Prevalence Of Pathogens In Patients Of Community-acquired Pneumonia And Resistance Mechanism Of Erythromycin In Streptococcus Pneumoniae

Objective To study the pathogens in community-acquired pneumonia (CAP) and improve the knowledge of atypical pathogens.Methods A prospective study was performed on 103 consecutive adult patients of mean (SD) 42.56 (20.32) years (range 18~86) with CAP between November 2001 and June 2002. 61 patients were men, 42 patients were women. Samples of acute and convalescent serum, acute urine and sputum (or throat specimens) were collected for the test. (1) Serological tests: Mycoplasma pneumoniae (MP): antibody liters to Mycoplasma pneumoniae were determined by microparticle agglutination using the commercial kit Serodia-Myco II (Fujirebio, Japan). Using this method, MP was diagnosed if there was a fourfold or greater rise or decline in antibodies in the paired serum samples. Legionella pneumophilia (LP) : antibodies to LP were detected using the indirect immunofluorescence test ( Mardx , USA). LP was considered to be the causal agent of CAP in the prescence of a fourfold or greater rise ( to 1: 128 ) or decline in IgG between paired serum samples. Chlamydia pneumoniae (CP) : CP was determined by the microimmunof luorescence method (FOCUS, USA) to detect IgG and IgA antibodies specific to Chlamydia pneumoniae, a fourfold or greater rise (to 1:32) or decline in titer for any immunoglobulin class between the paired serum samples was considered evidence that CP was the cause of CAP. (2) PCR method : For MP and CP, the primers were directed against the P1 adhesion gene and a species-specific sequence of the 16S ribosome gene respectively. In the reaction, the uracil-DNA-glycosylase (UDG) system was used to prevent carry over contamination from previous amplifications, and a specific internal control was added to detect possible inhibitors of the reaction,when inhibitors were detected, the PCR was repeated with samples which were treated with phenol-chloroform extraction, after that,detection of PCR product by gel electrophoresis. (3)Urine antigen tests: using enzyme immunoassay (EIA) (Biotest, Germany) for the detection of Legionel la antigen in urine. When OD>cut-off value, presumed positive for Legionella antigen in urine was diagnosed. This gives riseto the suspicion of an existing or past Legionella infection. (4) Bacterial culture: sputums or throat specimens were collected for culture, bacteria were isolated and identified using conventional methods.Results The aetiology of CAP was identified in 50(48.5%) patients. The distribution of atypical pathogens was as fol Iws: Mycoplasma pneumoniae 23 (22. 3%), Legionella pneumophilia 3 (2.9%), Chlamydia pneumoniae 2(1.9%). Bacterial pathogens were identified from 28 patients: streptococcus pneumoniae 12 (11.7%), Haemophilus influenzae 9(8.7%), Klebsiella pneumoniae 7(6.8%). In 6 patients (5.8%) more than one causal agent was found, 5 Mycoplasma pneumoniae were found in mixed infections .Among the 23 Patients with Mycoplasma pneumoniae, 20 cases (87%) were in 18~40 years and 13 cases (57%)occurred in November and December.Conclusions Atypical pathogens especially Mycoplasma pneumoniae have important role in CAP; streptococcus pneumoniae and Haemophilus influenzae remain the most common bacteria; mixed infection shouldnot be ignored.