Bacillus cereus and related species

A novel sensitive bioassay for detection of Bacillus cereus emetic toxin and related depsipeptide ionophores

Of the toxins produced by Bacillus cereus, the emetic toxin is likely the most dangerous but, due to the lack of a suitable assay, the least well known. In this paper, a new, sensitive, inexpensive, and rapid bioassay for detection of the emetic toxin of B. cereus is described. The assay is based on the loss of motility of boar spermatozoa upon 24 h of exposure to extracts of emetic B. cereus strains or contaminated food. The paralyzed spermatozoa exhibited swollen mitochondria, but no depletion of cellular ATP or damage to plasma membrane integrity was observed. Analysis of the purified toxin by electrospray tandem mass spectrometry showed that it was a dodecadepsipeptide with a mass fragmentation pattern similar to that described for cereulide. The 50% effective concentration of the purified toxin to boar spermatozoa was 0.5 ng of purified toxin ml of extended boar semen-1. This amount corresponds to 10(4) to 10(5) CFU of B. cereus cells. No toxicity was detected for 27 other B. cereus strains up to 10(8) CFU ml-1. The detection limit for food was 3 g of rice containing 10(6) to 10(7) CFU of emetic B. cereus per gram. Effects similar to those provoked by emetic B. cereus toxin were also induced in boar spermatozoa by valinomycin and gramicidin at 2 and 3 ng ml of extended boar semen-1, respectively. The symptoms provoked by the toxin in spermatozoa indicated that B. cereus emetic toxin was acting as a membrane channel-forming ionophore, damaging mitochondria and blocking the oxidative phosphorylation required for the motility of boar spermatozoa.

Growth and enterotoxin production by diarrhoeagenic Bacillus cereus in dietary supplements prepared for hospitalized HIV patients

This study was initiated because of an increase in diarrhoeal episodes in a ward caring for patients infected with the human immunodeficiency virus (HIV). An examination of hospital-prepared dietary supplements (build-up food) found Bacillus cereus to be a potential problem. Due in part to inadequate refrigeration conditions (13 +/- 4 degrees C), the microbial flora in commercially pasteurized semi-skimmed milk (PSSM) reached potentially hazardous levels (> 10(6) cfu/mL). While refrigerated PSSM did not support enterotoxin production, reconstitution of build-up powder in PSSM followed by storage in the HIV ward (4 h at 28 +/- 3 degrees C) resulted in growth of B. cereus (> 10(7) cfu/mL) and synthesis of diarrhoeal enterotoxin. While insufficient epidemiological data was available to establish conclusively a causal relationship between patients' symptoms and source, the study highlights a potential B. cereus problem with hospital-prepared dietary supplements and recommendations are proposed to prevent this re-occurrence.

Epidemic Bacillus endophthalmitis after cataract surgery I: acute presentation and outcome

OBJECTIVE

The purpose of the study is to report the clinical outcome of acute Bacillus endophthalmitis after cataract surgery.

DESIGN

The study design is a cohort study.

PARTICIPANTS

Fourteen eyes of 14 patients with epidemic acute postoperative inflammation after exposure to bacteria-contaminated viscoelastic material were studied.

INTERVENTION

Three patients with milder clinical presentations were treated without vitrectomy or antibiotics. Eleven patients with more severe infection were treated with vitrectomy as well as intravitreous and topical fortified antibiotics.

MAIN OUTCOME MEASURES

Final visual acuities were obtained in all 14 study patients. Results of microbiologic studies of aqueous and vitreous specimens from 11 vitrectomized eyes also were analyzed.

RESULTS

One patient with late presentation had severe inflammation and had phthisis bulbi develop with no light perception. The remaining 13 patients had successful resolution of inflammation after treatment by 1 month of follow-up. Twelve of these 13 patients, including 1 nonvitrectomized patient, had final visual acuities of 20/100 or better at 6 months' follow-up. Six patients, including two patients with nonvitrectomized eyes, had outcomes of 20/40 or better visual acuity. Bacillus species were grown from all 11 (100%) vitreous and 7 (88%) of 8 aqueous specimens obtained from vitrectomized patients, as well as from the contaminated viscoelastic material remaining in the operating room.

