Use of fluorescent amplified fragment length polymorphism (fAFLP) to characterise methicillin-resistant Staphylococcus aureus

The new PCR-based genotyping technique, fluorescent amplified fragment leng th polymorphism (fAFLP), was compared for discriminatory power and reproduc ibility with standard phenotypic methods, a coagulase gene (coa) restrictio n fragment length polymorphism (RFLP) method and pulsed-field gel electroph oresis (PFGE), in typing 34 isolates and four reference strains of methicil lin-resistant Staphylococcus aureus (MRSA). The fAFLP showed from 40 to 75 fragments, 50 to 450 base pairs (bp) in size. Based on replicate studies, t he isolates were judged indistinguishable when their fAFLP pattern was >93. 7% similar. Only two of the isolates were indistinguishable by this criteri on. Thirty-one MRSA fell into four major fAFLP groups (1, 2, 3 and 4) at th e level of >79.9% similarity. Three other isolates and an EMRSA-16 strain f ell outside these major groups. Within both fAFLP groups 1 and 2, two subgr oups, A and B, could be identified at similar to 82.0% similarity. While mo st isolates within group 1 could also be separated by their phenotypic and coagulase gene (coa) RFLP pattern, all the isolates within fAFLP groups 2A and 2B were identical on the basis of these characters. The MRSA within fAF LP groups 3 and 4 were heterogeneous by their phenotypic characteristics an d coo gene RFLP patterns. fAFLP was reproducible and distinguished between MRSA isolates that appeared identical by other methods. It is likely to con tribute to the epidemiological analysis of outbreaks of MRSA infection. (C) 1999 Elsevier Science B.V. All rights reserved.