Isolation, identification and antimicrobial susceptibility of Bacteroides fragilis group strains recovered from broiler faeces

Abstract

1. The objective was to evaluate the occurrence of cultivable components of the Bacteroides fragilis group in faeces of broiler chickens and their antimicrobial susceptibility patterns. 2. Faecal samples of 36 × 45-d-old Cobb broilers of both sexes from 15 different flocks on one farm were diluted 10-fold and plated on to Bacteroides-bile-esculin agar for colony count and isolation. Identification was by molecular methods and antimicrobial susceptibility in the agar dilution assay. 3. A total of 236 isolates was recovered from a mean population of 3·32 × 107 colony-forming units/g of faeces. B. fragilis was shown to be the predominant Bacteroides species (45·3%), followed by B. distasonis (35·6%), B. vulgatus (8·9%), B. ovatus (2·5%) and B. stercoris (1·3%). 4. Among 204 bacterial isolates tested, high resistance to ampicillin (98·5%), norfloxacin (95·1%) and tetracycline (88·2%) were observed. High (89·7%) multi-drug resistance was observed to 3–7 of the tested drugs. 5. Components of the B. fragilis group were sub-dominant in broiler faecal microbiota, with a different species pattern compared with human and high antimicrobial multi-drug resistance.