Antimicrobial susceptibility and β-lactamase production in Bacillus cereus isolates from stool of patients, food and environment samples
2016
Background/Aim. Bacillus cereus (B. cereus) usually ingested by food can
cause two types of diseases: vomiting due to the presence of emetic toxin and
diarrheal syndrome, due to the presence of diarrheal toxins. Systemic
manifestations can also occur. The severe forms of disease demand antibiotic
treatmant. The aim of this study was to determine the differences in
antibiotic susceptibility and β-lactamase activity of B. cereus isolates from
stools of humans, food and environment. Methods. Identification of B. cereus
was performed with selective medium, classical biochemical test and
polymerase chain reaction (PCR) with primers specific for bal gene. Thirty
isolates from each group were analysed for antibiotic susceptibility using
the disk-diffusion assay. Production of β-lactamase was determined by
cefinase test, and double-disc method. Results. All strains identified as B.
cereus using classical biochemical test, yielded 533 bp fragment with PCR.
Isolates from all the three groups were susceptible to imipenem, vancomycin,
and erythromycin. All isolates were susceptible to ciprofloxacin but one from
the environment. A statistically significant difference between the groups
was confirmed to tetracycline and trimethoprim-sulphamethoxazole sensitivity.
A total of 28/30 (93.33%) samples from the foods and 25/30 (83.33%) samples
from environment were approved sensitive to tetracycline, while 10/30
(33.33%) isolates from stools were sensitive. Opposite to this result, high
susceptibility to trimethoprim-sulphamethoxazole was shown in samples from
stools (100%), while isolates from foods (63.33%) and from environment (70%)
had low susceptibility. All samples produced β-lactamases. Conclusion. The
strains of B. cereus from all the three groups showed high rate of
sensitivity to most tested antibiotics, except to tetracycline in samples
from human stool and to trimethoprim-sulphamethoxazole in samples from food
and environment. The production of β-lactamases was confirmed in all the
strains.
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