Elimination of epidemic methicillin-resistant Staphylococcus aureus from a university hospital and district institutions,Finland

From August 1991 to October 1992, two successive outbreaks of methicillin-resistant Staphylococcus aureus (MRSA) occurred at a hospital in Finland. During and after these outbreaks, MRSA was diagnosed in 202 persons in our medical district; >100 cases involved epidemic MRSA. When control policies failed to stop the epidemic, more aggressive measures were taken, including continuous staff education, contact isolation for MRSA-positive patients, systematic screening for persons exposed to MRSA, cohort nursing of MRSA-positive and MRSA-exposed patients in epidemic situations, and perception of the 30 medical institutions in that district as one epidemiologic entity brought under surveillance and control of the infection control team of Turku University Hospital. Two major epidemic strains, as well as eight additional strains, were eliminated; we were also able to prevent nosocomial spread of other MRSA strains. Our data show that controlling MRSA is possible if strict measures are taken before the organism becomes endemic. Similar control policies may be successful for dealing with new strains of multiresistant bacteria, such as vancomycin-resistant strains of S. aureus.     

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.     

Cost-effective eradication of an outbreak of methicillin-resistant Staphylococcus aureus in a community teaching hospital

During an eight-month period, 25 hospitalized patients became infected or colonized with methicillin-resistant Staphylococcus aureus (MRSA) in a 464-bed acute care, medical-surgical teaching hospital. There were only five cases during the eight months prior to the outbreak period (P less than 0.0001). Initial measures, including category-specific isolation and education, did not limit the spread of the outbreak of a strain of MRSA. This prompted institution of additional measures including (1) strict isolation of all infected and colonized cases; (2) prospective microbiological surveillance to detect additional cases; (3) multiple site cultures of identified cases to determine the extent of colonization; (4) employee and environment surveillance; (5) antibiotic decolonization of patients and employees; and (6) educational efforts. The highest number of personnel carriers were noted in one of the critical care units where most of the cases occurred. The decolonization protocol was 100% effective for personnel carriers. The incidence of nosocomial cases of MRSA fell to zero in the five months following the implementation of the strategy. The cost of the entire eradication process was approximately half that of treating a single MRSA bacteremia.     

An epidemiological survey of methicillin-resistant Staphylococcus aureus in a tertiary referral hospital

Over a 30-month period from July 1995 to December 1997, new detections of methicillin-resistant Staphylococcus aureus (MRSA) were prospectively studied in a tertiary referral hospital. The aims of the study were to determine the incidence of colonization of patients admitted to each of the hospital's 39 clinical units and ascertain where each patient had become colonized. Epidemiological information (time to detection, ward movement, admission to other hospitals, data on MRSA isolations in hospital wards) and phage typing were used by the hospital's infection control unit to make this determination. Routine containment procedures included cohorting, flagging and triclosan body washes. Surveillance cultures were collected infrequently. Patients known to be colonized with MRSA were excluded from orthopaedic and haematology wards. During the study period, 995 patients were found to be newly colonized. The incidence of colonization varied from nil to 72 per 1000 admissions, being highest in the main intensive care unit and in services which frequently used that unit. The incidence of colonization in elective orthopaedic surgery (< 1 per 1000) and haematology (3 per 1000) was very low. Determining the place where patients acquired MRSA was made difficult by the high frequency of endemic phage types and frequent patient transfer between wards. Epidemiological data suggested that the main intensive care unit and surgical wards nursing patients with colorectal, urological and vascular diseases were the places where most patients became colonized. MRSA was never acquired by patients nursed in wards which practised an exclusion policy towards patients known to be colonized with MRSA. Our data suggest that in tertiary referral hospitals, where MRSA is not only endemic but frequently imported from other hospitals, it is possible to establish areas where MRSA is never acquired.     

Control of a hospital outbreak of methicillin-resistant Staphylococcus aureus infections: value of an isolation unit

An outbreak of methicillin- and gentamicin-resistant Staphylococcus aureus infections started in a university hospital after a patient, who was not known to be colonized, was admitted. During a 3-month period 15 surgical or geriatric patients and five staff were found to be infected or colonized by the epidemic strain in five surgical/orthopaedic wards, a geriatric ward, the intensive care unit and the isolation unit. Difficulties in controlling the outbreak arose when two patients who initially had negative bacteriological screening results were returned to general wards. Both patients were subsequently shown to be colonized and caused outbreaks which led to the further closure of two general wards. There was strong circumstantial evidence to suggest that physiotherapy staff were involved with the spread of the epidemic strain. Control of the outbreak was achieved by more strict isolation of 'negative' patient contacts as well as colonized/infected patients and increasing the level of staffing on the separate isolation unit.     

