纸片扩散法检测耐甲氧西林葡萄球菌的临床应用评价

目的 评价苯唑西林、头孢西丁两种药敏纸片检测耐甲氧西林葡萄球菌（MRS）的准确性.方法 以PCR方法检测mecA基因作参考,用纸片扩散法（K-B法）检测163株葡萄球菌对苯唑西林、头孢西丁两种药物的敏感性,比较两种纸片检测MRS的敏感性、特异性和预期率.结果 73株金黄色葡萄球菌和30株凝固酶阴性的葡萄球菌mecA基因检测阳性,头孢西丁检测金黄色葡萄球菌和凝固酶阴性的葡萄球菌的敏感性、特异性、阳性预期率和阴性预期率分别为97.4%、94.1%、97.4%94.1%;95.1%、100%、100%、88.9%.苯唑西林检测金黄色葡萄球菌和凝固酶阴性的葡萄球菌的敏感性、特异性、阳性预期率和阴性预期率分别为100%、58.8%、84.8%、100%;93.4%、89.1%、91.9%、91.1%.结论 头孢西丁比苯唑西林特异性更强但敏感性不够,二者联合使用更有助准确预测葡萄球菌对甲氧西林耐药性.     

头孢西丁纸片扩散法检测耐甲氧西林金黄色葡萄球菌的研究

目的评价头孢西丁纸片扩散法检测耐甲氧西林金黄色葡萄球菌(MRSA)的准确性. 方法头孢西丁、苯唑西林药敏纸片分别采用K-B法检测 156株金黄色葡萄球菌临床分离株,同时采用PCR扩增mecA基因方法为检测MRSA的标准方法,比较两种方法的准确性. 结果 95株mecA基因阳性,61株mecA基因阴性;头孢西丁、苯唑西林药敏纸片K-B法的敏感性分别为98.9%和96.7%,特异性分别为98.4%和93.4%;头孢西丁纸片扩散法检测MRSA的敏感性和特异性高于苯唑西林纸片扩散法. 结论头孢西丁纸片扩散法是检测MRSA的可靠方法.     

头孢西丁与苯唑西林纸片法、MIC法检测耐甲氧西林葡萄球菌方法比较

目的通过头孢西丁（FOX）与苯唑西林（OXA）纸片法、肉汤稀释法（最低抑菌浓度法，MIC）检测耐甲氧西林葡萄球菌（MRS）方法比较，对FOX纸片法的可靠性和临床实用性进行评估。方法用FOX与OXA纸片扩散法、MIC法检测临床送检标本中分离的葡萄球菌属共83株。结果3种方法检测27株金黄色葡萄球菌的MRS结果均为18株，符合率为100％；检测凝固酶阴性葡萄球菌MRS MIC法的结果特异性为58.3％，OXA纸片法特异性为66．7％。结论3种方法检测金黄色葡萄球菌的MRS结果相符合；检测凝固酶阴性葡萄球菌MRS的结果MIC法和OXA纸片法特异性均低，建议用FOX纸片法代替或更正对MRS的检测结果。     

头孢西丁检测耐苯唑西林金黄色葡萄球菌

目的评价头孢西丁纸片扩散试验检测耐苯唑西林金黄色葡萄球菌(ORSA)的临床应用价值.方法用头孢西丁和苯唑西林纸片扩散试验、苯唑西林琼脂筛选试验检测临床分离的186株金黄色葡萄球菌.结果82株PBP2a阳性金黄色葡萄球菌中,头孢西丁纸片法、苯唑西林纸片法和苯唑西林琼脂筛选法分别检出ORSA81、77株和78株;104株PBP2a阴性中,头孢西丁纸片法全部为阴性,苯唑西林纸片法和苯唑西林琼脂筛选法阴性为101株和103株;以ORSA-乳胶凝集试验结果为参考标准,头孢西丁纸片法、苯唑西林纸片法和苯唑西林琼脂筛选法检测ORSA的特异性分别为100%、97.1%和99.0%,敏感性分别为98.8%、93.9%和95.1%.结论头孢西丁纸片扩散试验简便、价廉,不需要特殊的试验条件并能提高测定ORSA常规试验的可靠性,适用于临床实验室对ORSA的常规检测.     

