Clinical Therapeutics/Volume ], Number ], 2014

Antimicrobial Salvage Therapy for Persistent Staphylococcal Bacteremia Using Daptomycin Plus Ceftaroline

George Sakoulas, MD1; Pamela A. Moise, PharmD2; Anthony M. Casapao, PharmD3; Poochit Nonejuie, PhD1; Joshua Olson, BS1; Cheryl Y.M. Okumura, PhD1; Michael J. Rybak, PharmD3; Ravina Kullar, PharmD4,*; Abhay Dhand, MD5; Warren E. Rose, PharmD6; Debra A. Goff, PharmD7; Adam M. Bressler, MD8; Yuman Lee, PharmD9; Joseph Pogliano, PharmD1; Scott Johns, PharmD10; Glenn W. Kaatz, MD11; John R. Ebright, MD11; and Victor Nizet, MD1 1University of California San Diego School of Medicine, La Jolla, California; 2Cubist Pharmaceuticals, Lexington, Massachusetts; 3Eugene Applebaum College of Pharmacy and Health Sciences, School of Medicine, Wayne State University, Detroit, Michigan; 4Oregon State University/Oregon Health & Science University, Portland, Oregon; 5New York Medical College, Valhalla, New York; 6University of Wisconsin Madison School of Pharmacy, Madison, Wisconsin; 7The Ohio State University Wexner Medical Center, Columbus, Ohio; 8Dekalb Medical Center, Decatur, Georgia; 9Maimonides Medical Center, Brooklyn, New York; 10VA San Diego Healthcare System, San Diego, California; and 11John D. Dingell VA Medical Center, Wayne State University School of Medicine, Detroit, Michigan

ABSTRACT therapy. After daptomycin plus ceftaroline was started, Purpose: Guidelines recommend daptomycin com- the median time to bacteremia clearance was 2 days bination therapy as an option for methicillin-resistant (range, 1–6 days). In vitro studies showed ceftaroline Staphylococcus aureus (MRSA) bacteremia after van- synergy against MRSA and enhanced MRSA killing by comycin failure. Recent data suggest that combining cathelicidin LL-37 and neutrophils. Ceftaroline also daptomycin with a β-lactam may have unique benefits; induced daptomycin binding in MSSA and MRSA to a however, there are very limited clinical data regarding comparable degree as nafcillin. MRSA grown in sub- the use of ceftaroline with daptomycin. inhibitory concentrations of ceftaroline showed attenu- Methods: All 26 cases from the 10 medical centers ated virulence in a murine subcutaneous infection model. in which ceftaroline plus daptomycin was used for Implications: Ceftaroline plus daptomycin may be treatment of documented refractory staphylococcal an option to hasten clearance of refractory staph- bacteremia from March 2011 to November 2012 ylococcal bacteremia. Ceftaroline offers dual benefit were included. In vitro (synergy studies, binding via synergy with both daptomycin and sensitization to assays, cathelicidin LL-37 killing assays), and in vivo innate host defense peptide cathelicidin LL37, which (virulence assays using a murine subcutaneous infec- could attenuate virulence of the pathogen. (Clin Ther. tion model) studies examining the effects of ceftaroline 2014;]:]]]–]]]) & 2014 Elsevier HS Journals, Inc. All with daptomycin were also performed. rights reserved. Findings: Daptomycin plus ceftaroline was used in Key Words: ceftaroline, daptomycin, MRSA, 26 cases of staphylococcal bacteremia (20 MRSA, 2 MRSE bacteremia, MSSA, VISA. vancomycin-intermediate S aureus, 2 methicillin- susceptible S aureus [MSSA], 2 methicillin-resistant S epidermidis). Bacteremia persisted for a median of – 10 days (range, 3 23 days) on previous antimicrobial Accepted for publication May 23, 2014. http://dx.doi.org/10.1016/j.clinthera.2014.05.061 *Current affiliation: Cubist Pharmaceuticals, Lexington, Mas- 0149-2918/$ - see front matter sachusetts. & 2014 Elsevier HS Journals, Inc. All rights reserved.

] 2014 1 Clinical Therapeutics

INTRODUCTION binding induced by ceftaroline. Finally, we show that Bacteremia due to methicillin-resistant Staphylococcus antistaphylococcal activity of human cathelicidin aureus (MRSA) poses significant surgical and medical HDPs and neutrophils of the innate immune system challenges to clinicians and the health care system.1 are significantly increased by ceftaroline. The most difficult cases are those that persist despite appropriate antimicrobial therapy and without an MATERIALS AND METHODS easily identified and removable focus, or cases in Clinical Cases which an infected biomedical device is identified but All 26 cases from the 10 medical centers in which cannot be removed without extreme risks to the ceftaroline plus daptomycin was used for the treatment patient.2 We have previously shown S aureus cross- of documented refractory staphylococcal bacteremia resistance between cationic antimicrobial host defense from March 2011 to November 2012 were included peptides (HDPs) of the human innate immune system (Figures 1 and 2). Additional case details are outlined in and vancomycin and daptomycin,3,4 the only anti- Table I. Participating institutions included the biotics approved by the US Food and Drug Admin- following: Sharp Memorial Hospital, San Diego, istration for the treatment of MRSA bacteremia. California; Detroit Medical Center, Detroit, Michigan; These data portend a worrisome scenario in clinical Oregon Health & Science University Hospital, cases in which the pathogen resists eradication and Portland, Oregon; Westchester Medical Center, resistance to these agents could develop simultane- Valhalla, New York; University of Wisconsin ously under continuous selective pressures, not just by Hospital, Madison, Wisconsin; The Ohio State administered antibiotics but also by HDPs. Thus, the University Wexner Medical Center, Columbus, Ohio; sense of clinical urgency in eradicating these infections Dekalb Medical Center, Decatur, Georgia; Maimonides is just becoming realized. Medical Center, Brooklyn, New York; VA San Diego We have previously described very successful outcomes Healthcare System, San Diego, California; and John D. in patients with refractory MRSA bacteremia using Dingell VA Medical Center, Detroit, Michigan. combination therapy with daptomycin and an antistaphy- Approval or waiver from each center’s institutional lococcal β-lactam.5 In addition, development of dapto- review board was obtained where appropriate based on mycin resistance by MRSA in vitro was suppressed in the the number of cases per site. presence of antistaphylococcal β-lactams.6 Ceftaroline was approved by the US Food and Bacterial Isolates Drug Administration in 2010, and it became the first One MRSA isolate (SA1, case 23, isolate 2, dapto- β-lactam available in the United States in 2011 with mycin MIC 1.0–2.0 mg/L; ceftaroline MIC 1 mg/L; in vitro and in vivo MRSA activity for the treatment nafcillin MIC 8 mg/L) and 1 methicillin-susceptible of bacterial skin and skin structure infections.7 We S aureus (MSSA) isolate (LUC77, case 22, daptomycin anticipated that the combination of daptomycin plus MIC 1.0 mg/L; ceftaroline MIC 0.25 mg/L; nafcillin ceftaroline therapy might exhibit superior activity MIC 0.5 mg/L) available from the case series were against MRSA given the following: (1) the demon- chosen for further in vitro analyses. SA1 was deter- strated synergy between daptomycin and β-lactams5; mined to have a daptomycin MIC of 1 mg/L by using (2) the intrinsic activity of ceftaroline against MRSA7; broth microdilution testing but an MIC of 2 mg/L by (3) the observed decrease in S aureus ceftaroline MIC Epsilometer test (Etest, BioMerieux, Durham, NC). In in S aureus upon loss of daptomycin susceptibility8; vivo mouse studies described in the following text and (4) a recent case in which daptomycin plus were performed on previously published strain MRSA ceftaroline was used successfully in salvage therapy Sanger 252 in which this infection model was well with supporting in vitro data.9 established in our laboratory.10 In the present article, we report the use of dapto- mycin and ceftaroline as a salvage antimicrobial In Vitro Assays regimen in the treatment of refractory staphylococcal Kill curves were performed in Mueller-Hinton bacteremia at 10 US medical centers. In vitro synergy broth supplemented with 50 mg/L Ca2þ by using a of ceftaroline plus daptomycin against MRSA is starting inoculum of 107 CFU/mL. Samples were demonstrated and correlated to enhanced daptomycin obtained at 0, 4, 24, and (in some cases) 48 hours,

