Study shows that Staphylococcus aureus acquired the methicillin-resistance gene in the middle of 1940s. A latest study was shown that methicillin-resistant S. aureus (MRSA) emerged long before the antibiotic methicillin into clinical practice. It was the widespread use of earlier antibiotics, such as researchers from the UK preferred penicillin to methicillin itself which caused MRSA to emerge.

      The researchers found that S. aureus acquired the gene with methicillin resistance, i.e., mecA , as early as the mid-1940s, which was 14 years before the first use of methicillin. The mecA gene confers resistance by producing a protein called PBP2a, which decreases the binding efficiency of antibiotics via the cell wall of S. aureus. The introduction of penicillin in the 1940s led to the selection of S. aureus strains that carried the methicillin resistance gene.

      What was the origin of the first MRSA and how to trace its evolutionary history? The researchers sequenced the genomes of a unique collection of 209 historic S. aureus isolates. The oldest of these isolates were identified over 50 years ago by the S. aureus reference laboratory of Public Health England and had been stored in their original freeze-dried state. The researchers found the genes in these isolates that confer resistance to numerous other antibiotics, as well as genes associated with decreased susceptibility to disinfectants.

Reference

CP Harkins, B Pichon, M Doumith, et al. Methicillin-resistant Staphylococcus aureus emerged long before the introduction of methicillin into clinical practice. Genome Biology, 2017, 18(1):130.