Characterisation of Anaerobes Isolated from Various Clinical Samples: A Cross-sectional Study

Abstract

Introduction: Anaerobes are an important cause of infections but are often neglected. These infections can range from simple abscesses to life-threatening infections. The isolation of anaerobes is crucial for administering appropriate antibiotic therapy. Aim: To investigate the profile of anaerobes in various clinical samples, including deep-seated skin and tissue infections, aspirated body fluids, and tissue biopsies. Materials and Methods: A cross-sectional study was conducted on a total of 100 samples at the Department of Microbiology, ABVIMS and Dr RML Hospital, New Delhi, from November 2019 to March 2021. Aspirations from deep-seated abscesses, body fluids, intraoperative samples, and tissue biopsies meeting the criteria for anaerobic culture were included. Simultaneous processing for the detection of aerobes was also performed. Anoxomat III anaerobic culture system was used to create an anaerobic environment. Robertson Cooked Meat (RCM) broth was used, and subculture was conducted on 10% Blood Agar (BA). Presumptive identification was performed using gram stain, catalase test (15% hydrogen peroxide), metronidazole disc (5 µg), special potency disc (vancomycin 5 µg, kanamycin 1000 µg, colistin 10 µg), and aerotolerance test. The Vitek 2 compact ID system was used for the final identification of anaerobes. Statistical Package for Social Sciences (SPSS) software, IBM manufacturer, Chicago, USA, ver 21.0, was utilised. Results: The isolation rate of anaerobes was 17 (17%), with Bacteroides fragilis being the predominant organism (6; 35.29%), followed by Actinomyces (2; 11.76%), Clostridium (2; 11.76%), Peptostreptococcus (2; 11.76%), and Prevotella species (2; 11.76%). Isolation was observed from diverse anatomic sites, with pus aspirates constituting the majority of the isolates (9; 52.94%), followed by brain abscesses (3; 17.65%), liver abscesses, peritoneal fluid (2; 11.76%), and tonsillar abscess (1; 5.89%). Five (29.41%) infections were polymicrobial, while 12 (70.59%) were monomicrobial in nature. Conclusion: Anaerobes are emerging as an important causative agents in a variety of diverse and heterogeneous pyogenic infections. This study demonstrates their isolation from various infection sites. Therefore, routine anaerobic cultures should be conducted alongside aerobic cultures, and the importance of anaerobes in clinical infections should not be underestimated.