Triclosan resistance in methicillin-resistant Staphylococcus aureus (MRSA)

Two triclosan selected mutants showed four-fold and 16-fold increases in their minimum inhibitory concentrations (MICs) of triclosan (1 mg/L and 4 mg/L) compared with their parent strains. Four clinical isolates of MRSA were detected with the same triclosan susceptibility as the mutants. One mutant had a predicted change in the gene product on FabI (Thr 147-->His), whilst only one clinical isolate had predicted FabI amino-acid changes (Ala 198-->Gly, and Leu 208-->Phe). The lack of fabI mutations in one mutant and three of the clinical isolates showing reduced triclosan susceptibility suggest that genetic loci other than fabI may be involved in triclosan resistance.     

Interaction between methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA)

In this paper we describe the in vitro interaction between three strains of methicillin-sensitive Staphylococcus aureus (MSSA) [NCTC 11561 and two strains derived from patients (PMSSA)] and endemic methicillin-resistant Staphylococcus aureus (EMRSA) 1, 3, 15 and 16. Mixed bacterial cultures of MSSA and EMRSA were incubated and subcultured after one, two and seven days. A proportion of MRSA in 50 randomly selected colonies was assessed. All strains of EMRSA (EMRSA 1, 3, 15 and 16) outgrew and virtually eradicated MSSA (NCTC 11561) after 24 h. The interaction between strains of PMSSA and the various strains of EMRSA was variable. PMSSA strain 1 was almost completely outgrown by EMRSA 1 and EMRSA 3 after seven days. Similarly there was a substantial increase of EMRSA 1 and 3 when tested against PMSSA strain 2. EMRSA 15 increased modestly against both strains, but EMRSA 16 failed to increase in proportion against either of the strains. We conclude that there is a complex interaction between various strains of EMRSA and MSSA. This interaction may have an important bearing on colonization of patients with MRSA.     

Clindamycin is unsuitable for the empirical treatment of infections due to pig-related methicillin-resistant Staphylococcus aureus (MRSA)

OBJECTIVE: To determine the antibiotic sensitivity of methicillin-resistant Staphylococcus aureus (MRSA) isolated from persons in contact with pigs. DESIGN: Retrospective. METHOD: The pig-related MRSA collection, built up between January 1st 2003 and November 30th 2006 in the Regional Laboratory for Medical Microbiology and Infection Prevention (RLMMI) of the Jeroen Bosch Hospital, Den Bosch, The Netherlands, was tested for sensitivity to a large number ofantibiotics. RESULTS: A total of 65 isolates were obtained from 53 patients. All (100%) of the pig-related MRSA isolates were sensitive to vancomycin, teicoplanin, nitrofurantoin, rifampicin, linezolid, and quinupristin-dalfopristin. Variable sensitivity was found for erythromycin (40%), clindamycin (48%), cotrimoxazole (48%), aminoglycosides (92%), tetracycline (6%), and quinolones (94%). CONCLUSION: In view of the sensitivities found, clindamycin does not seem suitable for the empirical therapy ofpig-related MRSA-infections. In case of severe infection, therapy should be started either with an intravenous glycopeptide or with oral ciprofloxacin, possibly combined with rifampicin or linezolid.     

Prevalence of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) on retail meat in Iowa

Several recent studies have indicated a high prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in retail-available meat. However, few studies have investigated MRSA in meat in the United States. The aim of this study was to determine the presence of Staphylococcus aureus (S. aureus) on meat samples available at retail stores. Samples of fresh raw pork, chicken, beef, and turkey were purchased from 22 food stores throughout Iowa. S. aureus strains were isolated from 27 of 165 samples, giving an overall prevalence of 16.4%. Turkey, pork, chicken, and beef had individual S. aureus prevalence rates of 19.4%, 18.2%, 17.8%, and 6.9%, respectively. Two isolates of MRSA were isolated from pork, giving an overall prevalence of 1.2%. One MRSA isolate was positive for the PVL gene. Common spa types included t034, t337, t008, and t002. These results suggest that MRSA is present on low numbers of retail meat in Iowa.     

Active surveillance for methicillin-resistant Staphylococcus aureus (MRSA) decreases the incidence of MRSA bacteremia.