Antimicrobial use and methicillin-resistant Staphylococcus aureus in a large nursing home

INTRODUCTION: In 1997, 18% of Staphylococcus aureus clinical isolates at the Wisconsin Veterans Home were resistant to methicillin. By 2002, 51% were resistant. METHODS: We determined the antibiotic sensitivity pattern of our methicillin-resistant S. aureus (MRSA) isolates as well as changes in utilization of specific antibiotics between two time periods. We reasoned that antibiotics with activity against methicillin-sensitive S. aureus (MSSA), but not MRSA, might be driving the overgrowth of MRSA. RESULTS: In our facility, MRSA is usually resistant to quinolones; MSSA is usually sensitive. Both MSSA and MRSA are usually sensitive to TMP-sulfa. An increased percentage of S. aureus resistant to methicillin (18%) was associated with a 42% increase in quinolone use and a 37% decrease in TMP-sulfa use. CONCLUSION: Our analysis and previous reports suggest that replacement of TMP-sulfa by quinolones could be selecting MRSA in our facility. This conclusion, however, is speculative, based on association, and requires confirmation.     

An outbreak of methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit.

OBJECTIVE: To describe the epidemiologic and molecular investigations that successfully contained an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) in a neonatal intensive care unit (NICU). DESIGN: Isolates of MRSA were typed by pulsed-field gel electrophoresis (PFGE) and S. aureus protein A (spa). SETTING: A level III-IV, 45-bed NICU located in a children's hospital within a medical center. PATIENTS: Incident cases had MRSA isolated from clinical cultures (eg, blood) or surveillance cultures (ie, anterior nares). INTERVENTIONS: Infected and colonized infants were placed on contact precautions, cohorted, and treated with mupirocin. Surveillance cultures were performed for healthcare workers (HCWs). Colonized HCWs were treated with topical mupirocin and hexachlorophene showers. RESULTS: From January to March 2001, the outbreak strain of MRSA, PFGE clone B, was harbored by 13 infants. Three (1.3%) of 235 HCWs were colonized with MRSA. Two HCWs, who rotated between the adult and the pediatric facility, harbored clone C. One HCW, who exclusively worked in the children's hospital, was colonized with clone B. From January 1999 to November 2000, 22 patients hospitalized in the adult facility were infected or colonized with clone B. Spa typing and PFGE yielded concordant results. PFGE clone B was identified as spa type 16, associated with outbreaks in Brazil and Hungary. CONCLUSIONS: A possible route of MRSA transmission was elucidated by molecular typing. MRSA appears to have been transferred from our adult facility to our pediatric facility by a rotating HCW. Spa typing allowed comparison of our institution's MRSA strains with previously characterized outbreak clones.     

Community-associated meticillin-resistant Staphylococcus aureus strains as a cause of healthcare-associated infection

Community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) was first noticed as a cause of infection in community-based individuals without healthcare contact. As the global epidemic of CA-MRSA has continued, CA-MRSA strain types have begun to emerge as a cause of healthcare-associated infections (HAIs) and hospital outbreaks have occurred worldwide. In areas where CA-MRSA clones have become established with high prevalence, for example USA300 (ST8-IV) in the USA, CA-MRSA are beginning to supplant or overtake traditional healthcare-associated MRSA strains as causes of HAI. The emergence of CA-MRSA as a cause of HAI puts a wider group of hospitalised patients, healthcare workers and their community contacts potentially at risk of MRSA infection. It also exposes CA-MRSA strains to the selective pressure of antibiotic use in hospitals, potentially resulting in increased antibiotic resistance, challenges traditional definitions of CA-MRSA and hampers control efforts due to the constant re-introduction of MRSA from an emerging community reservoir. There is thus an urgent need to clarify the definitions, prevalence and epidemiology of CA-MRSA and to develop systems for the identification and control of these organisms in the community, in hospitals and other healthcare facilities, and at the community–hospital interface.     

