Appearance of methicillin-resistant Staphylococcus aureus (MRSA) sensitive to gentamicin in a hospital with a previous endemic distinct MRSA.

To evaluate the efficacy of adding either linezolid or daptomycin to Optisol-GS donor storage medium in reducing methicillin-resistant Staphylococcus aureus (MRSA) contamination of donor corneas. Optisol-GS was supplemented with either linezolid at 2×, 4×, or 10× minimum inhibitory concentration (MIC) or daptomycin and calcium at 5× or 50× MIC. Unsupplemented control groups were also used. Gentamicin-sensitive and gentamicin-resistant isolates of MRSA were added, and vials were refrigerated for 48 hours followed by sampling for viable colony counts immediately upon removal from refrigeration and after warming to room temperature for 3 hours. Safety studies of Optisol-GS supplemented with 50× MIC daptomycin and calcium were performed by evaluating the central corneal thickness and endothelial cell density of the donor cornea. Stability of daptomycin in Optisol-GS at storage was also tested. No added benefit was observed with linezolid supplementation to Optisol-GS against gentamicin-sensitive MRSA, with reduction in viable colony counts by >90% in all groups. No benefit was observed with linezolid supplementation against gentamicin-resistant MRSA, with the majority of inocula remaining viable in all groups. Viable counts of gentamicin-sensitive MRSA and gentamicin-resistant MRSA were effectively reduced with both 5× MIC and 50× MIC daptomycin supplementation. 50× MIC daptomycin-supplemented Optisol-GS had no appreciable effect on the central corneal thickness or endothelial cell density of the donor cornea and was stable at storage for 14 days. The addition of daptomycin to Optisol-GS significantly increases the anti-MRSA activity of the medium without any apparent negative effects on donor corneal tissue.

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) is acommon pathogen causing healthcare-associated infections. Owing to therestricted use of beta-lactams in MRSA infections, non-beta-lactamantimicrobials are required for treatment. However, MRSA can developresistance mechanisms to non-beta-lactam antimicrobials, which reducesviable treatment options. Here, we evaluated the antimicrobialsusceptibility and resistance genes of MRSA isolated from hospitalizedpatients in South Brazil. METHODS: The antimicrobial susceptibilities of hospital MRSA (217) isolates weredetermined by disk diffusion or microdilution methods. Additionally, thepresence of 14 resistance genes and SCCmec typing wasperformed by PCR. RESULTS: Among the antimicrobials tested, we observed high erythromycin (74.2%),ciprofloxacin (64.5%), and clindamycin (46.1%) resistance rates and completesusceptibility to linezolid and vancomycin. Seventeen different patterns ofMRSA antimicrobial resistance were observed, of which 42.9% representedmultidrug resistance. Among erythromycin-resistant MRSA, 53.4%, 45.3%,37.9%, 13.0%, and 6.8% carried ermA, msrA,msrB, ermC, and ermBgenes, respectively. Among clindamycin-resistant MRSA, 83%, 17%, 10%, 4%,and 2% carried ermA, ermC,ermB, linA, and linBgenes, respectively. Among gentamicin-resistant MRSA, 96.8%, 83.9%, and 9.7%carried aac(6')/aph(2''), aph(3’)-IIIa,and ant(4’)-Ia genes, respectively. Amongtetracycline-resistant MRSA, 6.5% and 93.5% carried tetKand tetM genes, respectively. Lastly, amongtrimethoprim/sulfamethoxazole-resistant MRSA, 13.3% and 100% carrieddfrA and dfrG genes, respectively. TheSCCmec type IV isolates were detected more frequently,whereas the SCCmec type III isolates exhibited highermultidrug resistance. CONCLUSIONS: The study data provides information regarding the MRSA resistance profile inSouth Brazil that is associated with the clinical conditions of patients andcan contribute to clinical decision-making.