ATB Expression微生物分析系统筛查耐甲氧西林葡萄球菌的评价

目的 通过对头孢西丁(FOX)纸片扩散法与ATB Expression微生物分析系统(苯唑西林MIC法)检测耐甲氧西林葡萄球菌(MRS)的比较,对ATB Expression分析系统筛查MRS的准确性和临床适用性进行评估. 方法用FOX纸片扩散法、ATB Expression分析系统检测医院临床送检标本中分离的204株金黄色葡萄球菌和216株凝固酶阴性葡萄球菌. 结果两种方法检测204株金黄色葡萄球菌中MRS阳性率均为84.3%,且两种方法的符合率100%.检测216株凝固酶阴性葡萄球菌的MRS时,FOX纸片法阳性率为83.6%,而仪器检测的阳性率为91.7%,仪器检测的特异性为51.4%. 结论两种方法检测金黄色葡萄球菌的MRS结果相符合;而仪器检测凝固酶阴性葡萄球菌特异性较低,建议辩证灵活运用自动化仪器,在ATB Expression系统检测的同时用FOX纸片法补充和确认MRS检测结果.     

头孢西丁纸片法检测耐甲氧西林金黄色葡萄球菌的研究

目的:研究头孢西丁纸片法筛选耐甲氧西林金黄色葡萄球菌(MRSA)的方法.方法:以PCR方法检测mecA基因为金标准,采用NCCLS推荐的头孢西丁纸片法和苯唑西林纸片法检测MRSA.结果:共分离出179株金黄色葡萄球菌,其中mecA基因阳性127株,阴性52株.用头孢西丁纸片法筛查MRSA,敏感性为99.2%,特异性为98.1%;而苯唑西林纸片法检测MRSA敏感性为97.2%,特异性为94.6%.结论:头孢西丁纸片法筛查MRSA与mecA基因检测具有一致性,其操作简便、敏感性和特异性高,可作为临床实验室检测MRSA的可靠方法.     

耐甲氧西林金黄色葡萄球菌3种检测方法的评价

目的：对耐甲氧西林金黄色葡萄球菌(MRSA)3种检测方法的可靠性和临床实用性进行评价。方法：对257株临床分离的金黄色葡萄球菌采用美国临床实验室标准委员会(NCCLS)推荐的苯唑西林纸片扩散法和头孢西丁纸片扩散法筛选MRSA，采用琼脂稀释法测定各菌株对苯唑西林的最低抑菌浓度(MIC)，并采用聚合酶链反应(PCR)检测mecA基因作为判断MRSA的“金”标准。结果：苯唑西林纸片扩散法筛检MRSA的敏感性、特异性分别为98．9％、94．5％，头孢西丁纸片扩散法筛检MRSA的敏感性、特异性分别为99．5％、100％。苯唑西林琼脂稀释法筛检MRSA的敏感性、特异性分别为98．9％、98．6％。结论：PCR技术检测MRSA具有快速、敏感和特异的特点，是一种非常有效的鉴别方法。头孢西丁纸片扩散法较苯唑西林纸片扩散法结果更可靠，可作为临床实验室检测MRSA的有效方法。     

荧光实时PCR法检测耐甲氧西林金黄色葡萄球菌的研究

目的建立检测耐甲氧西林金黄色葡萄球菌（MRSA）mecA基因的荧光实时PCR法。方法对荧光实时PCR法的实验条件进行优化,并用该法检测临床分离的109株金黄色葡萄球菌,其结果与苯唑西林纸片扩散法的结果进行比较。结果109株金黄色葡萄球菌中,荧光实时PCR法检测出mecA基因阳性37株、阴性72株;苯唑西林纸片扩散法检测出MRSA27株、MSSA82株,经配对χ^2检验,荧光实时PCR法检出率显著高于苯唑西林纸片扩散法（P〈0.01）。结论荧光实时PCR法能敏感、特异检测MRSA并可实时监测反应进程,比普通PCR法更加简便、快速,可以弥补苯唑西林纸片扩散法漏检隐匿型、临界型耐药株的不足。     

葡萄球菌属mecA基因检测与药敏结果分析

目的 探讨医院2006年分离的葡萄球菌属mecA基因检测及耐药情况,为医院耐药性监测和临床用药提供指导.方法 采用 Microscan-Autoscan-4微生物分析仪及PC12复合板鉴定葡萄球菌属并测定对药物的敏感性;E-test检测各菌株对苯唑西林的最低抑菌浓度(MIC)值;PCR检测mecA基因.结果 共分离出472株葡萄球菌属,金黄色葡萄球菌196株,其中耐甲氧西林金黄色葡萄球菌(MRSA)133株、甲氧西林敏感金黄色葡萄球菌(MSSA)63株;凝固酶阴性葡萄球菌(CNS)276株,其中耐甲氧西林凝固酶阴性葡萄球菌(MRCNS)233株、甲氧西林敏感凝固酶阴性葡萄球菌(MSCNS)43株;PCR检测出MRSA和MRCNS都具有mecA基因,耐药性高的菌株有阿莫西林(91.3%)、氨苄西林(95.6%)、青霉素(99.2%)和头孢唑林(93.5%),耐药性低的菌株有利福平(22.9%)、庆大霉素(21.7%);未发现耐万古霉素菌株.结论 医院葡萄球菌属耐药性较为严重;PCR检测mecA基因和苯唑西林MIC值具有良好相关性.     