CONCLUSIONS

Postoperative Bacillus endophthalmitis need not result in poor outcome. Results depend on factors including bacterial load, specific bacterial species, timing of treatment, and immune status of the patient.

Use of pulsed-field gel electrophoresis to investigate a pseudo-outbreak of Bacillus cereus in a pediatric unit

Bacillus cereus is a well-known cause of food poisoning. It also causes rare systemic infections, usually in immunocompromised patients. Dissemination of this species in hospitals had been reported. Most of these episodes were pseudo-outbreaks and were usually secondary to equipment or environmental contamination. We report here on the use of pulsed-field gel electrophoresis (PFGE) to analyze a pseudo-outbreak of B. cereus in a pediatric unit. Different restriction endonucleases had been tested, and SmaI was found to give the best result for PFGE. Among the 26 clinical isolates of B. cereus and the type strain of the species, 15 distinct PFGE patterns were distinguished. PFGE after DNA macrorestriction with SmaI could clearly differentiate between the epidemiologically related isolates and the unrelated isolates. Because the same epidemic strain of B. cereus was isolated from the settle plates which were exposed near the outlet of the ventilation system, the source of this pseudo-outbreak was suspected to be the unit's air filtration system. This is one of the first reports of the application of PFGE to the study of B. cereus, and this method is useful for epidemiological investigation.

Characterization of Bacillus thuringiensis isolated from infections in burn wounds

Four strains of Bacillus thuringiensis were isolated from infections in burn wounds and from water used in the treatment of burn wounds. The strains produced large parasporal inclusion bodies composed of 141, 83, and 81 kDa protoxins. The four strains were tested for insecticidal activity against larvae of Pieris brassicae and Aedes aegypti but showed no activity; Vero cell assays for the production of enterotoxins were also negative. Attempts to classify the strains according to flagellar H-serotype showed them all to be non-flagellated. Apart from two occupational health accidents that occurred during the handling of highly concentrated B. thuringiensis fluids, this is the first report of B. thuringiensis causing non-gastrointestinal clinical infection in immunosuppressed patients.

Molecular evolution and diversity in Bacillus anthracis as detected by amplified fragment length polymorphism markers

Bacillus anthracis causes anthrax and represents one of the most molecularly monomorphic bacteria known. We have used AFLP (amplified fragment length polymorphism) DNA markers to analyze 78 B. anthracis isolates and six related Bacillus species for molecular variation. AFLP markers are extremely sensitive to even small sequence variation, using PCR and high-resolution electrophoresis to examine restriction fragments. Using this approach, we examined ca. 6.3% of the Bacillus genome for length mutations and ca. 0.36% for point mutations. Extensive variation was observed among taxa, and both cladistic and phenetic analyses were used to construct a phylogeny of B. anthracis and its closest relatives. This genome-wide analysis of 357 AFLP characters (polymorphic fragments) indicates that B. cereus and B. thuringiensis are the closest taxa to B. anthracis, with B. mycoides slightly more distant. B. subtilis, B. polymyxa, and B. stearothermophilus shared few AFLP markers with B. anthracis and were used as outgroups to root the analysis. In contrast to the variation among taxa, only rare AFLP marker variation was observed within B. anthracis, which may be the most genetically uniform bacterial species known. However, AFLP markers did establish the presence or absence of the pXO1 and pXO2 plasmids and detected 31 polymorphic chromosomal regions among the 79 B. anthracis isolates. Cluster analysis identified two very distinct genetic lineages among the B. anthracis isolates. The level of variation and its geographic distribution are consistent with a historically recent African origin for this pathogenic organism. Based on AFLP marker similarity, the ongoing anthrax epidemic in Canada and the northern United States is due to a single strain introduction that has remained stable over at least 30 years and a 1,000-mile distribution.

Fulminating bacteremia and pneumonia due to Bacillus cereus

We present two cases of rapidly progressing, fatal pneumonia caused by Bacillus cereus. These cases are interesting in that B. cereus, even from blood or sputum specimens, may often be considered a contaminant and receive inadequate attention. Also of interest was the fact that the two patients resided in the same area of the state, were welders by trade, and became ill within a few days of each other, yet there was no epidemiologic link between them.

