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Canadian Journal of Infectious Diseases and Medical Microbiology
Volume 18, Issue 3, Pages 181-188
http://dx.doi.org/10.1155/2007/136796
Original Article

Health Care-Associated Staphylococcus aureus Pneumonia

Duncan Webster,1 Linda Chui,2 Gregory J Tyrrell,2 and Thomas J Marrie3

1Department of Medical Microbiology, Dalhousie University, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada
2Provincial Laboratory for Public Health, Department of Laboratory Medicine & Pathology, University of Alberta, Edmonton, Alberta, Canada
3Division of Infectious Diseases, Department of Internal Medicine, University of Alberta, Edmonton, Alberta, Canada

Received 21 August 2006; Accepted 21 December 2006

Copyright © 2007 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

INTRODUCTION: While Staphylococcus aureus is an uncommon but serious cause of traditional community-acquired pneumonia (CAP), it is a predominant cause of nosocomial pneumonia in addition to the unique clinical entity of health care-associated pneumonia (HCAP). A cohort of bacteremic S aureus pneumonia cases was reviewed to determine the role of HCAP among the cohort, and to assess for differences between CAP and HCAP.

PATIENTS AND METHODS: Bacteremic S aureus pneumonia cases were identified from a prospective study of all patients diagnosed with CAP who presented to hospitals in Edmonton, Alberta, between November 2000 and November 2002. These cases were subsequently reviewed retrospectively. Demographic, clinical and microbiological data were obtained, and patients were classified as having CAP or HCAP. Relatedness of isolates was determined by pulsed-field gel electrophoresis analysis in conjunction with epidemiological information.

RESULTS: There were 28 cases of bacteremic S aureus pneumonia identified. Fifty-seven per cent were reclassified as having HCAP, and 43% remained classified as having CAP. The CAP cohort was significantly younger than the HCAP cohort (mean age 49.0±23.7 years versus 67.8±18.6 years; P=0.035) with higher rates of intravenous drug use (50% versus 0%; P=0.002). Long-term care facility residence (44%) was common in the HCAP cohort. The HCAP cohort presented with more severe illness, having a higher mean pneumonia severity index score (143.1±41.1 versus 98.2±54.6; P=0.028), and despite fewer embolic complications, there was a trend toward a significantly higher mortality rate (31% versus 0%; P=0.052). Two community-acquired isolates cultured in the setting of intravenous drug use were methicillin-resistant, and no isolates were positive for Panton-Valentine leukocidin. There was evidence of relatedness involving 44% of the HCAP isolates by pulsed-field gel electrophoresis analysis.

CONCLUSION: HCAP accounts for a significant number of cases that, when using traditional definitions, would be classified as CAP. Severity of illness and mortality was excessive within the HCAP group. There was evidence of relatedness and spread of common strains in the HCAP cohort. The present study supports recommendations for treatment guidelines directed toward the entity of HCAP and the empirical coverage of S aureus among certain high-risk groups.