MRSA emerged years before methicillin was even discovered
Methicillin resistant Staphylococcus aureus (MRSA) emerged long before the introduction of the antibiotic methicillin into clinical practice, according to a study published in the open access journal Genome Biology. It was the widespread use of earlier antibiotics such as penicillin rather than of methicillin itself which caused MRSA to emerge, researchers at the University of St Andrews, and the Wellcome Trust Sanger Institute, UK suggest.
The researchers found that S. aureus acquired the gene that confers methicillin resistance - mecA - as early as the mid-1940s - fourteen years before the first use of methicillin.
Professor Matthew Holden, molecular microbiologist at the University of St Andrews, the corresponding author said: "Our study provides important lessons for future efforts to combat antibiotic resistance. It shows that new drugs which are introduced to circumvent known resistance mechanisms, as methicillin was in 1959, can be rendered ineffective by unrecognized, pre-existing adaptations in the bacterial population. These adaptations happen because - in response to exposure to earlier antibiotics - resistant bacterial strains are selected instead of non-resistant ones as bacteria evolve."
Catriona P. Harkins et al, Methicillin-resistant Staphylococcus aureus emerged long before the introduction of methicillin into clinical practice, Genome Biology (2017). DOI: 10.1186/s13059-017-1252-9
A colorized scanning electron micrograph of MRSA. Credit: National Institute of Allergy and Infectious Diseases A colorized scanning electron micrograph of MRSA. Credit: National Institute of Allergy and Infectious Diseases
