Consider Legionnaires Disease in Pneumonia
WASHINGTON — Acute care hospitals were the most common source of health care-associated legionnaires disease reported to the Centers for Disease Control and Prevention during 2005–2007.
In that period, 94 cases of clinically compatible illness with laboratory evidence of legionellosis infection occurring within 10 days of inpatient health care exposure were reported to the CDC's supplemental legionnaires disease surveillance system (www.cdc.gov/legionella
Acute care hospitals accounted for 88% of the reports, while long-term care and rehabilitation facilities contributed to 12%. Six of the total 41 facilities had clusters, ranging from two to four cases, indicating a “missed opportunity for prevention,” Dr. Lauri A. Hicks and her associates reported in a poster at the jointly held annual Interscience Conference on Antimicrobial Agents and Chemotherapy and annual meeting of the Infectious Diseases Society of America.
Mean age of the patients was 61 years (range, 1–87), two-thirds were male, and most were white. The case fatality rate was high: 28 of 82 patients (34%) for whom the information was reported died of the infection.
Urine antigen was used to diagnose 71 (76%) of the cases, followed by culture in 11 (12%), direct fluorescent antibody in 3 (3%), and multiple methods in 9 (10%). It's important to obtain a respiratory specimen for Legionella in all potential cases in addition to the urine sample, because urine antigen testing is specific to L. pneumophila serogroup 1 and will not detect legionnaires disease caused by other Legionella species or serogroups, said Dr. Hicks and her associates of the CDC's National Center for Immunization and Respiratory Diseases.
Culture should also be used in addition to the urine antigen test because it allows for matching of clinical and environmental isolates so that the source can be identified and remediated. “A diagnosis of [legionnaires disease] should be considered in cases of health care-associated pneumonia. … Health care facility plans to systematically identify and reduce the environmental conditions that are conducive to Legionella growth may improve prevention,” the investigators said.
Dr. Hicks had no financial disclosures.
