We report the results of a province-wide quality control program in which five methicillin-resistant Staphylococcus aureus strains were circulated to all Ontario laboratories (hospital, private, and public health laboratories) on nine occasions between 1980 and 1989. The level of expression of methicillin resistance in each of the isolates was determined by performing viable colony counts on serial dilutions of methicillin in agar, and each isolate was assigned to an expression class according to previous published criteria (A. Tomasz, S. Nachman, and H. Leaf, Antimicrob. Agents Chemother. 35:124-129, 1991). Over this time there was an improvement in the performance of laboratories in the recognition of three strains that were relatively easy to detect (strains B, C, and E). These strains were of expression class II, and 98% of laboratories reported correct identifications in 1986. Performance in identifying two strains (strains A and D) of expression class I remained poor. Strain A was circulated in two surveys in 1987 and 1989, and laboratories were sent a questionnaire requesting details of the methods used in those two surveys. The methods used by the laboratories were classified into three categories: disk diffusion, single-plate screening by agar incorporation, and automated methods, which included premanufactured MIC panels. Between the 1987 and 1989 surveys, there was no change in the performance of the disk diffusion test (60% correct on both occasions), but there was improvement in the sensitivity of the agar incorporation test (36% correct in 1987 and 84% correct in 1989) and in automated methods (43% correct in 1987 and 79% correct in 1989). Over a decade, there was overall improvement in the performance of laboratories in detecting easy-to-detect strains, but there were difficulties in detecting organisms of low expression class, and an organism of very low expression class should be designated as a control organism for routine testing of methicillin-resistant s. aureus isolates.
A 26-year-old male was treated for acute hepatitis due to Epstein-Barr virus and infectious mononucleosis in our hospital. At 2 weeks after admission, there was relapse with high fever. A blood culture detected methicillin-resistant Staphylococcus aureus. A two-dimensional echocardiogram revealed severe aortic regurgitation and vegetation on the left coronary cusp of the aortic valve. The diagnosis was active infective endocarditis due to methicillin-resistant Staphylococcus aureus in the acute phase of infectious mononucleosis. Following preoperative administration of vancomycin, the aortic valve was replaced with a Carbomedics prosthetic valve. The aortic valve was bicuspid, and the right cusp and non-coronary cusp were conjoined. As the focus of infection was localized to the left coronary cusp, the infected tissue was fully removed with resection of all the cusps. Although fever persisted long after the operation, the blood culture became negative for methicillin-resistant Staphylococcus aureus, and repeated echocardiograms including transesophageal echocardiogram showed no prosthetic valve infection. Vancomycin was administered until the C-reactive protein became negative at 45 days after the operation.
Laboratory-based surveillance of methicillin-resistant Staphylococcus aureus (MRSA) monitors the baseline occurrence of different genotypes and identifies strains and transmission chains responsible for outbreaks. The consequences of substituting pulsed-field gel electrophoresis (PFGE) with spa typing as a first-line typing method were analyzed by typing 589 strains isolated between 1997 and 2006, with a focus on both short- and long-term correspondence between the PFGE and spa typing results. The study, covering these ten years, included all Finnish MRSA blood isolates and representatives of the two most prevalent MRSA strains (PFGE types FIN-4 and FIN-16) in Finland. In addition, all sporadic isolates from 2006 were included. spa typing was more expensive but approximately four times faster to perform than PFGE. Nearly 90% of FIN-4 and FIN-16 isolates showed consistent spa types, t172 and t067, respectively. spa typing predicted the PFGE result of the blood isolates by a Wallace coefficient of 0.9009, recognized internationally successful strains (t041, t067) to be common also in Finland, and identified a separate cluster of isolates, also related in time and place among the FIN-4 strains. Additional typing by another method was needed to provide adequate discrimination or to characterize isolates with a newly recognized spa type in Finland.
To investigate the prevalence of concurrent methicillin-resistant Staphylococcus aureus (MRSA) colonization in people and pets in the same household with a person or pet with an MRSA infection and to compare MRSA isolates by use of molecular techniques.
24 dogs, 10 cats, and 56 humans in part 1 and 21 dogs, 4 cats, and 16 humans in part 2 of the study.
In both parts of the study, nasal swab specimens were collected from humans and nasal and rectal swab specimens were collected from household pets. Selective culture for MRSA was performed, and isolates were typed via pulsed-field gel electrophoresis (PFGE) and spa typing. Households were defined as positive when MRSA was isolated from at least 1 person (part 1) or 1 pet (part 2).
In part 1, 6 of 22 (27.3%) households were identified with MRSA colonization in a person. In these households, 10 of 56 (17.9%) humans, 2 of 24 (8.3%) dogs, and 1 of 10 (10%) cats were colonized with MRSA. In part 2, only 1 of 8 households was identified with MRSA colonization in a pet. Most MRSA isolates obtained from humans and pets in the same household were indistinguishable by use of PFGE.
The high prevalence of concurrent MRSA colonization as well as identification of indistinguishable strains in humans and pet dogs and cats in the same household suggested that interspecies transmission of MRSA is possible. Longitudinal studies are required to identify factors associated with interspecies transmission.
