Refractory methicillin-resistant Staphylococcus aureus carriage associated with contamination of the home environment

Household Transmission of Community-Associated Methicillin-Resistant Staphylococcus Aureus

Currently, the mechanism of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) transmission mechanism is unclear; however, it must be considered in conjunction with asymptomatic S. aureus strains colonization dynamics. This epidemiological study aimed to determine the role of the household in CA-MRSA transmission in China. Five patients with culture-confirmed CA-MRSA infection and five control patients were recruited from the Sir Run Run Shaw Hospital in Zhejiang, China, between December 2019 and January 2020. The household members of the patients, their pets, and environmental surfaces were sampled and screened for MRSA colonization. Mass spectrometry identification and antimicrobial susceptibility testing were performed on the MRSA isolates. Whole-genome sequencing and core genome multilocus sequence typing (cgMLST) were performed to determine the origin and transmission of the MRSA isolates in the households. Overall, 14 S. aureus-positive specimens (14.1%, 14/99) were obtained from the five households of patients with CA-MRSA infections, of which 12 (85.7%) were MRSA. The overall positivity of MRSA was 12.1% (12/99) among the samples from the CA-MRSA households, while no MRSA isolates were detected in the five control households. Most MRSA isolates belonged to epidemic CA-MRSA clones, such as ST59 (15/35, 42.9%) and ST508 (15/35, 42.9%). The cgMLST results confirmed that MRSA was transmitted among patients, contacts, and pets in the households and was present on environmental surfaces in the CA-MRSA patients' households. In conclusion, the study revealed that the home environment was an important MRSA reservoir. Therefore, focusing on MRSA decolonization in patients alone is not sufficient for infection control of CA-MRSA.

Reducing antibiotic prescribing and addressing the global problem of antibiotic resistance by targeted hygiene in the home and everyday life settings: A position paper

Antimicrobial resistance (AMR) continues to threaten global health. Although global and national AMR action plans are in place, infection prevention and control is primarily discussed in the context of health care facilities with home and everyday life settings barely addressed. As seen with the recent global SARS-CoV-2 pandemic, everyday hygiene measures can play an important role in containing the threat from infectious microorganisms. This position paper has been developed following a meeting of global experts in London, 2019. It presents evidence that home and community settings are important for infection transmission and also the acquisition and spread of AMR. It also demonstrates that the targeted hygiene approach offers a framework for maximizing protection against colonization and infections, thereby reducing antibiotic prescribing and minimizing selection pressure for the development of antibiotic resistance. If combined with the provision of clean water and sanitation, targeted hygiene can reduce the circulation of resistant bacteria in homes and communities, regardless of a country's Human Development Index (overall social and economic development). Achieving a reduction of AMR strains in health care settings requires a mirrored reduction in the community. The authors call upon national and international policy makers, health agencies, and health care professionals to further recognize the importance of targeted hygiene in the home and everyday life settings for preventing and controlling infection, in a unified quest to tackle AMR.

Community- and Healthcare-Associated Methicillin-Resistant Staphylococcus aureus Strains: An Investigation Into Household Transmission, Risk Factors, and Environmental Contamination

OBJECTIVE To measure transmission frequencies and risk factors for household acquisition of community-associated and healthcare-associated (HA-) methicillin-resistant Staphylococcus aureus (MRSA). DESIGN Prospective cohort study from October 4, 2008, through December 3, 2012. SETTING Seven acute care hospitals in or near Toronto, Canada. PARTICIPANTS Total of 99 MRSA-colonized or MRSA-infected case patients and 183 household contacts. METHODS Baseline interviews were conducted, and surveillance cultures were collected monthly for 3 months from household members, pets, and 8 prespecified high-use environmental locations. Isolates underwent pulsed-field gel electrophoresis and staphylococcal cassette chromosome mec typing. RESULTS Overall, of 183 household contacts 89 (49%) were MRSA colonized, with 56 (31%) detected at baseline. MRSA transmission from index case to contacts negative at baseline occurred in 27 (40%) of 68 followed-up households. Strains were identical within households. The transmission risk for HA-MRSA was 39% compared with 40% (P=.95) for community-associated MRSA. HA-MRSA index cases were more likely to be older and not practice infection control measures (P=.002-.03). Household acquisition risk factors included requiring assistance and sharing bath towels (P=.001-.03). Environmental contamination was identified in 78 (79%) of 99 households and was more common in HA-MRSA households. CONCLUSION Household transmission of community-associated and HA-MRSA strains was common and the difference in transmission risk was not statistically significant. Infect Control Hosp Epidemiol 2016;1-7.

