Modelling the transmission dynamics of meticillin-resistant Staphylococcus aureus in Beijing Tongren hospital

Semi-professional volunteers work in many tertiary care hospitals in China as healthcare assistants. Proper infection control measures are needed to reduce nosocomial transmission involving volunteers. A compartmental model was constructed to describe the transmission characteristics of meticillin-resistant Staphylococcus aureus (MRSA) in the emergency ward (EW) and respiratory intensive care unit (RICU) for volunteers in Beijing Tongren Hospital, Beijing, China. The model consists of components describing uncolonized and colonized patients, uncontaminated and contaminated healthcare workers (HCWs), and uncontaminated and contaminated volunteers. The basic reproduction number (R(0)) was calculated, and the dependence of R(0) on various model parameters was analysed. Moreover, simulations of the model were performed for comparision with the reported data on the numbers of colonized patients in the EW and RICU from 3 March 2009 to 28 February 2010, respectively. Sensitivity analysis of R(0) showed that increasing handwashing compliance among HCWs and volunteers would reduce the risk of transmission dramatically. As volunteers care for patients on a one-to-one basis, this study showed that the number of MRSA-positive patients would increase if volunteers were replaced by HCWs. Therefore, in addition to improving hand hygiene among HCWs, the employment of properly trained volunteers is an attractive alternative to decrease MRSA and other multi-drug resistant bacteria infections in the hospital setting.     

Unexpected absence of meticillin-resistant Staphylococcus aureus nasal carriage by healthcare workers in a tertiary hospital in Kenya

Healthcare workers (HCWs) are a major reservoir of meticillin-resistant Staphylococcus aureus (MRSA). A cross-sectional study was conducted between July and December 2010 to determine the prevalence of nasal carriage of MRSA at the Aga Khan University Hospital Nairobi. Nasal swabs were taken from 246 randomly selected HCWs. MRSA was identified using both phenotypic and genotypic methods. The prevalence of MRSA carriage was 0% [95% confidence interval (CI): 0-1.5%] whereas that of meticillin-susceptible Staphylococcus aureus was 18.3% (95% CI: 14.0-23.6%). Given the absence of MRSA in our hospital, screening HCWs should be limited to an outbreak setting.     

Evaluation of different methods to recover meticillin-resistant Staphylococcus aureus from hospital environmental surfaces

The environment is implicated as a source of healthcare-associated infections (HAIs) and there is a need for evidence-based approaches to environmental sampling to assess cleanliness and improve infection prevention and control. We assessed, in vitro, different approaches to sampling the environment for meticillin-resistant Staphylococcus aureus (MRSA). In a laboratory-based investigation, the recovery of MRSA from two common hospital environments using six different sampling methods was evaluated, with a wild-type strain of MRSA. A 100 cm² section of mattress and a laboratory bench surface were contaminated with known inocula of MRSA. Bacteria were recovered by sampling at 30 min after inoculation, using either saline-moistened cotton swabs, neutralising buffer swabs, eSwabs or macrofoam swabs, which were all enriched in tryptone soya broth, or by sampling with direct contact plates or chromogenic ‘sweep’ plates. The sensitivity (i.e. the minimum number of bacteria inoculated on to a surface which subsequently produced a positive result) of each method was determined for each surface. The most sensitive methods were eSwabs and macrofoam swabs, requiring 6.1 × 10⁻¹ and 3.9 × 10⁻¹ MRSA/cm², respectively, to produce a positive result from the bench surface. The least sensitive swabbing method was saline-moistened cotton swabs, requiring 1.1 × 10³ MRSA/cm² of mattress. The recovery of bacteria from environmental samples varies with the swabs and methodology used and negative culture results do not exclude a pathogen-free environment. Greater standardisation is required to facilitate the assessment of cleanliness of healthcare environments.     

