Antimicrobial drug use and methicillin-resistant Staphylococcus aureus, Aberdeen, 1996-2000

Similar to many hospitals worldwide, Aberdeen Royal Infirmary has had an outbreak of methicillin-resistant Staphylococcus aureus (MRSA). In this setting, the outbreak is attributable to two major clones. The relationships between antimicrobial use and MRSA prevalence were analyzed by time-series analysis. From June 1997 to December 2000, dynamic, temporal relationships were found between monthly %MRSA and previous %MRSA, macrolide use, third-generation cephalosporin use, and fluoroquinolone use. This study suggests that use of antimicrobial drugs to which the MRSA outbreak strains are resistant may be an important factor in perpetuating the outbreak. Moreover, this study confirmed the ecologic effect of antimicrobial drug use (i.e., current antimicrobial use) may have an effect on resistance in future patients. Although these results may not be generalized to other hospitals, they suggest new directions for control of MRSA, which has thus far proved difficult and expensive.     

Antibiotic susceptibility and genotypic characterization of methicillin-resistant Staphylococcus aureus strains in eastern France

We studied changes over four years in the characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated in a French university hospital by analysis of antibiotic susceptibility and restriction fragment length polymorphism using pulsed field gel electrophoresis. Changes were considered in relation to regional and national frameworks. The proportion of gentamicin-susceptible methicillin-resistant S. aureus (GS-MRSA) among MRSA increased from 22.6% in 1994 to 86.8% in 1998. We first isolated strains of GS-MRSA susceptible to tobramycin and amikacin (TKS-MRSA) in 1996 from patients in eight wards. The number of TKS-MRSA strains per 100 MRSA was 6.1 in 1997, 14.5 in 1998, and 18.9 in 1999. Pattern A, the major DNA pattern identified, accounted for 78.6% of isolates in 1998. This pattern was found in TKS-MRSA and TKR-MRSA strains, but not in Gentamicin-resistant MRSA strains (GR-MRSA). Fitness analysis showed that GR-MRSA strains had much lower replication rates than GS-MRSA strains, but there was no difference between TKS-MRSA and TKR-MRSA strains. Aminoglycoside consumption remained constant between 1994 and 1998. The spread of TKS-MRSA in our hospital since 1996 may relate to the "total use threshold", as the level of tobramycin/amikacin use is below that required for selection of TKR-MRSA.     

Community-acquired methicillin-resistant Staphylococcus aureus,Finland

Methicillin-resistant Staphylococcus aureus (MRSA) is no longer only hospital acquired. MRSA is defined as community acquired if the MRSA-positive specimen was obtained outside hospital settings or within 2 days of hospital admission, and if it was from a person who had not been hospitalized within 2 years before the date of MRSA isolation. To estimate the proportion of community-acquired MRSA, we analyzed previous hospitalizations for all MRSA-positive persons in Finland from 1997 to 1999 by using data from the National Hospital Discharge Register. Of 526 MRSA-positive persons, 21% had community-acquired MRSA. Three MRSA strains identified by phage typing, pulsed-field gel electrophoresis, and ribotyping were associated with community acquisition. None of the strains were multiresistant, and all showed an mec hypervariable region hybridization pattern A (HVR type A). None of the epidemic multiresistant hospital strains were prevalent in nonhospitalized persons. Our population-based data suggest that community-acquired MRSA may also arise de novo, through horizontal acquisition of the mecA gene.     

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.     

Personal hygiene and methicillin-resistant Staphylococcus aureus infection

Methicillin-resistant Staphylococcus aureus (MRSA) infections outside the healthcare setting are an increasing concern. We conducted a case-control study to investigate an MRSA outbreak during 2002-2003 in a Missouri prison and focused on hygiene factors. Information on sociodemographic characteristics, medical history, and hygiene practices of study participants was collected by interview and medical record review. Logistic regression was used to evaluate MRSA infection in relation to hygiene factors individually and as a composite hygiene score; potential confounding factors were controlled. Selected MRSA isolates were analyzed by pulsed-field gel electrophoresis (PFGE). MRSA infection was significantly associated with a low composite hygiene score. Transmission among prison inmates appeared to be responsible for this outbreak. PFGE analysis showed that isolates were indistinguishable and associated with community-onset MRSA infections in other US prisons. Improving hygiene practices and environmental conditions may help prevent and interrupt future MRSA outbreaks in prison settings.     

