Sudağidan Mert, Cavuşoğlu Cengiz, Bacakoğlu Feza
Izmir Yüksek Teknoloji Enstitüsü, Biyoteknoloji ve Biyomühendislik Anabilim Dali, Biyoteknoloji ve Biyomühendislik Merkezi Araştirma Laboratuvari, Izmir.
Mikrobiyol Bul. 2008 Jan;42(1):29-39.
Staphylococci are the most important agents of nosocomial infections originating from biomaterials. The aim of this study was to investigate the presence of virulence genes and their phenotypic expressions in 11 methicillin-resistant Staphylococcus aureus strains isolated from the surfaces of clinically used biomaterials of 48 thorasic intensive-care unit patients. By the use of specific primers, the presence of genes encoding the attachment and biofilm production (icaA, icaC, bap), methicillin resistance (mecA), enterotoxins A-E (sea, seb, sec, sed, see), toxic shock syndrome toxin (tst), exfoliative toxins A and B (eta and etb), alpha- and beta-hemolysins (hla and hlb), staphylococcal exotoxin-like protein-1 (set1), proteases (sspA, sspB, aur, serine proteaz gene), lipase (geh) and the regulatory genes (sarA and agrCA) were investigated by polymerase chain reaction (PCR). The phenotypic properties of the isolates such as biofilm formation, antibiotic susceptibility, extracellular protease and lipase production were also evaluated. None of the isolates were found to be biofilm and/or slime producers, however, all strains were found to have icaA gene which is responsible for biofilm formation. Nevertheless the presence of icaC and bap genes that are also responsible for biofilm formation were not detected. All the strains have had mecA gene and were resistant to oxacillin, penicilin G and gentamicin, while 10 were also resistant to erythromycin and nine were also resistant to ofloxacin. The isolates were susceptible to vancomycin, teicoplanin and co-trimoxazole. Screening of toxin and regulatory genes revealed that all the strains harboured sea, set1, hla, hlb and sarA genes. The phenotypic tests for the determination of extracellular protease production revealed that all the strains formed very weak zones on skim milk and milk agar plates, and yielded negative results on casein agar plates. Furthermore, all strains were found to harbour sspA, sspB, aur and serine protease genes. Tween 20, Tween 80 and tributyrin containing media were used to detect lipase production and all strains gave late-positive results (on the third day of incubation), although they all lacked for lipase gene (geh). As a result, S. aureus strains isolated from biomaterial surfaces yielded positivity for some of the tested virulence genes, of which some of them have not been expressed phenotypically. Although there were some limitations in the study, it could be concluded that the presence of these virulence genes in S. aureus strains might be considered as potential threats especially in intensive care unit patients.
葡萄球菌是源自生物材料的医院感染最重要的病原体。本研究的目的是调查从48例胸科重症监护病房患者临床使用的生物材料表面分离出的11株耐甲氧西林金黄色葡萄球菌菌株中毒力基因的存在情况及其表型表达。通过使用特异性引物，利用聚合酶链反应（PCR）研究编码黏附及生物膜形成（icaA、icaC、bap）、耐甲氧西林（mecA）、肠毒素A-E（sea、seb、sec、sed、see）、中毒性休克综合征毒素（tst）、剥脱毒素A和B（eta和etb）、α-和β-溶血素（hla和hlb）、葡萄球菌类毒素样蛋白-1（set1）、蛋白酶（sspA、sspB、aur、丝氨酸蛋白酶基因）、脂肪酶（geh）以及调控基因（sarA和agrCA）的基因的存在情况。还评估了分离株的表型特性，如生物膜形成、抗生素敏感性、细胞外蛋白酶和脂肪酶产生情况。未发现分离株是生物膜和/或黏液产生菌，然而，所有菌株均发现有负责生物膜形成的icaA基因。尽管如此，未检测到同样负责生物膜形成的icaC和bap基因。所有菌株均有mecA基因，对苯唑西林、青霉素G和庆大霉素耐药，而10株对红霉素耐药，9株对氧氟沙星耐药。分离株对万古霉素、替考拉宁和复方新诺明敏感。毒素和调控基因筛查显示，所有菌株均含有sea、set1、hla、hlb和sarA基因。用于测定细胞外蛋白酶产生的表型试验显示，所有菌株在脱脂乳和乳琼脂平板上形成的透明圈非常微弱，在酪蛋白琼脂平板上结果为阴性。此外，所有菌株均发现含有sspA、sspB、aur和丝氨酸蛋白酶基因。使用含吐温20、吐温80和三丁酸甘油酯的培养基检测脂肪酶产生情况，所有菌株均在培养第三天给出延迟阳性结果，尽管它们均缺乏脂肪酶基因（geh）。结果，从生物材料表面分离出的金黄色葡萄球菌菌株对一些测试的毒力基因呈阳性，其中一些基因未在表型上表达。尽管本研究存在一些局限性，但可以得出结论，金黄色葡萄球菌菌株中这些毒力基因的存在可能被视为潜在威胁，尤其是在重症监护病房患者中。
