Detection of M. pneumoniae DNA and specific antibodies in relation to duration of illness

Abstract

INTRODUCTION: M. pneumoniae is the causative agent of primary atypical pneumonia. Patients mount IgM and IgG antibody responses, which provide useful diagnostic markers. Tests for specific antibodies-and DMA amplification by poiymerase chain reaction (PCR) in respiratory samples are now widely used for this infection. The timing of specimen collection is the one most important component to influence test sensitivity, amongst other test parameters. AIM: To determine optimum sampling time for detection of M. pneumoniae specific IgG/IgM antibodies and DNA by PCR. DESIGN, SETTING AND METHOD: A prospective clinical study was carried out involving 418 adult patients in Colombo North Teaching Hospital, Ragama and Chest Hospital, Welisara. (Pneumonia -97, acute bronchitis - 183, pharyngitis - 138). M. pneumoniae specific IgG and IgM were tested in paired sera using ELISA kits (IBL-Hamburg-Germany). PCRfor M. pneumoniae DNA was done for serologically positive and serologically negative patients. Each positive result was analysed in relation to duration of illness. RESULTS: IgM was detected in 37.5% (3/8) of patients on days 1-10 , 37.5% (3/8) on, days 11-20 , 12.5% (1/8) days 21 -30 and 12.5% (1/8) days 31 -40 post onset of illness (poi). IgG was detected in 48% (11/23) of patients on days 11-20, 22% (5/23) days 21-30 poi. M. pneumoniae DNA was detected in 94% (16/17) during the first 15 days of illness. Three seronegative patients (3/4, 75%) were negative for M. pneumoniae DNA >15 days poi. CONCLUSION: IgM response, higher during the first 20 days of illness than IgG which was detected during days 11-20, post onset of illness. M. pneumoniae DNA was detected within the first two weeks of illness.