用PCR扩增法检测耐甲氧西林葡萄球菌的mecA基因

目的：用PCR扩增法检测耐甲氧西林葡萄球菌（MRS）的mecA基因。方法：临床分离的161株葡萄球菌,应用PCR扩增法鉴定MRS的mecA基因,并与Oxacillin纸片扩散法进行比较。结果：161例葡萄球菌用Oxacillin纸片扩散法进行比较,结果：161株葡萄球菌用Oxacillin纸片扩散法和mecA基因法检测MRS有4株菌有差异,mecA基因法鉴定阴性而Oxacillin纸片扩散法鉴定为耐药株,3株纸片扩散临界耐药,mecA基因法鉴定阳性,两种方法的符合率是96．89％,结论：mecA基因检测技术可以准确、快速判定MRS,特别是在鉴定纸片扩散法临界耐药株具有优良。     

Detection of MRSA in a group of 752 strains of S. aureus using a cefoxitin disk

A set of 752 S. aureus strains including 665 fresh clinical isolates, 82 collection strains from the NRL for staphylococci and three control strains for external quality assessment were tested for susceptibility to oxacillin by three routine phenotypic methods with oxacillin (agar screening method, dilution micromethod and disk diffusion method) and a new method with a 30 micrograms cefoxitin disk. Gene mecA coding for oxacillin resistance was detected by PCR, PBP2a gene product was detected by latex agglutination. All of 218 oxacillin resistant strains--MRSA (methicillin resistant S. aureus)--gave inhibition zones of 6-19 mm around the cefoxitin disk, i.e. zones within the range set up for oxacillin resistant strains, eight out of these strains showing false oxacillin susceptibility in one or more phenotypic tests. It can be stated that the presence of an inhibition zone of < 20 mm around the 30 micrograms cefoxitin disk allows for reliable differentiation between MRSA and oxacillin susceptible S. aureus.     

葡萄球菌属的耐药性及耐药机制探讨

目的探讨诱导型克林霉素耐药测定的临床价值和评价头孢西丁纸片扩散法检测耐甲氧西林葡萄球菌mecA基因。方法用NCCLS规定的D试验法检测红霉素和克林霉素的耐药表型,以及根据2004年版的NCCLS推荐使用头孢西丁(30μg)纸片扩散法检测葡萄球菌mecA基因。结果所有390株葡萄球菌属细菌中,218株(55.9%)对红霉素和克林霉素均耐药(cMLS),70株(17.9%)对红霉素耐药,克林霉素敏感,但D试验阳性(iMLS),79株(20.3%)对红霉素耐药,克林霉素敏感,但D试验阴性(MS);头孢西丁纸片扩散法筛选的390株葡萄球菌属细菌,有272株为MRS。结论开展D试验检测葡萄球菌属中红霉素对克林霉素的诱导耐药性可帮助临床医师正确选用大环内酯类、克林霉素类抗菌药物,同时用头孢西丁纸片扩散法可以成为临床实验室常规开展筛选MRS的方法。     

应用双重PCR快速检测耐甲氧西林金黄色葡萄球菌

目的应用双重聚合酶链反应（PCR）技术,建立金黄色葡萄球菌及耐甲氧西林金黄色葡萄球菌（MRSA）的快速检测方法,指导临床及时、合理使用抗菌药物,防止MRSA的扩散。方法 根据金黄色葡萄球菌血浆凝固酶基因Coag和耐药基因mecA设计引物,调整PCR扩增反应各参数,建立快速、准确扩增Coag和mecA基因的双重PCR体系;应用双重PCR对临床分离鉴定的85株金黄色葡萄球菌同时扩增Coag和mecA基因片段,并将PCR扩增结果与苯唑西林-高盐琼脂筛选试验（OSAS）的结果进行比对。结果生化常规试验分离鉴定85株金黄色葡萄球菌,通过OSAS试验,共检出MRSA 53株,MRSA检出率为62.35%。双重PCR快速检测MRSA,85株金黄色葡萄球菌均扩增出Coag基因片段,其中53株扩增出mecA基因片段。双重PCR检测MRSA的结果与生化常规试验分离鉴定MRSA结果一致。结论双重PCR法能快速、同时检测金黄色葡萄球菌血浆凝固酶Coag基因和耐药基因mecA,有助于及早检出MRSA,指导临床合理用药,控制MRSA传播。     

Detection of mecA, femA, and femB genes in clinical strains of staphylococci using polymerase chain reaction.

