Nasal carriage of methicillin-resistant Staphylococcus aureus among hospital staff and outpatients.

This study sought to determine the rate of nasal methicillin-resistant Staphylococcus aureus (MRSA) carriage among hospital staff and outpatients. Nasal swabs were obtained from 500 outpatients and 500 hospital staff. Hospital staff were 2.3-fold more likely to carry MRSA than were outpatients (6% vs 2.6%, P = .013).     

Nasal carriage of methicillin-resistant Staphylococcus aureus by hospital staff in north Jordan.

The nasal carriage of methicillin-resistant Staphylococcus aureus was detected in 550 hospital staff members of four hospitals in north Jordan. Of the 109 (19.8%) individuals tested who were nasal carriers of S. aureus, only 32 (5.8%) were found to be carriers of methicillin-resistant Staphylococcus aureus. The carriers were four doctors, 23 nurses, three laboratory technicians, one maid and an administrator. It was noted that 25 (78.1%) of these carriers were in constant contact with patients in operating theatres, surgical wards or intensive care units. It was not clear whether the carriers were short- or long-term carriers, or whether they were persistent sources of methicillin-resistant Staphylococcus aureus. Decontamination of these carriers was considered among other control measures to avoid the dangerous outcome of hospital outbreaks caused by this potential pathogen.     

Rates of carriage of methicillin-resistant and methicillin-susceptible Staphylococcus aureus in an outpatient population.

OBJECTIVES: To assess the prevalence of and the clinical features associated with asymptomatic Staphylococcus aureus colonization in a healthy outpatient population, and to compare the characteristics of colonizing methicillin-resistant S. aureus (MRSA) strains with those of strains causing infection in our community and hospital. SETTING: Outpatient military clinics. METHODS: Specimens were obtained from the nares, pharynx, and axillae of 404 outpatients, and a questionnaire was administered to obtain demographic and risk factor information. MRSA strains were typed by pulsed-field gel electrophoresis (PFGE) and evaluated for antibiotic susceptibility. Antibiograms of study MRSA strains were compared with those of MRSA strains causing clinical illness during the same time period. RESULTS: Methicillin-susceptible S. aureus (MSSA) colonization was present in 153 (38%) of the 404 asymptomatic outpatients, and MRSA colonization was present in 8 (2%). Detection of colonization was highest from the nares. No clinical risk factor was significantly associated with MRSA colonization; however, a tendency was noted for MRSA to be more common in men and in those who were older or who had been recently hospitalized. All colonizing MRSA strains had unique patterns on PFGE. In contrast to strains responsible for hospital infections, most colonizing isolates of MRSA were susceptible to oral antibiotics. CONCLUSIONS: MRSA and MSSA colonization is common in our outpatient population. Colonization is best detected by nares cultures and most carriers of MRSA are without apparent predisposing risk factors for acquisition. Colonizing isolates of MRSA are heterogeneous and, unlike nosocomial isolates, often retain susceptibility to other non-beta-lactam antibiotics.     

Nasal carriage of enterotoxin-producing Staphylococcus aureus among restaurant workers in Kuwait City.

Enterotoxin-producing Staphylococcus aureus is a common cause of staphylococcal food poisoning. To determine the incidence of carriage of enterotoxin-producing S. aureus in a sample of the healthy population in Kuwait city, restaurant workers in the city were screened for nasal carriage of S. aureus. 26.6% of 500 workers studied carried S. aureus and 86.6% of the S. aureus produced staphylococcal enterotoxins. 28% produced enterotoxin A, 28.5% produced enterotoxin B, 16.4% produced enterotoxin C and 3.5% produced enterotoxin D. Ten isolates produced both enterotoxins A and B or A and C. 73% of the isolates were untypeable with standard phages. However, 17.1%, 3% and 6% belonged to phage groups I, II and III respectively. The results demonstrated a high level of enterotoxigenic S. aureus carriage among restaurant workers which although lower than that reported for the general population and hospital workers may be important in the restaurant industry.     

Risk factors for methicillin-resistant Staphylococcus aureus carriage in residents of German nursing homes.

