Staphylococcus aureus isolates belonging to different multilocus sequence types present specific virulence gene profiles

To characterize 73 Staphylococcus aureus isolates from infections in an orthopedic hospital in Rio de Janeiro, we investigated the SCCmec types, the clonality by pulsed field gel electrophoresis and multilocus sequence typing, and the presence of virulence genes. Twenty-eight (38.3%) methicillin-resistant (16 SCCmec type IV and 12 type III) isolates were detected. Most (83.5%) of the isolates were included in five lineages: sequence type (ST) 239 (SCCmecIII), 1, 5, 30, and 1462 (SCCmecIV and/or methicillin-susceptible isolates). Virulence genes fnbB, bbp, and pvl were related to STs 239, 30, and 30/1462, respectively. Isolates from STs 1, 5, and 30 presented specific virulence profiles, irrespective of methicillin resistance.     

Comparative genomics and drug resistance of a geographic variant of ST239 methicillin-resistant Staphylococcus aureus emerged in Russia

Two distinct classes of methicillin-resistant Staphylococcus aureus (MRSA) are spreading in hospitals (as hospital-acquired MRSA, HA-MRSA) and in the community (as community-acquired MRSA, CA-MRSA). Multilocus sequence type (ST) 239 MRSA, one of the most worldwide-disseminated lineages, has been noted as a representative HA-MRSA. Here, we isolated ST239 MRSA (spa type 3 [t037] and staphylococcal cassette chromosome mec [SCCmec] type III.1.1.1) and its novel variant with ST239/spa351 (t030)/SCCmecIII.1.1.4 (SCCmecIII(R)) not only from hospitals but also from patients with urethritis in the community in Russia. The Russian variant (strain 16K) possessed a hybrid genome consisting of CC8 and CC30, similar to the ST239/spa3/SCCmecIII.1.1.1 HA-MRSA (TW20) genome, but with marked diversity. The 16K' CC30 section had SCCmecIII(R) carrying the dcs-carrying unit (which corresponded to the SCCmecIVc J3 joining region of ST30 CA-MRSA), lacked SCCmercury, and possessed a novel mobile element structure (MES16K) carrying the ccrC-carrying unit (with the recombinase gene ccrC1 allele 3) and drug resistance tranposons. The Russian variant included strains with a high ability to transfer its multiple drug resistance by conjugation; e.g., for strain 16K, the transfer frequency of a chloramphenicol resistance plasmid (p16K-1 with 2.9 kb in size) reached 1.4×10(-2), followed by Tn554 conjugative transfer at 3.6×l0(-4). The Russian variant, which has been increasing recently, included divergent strains with different plasmid patterns and pulsed field gel electrophoresis profiles. The data demonstrate the alternative nature of ST239 MRSA as CA-MRSA and also as a drug resistance disseminator, and its micro but dynamic evolution in Russia.     

耐甲氧西林葡萄球菌和肠球菌blaTEM及tetM基因检测

目的了解临床分离的耐甲氧西林葡萄球菌(MRS)和肠球菌中blaTEM及tetM基因存在状况。方法分离50株耐甲氧西林金黄色葡萄球菌(MRSA),7株耐甲氧西林表皮葡萄球菌(MRSE)、5株耐甲氧西林溶血葡萄球菌(MRSH)、15株粪肠球菌和9株屎肠球菌,采用PCR技术检测耐药基因。结果MRSA、MRSE、MRSH、粪肠球菌和屎肠球菌中blaTEM基因阳性率分别为40.0%、57.1%、60.0%、6.7%和88.9%,tetM基因阳性率分别为100%、0%、0%、66.7%、0%。结论blaTEM基因阳性率在MRS中较高,在屎肠球菌中则很高;携带tetM基因是MRSA和粪肠球菌对四环素耐药的主要原因。     

Staphylococcus aureus resistance to antibiotics: key points in 2010

Staphylococcus aureus has a strong adaptive capacity and thus acquired various types of resistance to antistaphylococcal agents. More than 90% of isolates produce a penicillinase. Oxacillin remains active against these strains, but hospital associated staphylococci and more recently community acquired staphylococci have developed crossed resistance between methicillin (MRSA), oxacillin and other beta-lactams by production of a penicillin binding protein (PBP) with low affinity for beta-lactams, PBP2a. The gene encoding PBP2a, mecA is carried by a chromosomal element which also contains other resistance genes to heavy metals and other antibiotics thus explaining the multiresistant profile of hospital associated MRSA. By contrast, community acquired MRSA (CA-MRSA) are only resistant to kanamycin, fusidic acid and tetracycline, in addition to methicillin. This profile is specific of the European CA-MRSA ST80 clone which also encodes for a very particular virulence factor, the Panton-Valentine leukocidin. Glycopeptides, vancomycin and teicoplanin, are alternatives to oxacillin in case of resistance or intolerance. Strains with decreased susceptibility to glycopeptides have been reported. Their detection is difficult but necessary because vancomycin MIC creep seems linked to poor outcome in patients.     

