Guidance for the decontamination of intracavity medical devices: the report of a working group of the Healthcare Infection Society.

BACKGROUND: Intracavity medical devices (ICMDs) are used in a wide variety of healthcare settings. The approach to their decontamination and the resources available also differ widely. Their potential for infection transmission is considerable. AIM: To produce a comprehensive risk assessment-based approach to the decontamination of ICMDs, accompanied by an adaptable audit tool.

Whole-Genome Sequencing Reveals the Contribution of Long-Term Carriers in Staphylococcus aureus Outbreak Investigation.

Whole-genome sequencing (WGS) makes it possible to determine the relatedness of bacterial isolates at a high resolution, thereby helping to characterize outbreaks. However, for Staphylococcus aureus, the accumulation of within-host diversity during carriage might limit the interpretation of sequencing data. In this study, we hypothesized the converse, namely, that within-host diversity can in fact be exploited to reveal the involvement of long-term carriers (LTCs) in outbreaks. We analyzed WGS data from 20 historical outbreaks and applied phylogenetic methods to assess genetic relatedness and to estimate the time to most recent common ancestor (TMRCA). The findings were compared with the routine investigation results and epidemiological evidence. Outbreaks with epidemiological evidence for an LTC source had a mean estimated TMRCA (adjusted for outbreak duration) of 243 days (95% highest posterior density interval [HPD], 143 to 343 days) compared with 55 days (95% HPD, 28 to 81 days) for outbreaks lacking epidemiological evidence for an LTC (P = 0.004). A threshold of 156 days predicted LTC involvement with a sensitivity of 0.875 and a specificity of 1. We also found 6/20 outbreaks included isolates with differing antimicrobial susceptibility profiles; however, these had only modestly increased pairwise diversity (mean 17.5 single nucleotide variants [SNVs] [95% confidence interval {CI}, 17.3 to 17.8]) compared with isolates with identical antibiograms (12.7 SNVs [95% CI, 12.5 to 12.8]) (P < 0.0001). Additionally, for 2 outbreaks, WGS identified 1 or more isolates that were genetically distinct despite having the outbreak pulsed-field gel electrophoresis (PFGE) pulsotype. The duration-adjusted TMRCA allowed the involvement of LTCs in outbreaks to be identified and could be used to decide whether screening for long-term carriage (e.g., in health care workers) is warranted. Requiring identical antibiograms to trigger investigation could miss important contributors to outbreaks.

Surveillance and management of ventriculitis following neurosurgery.

Ventriculitis is an important complication following neurosurgery and is often associated with the use of an external ventricular drain (EVD). The incidence varies from <5% to 20%, partly due to variations in the definitions used for diagnosis. Staphylococci are the most important causes but the isolation of coagulase-negative staphylococci from a cerebrospinal fluid (CSF) sample needs to be interpreted with caution as it may represent contamination. Risk factors for ventriculitis include advanced age, the duration of EVD placement, the number of manipulations and the presence of intraventricular haemorrhage. Prevention strategies increasingly focus on the implementation of a care bundle that includes aseptic technique at the time of insertion and during any manipulations, skin preparation, prophylactic antibiotics, and appropriate dressings at the site of the EVD. The use of EVDs impregnated with antimicrobial agents is increasing but, whereas some studies show that these are effective, it is not clear whether they provide added benefit when there is compliance with other measures. Antimicrobial treatment is challenging as many widely used agents do not penetrate into the CSF and causative bacteria are increasingly multidrug resistant. Often a combination of high-dose intravenous and intraventricular agents is required, especially for Gram-negative infections. Large trials in this area are challenging to conduct; therefore, to better inform preventive strategies and to optimize management of this important condition, ongoing national surveillance and pooling of data on treatment approaches and outcomes are needed.

Clinical and economic burden of surgical site infection (SSI) and predicted financial consequences of elimination of SSI from an English hospital.

