Genetic diversity of clinical isolates of Bacillus cereus using multilocus sequence typing

<p>Abstract</p> <p>Background</p> <p><it>Bacillus cereus </it>is most commonly associated with foodborne illness (diarrheal and emetic) but is also an opportunistic pathogen that can cause severe and fatal infections. Several multilocus sequence typing (MLST) schemes have recently been developed to genotype <it>B. cereus </it>and analysis has suggested a clonal or weakly clonal population structure for <it>B. cereus </it>and its close relatives <it>B. anthracis </it>and <it>B. thuringiensis</it>. In this study we used MLST to determine if <it>B. cereus </it>isolates associated with illnesses of varying severity (e.g., severe, systemic vs. gastrointestinal (GI) illness) were clonal or formed clonal complexes.</p> <p>Results</p> <p>A retrospective analysis of 55 clinical <it>B. cereus </it>isolates submitted to the Centers for Disease Control and Prevention between 1954 and 2004 was conducted. Clinical isolates from severe infections (n = 27), gastrointestinal (GI) illness (n = 18), and associated isolates from food (n = 10) were selected for analysis using MLST. The 55 isolates were diverse and comprised 38 sequence types (ST) in two distinct clades. Of the 27 isolates associated with serious illness, 13 clustered in clade 1 while 14 were in clade 2. Isolates associated with GI illness were also found throughout clades 1 and 2, while no isolates in this study belonged to clade 3. All the isolates from this study belonging to the clade 1/cereus III lineage were associated with severe disease while isolates belonging to clade1/cereus II contained isolates primarily associated with severe disease and emetic illness. Only three STs were observed more than once for epidemiologically distinct isolates.</p> <p>Conclusion</p> <p>STs of clinical <it>B. cereus </it>isolates were phylogenetically diverse and distributed among two of three previously described clades. Greater numbers of strains will need to be analyzed to confirm if specific lineages or clonal complexes are more likely to contain clinical isolates or be associated with specific illness, similar to <it>B. anthracis </it>and emetic <it>B. cereus </it>isolates.</p

Characterization of Burkholderia rhizoxinica and B. endofungorum Isolated from Clinical Specimens

Eight isolates submitted to CDC from 1989 to 2006 from clinical specimens were initially identified as members of the genus Burkholderia based on preliminary cellular fatty acid analysis and/or 16S rRNA gene sequencing. With the recent descriptions of the new species B. rhizoxinica and B. endofungorum, which are considered endosymbiotic bacteria in Rhizopus microsporus fungi, we now identify seven of these clinical isolates as B. rhizoxinica and one as B. endofungorum based on biochemical testing, 16s rRNA, and DNA-DNA hybridization results. We also further characterize these isolates by assessing toxin production and/or by multiple locus sequence typing

Novel Brucella Strain (BO1) Associated with a Prosthetic Breast Implant Infection▿

We report the microbiological, biochemical, and molecular characterization of an unusual Brucella strain (BO1) isolated from a breast implant wound in a 71-year-old woman with clinical symptoms consistent with brucellosis. Initial phenotypic analysis, including biochemical and antimicrobial susceptibility testing, cellular fatty acid analysis, and molecular analysis based on DNA-DNA reassociation and the presence of multiple copies of IS711 element suggested that the isolate was a Brucella-like organism, but species determination using microbiological algorithms was unsuccessful. Furthermore, molecular data based on 16S rRNA gene sequencing and multilocus sequence analysis demonstrated that BO1 was an unusual Brucella strain and not closely related to any currently described Brucella species. However, comparison with equivalent sequences in Ochrobactrum spp. confirms that the isolate is much more closely related to Brucella than to Ochrobactrum spp., and thus the isolate likely represents an atypical and novel strain within the genus Brucella

Identification of Some Charcoal-Black-Pigmented CDC Fermentative Coryneform Group 4 Isolates as Rothia dentocariosa and Some as Corynebacterium aurimucosum: Proposal of Rothia dentocariosa emend. Georg and Brown 1967, Corynebacterium aurimucosum emend. Yassin et al. 2002, and Corynebacterium nigricans Shukla et al. 2003 pro synon. Corynebacterium aurimucosum

Sixty-three clinical isolates of charcoal-black-pigmented, gram-positive coryneform rods were received for identification by the Centers for Disease Control and Prevention (CDC) and were provisionally designated CDC fermentative coryneform group 4 (FCG4). Forty-five of these were characterized by morphological, physiologic, antimicrobial susceptibility, cellular fatty acids, 16S rRNA gene sequencing, and DNA-DNA hybridization analyses. Nitrate reduction, cellular fatty acid analysis, 16S rRNA gene sequencing, and DNA-DNA hybridization studies segregated these strains into two groups: FCG4a (8 strains) and FCG4b (37 strains). The FCG4a strains, only one of which was from a female genitourinary source, produced cellular fatty acid and biochemical profiles similar to those observed with reference strains of Rothia dentocariosa and Rothia mucilaginosa, while the FCG4b strains were similar to Corynebacterium species. DNA-DNA hybridization analysis demonstrated species-level relatedness among six FCG4a tested strains and showed that they were a charcoal-black-pigmented variant of R. dentocariosa. Sixteen isolates of the FCG4b group, mainly from female genitourinary tract specimens, as well as the type strains of two recently named species, Corynebacterium aurimucosum and Corynebacterium nigricans, were shown by DNA-DNA hybridization analysis and the sequencing of the 16S rRNA gene to be related at the species level and unrelated to the type strain of R. dentocariosa; therefore, the Corynebacterium-like strains were classified as a charcoal-black-pigmented variant of C. aurimucosum, because this name has nomenclatural priority over C. nigricans. These findings indicate that FCG4 represents a heterogeneous group that contains pigmented variants of both R. dentocariosa and C. aurimucosum; hence, the descriptions of both R. dentocariosa and C. aurimucosum have been amended to include charcoal-black-pigmented variants, and C. nigricans is a pro synonym of C. aurimucosum

Specific, Sensitive, and Quantitative Enzyme-Linked Immunosorbent Assay for Human Immunoglobulin G Antibodies to Anthrax Toxin Protective Antigen

The bioterrorism-associated human anthrax epidemic in the fall of 2001 highlighted the need for a sensitive, reproducible, and specific laboratory test for the confirmatory diagnosis of human anthrax. The Centers for Disease Control and Prevention developed, optimized, and rapidly qualified an enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G (IgG) antibodies to Bacillus anthracis protective antigen (PA) in human serum. The qualified ELISA had a minimum detection limit of 0.06 µg/mL, a reliable lower limit of detection of 0.09 µg/mL, and a lower limit of quantification in undiluted serum specimens of 3.0 µg/mL anti-PA IgG. The diagnostic sensitivity of the assay was 97.8%, and the diagnostic specificity was 94.2%. A competitive inhibition anti-PA IgG ELISA was also developed to enhance diagnostic specificity to 100%. The anti-PA ELISAs proved valuable for the confirmation of cases of cutaneous and inhalational anthrax and evaluation of patients in whom the diagnosis of anthrax was being considered