B. cereus is another clinically relevant species worthy of identification. It is penicillin resistant, beta-hemolytic, and motile, and it produces a wide zone of lecithinase on egg yolk agar (Figure 1).

Fig1. Lecithinase production by Bacillus cereus on egg yolk  agar. The organism has been streaked down the center of the plate.  The positive test for lecithinase is indicated by the opaque zone of  precipitation around the bacterial growth (arrows). 

 Epidemiology

 B. cereus, a very close relative to B. anthracis, is also found within the soil. The organism is considered an opportunistic pathogen and is often associated with foodborne illness.

 Pathogenesis and Spectrum of Disease

 B. cereus “food poisoning” is associated with the ingestion of a wide variety of foods including meats, vegetables, deserts, sauces, and milk. A higher incidence is seen following the ingestion of rice dishes. Following ingestion patients present with one of two types of symptoms: diarrhea and abdominal pain within 8 to 16 hours or nausea and vomiting within 1 to 5 hours. B. cereus produces several toxins implicated in the diarrheal symptoms, including hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe), and cytotoxin K (CytK). The three toxins are believed to act synergistically, with Nhe responsible for the major symptoms in the diarrheal presentation of the infection. The emetic form of illness is associated with a heat-stable, proteolysis, and acid resistant toxin, cereulide, produced in food.

In addition to the food poisoning associated with B. cereus, it is a serious pathogen of the eye, causing progressive endophthalmitis. Identification of B. cereus from a patient’s eye can cause permanent damage and should be reported to the physician immediately.

مواضيع ذات صلة

Bacillus anthracis

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Serodiagnosis Of Streptococcus,Enterococcus, and Similar Organisms

Approach To Identification of Streptococcus, Enterococcus, and Similar Organisms

Criteria For Identification of Bacteria

Taxonomy—The Vocabulary of Medical Microbiology

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Pathogenesis and Spectrum of Disease of Streptococcus Pneumonia and Viridians Streptococci

Pathogenesis and Spectrum of Disease of Beta- Hemolytic Streptococci

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