Molecular techniques open up new vistas for typing of coagulase-negative staphylococci.

Several methods were used to type 64 clinical isolates of coagulase-negative staphylococci (CNS) derived from hospitals in Morocco. The clinical isolates originated principally from blood cultures and wound sources. These isolates provided the opportunity to substantially compare the proficiency of developing molecular techniques with conventional phenotypic tests for use in the identification of clinical staphylococci. The following molecular methods were examined: Utility ribotyping analysis (Ribotyping); PCR analysis performed with 16S-23S ribosomal-DNA intergenic spacer (ITS-PCR); PCR-based random amplified polymorphic DNA (RAPD). The results obtained by the molecular techniques were contrasted to those of conventional phenotypic tests. Conventional phenotypic tests allowed the outright recognition of the majority of isolates (50/64). These 50 isolates were subdivided into 33 novobiocin-susceptible and 17 novobiocin-resistant strains of CNS. However, 2 other novobiocin-susceptible and 12 other novobiocin-resistant isolates remained unclassified by these tests. There was a good agreement between the conventional phenotypic tests and RAPD for the 33 novobiocin-susceptible isolates. But, the RAPD technique permitted the assignment of the two unidentified novobiocin-susceptible isolates to the Staphylococcus hominis species. A complete correlation was obtained between the three molecular tools for recognition of the 12 novobiocin-resistant isolates that were not identified by phenotypic typing; these were in fact identified as 5 Staphylococcus cohnii and 4 Staphylococcus equorum. Three isolates remained unidentified by all three systems of molecular techniques.

Relationship of Staphylococcal isolates in a Moroccan hospital by comparing phenotypical and genotypical tests.

The relationship of Staphylococcus isolates was determined among a collection of 26 clinical strains at the Centre Hospitalier Universitaire de Rabat. These isolates originated principally from blood culture and wounds. In order to affirm the clonal origins of these isolates, six phenotype (biotype, anti-biotype, serotype, phage type), and genotype (random amplified polymorphic DNA, pulsed field gel electrophoresis) methods were used. Biotyping, anti-biotyping, phage and serotyping were generally not sufficient while many isolates remained non-phage typeable. Random amplified polymorphic DNA analysis used in epidemiological typing seemed suitable for S. epidermidis and S. haemolyticus. However, rigorous standardization will be needed to assure reliable results. Pulsed field gel electrophoresis discriminated more efficiently than random amplification polymorphic DNA analysis. This study attests to the suitability of two or more methods in combination for typing Staphylococcus isolates.

Distribution of Staphylococcus sciuri subspecies among human clinical specimens, and profile of antibiotic resistance.

The distribution of three subspecies comprising Staphylococcus sciuri was determined for a collection of 30 clinical isolates originating from Morocco, the United Kingdom, and France. The sources of these isolates were principally wounds, skin, and soft tissue infections. At the species level, the isolates were identified according to biochemical characteristics and at the subspecies level by the ribotyping technique. PCR analysis performed with the 16S-23S ribosomal DNA intergenic spacer was less powerful for subspecies differentiation. S. sciuri subsp. sciuri was the most frequent subspecies (21 isolates) found in the collection, whereas S. sciuri subsp. rodentium (seven isolates) and S. sciuri subsp. carnaticus (two isolates) were less common. mecA or a mecA-related gene was detected by PCR and Southern blot in all 30 S. sciuri isolates, supporting the suggestion that S. sciuri species are the natural reservoir of the mecA gene. While the linA/linA' gene coding for lincomycin resistance was present in five isolates, an uncharacterized gene for this resistance was suspected in seventeen other isolates.