Molecular epidemiology for local outbreaks of methicillin resistantStaphylococcus aureus (MRSA)

Subtyping isolates may be useful for epidemiological studies of methicillin-resistant-Staphylococcus aureus (MRSA) outbreaks. Among subtyping methods, DNA-based techniques have been applied very effectively for this purpose. An outbreak of MRSA infections took place in one hospital in Barcelona early during 1991. From the beginning of the outbreak to December 92, 70 MRSA isolates from different patients and sources were collected. All strains were evaluated by restriction endonuclease analysis of plasmid DNA (REAP) and macrorestriction endonuclease analysis of genomic DNA usingSma I and pulsed-field-gel-electrophoresis (PFGE). Plasmid screening and REAP usingHind III demonstrated two plasmid subtypes: subtype A showing a large plasmid, and subtype B showing the same large plasmid plus a smaller one. Subtypes A and B corresponded to the more recent and older isolates, respectively, suggesting the loss of the small plasmid during the epidemic. PFGE usingSma I displayed two closely related profiles (PFGE subtype A and A'; CS=0.90). These subtypes were different from those subtypes exhibited from 4 methicillin-susceptible-Staphylococcusaureus (MSSA) isolates from the same hospital and from 2 epidemiologically unrelated MRSA isolates. Almost all isolates showing PFGE subtype A preceded those isolates showing PFGE subtype A'. This fact and the similarity between both subtypes suggested minor chromosomal DNA rearrangement during the outbreak from a unique strain. While PFGE usingSma I is a useful tool in evaluation of clonal dissemination, our data suggest epidemic or local outbreaks may need several methods to best delineate the source and spread of MRSA strains. The reproducibility and discriminatory power of REAP makes it a useful adjunct in this context.     

Evolution of Staphylococcus aureus and MRSA during outbreaks

Investigation of Staphylococcus aureus outbreaks, and particularly those due to methicillin-resistant S. aureus (MRSA) in hospitals, can identify infection reservoirs and prevent further colonization and infection. During outbreaks, S. aureus genomes develop single nucleotide polymorphisms (SNPs), small genetic rearrangements, and/or acquire and lose mobile genetic elements (MGE) encoding resistance and virulence genes. Whole genome sequencing (WGS) is the most powerful method for discriminating between related isolates and deciding which are involved in an outbreak. Isolates with only minor variations are detectable and can identify MRSA transmission routes and identify reservoirs. Some patients may carry ‘clouds’ of related isolates, and this has consequences for how we interpret the data from outbreak investigations. Different clones of MRSA are evolving at different rates, influencing their typability. S. aureus genome variation reveals the importance of antibiotic resistance in the long term evolution of successful hospital clones, contributing to strategies to prevent the spread of successful MRSA clones.     

Quantitative PCR analysis of genes expressed during biofilm development of methicillin resistant Staphylococcus aureus (MRSA)

Staphylococcus aureus biofilm associated infections remains a major clinical concern in patients with indwelling devices. Quantitative real-time PCR (qPCR) can be used to investigate the pathogenic role of such biofilms. We describe qPCRs for 12 adhesion and biofilm-related genes of four S. aureus isolates which were applied during in vitro biofilm development. An endogenous control (16S rRNA) was used for signal normalization. We compared the qPCR results with structural analysis using scanning electron microscopy (SEM). The SEM studies showed different cellular products surrounding the aggregated cells at different times of biofilm formation. Using qPCR, we found that expression levels of the gene encoding fibronectin binding protein A and B and clumping factor B (fnbA/B and clfB), which involves in primary adherence of S. aureus, were significantly increased at 24 h and decreased slightly and variably at 48 h when all 4 isolates were considered. The elastin binding protein (ebps) RNA expression level was significantly enhanced more than 6-fold at 24 and 48 h compared to 12 h. Similar results were obtained for the intercellular adhesion biofilm required genes type C (icaC). In addition, qPCR revealed a fluctuation in expression levels at different time points of biofilm growth of other genes, indicating that different parameter modes of growth processes are operating at different times.     

Molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) in a university hospital in Italy

The molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in a university hospital in Italy was studied in a five-month period in 1996, during which all S. aureus isolated were collected. All MRSA isolates (95) and a sample of methicillin-susceptible S. aureus (20) were typed with a variety of phenotypic and genotypic methods. Clonal identities were determined by pulsed-field gel electrophoresis (PFGE) of chromosomal SmaI digests and, for MRSA isolates, by probing ClaI digests with a mecA probe and a Tn554 probe. Overall, MRSA represented 32.3% of all isolates, with very high percentages from the intensive care units (adult and neonatal). PFGE after restriction with SmaI resolved genomic DNA of 95 MRSA strains into 26 major PFGE patterns. The use of southern blot hybridization of ClaI genomic digests with mecA and Tn554 allowed us a significant increase in discrimination, differentiating at least 32 different clones. Two major clones, however, each sharing common ClaI-mecA and Tn554 type and PFGE pattern as well as a common resistance phenotype, represented more than 50% of all MRSA isolates. The recovery of these two clones in the majority of the isolates of adult and neonatal intensive care units, respectively, is indicative of typical nosocomial outbreaks and clonal spread. It is concluded that intensive care units are major areas requiring preventative interventions.     

Dispersal of methicillin resistant Staphylococcus aureus (MRSA) in a burn intensive care unit

Methicillin resistant Staphylococcus aureus (MRSA) is a pathogen of special concern in intensive care units (ICUs). The burn units are a very susceptible habitat to colonization and infection events by this organism. In this paper isolation of MRSA from a sepsis case and from samples of the care unit air is described, along with simultaneous circulation of two clones of MRSA. Some peculiar epidemiological features of MRSA in burn intensive care wards are confirmed.     

应用聚合酶链反应检测日本血吸虫基因组DNA

中国是日本血吸虫病主要流行区[1],疫情形势严峻.准确评估钉螺感染和水体污染情况,对疫情防制意义重大.传统的压碎法、逸蚴法和哨鼠法灵敏性都较低[2],影响了血防工作的效率.有人尝试将PCR方法用于血吸虫病的诊断和流行监测[3-5],其中根据埃及和曼氏血吸虫中发现的串联重复序列建立的PCR方法都表现出极高的灵敏性[6-8],实用前景乐观[9].本研究的主要目的是揭示日本血吸虫中可能存在的该序列,优化PCR条件,评价其灵敏性.     

The cost of resistance: incremental cost of methicillin-resistant Staphylococcus aureus (MRSA) in German hospitals

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant problem in many healthcare systems. In Germany, few data are available on its economic consequences and, so far, no study has been performed using a large sample of real-life data from several hospitals. We present a retrospective matched-pairs analysis of mortality, length of stay, and cost of MRSA patients based mainly on routine administrative data from 11 German hospitals. Our results show that MRSA patients stay in hospital 11 days longer, exhibit 7% higher mortality, are 7% more likely to undergo mechanical ventilation, and cause significantly higher total costs (€ 8,198).

开封肉猪沙门菌和耐甲氧西林金葡菌污染状况分析

目的了解开封地区肉猪养殖及屠宰环节食源性致病菌的污染状况。方法对肉猪养殖环境和生猪屠宰过程随机采样,应用细菌的分离培养、生化鉴定和血清学鉴定,针对沙门氏菌和耐甲氧西林的金黄色葡萄球菌等致病菌进行跟踪监测。结果 264份样品中,共检出阳性菌株72株,其中沙门氏菌44株,阳性率为23.5%;耐甲氧西林的金黄色葡萄球菌28株,阳性率为36.4%。结论肉猪养殖和屠宰环节存在较为严重的致病菌污染,应引起足够重视。     

Risk factors for methicillin-resistant staphylococcus aureus (MRSA) infection in a Japanese geriatric hospital

