Acta Orthop. Belg., 2007, 73, 263-267 CASE REPORT Late prosthetic joint infection due to Rothia mucilaginosa Frederick MICHELS, Johan COLAERT, Filip GHEYSEN, Thierry SCHEERLINCK From the AZ Groeninge Hospital, Kortrijk, Belgium We report a chronic hip arthroplasty infection with habitat of R. mucilaginosa is the oral cavity and Rothia mucilaginosa, a Gram-positive germ belong- upper respiratory tract. To our knowledge, this is ing to the normal flora of the human oral cavity. the first reported case of prosthetic infection with Successful treatment was achieved by a two-stage hip this unusual germ. arthroplasty revision and intravenous administra- tion of vancomycin. This case report illustrates the CASE PRESENTATION potential virulence of R. mucilaginosa in patients with a joint prosthesis. We propose to routinely perform specific staining Our patient is a 59-year-old man who underwent and prolonged culturing techniques for unusual a bilateral total hip arthroplasty for osteoarthritis, germs such as Rothia mucilaginosa when the clinical in May 1992 (right side) and December 1992 (left history, physical examination or intra-operative find- side). Both interventions were successful and the ings suggest an implant infection. patient had an uneventful recovery and a satisfacto- This paper reviews current antibiotic prophylaxis ry result. His medical history revealed diabetes guidelines for infection prevention of joint arthro- type II and arterial hypertension. In March 1994 a plasties during dental procedures. dental extraction was performed, covered by antibi- Keywords : hip arthroplasty ; infection ; Rothia otic prophylaxis (penicillin 2 g orally 1 hour before mucilaginosa. and 1 g 6 hours after the procedure). Three months after that procedure the patient started to complain about right groin and mid-thigh pain. In September INTRODUCTION ■ Frederick Michels, MD, Orthopaedic Resident. The infection rate of total hip arthroplasties is ■ Johan Colaert, MD, Clinical microbiologist. Department approximately 1% (5). Most commonly such infec- of Laboratory Medicine and Bacteriology. tions are caused by gram-positive cocci, especially ■ Filip Gheysen, MD, Chairman of the Department of coagulase-negative staphylococci (CNS) and Orthopaedic Surgery. Staphylococcus aureus (5). Rothia mucilaginosa AZ Groeninge Hospital, Kortrijk, Belgium. ■ shares the coccal morphology and positive catalase Thierry Scheerlinck, MD, Chief of Clinic. Department of Orthopaedic Surgery, Academic Hospital of activity with staphylococci, and is commonly con- the Vrije Universiteit Brussel (AZ VUB), Brussels, Belgium. sidered as a CNS. However, R. mucilaginosa can Correspondence : Frederick Michels, OLV van Lourdeslaan easily be distinguished from staphylococci and 78, 1090 Brussels, Belgium. micrococci by a weak catalase activity and the E-mail : [email protected]. inability to grow on 5% NaCl agar. The natural © 2007, Acta Orthopædica Belgica. No benefits or funds were received in support of this study Acta Orthopædica Belgica, Vol. 73 - 2 - 2007 264 F. MICHELS, J. COLAERT, F. GHEYSEN, T. SCHEERLINCK 1996 a draining sinus tract developed on the right Table I. — Biochemical tests of the R. mucilaginosa isolate hip scar. The sinus tract was resected and debride- Biochemical test Reaction ment of a supposedly superficial infection was Adherence (blood agar) + performed. All cultures were negative. In 2002, a Growth in 5% NaCl – technetium bone scintigraphy revealed increased Catalase reaction + (weak) isotope uptake around the right femoral hip Coagulase reaction – implant, compatible with stem loosening. A Gelatin hydrolysis + labelled leukocyte scintigraphy was negative. Only Esculin hydrolysis + the femoral hip component was revised with an un- cemented stem and per-operative cultures were Table II. — Antibiotic susceptibilities of the R. mucilaginosa negative. identified as the pathogen in this case In October 2004 the patient was readmitted for Test Reaction persisting groin pain. He was apyretic and physical examination revealed swelling of the right hip and Penicillin R Oxacillin R pain on hip rotation. The white blood cell count Amikacin S 9 9 (WBC) was 7.86 ϫ 10 /l with 5.6 ϫ 10 /l neu- Levofloxacin S trophiles. The erythrocyte sedimentation rate Tetracycline S (ESR) was 30 mm/h (normal : < 20 mm/h) and the Erythromycin S C-reactive protein (CPR) level 47 mg/l (normal : 0- Vancomycin S 5 mg/l). Renal and liver parameters, urinalysis and Clindamycin S other laboratory tests were all within normal limits. R : resistant, S : susceptible. There was no heart murmur. During a debridement procedure in October 2004, abundant purulent fluid was found below the A two-stage revision of the right total hip arthro- tensor fasciae latae muscle. After 