2 Volume ] Number ] G. Sakoulas et al.

DAP 10 DAP 10 + CPT 600 q12 Case#1: L-sided IE VAN failure failure Clear 5d

Case#2: L-sided IE with DAP 8 + CPT 600 q24 VAN failure verterbral osteomyelitis Clear 2d

Case#3: L-sided IE with VAN + LIN DAP 8 + LIN DAP 8 + CPT 600 q8 VAN failure septic lung emboli failure failure Clear 5d

Case#4: IE with osteomyelitis DAP 6 DAP 10 DAP 10 + CPT 400 q8 VAN failure and discitis failure failure Clear 2d

DAP 10 DAP 10 + CPT 600 q12 Case#5: L-sided IE VAN failure MRSA failure Clear 1d bacteremia with DAP 10 DAP 10 + CPT 600 q12 Case#6: L-sided IE and ICD endocarditis failure Clear 2d

Case#7: L-sided IE with DAP 10 DAP 10 + CPT 600 q8 VAN failure splenic emboli failure Clear 4d

Case#7: L-sided IE, with DAP6 + CPT 200 q12 VAN failure endopthalmitis Clear 2d

Case#9: L-sided IE, with hematogenous VAN + CLIN VAN + CLIN + RIF DAP6 + CPT 600 q12 osteomyelitis/sternoclavicular failure failure Clear 6d septic arthritis

Case#10: DAP 9 DAP9 + CPT 600 q12 + RIF VAN failure L-sided IE and ICD failure Clear 1d

Case#11: VAN + CLIN DAP8 + CLIN DAP10 + CPT 600 q8 Epidural abcess failure failure Clear 1d

Case#12: DAP10 + CPT 600 q8 VAN failure Sacroiliac bone/joint Clear 1d

Case#13: DAP 6 DAP 6 + CPT 600 q12 Epidural abcess and VAN failure failure Clear 4d septic brain emboli

Case#14: DAP 10 DAP 10 + CPT 600 q12 VAN failure Unknown source failure Clear 1d

Case#15: DAP 4 DAP 4 + CPT 600 q12 MRSA Verterbral osteomyelitis failure Clear 2d bacteremia Case#16: DAP 10 DAP 10 + GEN DAP 10 + CPT 400 q24 without AV graft and Septic VAN failure failure failure Clear 6d endocarditis Thrombophlebitis Case#17: DAP 10 + CPT 200 q12 VAN failure Vertebral osteomyelitis Clear 1d Case#18: VAN + GEN DAP 6 DAP 6 + CPT 400 q12 osteomyelitis and chronic failure failure Clear 3d foot wounds Case#19: Tunneled venous catheter DAP 6 DAP 6 + CPT 600 q12 with multiple soft tissue failure Clear 2d infection foci

Case#20: DAP 6 DAP 6 + CPT 600 q12 VAN failure Prepatellar bursitis failure Clear 5d

Figure 1. Summary of cases in which daptomycin (DAP) þ ceftaroline (CPT) was used to clear persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia, stratified according to the presence (top strata) or the absence (bottom strata) of endocarditis. Additional details can be found in the Table 1. L ¼ left; IE ¼ infective endocarditis; VAN ¼ vancomycin; LIN ¼ linezolid; ICD ¼ infected cardiac device; RIF ¼ rifampin; CLIN ¼ clindamycin; GEN ¼ gentamicin; AV ¼ arteriovenous.

] 2014 3 Clinical Therapeutics

MSSA Case #21: DAP 8 + bacteremia LVAD- VAN + PIP/TAZ AMP/SUL DAP 8 + CPT 600 q12 AMP/SUL with associated failure failure clear 2d failure endicarditis R-sided IE

Case #22: Complex MSSA bacteremia VAN + CTX + bacteremia NAF + GEN DAP 8 + NAF DAP 8 + CPT 600 q12 with bone & TMP/SMX + without failure failure clear 1d joint, soft RIF failure endicarditis tissue & meningitis

VISA Case #23: DAP 10 + CPT 400 q12 (and MRSA) R-sided IE; VAN clear* (no qd cultures to documented date) bacteremia not a surgical failure further supression with PO DOX with candidate (relapsed after DOX discontinued) endicarditis

VISA Case #24: DAP 10 + CPT 200 q12 bacteremia Epidural abcess VAN LIN + GEN clear (no qd cultures to without with failure failure document date) endocarditis osteomyelitis

Case #25: R-sided IE DAP 10 + CPT 200 q12 VAN + GEN LIN prosthetic valve cleared (further failure thrombocytopenia MRSE not a surgical supression with PO DOX) bacteremia candidate with endocarditis Case #26: VAN VAN + GEN + RIF DAP 6 + CPT 400 Q12 R-sided IE failure failure clear 4d prosthetic valve

Figure 2. Summary of cases in which daptomycin (DAP) þ ceftaroline (CPT) was used to clear either (A) methicillin-susceptible Staphylococcus aureus (MSSA), (B) vancomycin-intermediate-susceptible Saureus (VISA), or (C) methicillin-resistant S epidermidis (MRSE). Additional details can be found in the Table 1. Case 23: VISA infective endocarditis (IE) case relapsed with bacteremia and endophthalmitis after doxycycline (DOX) was discontinued; relapse was re-treated with DAP þ CPT. LVAD ¼ left ventricular assist device; L ¼ left; VAN ¼ vancomycin; PIP/TAZ ¼ piperacillin/tazobactam; AMP/SUL ¼ ampicillin/ sulbactam; CTX ¼ ceftriaxone; TMP/SMX ¼ trimethoprim/sulfamethoxazole; RIF ¼ rifampin; NAF ¼ nafcillin; GEN ¼ gentamicin; R ¼ right; PO ¼ oral; LIN ¼ linezolid.

serially diluted 1:10 to 1:107, and 10 mL plated in representative experiment is shown. Limit of detection duplicate on Todd Hewitt agar (THA) plates. Assays was 1000 CFU/mL (log10 ¼ 3). were performed in duplicate in each experiment, and Susceptibility testing to daptomycin in varying con- experiments were performed twice on separate days. centrations of ceftaroline or nafcillin was performed by

Colonies were enumerated after 24 hours and log10 using broth microdilution methods established by the CFU/mL calculated for graphical presentation. One Clinical and Laboratory Standards Institute.11

4 Volume ] Number ] ] 2014 Table I. Clinical details of cases included in this study.

Antimicrobial Therapies Age/Sex Pathogen Patient (MICs) Comorbidities Diagnostic Findings Site(s) of Infection 1st Line 2nd Line 3rd Line 4th Line Comments

