Identification and detection of antibiotic susceptibility of the most common anerobes causing infection in surgical hospital, Faculty of Medicine Zagazig University, Egypt

Abstract

Objectives: Anaerobic infections are considered to be the most difficult organisms to be identified in the microbiology laboratory. It requires strict conditions, proper sampling , long time and laboratory skills. In addition most of them are mixed infections having both aerobic and anaerobic organisms. Choice of the proper antibiotic for treating these anaerobes is live saving for the patient.

Methods: Identification of anaerobic organisms using MALDI-TOF (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry) as a recent tool for identification together with API 20A (as a reference method). Antibiotic susceptibility test was done for the anaerobic isolates using Agar Dilution Method. With the the most commonly used antibiotic in our hospital which are Amoxacillin/Clavulonic acid, clindamycin, metronidazole and Imipenem.

Results: Anaerobic infections constitutes 21.7% of total 249 specimen from different surgical departments. Bacteroids spp. (41%) were the most prevalent anaerobic organisms followed by peptostreptococcus (26.9%). MALDI TOF MS system and API achieved 100% agreement for identification of Porphoryomonas spp. and Fusobacterium, while near results were obtained for other isolates. Bacteroid spp. shows the highest rate of resistance to clindamycin (69%). Excellent results were obtained for Imipenem and metronidazole. Most of resistance to Amoxacillin/Clavulonic acid is related to Bacteroid spp. and Fusobacterium spp.

Conclusion: MALDI TOF MS System is a useful tool for identification of. Anerobes are showing higher rates of resistance to commonly used antibiotics thus detection of resistant strains is vital for proper selection of antibiotics.

Keywords: Anaerobes, MALDI TOF System, API 20, Agar Dilution Method, Zagazig