Yu Sang-jie, Hu Yi-yun, Gao Wei, Wang Jin-fang, Yang Yong-hong
Department of Microbiology and Immunology, Pediatric Research Institute, Beijing Children's Hospital Affiliated to Capital University of Medical Sciences, Beijing 100045, China.
Zhonghua Er Ke Za Zhi. 2003 Sep;41(9):688-91.
Streptococcus pneumoniae is a common cause of potentially life-threatening infections such as meningitis, bacteraemia, pneumonia worldwide, for which children of preschool age are at particularly high risk. Since the late 1970s and 1980s, antibiotic resistance among pneumococci has become an emerging problem. Several multidrug-resistant clones have rapidly spread throughout the world.
(1) To investigate the prevalence of penicillin and other antibiotics nonsusceptibility among pneumococci. (2) To analyze the correlation of pbp2b amplicon profiles with penicillin resistance. (3) To serotype 31 isolates of penicillin-resistant pneumococci by latex agglutination. (4) To analyze the chromosomal relatedness of serotype 23F and 6 isolates of penicillin-resistant pneumococci by using pulsed-field gel electrophoresis (PFGE) and characterize these isolates in molecular epidemiology.
(1) Susceptibility was determined by using broth microdilution, E-test, and K-B disk. (2) The correlation of pbp2b amplicon profiles with penicillin resistance was assessed by restriction fragment length polymorphism (RFLP). (3) Serotyping of penicillin-resistant pneumococcal isolates was performed by using latex agglutination. (4) The properties of serotype 23F and 6 isolates of penicillin-resistant pneumococci were assessed by PFGE.
S. pneumoniae with increased nonsusceptibility (including intermediate strains and resistant strains) to penicillin G was 9.9% in 1997, 12.6% in 1998, 14.6% in 2000; to cefuroxime 4.2%, 1.5%, 8.2%; to cefotaxime 0.0%, 1.7%, 1.0% respectively. There were no statistically significant differences (P > 0.05). While resistance to erythromycin, trimethoprim-sulfamethoxazole and chloramphenicol increased significantly from 76.8% in 1997 to 87.4% in 2000, from 74.7% to 88.3%, and from 22.6% to 40.8%, respectively (P < 0.05). RFLP analysis of pneumococcal pbp2b-specific amplicons was effective for screening penicillin resistance. Of the 31 strains of penicillin-resistant pneumococci (MICs 0.12 - 2.0 micro g/ml) studied, 6 (19.4%) strains (MICs 0.12 - 0.19 micro g/ml) were serotype 23F and 3 (9.7%) strains (MICs 0.5 - 1.5 micro g/ml) were serotype 6. There were nearly identical susceptibility to antibiotics and identical PFGE patterns in the former, and there were different susceptibility to antibiotics and different PFGE patterns in the latter. Three serotype 6 strains had different susceptibility to antibiotics and different PFGE patterns, which suggested that those strains may be scattered.
Generally beta-lactams retained their activity against S. pneumoniae in Beijing. Resistance to erythromycin, trimethoprim-sulfamethoxazole, and chloramphenicol increased drastically. RFLP analysis of pneumococcal pbp2b-specific amplicons was effective for screening penicillin resistance. In 6 strains of serotype 23 F there were nearly identical susceptibility to antibiotics and identical PFGE patterns, which suggested the probability that there was a spread of serotype 23F isolates with low-level penicillin resistance in local area.
肺炎链球菌是全球范围内引起脑膜炎、菌血症、肺炎等潜在危及生命感染的常见病因，学龄前儿童尤其易感染。自20世纪70年代末和80年代以来，肺炎球菌的抗生素耐药性已成为一个新出现的问题。几种多重耐药克隆已在全球迅速传播。
（1）调查肺炎球菌对青霉素和其他抗生素不敏感的流行情况。（2）分析pbp2b扩增子谱与青霉素耐药性的相关性。（3）通过乳胶凝集法对31株耐青霉素肺炎球菌进行血清分型。（4）运用脉冲场凝胶电泳（PFGE）分析23F和6型耐青霉素肺炎球菌分离株的染色体相关性，并对这些分离株进行分子流行病学特征分析。
（1）采用肉汤微量稀释法、E试验和K - B纸片法测定药敏。（2）通过限制性片段长度多态性（RFLP）评估pbp2b扩增子谱与青霉素耐药性的相关性。（3）采用乳胶凝集法对耐青霉素肺炎球菌分离株进行血清分型。（4）用PFGE评估23F和6型耐青霉素肺炎球菌分离株的特性。
1997年对青霉素G不敏感（包括中介株和耐药株）的肺炎链球菌为9.9%，1998年为12.6%，2000年为14.6%；对头孢呋辛分别为4.2%、1.5%、8.2%；对头孢噻肟分别为0.0%、1.7%、1.0%。差异无统计学意义（P＞0.05）。而对红霉素、甲氧苄啶 - 磺胺甲恶唑和氯霉素的耐药率从1997年的76.8%显著增至2000年的87.4%，从74.7%增至88.3%，从22.6%增至40.8%（P＜0.05）。肺炎球菌pbp2b特异性扩增子的RFLP分析对筛选青霉素耐药性有效。在研究的31株耐青霉素肺炎球菌（MIC为0.12～2.0μg/ml）中，6株（19.4%）（MIC为0.12～0.19μg/ml）为23F血清型，3株（9.7%）（MIC为0.5～1.5μg/ml）为6血清型。前者对抗生素的敏感性几乎相同且PFGE图谱相同，后者对抗生素的敏感性不同且PFGE图谱不同。3株6血清型菌株对抗生素的敏感性不同且PFGE图谱不同，提示这些菌株可能是散在的。
总体而言，β - 内酰胺类在北京对肺炎链球菌仍保持活性。对红霉素、甲氧苄啶 - 磺胺甲恶唑和氯霉素的耐药性急剧增加。肺炎球菌pbp2b特异性扩增子的RFLP分析对筛选青霉素耐药性有效。在6株23F血清型菌株中，对抗生素的敏感性几乎相同且PFGE图谱相同，提示当地可能存在低水平青霉素耐药的23F血清型分离株传播的可能性。
