Multidrug-Resistant Gram-Negative bacilli Prosthetic Joint Infection: A Worrisome Scenario

BACKGROUND: The spectrum of the microbial etiology of prosthetic joint infections (PJIs) is changing, with a higher occurrence of Gram-negative bacilli (GNB) nowadays. In Latine America, GNB infections are usually caused by strains that produce multiple resistance mechanisms, making antimicrobial treatment increasingly difficult, especially for these biofilm-associated infections. We aimed to demonstrate the higher frequency of PJIs caused by GNB. METHODS: We performed a retrospective observational study with adult patients with a diagnosis of knee and hip PJIs. Patients included were submitted to an exchange of total hip and knee prostheses between September 2010 and December 2016, in two brazilian hospitals. It was included only patients with microbial diagnosis performed using either sonication fluid cultures of retrieved implant and conventional tissue cultures of periprosthetic tissues. The Infectious Disease Society of America (IDSA) definition was used to establish the diagnosis of PJIs. Multidrug-resistant (MDR) organisms were defined as acquired resistance to at least one agent in three or more antimicrobial categories. RESULTS: Were included 130 adult patients with a median age of 65.5 years, in which 60% were female. Infected hip arthroplasty was more frequent than knee infections (69% vs. 31%) and 61% were classified as late infection according to Zimmerli’s classification. One hundred twenty-three microorganisms were isolated on the tissue and sonication fluid culture. Despite the Coagulase-negative Staphylococci was the predominant microorganism (35%), Gram-negative bacilli had an expressive frequency of 30% of positivity on culture. Amongst them, 23% showed resistance to carbapenens and 38% were MDR-bacteria. The predominant microorganism was Pseudomonas spp., followed by Enterobacter spp., Acinetobacter spp., Escherichia coli, Stenotrophomonas maltophilia and Klebsiella pneumoniae, Proteus spp. and Serratia marcescens. There was no statistical difference on the resistance profile of the GNB isolated on tissue and sonicate fluid culture. CONCLUSION: We have shown an alarming high frequency of MDR-Gram-negative bacilli PJIs in two Brazilian centers, performing microbial diagnosis using sonication and tissue cultures. DISCLOSURES: All authors: No reported disclosures.