Increased risk of joint failure in hip prostheses infected with Staphylococcus aureus treated with debridement, antibiotics and implant retention compared to Streptococcus.

PURPOSE: The debridement, antibiotic and implant retention (DAIR) procedure is an option for patients with prosthetic hip joint infections for whom arthroplasty removal is problematic. Unfortunately, some of the guidelines proposed for deciding on DAIR management of arthroplasty infections fail to take into consideration the role of the infecting pathogen. While Staphylococcus aureus and streptococci are major contributors to infected hip arthroplasties, their respective contributions to treatment success or failure rates with the DAIR procedure have not been thoroughly analysed from a microbiological perspective. METHODS: This retrospective study included all patients who were hospitalised in Geneva University Hospitals between 1996 and 2012 and were initially treated with DAIR for prosthetic hip joint monomicrobial infection due to S. aureus or Streptococcus spp. The outcome of DAIR treatment was evaluated after a minimal follow-up of two years. A literature search was also performed to retrieve data from additional DAIR-treated cases in other institutions. RESULTS: In our institution, 38 DAIR-treated patients with hip arthroplasty monomicrobial infections underwent at least one surgical debridement (median two, range one to five), exchange of mobile parts and concomitant targeted antibiotic therapy for several weeks or months. A literature search identified outcome data in other institutions from 52 additional DAIR-treated cases according to our study criteria. After merging our own data with those retrieved from other reports, we found a failure rate of 21 % instead of 24 % for S. aureus-infected, DAIR-treated patients, but no failure in 14 streptococcal-infected patients. In the pooled data, the failure rate linked with S. aureus infections was significantly higher than that with Streptococcus ssp. (19/90 vs 0/14 episodes; Fisher's exact test, P = 0.07). CONCLUSIONS: DAIR-treated patients with prosthetic hip joint infections due to S. aureus tended to have worse outcomes than those infected with Streptococcus spp. The specific influence of the infecting pathogen should be considered in future guidelines and recommendations.

Which Orthopaedic Patients Are Infected with Gram-negative Non-fermenting Rods?

Background : 1st and 2nd generation cephalosporins used for perioperative prophylaxis in orthopaedic surgery do not cover non-fermenting Gram-negative rods (NFR). Methods: Epidemiological cohort study of adult patients operated for orthopedic infections between 2004 and 2014 with perioperative cefuroxim or vancomycin prophylaxis. Exclusion of polyneuropathic ischemic foot infections and septic bursitis cases. Results: Of the total 1840 surgical procedures in the study, 430 grew Gram-negative pathogens (23%), of which 194 (11%) were due to NFR and 143 (8%) to Pseudomonas aeruginosa. Overall, 634 episodes (35%) involved orthopaedic implants (321 arthroplasties, 135 plates, 53 nails, and others). In multivariate analysis and group comparisons, especially preoperative antibiotic use (124/194 vs. 531/1456; p<0.01) was significantly associated with NFR. Conclusions: Overall proportion of NFR oscillated between 9% and 13% among our orthopaedic infections. Variables associated with NFR were antibiotic use prior to hospitalization. The low infection rate of NFR following elective surgery and the community-based epidemiology, has led us to keep our standard perioperative prophylaxis unchanged.

Staphylococcus aureus soft tissue infection may increase the risk of subsequent staphylococcal soft tissue infections.

