| Background:Legionnaires' disease was discovered following an outbreak traced to a 1976 American Legion convention in Philadelphia, USA. In that outbreak, approximately 221 people contracted this previously unknown type of bacterial pneumonia, and 34 people died. A new pathogen was isolated from lungs of the dead next year, which was termed legionella pneumophila(Lp) in the worldwide in 1978. In China, Legionnaires' disease was firstly proved in Nanjing in 1982.There are 48 species comprising 70 distinct serogroups in Legionella currently. Approximately one half of them are associated with human diseases, and Lp is the most important one. It has been reported that about 15% of pneumonia are caused by Legionella and 90% of Legionella pneumonia are caused by Lp. Although there are now 15 serogroups of Lp ,most of all Lp pneumonia are caused by Lp serogroup 1(Lp1)- serogroup 6,especially Lp1, which caused 80% of Lp pneumonia.With the development of urbanization and wide use of modern equipment, legionella pollution had been considerably widespread. From the epidemic data ofLegionnaires' disease home and abroad, it is not difficult to draw a conclusion that the threat of legionella should not be ignored.Acute low respiratory tract infection remains the most frequent and common disease in children in our country. It accounts for 24.5%～65.2% of hospitalized children. Pneumonia is the first cause of death in children younger than 5 years old. Legionella pneumonia is an important kind of atypical pneumonia. Legionella can infect everyone of any age. Since Xiaoming Kang first report LD in China in 1982, the research of LD has been continually developing. Some local fulminant epidemic and sporadic cases of LD were occasionally reported. However, few paper have illustrated the LD in young children in China. Here, we detected and analyzed Lp infection in children younger than 5 years old with low respiratory tract infections.Objectives:1. To study the present situation of Lp infections in children younger than 5 years old with low respiratory tract infections.2. To study clinical distribution characteristics of Lp infection in children younger than 5 years old.Methods:Three hundreds hospitalized patients with the diagnosis of low respiratory tract infections from December 1,2004 to December 1,2005 in respiratory ward in our hospital were enrolled in the study. Of them, 191 were male and 109 were female ,with the mean age of 2.9 years (27days～5years). Disease duration was from one day to six months.1. Serum antibody(IgM) of Lp serogroup 1-7(Lp-IgM) was detected by ELISA.2. Urinary antigen of Lp serogroup 1(Lp-Ag) was measured by ELISA.Results:1. serum Lp-IgM: In the three hundred patients, ten cases were positive. The positive rate was 33.3%. Of the ten children, two were between 27 days and one year old, three were 1～3years old and five were 3～5 years old. The positive rates were significantly different among the three groups (1.27%vs 3.16% vs 10.64%) and tendentially increased following the increase of age ( x~2=8.47, P < 0.05). The genders did not significantly influence the positive rate with 3.67% in males and 2.75%in females. The spring and winter seasons (n=1), or summer and autum seasons (n=9) had obviously different positive rates(0.74%vs5.45%). Univariate analysis also demonstrated that the positive rate were also different between children come from town(n=7) or county(n=3) (7.53%vs1.45%).2. Lp-Ag in urine: In the three hundred patients, thirty-six cases were positive. The positive rate was 12%. Of the thirty-six children, fifteen were between 27 days and one year old, ten were 1～3years old, eleven were 3～5 years old. The positive rates were significantly different among the three groups (9.49%vs 10.53% vs 23.40%) and tendentially increased following the increase of age (x~2 = 5, P < 0.05). The genders did not significantly influence the positive rate(10.99% in males vsl3.76% in females). The spring and winter seasons (n=1), or summer and autum seasons (n=9) had obviously different positive rates (5.90%vsl6.96%). Univariate analysis also demonstrated that the positive rate were also different between children come from town(n=7) or county(n=3) (29.03%vs4.35%).3. Of the 300 children, no one was double positive for serum Lp-IgM and urine Lp-Ag. However, 254 cases were both negative for the serum Lp-IgM and urine Lp-Ag. The positive rate of serum Lp-IgM was much lower than that of urine Lp-Ag, the consistency of two specimen was very low.Conclusion1. There are certain cases of Lp infections in children younger than 5 years old with low respiratory tract infections. The positive rate of serum Lp-IgM and urine Lp-Ag was 3.33% and 12% respectively in this cohort.2. The infection rates are different among children of different ages and tendentially increased following the increase of age. There seems to be higher positive rates in summer and autumn season than in winter and spring season. Children coming from town also have a higher positive rate than those coming from country. |
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