Determination of antibiotic susceptibility and fatty acid methyl ester profiles of Bacillus cereus strains isolated from different food sources in Turkey

Abstract

In this study, a total of 77 Bacillus cereus isolates were obtained from four different food samples (58 raw milks, 8 chickens, 7 cereals and 4 meats) consumed in Turkey by using Chromogenic Bacillus Cereus Agar (Oxoid, CM1036). They were tested for susceptibilities to a total of 10 different antibiotics (penicillin, oxacillin, sulphamethoxazole, rifampicin, apromycin, amikacin, tobramycin, kanamycin, gentamicin and oflaxacin). In addition, they were determined to be in fatty acid methyl esters (FAMEs) group of the strains. All the isolates were identified as B. cereus based on colonical, cellular morphology and biochemical characters, including FAME analysis. A total of 25 different fatty acids were detected in 77 strains tested, but 16 of them appeared as minor components, in less than 2%. The strains had 15:0 iso 3OH (30.25%), 16:0 iso (11.23%), 17:0 iso (9.20%),16:0 (9.02%),13:0 iso (8.85%), 14:0 iso (6.79%), 15:0 anteiso (4.83%), 14:0 (4.58%), 16:1 ω6c (3.92%) and 16:1 ω7c (3.92%) as the major fatty acids (FA). Based on FAME analysis, the isolates were clustered into three main groups. Cluster 1, 2 and 3 were composed of the 71, 3 and 3 strains, respectively. All the strains in each cluster showed an extremely high degree of similarity (95 - 100%) to each other. Antibiotic resistant profile showed that all strains were resistance to penicillin and oxacillin, but they were highly susceptible to gentamicin and oflaxacin.