Effect of delayed infection control measures on a hospital outbreak of methicillin-resistant Staphylococcus aureus

All patients positive for methicillin-resistant Staphylococcus aureus (MRSA) at the University Hospitals of Geneva, Switzerland, between 1989 and 1997 (N = 1771) were included in a cohort study to evaluate the consequences of delayed containment of a hospital-wide outbreak occurring during a 4-year absence of MRSA control measures. The effects of efforts to control both the MRSA reservoir and the number of bacteraemic patients were assessed. Intensive infection control measures were initiated in 1993 and included patient screening, on-site surveillance, contact isolation, a computerized alert system, and hospital-wide promotion of hand hygiene. An increase in the rate of new MRSA-infected or -colonized patients was observed between 1989 and 1994 (from 0.05 to 0.60 cases per 100 admissions), which subsequently decreased to 0.24 cases in 1997 (P<0.001). However, the proportion of laboratory-documented methicillin-resistant isolates among all S. aureus showed little variation in the years from 1993 onwards (range, 19-24%), reflecting the result of an increase in the number of screening cultures. The annual number of patients with MRSA bacteraemia strongly correlated with the hospital-wide prevalence of MRSA patients (R(2)= 0.60; P = 0.01) and the rate of new MRSA patients (R(2)= 0.97; P<0.001). Consequently, the attack rate of nosocomial MRSA bacteraemia served as an excellent marker for the MRSA patient reservoir. In conclusion, despite delayed implementation, infection control measures had a substantial impact on both the reservoir of MRSA patients and the attack rate of MRSA bacteraemia.     

Epidemiology of methicillin-resistant Staphylococcus aureus at a university hospital in the Canary Islands.

OBJECTIVES: To describe the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) at a university hospital in Tenerife, Canary Islands, during a 40-month period and to evaluate the effectiveness of the application of control measures. DESIGN: Laboratory-based surveillance, medical charts and microbiological records review, and characterization of strains by pulsed-field gel electrophoresis (PFGE) were used to describe the epidemiology. Infection control practices were introduced as an intervention. SETTING: A 650-bed, tertiary-care university hospital. SUBJECTS: Patients with clinical and nasal isolates of MRSA and colonized staff members. RESULTS: The rate of nosocomial MRSA infections was 32.5% for 1997, 17.9% for 1998, 14.5% for 1999, and 25.6% during the first 4 months of 2000. The major sites of isolation for nosocomial MRSA infection included surgical wounds (25%) and the lower respiratory tract (24%). Intensive care units and surgical specialties had more frequent MRSA cases. Characteristics associated with nosocomial MRSA isolates included prior use of intensive antibiotic therapy, prolonged hospital stays, major underlying illness, invasive procedures, and older age. PFGE type A (subtype A1) was the strain most frequently found and the only PFGE type involved in clusters. CONCLUSIONS: Surveillance cultures and contact droplet precautions were followed by decreased rates for 2 years. Nevertheless, the spread of PFGE subtype A1 to many different areas of the hospital and the increase in incidence during the first third of 2000 indicates either that surveillance cultures were not used widely enough or that compliance with isolation measures was suboptimal.     

医院感染耐甲氧西林金黄色葡萄球菌耐药性与SCCmec分型及同源性研究

目的 研究医院耐甲氧西林金黄色葡萄球菌(MRSA)的耐药性及分子流行病学特点,为预防和控制医院感染提供参考.方法 采用药敏纸片法(K-B法)、SCCmec分型及葡萄球菌A蛋白(spa)分型技术,2009年3-4月对烧伤科、ICU、呼吸内科、急诊科、血液内科、儿童急救科和儿童呼吸科住院患者、医务人员及环境分离的MRSA,进行了药敏试验和同源性分析,并检测其杀白细胞毒素(pvl)基因.结果 从1352份标本中分离出108株金黄色葡萄球菌,MRSA为54株占50.0％,主要分离于烧伤科42株占77.8％;分离的临床菌株总体耐药率较高,除万古霉索外耐药率均＞50.0％,未发现万古霉素耐药株;SCCmec分型结果显示,54株MRSA以Ⅲ型为主占68.5％,pvl基因均为阴性;进行spa分型研究的23株MRSA中,22株为t030,1株为t2270,呈现高度的克隆一致性.结论 医护人员MRSA带菌率较高,部分医务人员、住院患者和环境中分离的MRSA有较高的同源性,存在人与人和人与环境之间的MRSA传播.     

