小儿下呼吸道感染的细菌病原学分析

Pathogenic bacteria of childhood lower respiratory tract infection

目的下呼吸道感染是造成儿童住院的最常见疾病之一。在发展中国家，病原菌以细菌感染相对多见，而病原菌的分布特点则常因年代不同而发生变迁。该研究的目的是了解本地区小儿下呼吸道感染常见病原菌及其对常用抗生素的耐药性，为临床药物治疗提供有价值的参考。方法对2001年8月至2002年7月住院的所有下呼吸道感染患儿，常规进行深部痰培养，并用纸片扩散法、Etest法和Vitek系统进行药敏试验。结果下呼吸道感染儿共4238例，其中1181例分离到1种或1种以上致病菌，阳性率为27．9％，最常见的病原菌为肺炎链球菌、流感嗜血杆菌、肺炎克雷伯菌、大肠埃希菌和金黄色葡萄球菌，分离率分别为5．2％，5．1％，5．1％，4．0％和2．1％。女性患儿肺炎链球菌的分离率显著高于男性（x^2=4．63，P〈0．05），而肺炎克雷伯菌和金黄色葡萄球菌在男性中的分离率均高于女性（x^2=5．71，4．57，P〈0．05）。年龄分布显示，1～3岁是肺炎链球菌和流感嗜血杆菌的好发年龄段，而肺炎克雷伯菌、大肠埃希菌、金黄色葡萄球菌和阴沟肠杆菌以及非常见菌感染则在1岁以内的婴儿中多见。季节分布上，12月份至3月份是大多数细菌感染分布较集中的时段。药敏结果显示青霉素不敏感肺炎链球菌、耐氨苄西林流感嗜血杆菌、耐苯唑西林金黄色葡萄球菌和产ESBL肺炎克雷伯菌、大肠埃希菌的比率分别为55．0％，16．5％，41．2％，42．6％和4．5％。结论肺炎链球菌、流感嗜血杆菌、肺炎克雷伯菌、大肠埃希菌和金黄色葡萄球菌是小儿下呼吸道感染常见致病菌，但在不同年龄的感染率存在明显差异，治疗上应根据药敏结果选择敏感抗生素。

Objective To study the pathogenic bacteria of lower respiratory tract infection （ LRTI ）, and age and gender distribution and drug resistance of the pathogenic bacteria in children. Methods Sputum specimens for bacterial cultures were collected in sterile tubes from all of the children with LRTI who had been admitted to the Children＇s Hospital of Zhejiang University between August 2001 and July 2002. Antibiotic susceptibility tests were performed using the Vitek system, the Kirby-Bauer diffuse method and the Etest method after bacteria were identified. Results Among the 4 238 patients with LRTI during the study period, 1 181 patients were bacteria-positive, with a positive rate of 27.9%. Streptococcus pneumoniae （S. pneumoniae ） was the most common （222 strains ）, followed by Haemophilus influenzae （ H. influenzae ） （ 216 strains ） , KlebsieUa pneumoniae （ K. pneumoniae ） （ 216 strains ） , Escherichia coil （ E. coli） （ 169 strains） and Staphylococcus aureus （S. aureus） （89 strains）. The isolation rate of S. pneurnoniae in females was significantly higher than in males （6.2% vs 4.7%; P 〈0.05）. However, the isolation rates of K. pneumoniae and S. aureus in males were higher than in females （5.1% vs 4.1% and 2.5% vs 1.5% , respectively; P 〈0.05 ）. A higher incidence of LRTI due to S. pneumoniae and H. influenzae was found in the 1-3 years group, while the incidence of LRTI due to K. pneumoniae, E. coli, S. aureus and E. cloacae was higher in patients under 1 year of age. Antibiotic susceptibility tests showed that rates of penicillin-non-susceptible S. pneumoniae, ampicillin resistant H. influenzae, oxacillin-resistant S. aureus and ESBL-positive K. pneumoniae and E. coli were 55.0% , 16.5% , 41.2% , 42.6% and 4.5% , respectively. Conclusions S. pneumoniae, H. influenzae, K. pneumoniac, E. coli and S. aureus were common pathogens of LRTI in children. The infection rate varied with age and gender. Antibiotics for treating LRTI should be selected based on the drug susceptibility test.