Outbreak of methicillin-resistant Staphylococcus aureus ST398 in a Dutch nursing home

We describe an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) ST398 in a nursing home in the Netherlands. Seven residents and 4 healthcare workers were identified with MRSA ST398, but 2 of the healthcare workers carried other strains. This study demonstrates that MRSA ST398 can spread in nursing homes.     

Community-associated methicillin-resistant Staphylococcus aureus, Canada

A total of 184 methicillin-resistant Staphylococcus aureus (MRSA) strains were collected from patients who sought treatment primarily for skin and soft tissue infections from January 1, 1999, to March 31, 2002, in east-central Saskatchewan, Canada. Molecular subtyping analysis using pulsed-field gel electrophoresis showed 2 major clusters. Cluster A (n = 55) was composed of a multidrug-resistant MRSA strain associated with a long-term care facility and was similar to the previously reported nosocomial Canadian epidemic strain labeled CMRSA-2. Cluster B (n = 125) was associated with cases identified at community health centers and was indistinguishable from a community-associated (CA)-MRSA strain identified previously in the United States (USA400). Cluster B remained susceptible to a number of classes of antimicrobial agents and harbored the lukF-PV and lukS-PV toxin genes. Over 50% of both clonal groups displayed high-level resistance to mupirocin. This is the first report of the USA400 strain harboring the lukF-PV and lukS-PV toxin genes in Canada.     

Community-associated methicillin-resistant Staphylococcus aureus and healthcare risk factors

To determine frequency of methicillin-resistant Staphylococcus aureus infections caused by strains typically associated with community-acquired infections (USA300) among persons with healthcare-related risk factors (HRFs), we evaluated surveillance data. Of patients with HRFs, 18%-28% had a "community-associated" strain, primarily USA300; of patients without HRFs, 26% had a "healthcare-associated" strain, typically USA100.     

Antimicrobial therapy for methicillin-resistant Staphylococcus aureus colonization in residents and staff of a Veterans Affairs nursing home care unit.

OBJECTIVE: To evaluate the effect of antimicrobial therapy on patients and staff colonized with methicillin-resistant Staphylococcus aureus (MRSA) in a skilled nursing facility and to assess the role of the environment as a potential reservoir for MRSA in the nursing home setting. DESIGN: As part of a comprehensive program to control an MRSA outbreak in a nursing home, patients and staff colonized with MRSA received 1 of 3 antimicrobial decolonization regimens depending upon the site and extent of colonization. Followup cultures were performed during therapy and on days 2, 7, 14, and 30 following the completion of therapy. Cultures of the patients' inanimate environment (pajamas, sheet, and floor) were obtained during and after therapy. Antimicrobial susceptibility tests were performed on 54 MRSA isolates obtained before and 44 MRSA isolates recovered after therapy. SETTING: A 120-bed Veterans Affairs nursing home care unit. PARTICIPANTS: Thirty-six patients and 7 staff nurses colonized with MRSA at 1 or more sites. INTERVENTION: Decolonization therapy with rifampin, trimethoprim-sulfamethoxazole, and clindamycin used alone or in various combinations for 5 or 10 days in conjunction with other infection control measures employed to combat the MRSA outbreak. RESULTS: Twenty (56%) of the 36 NHCU patients were either persistently colonized or became recolonized with MRSA during the 30-day followup period. Positive cultures on day 3 during therapy frequently identified patients who subsequently exhibited persistent or recurrent colonization. Before therapy, 92% of MRSA isolates were susceptible to rifampin, whereas only 43% of the isolates obtained after therapy were susceptible. Sixteen (80%) of 20 patients with persistent or recurrent colonization had rifampin-resistant strains of MRSA isolated after therapy. Twenty-three (18%) of 125 environmental cultures obtained during and after therapy from patients who exhibited persistent or recurrent colonization were positive for MRSA, in contrast to 9 (8%) of 107 from patients who were successfully decolonized. CONCLUSIONS: The decolonization component of the outbreak control program was judged to be ineffective and potentially hazardous because colonization persisted or recurred in more than half of the patients, and substantial antimicrobial resistance was noted in MRSA stains isolated after therapy. Resistance, especially to rifampin, and possibly re-acquisition of MRSA from other human or environmental sources were 2 factors that appeared to impede the decolonization effort.     

