Presentation of Bacillus Cereus bacteria. For MBBS students for microbiology

1. BACILLUS
CEREUS
M.USAMA ASIF
ROLL NO.19081
PRCM&DC

2. SCIENTIFIC CLASSIFICATION
DOMAIN : BACTERIA
PHYLUM : FIRMICUTES
CLASS : BACILLI
ORDER : BACILLALES
FAMILY : BACILLACEAE
GENUS : BACILLUS
SPECIES : B.cereus

3. INTRODUCTION
 GRAM POSITIVE BACTERIA
 SPORE BEARING
 ROD SHAPED
 MOTILE
 FACULTATIVE AEROBE & ANAEROBE
 BETA HEMOLYTIC

4.  It is widely spread in nature and frequently isolated
from soil and growing plants. But it is also well adapted
for growth in the intestinal tract of insects and
mammals.
 It is becoming one of the important causes of food
poisoning in the industrialized world.

5.  B.cereus is a model species of “Bacillus cereus group” also
Known as Bacillus ceres sensu lato,comprising five closely related
Species:
1. B. anthracis
2. B. thuringiensis
3. B. mycoides
4. B. pseudomycoides
5. B. weihenstephansis
 These all share a genetic similarity but they have difference
in both Pathogenic properties and phenotypic traits of strains.

6. Optimum condition for Growth
Temperature:
Optimum : 30 – 37°C
Range : 4 – 55°C
 Maximum toxin production occurs at 20 – 25°C
 Toxin production range at 10 – 40°C
pH:
Optimum : 6 – 7
Range : 4.5 – 9.5
Minimum water activity:
1. With NaCl > 0.93 and 0.95 aw
2. With glycerol 0.93 aw

7. For survival
Temperature:
 Spores more resistant to dry heat than moist heat. It is also more resistant in oily foods.
 Cooking at or below 100°C may allow spore survival.
pH:
 Vegetative cells decline generally rapidly in stomach acid.However, some may servive depending on
food and level of stomach acidity
 Spores are resistant to gastric acidity between pH 1 – 5.2.
Water activity:
 Spores survive long periods in dry foods
e.g : population unchanged after 48 weeks in serial 0.27 – 0.28w.

8. The white inclusions in the rode shaped bacteria are the spores.

9. Transmission
 B. cereus is isolated from rice, dairy products, vegetables, spices and some times it can
cause
cross contamination to other foods like meat products also.
 Spores on grains such as rice survive steaming and rapid frying.
 The spores germinate when rice is kept warm for many hours (e.g. reheated fried rice)
 The portal of entry is GIT.

10. Pathogenesis
B. cereus produces one type of emetic toxin and two types of enterotoxin.
 The mode of action of one of the enterotoxins is same as that of cholera toxin.
 The mode of action of other enterotoxin resembles that of staphylococcal enterotoxin.

11. Clinical Findings
There are two syndromes:
1. One syndrome has a short incubation period and consists primarily of nausea and
vomiting, similar to staphylococcal food poisoning.
2. The other has a long incubation period and features watery, non-bloody diarrhea
resembling clostridal gastroenteritis.

12. Local
Wound –
postoperative, burns,
abscess, trauma
Ocular – conjunctivitis,
panophthalmitis,
endophthalmitis,
keratitis
Osteomyelitis, arthritis
BACILLUS CEREUS INFECTION
GI infections
Diarrheal
syndrome
Emetic
syndrome
Non-GI infections
Systemic
Septicemia, endocarditis,
Respiratory, CNS

13. Laboratory Diagnosis
when grown under aerobic conditions on 5% sheep blood agar at 37°C , B.cereus colonies are dull,
grey and opaque with a rough matted surface.
Grey, opaque, granular, spreading colonies with
Irregular perimeters growing on 5% sheep blood agar.

14. Treatment
 Only symptomatic treatment is given.
Prevention
 There is no specific means of prevention.
 Rice should be kept warm for long periods.

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