Clinico-microbiological spectrum of anaerobic pyogenic infections in an Indian tertiary care teaching hospital: A two-year study.

Abstract

Anaerobes are important however the most neglected pathogens. Timely isolation of anaerobes can guide the clinician about the correct course of clinical treatment and thus reduce the mortality and also the problem of antimicrobial resistance. Tissue and/or pus aspirates were collected aseptically from infectious sites in the Robertson's cooked meat medium (RCM) and sent to anaerobic bacteriology laboratory for culture. Subcultures from RCM for each sample were done on neomycin blood agar and 5% sheep blood agar along with metronidazole disc (5μg). The plates were incubated in an anaerobic jar using GasPak for 72 hrs. The preliminary identification was performed by standard biochemical tests for both obligate and facultative anaerobic isolates. Speciations of obligate anaerobes were performed by Vitek 2 automated system. Obligate anaerobes either single or polymicrobial were obtained in 38/216 (14.5 %) samples processed during the study period. Polymicrobial infections were reported in 21/216 (55.26%) samples and most commonly with obligate anaerobic gramnegative bacilli i.e. <i>Prevotella-Porphyromonas and Bacteroides fragilis</i> group. Most common monomicrobial anaerobic infections were observed with <i>Veillonella spp</i>. (n=4) and <i>Porphyromonas spp</i>. (n=4) followed by <i>Bacteroides fragilis</i> (n=3). Obligate anaerobes were predominantly isolated from skin and soft tissue infections (n=14) followed by surgical site infections (n=8). Although most of the infections are polymicrobial, a rise in the incidence of monomicrobial anaerobic infections has been noticed. Therefore, the performance of anaerobic cultures along with aerobic cultures is much needed for complete bacterial work-up of specimens from infectious sites and better patient management.