Collecting the data but missing the point: validity of hand hygiene audit data.

BACKGROUND: Monitoring of hand hygiene compliance (HHC) by observation has been used in healthcare for more than a decade to provide assurance of infection control practice. The validity of this information is rarely tested. AIM: To examine the process and validity of collecting and reporting HHC data based on direct observation of compliance. METHODS: Five years of HHC data routinely collected in one large National Health Service hospital trust were examined. The data collection process was reviewed by survey and interview of the auditors. HHC data collected for other research purposes undertaken during this period were compared with the organizational data set. FINDINGS: After an initial increase, the reported HHC remained unchanged close to its intended target throughout this period. Examination of the data collection process revealed changes, including local interpretations of the data collection system, which invalidated the results. A minority of auditors had received formal training in observation and feedback of results. CONCLUSION: Whereas observation of HHC is the current gold standard, unless data collection definitions and methods are unambiguous, published, carefully supervised, and regularly monitored, variations may occur which affect the validity of the data. If the purpose of HHC monitoring is to improve practice and minimize transmission of infection, then a focus on progressively improving performance rather than on achieving a target may offer greater opportunities to achieve this.

The role of glutamate dehydrogenase for the detection of Clostridium difficile in faecal samples: a meta-analysis.

Clostridium difficile causes a serious, occasionally fatal, hospital-acquired infection. The laboratory diagnosis of C. difficile infection (CDI) needs to be accurate to ensure optimal patient management, infection control and reliable surveillance. Commercial enzyme-linked immunosorbent assays for C. difficile toxins have poor sensitivity when compared with cell culture cytotoxin assay (CTA) and toxigenic culture (TC). We performed a meta-analysis of the role of glutamate dehydrogenase (GDH) in diagnosis of CDI. We analysed 21 papers, of which eight were excluded. We included publications of original research that used a 'gold standard' reference test (either CTA or TC). We also included publications that used culture without toxin testing of the isolate as a reference test even though this is not recognised as a gold standard. Exclusion criteria were failure to use a gold standard reference test and where the index test was used as the gold standard. Significant heterogeneity between study results justified the summary receiver operating characteristic (SROC) analysis. The meta-analysis demonstrated high diagnostic accuracy of GDH for the presence of C. difficile in faeces; when compared with culture it achieved a sensitivity and specificity of >90%. The SROC plot confirmed this finding. As a surrogate for toxigenic strains the GDH yields a specificity of 80-100% with a false positivity rate of ∼20%, as it detects toxigenic and non-toxigenic strains of the organism. However, GDH test has high sensitivity and negative predictive value and would be a powerful test in a dual testing algorithm when combined with a test to detect toxin.

Performance of ultramicrofibre cleaning technology with or without addition of a novel copper-based biocide.

This study compared the bacterial removal performance of ultramicrofibre cloths and mops (UMF) moistened with water (UMF+water), with those moistened with a novel copper-based biocide (UMF+CuWB50, 300ppm) in several working hospital environments, specifically accident and emergency (A&E) and three other wards. A total of 13 defined sampling sites (10 sites per ward) were sampled in order to retrieve, culture, and enumerate total viable (bacterial) counts (TVC) for each site. We sampled 1h before, and 1 and 4h after, cleaning three times per week. The trial ran for 7 weeks. Two wards were cleaned with UMF+water for 3 weeks, and UMF+CuWB50 for 4 weeks. The reverse applied to the other two wards in a cross-over design fashion, to eliminate ward- and time-specific bias. Multivariate statistical analyses were used to establish extent and significance of any perceived differences, and to eliminate the effects of potential confounders. Cleaning with UMF+water reduced TVC on the test surfaces by 30%, whereas cleaning with TVC+CuWB50 reduced TVC by 56%. CuWB50 had two separate effects; a direct antibacterial effect (evident shortly after cleaning), and a residual antibacterial effect that lasted approximately 2 weeks. The residual effect requires regular application of CuWB50 if it is to persist. This 'real life' hospital implementation study demonstrates encouraging microbiological cleaning performance for UMF, which is further enhanced with CuWB50.

