Caracterização molecular e fenotípica de Bacillus cereus sensu stricto isolados de alimentos.

Abstract

Bacillus cereus sensu stricto (s.s.) is an opportunistic pathogen that can cause food poisoning or even serious human infectious diseases. The objective of this work was to carry out a molecular and phenotypic characterization of B. cereus s.s. isolated from different types of food, including B. cereus s.s. associated with foodborne outbreaks reported in the State of Minas Gerais. Affiliation to phylogenetic groups (I-VII) was determined through amplification and partial sequencing of the panC gene. Molecular characterization by MLST was determined through amplification and partial sequencing of the maintenance genes glp, gmk, ilv, pta, pur, pyc and tpi. Antimicrobial susceptibility was determined using the agar disk diffusion technique. 16 antimicrobials were tested. Of the 54 B. cereus s.s. analyzed by sequencing the panC gene, the majority were affiliated with phylogenetic groups IV (61.1%) and III (25.9%). The remaining B. cereus s.s. were distributed in groups V (9.3%) and II (3.7%). The combination of seven alleles for each of the 46 strains of B. cereus s.s. analyzed by MLST generated 31 STs, of which 17 already existed in the database. Among the 31 |STs identified, 14 STs (2811, 2812, 2813, 2814, 2815, 2816, 2817, 2943, 2945, 3101, 3103, 3104, 3105 and 3107) had not been described in the MLST database, and were, therefore, deposited. Of the 51 B. cereus s.s. analyzed using the agar disk diffusion technique, the most showed resistance to different β-lactams antibiotics, with the exception of imipenem. The highest resistance rates were amoxicillin-clavulanic acid (98.0%) and cefazolin (98.0%), followed by cephalexin (94.1%), ampicillin-sulbactan (88.2%), ampicillin (86.2%) and ceftriaxone (76.5%). On the other hand, most isolates were sensitive to the other antibiotics tested, including imipenem (100%), amikacin (100%), vancomycin (100%), ciprofloxacin (100%), gentamicin (98.0%), azithromycin (96.1%), tetracycline (96.1%), erythromycin (94.1%), chlorafenicol (92.2%) and clindamycin (60.8%). The present study revealed the genetic diversity and resistance profile of B. cereus s.s. isolated from different food types.