BACKGROUND: Although surgical site infections (SSIs) are known to be associated with increased length of stay (LOS) and additional cost, their impact on the profitability of surgical procedures is unknown. AIM: To determine the clinical and economic burden of SSI over a two-year period and to predict the financial consequences of their elimination. METHODS: SSI surveillance and Patient Level Information and Costing System (PLICS) datasets for patients who underwent major surgical procedures at Plymouth Hospitals NHS Trust between April 2010 and March 2012 were consolidated. The main outcome measures were the attributable postoperative length of stay (LOS), cost, and impact on the margin differential (profitability) of SSI. A secondary outcome was the predicted financial consequence of eliminating all SSIs. FINDINGS: The median additional LOS attributable to SSI was 10 days [95% confidence interval (CI): 7-13 days] and a total of 4694 bed-days were lost over the two-year period. The median additional cost attributable to SSI was £5,239 (95% CI: 4,622-6,719) and the aggregate extra cost over the study period was £2,491,424. After calculating the opportunity cost of eliminating all SSIs that had occurred in the two-year period, the combined overall predicted financial benefit of doing so would have been only £694,007. For seven surgical categories, the hospital would have been financially worse off if it had successfully eliminated all SSIs. CONCLUSION: SSI causes significant clinical and economic burden. Nevertheless the current system of reimbursement provided a financial disincentive to their reduction.

Prolonged outbreak of meticillin-resistant Staphylococcus aureus in a cardiac surgery unit linked to a single colonized healthcare worker.

BACKGROUND: In low- as well as in high-prevalence settings, healthcare workers (HCWs) may be a substantial, under-recognized, reservoir of meticillin-resistant Staphylococcus aureus (MRSA) and an important potential source of transmission to patients. AIM: To report an outbreak of MRSA in a cardiac surgery unit in England over a 10-month period. METHODS: Cases were defined as patients and staff on the cardiac surgery unit from whom the outbreak strain was newly isolated between 20 May 2011 and 16 March 2012. Representative isolates from all cases were characterized by spa-typing, pulsed-field gel electrophoresis and multi-locus variable-number tandem-repeat analysis (MLVA). FINDINGS: Four patients appeared to acquire MRSA during their inpatient stay on the cardiac surgery unit. All four patients and one HCW were found to be carrying an identical epidemic (E)MRSA-15 strain (spa t032, pulsotype A, MLVA profile 16-6-3-1-1-17-1-4). No other members of staff were found to be colonized with MRSA. The colonized HCW was thought to be the source of the outbreak and was decolonized using a combination of nasal mupirocin, chlorhexidine body wash and oral rifampicin and doxycycline. CONCLUSIONS: This report highlights recent changes in the epidemiology of MRSA in England and suggests an important role for colonized HCWs in the transmission of MRSA to patients. Screening HCWs may provide an increasingly valuable strategy in managing linked hospital acquisitions and well-defined outbreaks where initial investigation does not reveal a source.

Compartmentalization of wards to cohort symptomatic patients at the beginning and end of norovirus outbreaks.

BACKGROUND: Outbreaks of norovirus can have a significant operational and financial impact on healthcare establishments. AIM: To assess whether containment of symptomatic patients in single rooms and bays at the beginning and end of norovirus outbreaks reduced the length of bed closure. METHODS: In 2007, we introduced a new strategy to limit the operational impact of hospital outbreaks of norovirus. Early in an outbreak, symptomatic patients were cohorted in single rooms or bays in an attempt to contain the outbreak without closing the entire ward. Once a ward had been closed, and as beds became available through discharges, patients were decanted into single rooms or empty bays with doors to facilitate earlier cleaning and opening of affected areas on the same ward. The impact of these changes was assessed by comparing outbreak data for two periods before and after implementation of the new strategy. FINDINGS: Prior to June 2007, 90% of outbreaks were managed by closure of an entire ward, compared with only 54% from June 2007 onwards. The duration of closure was significantly shorter for bays compared with entire wards, both before (3.5 vs 6, P = 0.0327) and after (3 vs 5, P < 0.0001) June 2007. When considering all outbreaks, there was a significant reduction in duration of closure after the change in strategy (6 vs 5, P = 0.007). CONCLUSION: Using ward compartmentalization to cohort affected patients at the beginning and end of norovirus outbreaks improved the efficiency of outbreak management and reduced operational disruption.

Decontamination of transvaginal ultrasound probes: review of national practice and need for national guidelines.

