A comparison of clinical virulence of nosocomially acquired methicillin-resistant and methicillin-sensitive Staphylococcus aureus infections in a university hospital.
OBJECTIVE
To compare the clinical virulence of nosocomially acquired methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S aureus (MSSA) infections in 1989.


METHODS
A retrospective comparison of host factors, in-hospital exposures, sites of infections, and outcomes of patients with nosocomial MRSA and MSSA infections.


METHODS
University of Illinois Hospital, Chicago, Illinois.


METHODS
Forty-four adult patients with nosocomial S aureus infections.


RESULTS
The 22 MRSA-infected and 22 MSSA-infected persons were similar regarding mean age, gender, underlying diseases, and exposure to surgery. Before developing infection, MRSA-infected persons were more likely to have received antibiotics (73% compared with 27%, odds ratio = 7.1, 95% confidence interval [CI95] = 2.0-25.8 p = .003) and to have stayed in the hospital > 2 weeks (64% compared with 18%, odds ratio = 7.9, CI95 = 2.0-31.6, p = .002). Bacteremia was the most common presentation in the MRSA and MSSA groups (55% and 59%, respectively). Infectious complications and death were infrequent in both groups.


CONCLUSIONS
MRSA and MSSA strains infect patients with similar demographic features and underlying diseases, but MRSA infections are significantly more common among patients with previous antibiotic therapy and a prolonged preinfection hospital stay. Clinical presentations and outcomes did not differ significantly between the 2 groups. Thus, similar to studies in the early 1980s, our findings do not suggest greater intrinsic virulence of MRSA.
Hershow
R C
RC
School of Medicine, University of Illinois, Chicago 60612.
Khayr
W F
WF
Smith
N L
NL
D002641:Chicago; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D004352:Drug Resistance, Microbial; D006746:Hospital Bed Capacity, 500 and over; D006785:Hospitals, University / Q000706:statistics & numerical data*; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D008712:Methicillin / Q000494:pharmacology*; D016106:Methicillin Resistance; D008875:Middle Aged; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000472:pathogenicity*; D016896:Treatment Outcome; D014774:Virulence
D008712:Methicillin