Emergence of SCCmec type III with variable antimicrobial resistance profiles and spa types among methicillin-resistant Staphylococcus aureus isolated from healthcare- and community-acquired infections in the west of Iran

Oxacillin (methicillin) resistance in methicillin-resistant Staphylococcus aureus (MRSA) is associated with an increased incidence of resistance to other antibiotics, which has increased since it was first reported in 1969. In 1992 a new phenotype of MRSA arose in France; this was characterized by a heterogeneous expression of resistance to oxacillin and susceptibility to various antibiotics, including gentamicin but also tetracycline, minocycline, lincomycin, pristinamycin, co-trimoxazole, rifampin, and fusidic acid. In French hospitals a longitudinal nationwide surveillance of antibiotic resistance in S. aureus has allowed for the detection of changes in antibiotic susceptibility profiles. Seven French clinical laboratories (six from the mainland and one from the West Indies) reported the results of susceptibility testing of 57,347 S. aureus strains isolated in their institutes between 1992 and 1998. Over a 7-year period the incidence of isolation of gentamicin-susceptible MRSA (GS-MRSA) strains has steadily increased to represent, in 1998, 46.8 to 94.4% of the MRSA strains, irrespective of the overall incidence of MRSA. Two predominant types recognized by pulsed-field gel electrophoresis (PFGE) accounted for the majority of the GS-MRSA in different mainland hospitals, both differing from the predominant type observed in the French West Indies. Some GS-MRSA and gentamicin-resistant MRSA (GR-MRSA) strains had closely related PFGE profiles, and hybridization studies confirmed the lack in GS-MRSA of the aac6'-aph2" gene, which confers resistance to all aminoglycosides, with conservation of the ant4' gene, which confers resistance to kanamycin, tobramycin, and amikacin. Thus, it is likely that certain GS-MRSA strains could have emerged from GR-MRSA strains by excision or deletion of the aac6'-aph2" gene.

Joint Healthcare Infection Society (HIS) and Infection Prevention Society (IPS) guidelines for the prevention and control of meticillin-resistant Staphylococcus aureus (MRSA) in healthcare facilities

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) susceptible to gentamicin has been reported in a number of countries in the 1990s. To study the acquisition of gentamicin-sensitive MRSA (GS-MRSA) in southeast Queensland and the relatedness of GS-MRSA to other strains of MRSA, 35 cases of infection due to GS-MRSA from October 1997 through September 1998 were examined retrospectively to determine the mode of acquisition and risk factors for MRSA acquisition. Thirty-one isolates from the cases were examined using a variety of methods (antibiotyping, phage typing, pulsed-field gel electrophoresis [PFGE] fingerprinting, and coagulase typing by restriction analysis of PCR products) and were compared with strains of local hospital-acquired gentamicin-resistant MRSA (GR-MRSA) and of Western Australian MRSA (WA-MRSA). Only 6 of 23 cases of community-acquired GS-MRSA had risk factors for MRSA acquisition. Twenty of 21 isolates from cases of community-acquired infection were found to be related by PFGE and coagulase typing and had similar phage typing patterns. Hospital- and nursing home-acquired GS-MRSA strains were genetically and phenotypically diverse. Community-acquired GS-MRSA strains were not related to nosocomial GR-MRSA or WA-MRSA, but phage typing results suggest that they are related to GS-MRSA previously reported in New Zealand.

Multicenter Evaluation of the LightCycler MRSA Advanced Test, the Xpert MRSA Assay, and MRSASelect Directly Plated Culture with Simulated Workflow Comparison for the Detection of Methicillin-Resistant Staphylococcus aureus in Nasal Swabs

Epidemiological and molecular characteristics of meticillin-resistant Staphylococcus aureus in Turkey: A multicentre study.

