风险预判与主动干预在综合ICU患者多重耐药菌医院感染防控中的关键作用研究

目的:阐述风险预判与主动干预的综合防控措施对综合重症监护病房(GICU)患者多重耐药菌(MDRO)医院感染的防控效果。方法:对2018年1月~2019年12月入住GICU病房(分为A、B两个病区)>48 h的737例患者进行回顾性调查,其中A病区监测患者286例,MDRO防控参照院感科常规制度要求;B病区监测患者451例,MDRO防控采用入GICU时预判患者感染风险,再根据感染风险及患者自身状况对患者采取鼻腔去定植或肠道去定植的综合防控策略。用卡方检验比较两病区患者的感染结果与MDRO感染菌种分布情况,以验证不同防控策略的效果。结果:本研究共监测GICU住院患者737例,研究期间共发生MDRO医院感染85例。其中A病区监测患者286例,MDRO医院感染66例,感染率为23.1%;B病区监测患者451例,MDRO医院感染19例,感染率为4.2%,低于A病区(P<0.001)。单菌种感染结果显示,两病区感染菌种分布存在差异,CR-AB、CR-PA和MASR的感染率都为B病区低于A病区,两病区患者的共患病类型无差异。说明B病区MDRO防控效果优于A病区。结论:感染风险预判与主动干预的综合防控策略,有利于降低GICU患者MDRO医院感染发病率。     

Modeling the spread of methicillin-resistant Staphylococcus aureus in nursing homes for elderly

Methicillin-resistant Staphylococcus aureus (MRSA) is endemic in many hospital settings, including nursing homes. It is an important nosocomial pathogen that causes mortality and an economic burden to patients, hospitals, and the community. The epidemiology of the bacteria in nursing homes is both hospital- and community-like. Transmission occurs via hands of health care workers (HCWs) and direct contacts among residents during social activities. In this work, mathematical modeling in both deterministic and stochastic frameworks is used to study dissemination of MRSA among residents and HCWs, persistence and prevalence of MRSA in a population, and possible means of controlling the spread of this pathogen in nursing homes. The model predicts that: (i) without strict screening and decolonization of colonized individuals at admission, MRSA may persist; (ii) decolonization of colonized residents, improving hand hygiene in both residents and HCWs, reducing the duration of contamination of HCWs, and decreasing the resident∶staff ratio are possible control strategies; (iii) the mean time that a resident remains susceptible since admission may be prolonged by screening and decolonization treatment in colonized individuals; (iv) in the stochastic framework, the total number of colonized residents varies and may increase when the admission of colonized residents, the duration of colonization, the average number of contacts among residents, or the average number of contacts that each resident requires from HCWs increases; (v) an introduction of a colonized individual into an MRSA-free nursing home has a much higher probability of leading to a major outbreak taking off than an introduction of a contaminated HCW.     

Relevance of intra-hospital patient movements for the spread of healthcare-associated infections within hospitals - a mathematical modeling study

The aim of this study is to analyze patient movement patterns between hospital departments to derive the underlying intra-hospital movement network, and to assess if movement patterns differ between patients at high or low risk of colonization. For that purpose, we analyzed patient electronic medical record data from five hospitals to extract information on risk stratification and patient intra-hospital movements. Movement patterns were visualized as networks, and network centrality measures were calculated. Next, using an agent-based model where agents represent patients and intra-hospital patient movements were explicitly modeled, we simulated the spread of multidrug resistant enterobacteriacae (MDR-E) inside a hospital. Risk stratification of patients according to certain ICD-10 codes revealed that length of stay, patient age, and mean number of movements per admission were higher in the high-risk groups. Movement networks in all hospitals displayed a high variability among departments concerning their network centrality and connectedness with a few highly connected departments and many weakly connected peripheral departments. Simulating the spread of a pathogen in one hospital network showed positive correlation between department prevalence and network centrality measures. This study highlights the importance of intra-hospital patient movements and their possible impact on pathogen spread. Targeting interventions to departments of higher (weighted) degree may help to control the spread of MDR-E. Moreover, when the colonization status of patients coming from different departments is unknown, a ranking system based on department centralities may be used to design more effective interventions that mitigate pathogen spread.     