Host/parasite interactions in bacterial endophthalmitis

Bacterial infections within the eye arise as complications of intraocular surgery, penetrating injury, or hematogenous spread from distant anatomical sites. Because: 1) the interior surfaces of the eye are lined with sensitive, nonregenerating tissues, 2) the inner chambers of the eye are relatively sequestered from circulating immunological components, 3) the integrity of blood-ocular barriers provides poor penetration of systemically administered antibiotics, and 4) aqueous and vitreous humor represent rich, relatively acellular culture media; endophthalmitis often progresses rapidly and total loss of vision frequently results. Years of clinical experience have shown that current therapies for endophthalmitis, including antimicrobials, antiinflammatory agents, and vitrectomy, are frequently unsuccessful in ameliorating destruction of intraocular tissues. While bacterial and host factors were thought to play key roles in the course and severity of endophthalmitis, it is only recently that their contributions have been experimentally defined. Molecular-based techniques are gaining increased use in the study of infectious eye diseases. Current findings regarding the host/parasite interactions within the eye are reviewed, and a resulting integrative model of the natural course of endophthalmitis proposed. A molecular-level understanding of the roles of both bacterial and host factors during endophthalmitis will likely reveal potential targets for therapeutic intervention aimed at salvaging vision.

Discrimination between Bacillus cereus and Bacillus thuringiensis using specific DNA probes based on variable regions of 16S rRNA

Identification of Bacillus cereus and differentiation between B. cereus and closely related species are currently based on biochemical tests. The main problem is to discriminate between B. cereus and B. thuringiensis. Sequencing part of the 16S rRNA showed that several B. cereus isolates present in food and involved in food poisoning, confirmed according to the classical biochemical methods, were in fact B. thuringiensis. As this organism is the most commonly used microbial insecticide worldwide, the results of this study emphasize the need for accurate identification methods and for careful screening of strains for use as insecticides. Therefore, specific DNA probes based on the variable region VI of 16S rRNA of B. cereus and B. thuringiensis were designed. The probes were used in hybridization experiments with the variable region amplified using the polymerase chain reaction. In this way, a rapid and sensitive method was developed to distinguish B. cereus and B. thuringiensis.

Time to B. cereus about hot chocolate

OBJECTIVE

To determine the cause of illnesses experienced by employees of a Minneapolis manufacturing plant after drinking hot chocolate bought from a vending machine and to explore the prevalence of similar vending machine-related illnesses.

METHODS

The authors inspected the vending machines at the manufacturing plant where employees reported illnesses and at other locations in the city where hot chocolate beverages were sold in machines. Tests were performed on dry mix, water, and beverage samples and on machine parts.

RESULTS

Laboratory analyses confirmed the presence of B. cereus in dispensed beverages at a concentration capable of causing illness (170,000 count/gm). In citywide testing of vending machines dispensing hot chocolate, 7 of the 39 licensed machines were found to be contaminated, with two contaminated machines having B. cereus levels capable of causing illness.

CONCLUSIONS

Hot chocolate sold in vending machines may contain organisms capable of producing toxins that under favorable conditions, can induce illness. Such illnesses are likely to be underreported. Even low concentrations of B. cereus may be dangerous for vulnerable populations such as the aged or immunosuppressed. Periodic testing of vending machines is thus warranted. The relationship between cleaning practices and B. cereus contamination is an issue for further study.

Is the exploding powder gas of the propellant from blank cartridges sterile?

Shots from blank weapons loaded with blank cartridges, when fired from close range or as a contact shot, almost always cause the skin to burst open and lead to injuries to structures below the surface. Subsequently, wound infections are often observed. In addition to the introduction of skin germs, the possibility exists that contaminated propellants may enter into consideration as a source of infection. Using step-by-step experimental procedures we were able to demonstrate that: 1. Blank cartridge propellants were almost always contaminated with Bacillus cereus (nitrocellulose powder more so than black powder); 2. When the shot is fired numerous bacteria survive and are forced out with the gunsmoke from the weapon and thus find their way into the wound. In principle, blank cartridge propellant thus exhibits as much potential for wound infection as the skin germs. Clearly, the species B. cereus is prominent in this context. For open injuries even with 'harmless' blank weapons, an antibiotic prophylaxis should always be administered.