OBJECTIVES: To determine the prevalence of and the risk factors for methicillin-resistant Staphylococcus aureus (MRSA) carriage in nursing home residents in the Rhine-Neckar region of southern Germany. DESIGN: Point-prevalence survey. SETTING: Forty-seven nursing homes in the region. PARTICIPANTS: All residents of the approached nursing homes who agreed to participate. METHODS: After informed consent was obtained, all participants had their nares swabbed, some personal data collected, or both. All swabs were examined for growth of MRSA. All S. aureus isolates underwent oxacillin susceptibility testing and polymerase chain reaction for demonstration of the mecA gene. All MRSA isolates were typed using pulsed-field gel electrophoresis after digestion with SmaI. RESULTS: Swabs from 3,236 nursing home residents yielded 36 MRSA strains, contributing to a prevalence rate of 1.1%. Significant risk factors for MRSA carriage in the multivariate analysis were the presence of wounds or urinary catheters, limited mobility, admission to a hospital during the preceding 3 months, or stay in a medium-size nursing home. One predominant MRSA strain could be detected in 30 of the 36 MRSA carriers. CONCLUSIONS: The prevalence of MRSA in German nursing homes is still low. These residents seemed to acquire their MRSA in the hospital and transfer it to their nursing home. Apart from well-known risk factors for the acquisition of MRSA, we identified the size of the nursing home as an independent risk factor. This might be due to an increased use of and microbials in nursing homes of a certain size.     

Duration of methicillin-resistant Staphylococcus aureus carriage, according to risk factors for acquisition.

OBJECTIVE: To examine the duration of methicillin-resistant Staphylococcus aureus (MRSA) carriage and its determinants and the influence of eradication regimens. DESIGN: Retrospective cohort study. SETTING: A 1,033-bed tertiary care university hospital in Bern, Switzerland, in which the prevalence of methicillin resistance among S. aureus isolates is less than 5%. PATIENTS: A total of 116 patients with first-time MRSA detection identified at University Hospital Bern between January 1, 2000, and December 31, 2003, were followed up for a mean duration of 16.2 months. RESULTS: Sixty-eight patients (58.6%) cleared colonization, with a median time to clearance of 7.4 months. Independent determinants for shorter carriage duration were the absence of any modifiable risk factor (receipt of antibiotics, use of an indwelling device, or presence of a skin lesion) (hazard ratio [HR], 0.20 [95% confidence interval {CI}, 0.09-0.42]), absence of immunosuppressive therapy (HR, 0.49 [95% CI, 0.23-1.02]), and hemodialysis (HR, 0.08 [95% CI, 0.01-0.66]) at the time MRSA was first MRSA detected and the administration of decolonization regimen in the absence of a modifiable risk factor (HR, 2.22 [95% CI, 1.36-3.64]). Failure of decolonization treatment was associated with the presence of risk factors at the time of treatment (P=.01). Intermittent screenings that were negative for MRSA were frequent (26% of patients), occurred early after first detection of MRSA (median, 31.5 days), and were associated with a lower probability of clearing colonization (HR, 0.34 [95% CI, 0.17-0.67]) and an increased risk of MRSA infection during follow-up. CONCLUSIONS: Risk factors for MRSA acquisition should be carefully assessed in all MRSA carriers and should be included in infection control policies, such as the timing of decolonization treatment, the definition of MRSA clearance, and the decision of when to suspend isolation measures.     

Prevalence of and risk factors for methicillin-resistant Staphylococcus aureus carriage at hospital admission.

To determine the prevalence of and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) carriage at the time of admission to our hospital, we screened the medical records of 1,128 patients for demographic and clinical data. The antimicrobial resistance pattern and genotype of MRSA isolates were studied. The prevalence of MRSA carriage at hospital admission was 1.4%. Older patients and patients previously admitted to healthcare centers were the most likely to have MRSA carriage at admission.     

Long-term carriage, and transmission of methicillin-resistant Staphylococcus aureus after discharge from hospital.

The purpose of this study was to determine whether patients who become carriers of methicillin-resistant Staphylococcus aureus (MRSA) during their stay in hospital, remain colonized after discharge. Thirty-six patients colonized with MRSA during one of three outbreaks at Utrecht University Hospital (1986-89) were screened 2 or 3 years after they had become carriers. Patients were also interviewed to determine factors contributing to persistent carriage, such as antibiotics, re-admissions to the hospital, presence of skin lesions and chronic diseases. At the same time transmission of MRSA to family members was determined. The epidemic MRSA strain was still found in three patients (8%). One was a cystic fibrosis patient who had had frequent re-admissions to the hospital and had received several course of antibiotic treatment. Both of the other patients had skin lesions: a fistula and a colostomy respectively. None of the 44 family members of the patients was colonized or infected with MRSA. We conclude that long-term MRSA carriage occurs with low frequency and is comparable to persistent carriage of methicillin-sensitive Staphylococcus aureus (MSSA). Transmission of MRSA to healthy individuals in an antibiotic-free environment is a rare event.     