Removing bacteria from hospital surfaces: a laboratory comparison of ultramicrofibre and standard cloths.

We compared the ability of ultramicrofibre-woven cloths with conventional cloths moistened with water only, for their ability to remove several types of organisms relevant to hospital-acquired infections from a variety of surfaces in hospitals. We showed that ultramicrofibre cloths consistently outperformed conventional cloths in their decontamination ability, across all surfaces, and irrespective of whether the bacteria were coated on to the surfaces with phosphate-buffered saline (PBS) or PBS containing horse serum to simulate real-life soiling. The ability of the cloths to remove bacteria from surfaces was assessed by contact plating and colony formation, and by swabbing and measurement of ATP bioluminescence. The results suggest potential for use of ultramicrofibre in healthcare environments. Further studies are required, however, to define accurately how these cloths, which are designed to be used without detergent or biocides, might be capable of safe and effective deployment and recycling in the healthcare environment.

Influenza A and respiratory syncytial virus hospital burden in young children in East London.

Epidemiological studies have demonstrated high hospitalization rates attributable to influenza and RSV in children aged 6 months and those aged <12 months, respectively (43 and 92.5/10 000 person-months, respectively). In conclusion, these high paediatric RSV and influenza incidence rates can be used to inform UK policy on childhood influenza immunization and subsequent RSV immunization in the future.

Impact of rapid molecular screening for meticillin-resistant Staphylococcus aureus in surgical wards.

BACKGROUND: This study aimed to establish the feasibility and cost-effectiveness of rapid molecular screening for hospital-acquired meticillin-resistant Staphylococcus aureus (MRSA) in surgical patients within a teaching hospital. METHODS: In 2006, nasal swabs were obtained before surgery from all patients undergoing elective and emergency procedures, and screened for MRSA using a rapid molecular technique. MRSA-positive patients were started on suppression therapy of mupirocin nasal ointment (2 per cent) and undiluted chlorhexidine gluconate bodywash. RESULTS: A total of 18,810 samples were processed, of which 850 (4.5 per cent) were MRSA positive. In comparison to the annual mean for the preceding 6 years, MRSA bacteraemia fell by 38.5 per cent (P < 0.001), and MRSA wound isolates fell by 12.7 per cent (P = 0.031). The reduction in MRSA bacteraemia and wound infection was equivalent to a saving of 3.78 beds per year (276,220 pounds sterling), compared with the annual mean for the preceding 6 years. The cost of screening was 302,500 pounds sterling, making a net loss of 26,280 pounds sterling. Compared with 2005, however, there was a net saving of 545,486 pounds sterling. CONCLUSION: Rapid MRSA screening of all surgical admissions resulted in a significant reduction in staphylococcal bacteraemia during the screening period, although a causal link cannot be established.

Vitreous relapse following primary chemotherapy for retinoblastoma: is adjuvant diode laser a risk factor?

AIMS: To evaluate rates of vitreous relapse among retinoblastoma patients treated with primary chemotherapy and assess diode laser as a potential risk factor for relapse. METHODS: Retrospective review of all patients treated with primary chemotherapy at a large ocular oncology centre. Eyes that developed vitreous relapse were coded with regard to Reese-Ellsworth Group, laterality, time to relapse, type of relapse (vitreous base or non-vitreous base relapse), treatments used (including adjuvant diode laser), and ocular preservation. Individual tumour foci treated with laser hyperthermia were also coded for laser parameters including power settings, number of treatments, and concomitant administration of systemic chemotherapy (chemothermotherapy). RESULTS: 15 of 106 eyes (14.15%) developed vitreous relapse over a 6 year period. Mean time to relapse was 7.2 months after chemotherapy was completed. Five cases (33%) were of the vitreous base variety. Ocular salvage was attempted in 11 cases using a variety of methods; one patient was lost to follow up. Six of the remaining 10 eyes (60%) were salvaged. Eight of 38 eyes (21%) treated with systemic chemotherapy and laser hyperthermia developed vitreous relapse compared with seven of 68 eyes (10%) treated with primary chemotherapy alone (p<0.005). Laser settings, number of hyperthermia treatments, and the concomitant use of systemic chemotherapy (chemothermotherapy) were not associated with higher rates of vitreous relapse. CONCLUSION: Nearly one in seven eyes with retinoblastoma treated with primary chemotherapy may develop vitreous relapse. The administration of diode laser hyperthermia appears to increase this risk. Despite additional therapy a number of these eyes succumb to enucleation.