The emergency department approach to diarrhea

Enteric disease represents a significant medical problem on a worldwide basis. The evaluation of patients with diarrhea in the emergency department should follow a stepwise methodology to identify potentially serious disorders. The evaluation of the stool for fecal leukocytes is an important differentiation point in the evaluation of the moderately to seriously ill diarrhea patient. Oral rehydration alone can treat the vast majority of diarrhea patients. Oral rehydration solution takes advantage of the sodium glucose coupled active absorption mechanism, which is largely unaffected by enteric toxins. Antimicrobial or antidiarrheal agents are rarely indicated in the treatment of diarrhea.

Bacterial contaminants in liquid packaging boards: assessment of potential for food spoilage

Liquid packaging boards and blanks were examined for microbial contaminants. A total of 218 strains were identified and representatives of the most frequent species were characterized for their potential for food spoilage. Contaminants found were aerobic spore-forming bacteria, mostly Bacillus megaterium, B. licheniformis, B. cereus group, B. pumilus, Paenibacillus macerans, P. polymyxa, P. pabuli and B. flexus. Production of amylolytic, proteolytic, lipolytic and phospholipolytic enzymes was common. Approximately 50% of the B. cereus group strains were positive in the diarrhoeal enterotoxin immunoassay test or in the enterotoxin reversed passive latex agglutination test. Strains capable of growth at 6 degrees C were found among B. cereus group, P. pabuli, P. validus, B. megaterium and P. polymyxa. All b. licheniformis strains grew at 55 degrees C. The spores of B. licheniformis were most resistant to hydrogen peroxide. The B. cereus group strains were recognizable by fatty acid components not present in any of the other paperboard strains, 11-methyldodecanoic acid (13:0 iso) and trans-9-hexadecenoic acid (16:1 omega 7 trans), each contributing 7% or more to the total cellular fatty acids.

Infection with Bacillus cereus after close-range gunshot injuries

Three patients were admitted with close-range gunshot wounds of the knee and lower leg, inflicted in all three cases through clothing. At admission, all of the patients were given antibiotics (cefuroxime and metronidazole) to prevent streptococcal and anaerobic infection. All of the patients developed severe tissue infection with Bacillus cereus within days of admission. In one case, the organism was also recovered from the blood. B. cereus is capable of causing severe infection after trauma and its ubiquity in the environment allows it easy access to gunshot wounds. Its potent production of beta-lactamase renders penicillins and cephalosporins predictably ineffective. The early administration of a non-beta-lactam drug (such as ciprofloxacin) should be considered in cases where Bacillus cereus is isolated from traumatic wounds.

Randomly amplified polymorphic DNA (RAPD) assay for genomic fingerprinting of Bacillus cereus isolates

Randomly amplified polymorphic DNA (RAPD) assay was used for epidemiological subtyping of B. cereus and B. lentus. Within 25 isolates of B. cereus up to 22 strain types could be determined when five primers were used. RAPD patterns, which were found in three B. lentus strains, clearly differed form those of B. cereus. The RAPD technique proved to be an effective tool for the characterization of B. cereus strains.

The chromosome map of Bacillus thuringiensis subsp. canadensis HD224 is highly similar to that of the Bacillus cereus type strain ATCC 14579

A physical map of the Bacillus thuringiensis subsp. canadensis HD224 chromosome based on AscI, NotI, and SfiI restriction sites has been established. The chromosome map of 4.3 Mb was similar to a revised map of the chromosome of the B. cereus type strain ATCC 14579, except that the B. thuringiensis subsp. canadensis HD224 chromosome lacked a NotI site and had two additional AscI sites. The positions of 27 probes were identical in the common macromap. A probe for the insecticidal toxin gene, cryIA, hybridized only to the B. thuringiensis subsp. canadensis HD224 chromosome. The BssHII ribotype patterns were almost identical confirming the similarity between the two strains.