New insights concerning methicillin-resistant Staphylococcus aureus disease

Changes in the epidemiology of methicillin-resistant Staphylococcus aureus in a Greek tertiary care hospital, over an 8-year-period

The problem of the spread of methicillin-resistant Staphylococcus aureus (MRSA) during hospital transfers, re-admission and admission from nursing homes is well documented. Since MRSA carriage can be occult, only to be detected later in clinical specimens, screening at hospital admission has been advocated for areas in which MRSA is endemic [1]. In a previous study Troillet et al. [2] found that without admission screening half of the MRSA carriers whose status was unknown at admission would have been missed or detected late. Compared with no screening, targeted screening has been shown to be effective in reducing the rates of MRSA acquisition in hospitals with a high level of endemic MRSA [3]. In Hong Kong, MRSA has been endemic since the mid-1980s [4]. Currently, screening for MRSA at admission is only practiced in a few selected units. The present report details the experience gained at an acutecare hospital in Hong Kong (Northern District Hospital) where screening for MRSA at admission is practiced routinely. The data was obtained by retrospectively reviewing the culture results in the hospital’s mainframe computer and the infection control records over a 3-year period (1 January 1999–31 December 2001). The 600bed hospital has all of the major specialty services, including an intensive care unit and a 24-h emergency department. The hospital’s screening policy called for cultures to be performed within 24 h for all patients with one or more of the following risk factors: a history of MRSA carriage, nursing home residence or any previous hospitalization (including inter-hospital transfer) during the preceding 6 months. Patients were grouped together and isolation precautions were implemented until the results of screening were available [1]. Screening cultures were also performed before the start of hospital duty for all new healthcare workers whose jobs involved close patient contact. During the study period, compliance with the MRSA screening policy was monitored regularly by ward visits and chart review, and it was estimated to exceed 90%. In order to obtain a background rate of MRSA carriage, 600 patients without the above risk factors for MRSA were prospectively screened at the emergency department for 3 months (August–November 2000) using the same protocol. An average of 10 patients per day was screened. To facilitate data retrieval and auditing, codes were entered into the laboratory records of all screened patients and healthcare workers. Initial and follow-up samples were coded separately. Individual risk factors were not coded separately until 1 June 2001. Hence, a breakdown of the MRSA isolation rate according to individual risk factors was available only for the period 1 June–31 December 2001. As part of the infection control policy, all patients and staff members who tested positive for MRSA during screening were treated topically for 5 days with a daily wash or bath using 4% chlorhexidine gluconate (Hibiscrub; Zeneca Pharma, France) and the twice-daily application of 2% mupirocin (Bactroban nasal; GlaxoSmithKline, Hong Kong) to both nares. Follow-up MRSA cultures were performed weekly for 3 weeks following T. L. Que · K. T. Yip · H. L. Ng New Territory North Pathology Service, Northern District Hospital, Hong Kong SAR, People’s Republic of China

