Biomedical subjects

M John Albert

Publications and source records attributed to M John Albert.

22 records · Page 2Linked to original sources

PubMed2002

Aeromonas hydrophila subsp. dhakensis subsp. nov., isolated from children with diarrhoea in Bangladesh, and extended description of Aeromonas hydrophila subsp. hydrophila (Chester 1901) Stanier 1943 (approved lists 1980).

A group of 10 Aeromonas hydrophila-like strains referred to as group BD-2, which mainly comprised haemolytic and cytotoxic isolates from diarrhoeal children in Bangladesh, was subjected to a polyphasic taxonomic study including fluorescent amplified fragment length polymorphism (FAFLP) and ERIC-PCR fingerprinting, microplate DNA-DNA hybridization and extensive phenotypic characterization. Comparison of FAFLP and ERIC-PCR genotypic profiles indicated that the group BD-2 isolates constituted a separate taxon that was most closely related to A. hydrophila DNA hybridization group (HG) 1. Determination of DNA-DNA hybridization values with type and reference strains of all known Aeromonas taxa revealed that the BD-2 group represented a homogeneous taxon (internal DNA homology, 77-94%) that exhibited 78-92% DNA relatedness with the type strain of A. hydrophila HG1. These results indicated that the BD-2 group belongs genotypically to A. hydrophila HG1, but examination of 152 phenotypic characteristics revealed that the group BD-2 isolates differed from representatives of HG1 in eight biochemical properties. The diagnostic value of at least three of these tests, namely utilization of urocanic acid and L-arabinose and acid production from L-arabinose, has been confirmed outside this study by other workers. Collectively, the genotypic and phenotypic data reported suggest that the BD-2 group represents a subspecies of A. hydrophila, for which the name Aeromonas hydrophila subsp. dhakensis subsp. nov. is proposed. Its type strain is P21T (= LMG 19562T= CCUG 45377T). An extended description of A. hydrophila subsp. hydrophila (Chester 1901) Stanier 1943 (Approved Lists 1980) is given.

Aeromonas hydrophila↗

PubMed2002

TnphoA mutants of Providencia alcalifaciens with altered invasiveness of HEp-2 cells.

Recent studies have shown that Providencia alcalifaciens is a diarrhoeal pathogen. It may cause diarrhoea by an invasive mechanism, as it invades cultured mammalian cells in vitro and intestinal epithelial cells of experimentally inoculated rabbits in vivo. To locate the gene(s) involved in invasion, TnphoA mutants of a diarrhoeal isolate of P. alcalifaciens were generated. Compared with the parent strain, these mutants exhibited negligible invasion and actin condensation in HEp-2 cells. TnphoA insertion was located in fragments of 4.9 kb and 11.1 kb of the bacterial chromosome by Southern blot. These mutants did not secrete a 28-kDa protein, which may be involved in invasion. It should be possible now to study the gene(s) involved in invasion of P. alcalifaciens with these mutants. This investigation is another example of the usefulness of TnphoA mutagenesis in the study of bacterial virulence genes.

Alkaline Phosphatase↗

PubMed1999

Cross-reaction between a strain of Vibrio mimicus and V. cholerae O139 Bengal.

Of 200 isolates of Vibrio mimicus screened, one from water (N-57) agglutinated with V. cholerae O139 polyclonal antiserum (absorbed with a rough strain of V. cholerae only) and not with O139 polyclonal diagnostic antiserum (absorbed with the rough strain and V. cholerae O22 and O155). The antigenic relationship between V. cholerae 0139 and N-57 is of a,b-a,c type, where a is the common antigenic epitope and b and c are unique epitopes. Strain N-57 was assigned to a new serogroup of V. cholerae O194. It gave negative results in a monoclonal antibody-based rapid test and a PCR test specific for V. cholerae O139. It did not possess the ctx gene or produce cholera toxin. Antiserum to strain N-57 cross-protected infant mice against cholera on challenge with V. cholerae O139. Structural studies of the surface polysaccharides and studies of the rfb genes will shed more light on the extent of relatedness between V. mimicus N-57 and V. cholerae O139.

Agglutination Tests↗

PubMed1996

Aeromonas trota strains, which agglutinate with Vibrio cholerae O139 Bengal antiserum, possess a serologically distinct fimbrial colonization factor.

Pili of Aeromonas trota strain 1220, which agglutinates with Vibrio cholerae O139 Bengal antiserum, were purified and characterized. The molecular mass of the subunit protein was estimated to be 20 kDa and the pl was 5 center dot 4. The pili were immunologically unrelated to the other Aeromonas pili reported so far. However, the N-terminal amino acid sequence of the subunit pilin was similar to those of the pilins from other Aeromonas pili reported previously. Neither A. trota cells nor pili purified from strain 1220 agglutinated human and rabbit erythrocytes, but both adhered to the rabbit intestine. Bacterial cells pretreated with antipilus antibody (Fab portion) failed to adhere to the rabbit intestine. Moreover, bacteria did not adhere to the rabbit intestine pretreated with the purified pili. This pilus antigen was not detected in V. cholerae O139 Bengal and other Aeromonas spp. These findings suggest that the pilus of the A. trota strain is a novel colonization factor of Aeromonas spp.

Aeromonas↗