OBJECTIVEMycoplasma pneumoniae (Mp) infection is one of major causes of community-acquired pneumonia. Isolation and culture of Mp are very difficult, fluorescent quantitative PCR is a new technique to detect Mp. The aim of this study was to explore the diagnostic value of fluorescent quantitation PCR for Mp infection.

METHODMp-DNA from the deep respiratory tract secretion of children suffering from pneumonia was tested by a fluorescent quantitative PCR. Totally 256 cases who were positive for Mp DNA were enrolled into this study, 164 (64.1%) were male, 92 (35.9%) were female; the age ranged from 9 days to 16 years. All the patients also had results of Mp-IgM test. These patients were divided into 2 groups according to the result of Mp-IgM detection, namely, Mp-IgM positive and negative groups. Area under the roc curve (Az) was used as the index to evaluate the diagnostic value of fluorescent quantitation PCR for Mp detection. The number of Mp-DNA copies, age and course of disease of the 2 groups were also compared.

RESULTS(1) Diagnostic accuracy of fluorescent quantitative PCR for detecting Mp infection was that Az = 0.641. (2) The number of copies of the cases in Mp-IgM positive group was 5.42 +/- 1.26 [log(Mp-DNA copy/ml)], while that of Mp-IgM-negative group was 4.87 +/- 1.29 [log(Mp-DNA copy/ml), t = 3.43, P < 0.05]. (3) The age of Mp-IgM positive group was dramatically younger than Mp-IgM negative group (P < 0.001).

CONCLUSIONThe diagnostic accuracy of fluorescent quantitative PCR for mycoplasma pneumoniae (Mp) infection is low; however for children whose immunologic systems are not fully developed, this technique has some diagnostic value, and higher number of Mp-DNA copies may support diagnosis of Mp infection.

Adolescent ; Child ; Child, Preschool ; Female ; Humans ; Immunoglobulin M ; blood ; Infant ; Infant, Newborn ; Male ; Mycoplasma pneumoniae ; genetics ; immunology ; isolation & purification ; Pneumonia, Mycoplasma ; diagnosis ; Polymerase Chain Reaction ; methods

Local epidemiologic data on the etiologies of patients hospitalized with community-acquired pneumonia (CAP) is needed to develop guidelines for clinical practice. This study was conducted prospectively to determine the proportion of atypical bacterial pathogens in adults patients hospitalized with CAP in Korea between October 2001 and December 2002. Microbiological diagnosis was determined by serology for antibodies to Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneu-mophila. Nucleic acid of M. pneumoniae and C. pneumoniae in respiratory samples and Legionella antigen in urine samples were detected. The study population consisted of 126 patients (71 males, 55 females), averaging 54.6 yr (SD+/-17.8), whose paired sera were available. An etiologic diagnosis for atypical pathogens was made in 18 patients (14.3%): C. pneumoniae 9 (7.1%), M. pneumoniae 8 (6.3%), and L. pneumophila 3 patients (2.4%). Streptococcus preumoniae and other typical pathogens were isolated from 36 patients (28.6%). Of 126 patients, 16 (12.7%) were admitted to intensive care unit and atypical pathogens were identified in 5 patients (31.3%). Initial clinical features of patients with pneumonia due to atypical, typical or undetermined pathogens were indistinguishable. We conclude that atypical pathogens should be seriously considered in hospitalized patients with CAP, when initiating empiric treatment in Korea.
RNA, Ribosomal, 16S/genetics ; Prospective Studies ; Polymerase Chain Reaction ; Pneumonia, Bacterial/blood/*microbiology/urine ; Mycoplasma pneumoniae/genetics/immunology/*isolation & purification ; Middle Aged ; Male ; Legionella pneumophila/genetics/immunology/*isolation & purification ; Korea ; Humans ; Hospitalization/statistics & numerical data ; Female ; Community-Acquired Infections/microbiology ; Chlamydophila pneumoniae/genetics/immunology/*isolation & purification ; Antigens, Bacterial/urine ; Antibodies, Bacterial/blood ; Aged ; Adult