High rates of macrolide resistance among clinical isolates of Streptococcus agalactiae in Tunisia

One hundred sixty non duplicate erythromycin resistant Streptococcus agalactiae isolates were collected in Tunisia from January 2005 to December 2007 They were investigated to determine their resistance level to different macrolides and the mechanisms involved. Most erythromycin resistant S. agalactiae isolates were isolated from urinary specimens (38.75%, 62/160). The constitutive MLSB phenotype (cMLS) showed in 84.3% (135/160) with high MICs of macrolides and lincosamides (MIC90>256 microg/mL) and 8.2% (13/160) inducible MLSB phenotype (iMLS) with high MICs of macrolides (MIC90>256 microg/mL) and moderately increased MICs of lincosamides (MIC90=8 microg/mL). The M phenotype showed in 7.5% (12/160) with moderately increased MICs of macrolides (MIC90=32 microg/mL) and low MICs of lincosamides (MIC90=0.75 microg/mL). All strains were susceptible to quinupristun-dalfopristin association and linezolid (MIC90: 05 and 0.38 microg/mL respectively). Strains with MLSB phenotype harboured erm(B) gene with 825% (n=132), erm(TR) gene with 8.12% (n=13) and erm(B) plus mef (A) with 1.88% (n=3). All strains categorized as M phenotype carried the mef(A) gene (75%, n=12). cMLSB phenotype conferring cross resistance to macrolides, lincosamides and streptogramins B with high level of resistance was the most prevalent.     

Methicillin-Resistant Staphylococcus aureus in Commercial Swine Herds Is Associated with Disinfectant and Zinc Usage

Methicillin-resistant Staphylococcus aureus (MRSA) originating from swine is concerning for public health, but an understanding of the emergence and persistence of MRSA in nursery herds is lacking. The aim of this study was to determine whether MRSA in nursery pigs is associated with particular herd-level parameters, including the use of antimicrobials, disinfectants, and heavy metals, which may be driving the selection and persistence of antimicrobial resistance. Nasal cultures for MRSA were completed for 390 pigs from 26 farms at the end of the suckling phase and again at 3 weeks postweaning. Herd-level information was collected, and a random subset of MRSA isolates was screened for resistance to zinc and quaternary ammonium compounds (QACs). Multivariate analysis revealed that in-feed concentrations of zinc (P < 0.001) and frequent disinfection of nursery pens (P < 0.001) are associated with MRSA shedding in nursery pigs. Furthermore, 62.5% (25/40) of MRSA isolates carried the zinc resistance gene czrC and demonstrated decreased susceptibility to zinc. All MRSA isolates carried at least 1 QAC resistance gene. The most common genotype was qacG qacH smr, which occurred in 32.5% (13/40) of isolates. Seven isolates (17.5%) demonstrated a significant tolerance to benzalkonium chloride, indicating a potential to survive commercial QAC exposure in the presence of organic matter. Overall, these findings indicate that high levels of in-feed zinc and QAC-based disinfectants are important drivers in the selection and persistence of MRSA in commercial swine herds, and these agents may be coselecting for other antimicrobial resistance genes.     

A novel type-III staphylococcal cassette chromosome mec (SCCmec) variant among Indian isolates of methicillin-resistant Staphylococcus aureus