48 hours, all cul- plasty was performed in May 2005 (fig 1). All tures were negative, but because of the long and implants were removed, bone was debrided and a suspicious history of repetitive infections, agar spacer made of gentamicin-impregnated cement plates were incubated for another 24 hours. Finally, was implanted into the acetabulum and femoral gram-positive cocci were isolated on blood agar shaft. The cultures taken during implant removal (trypticase soy agar with 5% horse blood) but not were again positive for R. mucilaginosa. Anti- on Chapman agar, which is a selective agar for the microbial susceptibilities were unchanged. isolation of staphylococci as it contains 5% NaCl. Because of persisting high CRP levels and a per- The colonies were non-haemolytic, mucoid and sisting subpyretic state despite 6 weeks of intra- adherent to agar ; additional biochemical tests are venous antibiotic treatment a second debridement shown in table I. Based on these findings, the procedure was performed. After that, the patient pathogen was identified as R. mucilaginosa. received intravenous vancomycin during 4 weeks Although sensitivity screening was hampered by and the ESR and C-reactive protein level both the slow growth of the micro-organism, the germ decreased. Finally, a re-implantation procedure was was considered to be resistant to penicillin and performed 3 weeks later (fig 2). The postoperative oxacillin, but sensitive to several other antibiotics course was uncomplicated and intravenous (table II). An isotopic scintigraphy with labelled vancomycin was continued for 2 weeks. Six weeks lymphocytes showed limited hyperactivity around postoperatively the white blood cell count was the right femoral implant, compatible with a low- 8.97 ϫ 109/l, erythrocyte sedimentation rate grade infection. The patient was treated with lev- 28 mm/h and C-reactive protein level 15 mg/l. One ofloxacin but the effect on the erythrocyte sedi- year later, the white blood cell count, erythrocyte mentation rate and C-reactive protein levels was sedimentation rate and C-reactive protein level limited. were normal and the clinical result was excellent. Acta Orthopædica Belgica, Vol. 73 - 2 - 2007 ROTHIA MUCILAGINOSA 265 Fig. 1. — Preoperative AP radiograph : note the presence of Fig. 2. — Postoperative AP radiograph : two-stage revision cortical thickening and calcifications in the soft tissues around was performed with an antibiotic-loaded cement spacer (first the proximal femur. stage) and uncemented implants (second stage). DISCUSSION operative findings suggest the possibility of an unusual infection, the microbiology laboratory Prosthetic joint infections are extremely difficult should perform special staining and prolonged cul- to treat without a microbiological diagnosis. In our turing techniques for unusual germs such as : fungi, case, repetitive cultures were negative although the mycobacteriae, E. coli, Mycoplasma or Brucella clinical history strongly suggested a low-grade species, and small colony variants of Staphylo- infection. Finally, and after prolonged cultures, an coccus aureus (6). This requires a good collabora- unusual organism was found. tion between the orthopaedic and microbiology This favours the theory that some implant loos- department. In some cases, it might even require enings, considered as aseptic based on the absence specific expertise within both departments. of clinical signs of infection and failure to isolate Ultrasonication can be useful to disrupt the bacter- bacteria, might well be missed low-grade infec- ial biofilm layer and to increase the yield of stan- tions. As stated by Nelson et al (9) : “The absence dard culture techniques (9). Polymerase chain reac- of evidence was clearly not evidence of absence”. tion (PCR) can be used to amplify the genetic As such, cultures originating from joint replace- material of a pathogen and facilitate its detection ments should not only be performed on the classic even when present in very small amounts (7, 12). agar plates for 48 hours, but should also be incu- PCR techniques as well as the use of germ specific bated for at least five days in liquid enriched media. monoclonal antibodies and polyclonal antibodies When the history, physical examination or intra- combined with immunofluorescence microscopy Acta Orthopædica Belgica, Vol. 73 - 2 - 2007 266 F. MICHELS, J. COLAERT, F. GHEYSEN, T. SCHEERLINCK allowed detection of bacteria in culture-negative generally the most common origin, and although samples (12). These molecular diagnostic tech- the infection appeared only two years after a suc- niques seem promising but are not yet routinely cessful implantation, this possibility cannot be available. Moreover, clear cut criteria for the diag- excluded.