Competition between methicillin-sensitive and -resistant Staphylococcus aureus in the anterior nares.

Colonization of the anterior nares with Staphylococcus aureus has been shown to be a risk factor for infection. The purpose of this study was to test the hypothesis that methicillin-resistant strains of S. aureus (MRSA) compete with methicillin-sensitive (MSSA) strains for colonization of the anterior nares. As part of the local National Health Service trust MRSA infection control strategy, patients who have been in a healthcare institution in the last year are routinely sampled and tested for MRSA colonization at the time of hospital admission. The sampling and testing methods were modified for the six-month period of this study to allow the detection of both MSSA and MRSA/MSSA co-colonization. MRSA alone was carried by 56 (8%) of 680 patients, MSSA alone by 115 patients (17%), 505 patients (74.3%) carried neither, and four patients (0.6%) carried both MRSA and MSSA. The deviance between the observed number of co-colonized swabs and that expected under the null hypothesis of no competition between MSSA and MRSA was significant (P=0.02, Fisher's exact test). The statistical approach is unaffected by the confounding effect of factors that affect the relative frequencies of MRSA or MSSA colonization. When logistic regression was used to estimate the extent of competition, controlling for effects of age and sex, we estimated a protective efficacy of MSSA colonization in the prevention of MRSA colonization of 78% (95% CI 29-99%). Results from this cross-sectional study support the hypothesis that MRSA and MSSA compete for colonization space, and provides an estimate of the extent to which MSSA interferes with MRSA colonization.

Comparative epidemiology of scrapie outbreaks in individual sheep flocks.

Data recording the course of scrapie outbreaks in 4 sheep flocks (2 in Cheviot sheep and 2 in Suffolks) are compared. For each outbreak the data on scrapie incidence and sheep demography and pedigrees cover periods of years or decades. A key finding is that the incidence of clinical cases peaks in sheep 2-3 years old, despite very different forces-of-infection. This is consistent with age-specific susceptibility of sheep to scrapie, as has been reported for cattle to bovine spongiform encephalopathy and for humans to variant Creutzfeldt-Jakob disease. Scrapie incidence was higher in ewes than rams and at certain times of years, though these effects were not consistent between flocks. There was no evidence for high levels of vertical transmission.

Population dynamics of a scrapie outbreak.

A detailed analysis of a scrapie outbreak in a flock of Cheviot sheep is described. A total of 33 cases of 1473 sheep born to the flock were reported between 1985 and 1994. The epidemiology of scrapie can only be understood with reference to sheep demography, the population genetics of susceptibility to scrapie, pathogenesis during a long incubation period, and the rate of transmission (by both horizontal and vertical routes), all of which interact in complex ways. In recent work a mathematical model incorporating these elements was developed and successfully reproduced key features of an earlier outbreak of scrapie in this flock. Here an application of the model to the second outbreak is described. The model accurately reproduces observed allele frequencies and total numbers of susceptible animals remaining at the end of the outbreak. A major difference between the two outbreaks is the very much lower force of infection in the second outbreak. This provided additional information which suggested two ways in which our existing assumptions be refined; firstly, older animals have reduced susceptibility to scrapie and secondly, homozygous and heterozygous susceptibles have different incubation periods.

