Rapid Microarray-Based Identification of DifferentmecAAlleles in Staphylococci

Abstract

ABSTRACTTo screen isolates and to identifymecAalleles, publishedmecAsequences were analyzed, and a microarray for the rapid discrimination ofmecAalleles was designed. A GenBank analysis yielded 135 full-length gene sequences annotated asmecA. These sequences clustered into 32 different alleles corresponding to 28 unique amino acid sequences and to 15 distinct hybridization patterns on this microarray. A collection of 78 clinical and veterinary isolates ofStaphylococcusspp. was characterized using this assay. Nine of the 15 expected patterns, as well as one as-yet-unknown pattern, were identified. These patterns were detected in various epidemic methicillin-resistantStaphylococcus aureusstrains, inS. pseudintermedius, and in coagulase-negative species such asS. epidermidis,S. fleurettii, orS. haemolyticus. There was no correlation between the differentmecAhybridization patterns and the SCCmectype. Determination of MICs showed thatmecAalleles corresponding to only four of these nine patterns were associated with β-lactam resistance. ThemecAalleles that did not confer β-lactam resistance were largely restricted to coagulase-negative staphylococci of animal origin, such asS. sciuriandS. vitulinus. Because of the diversity of sequences and the different impact on β-lactam susceptibility, the existence of differentmecAalleles needs to be taken into account when designing diagnostic assays for the detection ofmecA.