Cultivation of Bacillus and Similar Organisms
المؤلف:
Patricia M. Tille, PhD, MLS(ASCP)
المصدر:
Bailey & Scotts Diagnostic Microbiology
الجزء والصفحة:
13th Edition , p269-270
2025-05-29
572
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
الاكثر قراءة في البكتيريا
اخر الاخبار
اخبار العتبة العباسية المقدسة
