THE MISSING SENSITIVITY IAN W ONG INFECTIOUS DISEASE AND MICROBIOLOGY REGISTRAR ROYAL HOBART HOSPITAL Case Presentation • 65F presents with headache associated with speech disturbance • Background • T2DM – Metformin • HTN - Perindopril • IUD inserted 20 years ago Case Presentation • Presented with a 3/52 history of headache associated with subjective fevers • Woke up in morning with expressive dysphasia, nausea and vomiting • No clinical sign of • Motor or sensory disturbance • Co-ordination deficits • Meningism MRI Brain Lumbar Puncture Brain Biopsy • No evidence of malignancy • No fungi or bacteria on staining • Histological features consistent with abscess with surrounding gliosis Brain Biopsy Case Presentation • Patient antibiotics subsequently rationalised to metronidazole and ceftriaxone • Resolution of neurological symptoms • Exploratory laparotomy + Diverting colostomy 29/8/14 • Non operative malignancy Case Summary • 65F with 2 cerebral abscess with B.fragilis and Fusobacterium • Secondary to endometrial carcinoma that fistulised to sigmoid colon • Clinically responded to anaerobic antimicrobial therapy Question • Viewpoints on the Brain biopsy comment? “Bacteroides and Fusobacterium are generally susceptible to metronidazole” • Should susceptibility studies be performed? Topics • Anaerobic antimicrobial sensitivity testing (AST) • Challenges of performing testing • Indications • Developments in Anaerobic resistance • Local Data from RHH Anaerobic Infections • Commensal organism of gastro-intestinal tract • Causes of significant infection • Abdomen • Pelvic • Soft Tissue • Brain • Current treatment empirical • Treatment uses broad spectrum Ab • Not target to susceptibility of organism obtain from clinical isolates Indications for Anaerobic AST • Sterile site infections (eg. brain, blood, joint fluid, prosthetic material) • Anaerobic organism which may harbour resistance – B.fragilis • Anaerobic organisms which have unpredictable resistance patterns – Bacteroides sp. Prevotella, Non perfringens Clostridium sp. , Bilophilia, Sutterella, Fusobacterium sp. Brook, I., Wexler, H., & Goldstein, E. (2013). Antianaerobic Antimicrobials: Spectrum and Susceptibility Testing. Clinical Microbiology Reviews, 526-546. Indications for Anaerobic AST • Treatment failure • If long term therapy required for anaerobic infection • When drug selection is critical in the management of patient Brook, I., Wexler, H., & Goldstein, E. (2013). Antianaerobic Antimicrobials: Spectrum and Susceptibility Testing. Clinical Microbiology Reviews, 526-546. Anaerobic Antimicrobial Susceptibility Testing (AST) • Despite clear indications anaerobic antimicrobial susceptibility testing not routinely performed in majority of labs • National Survey of USA hospital • 21 % of Hospital lab perform in house anaerobic antimicrobial susceptibility • Reducing rates of AST over time Goldstein, E., Citron, D., Goldman, P., & Goldman, R. (n.d.). National hospital survey of anaerobic culture and susceptibility methods: III. Anaerobe, 68-72. Challenges with Anaerobic AST • Absence of automated identification method for anaerobes prior to MALDI – TOF • Disc diffusion method previously unavailable for anaerobes • Different breakpoints between EUCAST and CLSI Nagy, E., Justesen, U., Eitel, Z., & Urbán, E. (n.d.). Development of EUCAST disk diffusion method for susceptibility testing of the Bacteroides fragilis group isolates. Anaerobe, 65-71. EUCAST vs CLSI Breakpoints Pen Piptaz FOX Clinda Mtz EUCAST Susceptible ≤ 0.25 ≤ 8 NA ≤ 4 ≤ 4 Resistant > 0.5 > 16 NA > 4 > 4 CLSI Susceptible ≤ 0.5 ≤ 32 ≤ 16 ≤ 2 ≤ 8 Intermediate 1 64 32 4 16 Resistant ≥ 2 ≥ 128 ≥ 64 ≥ 8 ≥ 32 Challenges with Anaerobic AST • Technical difficulties • Anaerobic organism slow growing • Specific growth requirement • Anaerobic infection often polymicrobial • Requires separation and resulting in slow turn around times • ID multiple organisms which may not be pathologically relevant The Case for Anaerobic AST • In vitro testing of anaerobic resistance patterns alters clinical outcomes Summary of Results Variable Active Therapy Inactive Therapy p value (n =81) (n=11) 30 day Mortality 13/81 (16%) 5/11 (45%) 0.04 Clinical Failure 18/83 (22%) 9/11 (82%) 0.0002 Microbiology 5/20 (25%) 3/7 (43%) 0.056 Persistence The Case for Anaerobic AST • Changes in Anaerobic resistance patterns • General trend for increase resistance to Clindamycin, Fluroquinolones, Augmentin • Regional variation Patterns of Bacteroides Sp. Resistance in Europe 40. 30. Augmentin 20. Cefoxitin Clindamycin Moxifloxacin 10. 0. 1992 2003 2011 Patterns of Bacteroides sp. Resistance in Europe 100. 75. Pencillin 50. Piperacillin Tazobactam Imipenem 25. Metronidazole 0. 