de Lencastre H, Couto I, Santos I, Melo-Cristino J, Torres-Pereira A, Tomasz A
Laboratory of Microbiology, Rockefeller University, New York, New York 10021.
Eur J Clin Microbiol Infect Dis. 1994 Jan;13(1):64-73. doi: 10.1007/BF02026129.
Fifteen pediatric patients as well as the five nursing staff of the Burn Unit of the Hospital D. Estefania in Lisbon, Portugal, were assayed at weekly intervals over a five-month period in order to identify the nature and number of methicillin-resistant Staphylococcus aureus (MRSA) clones associated with colonization and wound infection. Methicillin resistance was confirmed by a mec-specific DNA probe. MRSA isolates were classified into chromosomal types (clones) on the basis of a variety of techniques: (i) ribotyping; (ii) restriction digestion by the endonuclease ClaI followed by Southern hybridization with the mecA-specific DNA probe and (iii) by hybridization with Tn554; and (iv) pulsed-field electrophoresis (PFE) of SmaI digests followed by (v) Southern hybridization with the mecA DNA probe. A sixth, physiological technique (population analysis) was used to define the mode of phenotypic expression of methicillin resistance in each isolate. All isolates carried a single, common polymorph (ClaI type III) of the mecA gene. Hybridization with Tn554 resolved these isolates to two novel patterns (alpha and beta), of which one (Tn554 alpha) was predominant (90%). This pattern could be further resolved to four closely related PFE types (A through D). In contrast, all isolates with the Tn554 beta pattern belonged to an additional, grossly different PFE type E. The Tn554 beta class was also unique in that these bacteria carried the mecA gene in a SmaI fragment smaller (about 170 kb) than that found in the alpha type strains (194 kb). Most isolates (83%) showed a single heterogeneous (population analysis Class 3) mode of resistance expression. The data demonstrate the full capacity of the globally rare (ClaI type III) MRSA clone for colonization and virulence. The results also document the stability of the complex heterogeneous resistance phenotype as well as the stability of the chromosomal types under conditions of in vivo carriage over a period of several months. In a few isolates the same mecA polymorph was present in several, grossly different genetic backgrounds, suggesting horizontal transfer of the mecA gene.
在五个月的时间里，对葡萄牙里斯本埃斯特法尼亚医院烧伤科的15名儿科患者以及五名护理人员进行了每周一次的检测，以确定与定植和伤口感染相关的耐甲氧西林金黄色葡萄球菌（MRSA）克隆的性质和数量。通过mec特异性DNA探针确认耐甲氧西林特性。根据多种技术将MRSA分离株分类为染色体类型（克隆）：（i）核糖体分型；（ii）用内切酶ClaI进行限制性消化，然后用mecA特异性DNA探针进行Southern杂交，以及（iii）用Tn554进行杂交；（iv）对SmaI消化产物进行脉冲场电泳（PFE），随后（v）用mecA DNA探针进行Southern杂交。第六种生理技术（群体分析）用于确定每个分离株中耐甲氧西林特性的表型表达模式。所有分离株都携带mecA基因的单一常见多态性（ClaI III型）。与Tn554杂交将这些分离株解析为两种新的模式（α和β），其中一种（Tn554α）占主导（90%）。这种模式可以进一步解析为四种密切相关的PFE类型（A至D）。相比之下，所有具有Tn554β模式的分离株都属于另一种截然不同的PFE类型E。Tn554β类也很独特，因为这些细菌携带mecA基因的SmaI片段比α型菌株（194 kb）中的片段小（约170 kb）。大多数分离株（83%）表现出单一的异质性（群体分析3类）抗性表达模式。数据证明了全球罕见的（ClaI III型）MRSA克隆的定植和毒力的全部能力。结果还记录了复杂异质性抗性表型的稳定性以及在体内携带数月的条件下染色体类型的稳定性。在少数分离株中，相同的mecA多态性存在于几种截然不同的遗传背景中，表明mecA基因的水平转移。
