FORCE L, SAUCA G, BARRUFET P, DE ORY F, RETH P, SALAT D, CAPDEVILA J; Interscience Conference on Antimicrobial Agents and Chemotherapy (43rd: 2003: Chicago, Ill.).

Abstr Intersci Conf Antimicrob Agents Chemother Intersci Conf Antimicrob Agents Chemother. 2003 Sep 14-17; 43: abstract no. D-1695.

Hospital de Mataro, Mataro. Barcelona, Spain.

BACKGROUND: A total of 144 patients with pneumonia related to an outbreak of Legionella pneumophila (LP) were identified during a period of 46 days on summer 2002. Mean age was 58 +/- 17, 89 were male. LP serogroup 1 was isolated in 10 patients and also in a cooling tower of the city, all strains had the same molecular profiles. METHODS: The main diagnostic criteria was the presence of positive culture, LP antigenuria, or IgG fourfold rise in titer. A single IgG titer of >/= 256 or an IgM positive result was considered to be presumptive. Antigen detection in concentrate urine (Binax) was performed in all patients, sputum culture in 20 (14%), titration of IgG antibody by indirect immunofluorescence (IIF) in 129 (90%) and in 102 (71%) paired serum samples were available, IgG by ELISA in 28%, and finally detection of IgM by IIF was done in 94%. RESULTS: Diagnosis of LP disease was definitive in 113 patients (78%), presumptive in 10 (7%) and possible in the remaining 21 patients. LP urinary antigen was positive in 109/144 (76%), IIF IgG fourfold rise in titer in 22/102 (22%), sputum culture in 10/20 (50%) and IIF IgG >/= 256 without seroconversion in 23/129 (18%). Single high IgG ELISA level was observed in 7/40 cases (18%). IgM by IIF was positive in 86/135 patients (64%) and was the single positive test in 10 cases. LP antigenuria was more frequent in patients with early positive IgM result (96% vs 70%, p<0.01), and also in patients with hypoxemia (89% vs 60, p<0.001), and severity of symptoms (88% vs 65%, p<0.005). CONCLUSIONS: LP urinary antigen showed the best sensitivity, which was increased in patients with hypoxemia and severe disease. The rate of IIF IgG fourfold rise in titer was low and only added to antigenuria 4 LP diagnosis. The sensitivity of IgG by ELISA was very low and probably should not be used in LP diagnosis. Finally IIF IgM has shown a potential ability to improve the diagnosis of LP and can be used in the investigation of pneumonia outbreaks caused by this agent

Publication Types:

• Meeting Abstracts

Keywords:

• Antigens, Bacterial
• Disease Outbreaks
• Enzyme-Linked Immunosorbent Assay
• Fluorescent Antibody Technique, Indirect
• Humans
• Legionella pneumophila
• Legionnaires' Disease
• Male
• Sensitivity and Specificity
• diagnosis
• immunology

Other ID:

• GWAIDS0025503

UI: 102265127

From Meeting Abstracts