耐甲氧西林金黄色葡萄球菌多重耐药基因检测

The detection of clinically relevant antibiotic resistance genes in Staphylococcus aureus

目的了解金黄色葡萄球菌(金葡菌)β内酰胺类、氨基糖苷类、大环内酯类、四环素类抗生素耐药基因的分布特点,评估耐药性基因型与表型测定法的相关性。方法聚合酶链反应(PCR)测定本地分离100株金葡菌的β内酰胺类耐药基因mecA、氨基糖苷修饰酶基因aac(6′)/aph(2′′)、aph(3′)-III、ant(4′,4′′)、大环内酯类23srRNA甲基化酶基因erm、四环素类核糖体保护蛋白基因tetM的发生率,纸片扩散法测定苯唑西林、庆大霉素、红霉素、四环素的耐药性。结果100株受试菌中mecA阳性66株(MRSA),最常见的耐药基因是erm+tetM,存在于89·4%的MRSA中,最少见的是ant(4′,4′′),存在于4·5%的MRSA中,MRSA的aac(6′)/aph(2′′)、aph(3′)-III、erm、tetM检出率分别为97·0%、72·7%、100%、89·4%,明显高于MSSA的11·8%、2·9%、44·1%、8·8%;66株MRSA中,43株(65·2%)同时检出aac(6′)/aph(2′′)、aph(3′)-III、erm、tetM4种基因,58株(87·9%)同时检出aac(6′)/aph(2′′)、erm、tetM3种基因,34株MSSA中,仅2株(5·9%)同时检出aac(6′)/aph(2′′)、erm、tetM3种基因;苯唑西林、庆大霉素、红霉素、四环素与其相应的耐药基因mecA、aac(6′)/aph(2′′)、erm、tetM的符合率分别为96%、99%、96%、84%,81株红霉素表型耐药菌中79株(97·5%)为大环内酯-林可霉素-链霉菌素B(MLSB)结构型耐药。结论耐药基因在金葡菌中均可检出,金葡菌对氨基糖苷类、大环内酯类、四环素类抗生素耐药与苯唑西林耐药紧密相关,大环内酯类主要是结构型耐药,基因型与表型测定有较高的符合率。

Objective In order to determine the prevalence and distribution of the clinically relevant antibiotic resistance genes in Staphylococci aureus and the correlation between genotypic and phenotypic analysis for four drugs. Methods Six clinically relevant antibiotic resistance genes of Staphylococcus aureus including the methicillin resistance gene mecA, the aminoglycoside resistance gene aac （6′）/aph （ 2″）, aph （ 3 ′） -Ⅲ, ant （ 4′, 4″ ） , the macrolide-lincosamide-streptogramin B resistance gene crm and the tetracycline resistance gene tetM were detected by polymerase chain reaction （PCR） methods , resistance of oxacillin, gentamicin, erythromycin, tetracycline were assayed by standard disk diffusion tests. Results Amongst 100 unrelated isolates of S. aureus the most prevalent resistance gene was erm ＋ tetM,found in 89. 4% of MRSA, The least common was ant（4′, 4″） occurring in 4. 5% of MRSA and 0 of MSSA;The prevalence of all six genes in MRSA was significantly greater than that in MSSA isolates;In 66 MRSA, 43 （65.2%） possess aac （ 6′ ）/aph （ 2″ ）, aph （ 3′ ）-Ⅲ, erm and tetM, 58 （ 87.9% ） harbour aac （6′）/aph（2″） ,erm and tetM,but no resistance gene is detected in 17 （50%） of 34 MSSA; There was a very good correlation between the genotypic and phenotypic analysis for most of these 100 strains , showing the following correlations： 99% for gentamicin resistance, 96% for oxacillin resistance, 96% for erythromycin resistance, and 84% for tetracycline resistance; Of 81 crythromycin-resistant S. aureus isolates, 79 （97.5%） demonstrated constitutive resistance to clindamycin, while only 2 showed inducible resistance. Conclusion In S. aureus, resistance to aminoglycosides ,macrolide and tetracycline was closely associated with methicilhn resistance.