[Distribution of pathogenic microorganisms and its relationship with clinical features in children with community-acquired pneumonia].

OBJECTIVE: To study the distribution of pathogenic microorganisms in different genders, age groups and seasons in children with community-acquired pneumonia (CAP) and the relationship between the distribution of pathogenic microorganisms and clinical features. METHODS: A total of 1,155 children with CAP were enrolled, among whom there were 670 boys and 485 girls, with a mean age of 3.1±2.8 years (range: one month to 14 years). Indirect immunofluorescence assay, particle agglutination test, enzyme-linked immunosorbent assay, colloidal gold method. and bacterial culture were applied to determine common respiratory pathogenic microorganisms in sputum, throat swabs, blood samples, bronchoalveolar lavage fluid, and urine. RESULTS: A total of 758 specimens (65.63%) were tested positive by pathogen detection. The top three dominant pathogens were Mycoplasma pneumoniae (MP, 43.64%), bacteria (15.12%), and respiratory syncytial virus (RSV, 9.26%), and the rate of mixed infection was 16.02%. The rates of MP infection between boys and girls with CAP were different (40.8% vs 47.6%; P<0.05). The MP detection rate was the highest in the age group of 6-14 years (77.4%) and the lowest in children younger than 1 year (11.2%), while the detection rates of bacteria and RSV were the highest in children younger than 1 year (21.2% and 17.2%, respectively). The MP detection rate was significantly higher in summer and autumn than in winter and spring, while the detection rates of bacteria and RSV in summer and autumn were significantly lower than those in winter and spring. Among children who were MP positive, fever, chills, cough, crackles were more likely to appear; children with RSV infection were more likely to have wheezes; children with bacterial infection were less likely to have cough. Serum levels of C-reactive protein and procalcitonin were associated with bacterial infection (OR=1.747 and 1.418, respectively; both P<0.05). CONCLUSIONS: MP plays a more and more important role in the pathogenic microorganisms of CAP in children. Prevalence and outbreaks of MP infection among children should be alerted in summer and autumn. There are differences in the detection rate of various pathogenic microorganisms in CAP children with various age groups. The clinical features of children with CAP caused by different pathogenic microorganisms are different.

Influence of induced ciprofloxacin resistance on efflux pump activity of Klebsiella pneumoniae.

OBJECTIVE: The efflux pump (EP) is one of the major mechanisms of antibiotic resistance in Klebsiella pneumoniae. However, there are few reports on the effect of the abuse of antibiotic use on the activity of EPs. To determine whether the use of low efficacy antibiotics has any effect on the activity of EPs and induces drug resistance in K. pneumoniae, we investigated the effect of ciprofloxacin on the activity of EPs in K. pneumoniae strains. METHODS: Sixteen susceptible K. pneumoniae strains were isolated from patients and their minimum inhibitory concentrations (MICs) of ciprofloxacin were measured in the absence and presence of the pump inhibitor carbonyl cyanide m-chlorophenyl hydrazone (CCCP). The strains were then induced with a gradient of ciprofloxacin until the MICs of the strains showed no further increase, to obtain induced resistant strains. The EP activities of the strains before and after induction were compared using EP inhibition and ethidium bromide (EtBr) accumulation assays. RESULTS: The MIC values of the strains were 16‒256 times higher after induction than before induction. In the presence of CCCP, the MIC values of 50% of the induced strains were 2‒4-fold lower than that in the absence of this inhibitor. The EtBr accumulation assay showed that the fluorescence of EtBr in the induced cells was lower than that in the cells before induction. CONCLUSIONS: EPs are widespread in susceptible and drug-resistant K. pneumoniae strains. Induction with ciprofloxacin may increase the activity of EPs in K. pneumoniae. The EtBr accumulation assay is more sensitive than the EP inhibition assay in evaluating the activity of EPs in K. pneumoniae.