MecA, a structural gene located on the chromosome of Staphylococcus aureus, characterizes methicillin-resistant S. aureus (MRSA), and femA and femB(fem) genes encode proteins which influence the level of methicillin resistance of S. aureus. In order to examine effectiveness of detecting mecA and fem genes in identification of MRSA, the presence of these genes in 237 clinically isolated strains of staphylococci was investigated by polymerase chain reaction (PCR). An amplified mecA DNA fragment of 533 base pairs (bp) was detected in 100% of oxacillin-resistant S. aureus, in 16.7% of oxacillin-sensitive S. aureus, in 81.5% of S. epidermidis, and in 58.3% of other coagulase-negative staphylococci (CNS). While the PCR product of femA (509 bp) or femB (651 bp) was obtained from almost all the S. aureus strains except for five oxacillin-resistant strains (2.5%), neither of these genes were detected in CNS. Therefore, the detection of femA and femB together with mecA by PCR was considered to be a more reliable indicator to identify MRSA by differentiating it from mecA-positive CNS than single detection of mecA.     

Prevalence and antibiotic resistance of foodborne Staphylococcus aureus isolates in Turkey

Abstract In this study, 154 Staphylococcus aureus isolates were detected from 1070 food samples (14.4%) collected from seven cities in Turkey. Antimicrobial susceptibility testing against 21 antibiotics was performed by agar disk diffusion method, and those isolates resistant to any antibiotic were further analyzed to determine minimum inhibitory concentration by E-test and polymerase chain reaction analysis of vanA and mecA genes. According to disk diffusion test results, a total of 139 strains were resistant to at least one tested antibiotic, with 39 (25.3%) strains being multidrug resistant (MDR) and the other 15 strains being susceptible to all antibiotics. Penicillin G, linezolid, erythromycin, and tetracycline took up 71.4%, 23.4%, 18.2%, and 15.6% of the tested strains, respectively. In addition, all of the strains were susceptible to vancomycin, oxacillin, cefoxitin, and imipenem. Only one strain (S158B) was resistant to both teicoplanin and cefazolin. On the other hand, the presence of vanA and mecA genes was not detected in the strains. Pulsed-field gel electrophoresis analysis was used to identify genetic-relatedness of the MDR strains. It is noteworthy that some strains from different sources showed 100% homology; however, some of MDR strains were found unrelated with 60% or less homology. The high diversity observed in pulsed-field gel electrophoresis results indicated the possible contamination of S. aureus from different sources and routes.     

Rapid dissemination of Staphylococcus aureus with classic oxacillin resistance phenotype at a new university hospital

To determine the prevalence rates of oxacillin-resistant Staphylococcus aureus (ORSA) at a new university hospital since its opening, the results of disk diffusion tests on all clinical isolates, recovered between 1990 and 1998 at the National Cheng Kung University Hospital, were reviewed. In order, to investigate the mechanisms of oxacillin resistance among strains of S. aureus in Taiwan, MICs were determined by an agar dilution method, and polymerase chain reaction and colony hybridization assays were performed on 288 isolates collected during November 1998 to detect the mecA gene. The prevalence rates of ORSA increased rapidly from 14.1% in 1990 to 61.0% in 1998. The increasing rates were most rapid in the first four-year period, ranging from 11.6 to 106.7% per year, and became steady after 1994, ranging from 1.8% to 11.6%. Of 288 clinical isolates collected in November 1998, 206 (71.5%) were resistant to oxacillin (MIC >/= 16 mg/L), and four were borderline resistant (MIC 2-8 mg/L). All 210 strains possessed the mec A gene (classic resistance). The present study demonstrated that ORSA could disseminate in a new hospital with great speed, and indicated that all ORSA strains in Taiwan revealed classic resistance phenotype.     

Species identification and detection of oxacillin resistance in coagulase-negative Staphylococcus blood isolates from neutropenic patients

One hundred coagulase-negative staphylococcal isolates from septicemic neutropenic patients with hematologic malignancies were identified to a species level by means of the French API STAPH strip system and by the Automicrobic VITEK system. According to these two methods, which concurred in 95% of cases, S. epidermidis (80–82% of the isolates) was the most frequently identified species, followed by S. haemolyticus (6–7% of the isolates). The susceptibility to oxacillin was also evaluated by macrodilution MIC, Automicrobic VITEK system and agar screen, and 76,78 and 79 of the 100 isolates, respectively, were found resistant to this antibiotic. All oxacillin-resistant isolates according to Automicrobic VITEK were confirmed resistant by agar screen. A 48h incubation was required to determine oxacillin resistance in 11 of 79 isolates with agar screen and in 10 of 76 isolates with macrodilution MIC.Automicrobic VITEK system may represent a useful method for rapid identification to a species level and early recognition of oxacillin resistance in coagulase-negative staphylococci.Corresponding author.