MRSA cases 144M HIV/AIDS (CD4 Mitral valve IE L-sided IE VAN DAP 10 DAP 10 þ CPT None MRSA count 0 d 1-3 d4–9 600 Q12 (VAN 2, DAP 1, Viral load d10–43 CPT 0.5) 41 million), Afib Clear 5 d 275M ESRD on HD, HTN, DM AV 3 5mm IE (side unspecified) VAN DAP 8 þ DAP 10 þ DAP 10 þ LIN Changed to DAP monotherapy for 6 MRSA vegetation with discitis, d1 CPT 600 q24 CPT 600 q24 d 5-9 weeks once stabilized (VAN 2, DAP osteomyelitis d2–3 d4 o0.5, CPT 2) Clear 2 d 367M Asthma MRSA bacteremia; EBV pro- Aortic valve IE Pulmon- VAN VAN þ LIN DAP 8 þ LIN DAP 8 þ CPT Changed to DAP 8 þ VAN þ MERO þ MRSA liferative disorder; pulmon- ary septic emboli d1–5 d6–12 d13–18 600 q8 CIPRO, and then DAP 8 þ CPT 600 (VAN 1, DAP ary septic emboli; TTE AV d 19-35 q12þ MOXI 0.25) vegetation Clear 5 day DAP stopped d 43 due to suspected Splenic infarcts; sepsis pneumonitis (CT chest [ground glass infiltrates]) þ peripheral eosinophilia Discharged on VAN þ MOXI 469M HTN, CKD, Obesity, DM, Complicated by early MRSA Osteomyelitis and VAN DAP 6 DAP 10 DAP 10 þ CPT Patient provided comfort care and MRSA anemia of CKD, HTN, surgical site infection with discitis d1–2 d3–6 d7–9 400 q8 died (VAN 2, DAP stroke, T6-L4 spinal fu- osteomyelitis/ hardware with IE d 10-17 0.25) sion 1 month previous MRSA bacteremia Clear 2 day

551M CHF, DM, HTN, CKD, Afib Echodensity along RV wire Left-sided IE VAN DAP 10 DAP 10 þ None Pacer removed d 4; sent home on d 18 MRSA d1–3 d3–10 CPT 600 q12 of DAP þ CPT d10–52 Clear 1 d 673M Prostate cancer, HTN, DM, 2.4-cm mass RV and L-sided IE and ICD DAP 10 DAP 10 þ DAP 10 None Pacemaker removed d 13 MRSA Afib, CHF RA leads (pacemaker) d1–7 CPT 600 q12 d29–51 d7–28 Clear 2 d 755M Hepatitis C, IVDU, COPD, MV 0.7 X 1.3 cm vegetation L-sided IE (MV) with VAN DAP 10 DAP 10 þ Patient had MV replacement with MRSA stroke splenic emboli d1–7 d8–11 CPT 600 q8 prosthetic valve on d 29. Tissue None (VAN 1.5, d12–72 valve culture was negative DAP 3) Clear 4 day 843F ESRD on HD Endophthalmitis Presumed VAN DAP 6 q48, DAP 6 q48 None Suspected initial source: HD catheter MRSA DM L-sided IE d1–3 CPT 200 q12 d15–28 d4–14 Clear 2 d 947M DM, HTN, Complicated soft tissue L-sided IE (MV) with VAN þ CLIN VAN þ CLIN DAP 6 þ None MRSA ETOH abuse infection hematogenous d1–3 þ RIF d 4–10 CPT 600 q12 .Skua tal. et Sakoulas G. Sternoclavicular septic bone/joint d10–37 arthritis Clear 6 d 10 86 M Afib, Dementia, TEE negative, culture of pace- Presumed VAN DAP 9 DAP 9þ CPT 600 LIN Pacemaker removed d 13; cleared MRSA HTN, GERD, venous stasis, maker wires (þ) MRSA VAN L-sided IE; infected d1–3 d4–19 q12þ RIF d 41-48 bacteremia d 20 (7 d after pace- (VAN 2, DAP glaucoma, blind MIC 2 pacemaker d20–41 DOX maker removal and 1 d after DAP 1, CPT 1) Clear 1 day d 48-57 þ CPT); discharged on DOX PO

(continued) 5 6 Therapeutics Clinical

Table I. (continued).

Antimicrobial Therapies Age/Sex Pathogen Patient (MICs) Comorbidities Diagnostic Findings Site(s) of Infection 1st Line 2nd Line 3rd Line 4th Line Comments

11 55 M DM, HTN MRI epidural abscess Epidural abscess VAN þ CLIN DAP 8 þ CLIN DAP 10 þ CPT Abscess drainage d 2 MRSA 50 cm 20 cm 3cm d1–3 d4–8 600 q8 DAP 10 þ (VAN 1, DAP d9–12 TMP-SMX o0.5) Clear 1 d d 13-50 12 27 M HIV with disseminated MRI of sacroiliac joint abscess Septic sacroiliac joint VAN DAP 10 þ None None MRSA MAC, asthma 2.4 2 cm periarticular with adjacent d1–9 CPT 600 q8 (VAN 2, DAP fluid; TTE negative abscess d10–29 1, CPT 1) Clear 1 d 13 29 F IVDU; anemia Spinal MRI: T12-L3 epidural Bilateral psoas abscess VAN DAP 6 DAP 6 þ VAN VAN 6 wk was started at discharge MRSA and paraspinal abscesses; and epidural abscess d1 d2–3 CPT 600 q12 d 20-62 Septic emboli to brain with with septic brain d4–19 resulting cranial nerve III, IV, emboli Clear 4 d and VI palsies; left pleural empyema 14 76 M CAD, DM, HTN, TEE negative Unknown source VAN DAP 10 DAP 10 þ DAP 10 MRSA ESRD on HD MRI/CT negative d1 d2–7 CPT 600 q12 d 18-56 (VAN 2, COPD, morbid obesity d7–17 DAP r0.5) Clear 1 d 15 63 M DM, morbid obesity CT: Psoas and iliopsoas Vertebral osteomyelitis DAP 4 DAP 4þ LIN CPT 600 q12 DAP 4 based on actual body weight, MRSA Ventral hernia with colon abscesses, vertebral d1–2 CPT 600 q12 d6–10 d 11-42 DAP 6 based on ideal body weight (VAN 2, DAP 2) necrosis/ perforation; pre- osteomyelitis d3–5 vious PICC-associated TEE negative Clear 2 d MRSA bacteremia 16 66 F HIV, DM, HTN, ESRD on TEE negative, US of LUE: IV catheter; AV graft VAN DAP 10 DAP 10 þ GEN DAP 10 þ CPT Source of bacteremia unknown for 10 MRSA HD, CHF, asthma, HCV heterogeneous echogenic and septic d1–2 d3–5 1 mg/kg 400 q24 days; Removal of AV graft d 11; (VAN 1, DAP foci noted thrombophlebitis d6–7 d 8-22 cleared 72 h after graft removal. r0.5, CPT 0.5) Clear 6 d De-escalated to DAP 10 as out- patient treatment for 6 wk with HD

17 60 M IVDU admitted for TEE negative; CT scan small Small abscesses in the VAN DAP 10 þ DAP 10 None Patient had AKI and septic shock; MRSA NSTEMI, AKI, and thigh abscess; MRI of spine right thigh; Osteo- d1–7 CPT 200 q12 d15–53 started HD on day 8 of admission; (VAN 2, DAP 1) septic shock, HD lumbar osteomyelitis without myelitis of C2–C6 d8–14 De-escalated to DAP 10 epidural abscess Clear 1 d

18 63 M ESRD on HD, Chronic wounds on feet with HD catheter VAN þ GEN DAP 6 5d DAP 6 þ CPT None Recent 6 wk previous course of VAN MRSA DM osteomyelitis 5d1–5 d6–10 400 q 12 d11–26 Clear 3 d 19 63 F T-cell lymphoma Multiple skin infection foci Venous access tunneled DAP 6 DAP 6 þ VAN LIN Volume MRSA venous catheter d1–5 CPT 600 q12 d16–22 d 23-28 d6–15 Clear 2 d 20 49 M DM, HTN, BPH No other foci Prepatellar bursitis VAN DAP 6 DAP 6 þ CPT 600 q12

] MRSA d1–8 d9–13 CPT 600 q12 d22–42

Number d14–21 Clear 5 d

(continued) ] ] 2014

Table I. (continued).

