Pelton Stephen I, Huot Heather, Finkelstein Jonathan A, Bishop C J, Hsu Katherine K, Kellenberg Joan, Huang Susan S, Goldstein Richard, Hanage William P
Maxwell Finland Laboratory for Infectious Diseases, Boston University School of Medicine, Boston, MA, USA.
Pediatr Infect Dis J. 2007 Jun;26(6):468-72. doi: 10.1097/INF.0b013e31803df9ca.
The long-term effects of selective pressure from conjugate pneumococcal vaccine on the serotype distribution and antimicrobial resistance of carriage and invasive isolates of Streptococcus pneumoniae are unknown. Early changes demonstrate a reduction in vaccine serotypes and an increase in nonvaccine serotypes (NVT) among both carriage and invasive isolates. Ongoing surveillance is necessary to identify emerging invasive serotypes and antimicrobial susceptibilities.
Enhanced surveillance of invasive pneumococcal disease in Massachusetts began in October 2001 and remains ongoing. Isolates from children less than 5 are sent to the Massachusetts Department of Public Health and subsequently to the Maxwell Finland laboratory for serotyping and determination of antimicrobial susceptibility. Annual incidence rates for vaccine serotype and NVT disease are calculated using 2000 census data.
NVT caused 72%-91% of invasive pneumococcal disease annually in children less than 5 years of age between 2002 and 2005. Serotype 19A has emerged as the most frequent cause of IPD in Massachusetts. A multidrug-resistant clone (ceftriaxone, amoxicillin, azithromycin and trimethoprim-sulfamethoxazole) (MLST 320) was first identified in Massachusetts in 2005.
Three years after the introduction of pneumococcal conjugate vaccine for universal administration to children less than 2 in Massachusetts, a significant increase in invasive disease due to serotype 19A was observed. Although MLST 199 remains the most frequent sequence type among invasive isolates (of 19A), a multidrug-resistant sequence type, not previously identified in Massachusetts, has become an important cause of invasive disease. Further surveillance of the changing ecology of S. pneumoniae is necessary as a 4-year time period is not sufficient to fully evaluate the impact of PCV of pneumococcal infections.
共轭肺炎球菌疫苗产生的选择性压力对肺炎链球菌携带菌株和侵袭性分离株的血清型分布及抗菌药物耐药性的长期影响尚不清楚。早期变化显示，携带菌株和侵袭性分离株中疫苗血清型减少，非疫苗血清型（NVT）增加。持续监测对于识别新出现的侵袭性血清型及抗菌药物敏感性很有必要。
2001年10月起，马萨诸塞州加强了对侵袭性肺炎球菌疾病的监测，且仍在进行中。来自5岁以下儿童的分离株被送往马萨诸塞州公共卫生部，随后送往马克斯韦尔·芬兰实验室进行血清分型及抗菌药物敏感性测定。使用2000年人口普查数据计算疫苗血清型和NVT疾病的年发病率。
2002年至2005年期间，NVT每年导致5岁以下儿童侵袭性肺炎球菌疾病的72% - 91%。19A血清型已成为马萨诸塞州侵袭性肺炎球菌疾病最常见的病因。2005年在马萨诸塞州首次发现了一种多重耐药克隆（对头孢曲松、阿莫西林、阿奇霉素和甲氧苄啶 - 磺胺甲恶唑耐药）（多位点序列分型320）。
在马萨诸塞州对2岁以下儿童普遍接种肺炎球菌共轭疫苗三年后，观察到19A血清型导致的侵袭性疾病显著增加。尽管多位点序列分型199仍是侵袭性分离株（19A血清型）中最常见的序列类型，但一种此前在马萨诸塞州未被识别的多重耐药序列类型已成为侵袭性疾病的重要病因。由于4年时间不足以充分评估肺炎球菌共轭疫苗对肺炎球菌感染的影响，因此有必要对肺炎链球菌不断变化的生态进行进一步监测。
