Rapid diagnosis of Mycoplasma pneumoniae infection in children by polymerase chain reaction

Abstract

Background and purpose: Endemic atypical pneumonia was noted in central Taiwan during 2005. The serological response to Mycoplasma pneumoniae infection was usually poor in its early course; convalescent serum was needed in most cases, which was sometimes difficult to obtain in children. Empiric antimicrobial therapy was usually initiated before serological testing. A rapid test would be useful to define the etiology and initiate appropriate management. We studied the usefulness of polymerase chain reaction (PCR) analysis for diagnosis in this setting.

Methods: This 1-year prospective study conducted during 2005 in central Taiwan enrolled 307 hospitalized children (aged 3 months to 16 years) with respiratory tract infections, some complicated with systemic manifestations, such as encephalitis and skin rash. Fifty one patients were excluded due to unavailability of data or lack of consent. PCR analysis of samples using a primer set for the P1 gene of M. pneumoniae was compared to serological testing, including particle agglutinin test and enzyme-linked immunosorbent assay.

Results: 263 throat swabs from 256 patients were available for PCR tests, and serological tests were performed in 140 children (55%) with clinical suspicion of atypical pneumonia. Eighty two children (32%) were positive by the PCR method and 76 (30%) were serologically positive. Seventy one patients (87%) with duration of disease onset of 2 to 7 days had positive PCR results. The mean age of patients with M. pneumoniae infection was 5.2 years, with 27% of patients <2 years old and 73% of patients >2 years of age. The diagnoses were as follows: pneumonia (n = 44); pneumonia complicated with pleural effusion (n = 12); bronchitis and bronchopneumonia (n = 18); asthmatic bronchitis (n = 2); croup syndrome (n = 1); pharyngitis (n = 3); and herpangina (n = 2). Coinfection with bacteria or virus was found in 21% of patients with M. pneumoniae infection.

Conclusions: The PCR method could provide earlier diagnosis of M. pneumoniae infection and was useful to identify variable clinical features of infection, especially in younger children.