Efficacy of a standard meticillin-resistant Staphylococcus aureus decolonisation protocol in routine clinical practice

Summary

Decolonisation may reduce the risk of meticillin-resistant Staphylococcus aureus (MRSA) infection in individual carriers and prevent transmission to other patients. The aims of this prospective cohort study were to determine the long-term efficacy of a standardised decolonisation regimen and to identify factors associated with failure. Patients colonised with MRSA underwent decolonisation, which was considered to be successful if there was no growth in three consecutive sets of site-specific screening swabs obtained weekly post treatment. If patients were successfully decolonised, follow-up cultures were performed 6 and 12 months later. Of 137 patients enrolled, 79 (58%) were successfully decolonised. Of these 79, 53 (67%) and 44 (56%) remained decolonised at 6 and 12 months respectively. Therefore only 44/137 (32%) patients who completed decolonisation were MRSA negative 12 months later. Outcome was not associated with a particular strain of MRSA. Successful decolonisation was less likely in patients colonised with a mupirocin-resistant isolate (adjusted odds ratio: 0.08; 95% confidence interval: 0.02–0.30), in patients with throat colonisation (0.22; 0.07–0.68) and in patients aged >80 years (0.30; 0.10–0.93) compared with those aged 60–80 years. These findings suggest that although initially successful in some cases, the protocol used did not result in long-term clearance of MRSA carriage for most patients.

Cluster randomised controlled trial of an infection control education and training intervention programme focusing on meticillin-resistant Staphylococcus aureus in nursing homes for older people

The aim of this cluster randomised controlled trial was to test the impact of an infection control education and training programme on meticillin-resistant Staphylococcus aureus (MRSA) prevalence in nursing homes. Nursing homes were randomised to intervention (infection control education and training programme; N¼16) or control (usual practice continued; N¼16). Staff in intervention homes were educated and trained (0, 3 and 6 months) in the principles and implementation of good infection control practice with infection control audits conducted in all sites (0, 3, 6 and 12 months) to assess compliance with good practice. Audit scores were fed back to nursing home managers in intervention homes, together with a written report indicating where practice could be improved. Nasal swabs were taken from all consenting residents and staff at 0, 3, 6 and 12 months. The primary outcome was MRSA prevalence in residents and staff, and the secondary outcome was a change in infection control audit scores. In all, 793 residents and 338 staff were recruited at baseline. MRSA prevalence did not change during the study in residents or staff. The relative risk of a resident being colonised with MRSA in an intervention home compared with a control home at 12 months was 0.99 (95% con?dence interval: 0.69, 1.42) after adjustment for clustering. Mean infection control audit scores were signi?cantly higher in the intervention homes (82%) compared with the control homes (64%) at 12 months (P<0.0001). Consideration should be given to other approaches which may help to reduce MRSA in this setting.

No association between routinely recorded infections in early life and subsequent risk of childhood-onset Type 1 diabetes: a matched case-control study using the UK General Practice Research Database

Aims To determine whether children with infections in early life (recorded routinely in general practice) have a reduced risk of Type 1 diabetes, as would be expected from the hygiene hypothesis.

Staphylococcus epidermidis device-related infections: pathogenesis and clinical management

Staphylococcus epidermidis, the most frequently isolated coagulase-negative staphylococcus, is the leading cause of infection related to implanted medical devices (IMDs). This is directly related to its capability to establish multilayered, highly structured biofilms on artificial surfaces. At present, conventional systemic therapies using standard antimicrobial agents represent the main strategy to treat and prevent medical device-associated infections. However, device-related infections are notoriously difficult to treat and bacteria within biofilm communities on the surface of IMDs frequently outlive treatment, and removal of the medical device is often required for successful therapy. Importantly, major advances in this research area have been made, leading to a greater understanding of the complexities of biofilm formation of S. epidermidis and resulting in significant developments in the treatment and prevention of infections related to this member of the coagulase-negative group of staphylococci. This review will examine the pathogenesis of the clinically significant S. epidermidis and provide an overview of the conventional and emerging antibiofilm approaches in the management of medical device-associated infections related to this important nosocomial pathogen.

Tackling antibiotic resistance: a dose of common antisense?