We identified a novel type-III staphylococcal cassette chromosome mec (SCC mec ) element carried by eight methicillin-resistant Staphylococcus aureus (MRSA) strains from different wards and patients in an Indian hospital. Although the pulsed-field gel electrophoresis pattern and spa types of eight strains were identical and clonally related to other nosocomial Indian isolates that belonged to sequence type (ST) 239 and spa type t037, the minimum inhibitory concentration (MIC) of these eight variants was noticeably low compared with the typical type-III isolates from the same hospital, and we were unable to identify ccrC and hsdR by multiplex PCR, although mer operon and transposases A, B, and C of Tn 554 were amplified. By amplifying the entire SCC mec region by long-range PCR and determining parts of the nucleotide sequences of one isolate (V14), we found that the strain carried a novel SCC mec element containing a 422 bp sequence, which is highly homologous to that identified in strain CCR1-9583, mer operon and plasmid pT181 integrated in tandem via IS 431 in the J3 region. It also carried a cassette chromosome, previously reported to be an SCC-like element, downstream of type-III SCC mec . Because PCR amplification of representative genes showed that these eight strains carried the same genetic elements, they belong to a novel MRSA clone that differs from most nosocomial clones carrying type-III SCC mec and SCC mercury , despite belonging to the ST239 genotype.     

Molecular nature of methicillin-resistant Staphylococcus aureus derived from explosive nosocomial outbreaks of the 1980s in Japan

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) with Panton-Valentine leukocidin (PVL) genes is increasing worldwide. Nosocomial outbreak-derived (hospital-acquired) MRSA (HA-MRSA) in Japan in the 1980s was also largely PVL(+). PVL(+) HA-MRSA and CA-MRSA shared the same multi-locus sequence type (ST30) and methicillin resistance cassette (SCCmecIV), but were divergent in oxacillin resistance, spa typing, PFGE analysis or clfA gene analysis. PVL(+) HA-MRSA, which probably originated in PVL(+)S. aureus ST30, was highly adhesive (carrying cna and bbp genes), highly-toxic (carrying luk(PV) and sea genes) and highly drug-resistant. PVL(+) HA-MRSA was once replaced by other PVL(-) HA-MRSA (e.g., ST5), and is re-emerging as CA-MRSA.     

Synergistic effects between silibinin and antibiotics on methicillin-resistant Staphylococcus aureus isolated from clinical specimens

Methicillin-resistant Staphylococcus aureus (MRSA) is a dangerous microorganism, and creates serious medical problems. It causes many types of infections in humans and often acquires multi-drug resistance. In this study, silibinin was evaluated against 20 clinical isolates of MRSA, either alone or in combination with ampicillin or oxacillin, using a checkerboard assay. The silibinin exhibited good activity against isolates of MRSA, and MRSA ATCC33952 and MSSA ATCC25923, with minimum inhibitory concentrations/minimum bactericidal concentrations (MICs/MBCs) ranging between 2-8/4-16 μg/mL, for ampicillin 2-1024/2-2048 μg/mL, and for oxacillin 0.25-32/0.5-64 μg/mL. The range of MIC(50) and MIC(90) were 0.5-4 μg/mL and 2-8 μg/mL, respectively. The MICs/MBCs for the combination of silibinin plus oxacillin or ampicillin were reduced by ≥4-fold against the MRSA isolates tested, demonstrating a synergistic effect, as defined by a fractional inhibitory concentration index (FICI) of ≤0.5. Furthermore, a time-kill study evaluating the growth of the tested bacteria showed that growth was completely attenuated after 2-5 h of treatment with the 1/2 MIC of silibinin, regardless of whether it was administered alone or with oxacillin (1/2 MIC) or ampicillin (1/2 MIC). In conclusion, silibinin exerted synergistic effects when administered with oxacillin or ampicillin and the antibacterial activity and resistant regulation of silibinin against clinical isolates of MRSA might be useful in controlling MRSA infections.     

Impact of Molecular Epidemiology and Reduced Susceptibility to Glycopeptides and Daptomycin on Outcomes of Patients with Methicillin-Resistant Staphylococcus aureus Bacteremia

Background

Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia was associated with high mortality, but the risk factors associated with mortality remain controversial.

Methods

A retrospective cohort study was designed. All patients with MRSA bacteremia admitted were screened and collected for their clinical presentations and laboratory characteristics. Minimum inhibitory concentration (MIC) and staphylococcal cassette chromosome mec (SCCmec) type of bacterial isolates were determined. Risk factors for mortality were analyzed.

Results

Most MRSA isolates from the 189 enrolled patients showed reduced susceptibility to antibiotics, including MIC of vancomycin ≥ 1.5 mg/L (79.9%), teicoplanin ≥ 2 mg/L (86.2%), daptomycin ≥ 0.38 mg/L (73.0%) and linezolid ≥ 1.5 mg/L (64.0%). MRSA with vancomycin MIC ≥ 1.5 mg/L and inappropriate initial therapy were the two most important risk factors for mortality (both P < 0.05; odds ratio = 7.88 and 6.78). Hospital-associated MRSA (HA-MRSA), carrying SCCmec type I, II, or III, was associated with reduced susceptibility to vancomycin, teicoplanin or daptomycin and also with higher attributable mortality (all P < 0.05). Creeping vancomycin MIC was linked to higher MIC of teicoplanin and daptomycin (both P < 0.001), but not linezolid (P = 0.759).

