MRSA Research Today is a free monthly online journal that collates and summarizes the latest research about MRSA, including details on methicillin-resistant staphylococcus aureus, hospitals, infection, antibiotic resistance, superbugs.

Recurrence of heterogeneous methicillin-resistant Staphylococcus aureus (MRSA) among the MRSA clinical isolates in a Japanese university hospital.

Kishii K, Ito T, Watanabe S, Okuzumi K, Hiramatsu K

Department of Infection Control Science, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.

Objectives In the early 1980s, heterogeneous methicillin-resistant Staphylococcus aureus (hetero-MRSA) strains were predominant in the University of Tokyo Hospital. But, in the 1990s, they were completely substituted by homogeneously highly methicillin-resistant S. aureus (homo-MRSA) strains. Since 2000, however, we started observing an increase in MRSA strains with low cefazolin MICs (MRCLSA). This study was performed to understand the phenomenon by characterization of the 'cefazolin-susceptible' MRSA strains. Methods A total of 39 MRCLSA strains were collected between July 2000 and June 2002 and compared with 10 homo-MRSA strains isolated during the same period for their antibiograms and genotypes. The strains were also compared with the hetero-MRSA strains isolated in the same hospital in the early 1980s. Results In contrast to the homogeneous genotype [multilocus sequence type 5 and SCCmec type II.1 (IIa)] and multiresistant nature of the homo-MRSA strains, the MRCLSA strains were composed of various genotypes as revealed by multilocus sequence typing and SCCmec typing and had resistance only to a limited number of antibiotics. Most of the MRCLSA strains were also genetically differentiated from the hetero-MRSA strains of the 1980s. However, population analysis revealed that all of the MRCLSA strains were classified as hetero-MRSA strains. Conclusions A new group of hetero-MRSA strains genetically distinct from those dominant in the same hospital in the early 1980s might have emerged in the community and started invading the university hospital. This phenomenon may be caused by the change in the pattern of antibiotic use.

Published 9 May 2008 in J Antimicrob Chemother.
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Articles on MRSA published 9 May 2008:

Modelling the impact of antibiotic use and infection control practices on the incidence of hospital-acquired methicillin-resistant Staphylococcus aureus: a time-series analysis.   J Antimicrob Chemother.

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Articles on MRSA published 8 May 2008:

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Epidemiological surveillance for community-associated methicillin-resistant Staphylococcus aureus revealed prevalences of 33% and 13% in pediatric and adult patients, respectively, in Cordoba, Argentina, in 2005. This study describes for the first time the emergence and dissemination of the sequence type 5 (ST5) lineage as the most prevalent clone (89%) (pulsed-field gel electrophoresis type I-ST5-staphylococcal cassette chromosome type IVa-spa type 311) harboring the Panton-Valentine ... [Abstract] [Full-text]

Articles on MRSA published 5 May 2008:

Methicillin-resistant Staphylococcus aureus carriage in a long-term care facility: hypothesis about selection and transmission.   Age Ageing, 37(3): 294-9.

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