Use of Gaseous Ozone for Eradication of Methicillin-ResistantStaphylococcus aureusFrom the Home Environment of a Colonized Hospital Employee

An intensive care nurse with eczema was repeatedly treated for methicillin-resistantStaphylococcus aureus(MRSA) carriage. Because cultures remained positive for MRSA, her house was investigated. Thirty-four percent of environmental samples yielded MRSA. Her children and cat were free of MRSA. The house was decontaminated with gaseous ozone. All subsequent cultures were negative for MRSA. This decontamination cost €2,000 (approximately $2,400).

Personal and household hygiene, environmental contamination, and health in undergraduate residence halls in New York City, 2011

BACKGROUND

While several studies have documented the importance of hand washing in the university setting, the added role of environmental hygiene remains poorly understood. The purpose of this study was to characterize the personal and environmental hygiene habits of college students, define the determinants of hygiene in this population, and assess the relationship between reported hygiene behaviors, environmental contamination, and health status.

METHODS

501 undergraduate students completed a previously validated survey assessing baseline demographics, hygiene habits, determinants of hygiene, and health status. Sixty survey respondents had microbiological samples taken from eight standardized surfaces in their dormitory environment. Bacterial contamination was assessed using standard quantitative bacterial culture techniques. Additional culturing for coagulase-positive Staphylococcus and coliforms was performed using selective agar.

RESULTS

While the vast majority of study participants (n = 461, 92%) believed that hand washing was important for infection prevention, there was a large amount of variation in reported personal hygiene practices. More women than men reported consistent hand washing before preparing food (p = .002) and after using the toilet (p = .001). Environmental hygiene showed similar variability although 73.3% (n = 367) of subjects reported dormitory cleaning at least once per month. Contamination of certain surfaces was common, with at least one third of all bookshelves, desks, refrigerator handles, toilet handles, and bathroom door handles positive for >10 CFU of bacteria per 4 cm(2) area. Coagulase-positive Staphylococcus was detected in three participants' rooms (5%) and coliforms were present in six students' rooms (10%). Surface contamination with any bacteria did not vary by frequency of cleaning or frequency of illness (p>.05).

CONCLUSIONS

Our results suggest that surface contamination, while prevalent, is unrelated to reported hygiene or health in the university setting. Further research into environmental reservoirs of infectious diseases may delineate whether surface decontamination is an effective target of hygiene interventions in this population.

Community-based infections and the potential role of common touch surfaces as vectors for the transmission of infectious agents in home and community settings

Community-based pathogens that can survive on common touch surfaces include those that can cause gastrointestinal, respiratory, and skin infections. Our hands play an obvious role in the transmission of many of these pathogens, but common touch surfaces are also part of the transmission equation. Traditionally, common touch surfaces have not been the main focus of cleaning and sanitation in household and community settings. Infectious disease continues to be of concern globally due in part to emergence of new pathogens, antibiotic-resistant organisms, and a growing immunocompromised community. As a result, it is important to prevent and minimize the infection risk in homes and in the community. Understanding the role of common touch surfaces should inform surface hygiene practices and these surfaces should be the subject of future intervention studies.

Household transmission of meticillin-resistant Staphylococcus aureus and other staphylococci

Although the role of pets in household transmission of meticillin-resistant Staphylococcus aureus (MRSA) has been examined previously, only minor attention has been given to the role of the abiotic household environment independent of, or in combination with, colonisation of pets and human beings to maintain transmission cycles of MRSA within the household. This report reviews published work about household transmission of S aureus and other staphylococci and describes contamination of household environmental surfaces and colonisation of pets and people. Household microbial communities might have a role in transfer of antimicrobial resistance genes and could be reservoirs for recolonisation of people, although additional research is needed regarding strategies for decontamination of household environments. Household-based interventions should be developed to control recurrent S aureus infections in the community, and coordination between medical and veterinary providers could be beneficial.