Cost of the meticillin-resistant Staphylococcus aureus search and destroy policy in a Dutch university hospital

Costs related to a search and destroy policy and treatment for Staphylococcus aureus bacteraemia in the University Hospital Maastricht were calculated for the period 2000 and 2004. The financial cost-benefit break-even point of the search and destroy policy was determined by modelling. On average 22,412 patients were admitted per year for an average of 8.7 days. Each year 246 patients were screened for meticillin-resistant Staphylococcus aureus (MRSA) and 74 patients were decolonised and nursed in preventive isolation. The prevalence of MRSA in the University Hospital Maastricht was 0.7%, as calculated from positive blood cultures, and mean length of stay for all patients with S. aureus bloodstream infections was 39.9 days. The annual cost of pro-active searching for MRSA in the University Hospital Maastricht was euro 1,383,200, and euro 2,736,762 for MRSA prevention and treatment of S. aureus bloodstream infections. Simulation of a variety MRSA/meticillin-susceptible S. aureus (MSSA) ratios showed that even if the MRSA prevalence reaches 8%, prevention costs are still lower than the cost of treating S. aureus infections. In conclusion, the total cost of a search and destroy policy is lower than the cost of treating S. aureus bloodstream infections in the University Hospital Maastricht. At an MRSA prevalence of 相似文献   

Burden of meticillin-resistant Staphylococcus aureus colonization and infection in London acute hospitals: retrospective on a voluntary surveillance programme

Although meticillin-resistant Staphylococcus aureus (MRSA) is recognized as an important cause of hospital and community healthcare-associated morbidity, and colonization as a precursor to infection, few studies have attempted to assess the burden of both colonization and infection across acute healthcare providers within a defined health economy. This study describes the prevalence and incidence of MRSA colonization and infection in acute London hospital Trusts participating in a voluntary surveillance programme in 2000-2001. Hospital infection control staff completed a weekly return including details on incident and prevalent colonizations, bacteraemias and other significant infections due to MRSA. Incidence and prevalence rates were calculated for hospitals with sufficient participation across both years. Colonizations accounted for 79% of incident MRSA cases reported; 4% were bacteraemias, and 17% other significant infections. There was no change in incidence of colonization of hospital patients between 2000 and 2001. By contrast, there was an unexplained 49% increase in prevalence of colonizations over this period. For any given month, prevalent colonizations outnumbered incident colonizations at least twofold. This MRSA surveillance programme was unusual for prospective ascertainment of incident and prevalent cases of both colonization and infection within an English regional health economy. Consistent with other studies, the incidence and prevalence of colonization substantially exceeded infection. Given the small contribution of bacteraemias to the overall MRSA burden, and the surveillance, screening and control interventions of recent years, it may be appropriate to review the present reliance on bacteraemia surveillance.     

Experience applying the UK meticillin-resistant Staphylococcus aureus (MRSA) guidelines in a tertiary referral hospital in the United Arab Emirates 1999-2002: same guidelines, different cultures

Meticillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial pathogen worldwide. There are few reports concerning MRSA in the United Arab Emirates (UAE). We report our experience with MRSA in a 400-bed tertiary referral hospital in the UAE, which followed the UK MRSA guidelines. MRSA data were reviewed to include demographic and clinical data on all new MRSA cases; a review of the ward environment including number of single rooms, sinks, toilets and bathrooms, frequency of cleaning; cultural observations; and number of infection control personnel per beds. MRSA was an uncommon pathogen. There were 90 new MRSA cases from 1999 to 2002 including two clusters of MRSA. While the procedures followed were the same as those in the UK, there were differences in the hospital environment compared with the UK and in cultural aspects of the patients' behaviour. At least 70% of inpatients were in single rooms with ensuite bathrooms. It was rare for more than two patients to share a toilet or bathroom. There were fewer than recommended infection control personnel and no antibiotic restriction policy in the hospital. Cleaners were on the wards for >100 h per week and were available 24 h per day for rapid response. We conclude that there are many factors that influence the management and control of MRSA, including cultural and social behaviour.     