Staphylococcus aureus has long been recognised as an important pathogen. Originally sensitive to penicillins, including methicillin, the introduction of penicillin into clinical practice led to resistance and methicillin resistant S. aureus (MRSA) was first described in 1961. Not only is S. aureus a pathogen, but it commonly colonises skin and mucous membranes. The anterior nares are the most consistent area from which the organism can be isolated. Carriage rates of methicillin sensitive S. aureus (MSSA) vary between 25% and 33% and there is no significant difference between the general population and healthcare workers in this respect. Carriage of MRSA, however, is more common in healthcare workers than in the general population and general practitioners are just as likely as hospital workers to be carriers. Persistent carriage of MRSA occurs in 4.6% of healthcare workers [1]. With regard to carriage of S. aureus, four patterns occur. Some individuals always carry the organism (persistent carriers), some carry the organism intermittently (intermittent carriers) and some never carry the organism (non-carriers) [2]. Transient carriage is recognised in persons who carry the organism for a short period after contact with another person who is either infected or is carrying S. aureus. Transient carriage is common; up to 50% of nurses will have positive nasal swabs at the end of a shift when they have been caring for a patient with MRSA but most will be negative when swabbed at the beginning of the next shift [3]. S. aureus infection is common in hospital and S. aureus carriage is a risk factor for development of infection. In the surgical population there is a fourfold increased risk of S. aureus bacteraemia in carriers compared to non-carriers [4], and at least 80% of S. aureus infections are caused by S. aureus cells that were present on the skin or mucous membranes before hospital admission (endogenous infection) [5]. This leaves approximately 20% where the S. aureus has been acquired from elsewhere (exogenous infection) and the possibility of transfer from a healthcare worker in this group is very real. Carriage of MRSA is more likely than that of MSSA to lead to clinical infection, including wound, lower respiratory tract and catheter-related blood stream infections [6], and the risk of death is greater with MRSA bacteraemia compared with MSSA bacteraemia [7]. These are two of the reasons that there is a current focus on MRSA rather than MSSA. There are two main ways by which anaesthetists can increase the risk of MRSA bacteraemia in their patients – poor aseptic technique and poor hand hygiene – but there are a number of other factors that impact upon the transmission of MRSA, with which anaesthetists may be less familiar. Although hand hygiene is the public face of prevention [8, 9], the wide range of procedures and processes that have been identified as important means that MRSA blood stream infection has become a quality marker used by the UK Department of Health to set targets, rank hospitals and permit application for Foundation status. Mandatory reporting of MRSA blood stream infection to the Health Protection Agency began in 2001 and most hospitals now undertake a root cause analysis following every MRSA bacteraemia. Although post-operative MRSA bacteraemia only accounts for 50% of all cases, many of the surgical patients who develop MRSA bacteraemia have undergone major surgery and as such have had a number of intravascular catheters placed in the peri-operative period. Poor technique, imperfect compliance with guidelines or inadequate documentation of the line placement procedure is often quoted in a root cause analysis as a possible cause of infection. Regardless of the complexity of the operation, the anaesthetist is identified as a person possibly responsible for the MRSA infection. So what are the factors that can impact on the transmission and therefore the chance of MRSA bacteraemia occurring? A number of factors have been identified as important [10] and most of these are relevant to anaesthetists. Healthcare workers, besides being clean and competent, should be present in sufficient numbers to enable infection control procedures to be completed correctly. This last point is particularly relevant to anaesthetists. It is not possible to administer intravenous drugs with one hand and maintain the airway with the other whilst following correct infection control procedures. The correct process would be for two separate people to carry out the two separate procedures, a luxury that few of us experience. Care delivery procedures can be influenced both by the actions that we take and the decisions that we make. Hand hygiene and the use of personal protective equipment should be routine [11] and aseptic technique should be used correctly whenever appropriate. How many anaesthetists have been taught to scrub properly or to don gloves using a no-touch technique? This is not yet considered a core competency by the Royal College of Anaesthetists. Decisions that we make that impact upon the transmission of MRSA include avoiding the use of invasive devices and removing all devices as soon as possible. Equipment that is used must be able to be decontaminated between patients if it is not disposable. The line between disposable and non-disposable equipment is sometimes vague. It is obvious that the transoesophageal echocardiography machine used in theatre is not disposable but less obvious is an accepted method of decontamination between patients. A number of the ‘disposable’ items that we use are disposed of whilst trying to balance cost and risk. The disposable bag on the anaesthetic machine is used by the same hand that maintains the airway of the unconscious patient and yet it is frequently changed only at the end of the day or week. Effective decontamination of this type of item is extremely difficult. Administrative processes have been developed over the last few years that are designed to have an impact on the transmission of MRSA. These include antibiotic stewardship, surveillance and screening of patients and staff. Surveillance is now undertaken