Analysis of clinical characteristics and epidemic genotypes of children with Mycoplasma pneumoniae pneumonia

Abstract

Objective To explore the clinical features of children infected with macrolide-resistant (MR) Mycoplasma pneumonia(MP) isolates and genetic typing of all isolates. Methods Polymerase chain reaction(PCR) of MP positive in 96 nasopharyngeal or bronchoalveolar lavage fluid (BALF) samples were collected from patients diagnosed as MP pneumonia in the Affiliated Children′s Hospital of the Capital Institute of Pediatrics from January 2013 to October 2015.Fifty-five cases were male, 41 cases were female; 19 cases(19.8%) were 1 to 3 years old, 18 cases(18.7%) were more than 3 to 5 years old, 59 cases(61.5%) were more than 5 to 13 years and 2 months old.These samples were tested for MR associated mutations in the 23S rRNA of MP, and were divided into the MR group and the macrolide-sensitive (MS) group.Furthermore, the genotype of all the isolates were performed by conducting P1- restriction fragment length polymorphism(P1-RFLP) analysis and multiple-locus variable-number tandem-repeat analysis(MLVA) method.The clinical characteristics including the age, gender, hospitalization duration, symptoms, signs, fever duration, fever duration after macrolide therapy, white blood cell count, C-reactive protein (CRP), chest X-ray and/or chest computed tomography, which were compared between different groups.SPSS 11.5 software was used to analyze the statistical data.Statistical significance was determined at the 0.05 level of a two-tailed test. Results MR mutations were identified in the 23S rRNA gene in 81 specimens(84%), and the 96 specimens were divided into MR group(81 cases) and MS group(15 cases). There were statistical differences in fever duration, hospitalization duration, the incidence of complications and CRP level between the MR group and MS group (t=2.061, Z=-3.368, χ2=5.856, Z=-2.165, all P 0.05). All the 96 isolates were performed by adopting P1-RFLP typing, but 5 isolates were not typed successfully, while 81 cases(89.0%)isolates were typed as P1-Ⅰ and 10 isolates(11%) were typed as P1-Ⅱc.The hospitalization duration and the fever duration after macrolide therapy in the P1-Ⅰ were longer than the P1-Ⅱc group, and the difference was statistically significant (Z=-2.197, 2.237, all P 0.05). Seventy-three cases (90%)of P1-Ⅰ group were MR isolates, 8 cases (10%) were MS isolates; 3 cases(30%) of the P1-Ⅱc group were MR isolates, 7 cases (70%) were MS isolates.The MR isolates in P1-Ⅰ group were much more than P1-Ⅱc group.There was obvious statistical difference in the proportion of MR isolates between 2 groups(χ2=19.209, P 0.05). Seventy-four cases (90%)of the M4-5-7-2 group were MR isolates, 8 cases (10%) were MS isolates; 4 cases (36%) of the M3-5-6-2 group were MR isolates, 7 cases (64%) were MS isolates.The MR isolates in M4-5-7-2 group were much more than M3-5-6-2 group.There was obviously statistical difference in the proportion of MR isolates between 2 groups(χ2=17.022, P<0.01). Conclusions In the MR group, the children had longer fever duration and hospitalization duration, higher incidence of complications and higher CRP level than those in the MS group.The MR rates of MP in China was high.P1-Ⅰ and M4-5-7-2 are the predominate genotypes.There may be a correlation between genotype and MR. Key words: Mycoplasma pneumoniae; Drug resistance; Macrolides; Genotype