General charecteriticks and clinical diagnosis ,symptoms and prevention of Bacillus cereus

1. Bacillus cereus
BY
N.Mathan
BP211508
I MSc Applied Microbiology
Sacred Heart College

2. SYNOPSIS
 General Charecteristics
 Pathogenicity
 Disease Transmission
 Incubation Period
 Virulence Factors
 Pathogenesis
 Clinical Disease
 Laboratory Diagnosis
 Microscopic Examination
 Colony Morphology On Culture Medium
 Biochemical Test
 Antibiotic Theraphy And Prevention

3. GENERAL CHARACTERISTICS
Gram positive Bacteria
Rod Shape
Motile
Capsule Absent
Spore formation
Aerobic/ F.A
30°to 40° C(Temp)
4.5 to 9.3 (Ph)

4. Not considered as normal flora
Isolated from soil, milk, cereals, spices.,etc….
Saprophytic species of Bacillus sp.
Not Easily killed by alcolhol
Grace frankland isolated from the air in cowshed in 1887
Habitat

5. PATHOGENICITY OF Bacillus cerus
DISEASE TRANSMISSION
 Primary Mode Of Transmission Is Via The Ingestion Of
Bacillus Cereus Contaminated Food
 Emetic Type Of Food Poisoning
 Associated With The Consumption Of Rice And Pasta
 The Diarrheal Type Is Transmitted Mostly By Milk Products,
Vegetables And Meat.
 It Forms Spores And Spreads Easily.

6. INCUBATION PERIOD
1 to 6 Hours
VIRULENCE FACTORS OF Bacillus cereus
 Enterotoxin (causes Gastroenteritis)
 Emetic form (Heat stable enterotoxin)
 Diarrheal form (Heat labile enterotoxin)
 Hemolysis
 Cytolysis
 Necrotic toxin (Heat labile enterotoxin)
 Cereolysin (Potent hemolysin named after the species)
 Phospholipase C (Potent Lecithinase)
 Collagenase

7. PATHOGENESIS OF Bacillus cereus
 Food poisoning
 Diarrhoeal syndrome
 Emetic syndrome
 From its production of enterotoxins in the gastrointestinal tract.
 105 – 107 g dosage of ingested food is Diarrhoeal
syndrome
 105 – 108 g dosage of ingested food for Emetic syndrome
 Enterotoxins associated with Diarrhoeal syndrome are unresistant
to the acidic conditions
 Emetic syndrome is more resistant to acidic conditions and
remains active at 121 °C.

8.  Cause food-borne intoxications, it has been reported to cause local
and systemic infections.
 Also cause ocular infections
Toxins
 Necrotic toxin
 Cereolysin
 Phospholipase

9. CLINICAL DISEASES CAUSED BY Bacillus cereus
 Gastroenteritis
 Emetic Form Gastroenteritis
 Implicated Food Rice
 Incubation Period <6
 Symptoms Is Nausea, Vomiting, Abdominal Cramps.
 Duration 8to10
 Enterotoxin Heat Stable
Diarrheal Form Gastroenteritis
 Implicated Food Meat Vegetables
 Incubation Period >6
 Symptoms Diarrhea, Vomiting, Abdominal Cramps
 Duration 20to36
 Enterotoxin Heat Labile

10. Ocular infections
 Keratitis
 Endophthalmitis
 Panophthalmitis
Severe Pulmonary disease
 can produce severe Anthrax like Pulmonary disease

11. LABORATORY DIAGNOSIS OF Bacillus cereus
MICROSCOPIC EXAMINATION
 Gram stating – Violet coloured Gram positive gram
positive rods in singles, pairs, or serpentine with square
ends.
 Motility test – Motile.
 Endospore staining - Green coloured Endospores and Red
coloured Vegetative cells.

12. COLONY MORPHOLOGY ON CULTURE MEDIUM
 Nutrient agar – Large, feathery, spreading, dull, gray, granular,
spreading colonies and opaque with a rough matted surface and
irregular perimeters
 Blood agar – Bacillus cereus shows Beta – hemolysis in Blood
agar.
 MacConkey agar – White coloured Non-Lactose fermenting
colonies.
 Bacillus cereus Selective Agar – Pea cock blue coloured colonies.

13. BIOCHEMICAL TESTS
 Catalase test - Positive
 Oxidase test - Negative
 Urease test - Negative
 Indole test – Positive
 Methyl Red (MR) test - Negative
 Voges Proskauer (VP) test - Positive
 Citrate utilization test – Positive
 Nitrate reduction - Positive
 Gelatine hydrolysis – Positive
 Casein hydrolysis – Positive
 Arginine Dehydrolase – Positive
 Esculin hydrolysis – Positive
 Lysis by Gamma phage - Negative

14. ANTIBIOTIC THERAPY AND PREVENTION
Ocular infection is treated by using Clindamycin,
Erythromycin, Vancomycin, Aminoglycosides and
Tetracycline.
Proper cooking of food.
Refrigeration of food materials

15. THANK YOU