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Molecular Epidemiology of Methicillin–Resistant Staphylococcus Aureus in a Veterans Administration Medical Center

Published online by Cambridge University Press:  02 January 2015

Loreen A. Herwaldt ,
Jean M. Pottinger ,
Stacy Coffman  and
Jean Tjaden
Loreen A. Herwaldt*
Affiliation:
The University of Iowa Hospitals and Clinics, Iowa City, Iowa Department of Internal Medicine, The University of Iowa College of Medicine, Iowa City, Iowa The Veterans Affairs Medical Center, Iowa City, Iowa
Jean M. Pottinger
Affiliation:
The University of Iowa Hospitals and Clinics, Iowa City, Iowa The Veterans Affairs Medical Center, Sioux Falls, South Dakota
Stacy Coffman
Affiliation:
Department of Internal Medicine, The University of Iowa College of Medicine, Iowa City, Iowa
Jean Tjaden
Affiliation:
The Veterans Affairs Medical Center, Sioux Falls, South Dakota
*
C 520-1 GH, The University of Iowa Hospitals and Clinics, Iowa City, IA 52242-1081
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Abstract

Objectives:

To determine whether patients who were colonized or infected with methicillin-resistant Staphylococcus aureus (MRSA) persistently carried the same strain and to identify the extent of strain variation within a population of patients.

Design:

Molecular typing by pulsed-field gel electrophoresis (PFGE) of stored MRSA isolates.

Setting:

A Veterans Administration Medical Center with 288 hospital, 45 intermediate-care, and 75 extended-care beds.

Isolates:

Between January 1991 and March 1993, 91 patients had MRSA identified in routine cultures. One hundred isolates from 57 patients (63%) were available for typing.

Results:

Before 1988, only occasional MRSA isolates were identified. By 1993, 50% of S. aureus isolates from unique patients were resistant to methicillin. PFGE identified 7 MRSA strains, 3 of which were identified in specimens from 1 patient each. The most common strains were SD4 (20 patients), SD1 (12 patients), SD2 (12 patients), and SD5a (5 patients). Twenty patients had 2 or more isolates obtained at least 1 week apart (mean, 30.7 weeks; range, 1 to 102 weeks). Of these patients, 12 were colonized or infected with only one strain (mean time observed, 25.1 weeks; range, 1 to 82 weeks). Eight patients had at least 2 different strains (mean time observed, 39 weeks; range, 2 to 102 weeks).

Conclusion:

Numerous MRSA strains circulated in tiiis endemic setting; 40% of patients observed over time were colonized or infected witii more than one strain. Molecular typing was an essential tool for evaluating the epidemiology of MRSA in this setting.

Type
Original Articles
Information
Infection Control & Hospital Epidemiology , Volume 23 , Issue 9 , September 2002 , pp. 502 - 505
Copyright
Copyright © The Society for Healthcare Epidemiology of America 2002

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