| BackgroundMycoplasmas are cell wall-free organisms. Their sizes are between viruses and bacteria. They are the smallest prokaryotic microbes that are capable of growing in lifeless media. Fifteen species of mycoplasmas have been isolated from human body. Among them, Mycoplasma pneumoniae (M pneumoniae) is confirmed as a human respiratory tract infection pathogen. Although M. pneumoniae was isolated from sputum of an acute pneumonia patient in 1944 for the first time, not until 1963 was the organism ascertained as a pathogen. M. pneumoniae is an extracellular parasitic pathogen which contains RNA and DNA with double strands circular genome DNA. As a human pathogen, M. pneumoniae binds to respiratory tract epithelial cells with the attachment organelle at one end.M. pneumoniae can be transmitted through aerosols from person to person. It is a common pathogen causing respiratory tract infection in human, especially children and adolescents. Besides respiratory tract infection, M. pneumoniae also cause multiple system complications and immune dysfunction or immune damage. M. pneumoniae pneumonia (MPP) occupies the majority of M. pneumoniae infection, accounting for 1/3 of non bacterial pneumonia, or 10%-30% of pneumonia. Incidence of MPP increased in recent years. Refractory or critical MPP cases also increased, which did great harm to immune compromised population such as children and the old. Incidence of MPP changes seasonally with regional differences. This study aims to reveal the epidemiology of MPP by recording MPP cases in hospitalized children in Hangzhou in consecutive 3 years, and to reveal the relationship of epidemiology of MPP and meteorological factors by studying epidemiological characteristics of MPP and the meteorological factors.ObjectiveTo study the epidemiological characteristics of MPP in children in Hangzhou and its relationship to the meteorological factors.MethodsM. pneumoniae DNA in nasopharyngeal aspirate was detected by PCR in hospitalized children with pneumonia from January 2007 to December 2009.M. pneumoniae DNA positivity rates of different years, seasons and ages were compared by chi-square test. Relation of positivity rates and meteorological data including monthly mean air pressure (hPa), mean air temperature (℃), mean relative humidity (%), precipitation (mm) and rain days were analyzed by linear correlation and linear regression.Results1. From 2007 to 2009, in 14799 pneumonia cases 2744 (18.5%) were M. pneumoniae DNA positive. Of them,1610 (16.9%) male and 1134 (21.4%) female were positive. The positivity rate of female was higher than male with significant difference (χ2=45.68, p<0.001). Positivity rates of≤1 year group,～3 year group,～7 year group and>7 year group were 9.8%,21.1%,44.4% and 61.6%, respectively. Positivity rate increased as age grew with statistical trend (linear trend chi-square testχ2=46.72, p＜0.001).2. In descending order, positivity rates of summer, autumn, spring, and winter were 27.8%,23.9%,18.0% and 11.6%, respectively with statistical differences (χ2=372.75, p＜0.001). Positivity rate of summer was higher than that of autumn (χ=11.23, p＜0.001). Positivity rate of autumn was higher than that of spring (χ2=35.50, p＜0.001). Positivity rate of spring was higher than that of winter (χ2=74.43, p<0.001). The peak of M. pneumoniae pneumonia occurred on 5th, July in midsummer by circular statistical analysis (r=0.0599,p＜0.001).3. The positivity rates of 2007 to 2009 were 12.9%,19.3% and 23.6%, respectively. The positivity rates increased every year with statistical trend (linear trend chi-square testχ2=13.72,p＜0.001).4. In the five meteorological factors, monthly mean air temperature and monthly mean air pressure were linearly correlated to M. pneumoniae DNA positivity rate. There existed positive correlation between positivity rate and monthly mean air temperature (r=0.83, p＜0.001), with regression equation of M. pneumoniae DNA positivity rate (%) =5.875+0.830×monthly mean air temperature (℃). There existed negative correlation between positivity rate and monthly mean air pressure (r=-0.772, p＜0.001),with regression equation of M. pneumoniae DNA positivity rate (%)=801.454-0.772×monthly mean air pressure (hPa).Conclusions1. M. pneumoniae DNA positivity rate increased as age grew, with the highest in school children. The female had higher positivity rate than male.2. In Hangzhou, M. pneumoniae pneumonia was prevalent in summer and autumn with a peak in summer. 3. The positivity rate increased from 2007 to 2009 with a maximal rate in 2009.4. High air temperature and low air pressure were two meteorological factors effecting M. pneumoniae pneumonia prevalence. |
PDF Full Text Request