Evolution of community- and healthcare-associated methicillin-resistant Staphylococcus aureus

Staphylococcus aureus is a prominent cause of human infections globally. The high prevalence of infections is compounded by antibiotic resistance—a significant problem for treatment. Methicillin-resistant S. aureus (MRSA) is endemic in hospitals and healthcare facilities worldwide, and is an increasingly common cause of community-associated bacterial infections in industrialized countries. Although much focus is placed on the role of S. aureus as a human pathogen, it is in fact a human commensal organism that has had a relatively long coexistence with the human host. Many S. aureus infections can be explained by host susceptibility or other predisposing risk factors. On the other hand, the emergence/re-emergence of successful S. aureus clones (referred to as epidemic waves) suggests a rapid bacterial adaption and evolution, which includes the emergence of antibiotic resistance and increased virulence and/or transmissibility. It is within this context that we review our understanding of selected S. aureus epidemic waves, and highlight the use of genome sequencing as a means to better understand the evolution of each lineage.     

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.     

Serial survey of methicillin-resistant Staphylococcus aureus nasal carriage among residents in a nursing home

OBJECTIVE: To study the natural course of nasal colonization by methicillin-resistant Staphylococcus aureus (MRSA) among residents in a nursing home. DESIGN: A cohort study with eight surveys of nasal cultures over 15 months. SETTING: A community nursing home in Chicago, Illinois. PARTICIPANTS: Between 117 and 129 residents of the nursing home in each survey. RESULTS: MRSA carriers were present throughout the study period. On the average, 24.4% (range: 17.1% to 34.2%) of the residents carried S aureus, and 35.3% (range: 20% to 62.5%) of the isolates were methicillin resistant at each survey. The carrier state was persistent or transient and was affected little by a roommate's carrier status. Approximately 70% to 80% of residents who were bedridden or who had decubitus ulcers or foreign bodies carried MRSA at least once during the study period. Residents' prior hospitalization was not associated with MRSA carriage. CONCLUSION: This study demonstrated that MRSA was perpetuated in the nursing home by persistently or intermittently colonizing debilitated residents who required more intensive nursing care and that the prior hospitalization of the residents was not an important cause of its perpetuation.     

Community-associated methicillin-resistant Staphylococcus aureus isolates causing healthcare-associated infections

We noted a marked increase in healthcare-associated (HA) methicillin-resistant Staphylococcus aureus (MRSA) infections caused by isolates phenotypically consistent with community-associated (CA)-MRSA strains. To study this trend, we retrospectively examined all HA-MRSA isolates from patients in our institution during 1999-2004. An isolate was considered an SCCmecIV phenotype if it had antimicrobial drug susceptibilities consistent with typical CA-MRSA isolates. Our phenotypic definition was validated in a limited subset of isolates by SCCmec genotype, pulsed-field gel electrophoresis, and multilocus sequence typing. Among 352 patients with HA-MRSA isolates, SCCmecIV phenotype increased from 17% in 1999 to 56% in 2003 (p < 0.0001). Antimicrobial drug-susceptibility phenotype and genotype were consistent in 21 (91%) of 23 isolates. In a multivariate model, the SCCmec type IV phenotype was independently associated with wound culture source, later year of collection, and MRSA isolated earlier during hospitalization. In conclusion, MRSA isolates phenotypically similar to CA strains have become the predominant isolates associated with HA-MRSA in our hospital.     

Antimicrobial ointments and methicillin-resistant Staphylococcus aureus USA300

We tested 259 methicillin-resistant Staphylococcus aureus isolates and 2 USA300 ATCC type strains for susceptibility to bacitracin and neomycin contained in over-the-counter antibacterial ointments. Resistance to both bacitracin and neomycin was found only in USA300. The use of over-the counter antimicrobial drugs may select for the USA300 clone.     

Community-associated methicillin-resistant Staphylococcus aureus in pediatric patients

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections increased from 2000 to 2003 in hospitalized pediatric patients in Houston. CA-MRSA was associated with greater illness than was infection with methicillin-susceptible strains. Children with CA-MRSA were younger and mostly African American. Of MRSA isolates, 4.5% had the inducible macrolide-lincosamide-streptogramin B phenotype.     

Risk factors for colonization with methicillin-resistant Staphylococcus aureus among nursing home residents

Risk factors predictive of methicillin-resistant Staphylococcus aureus (MRSA) colonization in 786 of 910 nursing home residents were evaluated. A customized questionnaire was completed by theresidents, who were screened for MRSA. The risk factors significantly associated with MRSA colonization were male sex, age >80 years, residence in the nursing home for 相似文献