Antimicrobial Therapies Age/Sex Pathogen Patient (MICs) Comorbidities Diagnostic Findings Site(s) of Infection 1st Line 2nd Line 3rd Line 4th Line Comments

MSSA cases 21 50 M Nonischemic TEE negative LVAD infection VAN þ PIP/ AMP/SUL DAP 8 þ AMP/SUL DAP 8þ CPT Patient signed out AMA on d 12 of MSSA cardiomyopathy CT abdomen: No abscess Wound culture: TAZ d3–5 d5–6 600 q12 therapy; given a prescription for PO LVAD 3 y previously MSSA/ d1–3 d 6-12 cephalexin þ RIF; Escherichia coli Clear 2 day Returned with E coli bacteremia twice Blood culture: (1 mo and 3 mo later); MSSA only died 4 mo later (MSSA bacteremia had never returned) 22 54 M DM, hepatitis C, ETOH TEE-negative Retroperitoneal VAN/CTX/ NAF þ GEN DAP 8 þ NAF DAP 8þ CPT Treated purely with medical therapy MSSA abuse CT/MRI: Retroperitoneal infection TMP-SMX/RIF d3–6 d6–10 600 q12 DAP 8 þ NAF d 17–24 Phlegmon, L3–L5 Discitis/ d 1-3 d 10-17 NAF d 24–56 osteomyelitis/epidural ab- Clear 1 d Complete cure 6-mo follow-up scess. Psoas pyomyositis CSF: 2186/mm3 WBC (89% PMN), Glucose 31 mg/dL, protein 240 mg/dL VISA cases 23 60 F DM, HTN, s/pCABG TEE: atrial appendage 33- RA appendage VAN DAP 10 þ PO DOX Retreatment for Discharge on suppression on DOX VISA/MRSA Prior MRSA mm thrombus septic thrombus d1–30 CPT 400 q12 (noncompliant) relapse re-admitted with bacteremia and en- (isolate 1: sternal wound NM scan: no increased Poor surgical 42 days dophthalmitis after stopped VAN 4, DAP 3, Infection 2 focal uptake candidate taking DOX CPT 0.75) CT/MRI spine chest/abdo- retreated with DAP þ CPT and (isolate 2: men/pelvis: no osteomyeli- discharged on DOX VAN 2, DAP 1-2 tis, no abscess [see text], CPT 0.75) 24 71 F ESRD on HD TEE negative Epidural abscess VAN LIN þ GEN DAP 10 þ DOX DOX 3 months; no sign of VISA s/p laminectomy US AV graft: no fluid Osteomyelitis CPT 200 q12 90 days recurrence (VAN 3-4; DAP 2, collection 42 days LIN caused thrombocytopenia CPT 0.38) CT spine: lumbar osteomye- RIF resistance emerged litis, Discitis Epidural abscess MRSE cases 25 83 F ESRD on HD, TEE negative, mild MV VAN þ GEN LIN DAP 10þ DOX Suppression LIN caused thrombocytopenia MRSE CABG, AVR thickening d1–9 d10–16 CPT 200 q12 therapy RIF resistant Probable IE (VAN 4, DAP 0.5, Cirrhosis US AV graft: no fluid d17–42 d TMP-SMX severe allergy CPT 0.25) Prior MRSE bacteremia collection 2 prior breakthrough bacteremia on

3 times in past NM scan: no increased DOX and on wk 6 DAP al. et Sakoulas G. focal uptake Poor surgical candidate CT/MRI spine Chest/Abdo- men/Pelvis: no osteomyeli- tis, no abscess

(continued) 7 Clinical Therapeutics

Human cathelicidin LL-37 susceptibility testing ¼ ¼ ¼ ¼ and killing assays were performed in RPMI media atrial

DOX supplemented with 5% Luria broth (LB) as previously ¼ Epstein- 5,12 aortic valve b ¼ described. fi piperacillin/ ¼ ;A

¼ Daptomycin binding assays were performed, as EBV Comments previously described, after bacteria were grown to ux disease; ceftriaxone; VISA ;AVR fl OD of 0.6, exposed for 1 hour with ceftaroline 1 intravenous drug use;

¼ 600nm PIP/TAZ linezolid; ¼ mg/L or nafcillin 10 mg/L, and then labeled with 4 mg/L

¼ bodipy–daptomycin (Cubist Pharmaceuticals, Lexing- 5,12 IVDU S epidermidis

computed tomography; CKD ton, Massachusetts) for 15 minutes. The antimicro- ; infective endocarditis coronary artery disease; PICC

¼ –

¼ bial activity of bodipy daptomycin is slightly reduced ¼ such that the MIC is 1 dilution higher than unlabeled gastroesophageal re None Suspected source: HD catheter ¼ daptomycin. Cytochrome c binding was performed as ampicillin/sulbactam; ST-segment elevation myocardial infarction; 13 – ¼ arteriovenous; LIN previously described. Ceftaroline was provided by oxacin; CT fl ¼ non Forest Pharmaceuticals (New York, New York). þ ceftaroline; IE SUL 46 polymorphonuclear cell; CTX ¼ – / methicillin-resistant moxi ¼ ¼ DAP 6 CPT 400 q12 d15 Clear 4 d ¼ ¼ infected cardiac device

AMP Neutrophil Killing Assays ¼ rifampin; GERD Neutrophils were freshly isolated from the blood of RIF ¼ þ healthy donors by using the PolyMorphPrep kit (Frese- ;MOXI Antimicrobial Therapies GEN 14

– nius Kabi, Homburg, Germany), and erythrocytes were þ d4

oxacin 14 diabetes mellitus; AV fl lysed with sterile H2O as previously described. MRSA VAN daptomycin; CPT ¼ gentamicin; NSTEMI

alcohol; RIF Sanger 252 was grown to log phase in ceftaroline 0.1 cipro ¼ right atrial; ICD ¼ trimethoprim-sulfamethoxazole; CAD ¼ μ ¼

3 g/mL or media alone (untreated), washed, and – ¼ ¼ 1st Line 2nd Line 3rd Line 4th Line VAN d1 nuclear medicine; MRSE resuspended in phosphate-buffered saline (PBS). At this ¼ white blood cell count; PMN concentration of ceftaroline, there was no appreciable left ventricular assist device; ¼ effect on growth rate. Bacteria were inoculated at a ¼ ¼ 5 hypertension; DM

female; ETOH multiplicity of infection 1with5 10 polymor- vancomycin; DAP ¼ ultrasound; GEN ¼ þ 1

