A novel selective medium for the detection of methicillin-resistant Staphylococcus aureus enabling result reporting in under 24 h

A simple selective broth was devised to indicate the presence of methicillin resistant Staphylococcus aureus (MRSA) in clinical samples. The broth comprised nutrient broth supplemented with sodium chloride, ciprofloxacin, colistin and aztreonam as selective agents and also mannitol, trehalose and phenol red as an indicator system. In a preliminary study using 228 clinical samples this selective mannitol broth (SMB) proved to be more sensitive than other selective agars for detection of MRSA within 24 h. In an extended study of a further 1124 clinical samples from 470 randomly selected patients, SMB detected 85.1% of MRSA strains present with a specificity of 43.6%. We conclude that SMB offers a convenient, inexpensive and sensitive method for high-throughput screening for MRSA.     

Evaluation of three methods for detection of methicillin-resistant Staphylococcus aureus

AIM: To evaluate GenoType methicillin-resistant Staphylococcus aureus (MRSA) Direct assay and cultivation for the identification of MRSA by using mecA polymerase chain reaction (PCR) as the “gold standard” assay. METHODS: In total of 61 nasal specimens from patients at the intensive care unit were studied by GenoType MRSA Direct test, conventional culture method and automated bacterial identification system. The results of GenoType MRSA Direct assay were compared to conventional culture method the identification of MRSA and mecA gene PCR as the “gold standard” method. The sensitivity, specificity, positive predictive value and negative predictive value were calculated. RESULTS: In total, 61 specimens were studied. Fifty-four specimens (88.5%) were negative by all three methods. Six swabs (9.8%) were found positive by GenoType MRSA Direct test, conventional culture method and automated bacterial identification system. The presence of mecA in these strains was confirmed by PCR. One swab sample was negative for culture methods but MRSA and mecA gene were detected by GenoType MRSA Direct test and mecA PCR respectively. GenoType MRSA Direct test had a sensitivity of 100% (6/6) and a specificity of 100% (55/55), with a positive predictive value of 100% and a negative predictive value of 98%. Culture method of MRSA had a sensitivity of 83.3% (5/6) and a specificity of 98.2% (55/56). CONCLUSION: It was found that the GenoType MRSA Direct assay, which is a rapid and accurate test, is of the same sensitivity and specificity with mecA PCR. The GenoType MRSA Direct assay can be a better tool for rapid and accurate detection of MRSA in diagnostic laboratories.     

Osteomyelitis with methicillin-resistant Staphylococcus aureus

We describe 10 patients with hospital-acquired osteomyelitis due to methicillin-resistant Staphylococcus aureus. The patients were posttraumatic and eight had a foreign body in situ at the site of infection. Vancomycin therapy in association with radical debridement was followed by clinical and radiological cure in eight patients at 2-3.5 years follow-up, in two of whom a foreign body was left in situ. Only minor adverse effects of vancomycin therapy (one rash, two thrombophlebitis) were seen.     

Pneumonia and new methicillin-resistant Staphylococcus aureus clone

Necrotizing pneumonia caused by Staphylococcus aureus strains carrying the Panton-Valentin leukocidin gene is a newly described disease entity. We report a new fatal case of necrotizing pneumonia. An S. aureus strain with an agr1 allele and of a new sequence type 377 was recovered, representing a new, emerging, community-acquired methicillin-resistant clone.     

A model for surveillance of methicillin-resistant Staphylococcus aureus

It is well recognized that methicillin-resistant Staphylococcus aureus (MRSA) has become a community pathogen. Several key differences between community-associated and hospital-associated MRSA strains exist, including distinct methicillin resistance genes and genetic backgrounds and differing susceptibility to antibiotics. Recent studies have demonstrated that typical hospital and community strains easily move between hospital and community environments. Despite evidence of MRSA's expanding reach in the community, the best methods for population-level detection and containment have not been established. In an effort to determine effective methods for monitoring the spread of MRSA, we reviewed the literature on hospital-associated and community-associated MRSA (CA-MRSA) in the community and proposed a model for enhanced surveillance. By linking epidemiologic and molecular techniques within a surveillance system that coordinates activities in the community and health-care setting, scientists and public health officials can begin to measure the true extent of CA-MRSA in communities and hospitals.     

