Diagnosis of Legionnaires’ Disease and Detection of Legionella from Environment

Yu-Lan Wang, Li-Rong Cheng, Jei-Kai Tan, Chuen-Sheue Chiang

2012 Vol.28 NO.11

Correspondence Author： Yu-Lan Wang

Abstract：

Legionnaires’ disease is a life-threatening lung infection commonly seen in patients of community-acquired and hospital-acquired pneumonia. The key methods in determination of Legionnaires’ disease are to conduct appropriate microbiological diagnosis. However, there is no single laboratory method that being sensitive, specific, and rapid enough, simultaneously. Therefore, most of the laboratories conducting testing for Legionnaires’ disease usually employ multiple methods for multiple specimens from a single patient and make decision about the choice of the methods on the basis of the epidemiological characteristics of Legionnaires’ disease in their regions, and the understanding of the characters and limitations of the methods. The testing methods and the diagnostic criteria for confirmation of Legionnaires’ disease currently used are mostly the same among countries in the world, except that the diagnostic criteria for serological test are different among them. The annual number of reported Legionnaires’ disease cases in Taiwan ranged from 550 to 1,700 during 2000 and 2012 with 40 to110 confirmed cases. The average male to female ratio of confirmed cases was 2.9. The 70 years and older age group recorded the highest number of confirmed cases. An average of 68% of confirmed cases were determined by urinary antigen test and 25% by serological test. The strains of Legionella spp. were isolated from the specimens of 36% of confirmed cases. The positive rates for PCR assay were higher than that for culture. The PFGE pattern analysis indicates that 22 strains isolated from clinical specimens of confirmed cases have the same genotype as those from the corresponding environmental specimens since the PFGE assay was applied to the investigation of environmental sources in 2005. Owing to the difficulties in laboratory tests, the number of Legionnaires’ disease cases diagnosed has probably been much less than that really occurred. To be able to rapidly and correctly diagnose a patient with Legionnaires’ disease is a key step in reducing the severity and mortality of the disease. Therefore, the future development in diagnosis of Legionnaires’ disease will focus on the development and application of rapid test technologies, and the strategies for performing laboratory test would be to apply multiple tests simultaneously with multiple specimens from a single case to elevate the sensitivity of the laboratory diagnostic tests.