Genomic identification of cryptic susceptibility to penicillins and β-lactamase inhibitors in methicillin-resistant Staphylococcus aureus
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Antibiotic resistance in bacterial pathogens threatens the future of modern medicine. One such resistant pathogen is methicillin-resistant Staphylococcus aureus (MRSA), which is resistant to nearly all β-lactam antibiotics, limiting treatment options. Here, we show that a significant proportion of MRSA isolates from different lineages, including the epidemic USA300 lineage, are susceptible to penicillins when used in combination with β-lactamase inhibitors such as clavulanic acid. Susceptibility is mediated by a combination of two different mutations in the mecA promoter region that lowers mecA-encoded penicillin-binding protein 2a (PBP2a) expression, and in the majority of isolates by either one of two substitutions in PBP2a (E246G or M122I) that increase the affinity of PBP2a for penicillin in the presence of clavulanic acid. Treatment of S. aureus infections in wax moth and mouse models shows that penicillin/β-lactamase inhibitor susceptibility can be exploited as an effective therapeutic choice for ‘susceptible’ MRSA infection. Finally, we show that isolates with the PBP2a E246G substitution have a growth advantage in the presence of penicillin but the absence of clavulanic acid, which suggests that penicillin/β-lactamase susceptibility is an example of collateral sensitivity (resistance to one antibiotic increases sensitivity to another). Our findings suggest that widely available and currently disregarded antibiotics could be effective in a significant proportion of MRSA infections.
Harrison , E M , Ba , X , Coll , F , Blane , B , Restif , O , Carvell , H , Köser , C U , Jamrozy , D , Reuter , S , Lovering , A , Gleadall , N , Bellis , K L , Uhlemann , A C , Lowy , F D , Massey , R C , Grilo , I R , Sobral , R , Larsen , J , Rhod Larsen , A , Vingsbo Lundberg , C , Parkhill , J , Paterson , G K , Holden , M T G , Peacock , S J & Holmes , M A 2019 , ' Genomic identification of cryptic susceptibility to penicillins and β-lactamase inhibitors in methicillin-resistant Staphylococcus aureus ' , Nature Microbiology , vol. 4 , no. 10 , pp. 1680-1691 . https://doi.org/10.1038/s41564-019-0471-0
© 2019, the Author(s), under exclusive licence to Springer Nature Ltd. This work has been made available online in accordance with the publisher's policies. This is the author created accepted version manuscript following peer review and as such may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1038/s41564-019-0471-0
DescriptionThis work was supported by Medical Research Council partnership grants (G1001787/1 and MR/N002660/1) held between the Department of Veterinary Medicine and School of Clinical Medicine at the University of Cambridge, the Moredun Research Institute and the Wellcome Sanger Institute. This publication presents independent research supported by the Health Innovation Challenge Fund (WT098600 and HICF-T5-342)—a parallel funding partnership between the Department of Health and Wellcome Trust. E.M.H. is supported by a UK Research and Innovation Fellowship (MR/S00291X/1). F.C. is supported by the Wellcome Trust (201344/Z/16/Z). X.B. is supported by a UK–China AMR Partnership Grant (MR/P007201/1).
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