Dry collection and culture methods for recovery of methicillin-susceptible and methicillin-resistant Staphylococcus aureus strains from indoor home environments

Staphylococcus aureus in home environments may serve as a reservoir for human colonization, making sampling of indoor surfaces relevant to exposure assessment. Using laboratory experiments and application to homes of asthmatic children in Barbados, we characterize microbiological methods adapted for settings with transportation delays between sampling and initiation of culture.

The environment as an unrecognized reservoir for community-associated methicillin resistant Staphylococcus aureus USA300: a case-control study

Background

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are spreading, but the source of infections in non-epidemic settings remains poorly defined.

Methods

We carried out a community-based, case-control study investigating socio-demographic risk factors and infectious reservoirs associated with MRSA infections. Case patients presented with CA-MRSA infections to a New York hospital. Age-matched controls without infections were randomly selected from the hospital's Dental Clinic patient population. During a home visit, case and control subjects completed a questionnaire, nasal swabs were collected from index respondents and household members and standardized environmental surfaces were swabbed. Genotyping was performed on S. aureus isolates.

Results

We enrolled 95 case and 95 control subjects. Cases more frequently reported diabetes mellitus and a higher number of skin infections among household members. Among case households, 53 (56%) were environmentally contaminated with S. aureus, compared to 36 (38%) control households (p = .02). MRSA was detected on fomites in 30 (32%) case households and 5 (5%; p<.001) control households. More case patients, 20 (21%) were nasally colonized with MRSA than were control indexes, 2 (2%; p<.001). In a subgroup analysis, the clinical isolate (predominantly USA300), was more commonly detected on environmental surfaces in case households with recurrent MRSA infections (16/36, 44%) than those without (14/58, 24%, p = .04).

Conclusions

The higher frequency of environmental contamination of case households with S. aureus in general and MRSA in particular implicates this as a potential reservoir for recolonization and increased risk of infection. Environmental colonization may contribute to the community spread of epidemic strains such as USA300.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

The environment as a factor in methicillin-resistant Staphylococcus aureus transmission

In recent years, methicillin-resistant Staphylococcus aureus (MRSA) has become a leading cause of infectious disease morbidity and mortality in the United States. The epidemiology of the organism has changed, with novel strains emerging in the community among individuals lacking any healthcare contact. Although direct human-to-human transmission via skin contact is one way for this organism to spread, transmission via environmental contamination of fomites or through air are other potential ways that the organism can be acquired. As such, an improved understanding of MRSA transmission is needed to implement maximally effective control and prevention interventions. We review the research documenting the role of the environment in MRSA spread.

A critical evaluation of methicillin-resistant Staphylococcus aureus and other bacteria of medical interest on commonly touched household surfaces in relation to household demographics

BACKGROUND

We sought to characterize and quantify bacteria of medical interest on commonly touched household surfaces and to evaluate predictors such as employment, day care attendance, and presence of infants and pets.

METHODS

A convenience sample of 35 homes was recruited from the metro-Boston area, and up to 32 surfaces were sampled in kitchens, bathrooms, and living areas.

RESULTS

Highest bacterial counts were associated with wet sites including hand/skin contact surfaces such as the tub, kitchen sink, and faucet handles. Surfaces were found to be contaminated with the bacteria of medical interest including species of Enterobacteriaceae, Pseudomonas, methicillin-sensitive Staphyloccus aureus (MSSA), and methicillin-resistant Staphyloccus aureus (MRSA).

CONCLUSION

A number of hand/skin contact surfaces were found to be frequently contaminated with one or more of the bacteria of medical interest. The presence of a cat in the home was found to be a strong predictor for the isolation of MRSA. This study provides further insight about microorganisms of medical interest on surfaces in American homes and the impact of factors that can influence bacterial contamination. The study may indicate that cleaning in private homes should be directed to the areas pinpointed by the study as very rich in bacteria of potential medical importance.

