Dataset Information

Emergence of linezolid-resistant mutants in a susceptible-cell population of methicillin-resistant Staphylococcus aureus.

ABSTRACT: Methicillin-resistant Staphylococcus aureus with a MIC of linezolid of 4 ?g/ml, isolated from a patient who had undergone unsuccessful linezolid therapy, yielded linezolid-resistant mutants in blood agar at 48 h of incubation. The resistant clones showed a MIC of linezolid ranging from 8 to 64 ?g/ml and accumulated the T2500A mutation(s) of the rRNA genes. Emergence of these resistant clones appears to be facilitated by a cryptic mutation or mutations associated with chloramphenicol resistance.

SUBMITTER: Ikeda-Dantsuji Y

PROVIDER: S-EPMC3088184 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Emergence of linezolid-resistant mutants in a susceptible-cell population of methicillin-resistant Staphylococcus aureus.

Ikeda-Dantsuji Yurika Y Hanaki Hideaki H Nakae Taiji T Takesue Yoshio Y Tomono Kazunori K Honda Junichi J Yanagihara Katsunori K Mikamo Hiroshige H Fukuchi Kunihiko K Kaku Mitsuo M Kohno Shigeru S Niki Yoshihito Y

Antimicrobial agents and chemotherapy 20110228 5

Methicillin-resistant Staphylococcus aureus with a MIC of linezolid of 4 μg/ml, isolated from a patient who had undergone unsuccessful linezolid therapy, yielded linezolid-resistant mutants in blood agar at 48 h of incubation. The resistant clones showed a MIC of linezolid ranging from 8 to 64 μg/ml and accumulated the T2500A mutation(s) of the rRNA genes. Emergence of these resistant clones appears to be facilitated by a cryptic mutation or mutations associated with chloramphenicol resistance. ...[more]

PMID: 21357291

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Project description:BackgroundBloodstream infections due to Staphylococcus aureus cause significant patient morbidity and mortality worldwide. Of major concern is the emergence and spread of methicillin-resistant S. aureus (MRSA) in bloodstream infections, which are associated with therapeutic failure and increased mortality.MethodsWe generated high quality draft genomes from 323 S. aureus blood culture isolates from patients diagnosed with bloodstream infection at the Dartmouth-Hitchcock Medical Center, New Hampshire, USA in 2010-2018.ResultsIn silico detection of antimicrobial resistance genes revealed that 133/323 isolates (41.18%) carry horizontally acquired genes conferring resistance to at least three antimicrobial classes, with resistance determinants for aminoglycosides, beta-lactams and macrolides being the most prevalent. The most common resistance genes were blaZ and mecA, which were found in 262/323 (81.11%) and 104/323 (32.20%) isolates, respectively. Majority of the MRSA (102/105 isolates or 97.14%) identified using in vitro screening were related to two clonal complexes (CC) 5 and 8. The two CCs emerged in the New Hampshire population at separate times. We estimated that the time to the most recent common ancestor of CC5 was 1973 (95% highest posterior density (HPD) intervals: 1966-1979) and 1946 for CC8 (95% HPD intervals: 1924-1959). The effective population size of CC8 increased until the late 1960s when it started to level off until late 2000s. The levelling off of CC8 in 1968 coincided with the acquisition of SCCmec Type IV in majority of the strains. The plateau in CC8 also coincided with the acceleration in the population growth of CC5 carrying SCCmec Type II in the early 1970s, which eventually leveled off in the early 1990s. Lastly, we found evidence for frequent recombination in the two clones during their recent clonal expansion, which has likely contributed to their success in the population.ConclusionsWe conclude that the S. aureus population was shaped mainly by the clonal expansion, recombination and co-dominance of two major MRSA clones in the last five decades in New Hampshire, USA. These results have important implications on the development of effective and robust strategies for intervention, control and treatment of life-threatening bloodstream infections.

Dataset Information

Emergence of linezolid-resistant mutants in a susceptible-cell population of methicillin-resistant Staphylococcus aureus.

Publications

Emergence of linezolid-resistant mutants in a susceptible-cell population of methicillin-resistant Staphylococcus aureus.

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