1992 2003 2011 Patterns of Bacteroides sp. Resistance in USA 50 40 30 Clindamycin Cefoxitin 20 Trovafloxacin 10 0 1981-89 1990-99 2000-07 Australian Anaerobic AST • Minimal local data to guide anaerobic antibiotic selection • Last study performed 22 years ago 30 31 Findings of Chen et al. • Bacteroides fragilis group higher rates of antimicrobial resistance • Indole positive B.fragilis sp demonstrated highest rates of resistance • Beta lactam (6% of isolates sensitive to penicillin) • Cephalosporin (52% of isolates sensitive cefoxitin) • Beta-lactamase inhibitor improved Bacteroides sp. susceptibility to beta-lactams (Range 88-100%) 32 Findings of Chen et al. • Rates of anaerobic organism resistance clindamycin and imipenem were low • Clindamycin lowest susceptible group was indole negative B.fragilis sp. 82% isolates susceptible • Imipenem lowest susceptible group was Fusobacterium 88% isolates susceptible • Metronidazole provides good anaerobic coverage except to P.acnes and non sporing Anerobic gram positive bacilli 33 Royal Hobart Hospital AST • 51 Anaerobic isolates from 2014 to 2015 • E test strips used to assess Anaerobic organism susceptibility to Penicillin, Augmentin, Piperacillin- tazobactam and Metronidazole • 1 McFarland standard suspension of the organism was inoculated onto modify brucella agar • Plates were incubated anaerobically at 35°C between 24-72hrs depending on growth • Beta lactamase performed using nitrocefin disc Results 12 10 8 6 4 2 0 Results • Anaerococcous sp., Atopobium rimae, Dichelobacter nodusus and Peptostreptococcous anaerobious organisms were susceptible to beta lactams, clindamycin and metronidazole • Fingolida magna susceptible penicillin, Augmentin, Piptaz, Metronidazole but one isolates was highly resistant to clindamycin • Similar picture seen with Peptoniphilus sp. Finegoldia magna and Peptoniphilus sp. Pen Aug Clinda MTZ TZP Finegoldia magna 0.032 0.064 256 0.064 0.016 Peptonphilus harei 0.125 0.064 >256 0.5 0.064 Results Pen Aug Clinda MTZ TZP Porphyromonas sp. >32 0.016 <0.016 <0.016 <0.016 Prevotella oralis >32 1 <0.016 0.032 0.064 Eggethella sp. 1 0.5 0.5 0.064 0.064 • Porphyromonas gingivalis and Prevotella oralis resistant to penicillin • Eggerthella sp. discrepancy between EUCAST and CLSI whether penicillin susceptible Clostridium sp. Pen Aug Clinda MTZ TZP Clostridium bifermentans 0.25 4 0.016 0.125 1 Clostridium bifermentans 0.25 1 0.032 0.125 2 Clostridium perfringens 0.032 <0.016 0.023 0.5 <0.016 Clostridium perfringens 0.064 0.016 0.064 0.5 0.016 Clostridium septicum 0.125 1 0.125 32 0.064 Clostridium tertium 1 0.5 1 1 16 • Clostridium sp. susceptible to beta-lactams, clindamycin and metronidazole • Clostridium tertium potentially resistance to beta-lactam • Clostridium septicum intermediate metronidazole resistance Bacteroides fragilis Nitrocefin Pen Aug Clinda MTZ TZP Positive >32 0.75 0.38 0.19 0.125 Positive >32 2 0.25 0.25 0.25 Positive >32 0.125 1 0.064 0.064 Positive 16 0.25 2 0.25 0.125 Positive >32 0.25 2 0.25 0.5 Positive >32 2 1 0.5 0.25 Positive >32 1 1 0.5 0.5 Positive >32 16 1 1 32 Positive >32 2 1 0.5 1 Positive >32 0.25 0.125 0.5 0.25 • Positive for Beta lactamase -> Penicillin Resistant • 1 Isolate Resistant Augmentin and potentially Piptaz • Susceptible to Augmentin,Clindamycin and Metrondaizole Bacteroides Sp. Susceptibility Pen Aug Clinda MTZ TZP Bacteroides distasonis >32 16 2 0.5 >256 Bacteroides distasonis >32 4 2 0.125 16 Bacteroides distasonis >32 2 0.125 0.5 8 Bacteroides thetaiotamicron >32 4 >256 0.25 16 Bacteroides thetaiotamicron >32 0.5 2 0.5 16 Bacteroides thetaiotamicron >32 2 <0.016 0.5 16 Bacteroides vulgatus 8 0.5 1 0.25 4 • All isolates penicillin resistant • 1 B.distasonis isolate resistant to beta lactam with Beta- lactamase inhibitor • 1 B.thetaiotamicron isolate resistant to clindamycin • Potentially higher rates of Piperacillin tazobactam resistance Conclusion • Greater focus should be on Anaerobic AST should be performed for following indications • Sterile site infection • Anaerobic organism known to have variable or highly resistant patterns • In patient who failure treatment or require long term therapy • When drug selection critical in management of the patient • Alternatively periodic laboratory surveillance should be considered Questions? References • Brook, I., Wexler, H., & Goldstein, E. (2013). Antianaerobic Antimicrobials: Spectrum and Susceptibility Testing. Clinical Microbiology Reviews, 526-546. • Chen, S., Gottlieb, T., Palmer, J., Morris, G., & Gilbert, G. (n.d.). Antimicrobial susceptibility of anaerobic bacteria in Australia. Journal of Antimicrobial Chemotherapy J Antimicrob Chemother, 811-820. • Goldstein, E., Citron, D., Goldman, P., & Goldman, R. (n.d.). National hospital survey of anaerobic culture and susceptibility methods: III. Anaerobe, 68-72. • Nagy, E.,