Anaerobic bacteria isolated from clinical specimens in a university hospital and resistance of anaerobic Gram negative rods to antibiotics

Abstract

Objective: Although anaerobic bacteria are normal microbiota members in humans, they can cause endogenous and exogenous infections. The empirical treatment of anaerobic infections is based on reports of susceptibility patterns reported in various studies. This study aims to identify the anaerobic bacteria isolated from clinical samples in 2018 and to determine the resistance of anaerobic Gram negative rods to antibiotics and to compare the results obtained with the results of anaerobic Gram negative rods isolated between 2015 and 2017 in the same unit in this study.Material and method: Specimens were inoculated on Schaedler Agar and Cooked Meat Broth and incubated in anaerobic conditions. Bacteria were identified by colony morphologies, conventional tests and anaerobic diagnostic discs. Antibiotic susceptibility tests were performed using the concentration gradient method and evaluated according to the criteria of CLSI.Results: Of the 1,630 clinical samples sent for anaerobic culture, 41 (2.5%) anaerobic bacteria were isolated. Most of the bacteria were isolated from the Department of Gynecology and Obstetrics (29%), Otorhinolaryngology (29%) clinics and mostly abscess specimens (49%). Seventy-one percent of the isolated anaerobic bacteria were Gram negative and 29% Gram positive bacteria. The most frequently isolated anaerobic bacteria were Bacteroides fragilis group (24%) and Prevotella spp (22%). Clindamycin resistance was quite high and there was no carbapenem resistance in anaerobic Gram-negative rods, but one third of the isolates were resistant to amoxicillin+clavulanic acid.

Conclusion: It was remarkable that more than half of the isolated anaerobic Gram negative rods, especially the B. fragilis group, were resistant to clindamycin and about a third of amoxicillin+ clavulanate. Increased resistance to these antibiotics used empirically in the treatment of infections caused by anaerobic Gram-negative rods is anticipated to limit antibiotic treatment regimens in the future. Routine monitoring of resistance is necessary for proper empirical treatment.