Useful visual outcomes after treatment of Bacillus cereus endophthalmitis

PURPOSE

Bacillus cereus endophthalmitis occurring after penetrating ocular trauma has been almost always associated with a poor visual outcome. The purpose of our study was to review and report patients who had useful visual acuity outcomes.

METHODS

The study group consisted of five patients from a single medical center with penetrating ocular trauma and endophthalmitis caused by B. cereus. The study population was derived from a review of the microbiology records, clinical records, and operative reports of patients with culture-proven, post-traumatic endophthalmitis over a 15-year period. Patients were only included if the final visual acuity outcomes were 20/200 or better.

RESULTS

All five patients had penetrating ocular injuries, and four patients had a retained intraocular foreign body. Endophthalmitis was diagnosed preoperatively in three patients and intraoperatively in two patients. All patients underwent pars plana vitrectomy and injection of intravitreal and periocular antibiotics. Postoperatively, a rhegmatogenous retinal detachment developed in three patients between 4 weeks and 12 months after the injury (average, 19 weeks); all retinal detachments were reattached with additional vitreoretinal surgery. Final postoperative visual acuities were 20/200 (two patients), 20/30 (one patient), and 20/25 (two patients). The postoperative follow-up time interval ranged from 12 months to 30 months (average, 19.2 months).

CONCLUSION

The current series adds further support to the observation that certain eyes with post-traumatic B. cereus endophthalmitis may be associated with preservation of anatomic integrity and restoration of useful visual acuity.

Recovery of uncommon bacteria from blood: association with neoplastic disease

Table 6 is a summary of the organisms discussed with a listing of the environmental source, the endogenous source, the predisposing factors including neoplasms, and the postulated mechanisms by which the organism can gain access to the circulation. The evidence considered indicates that the entrance of one of these microorganisms into the bloodstream of a human being depends on the presence of multiplicity of predisposing factors. In the majority of cases of bacteremia due to one of these unusual organisms, two or more predisposing factors are present. Certain predisposing factors, such as cancer chemotherapy or intravenous catheterization, often provide a barrier break, while others, such as liver disease, may render the host immune system less capable of clearing organisms from the circulation. For organisms such as Campy-lobacter, Listeria, and Salmonella spp., attributes that allow the invasion of a healthy host are present and seem to be enhanced by the simultaneous presence of a predisposing condition, such as liver disease, in the host. Although somewhat fragmentary, a number of individual case reports describe bacteremia due to one of these organisms occurring weeks to years after surgery and after other therapeutic measures had effected a supposed cure of a cancer. It may be speculated that cancer patients, even after a cure, are still susceptible to bloodstream invasion by one of the aforementioned organisms by virtue of the presence of one or more predisposing metabolic, physiologic, or immunologic factors, even though these factors may be cryptic. The predominance of hematologic malignancies among cases of bacteremia due to these unusual organisms is also apparent. Although, as pointed out by Keusch (169), the reduction in the performance of immune function in hematologic malignancies compared with solid tumors is likely to be responsible, other associations of certain organisms with specific neoplasms warrant further examination. The frequency of bloodstream infections of Salmonella typhimurium and Capno-cytophaga canimorsus in Hodgkin's disease patients seems likely due to a particular mechanism which infection by these species is favored. The specific nature of these mechanisms remains to be determined. The recovery of any unusual bacterium from blood should warrant a careful consideration of the possibility of underlying disease, especially cancer. Microbiologists should advise clinicians of the unusual nature of the identified organism and provide the counsel that certain neoplastic processes, often accompanied by neutropenia, render the human host susceptible to invasion by almost any bacterium. The recovery of such organisms as C. septicum or S. bovis should prompt the clinician to aggressively seek to identify an occult neoplasm if one has not yet been diagnosed.