耐甲氧西林金黄色葡萄球菌mecA基因的临床研究

目的比较荧光定量PCR法和传统细菌培养药敏试验两种方法鉴定耐甲氧西林金黄色葡萄球菌(MRSA)的能力,评估荧光定量PCR直接检测不同类型标本中MRSA的mecA基因是否具有临床应用价值。方法收集2013年11月-2014年11月经细菌培养和纸片药敏试验确定为金黄色葡萄球菌的111份临床标本,荧光定量PCR法检测标本的mecA基因,比较两种方法结果。结果两种方法具有较好一致性、吻合度,差异有统计学意义;以传统方法为对照,荧光定量PCR直接检出MRSA的敏感性为100.0%、特异性90.9%;PCR检出痰液标本的MRSA的敏感性为100.0%、特异性100.0%;PCR检出其他标本的MRSA的敏感性为100.0%、特异性81.8%;mecA基因直接检测与传统方法不一致的全部为血培养标本,但分离菌落基因检测与药敏结果一致。结论荧光定量PCR直接检测临床标本mecA基因用于筛查MRSA可靠,临床微生物实验室可推广以早期控制医院感染和指导临床抗菌药物使用。     

应用显色培养基快速检测血培养中耐甲氧西林金黄色葡萄球菌

目的 评价CHRMOgenic MRSA显色培养基在耐甲氧西林金黄色葡萄球菌(MRSA)所致血流感染的快 速诊断方面应用价值.方法 对2009年1-12月临床常规送检的血培养使用全自动仪器孵育,仪器报警阳性后及时取出血培养瓶,涂片镜检后如发现镜下细菌为革兰阳性球菌、呈葡萄状排列者,转种CHRMOgenic MRSA显色培养基;琼脂稀释法检测耐甲氧西林金黄色葡萄球菌的抗菌药物最低抑菌浓度,双重PCR方法检测菌株nuc、mecA基因;比较CH RMOgenic MRSA显色培养基鉴定结果与实验室常规鉴定及PCR方法鉴定结果.结果 2009年1-12月医院阳性血培养瓶中检出金黄色葡萄球菌72份,其中耐甲氧西林金黄色葡萄球菌48份,凝固酶阴性葡萄球菌491份,血培养分离MRSA耐药率除对万古霉素、替考拉宁、米诺环素较敏感外,对其他多种抗菌药物的耐药率均＞90.0％,CHRMOgenic MRSA显色培养基直接检测阳性血培养瓶中MRSA结果,与常规鉴定及PCR检测结果的符合率高,特异性为98.8％,敏感性为97.9％.结论 阳性血培养涂片镜检与CH RMOgenic MRSA显色培养基相结合,将实验室诊断MRSA血流感染的平均报告时间提前1d,是一种快速有效的简易方法,适于临床实验室的广泛应用.     

Comparison of systematic versus selective screening for methicillin-resistant Staphylococcus aureus carriage in a high-risk dermatology ward.

OBJECTIVE: To compare two strategies for screening methicillin-resistant Staphylococcus aureus (MRSA) carriers in a high-risk dermatology ward: systematic screening of all admitted patients versus selective screening of patients at risk. DESIGN: The two strategies were applied prospectively during two consecutive periods. In period A (8.5 months), only patients transferred from other wards, or with a history of prior hospitalization, or presenting chronic wounds or disease with denuded skin were considered at high risk of MRSA carriage and sampled. In period B (7.5 months), all admitted patients were systematically screened. End-points were the number of patients having a MRSA-positive screening sample on admission during period B and having none of the risk factors used in period A, the rate of imported MRSA cases, and the rate of acquired cases. SETTING: A 1,032-bed university hospital with a 19-bed inpatient dermatology ward, a referral center for toxic epidermal necrolysis and severe extensive dermatoses. PATIENTS: The study included 729 dermatology inpatients (370 in period A and 359 in period B). RESULTS: During period A, screening samples were obtained on admission for 30% of patients (77% of the patients at risk) and identified 25 MRSA carriers. During period B, 90.5% of admitted patients were screened, and 26 MRSA carriers were detected on admission; all of these patients belonged to at least one predefined category at risk for carriage. Overall rates of imported and acquired cases were similar between the two periods (6.8% vs 7.5%, and 2.9% vs 2.4%, respectively). CONCLUSIONS: A screening strategy targeted to patients at risk of harboring MRSA has similar sensitivity and is more cost-effective than a strategy of systematic screening to identify MRSA carriers on admission.     

