The European committee on antimicrobial susceptibility testing disc diffusion susceptibility testing method for frequently isolated anaerobic bacteria. Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases OBJECTIVES:Antimicrobial resistance in anaerobic bacteria is increasing and there is a link between inappropriate antimicrobial therapy and poor clinical outcome in the treatment of infections caused by anaerobic bacteria. Accurate and timely antimicrobial susceptibility testing of anaerobic bacteria is therefore of critical importance. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) has recently described a disc diffusion susceptibility testing method for anaerobic bacteria using fastidious anaerobe agar (FAA) supplemented with 5% defibrinated horse blood (HB). This method was previously validated for Bacteroides spp. only. The aim of this study was to determine the suitability of FAA-HB for disc diffusion and also for frequently isolated anaerobic bacteria. METHODS:Clinical isolates, including 54 Bacteroides/Phocaeicola/Parabacteroides spp., 49 Prevotella spp., 51 Fusobacterium necrophorum, 58 Clostridium perfringens, and 54 Cutibacterium acnes were evaluated against six antimicrobial agents. MICs were determined by agar dilution following Clinical and Laboratory Standards Institute methodology, modified to use FAA-HB as recommended by EUCAST, instead of supplemented Brucella agar, and disc diffusion was performed on FAA-HB following EUCAST methodology. RESULTS:Results for quality control strains were reproducible, with 99.3% of zones within range. Disc diffusion by EUCAST methodology was able to distinguish between susceptible and resistant isolates of anaerobic bacteria for benzylpenicillin, piperacillin-tazobactam, meropenem, clindamycin, and metronidazole (98.7% correct categorization). No isolates resistant to vancomycin were tested, but zone diameters correctly categorized the susceptible isolates, and there was a logical relationship between MICs and inhibition zones. DISCUSSION:The recently published EUCAST method for disc diffusion for anaerobic bacteria based on FAA-HB is a reproducible and accurate method for susceptibility testing of frequently isolated anaerobic bacteria. 10.1016/j.cmi.2023.01.027

Antimicrobial susceptibility testing of anaerobic bacteria causing bacteremia: A 13-year (2010-2022) retrospective study in a tertiary hospital. Anaerobe Infections from anaerobic microorganisms result from breached mucosal barriers, posing a significant mortality risk. A retrospective study at Hospital Universitario La Paz (Madrid) from 2010 to 2022 analyzed 491 (6.17 %) anaerobic bacteremia cases out of 7956 significant bacteremia cases among 171,833 blood culture requests. Bacteroides fragilis was the most frequently isolated species (28.3 %), followed by Clostridium perfringens (13.6 %). B. fragilis showed good susceptibility to amoxicillin/ clavulanic acid (86 %), piperacillin/tazobactam (86 %), and metronidazole (87.7 %). In general, non-fragilis Bacteroides species showed low susceptibility to penicillin (7 %), amoxicillin (17.5 %), and clindamycin (64.9 %). Of our 13 non-perfringens Clostridium isolates, four exhibited resistance to penicillin and four showed resistance to clindamycin. Lactobacillus species were highly susceptible to antibiotics tested. Prevotella spp. showed low susceptibility to penicillin (20 %), amoxicillin (20 %), and clindamycin (40 %). The study contributes valuable data for monitoring and improving anaerobic bacteremia treatment. 10.1016/j.anaerobe.2023.102803

Antimicrobial susceptibility testing of anaerobic bacteria: In routine and research. Anaerobe To date, antimicrobial susceptibility testing (AST) in anaerobes is highly disarrayed. The testing is not routinely performed in many laboratories to direct appropriate antimicrobial therapy, and literature on AST remains scarce. This review aims to present the current methods employed for the AST of anaerobic bacteria both in routine and research. Anaerobes are potential human pathogens and predominate the human microbiota. Despite their significant role in human health and disease, they are not paid enough heed. The educated experience-based treatment has often been instituted with anaerobic infections due to the challenging AST and relatively predictable patterns of antimicrobial resistance (AMR). However, the AMR in anaerobes remains no more predictable, especially in Gram-negative anaerobes like Bacteroides spp., where multi-drug resistance is also emerging. The changing antibiograms and the emergence of resistance determinants in anaerobes necessitate routine AST, periodic monitoring, and literature review of these organisms. The present scenario dictates to limit the empirical management of anaerobic infections and encourage consistent AST practice in routine by employing economical, faster, and more pragmatic approaches, especially in tertiary care setups that cater to a vast patient population and are held accountable for producing accurate clinical and surveillance data. The article may provide a broad perspective on the topic and different AST solutions. 10.1016/j.anaerobe.2022.102559