Genetic variability of Bacillus anthracis and related species

We evaluated the abilities of pulsed-field gel electrophoresis (PFGE) and sequences of intergenic spacer regions (ISRs) between two highly conserved genes, 16S-23S rDNA and gyrB-gyrA ISRs, to detect variation in strains of Bacillus anthracis as well as two closely related species, B. cereus ATCC 14579 and B. mycoides ATCC 6462. For each restriction enzyme, (NotI, SfiI, and SmaI), the PFGE banding patterns for three B. anthracis strains (Ames, Vollum, and Sterne) were identical. However, closely related species could be differentiated from B. anthracis and from each other. PCR amplification of the 16S-23S rDNA ISR yielded a 143- to 144-bp fragment, showing identical sequences for B. anthracis strains, one nucleotide deletion between B. cerus and B. anthracis, and 13 nucleotide differences between B. mycoides and B. anthracis. The gyrase ISR sequences (121 bp) in B. anthracis strains were also identical, but those in B. cereus and B. mycoides differed from that in B. anthracis by 1 and 2 nucleotides, respectively, and from each other by only 1 nucleotide. Given the diverse geographic origins of these B. anthracis strains, this species is very homogenous. We conclude that methods such as PFGE and sequences of ISRs may be useful in separating B. anthracis from closely related species, but more sensitive methods are needed for strain identification of B. anthracis.

A retrospective study of bovine abortions associated with Bacillus licheniformis

A retrospective study of bovine abortions associated with Bacillus licheniformis is described. The material consisted of 2445 bovine abortions submitted for diagnostics from 1986 through 1993. Initially, B. licheniformis had been isolated from 81 cases. Sections of these cases were re-examined microscopically and immunohistochemically by a PAP technique using a primary antibody against B. licheniformis. Of these abortions, 47 were most likely associated with B. licheniformis as tissue lesions with immunostained bacteria were present in these. In the remaining cases the diagnosis may not have been established due to the lack of sufficient materials, or the isolation of the bacterium was considered to be a result of contamination. In four cases concomitant infections with B. licheniformis and bovine virus diarrhoea virus were present. Abortions caused by B. licheniformis were predominantly seen during the winter months and in late pregnancy. The most common lesions were necrotizing placentitis followed by fetal multifocal suppurative bronchopneumonia. Immunohistochemically, B. licheniformis was demonstrated in association with tissue lesions and intracellularly in trophoblasts. The pattern of bacterial isolations, especially from the placenta, lungs, and abomasal contents, combined with the histological findings points to B. licheniformis abortions as being of haematogenous origin with subsequent transplacental spread to the fetus.

Experimental infection in mice with Bacillus licheniformis

The pathogenicity of Bacillus licheniformis was assessed in normal and immunodepressed BALB/c mice. The animals were challenged intravenously with 4 x 10(7) colony forming units of B. licheniformis (ATCC 14580) and both normal and immunodepressed mice were susceptible. However, the infection was more severe in the immunosuppressed animals. In normal mice, lesions were restricted to the liver and kidneys, while lesions also occurred in other organs of immunodepressed mice. By crossed immunoelectrophoresis it was shown that antigens of B. licheniformis are potent immunogens, and the bacteria could be identified in tissue sections by immunostaining. Immunohistochemically, B. licheniformis was demonstrated in hepatic and pulmonic macrophages, and from some animals the bacteria were also reisolated.

Bacillus cereus phage typing as an epidemiological tool in outbreaks of food poisoning

Bacillus cereus is responsible for an increasing number of food poisoning cases. By using 12 bacteriophages isolated from sewage, a typing scheme for B. cereus isolates from outbreaks or sporadic cases of food poisoning was developed. The phages belonged to three morphotypes. Ten phages with contractile tails and icosahedral heads were members of the Myoviridae family, and two phages with noncontractile tails belonged to the Siphoviridae family. Phage 11 represented a new species. It had an isometric head and a very long contractile tail with long wavy tail fibers and was one of the largest viruses known. The vast majority of 166 B. cereus strains (161, or 97%) isolated from food poisoning cases were typeable. Of 146 strains isolated from 18 outbreaks, 142 (97%) could be divided into 17 phage types. A good correlation, on the order of 80 to 100%, between phage types of strains isolated from suspected foods and those of strains isolated from stools of symptomatic patients was observed. Most Bacillus thuringiensis strains were also typeable, providing further evidence of the close relatedness of B. cereus and B. thuringiensis. This phage typing scheme can be a valuable epidemiological tool in tracing the origins of food poisoning caused by B. cereus.