2008-2014年南昌某医院金黄色葡萄球菌耐药谱及变化趋势

摘要:目的 了解2008-2014年医院金黄色葡萄球菌耐药变化趋势及MRSA感染下降的原因,为更加有效地控制及预防MRSA感染提供依据。方法 利用院内监测数据分析2008-2014年金黄色葡萄球菌的耐药状况、科室来源、分离部位及重点科室MRSA感染率的变迁及原因。结果 (1)2008-2014年共计分离到2525株金黄色葡萄球菌,主要来源科室包括呼吸科、烧伤科、脑外科、骨科、ICU和急诊科。(2)青霉素、苯唑西林、氨苄西林/舒巴坦、亚胺培南、四环素、红霉素、利福平、林可霉素、庆大霉素、环丙沙星、莫西沙星的耐药呈下降趋势;复方新诺明耐药小幅上升;而喹奴普汀/达福普汀、利奈唑烷、万古霉素耐药率维持2%以下。(3)烧伤科、ICU的MRSA感染率一直维持高水平;骨科和呼吸科呈明显下降。结论 2008-2014年南昌某医院金黄色葡萄球菌耐药呈下降趋势,但不同科室MRSA感染率改变趋势不同。应保持目前的抗生素管理模式,对高水平MRSA感染科室制定更加有效的管理措施,切实降低MRSA感染率。     

Spread and control of a methicillin-resistant Staphylococcus aureus in an academic hospital

Between December 1988 and March 1989 twelve patients in the Utrecht University Hospital developed an infection with a methicillin-resistant Staphylococcus aureus (MRSA). Twenty other patients and 39 personnel members became colonized with the same MRSA strain. In spite of early isolation measures, progression of this epidemic was probably caused by the extreme degree of contagiousness of the first patient, who had a drug-induced allergic skin eruption. It seems likely that spread occurred via personnel and via a computer tomographic scanner. To contain the epidemic it was necessary to institute a special isolation ward with dedicated personnel. Although several MRSA strains have been introduced in the University Hospital since 1986, the strain we describe here is the only one which spread epidemically.     

The relationship of a clonal outbreak of Enterococcus faecium vanA to methicillin-resistant Staphylococcus aureus incidence in an Australian hospital

Australian isolates of vancomycin-resistant enterococci (VRE) have been widely scattered geographically, predominantly polyclonal and of the VanB phenotype. Forty-nine VRE were isolated from 47 patients in our hospital from October 1996 to December 1999. Forty-four of these VRE were Enterococcus faecium with a vanA glycopeptide resistance genotype. Four isolates were pathogenic. Thirty-five VRE were from an outbreak in the Renal and Infectious Diseases Units over a four-month period. Pulsed-field gel electrophoresis (PFGE) demonstrated that 41 of the 49 VRE were indistinguishable or closely related. Enhanced environmental cleaning, strict contact isolation of colonized patients and reducing inpatient admissions terminated the epidemic. Cohorting of methicillin-resistant Staphylococcus aureus (MRSA)-positive patients was restricted because VRE patients occupied the isolation facilities. This resulted in a statistically significant increase in MRSA infections across the hospital. VRE epidemics have the ability to influence the epidemiology of other nosocomial pathogens when infection control resources are exhausted.     

Three-year survey of community-acquired methicillin-resistant Staphylococcus aureus producing Panton-Valentine leukocidin in a French university hospital

A retrospective survey was conducted at Bicêtre Hospital, France from January 2001 to September 2003 to screen for S. aureus isolates with a typical phenotype previously involved in necrotizing pneumonia in France. They were resistant to oxacillin and kanamycin, of intermediate susceptibility to fusidic acid, and susceptible to tobramycin and fluoroquinolones. Seventeen isolates were found and 16 were viable. The Panton-Valentine leukocidin (PVL) genes, various toxin genes and SCCmec IV and agr3 alleles were detected in all isolates. The clonal origin of these isolates was demonstrated by pulsed-field gel electrophoresis. Fourteen isolates were community-acquired methicillin-resistant Staphylococcus (CA-MRSA) isolated from previously healthy patients with skin or soft tissue infections. Three infections were of nosocomial origin, underlining that these PVL-producing CA-MRSA strains may also be hospital acquired. Five CA-MRSA isolates with an identical resistance phenotype collected in a neighbouring teaching hospital (H?pital Pitié-Salpétrière, Paris, France) were also PVL positive. Three isolates were clonally related to those of the Bicêtre Hospital whereas two were not. This retrospective study identified PVL-producing CA-MRSA in two Parisian hospitals. The incidence at Bicêtre Hospital was 0.8% of all S. aureus and 2% of all MRSA isolated. Our data indicate that these MRSA isolates might become hospital acquired.     

