Environmental survey for four pathogenic bacteria and closely related species using phylogenetic and functional genes

Bacterial species with high DNA sequence similarity to pathogens could affect the specificity of assays designed to detect biological threat agents in environmental samples. The natural presence of four pathogenic bacteria, Bacillus anthracis, Clostridium perfringens, Francisella tularensis, and Yersinia pestis and their closely related species, was determined for a large collection of soil and aerosol samples. Polymerase chain reaction (PCR) and gene sequencing were used using group-specific 16S rRNA primers to identify pathogens and related species, and pathogen-specific virulence genes. Close relatives of B. anthracis (B. cereus group species) were detected in 37% of the soils and 25% of the aerosol samples. The B. anthracis protective antigen (pag) gene or a close homolog was detected in 16 of these samples. For the other three pathogen groups, the frequency of detection was much lower, and none of the samples were positive with both the phylogenetic and virulence gene primer sets.     

Death caused by neglect?

Over a period of several months a 23-year-old bedridden woman suffered from increasing cachexia with numerous decubital ulcera in the parental house. The parents induced the hospitalization not before the patient reached the agonal phase. The reported case was especially spectacular because the left arm had fallen off and lay beside the woman showing maggot infestation, mummification and skeletonization. Against the parents a preliminary investigation for manslaughter by negligence was instituted. This case report describes the unusual course of disease and the striking familiar situation.     

Composition of bacillus species in aerosols from 11 U.S. cities

A PCR-based heteroduplex assay was used to determine the presence and composition of Bacillus species in 11,059 Environmental Protection Agency PM2.5 aerosol samples from 11 U.S. cities. The assay differentiated three groups: Type A containing Bacillus anthracis and very closely related, often pathogenic, Bacillus cereus and Bacillus thuringiensis strains; Type B containing other B. cereus and B. thuringiensis strains; and a third group of more-distantly related Bacillus species. Eight of the 11 cities were positive for Bacillus species in 50% or more of the samples, and the percent of aerosol samples that contained the HD Type A group ranged from 3% to 32%. Cities from the eastern half of the United States generally contained a higher frequency and broader diversity of Bacillus species than the western half of the United States. Positive samples were detected throughout the year. These results have implications for pathogen detection in environmental samples, understanding the natural evolution of new pathogenic strains, and incidence of infection caused by strains of the B. cereus subgroup.