Media of Choice

 All Bacillus and related genera grow well on 5% sheep blood agar, chocolate agar, routine blood culture media, and nutrient broths. Isolates susceptible to nalidixic acid will not grow on Columbia agar with nalidixic acid and colistin (CNA), a selective and differential medium for gram-positive organisms. Phenylethyl alcohol agar (PEA), an additional selective agar for gram-positive organisms, is useful for the removal of contaminating organisms and the isolation of Bacillus spp. Polymyxin-lysozyme-EDTA thallous acetate (PLET) can be used for selection and isolation from contaminated specimens. Colonies appear as creamy white, domed, circular colonies. Additionally, bicarbonate agar is used to induce B. anthracis capsule formation, providing a means for presumptive morphologic identification.

B. cereus media referred to as mannitol, egg yolk, and polymyxin B agar (MEYP or MYP); polymyxin B, egg yolk, mannitol, bromthymol blue (PEMBA); and B. cereus medium (BCM) have been developed for the specific isolation and identification of the organism. These media take advantage of the phospholipase C positive reaction on egg yolk agar, no production of acid from mannitol, and incorporation of pyruvate or polymyxin as the selective agents.

Heat shock treatment can be utilized for the growth and enhancement of endospores from clinical specimens. Heat treatment at 70° C for 30 minutes or 80° C for 10 minutes is effective for killing vegetative cells and retaining spores for most Bacillus spp. B. anthracis heat treatment is carried out at lower temperatures, 62° to 65° C for 15 to 20 minutes. Following heat treatment, samples are plated to culture medium along with a sample of untreated specimen to ensure maximal recovery of the isolate.

Incubation Conditions and Duration

Most species will produce detectable growth within 24 hours following incubation on media incubated at 35° C, in ambient air, or in 5% carbon dioxide (CO2). Bicarbon ate agar requires incubation in CO2.

 Colonial Appearance

 Table 1 describes the colonial appearance on blood agar and other distinguishing characteristics (e.g., hemolysis) of each species of Bacillus or related genera.

Colonies of B. anthracis growing on bicarbonate agar appear large and mucoid.

Table1. Colonial Appearance and Other Characteristics

مواضيع ذات صلة

The Growth Curve in Batch Culture

The Measurement of Microbial Concentrations

Bacterial Pathogenesis

Distribution of Normal Flora in The Body

Diagnostic Laboratory Tests for Borrelia Burgdorferi

Bacterial Cell wall

Bacillus cereus

Bacillus anthracis

Antimicrobial Susceptibility Testing and Therapy for Streptococcus,Enterococcus, and Similar Organisms

Serodiagnosis Of Streptococcus,Enterococcus, and Similar Organisms

Approach To Identification of Streptococcus, Enterococcus, and Similar Organisms

Criteria For Identification of Bacteria