LVAD phonuclear cells in RPMI 2% 70 C heat-inactivated ¼ ¼ uid; WBC 15 valve fl meropenem; CIPRO fetal bovine serum in suspension culture plates. After Left-sided IE, prosthetic right ventricular; RA ¼ 90 minutes of incubation at 371C/5% CO2, cells were ¼ S aureus; clindamycin; TMP-SMX lysed with 0.025% Triton X-100, and the total number ¼ male; VAN

mitral valve; F of remaining bacteria were enumerated on THA plates. ¼ ¼

cerebrospinal Survival was calculated as the percentage of the initial hemodialysis; HTN M ¼

¼ inoculum. Experiments were performed by using blood hepatitis C virus; US endocarditis coronary artery bypass graft; NM AV, MV bioprosthetic valve from at least 3 healthy donors. Use and procedures ¼

¼ were approved by the University of California San Diego Human Research Protections Program. methicillin-susceptible CABG ¼

congestive heart failure; RV Animal Model of MRSA Cutaneous Infection Staphylococcus aureus; ¼ MRSA Sanger 252 has been used in our laboratory S aureus; ESRD on HD DM to study the effect of β-lactam antibiotics on MRSA

against medical advice; CSF virulence. The strain was grown overnight to the end-stage renal disease; HD magnetic resonance imaging; CLIN ¼ transes ophageal echocardiography; MERO

¼ stationary phase in 40 mL of antibiotic-free LB or ¼ ¼ LB containing ceftaroline 0.1 mg/L. Bacteria were (MICs) Comorbidities Diagnostic Findings Site(s) of Infection

MRI washed in PBS 40 mL, and resuspended in 2 mL of methicillin-resistant MRSE chronic obstructive pulmonary disease; MV Age/Sex Pathogen acute kidney injury; MSSA ¼ ¼ PBS and 2 mL of Cytodex beads (Sigma-Aldrich, St. 10 ¼ Louis, MO) (1 mg/L), yielding 10 CFU/mL. Next, brillation; ESRD replacement. vancomycin-intermediate tazobactam; AMA COPD doxycycline; Patient MRSA chronic kidney disease; CHF peripherally inserted central catheter; HCV AKI 26 60 M Barr virus; TEE fi 0.1 mL of the bacterial suspension was injected Table I. (continued). subcutaneously into flanks of 25-g female CD1 mice.

8 Volume ] Number ] G. Sakoulas et al.

To control for animal-to-animal variability, paired II). Twenty-five (96%) of the patients survived com- lesions were created, with ceftaroline-treated MRSA pletion of therapy; 1 patient died when medical care on one side and antibiotic-free grown MRSA on the was withdrawn due to multiple medical problems contralateral side using a total of 12 mice. Right and upon which the MRSA bacteremia was superimposed. left sides were alternated for antibiotic-free grown and The use of daptomycin plus ceftaroline combina- ceftaroline-grown MRSA. tion therapy was mostly for documented failure of Lesion sizes were measured at 2 days and compared bacteremia clearance. For 23 of the 26 cases for which by using a paired-sample Wilcoxon signed-rank test. detailed microbiologic information was available via A P value of o0.05 was considered significant. All serial daily blood culture results, bacteremia persisted animal studies were performed under protocols that for a median of 10 days (range, 3–23 days) on were reviewed and approved by the University of previous antimicrobial therapy, and the bacteremia California San Diego Institutional Animal Use and cleared in a median of 2 days (range, 1–6 days) after Care Committee. All animal research in this inves- daptomycin plus ceftaroline was started. It is critical tigation was performed in accordance with national to note that in all but 1 case (case 21; Table I), the and local guidelines that are in place to maximize bacteremia clearance on daptomycin plus ceftaroline humane animal treatment. therapy was not temporally related to a surgical procedure such as device removal. RESULTS Case Series Endocarditis Cases Characteristics of the Clinical Cases As anticipated from a case series examining salvage Daptomycin plus ceftaroline was used in 26 cases therapy for staphylococcal bacteremia, a large per- of staphylococcal bacteremia from 10 geographically centage of patients (14 of 26 [54%]) had bacterial and demographically distinct US hospitals. Clinical endocarditis. These cases warrant closer scrutiny details are provided in Table I, and a summary of because bacteremia persistence is a salient feature of relevant clinical characteristics are provided in Table II. their clinical and microbiologic course. These 14 The pathogens consisted of MRSA in 20 cases patients comprised 10 with MRSA, 1 with MSSA, 1 (Figure 1), MSSA in 2 cases, vancomycin-intermediate with VISA, and 2 with methicillin-resistant S epider- Saureus(VISA) in 2 cases, and methicillin-resistant midis endocarditis. Daptomycin plus ceftaroline was S epidermidis in 2 cases (Figure 2). As expected, used as second-line therapy for 4 patients, third-line endocarditis (confirmed echocardiographically) was therapy for 7, and fourth-line therapy for 2. Among highly represented (54% [14 of 26]), and included 12 the 10 patients with endocarditis who had serial blood patients with left-sided, 1 side unspecified, and 1 right- cultures collected, bacteremia cleared a median of 2 sided endocarditis. The mean patient age was 60 years, days (range, 1–6 days) after daptomycin plus ceftaro- and 73% were males. Nine (35%) of the patients had line therapy was started. end-stage renal disease and were on hemodialysis, and 15 (58%) patients had diabetes mellitus. Nonsusceptible Organisms Daptomycin Plus Ceftaroline Salvage Other salient features in these cases are the involve- The daptomycin plus ceftaroline combination was ment of nonsusceptible organisms to daptomycin in 4 used most often as third-line therapy in 13 cases cases and ceftaroline in 1 case. The ceftaroline- (50%), followed by second-line therapy in 8 cases resistant isolate was successfully cleared after 2 days (31%), and fourth-line therapy in 5 cases (19%). The with the combination therapy using daptomycin 8 mg/ median duration of daptomycin plus ceftaroline com- kg per day plus ceftaroline 600 mg every 24 hours. bination therapy was 16 days. Once deemed stable, The cases with daptomycin nonsusceptibility involved: some patients received additional de-escalated, step- (1) 2 cases with VISA (cases 23 and 24); (2) one case down antibiotics replacing daptomycin plus ceftaro- with 7 days of vancomycin therapy followed by line (eg, daptomycin monotherapy, oral doxycycline), daptomycin 10 mg/kg (case 7); and (3) 1 case treated to complete a median total duration of 42 days of with daptomycin 6 mg/kg based on ideal body weight therapy for staphylococcal bacteremia (Tables I and that was 4 mg/kg actual body weight (case 15).