Modeling the impact of random screening and contact tracing in reducing the spread of HIV

Mathematical models can help predict the effectiveness of control measures on the spread of HIV and other sexually transmitted diseases (STDs) by reducing the uncertainty in assessing the impact of intervention strategies such as random screening and contact tracing. Even though contact tracing is one of the most effective methods used for controlling treatable STDs, it is still a controversial strategy for controlling HIV because of cost and confidentiality issues. To help estimate the effectiveness of these control measures, we formulate two models with random screening and contact tracing based on the differential infectivity (DI) model and the staged-progression (SP) model. We derive formulas for the reproductive numbers and the endemic equilibria and compare the impact that random screening and contact tracing have in slowing the epidemic in the two models. In the DI model the infected population is divided into groups according to their infectiousness, and HIV is largely spread by a small, highly infectious, group of superspreaders. In this model contact tracing is an effective approach to identifying the superspreaders and has a large effect in slowing the epidemic. In the SP model every infected individual goes through a series of infection stages and the virus is primarily spread by individuals in an initial highly infectious stage or in the late stages of the disease. In this model random screening is more effective than for the DI model, and contact tracing is less effective. Thus the effectiveness of the intervention strategy strongly depends on the underlying etiology of the disease transmission.     

感控干预在控制多重耐药定植菌医院感染的临床研究

目的研究多重耐药定植菌与医院感染的关系以及去定植措施的效果。方法对入住ICU的患者进行多重耐药定植菌筛查,观察阳性患者和阴性患者医院感染发生率;将阳性患者随机分为对照组和试验组,对照组采用常规的预防控制措施,试验组加上安尔碘Ⅲ去鼻腔MRSA、口服金双歧去肠道产ESBLs肠杆菌措施,观察两组患者医院感染发生率以及定植菌与医院感染的关系,对比两组去定植效果。结果ICU多重耐药菌定植率为31. 16% ;多重耐药定植菌筛查阴性患者医院感染率为7. 56%,阳性患者医院感染率为15.47% （P 〈0.01）;对照组医院感染率为20.79%,试验组医院感染率为22. 22% （P 〉0. 05）;对照组定植菌医院感染率为4. 95% ,试验组定植菌医院感染为0（ P 〈0.01）;对照组产ESBLs大肠埃希菌定植自行清除率为26. 31% ,试验组产ESBLs大肠埃希菌去定植率为80. 95% （P 〈 0. 01）。结论ICU患者多重耐药菌定植率高,多重耐药菌定植患者医院感染率高,口服金双歧去肠道产ESBLs细菌干预措施有效,安尔碘Ⅲ去鼻腔MRSA效果需继续研究。     

On being the right size: the impact of population size and stochastic effects on the evolution of drug resistance in hospitals and the community

The evolution of drug resistant bacteria is a severe public health problem, both in hospitals and in the community. Currently, some countries aim at concentrating highly specialized services in large hospitals in order to improve patient outcomes. Emergent resistant strains often originate in health care facilities, but it is unknown to what extent hospital size affects resistance evolution and the resulting spillover of hospital-associated pathogens to the community. We used two published datasets from the US and Ireland to investigate the effects of hospital size and controlled for several confounders such as antimicrobial usage, sampling frequency, mortality, disinfection and length of stay. The proportion of patients acquiring both sensitive and resistant infections in a hospital strongly correlated with hospital size. Moreover, we observe the same pattern for both the percentage of resistant infections and the increase of hospital-acquired infections over time. One interpretation of this pattern is that chance effects in small hospitals impede the spread of drug-resistance. To investigate to what extent the size distribution of hospitals can directly affect the prevalence of antibiotic resistance, we use a stochastic epidemiological model describing the spread of drug resistance in a hospital setting as well as the interaction between one or several hospitals and the community. We show that the level of drug resistance typically increases with population size: In small hospitals chance effects cause large fluctuations in pathogen population size or even extinctions, both of which impede the acquisition and spread of drug resistance. Finally, we show that indirect transmission via environmental reservoirs can reduce the effect of hospital size because the slow turnover in the environment can prevent extinction of resistant strains. This implies that reducing environmental transmission is especially important in small hospitals, because such a reduction not only reduces overall transmission but might also facilitate the extinction of resistant strains. Overall, our study shows that the distribution of hospital sizes is a crucial factor for the spread of drug resistance.     