OBJECTIVES: To evaluate the influence of performance of active surveillance cultures for methicillin-resistant Staphylococcus aureus (MRSA) on the incidence of nosocomial MRSA bacteremia in an endemic hospital. DESIGN: Before-after trial. SETTING: A 700-bed hospital. PATIENTS: All patients admitted to the hospital who were at high risk for MRSA bacteremia. INTERVENTION: Performance of surveillance cultures for detection of MRSA were recommended for all patients at high risk, and contact isolation was implemented for patients with positive results of culture. Each MRSA-positive patient received one course of eradication treatment. We compared the total number of surveillance cultures, the percentage of surveillance cultures with positive results, and the number of MRSA bacteremia cases before the intervention (from January 2002 through February 2003) after the start of the intervention (from July 2003 through October 2004). RESULTS: The number of surveillance cultures performed increased from a mean of 272.57 cultures/month before the intervention to 865.83 cultures/month after the intervention. The percentage of surveillance cultures with positive results increased from 3.13% before to 5.22% after the intervention (P < .001). The mean number of MRSA bacteremia cases per month decreased from 3.6 cases before the intervention to 1.8 cases after the intervention (P < 0.001). CONCLUSIONS: Active surveillance culture is important for identifying hidden reservoirs of MRSA. Contact isolation can prevent new colonization and infection and lead to a significant reduction of morbidity and healthcare costs.     

The value of nasal mupirocin in containing an outbreak of methicillin-resistant Staphylococcus aureus in an orthopaedic unit

An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) occurred in two adjacent orthopaedic wards following the admission of a known carrier. The outbreak was not contained by ward closure or by standard infection control measures. Eventually several nasal carriers were identified and treated with nasal mupirocin, following which the outbreak ended.     

Screening strategies in surveillance and control of methicillin-resistant Staphylococcus aureus (MRSA)

With reports of hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) continuing to increase and therapeutic options decrease, infection control methods are of increasing importance. Here we investigate the relationship between surveillance and infection control. Surveillance plays two roles with respect to control: it allows detection of infected/colonized individuals necessary for their removal from the general population, and it allows quantification of control success. We develop a stochastic model of MRSA transmission dynamics exploring the effects of two screening strategies in an epidemic setting: random and on admission. We consider both hospital and community populations and include control and surveillance in a single framework. Random screening was more efficient at hospital surveillance and allowed nosocomial control, which also prevented epidemic behaviour in the community. Therefore, random screening was the more effective control strategy for both the hospital and community populations in this setting. Surveillance strategies have significant impact on both ascertainment of infection prevalence and its control.     

Methicillin-Resistant Staphylococcus aureus (MRSA)

Occupational and environmental health nurses can prevent the spread of MRSA when evaluating and treating workers' injuries.     

Comparative cost of selective screening to prevent transmission of methicillin-resistant Staphylococcus aureus (MRSA), compared with the attributable costs of MRSA infection.

The annual cost of a screening program to detect methicillin-resistant Staphylococcus aureus (MRSA) in a teaching hospital in Spain was 10,261 Euro. The average cost per MRSA infection was 2,730 Euro; therefore, the cost of the program would be covered if it only prevented 4 infections per year (11% of the total number of MRSA infections at our hospital).     

Effects on nursing workload of different methicillin-resistant Staphylococcus aureus (MRSA) control strategies

Nursing staff workload may influence hospital-acquired staphylococcal transmission. Closure of wards to new admissions is used in some institutions as part of methicillin-resistant Staphylococcus aureus (MRSA) outbreak control, and we postulated that it worked by reducing staff workload, allowing more time for good infection control practices. We have used the GRASPCopyright workload system to compare nursing workload during six MRSA outbreaks. Two outbreaks occurred while an aggressive control policy ('old'; 1994-1995) was in place, with a low threshold for ward closure. Control measures had been relaxed before the later four outbreaks, with wards remaining fully or partially open unless MRSA transmission proved intractable ('new'; 1995-1996). To standardize the analysis we compared GRASP and epidemiological data for periods while MRSA transmission was occurring on each ward ('during'), and four week periods 'before' and 'after'. Closing wards to admissions reduces staff workload towards a quality environment, although the nursing requirements of remaining patient rises. Workload pressures may rise during outbreaks if wards are not closed quickly and fully, and patients are not transferred to specialist isolation facilities. Changes in nursing workload need to be assessed during comparative studies of outbreak control measures and the GRASP(c) system appears to be a sensitive way to measure these.     