BACKGROUND: Staphylococcus aureus is the most common cause of soft tissue infections. It is unknown, however, if a patient who has had such an infection is at greater risk for future soft tissue infections with S. aureus. METHODS: We conducted an epidemiological survey of adult patients hospitalized in the only public hospital in Geneva for treatment (usually combined surgical and medical) of a soft tissue infection caused by S. aureus. By reviewing nursing and medical records from the emergency department and hospital wards, we assessed whether or not they developed any other soft tissue infections (excluding a recurrence) after or before the index one. RESULTS: Among 1023 index episodes of soft tissue infections, 670 (65%) were caused by S. aureus, of which 47 were caused by methicillin-resistant strains (30 healthcare-associated and 17 community-acquired). The patients' median age was 51 years and 334 (34%) were immune-compromised. The median time span between the patient's first and last consultation (for any reason) in our hospital was 21.4 years (interquartile range, 10-30 years). In addition to their index infection, 124 patients (12%) developed a new nosocomial or community-acquired soft tissue infection. Among the index cases with an S. aureus infection, 92 (14%) had another soft tissue infection, compared to 32 (9%) who had a non-staphylococcal index infection (Pearson-χ2-test; p=0.03). Similarly, patients with an index S. aureus infection, compared to those with a non-S. aureus infection, had a higher rate of another soft tissue infection caused by S. aureus (χ2-test; p<0.01). In multivariate analysis, an index infection due to S. aureus shows a high association to further S. aureus soft tissue infections (logistic regression; odds ratio 2.5, 95% confidence interval 1.4-4.6). CONCLUSION: Among adult patients hospitalised for a soft tissue infection, those infected with S. aureus (compared with other pathogens) may be at higher risk of a subsequent soft tissue infection, particularly with S. aureus.

Clinical features of anaerobic orthopaedic infections.

Some patient populations and types of orthopaedic surgery could be at particular risk for anaerobic infections. In this retrospective cohort study of operated adult patients with infections from 2004 to 2014, we assessed obligate anaerobes and considered first clinical infection episodes. Anaerobes, isolated from intra-operative samples, were identified in 2.4% of 2740 surgical procedures, of which half (33/65; 51%) were anaerobic monomicrobial infections. Propionibacterium acnes, a penicillin and vancomycin susceptible pathogen, was the predominantly isolated anaerobe. By multivariate analysis, the presence of fracture fixation plates was the variable most strongly associated with anaerobic infection (odds ratio: 2.1, 95% CI: 1.3-3.5). Anaerobes were also associated with spondylodesis and polymicrobial infections. In contrast, it revealed less likely in native bone or prosthetic joint infections and was not related to prior antibiotic use. In conclusion, obligate anaerobes in our case series of orthopaedic infections were rare, and mostly encountered in infections related to trauma with open-fracture fixation devices rather than clean surgical site infection. Anaerobes were often co-pathogens, and cultures most frequently recovered P. acnes. These observations thus do not support changes in current practices such as broader anaerobe coverage for perioperative prophylaxis.

Do diabetic foot infections with methicillin-resistant Staphylococcus aureus differ from those with other pathogens?

There is controversy as to whether or not diabetic foot infections (DFIs) caused by methicillin-resistant Staphylococcus aureus (MRSA) are associated with worse outcomes than DFIs caused by other pathogens. To address this issue we performed a nonsystematic literature search of published articles in English language journals seeking studies reporting on the outcomes of DFIs related to their microbiology. We retrieved 48 articles published from 1999 to 2013 that described a total of 7771 cases of DFI. The overall proportion of DFIs with an isolate of S aureus was about 30%; just over one third of these (11% of all cases) were MRSA strains. Among the DFI cases caused by MRSA 1543 were episodes of soft tissue infections and 113 of osteomyelitis, while non-MRSA organisms caused 5761 soft tissue infections and 354 cases of osteomyelitis. Only 5 of the included articles attempted a comparison between DFI caused by MRSA and those caused by other pathogens, with no clear differences noted. The median total duration of antibiotic therapy for DFI caused by MRSA was 26 days, of which a median of 10 days was given intravenously. Only a few articles reported the proportion of patients with a recurrence, but they often did not differentiate between MRSA and non-MRSA cases. Four publications reported a worse functional or microbiological outcome in MRSA, compared to non-MRSA, cases, but the findings were variable and differences did not seem to be significant. Many trials failed to adjust for case-mix or to definitively demonstrate a relationship between microbiology and outcomes. Few of the articles specifically commented on whether the MRSA isolates were health care- or community-acquired strains. Notwithstanding the substantial limitations of the available literature, there does not appear to be a need for any special treatment for DFI caused by MRSA. The current guidelines for treating according to established international recommendations seem appropriate.