Gary French

The Role Played by Contaminated Surfaces in the Transmission of Nosocomial Pathogens

Studies in the 1970s and 1980s suggested that environmental surface contamination played a negligible role in the endemic transmission of healthcare-associated infections. However, recent studies have demonstrated that several major nosocomial pathogens are shed by patients and contaminate hospital surfaces at concentrations sufficient for transmission, survive for extended periods, persist despite attempts to disinfect or remove them, and can be transferred to the hands of healthcare workers. Evidence is accumulating that contaminated surfaces make an important contribution to the epidemic and endemic transmission of Clostridium difficile, vancomycin-resistant enterococci, methicillin-resistant Staphylococcus aureus, Acinetobacter baumannii, Pseudomonas aeruginosa, and norovirus and that improved environmental decontamination contributes to the control of outbreaks. Efforts to improve environmental hygiene should include enhancing the efficacy of cleaning and disinfection and reducing the shedding of pathogens. Further high-quality studies are needed to clarify the role played by surfaces in nosocomial transmission and to determine the effectiveness of different interventions in reducing associated infection rates.

Molecular epidemiology of community-associated meticillin-resistant Staphylococcus aureus in Europe

Over the past decade, community-associated meticillin-resistant Staphylococcus aureus (MRSA) has emerged in patients without health-care contact, especially in the USA. Although data are limited, the prevalence of community-associated MRSA in Europe seems to be low but is increasing. The organism has been reported in most European countries, including The Netherlands and Nordic countries, which have low rates of health-care-associated MRSA. In Greece, rates of community-associated MRSA in some centres approach those of the USA. By contrast with North America, where the USA300 clone (ST8-IV) predominates, community-associated MRSA in Europe is characterised by clonal heterogeneity. The most common European strain is the European clone (ST80-IV), although reports of USA300 are increasing. Several community-associated MRSA clones have arisen in Europe, most notably the ST398-V pig-associated MRSA clone in The Netherlands and Denmark. An understanding of the epidemiology of community-associated MRSA is essential to guide new control initiatives to prevent these organisms from becoming endemic in Europe.

Guidelines for the management of hospital-acquired pneumonia in the UK: Report of the Working Party on Hospital-Acquired Pneumonia of the British Society for Antimicrobial Chemotherapy

Abstract These evidence-based guidelines have been produced after a systematic literature review of a range of issues involving prevention, diagnosis and treatment of hospital-acquired pneumonia (HAP). Prevention is structured into sections addressing general issues, equipment, patient procedures and the environment, whereas in treatment, the structure addresses the use of antimicrobials in prevention and treatment, adjunctive therapies and the application of clinical protocols. The sections dealing with diagnosis are presented against the clinical, radiological and microbiological diagnosis of HAP. Recommendations are also made upon the role of invasive sampling and quantitative microbiology of respiratory secretions in directing antibiotic therapy in HAP/ventilator-associated pneumonia.

The continuing crisis in antibiotic resistance

The emergence of antibiotic resistance in bacterial pathogens is an inevitable consequence of antibiotic use. Despite repeated warnings, negligent antibiotic use and poor infection-control practice have led to the continuing development of extensive resistance problems worldwide. Multidrug-resistant pathogens are now characterized by their heterogeneity, increasing virulence, resistance even to reserve agents and spread within and between hospitals and the community. Examples are glycopeptide-resistant meticillin-resistant Staphylococcus aureus (MRSA) and enterococci, extended-spectrum β-lactamase- and carbapenemase-producing coliforms, and toxin-hyperproducing Clostridium difficile. Effective national and international programmes of control to combat these problems are urgently needed. The potential for success of such coordinated efforts has been demonstrated by the recent dramatic reductions in MRSA and C. difficile infections in England.

Guidelines for UK practice for the diagnosis and management of methicillin-resistant Staphylococcus aureus (MRSA) infections presenting in the community

These guidelines have been developed by a Working Party convened on behalf of the British Society for Antimicrobial Chemotherapy. Their aim is to provide general practitioners and other community- and hospital-based healthcare professionals with pragmatic advice about when to suspect MRSA infection in the community, when and what cultures should be performed and what should be the management options, including the need for hospitalization.

Impact of rapid screening tests on acquisition of meticillin resistant Staphylococcus aureus: cluster randomised crossover trial