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Table II. Summary of patient and infection Table II. (continued). characteristics. Values are given as Value median (range) or number (%). Characteristic (n ¼ 26) Value Duration of DAP þ CPT plus follow-up 42 (8–132) Characteristic (n ¼ 26) antibiotics, d 414 25 (96) Age, y 60 (27–86) 442 14 (54) Male 19 (73) Antimicrobial resistance Pathogen Daptomycin nonsusceptible 4 (15) MRSA 20 (77) MSSA 2 (8) VISA 2 (8) MRSA ¼ methicillin-resistant Staphylococcus aureus; MSSA MRSE 2 (8) ¼ methicillin-susceptible S aureus; VISA ¼ vancomycin- Common comorbidities intermediate S aureus; MRSE ¼ methicillin-resistant S Diabetes 15 (58) epidermidis;IE¼ infective endocarditis;AV¼ arteriovenous; Hemodialysis 9 (35) DAP ¼ daptomycin; CPT ¼ ceftaroline. HIV/AIDS 3 (12) *May have 41 site, so total 4 100%. Liver disease 5 (19) Malignancy 2 (8) Sites of infection* Endocarditis 14 (54) Left-sided IE 12 (46) Refractory MSSA Bacteremia Right-sided IE 1 (4) Of note, 2 of the 5 cases in which the combination Side not specified 1 (4) therapy was used as fourth-line therapy involved Left ventricular assist device 1 (4) Pacemaker/defibrillator 2 (8) persistent bacteremia due to MSSA that failed to Osteoarticular 11 (42) clear promptly with daptomycin in combination with Discitis/vertebral osteomyelitis/epidural abscess 8 (31) nafcillin or ampicillin/sulbactam. One case (case 22; Sternoclavicular septic arthritis 1 (4) Table I) involved a massive retroperitoneal phlegmon Sacroiliac joint 1 (4) localized between the vertebral spine posteriorly and Osteomyelitis and chronic foot wounds 1 (4) ’ Other deep tissue 3 (12) the descending aorta anteriorly. The patient s bac- Tunneled venous catheter with soft tissue 1 (4) teremia resolved, and he made a complete clinical, infection foci microbiologic, and radiographic recovery without any AV graft with septic thrombophlebitis 1 (4) surgical intervention. The MSSA from this patient Prepatellar bursitis 1 (4) (LUC77) was subjected to in vitro study (described Septic brain emboli/meningitis 2 (8) later). The second of the MSSA bacteremia cases Unknown bacteremia source 1 (4) Bacteremia duration before DAP þ CPT, d 10 (3–23) warrants mention because the patient had an infected Bacteremia duration after DAP þ CPT, d 2 (1–6) nonremovable left ventricular assist device, with DAP þ CPT salvage superficial cultures growing MSSA and Escherichia Second-line 8 (31) coli and persistent blood culture specimens growing Third-line 13 (50) MSSA (case 21). The patient ultimately cleared the Fourth-line 5 (19) Daptomycin dosing, mg/kg MSSA bacteremia after 8 days, including 48 hours on 4 1 (4) ceftaroline plus daptomycin. However, the patient had 6 7 (27) a history of medical noncompliance and abusive 48 18 (69) behavior toward medical staff, eliminating his CPT dosing chances for device exchange, and he signed himself q8 h 5 (19) out of the hospital against medical advice 4 days after q12 h 19 (73) q24 h 2 (8) bacteremia clearance (12 days of total parenteral Duration of DAP þ CPT, d 16 (3–61) antimicrobial therapy). He was prescribed cephalexin 47 23 (88) plus rifampin orally with unknown compliance. Re- 428 7 (28) markably, while the patient was readmitted 2 sub- E coli (continued) sequent times with bacteremia and concomitant

10 Volume ] Number ] G. Sakoulas et al. left ventricular assist device driveline infection, the Table III. Daptomycin (DAP) susceptibilities MSSA bacteremia never recurred for 4 months until of methicillin-resistant Staphylococcus the patient died. aureus (MRSA) SA1 and methicillin- susceptible S aureus (MSSA) LUC77 Antibiotic-related Adverse Effects in broth media containing varying Characteristic adverse effects related to specific concentrations of ceftaroline or antimicrobial agents requiring alternative therapy nafcillin. were observed among patients in this case series. These adverse effects included hepatotoxicity and LUC 77 interstitial nephritis from rifampin, thrombocytopenia (MSSA) SA1 (MRSA) from linezolid, eosinophilic pneumonitis from dapto- Antibiotic in Broth DAP MIC DAP MIC mycin, and hypersensitivity reactions from trimetho- Media (mg/L) (mg/L) prim/sulfamethoxazole. Ceftaroline, mg/L 012 In Vitro Synergy Testing 0.125 0.25 1 To determine in vitro synergy between daptomycin 0.25 0.5 and ceftaroline, checkerboard (Table III) and time-kill 0.50 0.125 studies were performed against MSSA LUC77 from 1.0 case 22 (Figure 3A) and MRSA SA1 from case 23 Nafcillin, mg/L (Figure 3B). Against MSSA LUC77, nafcillin 20 mg/L 012 and ceftaroline 5 mg/L alone achieved comparable 0.125 0.5 2 bactericidal killing at 24 hours. These concentrations 0.25 0.25 2 were chosen because they approximate the free Cmax 0.5 2 7,16,17 achieved in vivo with standard dosing regimens. 1.0 2 When co-incubated with a subinhibitory daptomycin 2.0 2 concentration of 0.5 mg/L, the ceftaroline combination 4.0 1 produced further killing than ceftaroline alone, but the 8.0 nafcillin combination allowed significant regrowth. Against MRSA, the combination of daptomycin 1 mg/L plus ceftaroline 0.1 mg/L demonstrated consid- erable and obvious synergy over each drug alone. and vancomycin-resistant Efaecium,12 respectively, by cationic antimicrobial peptides. MRSA SA1 and MSSA Daptomycin Binding LUC77 demonstrated MIC to LL-37 of 16 mM. In the Our previous studies have demonstrated β-lactam– presence of 0.1 mg/L of ceftaroline or nafcillin, the LL- induced binding of daptomycin to MRSA5 and 37 MIC was reduced to 8 mM for both isolates. vancomycin-resistant Enterococcus faecium.12 Figure 4 Figure 5A shows that against MRSA SA1, growth in microscopically and quantitatively demonstrates that subinhibitory concentrations of ceftaroline results in a ceftaroline also induces daptomycin binding in MSSA concentration-dependent hypersensitization to killing and MRSA comparably to nafcillin. Under these con- by the human cathelicidin LL-37 (16 mM). We then ditions of ceftaroline exposure, there was no significant examined the effects of ceftaroline on killing of MRSA difference in cytochrome c binding for either MRSA SA1 Sanger 252 by using freshly isolated human neutro- or MSSA LUC77, suggesting that the mechanism of phils, which produce LL-37 abundantly. These assays enhanced daptomycin binding was not mediated by demonstrated a significant enhancement of neutrophil reduction in net surface charge (data not shown). killing of MRSA after the growth in ceftaroline 0.1 mg/ L compared with the same strain grown in antibiotic- Ceftaroline Effects on Innate Staphylocidal free LB broth (Figure 5B). Immunity MRSA Sanger 252 was cultured under the same We have demonstrated that antistaphylococcal conditions and subsequently injected subcutaneously β-lactams and ampicillin enhance killing of MRSA5 into CD1 mice. The exact inoculum was 2.95 109

] 2014 11 Clinical Therapeutics

focus. Although such refractory infections have been appreciated to pose increased risks of adverse individ- 10 Control ual patient outcomes such as mortality and increased NAF 20 8 MSSA health care resource utilization, recent emerging data CPT 5 1,2 DAP 0.5 suggest more global implications of such infections. CFU/mL 6 10 DAP 0.5 + NAF 20 It has long been appreciated that selection pressure on DAP 0.5 + CPT 5 Log 4 bacteria in a persistent high-inoculum focus of infec- tion (particularly by suboptimally dosed antibiotics) 0102030 can drive antibiotic resistance and therefore highlights Time (h) the importance of surgical source control of such infections.18,19 However, it is becoming increasingly 10 Control apparent that antimicrobial resistance in staphylococci 8 NAF 0.1 CPT 0.1 MRSA does not emerge in a closed system driven only by the DAP 2 antimicrobial agents themselves. We have shown that CFU/mL 6 DAP 2 + NAF 0.1 10 DAP 2 + CPT 0.1 important cationic HDPs of the human innate immune

