T. Nawas et al., PHENOTYPIC AND GENOTYPIC CHARACTERIZATION OF NOSOCOMIAL STAPHYLOCOCCUS-AUREUS ISOLATES FROM TRAUMA PATIENTS, Journal of clinical microbiology, 36(2), 1998, pp. 414-420
Staphylococcus aureus is a major cause of nosocomial infections, Durin
g the period from March 1992 to March 1994, the patients admitted to t
he intensive care unit of the University of Maryland Shock Trauma Cent
er were monitored for the development of S. aureus infections, Among t
he 776 patients eligible for the study, 60 (7.7%) patients developed 6
5 incidents of nosocomial S. aureus infections, Of the clinical isolat
es, 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 ty
ped by the type 5 or type 8 antibodies, Six antibiogram types were not
ed among the infection-related isolates, with the majority of the type
s being resistant only to penicillin and ampicillin. It was noted that
the majority of cases of pneumonia mere caused by relatively suscepti
ble strains, while resistant strains were isolated from patients,vith
bacteremia and other infections, Only 16 (6.3%) of the isolates were f
ound 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 isolate
s from the shock trauma patients did not belong to a single clone, alt
hough the predominance of a methicillin resistant genotype was noted,
(ii) most infection-related S. aureus isolates were relatively suscept
ible to antibiotics, but a MRSA strain was endemic, and (iii) for prac
tical purposes, the combination of the results of capsular and antibio
gram typing can be used as a useful epidemiological marker.