The Impact of Syphilis Screening among Female Sex Workers in China: A Modelling Study

Background

In China, female sex workers (FSWs) are at high risk of syphilis infection, but are hard to reach for interventions. Point-of-care testing introduces opportunities for expanding syphilis control measures. Modelling is used to estimate the impact of using rapid tests to screen FSWs for syphilis. In other settings, modelling has predicted large rebounds in infectious syphilis following screening, which may undermine any impact achieved.

Methods

A deterministic syphilis transmission model among FSWs and clients was fitted to data from Yunnan Province (FSW syphilis prevalence = 7.5%), and used to estimate the impact of rapid syphilis testing and treatment for FSWs. Impact projections were compared for different model structures that included risk heterogeneity amongst FSWs, incoming syphilis infections amongst new FSWs and clients and re-infection from FSWs'' regular non-commercial partners. The rebound in syphilis prevalence after screening ceased was explored.

Results

All model structures suggest yearly syphilis screening could substantially reduce (by 72–88%) syphilis prevalence amongst FSWs in this setting over five years. However, incoming syphilis infections amongst new FSWs and clients or re-infections from regular non-commercial partners of FSWs can considerably reduce (>30%) the proportion of infections averted. Including heterogeneity in risk amongst FSWs had little effect upon the proportion of infections averted. In this setting, the rebound in syphilis prevalence after screening ceased is predicted to be slight, but it could be large in high prevalence settings.

Conclusions

Rapid test screening could dramatically reduce syphilis prevalence amongst hard-to-reach groups, but strategies to reduce re-infection from regular non-commercial partners are needed to maximise impact.     

Prevalence of anti hepatitis C virus among the hospital populations in Jordan

Five hundred and seventy-eight individuals in two hospitals in the Amman area were screened for anti hepatitis C virus (anti HCV). The results of this study indicate the prevalence of anti HCV in the hospital population ranged from 0.65 to 6.25% depending on the sub population studied. Comparison studies revealed the hospital employees' prevalence rate was the lowest and kidney dialysis patients the highest. Invasive medical procedures, tattooing and education level effects on the prevalence of HCV were evaluated and it may have an impact on HCV spread of infection. Age group distribution studies of those who have positive anti HCV indicated an increased rate with age.     

Modelling the costs and effects of selective and universal hospital admission screening for methicillin-resistant Staphylococcus aureus

Background

Screening at hospital admission for carriage of methicillin-resistant Staphylococcus aureus (MRSA) has been proposed as a strategy to reduce nosocomial infections. The objective of this study was to determine the long-term costs and health benefits of selective and universal screening for MRSA at hospital admission, using both PCR-based and chromogenic media-based tests in various settings.

Methodology/Principal Findings

A simulation model of MRSA transmission was used to determine costs and effects over 15 years from a US healthcare perspective. We compared admission screening together with isolation of identified carriers against a baseline policy without screening or isolation. Strategies included selective screening of high risk patients or universal admission screening, with PCR-based or chromogenic media-based tests, in medium (5%) or high nosocomial prevalence (15%) settings. The costs of screening and isolation per averted MRSA infection were lowest using selective chromogenic-based screening in high and medium prevalence settings, at $4,100 and $10,300, respectively. Replacing the chromogenic-based test with a PCR-based test costs $13,000 and $36,200 per additional infection averted, and subsequent extension to universal screening with PCR would cost $131,000 and $232,700 per additional infection averted, in high and medium prevalence settings respectively. Assuming $17,645 benefit per infection averted, the most cost-saving strategies in high and medium prevalence settings were selective screening with PCR and selective screening with chromogenic, respectively.

Conclusions/Significance

Admission screening costs $4,100–$21,200 per infection averted, depending on strategy and setting. Including financial benefits from averted infections, screening could well be cost saving.     