Log 3 4 system can select for resistance to vancomycin and daptomycin4 that clinicians subsequently administer 0102030 Time (h) to patients for therapy. The longer these infections persist, HDPs plus administered antibiotics may co- Figure 3. Kill curves demonstrating the effect of select drug-resistant bacteria if the bacterial inoculum daptomycin (DAP), nafcillin (NAF), remains high. A more recent study has even shown the and ceftaroline (CPT) alone or in emergence of daptomycin resistance in vivo under combination at the specified concen- HDP selection pressure without the additional selec- trations (milligrams per liter) against tive pressure of antibiotic therapy.20 Although clear- Staphylococ- (A) methicillin-susceptible ing these infections in the fastest possible manner cus aureus (MSSA) LUC77 and (B) reduces the risk of antibiotic resistance, the data are methicillin-resistant S aureus (MRSA) limited identifying the best possible approaches to SA1. achieve this goal. – Based on previous data,21 25 we have examined and shown that the addition of antistaphylococcal β-lactams CFU for the control antibiotic-free grown MRSA and to daptomycin may prove to be helpful in bacteremia 9 5 β 2.90 10 CFU for the ceftaroline-grown MRSA in clearance. In addition, -lactams seem to reduce the 0.1 mL, confirming minimal growth differences of development of daptomycin (and therefore possibly Saureus.6 MRSA Sanger 252 under these conditions. If the HDP) resistance in Through research collabo- fi enhanced LL-37 and white blood cell activity rendered rative discussions of this phenomenon, we identi ed by exposure to ceftaroline was functionally significant centers where the novel cephalosporin ceftaroline was in vivo, then attenuation in lesion sizes would be used in combination with daptomycin. These centers expected. Indeed, this outcome was observed as contributed all their cases in which the daptomycin plus shown in Figure 5C, with MRSA Sanger 252 grown ceftaroline combination was used as treatment of in ceftaroline 0.1 mg/L before mouse challenge persistent staphylococcal bacteremia to this series. producing significantly smaller lesion sizes compared As in the previous case series, the combination of with the same strain cultured in antibiotic-free media daptomycin plus ceftaroline was highly successful, clear- and injected on the contralateral side. ing the bacteremia in a median of 2 days after persisting for a median of 10 days. Although there is no way of knowing how this time to bacteremia clearance would DISCUSSION compare with either agent alone (particularly with Refractory MRSA bacteremia is a very challenging ceftaroline monotherapy), 2 very recent studies suggest clinical situation, especially when source control is that the combination therapymayclearbacteremiamore not possible by virtue of an elusive or irremovable rapidly than monotherapy. One study showed a mean

12 Volume ] Number ] G. Sakoulas et al.

1.0

0.8 Control + CPT 1 0.6 + NAF 10

0.4

Relative Frequency 0.2

0.0 Control CPT 1 NAF 10 0 200 400 600 800 1000+ Bodipy-Daptomycin Intensity

1.0

0.8 Control 0.6 + CPT 1 + NAF 10 0.4

Relative Frequency 0.2

0.0 Control CPT 1 NAF 10 0 40 80 120 160 200+ Bodipy-Daptomycin Intensity

Figure 4. Effect of bodipy-labeled daptomycin (4 mg/mL) binding to methicillin-resistant Staphylococcus aureus isolate SA1 (top panel) or methicillin-susceptible S aureus isolate LUC77 (bottom panel) after exposure for 1 hour to either ceftaroline (CPT) 1 mg/L or nafcillin (NAF) 10 mg/L compared with no antibiotic. The accompanying histograms on the right quantitatively demonstrate that CPT and NAF result in higher intensity binding.

60 150 15 ) P < 0.02 3 40 100 P < 0.05 10 P = 0.03

20 % Survival 50 5 % Survival (2 h) Lesion size (mm 0 0 0 0 0.06 0.25 0.50 00.1 Untreated CPT CPT (g/mL) CPT (g/mL)

Figure 5. (A) Methicillin-resistant Staphylococcus aureus (MRSA) SA1 grown in antibiotic-free Luria broth (LB) or LB containing 0.06, 0.25, and 0.5 mg/L of ceftaroline (CPT), washed in phosphate-buffered saline, and subjected to LL37 16 mM. Percent survival at 2 hours in shown (Kruskal-Wallis ANOVA, P ¼ 0.02). (B) CPT-sensitized MRSA Sanger 252 is more susceptible to killing by neutrophils. MRSA Sanger 252 grown in 0.1 mg/L of CPT is more susceptible to polymorphonuclear cell killing than bacteria grown in media containing no antibiotic (Mann-Whitney U test, P o 0.05). (C) CPT- sensitized MRSA Sanger 252 produces smaller lesions when injected subcutaneously into CD1 mice compared with the same strain grown in antibiotic-free media (paired-sample Wilcoxon signed-rank test, P ¼ 0.03).

] 2014 13 Clinical Therapeutics bacteremia duration of 5 days when salvage ceftaroline to PBPs by ceftaroline must be 40.1 mg/L to produce monotherapy was used in staphylococcal bacteremia the necessary physiologic changes that will result in after glycopeptide failure.26 In another recent study daptomycin synergy, consistent with previous data on that examined outcomes of 31 patients with persistent binding affinity of ceftaroline for S aureus PBPs.29 MRSA bacteremia treated with ceftaroline, 0% failure (0 With respect to the enhancement of innate immune- of 10) was reported among the 10 patients who received mediated staphylocidal activity, however, growing ceftaroline combination therapy (5 with daptomycin), bacteria overnight in ceftaroline 0.1 mg/L was sufficient compared with 38% failure (8 of 21) among patients to show enhancement of cathelicidin LL-37 killing, who received ceftaroline monotherapy (Fisher exact text, enhancement of neutrophil killing, and reduced viru- P ¼ 0.0317).27 lence in skin lesion generation when injected into mice. Against a MRSA from 1 case in our study, in vitro We suspect that the reduced lesion sizes were due to the synergy was clearly demonstrated between daptomy- increased effectiveness of the host cathelicidin and cin and ceftaroline. When evaluating MSSA from neutrophil defenses in bacteria exposed to ceftaroline. another case, synergy was found between daptomycin This study provides encouraging data to clinicians and ceftaroline; however, the addition of subinhibi- treating serious infections due to staphylococci, par- tory concentrations of daptomycin to nafcillin proved ticularly cases of MRSA bacteremia refractory to less effective in killing than nafcillin alone. This standard forms of therapy due to unidentifiable or finding may potentially explain why nafcillin plus unremovable foci of infection. In addition, although daptomycin failed to clear the bacteremia as a third- the combination of daptomycin plus antistaphylococ- line regimen in MSSA bacteremia, yet the combination cal β-lactams has shown successful outcomes in a few of daptomycin and ceftaroline was subsequently suc- cases of refractory MRSA bacteremia and substanti- cessful as a fourth-line regimen. It also highlights the ated by recent additional in vitro studies, one clinical complex pharmacodynamic interactions of antibiotics case in this series of MSSA bacteremia and subsequent in vivo, with potential negative effects of combination in vitro studies in this report suggest that this antibiotic therapy against susceptible organisms. combination may be less potent than the antistaphy- Although daptomycin plus nafcillin has shown great lococcal agent alone for some MSSA strains, as seen promise in the treatment of MRSA bacteremia, this for strain LUC77 (case 22; Table I). However, combination needs to be examined further against ceftaroline plus daptomycin exhibited excellent MSSA. Based on previous work, we hypothesized that activity against this particular organism in vitro, and the differences between nafcillin and ceftaroline with this combination was ultimately successful in clearing respect to synergy with daptomycin rests on relative the bacteremia. The patient ultimately was de- binding to penicillin-binding protein 1 (PBP1).28 escalated to daptomycin plus nafcillin and then to Ceftaroline seems to bind PBP1, as well as all other cefazolin monotherapy to complete a prolonged pa- PBPs of S aureus with the exception of PBP4.29 renteral course of therapy, with an excellent clinical However, there is considerable heterogeneity in the outcome. Thus, it seems that once an infection is 50% inhibitory concentrations on PBP1 and other adequately controlled, and there are no outstanding PBPs between different S aureus strains, and these surgical management issues, it may not be necessary to relative differences need to be explored further, likely complete an entire parenteral course of antimicrobial through sequencing on PBP genes of different strains. therapy with daptomycin plus the β-lactam or ceftaro- Treatment of the strains with ceftaroline 1 mg/L line, as combination therapy can be very cumbersome resulted in an enhancement of daptomycin binding to and expensive outside an acute care hospital setting. MRSA SA1 and MSSA LUC-77 comparable to naf- However, we caution against early de-escalation in cillin 10 mg/L (Figure 4). Interestingly, we did not see patients with left-sided endocarditis for which a this effect when we reduced ceftaroline to 0.1 mg/L cardiac surgical indication remains despite bacteremia and grew the bacteria overnight. Thus, we “pulsed” clearance, and we suggest continuation of combina- the bacteria with ceftaroline 1 mg/L or nafcillin 10 tion therapy until the patient can be bridged to mg/L for 1 hour and searched for changes in surgery (G.S., unpublished data). daptomycin binding, with no appreciable effect on The present study is clearly limited in its retrospec- bacterial viability. This finding suggests that binding tive, noncomparative design. Furthermore, although