Conclusions

Giving empirical broad-spectrum antibiotics for at least 5 days to treat catheter-related infections, pneumonia, soft tissue infection and other infections was the most important risk factor for acquiring subsequent HA-MRSA infection. Choice of effective anti-MRSA agents for treating MRSA bacteremia should be based on MIC of vancomycin, teicoplanin and daptomycin. Initiation of an effective anti-MRSA agent without elevated MIC in 2 days is crucial for reducing mortality.     

Antimicrobial susceptibility and invasive ability of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> isolates from mastitis from dairy backyard systems

Fifteen (15) backyard farms were investigated to determine the antimicrobial susceptibility and invasion ability of S. aureus isolates from cows with subclinical mastitis in México. A total of 106 cows were sampled and 31 S. aureus isolates were recovered. S. aureus isolates were resistant to penicillin class antibiotics and susceptible to gentamicin and cetyltrimethylammonium bromide. STA9 and STA13 isolates were resistant to erythromycin (MIC > 25 microg/ml) and lincomycin (STA13, MIC > 25 microg/ml; STA9, MIC > 100 microg/ml). STA9 isolate harbors the erm(B) and msr(A) genes, whereas STA13 isolate harbors the erm(C) gene. STA9 and STA13 isolates contains the lnu(A) gene. Only 5 isolates (STA11, STA13, STA14, STA15 and STA21) were able to internalize in bovine mammary epithelial cells. These results indicate that S. aureus isolates from dairy backyard farms showed differences in the antimicrobial susceptibility patterns and invasion ability in bovine mammary epithelial cells. This kind of evaluations should be performed in different dairy regions, since resistance patterns and isolate diversity vary on a per-region basis.     

Resistance to macrolide, lincosamide and streptogramin antibiotics in staphylococci isolated in Istanbul, Turkey

The purpose of this study was to investigate the prevalence and genetic mechanisms of erythromycin resistance in staphylococci. A total of 102 erythromycin resistant non-duplicate clinical isolates of staphylococci [78 coagulase negative stapylococci (CNS), 24 Staphylococcus aureus] were collected between October 2003 and August 2004 in Istanbul Faculty of Medicine in Turkey. The majority of the isolates were from blood and urine specimens. Antimicrobial susceptibilities were determined by the agar dilution procedure and the resistance phenotypes by the double disk induction test. A multiplex PCR was performed, using primers specific for erm(A), erm(B), erm(C), and msrA genes. Among the 78 CNS isolates, 57.8% expressed the MLSB-constitutive, 20.6% the MLSB-inducible, and 21.6% the MSB phenotypes. By PCR, 78.2% of these isolates harbored the erm(C) gene, 8.9% erm(A), 6.4% erm(B), and 11.5% msrA genes. In S. aureus, the constitutive MLSB (58.3%) was more common than the inducible phenotype (20.8%). erm(A) was detected in 50% and erm(C) in 62.5% of the isolates, while 37.5% contained both erm(A) and erm(C). erm(C)-associated macrolide resistance was the most prevalent in CNS, while erm(C) and erm(A, C) was the most prevalent in S. aureus.     

金黄色葡萄球菌儿童临床分离株携带PVL基因状况的分析

目的了解金黄色葡萄球菌儿童分离株携带Panton-Valentine杀白细胞素（PVL）基因的状况及感染类型。方法采用多重PCR同时检测金黄色葡萄球菌16SrRNA基因、PVL基因和mecA基因;多重PCR检测MR—SA的SCCmec基因型及亚型。结果66株金黄色葡萄球菌JL童临床分离株经多重PCR检测,其中MRSA有7株（10．6％）,MSSA有59株（89．4％）;携带PVL基因金黄色葡萄球菌有31株,总阳性率为47．O％（31／66）,其中2株为MRSA,29株为MSSA,阳性率分别为28．6％（2／7）和49。2％（29／59）。2株MRSA都属于SCCmecIV型;31株PVL基因阳性分离株有21株分离自脓液,7株分离自血液,仅1株分离自痰液。结论儿童MSSA是携带PVL基因的主要菌株,携带PVL基因的金黄色葡萄球菌主要引起化脓性感染和血流感染。     

