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

Several methods were used to type 64 clinical isolates of coagulase-negativ e staphylococci (CNS) derived from hospitals in Morocco. The clinical isola tes originated principally from blood cultures and wound sources. These iso lates 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 me thods were examined: Utility ribotyping analysis (Ribotyping); PCR analysis performed with 16S-23S ribosomal-DNA intergenic spacer (ITS-PCR); PCR-base d random amplified polymorphic DNA (RAPD). The results obtained by the mole cular techniques were contrasted to those of conventional phenotypic tests. Conventional phenotypic tests allowed the outright recognition of the majo rity of isolates (50/64). These 50 isolates were subdivided into 33 novobio cin-susceptible and 17 novobiocin-resistant strains of CNS. However, 2 othe r novobiocin-susceptible and 12 other novobiocin-resistant isolates remaine d unclassified by these tests. There was a good agreement between the conve ntional phenotypic tests and RAPD for the 33 novobiocin-susceptible isolate s. But, the RAPD technique permitted the assignment of the two unidentified novobiocin-susceptible isolates to the Staphylococcus hominis species. A c omplete correlation was obtained between the three molecular tools for reco gnition of the 12 novobiocin-resistant isolates that were not identified by phenotypic typing; these were in fact identified as 5 Staphylococcus cohni i and 4 Staphylococcus equorum. Three isolates remained unidentified by all three systems of molecular techniques. (C) 2001 Editions scientifiques et medicales Elsevier SAS.