routinely as part of all hospitals’ infection control programmes, with hospitals obliged to publish the number of MRSA bacteraemias that occur every month. Although some anaesthetists fit nicely into groups that can take an active part in reviewing surveillance data and therefore work to reduce the incidence of MRSA (neuro-anaesthetists may review the data from neurosurgical and neuro-intensive care patients etc), many anaesthetists do not fit neatly into these groups and view the surveillance data with little more than passing interest. Screening patients for MRSA is not a control measure in itself but the efficacy of screening depends upon the other interventions that occur following the result. This will include decolonisation or isolation. Recommendations for screening have changed over the last 15 years from not being recommended, to being recommended for high risk surgery, to being recommended for virtually all patients [12], and screening before admission to hospital (or on admission when admitted as an emergency) has been mandatory for all patients in the UK since April 2009 [13]. How this intervention impacts upon the prevalence of MRSA bacteraemia remains to be seen, but there is already evidence that screening higher risk patients significantly reduces prevalence. The approach to positive MRSA carriage in patients will vary according to the urgency of admission and local policy, but elective patients now receive decolonisation treatment if found to be positive when screened. The controversy surrounding routine screening of patients has now disappeared and it has been replaced by a controversy about the screening of healthcare workers. Although the 2006 guidelines for MRSA in healthcare facilities did not recommend routinely screening staff, the times they are a-changing and the public is beginning to demand this. Sir Richard Branson is now Vice-President of the Patient’s Association and he has stated that he wants to see the immediate implementation of routine screening for MRSA in healthcare workers. So why should it be done, how should it be done, how should MRSA carriage be treated in healthcare workers and what are the implications for the 4.6% of us who are carriers of MRSA? There is a clear association between carriage of MRSA by healthcare workers and MRSA infection in patients, but it is unclear whether the healthcare worker is the ‘source, vector or victim’ of the problem [1]. The 2006 guidelines recommended that investigation or screening of staff should be restricted to those associated with an outbreak of MRSA, possibly starting with staff who had skin lesions eg eczema, but the argument for more general screening is supported by the correlation between colonisation rate and the prevalence of endemic MRSA. The likely source of MRSA will change markedly from now on with the introduction of universal screening for patients, changing the odds that a single case of MRSA bacteraemia originates from a healthcare worker. When screening (of staff) is done, it should be performed at the beginning of the day away from the clinical environment. This will prevent inappropriate identification of transient carriers with unnecessary treatment and exclusion from work. Swabs should be moistened with sterile saline before swabbing to enhance the likelihood of detection. Although there is no agreement on the sites to be swabbed, this should certainly include the anterior nares and usually includes the groin or axilla. Treatment of a MRSA positive healthcare worker should be multi-faceted. Exclusion from the clinical workplace for 48 h following the positive finding and initiation of treatment are recommended. Return to clinical work should be determined by a risk analysis. Clearly anaesthetists fall into a high-risk group and return to practice is generally delayed until negative swabs have been obtained 48 h after treatment has been completed. Treatment generally lasts 5 days and includes showering and hair washing with chlorhexidine liquid and mupiricin ointment applied to the anterior nares. Although the goal of treatment in the patient population is decolonisation, in healthcare workers, the aim is eradication. Eradication is continued decolonisation, with a negative screen at either 6 or 12 months. The difference between the two is due to treatment failure or recurrence. Treatment failure occurs in 9% of healthcare workers, some of which may be due to treatment compliance, but recurrence in healthcare workers who were initially decolonised has been estimated to occur in approximately 25% by 1 month [14]. So what are the implications for anaesthetists? It is not yet clear that testing for all or all relevant healthcare workers will be introduced, but there are a number of advantages if it is. It will probably reduce the prevalence in patients where MRSA is endemic and decrease the incidence where MRSA is sporadic. It will reduce the chance of MRSA infection in healthcare workers and will undoubtedly improve patient and public confidence. It would add to the existing training methods in infection control by a process of ‘vivid experience’ [15]. Balancing the advantages, there are a number of disadvantages or other considerations. First, careful consideration needs to be made of the ethics of mass screening [16] and whether the imperative that benefit should outweigh likely harm has been met. The complexities of individual vs population benefit must also be considered. Screening staff would provide false reassurance for non-colonised or non-identified healthcare workers, it would disrupt patient care and it would threaten staff morale. The feelings of guilt of MRSA positive healthcare workers towards patients and close contacts would need to be addressed. The issues of stigmatisation, anonymity, failure of decolonisation and reporting of long-term carriers under the ‘Reporting of Injuries, Diseases and Dangerous Occurrences Regulations’ (RIDDOR, 1995) as a mechanism of providing legal protection all need consideration. Although public pressure can be very powerful it is important to have a logical approach to screening staff before its introduction.