High prevalence of MRSA in household contacts

In a 6-y period, 114 household contacts connected to newly diagnosed MRSA patients screened for MRSA in the southern part of Sweden. In 22 of 51 (43%) families, 1 to 4 household contact(s) connected to a MRSA patient were positive for MRSA. In the 22 families, 42 of 60 (70%) household contacts were positive for MRSA and transmission of MRSA occurred between adult couples, parents and children, grandparent and children and between siblings. Within a family, MRSA-positive family members had in all but 1 instance identical MRSA strain genotypes (spa types) making intrafamilial spread of MRSA highly probable. MRSA transmission among household contacts may contribute to the prevalence of MRSA in the community and failure to identify MRSA in household contacts may maintain MRSA colonization in an already known MRSA patient. MRSA screening of family members living in the same household as a known MRSA patient should therefore be considered.

Implementing the MRSA recommendations made by the Commission for Hospital Hygiene and Infection Prevention (KRINKO) of 1999 - current considerations by the DGKH Management Board

In Germany, recommendations on dealing with patients who are colonised with methicillin-resistant S. aureus (MRSA) for the inpatient sector have been published in 1999 by the Commission for Hospital Hygiene and Infection Prevention (KRINKO). Some challenges arise with regard to the practical implementation of the KRINKO recommendations. These challenges do not principally question the benefit of the recommendations but have come into criticism from users. In this commentary the German Society for Hospital Hygiene (DGKH) discusses some controversial issues and adds suggestions for unresolved problems regarding the infection control management of MRSA in healthcare settings.

[Risk of infection in the home environment. Plea for a new risk assessment]

Within the last two decades risks posed by infectious diseases outside of hospitals and nursing homes had no high significance in the public perception. The home environment is regarded as a save shelter from infectious risks. In the mean time there have been dramatic socio-demographic, health policy and technological changes which have increased infectious risks outside medical facilities. In Germany up to 1.4 million people with multiple morbidities are nursed at home. Technological changes with the aim to protect the environment, like reduction of water temperature and water volumes in washing processes has lowered the efficacy to control pathogens. Thus it is time to revise the process of risk assessment in which not only aspects of environmental protection but also those of health protection must be taken into account. The article gives an overview of new risks and epidemiological changes and discusses the necessity of a new risk assessment and risk management approach which hopefully will lead to a changing paradigm.

The role of healthcare personnel in the maintenance and spread of methicillin-resistant Staphylococcus aureus

Healthcare workers may acquire methicillin-resistant Staphylococcus aureus (MRSA) from patients, both hospital and home environments, other healthcare workers, family and public acquaintances, and pets. There is a consensus of case reports and series which now strongly support the role for MRSA-carrying healthcare personnel to serve as a reservoir and as a vehicle of spread within healthcare settings. Carriage may occur at a number of body sites and for short, intermediate, and long terms. A number of approaches have been taken to interrupt the linkage of staff-patient spread, but most emphasis has been placed on handwashing and the treatment of staff MRSA carriers. The importance of healthcare workers in transmission has been viewed with varying degrees of interest, and several logistical problems have arisen when healthcare worker screening is brought to the forefront. There is now considerable support for the screening and treatment of healthcare workers, but it is suggested that the intensity of any such approach must consider available resources, the nature of the outbreak, and the strength of epidemiological associations. The task of assessing healthcare personnel carriage in any context should be shaped with due regard to national and international guidelines, should be honed and practiced according to local needs and experience, and must be patient-oriented.

Biometric fingerprinting for visa application: device and procedure are risk factors for infection transmission

BACKGROUND

Biometric fingerprint identity verification is currently introduced in visa application and entry screening at border control. The system implies physical contact between the skin and the surface of the fingerprint-capturing and reading devices.

AIM

To assess the risk of infection transmission through fingerprinting.

METHODS

The medical literature was reviewed for the potential of microorganisms to be carried on the skin of hands in the community, to be transferred from hands to inanimate surfaces, to survive on surfaces, and to be transferred in doses exceeding the infectious dose. The fingerprinting procedures as currently applied were reviewed.