Molecular epidemiology of methicillin-resistant Staphylococcus aureus

Subtyping methicillin- resistant Staphylococcus aureus (MRSA) isolates and tracking nosocomial infections have evolved from phenotypic to genotypic approaches; most laboratories now depend on pulsed-field gel electrophoresis (PFGE). We discuss the limitations of current image-based genotyping methods, including PFGE, and the advantages (including ease of entering data into a database) of using DNA sequence analysis to control MRSA infections in health-care facilities.     

Human-to-dog transmission of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) was cultured from the nose of a healthy dog whose owner was colonized with MRSA while she worked in a Dutch nursing home. Pulsed-field gel electrophoresis and typing of the staphylococcal chromosome cassette mec (SCCmec) region showed that both MRSA strains were identical.     

耐甲氧西林金黄色葡萄球菌的目标性监控与分析

目的 了解临床耐甲氧西林金黄色葡萄球菌的分离及耐药性,探索耐甲氧西林金黄色葡萄球菌感染病例的监控措施.方法 对2010年医院临床分离的病原菌进行目标性监测,统计出耐甲氧西林金黄色葡萄球菌的株数以及耐药性,并对临床耐甲氧西林金黄色葡萄球菌感染病例实施监控.结果 全年检测结果发现,共分离出金黄色葡萄球菌334株,耐甲氧西林金黄色葡萄球菌50株,检出率为14.97％;对抗菌药物耐药率较高;全院未发生耐甲氧西林金黄色葡萄球菌的暴发和流行.结论 耐甲氧西林金黄色葡萄球菌分离株数较多,耐药率较高,应该加强临床合理使用抗菌药物的管理,并对耐甲氧西林金黄色葡萄球菌感染病例实施监控,预防和减少多药耐药菌的产生,控制医院感染.     

Genetic characterization of methicillin-resistant Staphylococcus aureus

The genome structure of Staphylococcus aureus is analyzed. The genome is composed of two domains. The first domain, descendent from an ancestral bacterial species, contains house-keeping genes that showed highest homology to those of Bacillus species. The second domain contained the genes responsible for virulence and drug-resistance in human infection that seems to have been acquired from other bacterial species via lateral gene transfer. The latter domain constitutes the genetic information that makes S. aureus a notorious hospital pathogen.     

In-vitro evaluation of povidone-iodine and chlorhexidine against methicillin-resistant Staphylococcus aureus.

The in-vitro activity of povidone-iodine (PVP-I) and chlorhexidine (CHX) against 33 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) was evaluated by a quantitative suspension test method. Bactericidal potency was measured by the logarithmic reduction factors (LRFs) achieved with each strain, tested at dilutions 25-800 over exposure times 30-300 s using a challenge of approximately 10(7) colony forming units (cfu) ml-1. The mean LRFs achieved over all dilutions, times and strains were significantly higher for PVP-I than CHX. PVP-I exhibited a superior killing effect whether measured by rate of kill or final LRF achieved. This difference was highly significant as judged by analysis of variance (P less than 0.001). Full efficacy of an antiseptic has been defined as a safe LRF greater than five. Over the dilution range 25-200 this was achieved by CHX with only three of 33 strains. In contrast, PVP-I achieved full efficacy with all 33 strains.     

Control of epidemic methicillin-resistant Staphylococcus aureus

We controlled the spread of epidemic methicillin-resistant Staphylococcus aureus (MRSA) infection in an 884-bed veterans' facility by cohorting known active MRSA carriers and MRSA-infected patients on one nursing unit. Simultaneously, all previously-institutionalized transfers into the veterans' facility were screened with swab cultures for MRSA at the time of admission. All MRSA patients were maintained on contact (gown and glove) or strict isolation and treated aggressively with topical and enteral antibiotics with the assistance of the infectious disease consultant. The monthly incidence of new MRSA patients dropped from a maximum of 16 per month to three or less per month within six months of instituting these infection control measures. There were no further MRSA bacteremias after the establishment of the MRSA cohort in a single unit. Aggressive cohort management of known MRSA patients and screening of previously-institutionalized patients on admission for MRSA controlled epidemic MRSA in this large institution.