Fey P D, Saïd-Salim B, Rupp M E, Hinrichs S H, Boxrud D J, Davis C C, Kreiswirth B N, Schlievert P M
Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA.
Antimicrob Agents Chemother. 2003 Jan;47(1):196-203. doi: 10.1128/AAC.47.1.196-203.2003.
Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is a growing public health concern that has been associated with pediatric fatalities. It is hypothesized that the evolution of CA-MRSA is a recent event due to the acquisition of mec DNA by previously methicillin-susceptible strains that circulated in the community. This study investigated the genetic relatedness between CA-MRSA, hospital-associated MRSA (HA-MRSA), and nonmenstrual toxic shock syndrome (nmTSS) isolates. Thirty-one of 32 CA-MRSA isolates were highly related as determined by pulsed-field gel electrophoresis and spa typing yet were distinguishable from 32 HA-MRSA strains. The 31 related CA-MRSA isolates produced either staphylococcal enterotoxin B (n = 5) or C (n = 26), and none made TSS toxin 1. All CA-MRSA isolates tested contained a type IV staphylococcal cassette chromosome mec (SCCmec) element. In comparison, none of the HA-MRSA isolates (n = 32) expressed the three superantigens. Antibiotic susceptibility patterns were different between the CA-MRSA and HA-MRSA isolates; CA-MRSA was typically resistant only to beta-lactam antibiotics. Six of twenty-one nmTSS isolates were indistinguishable or highly related to the CA-MRSA isolates. MnCop, an nmTSS isolate obtained in Alabama in 1986, was highly related to the CA-MRSA isolates except that it did not contain an SCCmec element. These data suggest that CA-MRSA strains may represent a new acquisition of SCCmec DNA in a previously susceptible genetic background that was capable of causing nmTSS. CA-MRSA poses a serious health risk not only because it is resistant to the antibiotics of choice for community-acquired staphylococcal infections but also because of its ability to cause nmTSS via superantigen production.
社区获得性耐甲氧西林金黄色葡萄球菌（CA-MRSA）是一个日益引起公众健康关注的问题，且与儿童死亡有关。据推测，CA-MRSA的进化是一个近期事件，是由于社区中先前对甲氧西林敏感的菌株获得了mec DNA所致。本研究调查了CA-MRSA、医院获得性MRSA（HA-MRSA）和非经期中毒性休克综合征（nmTSS）分离株之间的遗传相关性。通过脉冲场凝胶电泳和spa分型确定，32株CA-MRSA分离株中有31株高度相关，但与32株HA-MRSA菌株可区分。31株相关的CA-MRSA分离株产生葡萄球菌肠毒素B（n = 5）或C（n = 26），无一产生TSS毒素1。所有测试的CA-MRSA分离株都含有IV型葡萄球菌盒式染色体mec（SCCmec）元件。相比之下，HA-MRSA分离株（n = 32）均未表达这三种超抗原。CA-MRSA和HA-MRSA分离株的抗生素敏感性模式不同；CA-MRSA通常仅对β-内酰胺类抗生素耐药。21株nmTSS分离株中有6株与CA-MRSA分离株无法区分或高度相关。1986年在阿拉巴马州获得的nmTSS分离株MnCop与CA-MRSA分离株高度相关，只是它不含有SCCmec元件。这些数据表明，CA-MRSA菌株可能代表了在先前易感的遗传背景中对SCCmec DNA的新获得，这种遗传背景能够导致nmTSS。CA-MRSA构成严重的健康风险，不仅因为它对社区获得性葡萄球菌感染的首选抗生素耐药，还因为它能够通过产生超抗原导致nmTSS。