Control of a methicillin-resistant Staphylococcus aureus (MRSA) outbreak in a day-care institution

This article describes an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) in two institutions for multi-handicapped children in Copenhagen. The aim of the study was to determine whether it was possible to eradicate MRSA in a setting with multi-handicapped children and staff where there was a high degree of physical interaction. This was a prospective interventional uncontrolled cohort study that took place from January 2003 to March 2005. All individuals in close contact with the two institutions and/or in close contact with an MRSA-colonized subject from the outbreak were included in the study: 38 children, 60 staff members and 12 close relatives of colonized subjects. Infection control measures included screening all individuals. When MRSA infection or colonization was found, an attempt was made to eradicate MRSA, staff education was undertaken and attempts were made to determine the route of transmission. Eleven individuals were found to be positive for MRSA (10.0%). All isolates were identical by pulsed-field gel electrophoresis and harboured the staphylococcal cassette chromosome mec (SCCmec) type IV. All colonized and infected individuals were associated with a single room in one of the institutions. MRSA was eradicated from all the colonized and infected subjects. This study shows that it is possible to control an MRSA outbreak in institutions for multi-handicapped children where there is a high degree of physical contact.     

Prevention of percutaneous endoscopic gastrostomy site infections caused by methicillin-resistant Staphylococcus aureus

Percutaneous endoscopic gastrostomy (PEG) is widely used to maintain enteral nutrition in patients who are unable to swallow. Peristomal wound infection is the most common complication of this procedure. In a hospital endemic for methicillin-resistant Staphylococcus aureus (MRSA), MRSA can be the most common organism associated with these infections. We have evaluated a strategy consisting of screening, skin decontamination and glycopeptide prophylaxis for preventing PEG-site infections. None of the 34 patients who received the decontamination protocol and glycopeptide prophylaxis (Group A) developed PEG-site infections within one month of surveillance. Two patients were infected with MRSA after that period. One of seven patients who received the decontamination protocol alone (Group B) was infected within the period of surveillance, while another patient was infected after that period. Both were infected with MRSA. None of nine patients who received glycopeptide prophylaxis alone (Group C) were infected. The results suggest that the strategy of screening, decontamination and glycopeptide prophylaxis is effective in the prevention of PEG-site infections with MRSA. Further trials are necessary to confirm these findings.     

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%.     

Spread of methicillin-resistant Staphylococcus aureus (MRSA) among household contacts of individuals with nosocomially acquired MRSA.

OBJECTIVE: To determine the frequency with which methicillin-resistant Staphylococcus aureus (MRSA) is spread from colonized or infected patients to their household and community contacts. DESIGN: Retrospective cohort study. SETTING: University hospital. PARTICIPANTS: Household and community contacts of MRSA-colonized or -infected patients for whom MRSA screening cultures were performed. RESULTS: MRSA was isolated from 25 (14.5%) of 172 individuals. Among the contacts of index patients who had at least one MRSA-colonized contact, those with close contact to the index patient were 7.5 times more likely to be colonized (53% vs 7%; 95% confidence interval, 1.1 to 50.3; P = .002). An analysis of antimicrobial susceptibility and DNA fingerprint patterns suggested person-to-person spread. CONCLUSIONS: MRSA colonization occurs frequently among household and community contacts of patients with nosocomially acquired MRSA, suggesting that transmission of nosocomially acquired MRSA outside of the healthcare setting may be a substantial source of MRSA colonization and infection in the community.     

Possible risk for re-colonization with methicillin-resistant Staphylococcus aureus (MRSA) by faecal transmission

An increase in the frequency of methicillin-resistant Staphylococcus aureus (MRSA) as an important causative agent of nosocomial infections is observed worldwide. Unfortunately, in spite of optimal hygienic conditions (barrier isolation, screening, decontamination), patients often remain MRSA positive or are detected as "re-colonized" at readmission. The objective of our study was to clarify if this is due to an undetected colonization of the gastrointestinal tract, which could possibly lead to re-colonization after primary successful decontamination. Therefore, all MRSA strains were collected from 290 in-patients of a university hospital over a period of 2 years. A surprisingly high number (24.1% of all) was isolated from stool samples. Even 13.1% of the total collection could be first observed in this material before detecting MRSA in other materials of these patients. To evaluate the epidemiology of these isolates, pulsed-field gel electrophoresis (PFGE) was used. On the basis of PFGE restriction types one main clone and 11 singular clones could be identified. Additionally, for six individual patients MRSA isolates from stool specimens were indistinguishable from other isolates from different locations. We show here that colonization of the gastrointestinal tract with MRSA apparently could play an important role in spreading MRSA via faecal contamination. Hence, we suggest that stool colonization with MRSA could be the source of a so far unrecognized transmission of MRSA within individual patients and within the population. Therefore, our findings imply a modification in the hygienic strategies for handling decontamination and therapy of MRSA patients.