A case control study on MRSA infection was carried out, with the purpose of evaluating the effect of age, gender, hypoalbuminemia, the limitation of activities of daily living (ADL), the administration of antibiotics and the use of the new cephems which include third generation cephalosporins and monobactam and carbapenems, on the occurrence of MRSA infection among the inpatients in a geriatric hospital. From April 1991 to March 1994, 285 patients underwent a bacterial culture in the various clinical aspects. 118 patients were positive for MRSA, who were then used as cases while 167 patients who were negative for MRSA were used as controls. The level of serum albumin and the ADL score were lower in the MRSA group than in the non-MRSA group (P < 0.01) while the number of antibiotics administered before bacterial culture was greater in the MRSA group than in the non-MRSA group (P < 0.01). The third generation cephems were more commonly used in the MRSA positive patients than the negative patients (P < 0.01). Even after controlling for the other factors, hypoalbuminemia (OR = 1.73, 95% CI = 1.27–2.36), the limited ADL (partially limited vs without limitation: OR = 1.88, 95% CI = 1.19–2.96, completely limited vs without limitation: OR = 2.50, 95% CI = 1.64–3.82), the use of antibiotics other than the third generation cephems (vs without antibiotics: OR = 1.73, 95% CI = 1.20–2.50) and the administration of the third generation cephems (vs without antibiotics: OR = 3.12, 95% CI = 2.16–4.50) increased the risk of MRSA infection.     

Detection and molecular characterization of a gentamicin-susceptible, methicillin-resistant Staphylococcus aureus (MRSA) clone in Rio de Janeiro that resembles the New York/Japanese clone

Staphylococcus aureus is the leading cause of hospital-acquired infections in many countries, and multiple factors contribute to the ability of these bacteria to disseminate and spread in hospitals. In Brazil it has been demonstrated that a multiresistant methicillin-resistant S. aureus clone, the so-called Brazilian epidemic clone, is widespread geographically. This clone was first detected in 1992 in Brazil, and recently from many other countries within South America, Europe and Asia. The study describes the detection of a gentamicin-susceptible heterogeneous MRSA clone that resembles another MRSA clone widely spread in US and Japanese hospitals, and supports the premise that the detection of heterogeneous MRSA isolates by some recommended methods is a challenging task that may, occasionally, result in MRSA misidentification.     

Appearance of methicillin-resistant Staphylococcus aureus (MRSA) sensitive to gentamicin in a hospital with a previous endemic distinct MRSA

Since 1990 a clone of gentamicin and methicillin-resistant Staphylococcus aureus (MRSA) has remained endemic in our hospital, but since January 1996 a gentamicin-sensitive strain has progressively replaced the previous clone. We characterized the phenotypic and molecular pattern of the MRSA strains isolated in our hospital in 1996 and compared prospectively the epidemiological, clinical and evolutionary characteristics of ninety patients infected or colonized by gentamicin-sensitive MRSA (GS-MRSA) (49) and by gentamicin-resistant MRSA (GR-MRSA) (41). Finally we studied the variation of aminoglycoside consumption in our hospital from 1989 to 1996. We observed two antibiotypes (GS-MRSA and GR-MRSA) corresponding to two major chromosomal patterns. Patients with GS-MRSA usually acquired the infection 72 hours after hospital admission. No significant differences were observed in epidemiological characteristics, clinical presentation and evolution between patients with GS-MRSA and GR-MRSA. Since 1989 aminoglycoside intake in our hospital has decreased by 46%.     

Recommendations for the prevention and control of methicillin-resistant Staphylococcus aureus isolates (MRSA) in hospitals and other healthcare facilities

The Commission for Hospital Hygiene and Infection Control (KRINKO) at the Robert Koch-Institute Berlin published the “Recommendations for Preventing and Controlling Methicillin-Resistant Staphylococcus aureus (MRSA) Strains in Hospitals and Other Medical Facilities“ in the Federal Health Gazette in 1999 [1]. These recommendations were translated for the current edition of GMS Krankenhaushygiene Interdisziplinär by the German Society of Hospital Hygiene.KRINKO''s work is legitimated by § 23 para. 2 of the Infection Protection Act. Regarding the legal nature of the KRINKO recommendations, it should be noted that they are neither a formal act or an administrative regulation. The KRINKO recommendations are instead an evidence-based consensus of particularly qualified experts. The consensus is reached by including the Federal States'' authorities and all competent professional bodies and associations. This is to guarantee that the KRINKO recommendations reflect the state-of-the-art of medical science, and are met with a high degree of user acceptance. The recommendations are published in the Federal Health Gazette and on the RKI''s Internet pages (http://www.rki.de/).Link to the German original edition of the MRSA recommendations     

