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Journal of Clinical Microbiology, February 1998, p. 414-420, Vol. 36, No. 2
W. W. Karakawa Microbial Pathogenesis
Laboratory, NABI, Rockville, Maryland1;
School of Medicine, University of Maryland, Baltimore,
Maryland2; and
Department of
Medicine, Oregon Health Sciences University, Portland,
Oregon3
Received 5 September 1997/Returned for modification 10 October
1997/Accepted 13 November 1997
Staphylococcus aureus is a major cause of nosocomial
infections. During the period from March 1992 to March 1994, the
patients admitted to the intensive care unit of the University of
Maryland Shock Trauma Center were monitored for the development of
S. aureus infections. Among the 776 patients eligible for
the study, 60 (7.7%) patients developed 65 incidents of nosocomial
S. aureus infections. Of the clinical isolates, 43.1%
possessed a polysaccharide type 5 capsule, 44.6% possessed a type 8 capsule, and the remaining 12.3% had capsules that were not typed by
the type 5 or type 8 antibodies. Six antibiogram types were noted among
the infection-related isolates, with the majority of the types being
resistant only to penicillin and ampicillin. It was noted that the
majority of cases of pneumonia were caused by relatively susceptible
strains, while resistant strains were isolated from patients with
bacteremia and other infections. Only 16 (6.3%) of the isolates were
found to be methicillin-resistant S. aureus (MRSA). DNA
fingerprinting by pulsed-field gel electrophoresis showed 36 different
patterns, with characteristic patterns being found for MRSA strains and the strains with different capsular types. Clonal relationships were
established, and the origins of the infection-related isolates in each
patient were determined. We conclude that (i) nosocomial infection-related isolates from the shock trauma patients did not
belong to a single clone, although the predominance of a
methicillin-resistant genotype was noted, (ii) most infection-related
S. aureus isolates were relatively susceptible to
antibiotics, but a MRSA strain was endemic, and (iii) for practical
purposes, the combination of the results of capsular and antibiogram
typing can be used as a useful epidemiological marker.
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Phenotypic and Genotypic Characterization of
Nosocomial Staphylococcus aureus Isolates from Trauma
Patients

*
Corresponding author. Mailing address: NABI Rockville,
12280 Wilkins Ave., Rockville, MD 20852. Phone: (301) 255-6970. Fax: (301) 770-2014. E-mail: afattom{at}nabi.com.
Present address: Natural Science Division, Lebanese American
University, Beirut, Lebanon.
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