RESULTS

Factors that favor transfer of microorganisms are large skin-surface contact between flat fingers (2 x 20 cm(2)) and fingerprint-capturing device, nonporous contact surface, large overlap of contact surface and short turnaround time between successive applicants, high contact pressure, and difficulties to disinfect devices. Transmission risk exists for enteric viruses (rotavirus, norovirus, and hepatitis A virus), respiratory viruses (respiratory syncytial virus, rhinovirus, influenza virus, etc.), and enteropathogenic bacteria with low infectious doses (Shigella dysenteriae, Enterohemorrhagic Escherichia coli, etc.). Using Monte Carlo risk analysis on US data, transmission of human rotavirus is estimated at 191 [95% credible intervals (CI) 0-289] per million fingerprint-capturing procedures. Application of 70% isopropyl hand rub and 85% ethanol hand gel reduces the risk to 77 (95% CI 0-118) and 0.3 (95% CI 0-0.3) transmissions per million procedures, respectively.

CONCLUSIONS

The fingerprinting procedure as currently used is associated with a risk of infection transmission. Simple hygienic measures can considerably reduce this transmission risk.

A pilot study to isolate Staphylococcus aureus and methicillin-resistant S aureus from environmental surfaces in the home

BACKGROUND

The major sources of Staphylococcus aureus, including methicillin-resistant S aureus (MRSA), in the home are colonized or infected individuals and pets, such as cats and dogs; however, the occurrence of MRSA on surfaces in healthy homes is not well documented.

METHODS

A convenience sample comprising 35 homes of health care and non-health care workers, each with a child in diapers and either a cat or dog in the home, was recruited from the Boston area between January and April 2006. In each home, a total of 32 surfaces were sampled in kitchens, bathrooms, and living areas.

RESULTS

S aureus was found in 34 of the 35 homes (97%) and was isolated from all surfaces in 1 or more homes, with the exception of the kitchen chopping board and the child training potty. MRSA was isolated from 9 of 35 homes (26%) and was found on a variety of household surfaces, including the kitchen and bathroom sinks, countertops, kitchen faucet handle, kitchen drain, dish sponge/cloth, dish towel, tub, infant high chair tray, and pet food dish. A positive correlation was indicated for the presence of a cat and the isolation of MRSA from surfaces.

CONCLUSIONS

This study has shown the presence of MRSA at hand-contact surfaces in healthy homes. This provides further evidence for the potential for infection transmission via inanimate surfaces and underscores the need for good hygiene practice in the home.

Health-care workers: source, vector, or victim of MRSA?

There is ongoing controversy about the role of health-care workers in transmission of meticillin-resistant Staphylococcus aureus (MRSA). We did a search of the literature from January, 1980, to March, 2006, to determine the likelihood of MRSA colonisation and infection in health-care workers and to assess their role in MRSA transmission. In 127 investigations, the average MRSA carriage rate among 33 318 screened health-care workers was 4.6%; 5.1% had clinical infections. Risk factors included chronic skin diseases, poor hygiene practices, and having worked in countries with endemic MRSA. Both transiently and persistently colonised health-care workers were responsible for several MRSA clusters. Transmission from personnel to patients was likely in 63 (93%) of 68 studies that undertook genotyping. MRSA eradication was achieved in 449 (88%) of 510 health-care workers. Subclinical infections and colonisation of extranasal sites were associated with persistent carriage. We discuss advantages and disadvantages of screening and eradication policies for MRSA control and give recommendations for the management of colonised health-care workers in different settings.

MRSA and the environment: implications for comprehensive control measures

Environmental contamination with methicillin-resistant Staphylococcus aureus (MRSA) is established soon after colonized or infected patients become resident. There are many studies that detail the mechanisms of spread and environmental survival of methicillin-susceptible Staphylococcus aureus (MSSA); this knowledge translates directly into the same findings for MRSA. The potential ubiquity of MRSA in a health-care setting poses challenges for decontamination. Whereas patients and medical staff are important sources for MRSA spread, the environmental burden may contribute significantly in various contexts. Effective control measures must therefore include consideration for MRSA in the environment.

Transmission of methicillin-resistant Staphylococcus aureus among hospital staff in a German trauma centre: a problem without a current solution?