Effect of reduction in ciprofloxacin use on prevalence of meticillin-resistant Staphylococcus aureus rates within individual units of a tertiary care hospital

Previous studies have shown a correlation between fluoroquinolone use in hospitals and rates of meticillin-resistant Staphylococcus aureus (MRSA) infection. This study examined the effect on MRSA infection rates within individual adult units of a tertiary care teaching hospital after instituting a programme to decrease ciprofloxacin use. Clinical specimens positive for S. aureus were determined on all adult inpatient units between 1 January 2004 and 31 December 2005. Units with >10 isolates of S. aureus per year were included in the analysis. Ciprofloxacin use, measured in defined daily doses per 1000 patient-days, was determined for each unit during the same time period. Ciprofloxacin use and MRSA rates for 2004 and 2005 were compared. In the 17 units studied, ciprofloxacin use decreased by 31.2% (P<0.0001). The MRSA rate in these units decreased from 59.6% to 54.2% (P=0.122). There was a correlation between ciprofloxacin use and the MRSA rate within these units (r=0.70; 95% confidence interval -0.01-0.94; P=0.053). Within individual units, there was a variable response. In seven of the units, there was an increase in the MRSA rate despite a reduction in ciprofloxacin use, suggesting that other factors (length of stay, infection control and community-acquired MRSA) may have contributed. Although many factors are associated with high MRSA rates, ciprofloxacin use appears to be a contributing factor. Reducing the use of ciprofloxacin may be a means of controlling MRSA in the hospital setting.     

Studying the transmission dynamics of meticillin-resistant Staphylococcus aureus in Hong Kong using spa typing

This study investigated the transmission dynamics of meticillin-resistant Staphylococcus aureus (MRSA) in a tertiary referral surgical unit with 300 beds. All adult patients were actively screened for MRSA by culture at hospital admission and twice weekly thereafter during hospitalisation from 1 October to 31 December 2008. The colonisation pressure per 1000 patient-days and the incidence density of nosocomial MRSA transmission per 1000 colonisation-days were calculated for the different spa types of MRSA. In total, 6619 nasal swabs were obtained from 2289 patients. One-hundred and forty-eight (7%) patients had MRSA in nasal swabs at admission screening, of which 68/148 (46%) were residents of elderly care homes. Fifty-two of 2141 (2%) patients had conversion of nasal MRSA carriage status from negative to positive during hospitalisation. Among the 200 patients with MRSA, spa types t1081 and t037 were found in 99 (50%) and 30 (15%) patients, respectively. The colonisation pressure per 1000 patient-days was 40.9 for t0181, 22.2 for t037 and 26.3 for the less common spa types. The incidence densities of nosocomial MRSA transmission per 1000 colonisation-days were significantly higher for t1081 (28.5 vs 4.0, P < 0.01) and t037 (21.5 vs 4.0, P = 0.03) compared with the less common spa types. Proactive screening of MRSA in patients from elderly care homes and targeted isolation of these patients, especially those carrying spa types with high transmissibility, are important for the control of MRSA in hospitals.     

Risk factors associated with the conversion of meticillin-resistant Staphylococcus aureus colonisation to healthcare-associated infection

The objective of the study was to identify risk factors for healthcare-associated meticillin-resistant Staphylococcus aureus (HA-MRSA) infections in patients with MRSA colonisation over an extended time period. This was a case–control study conducted at a community teaching hospital. Patients included 41 cases and 82 controls, aged ≥18 years, who were nares colonisation culture positive for MRSA and either did or did not develop an HA-MRSA infection within 60 days after index colonisation, respectively. Potential risk factors evaluated included: patient demographics, comorbid conditions, medication use, presence of invasive devices, presence of wounds or other infections, nutritional status, number of hospitalisations and time to infection development. In the univariate analysis, the presence of peripheral vascular disease, three or more comorbidities, a central venous catheter, a Foley catheter, or two or more hospitalisations were significantly associated with increased risk for HA-MRSA infection. Multivariate analysis yielded a model that included presence of a central venous catheter (OR: 8.00; 95% CI: 3.13–20.4) or two or more hospitalisations (OR: 3.37; 95% CI: 1.37–8.26) as independent risk factors for MRSA infection in those with MRSA colonisation. In conclusion, risk factors independently associated with the conversion of MRSA colonisation to HA-MRSA infection include the presence of a central venous catheter or two or more hospitalisations. Strategies involving risk factor minimisation may be helpful in reducing HA-MRSA infections in this patient population.     

