1999-2010 年期间，从墨西哥和美国的侵袭性和非侵袭性感染中分离出的耐红霉素酿脓链球菌的表型和基因型。
Phenotypes and genotypes of erythromycin-resistant Streptococcus pyogenes strains isolated from invasive and non-invasive infections from Mexico and the USA during 1999-2010.
机构信息
Molecular Microbiology Laboratory, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Sierra Mojada 800, Col. Independencia, Código Postal 44340 Guadalajara, Jalisco, Mexico.
出版信息
Int J Infect Dis. 2012 Mar;16(3):e178-81. doi: 10.1016/j.ijid.2011.11.005. Epub 2012 Jan 2.
OBJECTIVE
To compare the prevalence, phenotypes, and genes responsible for erythromycin resistance among Streptococcus pyogenes isolates from Mexico and the USA.
METHODS
Eighty-nine invasive and 378 non-invasive isolates from Mexico, plus 148 invasive, 21 non-invasive, and five unclassified isolates from the USA were studied. Susceptibilities to penicillin, erythromycin, clindamycin, ceftriaxone, and vancomycin were evaluated according to Clinical and Laboratory Standards Institute (CLSI) standards. Phenotypes of erythromycin resistance were identified by triple disk test, and screening for mefA, ermTR, and ermB genes was carried out by PCR.
RESULTS
All isolates were susceptible to penicillin, ceftriaxone, and vancomycin. Erythromycin resistance was found in 4.9% of Mexican strains and 5.2% of USA strains. Phenotypes in Mexican strains were 95% M and 5% cMLS; in strains from the USA, phenotypes were 33.3% iMLS, 33.3% iMLS-D, and 33.3% M. Erythromycin resistance genes in strains from Mexico were mefA (95%) and ermB (5%); USA strains harbored ermTR (56%), mefA (33%), and none (11%). In Mexico, all erythromycin-resistant strains were non-invasive, whereas 89% of strains from the USA were invasive.
CONCLUSIONS
Erythromycin resistance continues to exist at low levels in both Mexico and the USA, although the genetic mechanisms responsible differ between the two nations. These genetic differences may be related to the invasive character of the S. pyogenes isolated.
目的
比较来自墨西哥和美国的酿脓链球菌分离株中红霉素耐药的流行率、表型和相关基因。
方法
研究了来自墨西哥的 89 株侵袭性和 378 株非侵袭性分离株，以及来自美国的 148 株侵袭性、21 株非侵袭性和 5 株未分类分离株。根据临床和实验室标准协会（CLSI）标准评估青霉素、红霉素、克林霉素、头孢曲松和万古霉素的敏感性。通过三联纸片试验鉴定红霉素耐药表型，并通过 PCR 筛选 mefA、ermTR 和 ermB 基因。
结果
所有分离株均对青霉素、头孢曲松和万古霉素敏感。4.9%的墨西哥菌株和 5.2%的美国菌株对红霉素耐药。墨西哥菌株的表型为 95%M 和 5%cMLS；美国菌株的表型为 33.3%iMLS、33.3%iMLS-D 和 33.3%M。来自墨西哥的菌株携带红霉素耐药基因 mefA（95%）和 ermB（5%）；来自美国的菌株携带 ermTR（56%）、mefA（33%）和无（11%）。在墨西哥，所有红霉素耐药菌株均为非侵袭性，而美国菌株中 89%为侵袭性。
结论
尽管两国的遗传机制不同，但红霉素耐药在墨西哥和美国都继续以低水平存在。这些遗传差异可能与酿脓链球菌的侵袭性特征有关。
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