Between October 2001 and February 2002, 324 healthcare workers were screened for methicillin-resistant Staphylococcus aureus (MRSA) by nose and throat swabs. A positive finding led to activation of a standardised control programme for the affected person who was immediately excluded from work. Family members of those who were MRSA-positive were offered screening free of charge. An eradication programme was carried out in the permanent carriers. MRSA was found in 17 (5.3%) healthcare workers, 11 of whom proved to be permanent carriers, and six temporarily colonised. Three children of a positive healthcare worker showed nasopharyngeal MRSA, the acquisition of which occurred within the hospital. The standardised eradication programme for carriers was successful in most cases but failed in two individuals, whereupon systemic antibiotics were used successfully. The decolonised carriers, observed for more than one year, remained MRSA negative. Isolation precautions in hospitals do not always prevent hospital staff and their families from acquiring MRSA. The identification of affected employees is difficult because in most cases only asymptomatic colonisation occurs. Screening and eradication can be complicated and costly, and for the affected employees the occupational consequences can be far-reaching as they have no guaranteed legal protection.

Computer equipment used in patient care within a multihospital system: recommendations for cleaning and disinfection

Computer hardware has been implicated as a potential reservoir for infectious agents. Leaders of a 22-hospital system, which spans North America and serves pediatric patients with orthopedic or severe burns, sought to develop recommendations for the cleaning and disinfection of computer hardware within its myriad patient care venues. A task force comprising representatives from infection control, medical affairs, information services, and outcomes management departments was formed. Following a review of the literature and of procedures within the 22 hospitals, criteria for cleaning and disinfection were established and recommendations made. The recommendations are consistent with general environmental infection control cleaning and disinfection guidelines, yet flexible enough to be applicable to the different locales, different computer and cleaning products available, and different patient populations served within this large hospital system.

Carriage of methicillin-resistant Staphylococcus aureus among hospital employees: prevalence, duration, and transmission to households

OBJECTIVE

To assess the prevalence and duration of methicillin-resistant Staphylococcus aureus (MRSA) carriage among hospital employees and transmission to their households.

DESIGN

A point-prevalence survey of MRSA carriage (nasal swabbing) of staff and patients throughout the hospital; a prevalence survey of MRSA carriage in 2 medical wards, with carriers observed to estimate carriage duration; and evaluation of transmission to MRSA-positive workers' families. All MRSA isolates were analyzed by pulsed-field gel electrophoresis. During the study, no MRSA outbreak was detected among hospitalized patients.

SETTING

A 600-bed, public tertiary-care teaching hospital near Paris.

RESULTS

Sixty MRSA carriers were identified among 965 healthcare providers (prevalence, 6.2%; CI95, 4.7%-7.7%). Prevalence was higher in staff from clinical wards than from elsewhere (9.0% vs 2.1%; P < .0001). Identity of isolates from employees and patients varied from 25% in medical wards to 100% in the long-term-care facility. MRSA carriage was identified in 14 employees from 2 medical wards (prevalence, 19.4%; CI95, 10.3%-28.5%). Prevalence depended on the length of service in these wards. Transmission to households was investigated in 10 MRSA-positive workers' families and was found in 4. All isolates from each family were identical.

CONCLUSIONS

Few data are available concerning the prevalence of MRSA carriers among hospital employees in the absence of an outbreak among patients. MRSA transmission between patients and employees likely depends on the frequency and duration of exposure to MRSA-positive patients and infection control measures employed. Frequent transmission of MRSA from colonized healthcare workers to their households was documented.

Potential impact of increased use of biocides in consumer products on prevalence of antibiotic resistance

There has recently been much controversy surrounding the increased use of antibacterial substances in a wide range of consumer products and the possibility that, as with antibiotics, indiscriminate use of biocides might contribute to the overall pattern of susceptibility in the general environment and in the clinic. Such speculation, based on the isolation of resistant mutants from in vitro monoculture experiments, is not reflected by an emergence of biocide-resistant strains in vivo. This review provides a broad coverage of the biocide and resistance literature and evaluates the potential risks, perceived from such laboratory monoculture experiments, against evidence gathered over 50 years of field studies. An explanation for the continued effectiveness of broad-spectrum biocidal agents against the decline in efficacy of therapeutic agents is provided based on the fitness costs of resistance and the ubiquity of naturally occurring substances that possess antibacterial effect. While we conclude from this review of the literature that the incorporation of antibacterial agents into a widening sphere of personal products has had little or no impact on the patterns of microbial susceptibility observed in the environment, the associated risks remain finite. The use of such products should therefore be associated with a clear demonstration of added value either to consumer health or to the product life. Hygienic products should therefore be targeted to applications for which the risks have been established.

