Update on the genotypic and phenotypic characteristics of <I>Staphylococcus hominis</i> subsp. <I>novobiosepticus</i> strains from Czech hospitals
| Authors | |
|---|---|
| Year of publication | 2004 |
| Type | Article in Proceedings |
| Conference | 11th International Symposium on Staphylococci & Staphylococcal Infections. Plenary Summaries & Poster Abstracts |
| MU Faculty or unit | |
| Citation | |
| Web | http://www.isssi.org/ |
| Field | Genetics and molecular biology |
| Keywords | staphylococcus; coagulase negative staphylococci; molecular epidemiology |
| Description | A new subspecies, Staphylococcus hominis subsp. novobiosepticus (SHN), isolated from relevant human clinical material, was described in 1998, arousing little attention in the world. We present genetic and phenotypic characteristics of SHN strains from 25 Czech cities. The aims of the present study were to determine phenotypic variability of SHN strains and to compare different molecular techniques for suitability for routine discrimination between the methicillin-resistant strains of S. hominis subsp. hominis and SHN. A total of 269 SHN strains collected in 30 Czech hospitals mainly from the blood (69%) were characterized phenotypically by both conventional tests and commercial kits and tested for resistance to 12 antibiotics. The following molecular typing methods were used to map characteristics of 90 selected SHN strains: SmaI macrorestriction analysis resolved by PFGE; amplification of rDNA intergenic spacers (ITS-PCR); AP-PCR; rep-PCR with primer ERIC2; and PCR-RFLP analysis of mecA gene using MseI restriction endonuclease. Few differences in phenotypic characters were found between our strains and the SHN type strains (D-mannose, acetoin production, lactose, melezitose, hydrolysis of aesculine). Nearly all of our SHN strains produced slime, about 75% of the strains produced delta-haemolysin, and all tested strains were multiresistant to antibiotics. PFGE allowed for unambiguous differentiation between the two subspecies and, with the database of restriction profiles, seems to be highly suitable for the study of genomic variability in S. hominis. Other DNA based techniques showed low discrimination power compared with PFGE and were not able to differentiate the two subspecies from each other. Amplification of rDNA intergenic spacers yielded an identical profile for all SHN strains which is found in 90 % of S. hominis. subsp. hominis strains. Therefore, ITS-PCR is a suitable tool for confirming identification at the species level. Highly virulent and resistant SHN strains as opportunistic pathogens certainly play an important role in hospital infections, particularly in those of the bloodstream. The subspecies of S. hominis are an example of the genetically closely related but phenotypically highly divergent strains. Apart from resistance to antibiotics and conversion of some substrates, differentiation of the two subspecies is supported by the results of DNA-DNA hybridization (Kloos et al., 1998) and sequencing of hsp60 gene (Kwok and Chow, 2003) while sequencing of 16S rRNA gene does not allow for unambiguous differentiation (Fitzgibbon et al., 2001). Nevertheless, DNA-DNA hybridization and sequencing cannot be routinely used in clinical microbiological laboratories. It can be concluded that the genetic relatedness between the two subspecies has not been characterized in detail yet and that apart from phenotypic tests, PFGE remains the only method suitable for differentiation of the two subspecies. |
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