Genus: bacillus

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Genus Bacillus

Genus Clostridium



• Aerobic, non-motile ,spore-forming, gram-positive chain forming rods.

• Bacillus species are ubiquitous saprophytes Important huma pathogen

B. anthracis

B. cereus

Bacillus anthracis

• Major agent of bioterrorism and biological warfare

• Major pathogen of domesic herbivores that come in contact with


Pathogenesis and Clinical feature:

Acquired by the entry of spores through injured skin incutaneous anthrax, or mucus membrane in intestinal anthrax, or inhalation of spores in the lung while handling skin and hides

Laboratory diagnosis:

Specimen: Fluid or pus from skin lesion, Blood, sputum

Smear: Non-capsulated gram-positive rods with centrally

located spores from culture

Large capsulated gram-positive rods without spores from primary specimen.

Culture: Grows aerobically in ordinary media over wide range of temperature. Non-hemolytic ,large, dense, grey-white irregular colonies with colony margin of “Medussa Head” or“curled-hair lock” appearance due to composition of parallel chaining of cells

Biochemical reaction:

Gelatin-stab culture: Gelatin liquefactionGrowth along the track of the wire with lateral spikes longest near the surface Providing “inverted fur tree”appearance.

Serology: ELISA has been developed to measure antibodies to edema toxin and lethal toxin

Positive result: 4-fold change or single titer > 1:32

Bacillus cereus

General characteristics:

Exhibit motility by swarming in semisolid media Produce β lactamase, so not sensitive to penicillin

Clinical features

1. Food poisoning

Lab. Diagnosis

>105 org/gm of food Isolation of B.cereus in stool is not diagnostic since it is present in normal stool specimen

Treatment: Fluid replacement , Antibiotics not required

2. Ocular infection

Ocular disease following trauma from non-sugical penetrating

Objects Manifests with keratitis, endophthalmitis, and panophthalmitis

Treatment: Clindamycin + Aminoglycosides

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