Clinical significance of the emergence of bacterial resistance in the hospital environment

Antibiotic resistance is an increasing threat in hospitals and both morbidity and mortality from infections are greater when caused by drug-resistant organisms. Whilst hospitals are universally blamed for this increase, there is an insufficient appreciation of external sources of resistance, such as when patients are admitted to hospitals from long-term care facilities in the community. The use of antibiotics in family practice and animal husbandry has also been linked to drug resistance being encountered in the hospital setting. Justifiable hospital antibiotic use, which can be life saving, may lead to 'collateral damage' with the emergence of resistance in non-target bacteria in the bowel, for example, with subsequent spread by cross-infection. At a management level, antibiotic resistance can have a significant impact on the ability of hospitals to maintain services since cohorting of patients and ward closures from outbreaks add to continuing bed shortages and waiting lists. Hospital laboratories must review their standard operating procedures since some resistance mechanisms may be missed by current methods of antibiotic susceptibility testing. With increasing public concern from press reports of 'multiresistant Staphylococcus aureus killer virus' and other drug-resistant organisms, there will inevitably be a push by national authorities for more surveillance data on antibiotic resistance; however, the cost-effectiveness of different surveillance strategies should be considered. Clinical governance and risk management are dominant themes in the National Health Service and hospital hygiene and antibiotic resistance are likely to feature prominently in audits related to these themes in the near future.     

Prevalence and significance of hepatitis B surface antigen in a general hospital.

Over a 6-month period 2025 patients admitted to New Mount Sinai Hospital, Toronto were screened for hepatitis B surface antigen (HBsAg) by counter-immunoelectrophoresis (CIEP) and radioimmunoassay (RIA). CIEP detected 12 HBsAg-positive patients and RIA 16. RIA is therefore the more sensitive test for HBsAg. Of the 16 patients 2 had liver disease previously diagnosed, 3 had malignant disease and 11 were asymptomatic carriers. Of the 11 carriers all were born in countries where the carrier rate is known to be high. Routine screening of hospital patients on admission is of no value in detecting unsuspected liver disease but is of value in detecting asymptomatic carriers, which is of importance for the patient and his family. Routine screening tests for HBsAg in Canadian hospitals that treat many patients born in countries with a known high HBsAg prevalence is recommended. Routine screening is also recommended in all hospitals in Mediterranean and Asian countries.     

Identification of infant food as a vehicle in a nosocomial outbreak of Citrobacter freundii: epidemiological subtyping by allozyme, whole-cell protein and antibiotic resistance

A total of 38 Citrobacter freundii strains was isolated from patients and their environment at a neonatal intensive care unit of a large hospital where colonization and clinical diseases due to the agent had been observed. Epidemiological investigations were carried out by subtyping, for which a combination of allozyme, whole-cell protein and resistance pattern analysis was used. Infant formula was identified as a vehicle of nosocomial spread. This shows that the role of foods in the transmission of hospital infections should not be underestimated.
The combination of methods applied, in particular a limited enzyme set, is recommended also for epidemiological investigations of food-borne infections and establishment of their causes.     

高海拔地区慢性阻塞性肺疾病患者 病原菌分布及相关因素分析

摘要：目的 探究高海拔地区慢性阻塞性肺疾病（COPD）患者病原菌分布及相关危险因素。方法 选取2016年1月至2019年1月青海省中医院收治的274例COPD患者为研究对象,对患者痰液进行病原菌培养,分析病原菌分布情况及感染多重耐药菌（MDRO）的相关危险因素。结果 274例患者痰液中共培养出致病菌165株,阳性率为60.2%;其中革兰阴性菌占71.5%（118/165）,革兰阳性菌占17.0%（28/165）,真菌占11.5%（19/165）。单因素分析显示,COPD患者发生MDRO感染与年龄、糖尿病病史、卧床时间、呼吸机污染、机械通气史和频繁更换抗菌药有一定相关性（χ2=8.326、4.868、21.298、5.534、19.686、11.549,均P<0.05）,Logistic分析显示,呼吸机污染、机械通气史、频繁更换抗菌药和卧床时间是COPD患者发生多重耐药菌感染的危险因素（OR=1.292、2.112、1.752、1.625,均P<0.05）。结论 高海拔地区COPD患者病原菌以革兰阴性菌为主,而呼吸机及管路污染、机械通气史、频繁更换抗菌药及卧床时间长是COPD患者发生多重耐药菌感染的危险因素。应加强对相关病原菌及危险因素的监测,降低患者感染风险。     

The digestive tract in immunocompromised patients: importance of maintaining its resistance to colonization,especially in hospital in-patients and those taking antibiotics