Trypanosoma evansi in Indonesian buffaloes: evaluation of simple models of natural immunity to infection.

Deterministic models were employed to investigate the biology of Trypanosoma evansi infection in the Indonesian buffalo. Models were fitted to two age-structured data sets of infection. The Susceptible-Infected-Susceptible (SIS) model was the best supported description of this infection, although the results of the analysis depended on the serological test used; the Tr7 Ag-ELISA was judged the most reliable indicator of infection. Estimated forces of infection increase with age from 1.2 to 2.0 acquisitions per buffalo per year. The buffaloes would clear infection in an estimated mean time period of 16.8 months (95% CIs: 12.5-25.9 months) since acquisition, either by drug treatment by owners or self-cure. A general discussion on the role of immunity in protozoan infections includes consideration that the fitted SIS model would be consistent with strain-specific immunity. The model may become a useful tool for the evaluation of control programmes.

Mathematical modelling of infection and disease due to Neisseria meningitidis and Neisseria lactamica.

BACKGROUND: Invasive meningococcal disease, due to Neisseria meningitidis, is an important cause of morbidity and mortality in young children and adolescents. Nasopharyngeal carriage of meningococci (MC), is most prevalent in young adults whereas carriage of Neisseria lactamica (LC), a related non-pathogenic organism, is most prevalent in young children. The objective of this study was to use modelling techniques to test hypotheses on the processes that govern the incidence of meningococcal disease (MD). METHODS: Deterministic compartmental models were fitted to age structured data sets of MC, LC and MD. RESULTS: The model most consistent with the available data sets is one where LC inhibits MC, an inhibition that lasts for a mean of 4.7 years. The hypothesis that LC also acts as a natural immunogen against MD was consistent with this model. The second peak of MD observed among adolescents could be due to the peak in the acquisition of MC in this age group. CONCLUSIONS: The role of LC as a natural immunogen against asymptomatic and symptomatic meningococcal infection was consistent with available field data. If the introduction of novel meningococcal vaccines into a population changes the prevalence of MC or LC, this could have a substantial impact on the effectiveness of immunization programmes. This paper demonstrates the potential utility of modelling to estimate these effects.

The Hib immunization programme in the Oxford region: an analysis of the impact of vaccine administration on the incidence of disease.

In May 1991 an immunization programme against Haemophilus influenzae type b (Hib) infection began within the Oxford region. We validate a deterministic mathematical model of Hib by comparison with the incidence of disease in the Oxford region, 1985-97. The comparison of model results with observed outcome allows an exploration of some of the poorly understood properties of the immunization programme. Model results and observed incidence are consistent with a vaccine that blocks the acquisition of carriage. Similarly, the data suggest that factors other than experience of Hib carriage are likely to have generated acquired immunity to Hib disease prior to the introduction of vaccination. Hence it is unlikely that waning of vaccine-derived protection will result in a resurgence of disease. The inclusion in the immunization schedule of a booster dose, as used in other countries, would have provided very little extra benefit.

Mathematical models of Haemophilus influenzae type b.

A review of empirical studies and the development of a simple theoretical framework are used to explore the relationship between Haemophilus influenzae type b (Hib) carriage and disease within populations. The models emphasize the distinction between asymptomatic and symptomatic infection. Maximum likelihood methods are used to estimate parameter values of the models and to evaluate whether models of infection and disease are satisfactory. The low incidence of carriage suggests that persistence of infection is only compatible with the absence of acquired immunity to asymptomatic infection. The slight decline in carriage rates amongst adults is compatible with acquired immunity, but could be a consequence of reduced contacts. The low rate of disease observed in adulthood cannot be explained if protection from disease is a product of previous detectable exposure to Hib alone. We estimate an R0 of 3.3 for Hib in developed countries, which suggests that current immunization programmes may eliminate the infection. Analysis of the disease data set suggests the absence of maternal immunity and increased susceptibility to disease in the oldest age classes.