Synergic interaction between pomegranate extract and antibiotics against Staphylococcus aureus

We evaluated the interaction between Punica granatum (pomegranate) methanolic extract (PGME) and antibiotics against 30 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA). Susceptibility testing of the isolates to PGME and antibiotics was performed by the broth dilution method. Synergic activity was detected between PGME and the 5 antibiotics tested, chloramphenicol, gentamicin, ampicillin, tetracycline, and oxacillin, ranging from 38% to 73%. For some isolates, PGME did not interfere with the action of any of the antibiotics tested. The bactericidal activity of PGME (0.1 x MIC) in combination with ampicillin (0.5 x MIC) was assessed using chosen isolates by time-kill assays, and they confirmed the synergic activity. Using this combination, cell viability was reduced by 99.9% and 72.5% in MSSA and MRSA populations, respectively. PGME increased the post-antibiotic effect (PAE) of ampicillin from 3 to 7 h. In addition, PGME demonstrated the potential to either inhibit the efflux pump NorA or to enhance the influx of the drug. The detection of in vitro variant colonies of S. aureus resistant to PGME was low and they did not survive. In conclusion, PGME dramatically enhanced the activity of all antibiotics tested, and thus, offers an alternative for the extension of the useful lifetime of these antibiotics.     

The prevalence of Staphylococcus aureus and methicillin resistant Staphylococcus aureus in milk and dairy products in Riyadh,Saudi Arabia

In terms of life- menaced contagion, methicillin resistant Staphylococcus aureus (MRSA) is known to be one of which and it is truly notable in the contaminated food causing a community health anxiety. However, the occurrence of S. aureus and MRSA in diverse kinds of dairy products have been tested in this study. Samples from: raw milk (unpasteurized) from horse, goat, camel, and cow origins and unpacked cheese were checked for the recovered strains of such bacterium and MRSA. Wholly, MRSA isolates were verified for antimicrobial susceptibility and further characterized by mecA and staphylococcal cassette chromosome mec (SCCmec) typing. Also, Panton-Valentine Leukocidin (PVL), Staphylococcus aureus protein A (spa), and Staphylococcal enterotoxins (SEs) were also tested between all positive MRSA isolates in order to discover the virulence factors. Consequently, 70% of the 100 collected dairy products samples were contaminated by S. aureus bacteria and 72.9% of them were defined as MRSA. 9.8% of MRSA isolates contained mecA genes with SCCmec type II (80%) as the most common SCCmec type. Moreover, large number of MRSA isolates were identified as multidrug resistance and 28.6% of MRSA-mecA positive isolates were also carried vancomycin resistance genes (i.e., vanB). Too, spa gene was detected between 9.8% of MRSA isolates but PVL gene was not spotted at all. Additionally, the existing of SEs was variable between MRSA isolates and the most common type was SEH (51%). In general, our results confirmed that raw milk and unpacked cheese in the Kingdom of Saudi Arabia (Riyadh) is a potential vehicle for multidrug resistant MRSA transmission. It is a critical civic health menace and stresses, thus; the need of applying well cleanliness practices is essential.     

Synthesis and potent antimicrobial activity of some novel methyl or ethyl 1H-benzimidazole-5-carboxylates derivatives carrying amide or amidine groups

A series of benzimidazole-5-carboxylic acid alkyl ester derivatives carrying amide or amidine substituted methyl or phenyl groups at the position C-2 were synthesised and evaluated for antibacterial and antifungal activities against S. aureus, methicillin resistant S. aureus (MRSA), S. faecalis, methicillin resistant S. epidermidis (MRSE), E. coli and C. albicans. The results showed that while all simple acetamides are essentially inactive, aromatic amides and amidines have potent antibacterial activities. Aromatic amidine derivatives 13 f-h exhibited the best inhibitory activity with 1.56-0.39 microg/mL MIC values against MRSA and MRSE.     