Evaluating the Probability of Previously Unknown Carriage of MRSA at Hospital Admission

Objective To isolate and identify the methicillin-resistant Staphylococcus aureus (MRSA) strains carrying Panton-Valentine leukocidin genes (pvl+ -MRSA) from clinical samples and to further understand their molecular characteristics and infections caused by them. Methods Drug susceptibility test was performed to detect the drug resistance in 259 MRSA strains. pvl+ -MRSA strains were screened out from those MRSA strains using cefoxitin slip test and mecA gene detection by PCR. Multiple PCR and multilocus sequence typing (MLST) were used for SCCmec and ST typing. Pulsed-field gel electrophoresis (PFGE) and cluster analysis were used to understand the genetic and epidemic features of the pvl+ -MRSA strains. Different types of infections and diseases caused by the pvl+ -MRSA strains were analyzed. Results Among the 259 MRSA strains, 51 pvl+ -MRSA strains were identified (19.7%, 51/259), of which 29 and 22 strains were respectively isolated from patients with community-acquired and hospital-acquired infections. ST59-SCCmecⅢ (35.3%, 18/51) was the predominant type of the 51 pvl+ -MRSA strains, followed by ST59-SCCmecⅣ(25.5%, 13/51). But no predominant clone among those strains was revealed by the result of PFGE. Children, young- and middle-aged patients (≤44 years old) had a significantly higher positive rate of pvl+ -MRSA than patients aged ≥45 years (P<0.05). Skin and soft tissue infection (47.1%, 24/51) was the most common disease caused by the pvl+ -MRSA strains (P<0.05), followed by pneumonia (17.6%, 9/51). The pvl+ -MRSA strains showed lower resistance to levofloxacin, gentamycin and rifampicine (7.8%-21.6%). No moxifloxacin-, nitrofurantoin- or linezolid-resistant pvl+ -MRSA strains were identified. Conclusion The rate of pvl+ -MRSA infection is high in the local population. ST59-SCCmecⅢ and ST59-SCCmecⅣ are the predominant types of pvl+ MRSA strains. Children, young- and middle-aged persons are the susceptible population. Skin and soft tissue infection and pneumonia are the common diseases caused by pvl+ -MRSA. Key words: Methicillin-resistant Staphylococcus aureus; Infection; Panton-Valentine leucocidin; Molecular typing; Disease type

To determine whether any of several quality improvement interventions with none specifically targeting methicillin-resistant Staphylococcus aureus (MRSA) were associated with a decline in endemic MRSA prevalence in an intensive care unit (ICU) where active screening and contact isolation precautions for known MRSA colonised patients are not practised. Medical-surgical ICU with 2,000 admissions/year. 8.5-year retrospective time-series analysis. ICU re-location, antibiotic stewardship utilising computerised decision-support and infectious-diseases physician rounds, dedicated ICU infection control practitioners, alcohol-based hand rub solution (ABHRS). Regression modelling was used to evaluate trends in S. aureus prevalence density (monthly clinical isolates per 1,000 patient-days), antibiotic consumption, infection control consumables, ABHRS and their temporal relationship with MRSA prevalence. Methicillin-resistant S. aureus prevalence density decreased by 83% [95% confidence interval (CI) -68% to -91%, p < 0.001]. Rates of MRSA bacteraemia decreased 89% (95% CI -79% to -94%, p = 0.001) with no statistically significant change in methicillin-sensitive S. aureus bacteraemia. Hospital MRSA prevalence density decreased 17% (95% CI -5% to -27%, p = 0.005), suggesting that ICU was not shifting MRSA elsewhere. In ICU, broad-spectrum antibiotic use decreased by 26% (95% CI -12% to -38%, p = 0.008), coinciding with a decrease in MRSA, but time-series analysis did not show a significant association. On multivariate analysis, only ABHRS was significantly associated with a decrease in MRSA, but it was formally introduced late in the study period when MRSA was already in decline. General quality improvement measures were associated with a decrease in endemic MRSA in a high-risk setting without use of resource-intensive active surveillance and isolation practices.