Objective To determine whether introducing a rapid test for meticillin resistant Staphylococcus aureus (MRSA) screening leads to a reduction in MRSA acquisition on hospital general wards. Design Cluster randomised crossover trial. Setting Medical, surgical, elderly care, and oncology wards of a London teaching hospital on two sites. Main outcome measure MRSA acquisition rate (proportion of patients negative for MRSA who became MRSA positive). Participants All patients admitted to the study wards who were MRSA negative on admission and screened for MRSA on discharge. Intervention Rapid polymerase chain reaction based screening test for MRSA compared with conventional culture. Results Of 9608 patients admitted to study wards, 8374 met entry criteria and 6888 had full data (82.3%); 3335 in the control arm and 3553 in the rapid test arm. The overall MRSA carriage rate on admission was 6.7%. Rapid tests led to a reduction in median reporting time from admission, from 46 to 22 hours (P<0.001). Rapid testing also reduced the number of inappropriate pre-emptive isolation days between the control and intervention arms (399 v 277, P<0.001). This was not seen in other measurements of resource use. MRSA was acquired by 108 (3.2%) patients in the control arm and 99 (2.8%) in the intervention arm. When predefined confounding factors were taken into account the adjusted odds ratio was 0.91 (95% confidence interval 0.61 to 1.234). Rates of MRSA transmission, wound infection, and bacteraemia were not statistically different between the two arms. Conclusion A rapid test for MRSA led to the quick receipt of results and had an impact on bed usage. No evidence was found of a significant reduction in MRSA acquisition and on these data it is unlikely that the increased costs of rapid tests can be justified compared with alternative control measures against MRSA. Trial registration Clinical controlled trials ISRCTN75590122.

Incidence and mechanisms of resistance to the combination of amoxicillin and clavulanic acid in Escherichia coli.

Among Escherichia coli organisms isolated at St. Thomass Hospital during the years 1990 to 1994, the frequency of resistance to amoxicillin-clavulanic acid (tested by disk diffusion in a ratio of 2:1) remained constant at about 5% of patient isolates (10 to 15% of the 41 to 45% that were amoxicillin resistant). Mechanisms of increased resistance were determined for 72 consecutively collected such amoxicillin-clavulanic acid-resistant isolates. MICs of the combination were 16-8 micrograms/ml for 51 (71%) of these and > or = 32-16 micrograms/ml for the remainder. The predominant mechanism was hyperproduction of enzymes isoelectrically cofocusing with TEM-1 (beta-lactamase activities, > 200 nmol of nitrocefin hydrolyzed per min per mg of protein) which was found in 44 isolates (61%); two isolates produced smaller amounts (approximately 150 nmol/min/mg) of such enzymes, and two isolates hyperproduced enzymes cofocusing with TEM-2. Eleven isolates produced enzymes cofocusing with OXA-1 beta-lactamase, which has previously been associated with resistance to amoxicillin-clavulanic acid. Ten isolates produced increased amounts of chromosomal beta-lactamase, and four of these additionally produced TEM-1 or TEM-2. Three isolates produced inhibitor-resistant TEM-group enzymes. In one of the enzymes (pI, 5.4), the amino acid sequence change was Met-67-->Val, and thus the enzyme is identical to TEM-34. Another (pI, 5.4) had the substitution Met-67-->Ile and is identical to IRT-I67, which we propose now be given the designation TEM-40. The third (pI, 5.2) had the substitution Arg-241-->Thr; this enzyme has not been reported previously and should be called TEM-41. The rarity and diversity of inhibitor-resistant TEM-group enzymes suggest that they are the result of spontaneous mutations that have not yet spread.

Survival of Nosocomial Bacteria and Spores on Surfaces and Inactivation by Hydrogen Peroxide Vapor

ABSTRACT With inocula of 6 to 7 log10 CFU, most vegetative bacteria and spores tested survived on surfaces for more than 5 weeks, but all were inactivated within 90 min of exposure to hydrogen peroxide vapor in a 100-m3 test room even in the presence of 0.3% bovine serum albumin to simulate biological soiling.

Community-associated meticillin-resistant Staphylococcus aureus strains as a cause of healthcare-associated infection

Community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) was first noticed as a cause of infection in community-based individuals without healthcare contact. As the global epidemic of CA-MRSA has continued, CA-MRSA strain types have begun to emerge as a cause of healthcare-associated infections (HAIs) and hospital outbreaks have occurred worldwide. In areas where CA-MRSA clones have become established with high prevalence, for example USA300 (ST8-IV) in the USA, CA-MRSA are beginning to supplant or overtake traditional healthcare-associated MRSA strains as causes of HAI. The emergence of CA-MRSA as a cause of HAI puts a wider group of hospitalised patients, healthcare workers and their community contacts potentially at risk of MRSA infection. It also exposes CA-MRSA strains to the selective pressure of antibiotic use in hospitals, potentially resulting in increased antibiotic resistance, challenges traditional definitions of CA-MRSA and hampers control efforts due to the constant re-introduction of MRSA from an emerging community reservoir. There is thus an urgent need to clarify the definitions, prevalence and epidemiology of CA-MRSA and to develop systems for the identification and control of these organisms in the community, in hospitals and other healthcare facilities, and at the community-hospital interface.

Evidence that contaminated surfaces contribute to the transmission of hospital pathogens and an overview of strategies to address contaminated surfaces in hospital settings.

Evidence that contaminated surfaces contribute to the transmission of hospital pathogens comes from studies modeling transmission routes, microbiologic studies, observational epidemiologic studies, intervention studies, and outbreak reports. This review presents evidence that contaminated surfaces contribute to transmission and discusses the various strategies currently available to address environmental contamination in hospitals.