Antigenic relationship of the endospores of Bacillus cereus-like insect pathogens to Bacillus cereus and Bacillus anthracis

Bacillus cereus and related species

Bacillus cereus is a gram-positive aerobic or facultatively anaerobic spore-forming rod. It is a cause of food poisoning, which is frequently associated with the consumption of rice-based dishes. The organism produces an emetic or diarrheal syndrome induced by an emetic toxin and enterotoxin, respectively. Other toxins are produced during growth, including phospholipases, proteases, and hemolysins, one of which, cereolysin, is a thiol-activated hemolysin. These toxins may contribute to the pathogenicity of B. cereus in nongastrointestinal disease. B. cereus isolated from clinical material other than feces or vomitus was commonly dismissed as a contaminant, but increasingly it is being recognized as a species with pathogenic potential. It is now recognized as an infrequent cause of serious nongastrointestinal infection, particularly in drug addicts, the immunosuppressed, neonates, and postsurgical patients, especially when prosthetic implants such as ventricular shunts are inserted. Ocular infections are the commonest types of severe infection, including endophthalmitis, panophthalmitis, and keratitis, usually with the characteristic formation of corneal ring abscesses. Even with prompt surgical and antimicrobial agent treatment, enucleation of the eye and blindness are common sequelae. Septicemia, meningitis, endocarditis, osteomyelitis, and surgical and traumatic wound infections are other manifestations of severe disease. B. cereus produces beta-lactamases, unlike Bacillus anthracis, and so is resistant to beta-lactam antibiotics; it is usually susceptible to treatment with clindamycin, vancomycin, gentamicin, chloramphenicol, and erythromycin. Simultaneous therapy via multiple routes may be required.

Identification of Bacillus anthracis by polyclonal antibodies against extracted vegetative cell antigens

The extractable protein antigens EA1 and EA2 of Bacillus anthracis were prepared from electrophoresis transblots of SDS extracts of vegetative bacteria of the Sterne strain. Hyperimmune guinea-pig antiserum against EA2 failed to react with B. anthracis cells in immunofluorescence (IF) tests. Guinea-pig antiserum against EA1 (anti-EA1) reacted strongly in IF tests with non-encapsulated vegetative cell of 10 of 12 strains of B. anthracis and with cells of strains of B. cereus and B. thuringiensis. The unreactive B. anthracis strains were delta-Vollum-1B-1 and Texas. Encapsulated cells of B. anthracis stained poorly except for small bright regions. Absorption of anti-EA1 with cells of B. cereus NCTC 8035 and NCTC 9946 removed activity towards all B. cereus strains tested, but only partly reduced cross-reaction with B. thuringiensis strains. Absorption of anti-EA1 with B. thuringiensis 4041 removed activity towards this strain and B. cereus strains. Evidence is produced that B. thuringiensis cells grown on nutrient agar possess more cross-reacting antigens than cells grown in nutrient broth. The reaction of anti-EA1 with Bacillus spores immobilized in clumps on microscope slides was attributed to contaminating vegetative debris because well-separated individual spores failed to react. A rapid IF test was developed allowing identification of B. anthracis sampled from overnight cultures on blood plates. When sodium dodecyl sulphate extracts of B. anthracis vegetative cells were analysed on immunoblots (Western blots) by reaction with anti-EA1, a number of bands were visualized in addition to the expected 91 kiloDalton EA1 band. Prior absorption of anti-EA1 with B. cereus or B. thuringiensis cells resulted in the disappearance of most or all of the brands in blots of these species, but had less effect on blots of the B. anthracis strains. All six B. anthracis strains that were blotted including delta-Vollum-1B-1 and Texas, could thus be distinguished from B. cereus and B. thuringiensis by their differential reaction with unabsorbed and absorbed anti-EA1.