Home hygiene: a risk approach

The need to place "prevention through hygiene" at the core of strategies for infection prevention has been emphasised by recent events. Indications are that re-evaluation of current practice and the promotion of improved hygiene in the domestic setting could have a significant impact in reducing infectious disease. If the public are to play a part however they must be properly informed. Encouraging the concept of the home as a setting in which the whole range of activities occur, including food hygiene, personal hygiene and hygiene related to medical care, provides the opportunity for a rational approach to home hygiene based on risk assessment. In the home surfaces (including hand surfaces) and other sites play an important part in the transmission of infection, especially food-borne infections. From an assessment of the frequency of occurrence of pathogens and potential pathogens at reservoirs, disseminators and hand and food contact sites together with the potential for transfer within the home, the risks of exposure can be assessed. This can be used to develop a rational approach in which effective hygiene procedures involving cleaning and disinfection as appropriate are targeted at these sites to reduce risks of cross contamination. This approach is consistent with the view that good home hygiene is not about "getting rid of household germs" but about targeting hygiene measures appropriately to reduce exposure to germs and thereby prevent cross infection. In motivating change, education programmes must take account of concerns related to antimicrobial resistance, the environment and the "health" of the immune system.

Basic microbiologic and infection control information to reduce the potential transmission of pathogens to patients via computer hardware

Computer technology from the management of individual patient medical records to the tracking of epidemiologic trends has become an essential part of all aspects of modern medicine. Consequently, computers, including bedside components, point-of-care testing equipment, and handheld computer devices, are increasingly present in patients' rooms. Recent articles have indicated that computer hardware, just as other medical equipment, may act as a reservoir for microorganisms and contribute to the transfer of pathogens to patients. This article presents basic microbiological concepts relative to infection, reviews the present literature concerning possible links between computer contamination and nosocomial colonizations and infections, discusses basic principles for the control of contamination, and provides guidelines for reducing the risk of transfer of microorganisms to susceptible patient populations.

Antibiotic resistance patterns of bacterial isolates from blood in San Francisco County, California, 1996-1999

Countywide antibiotic resistance patterns may provide additional information from that obtained from national sampling or individual hospitals. We reviewed susceptibility patterns of selected bacterial strains isolated from blood in San Francisco County from January 1996 to March 1999. We found substantial hospital-to-hospital variability in proportional resistance to antibiotics in multiple organisms. This variability was not correlated with hospital indices such as number of intensive care unit or total beds, annual admissions, or average length of stay. We also found a significant increase in methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, and proportional resistance to multiple antipseudomonal antibiotics. We describe the utility, difficulties, and limitations of countywide surveillance.

A purpose built MRSA cohort unit

The control of hospital-acquired infection, in particular methicillin-resistant Staphylococcus aureus (MRSA) remains a challenge. Our hospital has established a purpose built 11-bed cohort unit with on-site rehabilitation for care of patients colonized with MRSA, in an attempt to improve their quality of care. Prior to the opening of this unit a number of concerns were voiced and the aim of this study was to address these. First, to establish if patient cohorting reduces the likelihood of successful decolonization, second, to evaluate the risk of staff colonization, and finally to see if successful environmental control of MRSA is possible.A patient database was established detailing patient demographics, infection rates, eradication and reacquisition rates. Staff screening was performed weekly, at the start of a period of duty. Sixty environmental sites were screened before unit opening, at 48h, six weeks and at six months. There were 88 admissions in the first six months; 62 patients were colonized with MRSA, and 26 patients (10 surgical, 16 medical) had MRSA infections. Twenty-three of 88 patients (26%) were successfully decolonized, which compares favourably with an eradication rate of 20% for the rest of the hospital. Twenty staff members participated in weekly screening. Five staff members colonized with MRSA were detected and all were successfully decolonized. Environmental control was achieved with a combination of a daily detergent clean and a once weekly clean with phenolic disinfectant. Our preliminary data suggest that, despite cohorting patients colonized with MRSA, with proper education and supervised cleaning protocols, it is possible to control environmental MRSA load, successfully decolonize patients and limit the risk of staff colonization.