Community-acquired methicillin-resistant Staphylococcus aureus: an emerging pathogen.

The prevalence of MRSA in the nosocomial setting has been well studied, and its control remains a challenge for infection control professionals. Complicating this problem is the increasing number of reports on the spread of community-acquired MRSA (CA-MRSA). CA-MRSA strains differ from hospital-acquired MRSA (HA-MRSA) strains in that they are generally susceptible to most antibiotics. These strains share the presence of staphylococcal cassette chromosome mec (SCCmec) type IV in their genomes, are frequently virulent, and predominantly cause skin and soft tissue infections. The genome sequence of the prototypic CA-MRSA strain, MW2, revealed the presence of additional virulence factors not commonly present in other S. aureus strains. We determined the genetic relatedness of 30 geographically diverse CA-MRSA isolates clustered based on SCCmec type IV by sequence analysis of the polymorphic repeat region of the protein A gene (spa typing). These results indicated that most strains shared a common spa type (131), identical to MW2. Because this group tends to infect healthy individuals with no known risk factors for nosocomial acquisition of MRSA, we refer to it as CA-MRSA without risk factors. A second group, CA-MRSA with risk factors, consists of two related genotypes, spa types 1 and 7, which differ by one nucleotide change. These strains have caused severe infections in HIV-positive patients in Los Angeles and New York. Although CA-MRSA strains share genetic determinants, they are not clonal but rather are derived from different genetic backgrounds. The genetic characteristics and the epidemiology of CA-MRSA with and without risk factors are discussed.     

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.     

Clonal diversity of methicillin-resistant Staphylococcus aureus in an acute-care institution.

OBJECTIVE: To evaluate plasmid and chromosomal typing methods for differentiation of methicillin-resistant Staphylococcus aureus (MRSA). DESIGN: Comparison of relatedness of strains using epidemiologic features, phage typing, and antimicrobial susceptibility with blinded assessment by molecular typing methods. Molecular typing methods included AccI and ClaI restriction endonuclease fingerprinting of chromosomal DNA and plasmid typing. SETTING: Tertiary-care teaching hospital. METHODS: Convenience sample of 10 MRSA strains, including 4 outbreak-associated and 6 sporadic strains of diverse epidemiologic origins without evidence of nosocomial transmission. RESULTS: Only 2 strains were phage typeable. The epidemic strain was distinguishable by its susceptibility pattern. The other strains were not consistently separable by phenotyping or plasmid typing methods but were distinct by chromosome typing. CONCLUSIONS: These observations document the diversity of origins of MRSA strains introduced into an acute-care institution. Chromosomal typing may be the preferred method for the determination of clonal origin of MRSA.     

High risk for nasal carriage of methicillin-resistant Staphylococcus aureus among Danish veterinary practitioners

OBJECTIVES: Due to their multiple antibiotic resistance properties, methicillin-resistant Staphylococcus aureus (MRSA) are a major public health problem. After the recently described emergence of MRSA in animals, the authors investigated the risk of nasal MRSA carriage among people with professional contact with animals. METHODS: Nasal swabs and information on animal exposure and known MRSA risk factors were obtained from participants (N=702) at five conferences organized by national veterinary and farmer associations and students at a business school in Denmark. All of the participants were screened by standard microbiological techniques for MRSA detection and characterization. RESULTS: MRSA carriage was significantly (P<0.02) higher among the veterinary practitioners (3.9%) than among the participants not professionally exposed to animals (0.7%). Six of the nine MRSA strains isolated from veterinary practitioners belonged to clonal complexes (CC) previously associated with horses (CC8), small animals (CC22), and pigs (CC398). Although four of the nine positive veterinarians carried the CC associated with pigs, exposure to small animals, cattle, or horses, but not to pigs, was found to be a significant risk factor. CONCLUSIONS: The results indicate that veterinarians are at risk of MRSA carriage. Veterinary professionals should be informed about this emerging occupational health risk and educated about preventive measures. Collaboration between national medical and veterinary institutions is urgently needed to control the spread of these unwanted bacteria in the community.     

Decolonization of Staphylococcus aureus carriage

Staphylococcus aureus nasal colonization is a well-known independent risk factor for infection caused by this bacterium. Screening and decolonization of carriers have been proven effective in reducing S. aureus infections in some populations. However, a gap remains between what has been proven effective and what is currently done. We aimed to summarize recommendations and current knowledge of S. aureus decolonization to answer the following questions: Why? For whom? How? When? And what are the perspectives?