Cresti Stefania, Lattanzi Maria, Zanchi Alessandra, Montagnani Francesca, Pollini Simona, Cellesi Carla, Rossolini Gian Maria
Clinica delle Malattie Infettive, Sezione di Microbiologia, Dipartimento di Biologia Molecolare, Università degli Studi di Siena, I-53100 Siena, Italy.
Antimicrob Agents Chemother. 2002 Jun;46(6):1816-22. doi: 10.1128/AAC.46.6.1816-1822.2002.
Susceptibility to macrolides and lincosamides was investigated with 299 consecutive nonduplicate Streptococcus pyogenes clinical isolates collected over a 6-year period (1992 to 1997) from an area of central Italy. During this period, macrolide resistance rates steadily increased (from 9% in 1992 to 53% in 1997; P < 0.001). The increase was caused by isolates with a macrolide-lincosamide-streptogramin B resistance phenotype, carrying mostly erm(B) but also erm(TR) genes, that were not detected in the first 2 years and were detected with increasing prevalence (8, 5, 26, and 37%, respectively) during the following 4 years. During the same period, the prevalence of isolates with a macrolide resistance phenotype, carrying mef(A) determinants, did not vary significantly; on average it was 13%, with modest rate fluctuations in different years and no definite trend. Molecular typing revealed a remarkable clonal diversity among susceptible and resistant isolates and a notable heterogeneity of the genetic environment of the resistance genes. The analysis of clonal diversity in relation with resistance phenotypes and genotypes revealed that increased macrolide resistance rates were due to a complex interplay of different mechanisms, with a relevant contribution played by an "epidemic" spread of genetic elements carrying the erm(B) gene among the circulating streptococcal population.
对1992年至1997年6年间从意大利中部一个地区收集的299株连续非重复化脓性链球菌临床分离株进行了大环内酯类和林可酰胺类药物敏感性研究。在此期间，大环内酯类耐药率稳步上升（从1992年的9%升至1997年的53%；P<0.001）。这种上升是由具有大环内酯-林可酰胺-链阳菌素B耐药表型的分离株引起的，这些分离株大多携带erm(B)基因，但也携带erm(TR)基因，前两年未检测到，在随后4年中检测到的流行率逐渐增加（分别为8%、5%、26%和37%）。在同一时期，携带mef(A)决定簇的具有大环内酯耐药表型的分离株的流行率没有显著变化；平均为13%，不同年份有适度的波动且无明确趋势。分子分型显示敏感和耐药分离株之间存在显著的克隆多样性，耐药基因的遗传环境存在明显的异质性。对与耐药表型和基因型相关的克隆多样性分析表明，大环内酯耐药率的增加是由于不同机制的复杂相互作用，携带erm(B)基因的遗传元件在循环链球菌群体中的“流行”传播起到了相关作用。
