DETECTION BY POLYMERASE CHAIN-REACTION OF GENES ENCODING AMINOGLYCOSIDE-MODIFYING ENZYMES IN METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS ISOLATES OF EPIDEMIC PHAGE TYPES

The polymerase chain reaction (PCR) was used to identify the aacA-aphD , aphA3 and aadC genes, encoding the aminoglycoside-modifying enzymes AAC(6')-APH(2''), APH(3')III and ANT(4' 4''), respectively, and the me thicillin resistance determinant mecA, in epidemic aminoglycoside and methicillin-resistant isolates of Staphylococcus aureus. In total, 37 isolates collected in the period 1980-1985 and 81 isolates from the pe riod 1991-1992 were obtained from 10 different Belgian hospitals. Epid emic isolates from the earlier period were characterised by phage type C (6/47/54/75) of phage group III, whereas two other epidemic phage t ypes of group III-types A (77) and B (47/54/75/77/84/85)-were commones t in isolates from the second period. The bifunctional AAC(6')-APH(2'' ) was the enzyme encountered most frequently. The prevalence of APH(3' )III decreased significantly in the 1991-1992 period, while ANT(4', 4' ') was found solely in isolates from this period. Resistance mechanism s were more complex in isolates from the 1991-1992 period and the mecA gene was detected in all isolates. The PCR results corresponded well with those obtained in the radiochemical phosphocellulose paper bindin g assay. Isolates from the 1991-1992 period were shown to express sign ificantly higher levels of acetyltransferase activity than isolates fr om the 1980s.