Resistance to antimicrobial agents undermines our ability to treat bacterial infections. It attracts intense media and political interest and impacts on personal health and costs to health infrastructures. Bacteria have developed resistance to all licensed antibacterial agents, and their ability to become resistant to unlicensed agents is often demonstrated during the development process. Conventional approaches to antimicrobial development, involving modification of existing agents or production of synthetic derivatives, are unlikely to deliver the range or type of drugs that will be needed to meet all future requirements. Although many companies are seeking novel targets, further radical approaches to both antimicrobial design and the reversal of resistance are now urgently required. In this article, we discuss ‘antisense’ (or ‘antigene’) strategies to inhibit resistance mechanisms at the genetic level. These offer an innovative approach to a global problem and could be used to restore the efficacy of clinically proven agents. Moreover, this strategy has the potential to overcome critical resistances, not only in the so-called ‘superbugs’ (methicillin-resistant Staphylococcus aureus, glycopeptide-resistant enterococci and multidrug-resistant strains of Acinetobacter baumannii, and Pseudomonas aeruginosa), but in resistant strains of any bacterial species.

Infections and vaccinations as risk factors for childhood type I (insulin-dependent) diabetes mellitus: a multicentre case-control investigation.

AIMS/HYPOTHESIS: To determine if vaccinations and infections are associated with the subsequent risk of Type I (insulin-dependent) diabetes mellitus in childhood. METHOD: Seven centres in Europe with access to population-based registers of children with Type I diabetes diagnosed under 15 years of age participated in a case-control study of environmental risk factors. Control children were chosen at random in each centre either from population registers or from schools and policlinics. Data on maternal and neonatal infections, common childhood infections and vaccinations were obtained for 900 cases and 2302 control children from hospital and clinic records and from parental responses to a questionnaire or interview. RESULTS: Infections early in the child's life noted in the hospital record were found to be associated with an increased risk of diabetes, although the odds ratio of 1.61 (95% confidence limits 1.11, 2.33) was significant only after adjustment for confounding variables. None of the common childhood infectious diseases was found to be associated with diabetes and neither was there evidence that any common childhood vaccination modified the risk of diabetes. Pre-school day-care attendance, a proxy measure for total infectious disease exposure in early childhood, was found, however, to be inversely associated with diabetes, with a pooled odds ratio of 0.59 (95% confidence limits 0.46, 0.76) after adjustment for confounding variables. CONCLUSION/INTERPRETATION: It seems likely that the explanation for these contrasting findings of an increased risk associated with perinatal infections coupled with a protective effect of pre-school day care lies in the age-dependent modifying influence of infections on the developing immune system.

Lack of horizontal gene transfer of methicillin-resitance genetic determinants from PBP2a-positive, coagulase-negative Staphylococci to methicillin-sensitive Staphylococcus aureus using transcutaneous electric nerve stimulation (TENS),

Previous research shows that approximately half of the coagulase-negative staphylococci (CNS) isolated from patients in the intensive care unit (ICU) at Belfast City Hospital were resistant to methicillin. The presence of this relatively high proportion of methicillin-resistance genetic material gives rise to speculation that these organisms may act as potential reservoirs of methicillinresistance genetic material to methicillin-sensitive Staphylococcus aureus (MSSA). Mechanisms of horizontal gene transfer from PBP2a-positive CNS to MSSA, potentially transforming MSSA to MRSA, aided by electroporation-type activities such as transcutaneous electrical nerve stimulation (TENS), should be considered. Methicillin-resistant CNS (MR-CNS) isolates are collected over a two-month period from a variety of clinical specimen types, particularly wound swabs. The species of all isolates are confirmed, as well as their resistance to oxacillin by standard disc diffusion assays. In addition, MSSA isolates are collected over the same period and confirmed as PBP2a-negative. Electroporation experiments are designed to mimic the time/voltage combinations used commonly in the clinical application of TENS. No transformed MRSA were isolated and all viable S. aureus cells remained susceptible to oxacillin and PBP2a-negative. Experiments using MSSA pre-exposed to sublethal concentrations of oxacillin (0.25 µg/mL) showed no evidence of methicillin gene transfer and the generation of an MRSA. The study showed no evidence of horizontal transfer of methicillin resistance genetic material from MR-CNS to MSSA. These data support the belief that TENS and the associated time/voltage combinations used do not increase conjugational transposons or facilitate horizontal gene transfer from MR-CNS to MSSA.