14 Volume ] Number ] G. Sakoulas et al. bacteremia cleared a median of 2 days after daptomycin Pharmacology of Pediatric Antimicrobial Therapy plus ceftaroline therapy, it is impossible to know how (Drs. Sakoulas and Nizet)]. Additional funding was long the bacteremia would have taken to clear had the provided by Forest Pharmaceuticals (New York, NY). previous therapies been continued without reliance on G. Sakoulas and P.A. Moise was responsible in daptomycin plus ceftaroline salvage. This question searching of the literature. G. Sakoulas, P.A. Moise could only have been answered in a prospective com- and V. Nizet was responsible in figure creation. G. parative study. In addition, follow-up of 43 months Sakoulas and V. Nizet was responsible in designing was available for only 2 of the 25 surviving patients, the study. G. Sakoulas, A.M. Casapao, P. Nonejuie, J. and the durability of this therapy is unknown. Olson, C.Y.M. Okumura, M.J. Rybak, R. Kullar, A. Nevertheless, there are promising data to suggest a Dhand, W.E. Rose, D.A. Goff, A.M. Bressler, Y. Lee, clinical utility of daptomycin plus ceftaroline in the acute J. Pogliano, S. Johns, G.W. Kaatz and J.R. Ebright period to quench refractory bacteremia and potentially was responsible in data collection. G. Sakoulas, P.A. widen the time window to obtain prompt source control Moise and V. Nizet was responsible in data interpre- andreduceHDP-drivenresistancetodaptomycinand tation. And all the authors were responsible for vancomycin. The medical centers that contributed cases writing of this paper. to this series included all cases in which daptomycin plus ceftaroline was used, not just cases with successful CONFLICTS OF INTEREST outcome. This understanding, along with our compan- Dr. Sakoulas has received research grant support from ion in vitro studies, suggests that the combination of Cubist Pharmaceuticals and speaking honoraria from daptomycin and ceftaroline warrants further investiga- Cubist, Pfizer, Forest, Novartis, and Astellas Pharma- tion. In more global terms, this study, as well as – ceuticals. Dr. Moise is an employee and shareholder of numerous previously in vitro,21 24,28 animal models,25 Cubist. Dr. Casapao has received grant support from and human data,5,26,27 suggest that daptomycin plus β- Cubist, Forest, and the Michigan Department of lactam therapy may be an appropriate candidate for Community Health. Dr. Rybak has received grant formal large-scale clinical trials. Although direct com- support from, consulted for, or provided lectures for parisons of the current MRSA bacteremia treatment Cubist, Forest, Durata, Cepheid, and Novartis. Dr. standards daptomycin and vancomycin monotherapy Kullar is an employee and shareholder of Cubist; this versus these agents with nafcillin added are probably the research was conducted during her prior employment most anticipated among infectious disease clinicians, at Oregon State University. At that time, Dr. Kullar exploration of ceftaroline in combination with these received speaking honoraria from Cubist and Forest, agents is also warranted, probably as a follow-up study. and served on the advisory board of Optimer. Dr. We believe that combination therapy using β-lactams is Dhand has received speaker’s honoraria from Cubist poised to represent the new treatment paradigm for and Pfizer. Dr. Rose has received grant support and MRSA bacteremia in the future. speaking honoraria from Cubist and is a consultant for The Medicines Company and Visante, Inc. Dr. CONCLUSIONS Goff has received grant support from Merck and Ceftaroline plus daptomycin may be an option to serves on the advisory board of Optimer, Cubist, hasten clearance of refractory staphylococcal bacter- Merck, Rempex, and Forest. Dr. Pogliano has re- emia. Ceftaroline offers a dual benefit via synergy with ceived research grants and consulting fees from Cub- both daptomycin and sensitization to innate host ist. Dr. Nizet was formerly on the advisory board of defense peptide cathelicidin LL37, which could attenu- Trius Therapeutics (acquired by Cubist). The authors ate virulence of the pathogen. have indicated that they have no other conflicts of interest regarding the content of this article. ACKNOWLEDGMENTS This work was supported by a grant from the Na- tional Institute of Health, Division of National In- REFERENCES stitute of Child Health and Human Development 1. Naber CK. Staphylococcus aureus bacteremia: epidemiol- (grant U54 HD071600-01 [September 26, 2011– ogy, pathophysiology, and management strategies. Clin June 30, 2016] Developmental and Translational Infect Dis. 2009;48:231–237.

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daptomycin-nonsusceptible strains of methicillin-resistant Staphylo- coccus aureus with evolving oxa- cillin susceptibility (the “seesaw effect”). Antimicrob Agents Chemo- ther. 2010;54:3161–3169. 26. Paladino JA, Shields RK, Taylor JE, Schentag JJ. Abstr Intersci Conf Antimicrob. Agents Chemother. 2013; abstract K-709. Available at: http://www.icaaconline.com/ php/icaac2013abstracts/start.htm. 27. Polenakovic HM, Pleiman CM. Cef- taroline for methicillin-resistant Staphylococcus aureus bacteremia: case series and review of the liter- ature. Int J Antimicrob Agents.2013; 42:450–455. 28. Berti A, Sakoulas G, Nizet V, et al. β-lactam antibiotics targeting PBP1 selectively enhance dapto- mycin activity against methicillin- resistant Staphylococcus aureus. Antimicrob Agents Chemother.2013; 57:5005–5012. 29. Kosowska-Shick K, McGhee PL, Appelbaum PC. Affinity of ceftaro- line and other beta-lactams for penicillin-binding proteins from Staphylococcus aureus and Strep- tococcus pneumoniae. Antimicrob Agents Chemother. 2010;54:1670– 1677.

Address correspondence to: George Sakoulas, MD, University of Cal- ifornia San Diego School of Medicine, Center for Immunity, Infection & Inflammation, Biomedical Research Facility II, Room 4114, 9500 Gilman Drive, Mail Code 0760, La Jolla, CA 92093-0760. E-mail: gsakoulas@ ucsd.edu

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