Surveillance of serotype distribution of Streptococcus pneumoniae isolated from children with pneumonia in children's hospitals located in Beijing,Shanghai,Guangzhou and Shenzhen

Objective To investigate the situation of serotype distribution of Streptococcus pneumoniae(S.pneumoniae) isolated from Chinese children hospitalized for pneumonia and to evaluate coverage rate of pneumococcal conjugate vaccine in the isolates,especially of the 7-valent pneumococcal conjugate vaccine(PCV7,covering the serotype 4,6B,9V,14,18C,19F,and 23F).Methods From February 16,2006 to February 16,2007,the following four centres,located in different parts of mainland China,took part in the study:Beijing Children's Hospital,Beijing(Beijing);Pediatric Hospital of Fudan University,Shanghai(Shanghai),Guangzhou Children's Hospital,Guangzhou(Guangzhou) and Shenzhen Children's Hospital,Shenzhen(Shenzhen).Children less than 5 years old with clinical pneumonia,who were admitted to the in-patient department of the four hospitals,were enrolled in the study after the informed consents were obtained from parents or legal guardian.Clinical pneumonia was defined as the subjects who had at least three of the followings:fever(temperature ≥ 38.0 ℃),tachypnea(≥ 50 breaths per minute for infants,or ≥ 40 breaths for children 12-60 months old),cough,auscultation findings indicative of lower respiratory disease(including rhonchi,crackles,or bronchial breath sounds),and/or chest indrawing.Hypopharyngeal aspirates specimens were collected from the enrolled children and were sent to a local laboratory for bacterial culture.The pneumococcal isolates from aspirates were determined for the serotype using type-specific sera,while the other ones from blood,cerebrospinal fluid,pleural fluid in medical practice.All data were sent to the department for Clinical Data Management Statistical Analysis of APEX China Co.,Ltd.and were analysed with the software SAS version 8.2.The χ2 test and Fisher's accurate probability method was performed for comparing the proportions.Results A total of 279 isolates of S.pneumoniae were recovered from respiratory aspirate and pleural fluid.The isolation rate of S.pneumoniae in deep respiratory aspirate was 9.7%(278/2 865).Serotype 19F was the most frequent type observed(60.6%).Other frequently observed serotypes in decreasing order of frequency,were serotypes 19A(9.7%),23F(9.3%) and 6B(5.4%).Any of the other identified types were found in less than 10 strains.The frequency of serotype distribution also showed difference among the four cities.The most remarkable one was serotype 19F covered only 28.6%(18/63) in Beijing in compared with 62.2%-75.45% isolates in the other three cities(χ2=38.71,P0.001).The serotype 19A,which was not covered by the PCV7,was the second commonest type and was very frequent in Beijing(20.6%,13/63) and Shanghai(16.9%,11/65).Of all these isolates,81.0%(226/279) were covered in the PCV7.The coverage rates of PCV7 among cities:only 46.0%(29/63) in Beijing,while 80.0%(52/65),98.4%(60/61) and 94.4%(85/90) in Shanghai,Guangzhou and Shenzhen,respectively(χ2=72.62,P0.001).Compared to the PCV7,the 9-,10-,and 11-valent vaccine coverage rates did not increase significantly because the additional serotypes 1,3,5,or 7F were isolated rarely while the 13-valent vaccine coverage rates had little increase in Guangzhou and Shenzhen,but 18.6% and 28.6% increase in Beijing(χ2=10.74,P0.01) and Shanghai(χ2=11.53,P0.01) as the additional serotype 19A was common.Conclusions Sertotypes 19F,19A,23F and 6B were the common types among the pneumococcal strains isolated from Chinese children hospitalized for pneumonia.The case that the PCV7 could cover most of the isolates suggested the preventive effect of the vaccine on penumococcal infection was valid at present in China.