The colonization resistance (CR) of the gastrointestinal tract to potential pathogens depends partly on factors within the host but to a greater extent on the normal (anaerobic) gut flora. Its strength varies between individuals. These individual differences in resistance to colonization by pathogenic microorganisms may explain differences in susceptibility to infection. CR is lowered by remission-inducing treatment (radiation and/or chemotherapy) in leukaemia, but more severely by certain antibiotics. Development (by selection or transfer) of resistance to these antibiotics may lead to overgrowth and penetration of the mucosal lining by the overgrowing (potentially) pathogenic bacteria. Other antibiotics however, if sufficiently dosed, have been found to eliminate (potential) pathogens selectively without decreasing CR. This selective decontamination of the gastrointestinal tract has been successfully used prophylactically in neutropenic patients but needs to be monitored bacteriologically. It should perhaps be used more widely in the hospital to control development and spread of antibiotic-resistant strains.     

Effects of Population Based Screening for Chlamydia Infections in The Netherlands Limited by Declining Participation Rates

Background

A large trial to investigate the effectiveness of population based screening for chlamydia infections was conducted in the Netherlands in 2008–2012. The trial was register based and consisted of four rounds of screening of women and men in the age groups 16–29 years in three regions in the Netherlands. Data were collected on participation rates and positivity rates per round. A modeling study was conducted to project screening effects for various screening strategies into the future.

Methods and Findings

We used a stochastic network simulation model incorporating partnership formation and dissolution, aging and a sexual life course perspective. Trends in baseline rates of chlamydia testing and treatment were used to describe the epidemiological situation before the start of the screening program. Data on participation rates was used to describe screening uptake in rural and urban areas. Simulations were used to project the effectiveness of screening on chlamydia prevalence for a time period of 10 years. In addition, we tested alternative screening strategies, such as including only women, targeting different age groups, and biennial screening. Screening reduced prevalence by about 1% in the first two screening rounds and leveled off after that. Extrapolating observed participation rates into the future indicated very low participation in the long run. Alternative strategies only marginally changed the effectiveness of screening. Higher participation rates as originally foreseen in the program would have succeeded in reducing chlamydia prevalence to very low levels in the long run.

Conclusions

Decreasing participation rates over time profoundly impact the effectiveness of population based screening for chlamydia infections. Using data from several consecutive rounds of screening in a simulation model enabled us to assess the future effectiveness of screening on prevalence. If participation rates cannot be kept at a sufficient level, the effectiveness of screening on prevalence will remain limited.     

Close encounters in a pediatric ward: measuring face-to-face proximity and mixing patterns with wearable sensors

Background

Nosocomial infections place a substantial burden on health care systems and represent one of the major issues in current public health, requiring notable efforts for its prevention. Understanding the dynamics of infection transmission in a hospital setting is essential for tailoring interventions and predicting the spread among individuals. Mathematical models need to be informed with accurate data on contacts among individuals.

Methods and Findings

We used wearable active Radio-Frequency Identification Devices (RFID) to detect face-to-face contacts among individuals with a spatial resolution of about 1.5 meters, and a time resolution of 20 seconds. The study was conducted in a general pediatrics hospital ward, during a one-week period, and included 119 participants, with 51 health care workers, 37 patients, and 31 caregivers. Nearly 16,000 contacts were recorded during the study period, with a median of approximately 20 contacts per participants per day. Overall, 25% of the contacts involved a ward assistant, 23% a nurse, 22% a patient, 22% a caregiver, and 8% a physician. The majority of contacts were of brief duration, but long and frequent contacts especially between patients and caregivers were also found. In the setting under study, caregivers do not represent a significant potential for infection spread to a large number of individuals, as their interactions mainly involve the corresponding patient. Nurses would deserve priority in prevention strategies due to their central role in the potential propagation paths of infections.

Conclusions

Our study shows the feasibility of accurate and reproducible measures of the pattern of contacts in a hospital setting. The obtained results are particularly useful for the study of the spread of respiratory infections, for monitoring critical patterns, and for setting up tailored prevention strategies. Proximity-sensing technology should be considered as a valuable tool for measuring such patterns and evaluating nosocomial prevention strategies in specific settings.     