Character of cell-free genomic DNA in embryo culture medium and the prospect of its clinical application in preimplantation genetic testing

There is increasing evidence that cell-free DNA (cfDNA) in spent culture media (SCM) can be amplified for genetic testing. Therefore, this paper reviews the cha...     

Methicillin-resistant Staphylococcus aureus (MRSA) isolated in clinics and hospitals in the Fukuoka city area

Bacteriological and clinical studies were carried out on 280 strains of Staphylococcus aureus isolated in clinics and hospitals in the Fukuoka city area from September 1990 to March 1991. The percentage of methicillin-resistant S. aureus (MRSA) strains studied was 41·4% (116 of 280). Of 116 MRSA strains, 48 (41·3%) produced coagulase VII and 21 (18·1%) produced coagulase II. The mean age of the patients who harboured MRSA, 70·5 ± 16·9 years, was significantly higher than that of patients with methicillin-sensitive S. aureus (MSSA), 44·2 ± 29·3 years (P < 0·001). MRSA was detected more frequently than MSSA in sputum (P < 0 · 01), while MSSA was detected more frequently than MRSA in pus (P < 0 · 01). Ninety (89 · 1%) of 101 strains of MRSA were isolated from inpatients and 98 (71 · 0%) of 130 strains of MSSA were isolated from outpatients. Similar number of MRSA strains were recovered in a variety of hospitals, indicating that there was no relationship between hospital size (number of beds) and the incidence of MRSA. As for drug susceptibility, coagulase VII-producing MRSA strains were more sensitive to clindamycin (P < 0 · 01) and more resistant to mino-cycline (P < 0 · 01) than were other MRSA strains.     

Qualitative and (semi)quantitative characterization of nasal and skin methicillin-resistant Staphylococcus aureus carriage of hospitalized patients

The objective of this study was to systematically investigate the carriage pattern and load of newly identified methicillin-resistant Staphylococcus aureus (MRSA) colonized or infected patients before any decolonization took place. Cultures of wounds (38%), of sputum (16%) or throat (10%) and of urine (10%) most frequently gave the initial positive MRSA result. Samples from nose, forehead, neck, axilla, and groin were obtained to determine the extent of nasal and extranasal colonization. Fifty-six (69%) of the screened patients proved to be MRSA positive at one or more of these sample sites, and 53 (65%) were extranasal carriers. The proportions positive for cultures of the nares, forehead, groin, neck and axilla were 54%, 51%, 38%, 35%, and 28%, respectively. The most sensitive screening method (96% sensitivity) was to take a combination of cultures from the nares, forehead and groin. Out of the 56 patients (100% sensitivity) this combination revealed 10 more MRSA-carriers than testing the nose alone (79% sensitivity). But the number of study patients was relative small. Therefore we cannot give general recommendations for MRSA screening on the basis of these results. For our hospital we concluded to take a combination of three screening samples to detect MRSA-carriers. Beside the MRSA-carriage pattern we report about the quantitative whole-body colonization. Out of 41 patients colonized on the forehead, a median of 20 MRSA/24 cm2 was obtained on contact agar plates. On the neck (n = 28), an identical value was found. The median MRSA levels for the nose (n = 44), the groin (n = 31), and the axilla (n = 23) were 80, 50 and 50 cfu/swab streak. The MRSA load varied widely from 1 to more than 100 colonies per culture. Further studies must show whether the individual number of MRSA cultured from different body sites is relevant for transmission, for acquiring infections or for decolonization efficacy.     

