Rapid detection, differentiation and typing of methicillin-resistant Staphylococcus aureus harbouring either mecA or the new mecA homologue mecALGA251

Abstract

The recent finding of a new mecA homologue, mecA(LGA251) , with only 70% nucleotide homology to the conventional mecA gene has brought the routine testing for mecA as a confirmatory test for methicillin-resistant Staphylococcus aureus (MRSA) into question. A multiplex PCR was designed to differentiate mecA(LGA251) from the known mecA together with detection of lukF-PV and the spa gene fragments, enabling direct spa typing by sequencing of the PCR amplicons. The PCR analysis and subsequent spa typing were validated on a large collection (n=185) of contemporary MRSA and methicillin-sensitive S. aureus isolates, including 127 isolates carrying mecA(LGA251) . The mecA(LGA251) gene was situated in staphylococcal cassette chromosome mec type XI elements, and sequence variation within a 631-bp fragment of mecA(LGA251) in 79 isolates indicated a very conserved gene sequence. Following a successful validation, the multiplex PCR strategy was implemented in the routine testing of MRSA for national surveillance. Over a 2-month period, among 203 samples tested, 12 new MRSA cases caused by isolates carrying mecA(LGA251) were identified, emphasizing the clinical importance of testing for these new MRSA isolates.

Comparison of Xpert MRSA/SA Nasal and MRSA/SA ELITe MGB Assays for Detection of the mecA Gene with Susceptibility Testing Methods for Determination of Methicillin Resistance in Staphylococcus aureus Isolates

“…The primer sequences used in this study are listed in Table 1. Oligonucleotides ranging from 138 to 800 bp were selected from the published DNA sequences of the S. aureus genes (9,10,17). The mecA LGA251 primers were used to verify the presence of mecA LGA251 in all 82 isolates tested by the Xpert MRSA/SA assay and the MRSA/SA ELITe MGB kit.…”

“…A novel mecA homolog (mecC or mecA LGA251 , with reference to the S. aureus LGA251 isolates from which it was characterized) was recently described (8)(9)(10). It has been found in S. aureus lineages typically associated with cattle, i.e., clonal complex 130 (CC130), CC1943, and sequence type 425 (8).…”

A Staphylococcus xylosus Isolate with a New mecC Allotype

“…As a result, the transpeptidase activity of PBP2a is functional at normally inhibitory concentrations of beta-lactam antibiotics, allowing cell wall synthesis to occur (2)(3)(4). Recently, a novel variant of mecA was identified in Staphylococcus aureus from cattle (5), humans, and a range of other animal species (6) in Denmark, France, The Netherlands, Ireland, Germany, Belgium, and the United Kingdom (5,(7)(8)(9)(10)(11). This subtype was originally designated mecA LGA251 but has since been renamed mecC and shares 70% nucleotide identity with the conventional mecA gene.…”

Comparison between reduced susceptibility to disinfectants and multidrug resistance among hospital isolates of pseudomonas aeruginosa and staphylococcus aureus in bangladesh

“…DNA was extracted from the bacterial isolates using DNA extraction method followed by Stegger et al (30). DNA samples were stored at -20°C.…”