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[Additional studies of the pathogenicity of aerobic spore-forming organisms (genus Bacillus) for mice]
Abstract:
An investigation of the parenteral pathogenic potential of aerobic spore-forming bacteria (genus Bacillus) in mice revealed that in the case of i.p. inoculation (0.5 ml suspension, 10(6)-10(7) viable cells per ml) only B. cereus was pathogenic, killing appr. one half of the inoculated animals (293 out of 577). Other bacilli (B. subtilis, B. megaterium, B. pumilus etc.) administered intraperitoneally did not produce any lethal effect. If inoculated intracerebrally, B. cereus killed appr. 90% of the mice (138 out of 155), while for other bacilli the rate was appr. 50% only (260 out of 529). It is suggested that most of the aerobic spore-forming organisms cultured from cases of hospital infections are B. cereus which, however, does not completely exclude the presence of other species.
Insights
Bacillus cereus is pathogenic in mice via parenteral inoculation, causing significant mortality. Other Bacillus species show lower pathogenicity, suggesting B. cereus is a key pathogen in hospital-acquired infections.
Area of Science:
- Microbiology
- Pathogen Discovery
Background:
- Aerobic spore-forming bacteria, particularly the Bacillus genus, are common environmental and hospital contaminants.
- Understanding the pathogenic potential of different Bacillus species is crucial for infection control.
Purpose of the Study:
- To investigate the parenteral pathogenic potential of common aerobic spore-forming bacteria (Bacillus species) in a murine model.
- To differentiate the pathogenicity of Bacillus cereus from other Bacillus species following different inoculation routes.
Main Methods:
- Intraperitoneal (i.p.) and intracerebral inoculation of mice with standardized viable cell concentrations (10^6-10^7 cells/ml) of various Bacillus species.
- Monitoring and recording mortality rates in inoculated animal groups.
- Statistical analysis of survival data to determine significant differences in pathogenicity.
Main Results:
- Bacillus cereus demonstrated significant pathogenicity via i.p. inoculation, causing approximately 50% mortality (293/577 mice).
- Intracerebral inoculation with Bacillus cereus resulted in a higher mortality rate of approximately 90% (138/155 mice).
- Other Bacillus species (e.g., B. subtilis, B. megaterium, B. pumilus) exhibited markedly lower pathogenicity, with mortality rates around 50% for intracerebral inoculation and no lethal effect for i.p. inoculation.
Conclusions:
- Bacillus cereus is the primary pathogenic species among the investigated aerobic spore-forming bacteria in the parenteral mouse model.
- The findings suggest that Bacillus cereus is likely the predominant Bacillus species implicated in hospital-acquired infections.
- While B. cereus is the main concern, the presence of other pathogenic Bacillus species cannot be entirely ruled out.