MRSA carriage: the relationship between community and healthcare setting. A study in an Italian hospital

From May 1997 to June 1998, all patients admitted to the study institution were screened at entry for MRSA carriage (both colonization and infection). Eighty-six MRSA carriers were identified; of these, 85 were nasal carriers. Risk factors were compared to those of 86 controls. Although the vast majority of both carriers and controls had at least one previous hospital stay, carriers were less likely than controls to be referred from a community setting, and had resided within the community for a shorter time before the current admission. The number of underlying conditions was comparable in the two groups, but those infected were more likely to have cancer than the controls. While community-acquired MRSA carriage is rare, exposure to a health care setting (particularly if repeated) within six months from the current admission, is a risk factor for MRSA carriage and introduction of the organism into an institution.

Methicillin-resistant Staphylococcus aureus in the community: new battlefronts, or are the battles lost?

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of nosocomial infections worldwide. Interpretation of community MRSA trends is problematical, in that the term is ill-defined, and related data are difficult to put into context. There are four relevant battlefronts, all of interest to risk assessment and prevention. These comprise the following: the issues relating to an increasing pool of patients with MRSA discharged from hospitals into the community; MRSA spreading to patients in nursing and residential homes; and MRSA spreading from patients and healthcare workers to others in the community. There are often difficulties in determining whether the fourth issue, MRSA arising apparently de novo in the community, is in fact due to one of these other fronts. All these battlefronts are important and not yet lost. However, we must agree on definitions and design-appropriate surveillance strategies, so that we can best inform prevention and control activities to contain these emerged or emerging problems.

Mopping up hospital infection

Hospital cleaning is a neglected component of infection control. In the UK, financial constraints have forced managers to re-evaluate domestic services and general cleaning has been reduced to the bare minimum. Services have been contracted out in some hospitals, which has further lowered standards of hygiene. Control of infection personnel believe that cleaning is important in preventing hospital-acquired infections but they do not manage domestic budgets and have failed to stop their erosion. It is difficult to defend high levels of hygiene when there is little scientific evidence to support cleaning practices. This review examines the common micro-organisms associated with hospital-acquired infection and their ability to survive in the hospital environment. It also describes studies which suggest that comprehensive cleaning disrupts the chain of infection between these organisms and patients. It is likely that restoring hygienic standards in hospitals would be a cost-effective method of controlling hospital-acquired infection. Furthermore, good cleaning is achievable whereas the enforcement of hand washing and good antibiotic prescribing are not.

Improved recognition of MRSA case clusters by the application of molecular subtyping using pulsed-field gel electrophoresis

Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly common in hospital and community populations, making the recognition of true nosocomial outbreaks more difficult. We have used pulsed-field gel electrophoresis (PFGE) with Sma I digestion to analyse retrospectively two perceived outbreaks of epidemic methicillin-resistant Staphylococcus aureus 15 (EMRSA 15) colonization. The first cluster of cases in patients and staff on a general ward (ward D) revealed three different antibiograms based on differences in ciprofloxacin and rifampicin sensitivities. All isolates typed using PFGE, which was more discriminatory than phage-typing. One PFGE banding profile labelled type 5 was predominant, but 12 isolates proved to be subtypes of type 5 and two were PFGE type 11. Four staff members carried a strain not found in patients, three carried strains found in patients and transient carriage was highlighted as a problem when screening staff. PFGE enhanced the epidemiological data and proved that the cases on this ward did not comprise one large outbreak but numerous sporadic cases and smaller clusters. In contrast, isolates from a second cluster of cases which occurred on ward F were indistinguishable using antibiograms, phage-typing and PFGE, confirming this was more likely to be a true outbreak of colonization. We conclude that PFGE usefully augments epidemiological information and allows more logical infection control decisions to be made, with better utilization of scarce resources.

Staff carriage of methicillin-resistant Staphylococcus aureus (EMRSA 15) and the home environment: a case report

A case of refractory carriage of methicillin-resistant Staphylococcus aureus (MRSA) by a nurse is described. The nurse's home environment was widely contaminated with MRSA and two family members acquired the organism. Relapse of carriage after routine anti-staphylococcal measures and three negative sets of screening specimens resulted in a hospital outbreak involving three patients. The problem was finally terminated after a co-ordinated commercial cleaning of the house, thermal disinfection of all linen and replacement of some soft furnishings.