金黄色葡萄球菌所致肺部感染的耐药特点及其Panton—Valentine杀白细胞素基因的携带状况分析

目的分析金黄色葡萄球菌所致肺部感染的耐药性特点及其Panton—Valentine杀白细胞素基因的携带状况。方法回顾性调查了温州医学院第一附属医院2005年1月至2006年1月医院感染的金黄色葡萄球菌所致肺部感染患者132例,对其体外药敏试验进行分析;并利用多重PCR检测其PVL基因,应用多位点基因序列分型（multilocus sequence typing,MLST）技术对PVL基因阳性的菌株进行序列分型。耐甲氧西林金黄色葡萄球菌（methicillin-resistant Staphylococcus aureus,MRSA）的SCCmec基因分型采用多重聚合酶链反应。结果致肺部感染的132株金黄色葡萄球菌的耐药现象较为严重,仅对万古霉素、呋喃妥因及复方新诺明等药物的敏感率较高;其中经多重PCR筛选出10株携带PVL基因的金葡菌,全部为MRSA菌株,3株为ST239-SCCⅢ,2株为ST398-SCCmecⅢ,2株为ST398-SCCmecⅣ,ST25-SCCmecⅢ、ST59-SCCmecⅠ和ST88-SCCmecⅢ各1株。结论肺部感染的金黄色葡萄球菌对多种抗生素耐药,呈多重耐药性;其携带PVL基因占一定比例。     

长沙地区临床分离金黄色葡萄球菌的耐药监测

目的了解长沙地区临床分离金黄色葡萄球菌（以下简称金葡菌）对常用抗菌药物的耐药现状,探讨金黄色葡萄球菌对甲氧西林的耐药水平。方法收集长沙地区11家医院2009年11月至2010年11月临床分离的非重复金葡菌279株,应用Vitek-2全自动微生物分析系统进行鉴定,K-B法检测金葡菌对24种药物的敏感性,产色头孢菌素试验检测β-内酰胺酶以及D试验检测诱导型克林霉素耐药。应用头孢西丁和苯唑西林纸片扩散法筛查耐甲氧西林的金葡菌（MRSA）,琼脂稀释法检测头孢西丁和苯唑西林的最低抑菌浓度（MIC）。结果在被检测的24种药物中,敏感率〉50%的药物为9种,未发现对万古霉素、替考拉宁和利奈唑胺耐药菌株;耐药率〉50%的抗菌药物有11种,其中以青霉素和氨苄西林的耐药率最高（均为97.1%）。MRSA的分离率达54.5%,且对常用的16种抗菌药物的耐药率均显著高于甲氧西林敏感金黄色葡萄球菌（MSSA）。279株金葡菌中,β-内酰胺酶阳性250株（89.6%）;红霉素耐药而克林霉素敏感或中介的30株中,D试验阳性22株（73.3%）。苯唑西林（OXA）和头孢西丁（FOX）MIC范围分别为0.125～〉256μg/mL和2～〉256μg/mL,苯唑西林的MIC50和MIC90分别为128μg/mL和256μg/mL,头孢西丁的MIC50和MIC90分别为64μg/mL和256μg/mL。结论长沙地区临床分离金葡菌对常用抗菌药物呈多重耐药;MRSA不仅分离率高,而且对甲氧西林呈高水平耐药。     

Novel 10-bp deletion in the translational attenuator of a constitutively expressed erm(A) gene from Staphylococcus epidermidis.

Alterations in the erm(A) regulatory region of six clinical isolates of Staphylococcus epidermidis and one of Staphylococcus haemolyticus displaying a constitutive resistance phenotype were investigated. Anovel deletion of 10 bp with respect to the corresponding sequence of Tn554 was identified in the attenuator of a constitutively expressed erm(A) gene of one of the S. epidermidis isolates. Thus far, this is the smallest deletion conferring constitutive resistance in the translational attenuator of erm(A) in a naturally occurring S. epidermidis strain of human origin.     

mecA基因PCR扩增法检测耐甲氧西林金黄色葡萄球菌

目的 应用mecA基因PCR扩增法检测耐甲氧西林金黄色葡萄球菌（methicillin resistant staphylococcus aureus,MRSA）。方法 临床分离的70株金黄色葡萄球菌,应用mecA基因PCR扩增法鉴定MRSA,并与苯唑西林纸片扩散法进行比较。结果 70株金黄色葡萄球菌用PCR扩增法和纸片扩散法有6株鉴定有差异,4株。mecA基因阳性而纸片扩散法鉴定为敏感,1株mecA基因阳性纸片扩散法鉴定为临界耐药,1株mecA基因阴性却表现为苯唑西林耐药,2种方法符合率为91．43％。结论 mecA基因PCR扩增法可以准确、快速判定MRSA,特别是对隐匿型或低水平耐药菌株的检出有重要的价值。