MRSA Pediatric clone expressing ermC plus lnuA genes causing nosocomial transmission and healthcare workers colonization in a neonatal intensive care unit

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of both nosocomial and community-acquired infections. We describe an outbreak caused by the MRSA Pediatric clone expressing an unusual lincosamide resistant phenotype. Between January and May 2006, an MRSA outbreak was detected at the Neonatal Unit of Hospital Interzonal General de Agudos “Evita”, Buenos Aires Province, Argentina that affected ten patients. Seven isolates from seven patients plus five MRSA recovered from health care workers (nasal carriage) were studied. Two phenotypes were observed: (i) ELCi (10), resistance to erythromycin and lincomycin and inducible resistance to clindamycin; (ii) ELiCi (2), resistance to erythromycin and inducible resistance to lincomycin and clindamycin. All 12 MRSA were resistant to oxacillin, erythromycin and gentamicin. Isolates expressing the ELCi-phenotype showed lincomycin MIC values between 16 and 32 mg/L, while the remaining 2 isolates with ELiCi-phenotype presented a MIC value of 0.5 mg/L. No differences were observed between the clindamycin MIC values in both phenotypes, ranging 0.25–0.5 mg/L. Isolates showing ELCi-phenotype harbored ermC plus lnuA genes, and the other two only ermC gene. All 12 isolates were genetically related and belonged to the Pediatric clone (ST100) harboring a new variant of SCCmecIV. This is the first MRSA outbreak expressing an unusual ELCi phenotype due to a combination of ermC plus lnuA genes.     

Outbreak of methicillin-resistant Staphylococcus aureus in two nursing homes in Central Norway

Until recently, infections with methicillin-resistant Staphylococcus aureus (MRSA) have mainly been associated with hospital outbreaks in Norway. However, increasingly cases are contracted outside hospitals. This paper reports the first two outbreaks of MRSA in two nursing homes in central Norway, affecting 23 residents and five staff members. Pulsed-field gel electrophoresis analysis showed that all strains from nursing home A were identical and that the strains from nursing home B were genotypically similar with one or two band differences. Multi-locus sequence typing (MLST) showed that the strains from the two nursing homes belong to clonal complex 45, with each strain being a single-locus variant of sequence type 45 (ST 45), a well-known European epidemic strain. No evident source of the two outbreaks was found, and there was no obvious connection between the two outbreaks. The latter is also supported by the minor differences observed by MLST, suggesting a connection at some time in the past. The outbreaks led to a heavier workload and economic strain on both nursing homes. The outbreak in nursing home A was brought to an end, whereas two residents remained colonized in nursing home B despite several eradication attempts. These outbreaks show the potential for MRSA spread in a nursing home. If the prevalence of MRSA in Norway continues to increase, nursing home staff and residents may have to be included in the groups to be screened for MRSA upon hospital admission.     

Reducing the potential for phlebotomy tourniquets to act as a reservoir for meticillin-resistant Staphylococcus aureus

The contamination rate of phlebotomy tourniquets with meticillin-resistant Staphylococcus aureus (MRSA) was assessed, and it was determined whether this could be reduced by changes in practice or by the use of a physical barrier. Initially, the tourniquets of both preregistration house officers and phlebotomists were investigated, but as phlebotomists reported significantly more venepunctures daily, the trial continued solely with phlebotomists. Each day, the phlebotomists were supplied with a fresh sterile tourniquet, and after use, the tourniquets were swabbed and cultured. The rate of contamination with MRSA was 32 of 131 (25%) tourniquets. An audit of hand hygiene practice was undertaken and revealed that phlebotomists were performing hand decontamination inadequately between patients and wore wristwatches while working. Education comprising standard infection control methods to encourage good practice was given. After this, a polythene strip was used as a barrier by half of the phlebotomists during all venepunctures. Tourniquets were cultured and replaced daily as before. During this stage of the trial, the rates of contamination were 1 of 46 tourniquets (using a polythene strip) and 1 of 42 tourniquets (without using a polythene strip). In conclusion, phlebotomy tourniquets may be potential vectors for transferring bacteria, including MRSA. Contamination rates, and hence potential risk, can be reduced if hand decontamination is performed. This suggests that contamination of tourniquets is via phlebotomists' hands, not directly from patients' skin. Hand hygiene should be regarded as the most important method by which the spread of organisms can be reduced.