Patient Referral Patterns and the Spread of Hospital-Acquired Infections through National Health Care Networks

Rates of hospital-acquired infections, such as methicillin-resistant Staphylococcus aureus (MRSA), are increasingly used as quality indicators for hospital hygiene. Alternatively, these rates may vary between hospitals, because hospitals differ in admission and referral of potentially colonized patients. We assessed if different referral patterns between hospitals in health care networks can influence rates of hospital-acquired infections like MRSA. We used the Dutch medical registration of 2004 to measure the connectedness between hospitals. This allowed us to reconstruct the network of hospitals in the Netherlands. We used mathematical models to assess the effect of different patient referral patterns on the potential spread of hospital-acquired infections between hospitals, and between categories of hospitals (University medical centers, top clinical hospitals and general hospitals). University hospitals have a higher number of shared patients than teaching or general hospitals, and are therefore more likely to be among the first to receive colonized patients. Moreover, as the network is directional towards university hospitals, they have a higher prevalence, even when infection control measures are equally effective in all hospitals. Patient referral patterns have a profound effect on the spread of health care-associated infections like hospital-acquired MRSA. The MRSA prevalence therefore differs between hospitals with the position of each hospital within the health care network. Any comparison of MRSA rates between hospitals, as a benchmark for hospital hygiene, should therefore take the position of a hospital within the network into account.     

Comparing apples and oranges--model-based assessment of different tsetse-transmitted trypanosomosis control strategies

The current control strategies for tsetse-transmitted trypanosomosis in cattle (trypanocidal drugs, tsetse control and trypanotolerant cattle) are briefly reviewed and their adoption rates in different geographic regions of sub-Saharan Africa are presented. The impact of these control strategies and the potential use of vaccines, should they be developed, on trypanosomosis transmission were compared using a mathematical model. The relative trypanosomosis prevalence compared with no control was estimated across a range of control coverages (from none to complete control coverage) by varying the change in specific model parameters influenced by individual control measures. Based on this comparison, the relative rankings of the effect of control strategies on reducing disease prevalence were: vector control, vaccination, and drug use, in that order. In this model, trypanotolerance was assumed to decrease disease prevalence, but not to influence transmission. Differences in the predicted impact of control measures on the transmission of human sleeping sickness are discussed. Finally, the role of transmission model outputs as inputs for economic models to guide investment decisions for trypanosomosis control is emphasised.     

Spatial heterogeneity and rates of spread in experimental streams

Theoretical models predict that environmental heterogeneity can decrease or potentially increase rates of spread in biological populations depending on the relationship between the scale of dispersal and the scale of heterogeneity. These effects arise from the interaction between habitat quality and the processes of dispersal, colonization and growth. Flowing water environments provide a unique opportunity to test these predictions. If advection influences dispersal, flow can alter the relative scale of dispersal to environmental heterogeneity in the upstream versus downstream direction. We explored the influence of heterogeneity on the spatial spread of a species of diatom in experimental streams. Environmental heterogeneity was created by maintaining agar diffusing substrata at different nutrient levels. Diatoms were placed at the midpoint of each stream, and spatial spread rates were determined by monitoring algal abundance non‐destructively. Our results reveal that, relative to homogeneous streams, resource heterogeneity decreases spread rate in the upstream direction but increases spread rate in the downstream direction. Empirical estimates of growth rates and colonization times reveal that heterogeneity predominantly influenced colonization rates. Colonization rates estimate successful dispersal events, and thus relate to both colonization and dispersal. These results are one of the first empirical tests of general theories regarding the impact of heterogeneity on rates of spread and highlight the importance of understanding the impact of heterogeneity on colonization and dispersal in continuous habitats.     

Methicillin-resistant Staphylococcus aureus (MRSA) screening of hospital dental clinic surfaces

We assessed the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) strains on surfaces of hospital dental clinics. Specimens were obtained from 5 clinically symptoms-free patients of five different specialties clinics (Implantology, Pediatric Dentistry, Prosthetics, Restorative Dentistry, and Oral Medicine) of the Dental Clinic Hospital of King Saud University before and after each patient. A Q-tip swabs were used from 10 surfaces in each clinic (Arm rest of dental chair, floor beneath dental chair, sink/faucet, towel dispenser, instrument table handle, light handle, X-ray viewer, paper dental records, head rest, and bench). Specimens were cultured in CHROMagar MRSA medium. Prevalence of MRSA colonization was compared between periods before and after patients visited each clinic for treatment. The results showed that the prevalence of MRSA was remarkably increased after patients visited the area. The results indicate that dental clinics should be considered as possible reservoirs of MRSA in the hospital setting.