OBJECTIVE: We investigated a large outbreak of community-onset methicillin-resistant Staphylococcus aureus (MRSA) infections in southwestern Alaska to determine the extent of these infections and whether MRSA isolates were likely community acquired. DESIGN: Retrospective cohort study. SETTING: Rural southwestern Alaska. PATIENTS: All patients with a history of culture-confirmed S. aureus infection from March 1, 1999, through August 10, 2000. RESULTS: More than 80% of culture-confirmed S. aureus infections were methicillin resistant, and 84% of MRSA infections involved skin or soft tissue; invasive disease was rare. Most (77%) of the patients with MRSA skin infections had community-acquired MRSA (no hospitalization, surgery, dialysis, indwelling line or catheter, or admission to a long-term-care facility in the 12 months before infection). Patients with MRSA skin infections were more likely to have received a prescription for an antimicrobial agent in the 180 days before infection than were patients with methicillin-susceptible S. aureus skin infections. CONCLUSIONS: Our findings indicate that the epidemiology of MRSA in rural southwestern Alaska has changed and suggest that the emergence of community-onset MRSA in this region was not related to spread of a hospital organism. Treatment guidelines were developed recommending that beta-lactam antimicrobial agents not be used as a first-line therapy for suspected S. aureus infections.
Comment In: Infect Control Hosp Epidemiol. 2003 Jun;24(6):392-612828313
An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) occurred in a hospital without endemic MRSA, following the transfer of a patient colonized by MRSA from another hospital known to have a problem with endemic MRSA. Despite initial appropriate isolation and therapy to eradicate colonization of the organism, the index child relapsed 10 weeks after the last prior positive culture. Simultaneously, the organism was isolated from two other patients on the same ward, and subsequently at surgery from one child transferred to the neonatal intensive care nursery. Antimicrobial therapy for urinary tract infection likely impaired earlier identification of MRSA in the index case. Suppression with mupirocin rather than eradication may have resulted in inappropriate early discontinuation of infection control precautions. Control of the outbreak and eradication of the organism from all patients was successful after intensive surveillance and control measures, including strict isolation and cohorting. This outbreak suggests that infection control precautions and intensive screening of contacts, as well as positive cases, may be effective for control and eradication of MRSA from health care facilities with recent introduction of an epidemic strain.
BACKGROUND: Staphylococcus aureus is a frequent cause of serious infections. Methicillin-resistant S. aureus (MRSA) are resistant to almost all types of beta-lactam antibiotics and therefore represent a substantial medical problem. MATERIAL AND METHOD: In April 2006, the Department of Obstetrics at the Asker and Baerum hospital had an outbreak of MRSA that affected four newborns. The source for the infection was sought among family members, other patients and employees, and eradication was attempted. RESULTS: An employee was identified as the probable infectious source. Subsequent investigation identified 13 individuals infected by the same MRSA clone, which was Panton-Valentine-leukocidin (PVL) positive and therefore clearly a pathogen. 10 of the patients had MRSA disease, with 21 months between the first and the last identified case. For 5 of 13 patients MRSA was still detectable after the first attempt of eradication. For 2 patients, including one of the newborns, eradication has so far been unsuccessful and a third patient has acquired a new abscess after one year. INTERPRETATION: Issues connected to MRSA-screening of close contacts and eradication are resource-demanding and require careful consideration of strategy, especially for small children and families with chronic MRSA carriers. Updated detailed national guidelines for MRSA management are needed.
To report a multi-institution outbreak caused by a single strain of methicillin-resistant Staphylococcus aureus (MRSA).
Between September 19 and November 20, 1996 an index case and five secondary cases of nosocomial MRSA occurred on a 26 bed adult plastic surgery/burn unit (PSBU) at a tertiary care teaching hospital. Between November 11 and December 23, 1996, six additional cases were identified at a community hospital. One of the community hospital cases was transferred from the PSBU. All strains were identical by pulsed-field gel electrophoresis. MRSA may have contributed to skin graft breakdown in one case, and delayed wound healing in others. Patients required 2 to 226 isolation days.
A hand held shower and stretcher for showering in the hydrotherapy room of the PSBU were culture positive for the outbreak strain, and the presumed means of transmission. Replacement of stretcher showering with bedside sterile burn wound compresses terminated the outbreak. The PSBU was closed to new admissions and transfers out for 11 days during the investigation. Seven of 12 patients had effective decolonization therapy.
Environmental contamination is a potential source of nosocomial MRSA transmission on a burn unit. Notification among institutions and community care providers of shared patients infected or colonized with an antimicrobial resistant microorganism is necessary.
Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) represent an increasing problem in Norway, also in nursing homes and other institutions for long-term care. We describe an outbreak of MRSA in a nursing home in Oslo 2004-5.
The nursing home has six wards with 185 beds. The building is old, all rooms have toilets and sinks, but showers are shared. Standard screening procedures were carried out according to the national MRSA guide and by using the nursing home's infection control programme. Later on we used more extensive screening of staff and patients.
The outbreak started in a ward for short-term care, but spread to a ward for patients with dementia after some months. Ten patients, seven staff members and two relatives of infected persons were diagnosed with MRSA. All bacteria probably belonged to the same strain. Four staff members and five patients who were infected had pre-existing wounds or eczema. The nursing home was declared free of MRSA 20 months after the outbreak started, but one member of staff remained a carrier for two years, and one patient became a chronic carrier of MRSA. During the first six months, infected patients were restricted to their rooms, and standard eradication procedures were carried out for five days. Later on, we introduced cohort isolation for infected, exposed and recently treated patients, a different screening routine, a prolonged eradication procedure, restrictions on staff working elsewhere and more stringent precautions for visitors.
An old building and insufficient isolation procedures during the first phase of the outbreak contributed to spreading MRSA and prolonging the outbreak. Cohort isolation seemed to be the most important measure to control the outbreak. All nursing homes should have a designated single patient room for contact precautions. Long-term carriers of MRSA in nursing homes represent a big challenge.