耐甲氧西林金黄色葡萄球菌中mecA、femA检测及其抗生素敏感性研究

目的探讨mecA、femA基因PCR聚合扩散快速检测耐甲氧西林金黄色葡萄球菌(MRSA)的敏感性及特异性。方法选择耐甲氧西林金黄色葡萄球菌株84株用PCR聚合扩散法检测mecA、femA基因,并用纸片扩散法检测MRSA菌株的药物敏感性。结果 84株耐甲氧西林金黄色葡萄球菌中,mecA基因阳性率为100%femA基因阳性率为97.6%。未发现万古霉素耐药的菌株。结论 PCRmecA、femA基因聚合扩散法即可用于MRSA快速诊断,又有特异性强的有点。     

Methicillin resistant Staphylococcus aureus (MRSA) isolated in Saudi Arabia: epidemiology and antimicrobial resistance patterns

Methicillin resistant Staphylococcus aureus (MRSA) comprised about 7·5% per annum of all S. aureus isolated in a general hospital in Jeddah, Saudi Arabia during the 3 year period 1990–1992. Most isolates were from wound sites (71%). Resistance to gentamicin (83%) and tetracycline (93%) was frequently observed whilst resistance to ciprofloxacin (1%) and rifampicin (6%) was uncommon. Low levels of mupirocin resistance (MIC 8 mg 1⁻¹), were detected in 3% of all MRSA isolates.     

Control and the prevention of methicillin-resistant Staphylococcus aureus in hospitals in Ireland: North/South Study of MRSA in Ireland 1999

As part of an all-island survey of methicillin-resistant Staphylococcus aureus (MRSA) in the Republic of Ireland (the South), where there is a mixed public and private healthcare system, and Northern Ireland (the North), where the healthcare system is part of the UK National Health Service, a questionnaire was circulated to all participating hospitals on measures routinely taken to control MRSA. Response rates were 100% in the North and 89% in the South. Over 70% of hospitals screened particular groups of patients on admission to hospital. Ninety-five percent of hospitals in the North and 88% in the South attempted to eradicate MRSA from carriage sites. Most hospitals attempted to isolate or cohort positive patients. About a quarter of hospitals in both parts of Ireland screened new healthcare workers for the presence of MRSA. Terminal decontamination of the environment after the discharge of a patient positive for MRSA was the norm in over 90% of hospitals, however, 6% of hospitals in the South used inappropriate disinfectants for MRSA. All hospitals in the North, but a minority (41%) in the South, had written antibiotic prescribing policies, but only 65% of hospitals in the South had access to an infection control committee, acute hospitals having greater access than district hospitals. The prevention and control of spread of MRSA remains a major challenge in the North and in the South. Although most hospitals in the North and in the South implemented current recommended guidelines on the control of MRSA in hospitals, there was some variability that may be resource related. Policies need to be reviewed in the light of the changing epidemiology of MRSA.     

The ‘moral careers’ of microbes and the rise of the matrons: An analysis of UK national press coverage of methicillin-resistant Staphylococcus aureus (MRSA) 1995–2006

This paper examines similarities and differences in media discourses relating to methicillin resistant Staphylococcus aureus (MRSA) at three important points in the development of the bacterium and its perception by the public over the last decade. We analyse three increasingly large sets of texts from the national media using a variety of complementary qualitative and quantitative methods. As such this paper exploits, develops and empirically assesses an emerging methodological trend in applied linguistics, namely the convergence of critical metaphor analysis, with corpus linguistics and science and technology studies. Using this, the study identifies a shifting media narrative that involves changes in dramatis personae over the decade. First, personified forces of nature, doctors and hospitals are engaged in a battle of evil against good, but also intelligence over stupidity. Second, we are presented with victims of personified bacterial forces and doctors and hospitals cast as perpetrators of crimes of omission by not cleaning hands or wards. Third, the malignant forces of politics try to exploit the evil forces of nature for their own ends while a mediator between the doctors and the potential victims of MRSA emerges and is given political and symbolic power: the modern matron.