Antimicrobial susceptibility, β-lactamase and enterotoxin production in Bacillus cereus isolates from clinical and food samples

The antimicrobial susceptibility of 30 clinical and 30 food Bacillus cereus isolates was determined. All isolates were susceptible to streptomycin, ciprofloxacin and gentamicin, 90 % of them to clindamycin and vancomycin, and 67 % to erythromycin. All isolates were resistant to amoxicillin with clavulanic acid, ampicillin, cefotaxime, ciprofloxacin, cloxacillin, cefotaxime with clavulanic acid and penicillin. The MIC values (determined by E-tests) were 48-256 mg/L for ampicillin, 0.19-1.5 mg/L for gentamicin, 0.125-1.0 mg/L for clindamycin, 0.047-4.0 mg/L for erythromycin and 1.5-16 mg/L for vancomycin. The MICs 4.6-18.75 g/L were observed for penicillin using the microdilution method. The presence of metallo-beta-lactamases was detected by E-test for 100 % of strains. Nonhemolytic diarrheal enterotoxin (NHE) was produced by 98.3 % of strains, while 31.7 % of them produced hemolytic diarrheal enterotoxin (HBL). Clinical isolates produced 10 % more HBL than food isolates. The psychrotrophic strains isolated from food samples produced NHE at 6.5 A degrees C in 73 % of cases.