MRSA carriage in healthcare personnel in contact with farm animals

In The Netherlands it has been shown that people in contact with pigs have a higher risk of meticillin-resistant Staphylococcus aureus (MRSA) carriage than the general population. Isolates of closely related spa types, corresponding to multilocus sequence type (MLST) ST398, were found in pig farmers, pig veterinarians and pigs. The objective of this study was to investigate whether contact with pigs and veal calves or other livestock is a risk factor for MRSA carriage in Dutch healthcare workers (HCWs). HCWs at four general hospitals and one university hospital were asked to fill in questionnaires covering contact with animals and to take MRSA cultures of their throat and nares. Cultures of HCWs in contact with livestock were processed with samples from HCWs with no contact with livestock as controls. Seventy-seven of 1721 HCWs (4.4%) reported direct or indirect contact with pigs and/or veal calves and 145 reported contact with other livestock animals. The MRSA carriage rate in the group in contact with pigs and veal calves was 1.7% and in the control group was 0.15%. No carriers were found among HCWs in contact with other livestock. An estimated 3% of hospital staff working in Dutch hospitals serving rural populations belong to a high risk group for MRSA carriage according to the Dutch guidelines. Although MRSA carriage in HCWs in contact with livestock is 10-fold higher than in other HCWs, the difference is not statistically significant.     

Vancomycin versus cefazolin prophylaxis for cerebrospinal shunt placement in a hospital with a high prevalence of meticillin-resistant Staphylococcus aureus

International guidelines suggest that a high prevalence of meticillin-resistant Staphylococcus aureus (MRSA) infections should influence the use of vancomycin for surgical prophylaxis. In order to compare the efficacy and adverse effects of vancomycin versus cefazolin as antimicrobial prophylaxis for insertion of cerebrospinal fluid (CSF) shunts, a randomised prospective clinical trial was performed. Over a 16-month period, all consecutive adult patients who underwent CSF shunt insertion at a university hospital with a high prevalence of MRSA infections were included. Patients were randomly allocated to receive either vancomycin or cefazolin before surgery and followed-up for four weeks for the development of infections. Of the 176 patients included in the study, 88 received vancomycin and 88 cefazolin. Shunt infections were significantly less likely to be observed in patients who were on vancomycin prophylaxis (4% vs 14%; P=0.03). All isolated staphylococci were resistant to meticillin. Mortality of patients with post-surgical infections was higher in the cefazolin group (P=0.02). Our data suggest that use of vancomycin as prophylactic agent for cerebrospinal shunt placement reduces the rate of shunt infections in the context of high prevalence of MRSA.     

Methicillin-Resistant Staphylococcus aureus (MRSA) Detected at Four U.S. Wastewater Treatment Plants

Background: The incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections is increasing in the United States, and it is possible that municipal wastewater could be a reservoir of this microorganism. To date, no U.S. studies have evaluated the occurrence of MRSA in wastewater.Objective: We examined the occurrence of MRSA and methicillin-susceptible S. aureus (MSSA) at U.S. wastewater treatment plants.Methods: We collected wastewater samples from two Mid-Atlantic and two Midwest wastewater treatment plants between October 2009 and October 2010. Samples were analyzed for MRSA and MSSA using membrane filtration. Isolates were confirmed using biochemical tests and PCR (polymerase chain reaction). Antimicrobial susceptibility testing was performed by Sensititre® microbroth dilution. Staphylococcal cassette chromosome mec (SCCmec) typing, Panton-Valentine leucocidin (PVL) screening, and pulsed field gel electrophoresis (PFGE) were performed to further characterize the strains. Data were analyzed by two-sample proportion tests and analysis of variance.Results: We detected MRSA (n = 240) and MSSA (n = 119) in 22 of 44 (50%) and 24 of 44 (55%) wastewater samples, respectively. The odds of samples being MRSA-positive decreased as treatment progressed: 10 of 12 (83%) influent samples were MRSA-positive, while only one of 12 (8%) effluent samples was MRSA-positive. Ninety-three percent and 29% of unique MRSA and MSSA isolates, respectively, were multidrug resistant. SCCmec types II and IV, the pvl gene, and USA types 100, 300, and 700 (PFGE strain types commonly found in the United States) were identified among the MRSA isolates.Conclusions: Our findings raise potential public health concerns for wastewater treatment plant workers and individuals exposed to reclaimed wastewater. Because of increasing use of reclaimed wastewater, further study is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated wastewater.