Differentiation of Bacillus anthracis and other Bacillus species by lectins

Bacillus anthracis was agglutinated by several lectins, including those from Griffonia simplicifolia, Glycine max, Abrus precatorius, and Ricinus communis. Some strains of Bacillus cereus var. mycoides (B. mycoides) were strongly reactive with the lectin from Helix pomatia and weakly reactive with the G. max lectin. The differential interactions between Bacillus species and lectins afforded a means of distinguishing B. anthracis from other bacilli. B. cereus strains exhibited heterogeneity with respect to agglutination patterns by lectins but could readily be differentiated from B. anthracis and the related B. mycoides. Spores of B. anthracis and B. mycoides retained lectin receptors, although the heating of spores or vegetative cells at 100 degrees C resulted in a decrease in their ability to be specifically agglutinated. Fluorescein-conjugated lectin of G. max stained vegetative cells of B. anthracis uniformly, suggesting that the distribution of lectin receptors was continuous over the entire cellular surface. B. anthracis cells grown under conditions to promote the production of capsular poly(D-glutamyl peptide) were also readily agglutinated by the lectins, suggesting that the lectin reactive sites penetrate the polypeptide layer. Trypsin, subtilisin, lysozyme, and mutanolysin did not modify the reactivity of B. anthracis with the G. max agglutinin, although the same enzymes markedly diminished the interaction between the lectin and B. mycoides. Because the lectins which interact with B. anthracis are specific for alpha-D-galactose or 2-acetamido-2-deoxy-alpha-D-galactose residues, it is likely that the bacteria possess cell surface polymers which contain these sugars. Lectins may prove useful in the laboratory identification of B. anthracis and possibly other pathogenic Bacillus species, such as B. cereus.

Isolation and characterization of three autolytic enzymes associated with sporulation of Bacillus thuringiensis var. thuringiensis

Cells of Bacillus thuringiensis containing refractile spores autolyzed readily when suspended in buffer. The autolysate contained enzymes which lysed vegetative cell walls of the organism. Three enzymes were isolated from the autolysate, and each was purified approximately 30-fold. One enzyme, most active near pH 4.0, was found to be an N-acetylmuramidase. The other two enzymes exhibited pH optima at 8.5. One was stimulated by cobalt ions and the other was not. The cobalt-stimulated enzyme was shown to be an N-acetylmuramyl-l-alanine amidase. The cobalt insensitive enzyme exhibited both N-acetylmuramyl-l-alanine amidase and endopeptidase activity. The amidase activity may reflect incomplete separation of the cobalt-stimulated enzyme. The endopeptidase cleaved the peptide bond between l-alanine d-glutamic acid. A cell wall lytic endopeptidase with this specificity has not been previously reported. All three enzymes were extremely limited in the range of bacterial cell walls which they attacked. Except for cell walls of Micrococcus lysodeikticus, which were lysed by the muramidase, only cell walls of members of the genus Bacillus were attacked.

Differential media for the identification of Bacillus anthracis

Knisely, Ralph F. (U.S. Army Biological Laboratories, Fort Detrick, Frederick, Md.). Differential media for the identification of Bacillus anthracis. J. Bacteriol. 90:1778-1783. 1965.-Two new differential media for the identification of Bacillus anthracis are described. Phenethyl alcohol and chloral hydrate were used as selective ingredients. These media should aid in the differentiation of B. anthracis from B. cereus and, if used in conjunction with other differential tests, they should also differentiate B. anthracis from the majority of other aerobic sporeforming bacilli. These media might also be useful in the classification of Bacillus species.

LETHALITY FOR MICE OF VEGETATIVE AND SPORE FORMS OF BACILLUS CEREUS AND BACILLUS CEREUS -LIKE INSECT PATHOGENS INJECTED INTRAPERITONEALLY AND SUBCUTANEOUSLY

Lamanna, Carl (Army Research Office, Washington, D.C.) and Linda Jones . Lethality for mice of vegetative and spore forms of Bacillus cereus and Bacillus cereus -like insect pathogens injected intraperitoneally and subcutaneously. J. Bacteriol. 85: 532–535. 1963.—Lethality for mice of Bacillus thuringiensis var. thuringiensis (two strains), var. sotto (one strain), var. alesti (one strain), and B. entomocidus var. entomocidus (one strain) maintained on artificial laboratory media is dependent upon the route of injection, the number of the bacilli, and their biological state, i.e., vegetative or spore form. Deaths did not occur upon subcutaneous injection of tenfold greater numbers of organisms than the ld 50 dose for the intraperitoneal route. From 10 to 100 times the number of spores were required to kill than vegetative bacilli given intraperitoneally. These observations duplicated those made with strains of B. cereus . For both types of spore forms, from 5 × 10 5 to 5 × 10 7 vegetative organisms were required for one intraperitoneal ld 50 . With two strains of highly virulent B. anthracis , ld 50 values were the same for the vegetative and spore states, and for subcutaneous and intraperitoneal injections. Thus, the insect pathogenic sporeforming bacteria tested are more like B. cereus than like B. anthracis in their capacity to infect mice. The similarity to B. cereus extends to the rapidity of death after fatal injection of the insect pathogenic strains. The medical and taxonomic implications of the observations are discussed.