Virulence factors and antibiotic profiles of Bacillus cereus isolated from stool and vomitus of inpatients with acute diarrhea

Abstract EN

Ninety five specimens were collected from inpatients suffering from diarrhea at Al-Zubair General Hospital, including 50 stool and 45 vomitus samples.

Bacillus cereus was presumptively identified by the appearance of red-purple colonies surrounded by a halo of white precipitate after culturing samples on the selective medium Mannitol-Egg Yolk Polymyxin B Agar (MYPA).

Identification was confirmed by characterization tests and resistance to penicillin.

B.cereus was recovered from 19 samples (20 %) : 13 from stool (26 %) and 6 from vomitus (13 %).

The highest recovery percentage was among children aged less than 10 years (30 %) and the least was from adults aged above 40 years (14 %) with significant difference (P > 0.05).

B.cereus was recovered in stool and vomitus specimens of the same patients in 8 cases.

All recovered isolates from vomitus were able to produce hemlysin, casienase and gelatinase (100 %) while only hemlysin and casienase were produced by all recovered isolates from stool.

Only 83.3 % of vomitus and 76.9 % of stool isolates were able to lyse starch.

Recovered isolates from both sources exhibit swarming motility with higher percentage shown by vomitus isolates (80 % VS 66.6 %).

Ability of B.cereus to grow at low temperatures was determined ; 40 % of each vomitus and stool isolates were able to grow and reproduce at 4OC, growth rate was raised to 80 % and 60 % at 6OC respectively and reached up to 100 % at 10OC.

The mean time for survival of spores of stool and vomitus isolates at 100OC was 4.1 and 4.25 min.

respectively.

The study has proved ability of stool isolate to produce enterotoxin when injected in the vein of mice tail.

Isolates from both sources were almost equally highly resistant to ampicillin, carbencillin, tetracycline and streptomycin.

The least resistance was toward gentamycin, erythromycin and chloramphenicol, which makes them the drug of choice.

Four patterns of antibiotic resistance were reported among isolates of B.

cereus.