AIM: To determine the national practice of transvaginal ultrasound (TVUS) probe decontamination in English hospitals and to develop recommendations for guidance. MATERIALS AND METHODS: A literature review was undertaken to clarify best practice and evaluate methods of decontamination of TVUS probes. A questionnaire was developed to ascertain TVUS probe decontamination programmes in current use within English hospitals. This was sent to ultrasound leads of 100 English hospitals; 68 hospitals responded. RESULTS: There is a wide variation in TVUS probe decontamination across English hospitals. Although the majority of respondents (87%, 59/68) reported having clear and practical written guidelines for TVUS decontamination, the frequency, methods, and types of decontamination solutions utilized were widely variable and none meet the standards required to achieve high-level disinfection. CONCLUSION: While the decontamination of other endoluminal medical devices (e.g., flexible endoscopes) is well defined and regulated, the decontamination of TVUS probes has no such guidance. There appears to be incomplete understanding of the level of risk posed by TVUS probes, and in some cases, this has resulted in highly questionable practices regarding TVUS hygiene. There is an urgent need to develop evidence-based national guidance for TVUS probe decontamination.

Impact of preoperative screening for meticillin-resistant Staphylococcus aureus by real-time polymerase chain reaction in patients undergoing cardiac surgery.

We report a significant reduction in the number of surgical site infections (SSIs) due to meticillin-resistant Staphylococcus aureus (MRSA) in patients undergoing cardiac surgery after the introduction of preoperative screening using a same-day polymerase chain reaction (PCR) test. This was an observational cohort study set in a cardiac surgery unit based in southwest England. We studied 1462 patients admitted for cardiac surgery between October 2004 and September 2006. The IDI MRSA PCR test was used preoperatively to screen 765 patients between October 2005 and September 2006. Patients identified as carriers were treated with nasal mupirocin ointment and topical triclosan for five days, with single-dose teicoplanin instead of flucloxacillin as perioperative antibiotic prophylaxis. The rate of SSI following cardiac surgery in this group was compared to 697 patients who underwent surgery without screening between October 2004 and September 2005. After introduction of PCR screening, the overall rate of SSI fell from 3.30% to 2.22% with a significant reduction in the rate of MRSA infections (relative risk reduction: 0.77; 95% confidence interval: 0.056-0.95). PCR screening combined with suppression of MRSA at the time of cardiac surgery is feasible in routine clinical practice and is associated with a significant reduction in subsequent MRSA SSIs.

Identification of nonessential Helicobacter pylori genes using random mutagenesis and loop amplification.

Analysis of the published genome sequences of Helicobacter pylori revealed that approximately 40% of the predicted open reading frames (ORFs) were of unknown function. We have developed the random mutagenesis and loop amplification (RMLA) strategy, and used this approach both to characterize individual virulence factors and to collectively screen comparatively large numbers of H. pylori mutants to identify genes that are not essential for viability in vitro. The mini-Tn3-Km transposon was used to generate a random mutant library in H. pylori strain G27. By screening the library of mutants we were able to demonstrate that the transposon integrated randomly into the chromosome of H. pylori and that RMLA was able to identify mutants in known virulence genes (urease and catalase). To test whether this strategy could be used as a high-throughput approach for the simultaneous identification of a series of nonessential genes of H. pylori, the transposon-chromosomal junctions of a pool of mutants were amplified by inverse PCR using circular fragments of genomic DNA obtained after chromosomal DNA extracted from the pool of mutants had been digested with HindIII and self-ligated. The amplification products were radioactively labelled and hybridized to a high density macroarray membrane containing a duplicated target sequence for every gene of H. pylori strain 26695. For the positive ORFs the precise site of transposon insertion was confirmed by PCR mapping. In total 78 H. pylori genes were unambiguously identified as nonessential for viability in vitro, including 20 with orthologues of unknown function in other species and 21 which were H. pylori-specific.

Differentiation of metronidazole-sensitive and -resistant clinical isolates of Helicobacter pylori by immunoblotting with antisera to the RdxA protein.

Antimicrobial resistance in Helicobacter pylori is a serious and increasing problem, and the development of rapid, reliable methods for detecting resistance would greatly improve the selection of antibiotics used to treat gastric infection with this organism. We assessed whether detection of the RdxA protein could provide the basis for determining the susceptibility of H. pylori to metronidazole. In order to raise polyclonal antisera to RdxA, we cloned the rdxA gene from H. pylori strain 26695 into the commercial expression vector pMAL-c2, purified the resultant fusion protein by affinity chromatography, and used this recombinant RdxA preparation to immunize rabbits. We then used this specific anti-RdxA antibody to perform immunoblotting on whole bacterial cell lysates of 17 metronidazole-sensitive and 27 metronidazole-resistant clinical isolates of H. pylori. While a 24-kDa immunoreactive band corresponding to the RdxA protein was observed in all metronidazole-sensitive strains, this band was absent in 25 of 27 resistant isolates. Our results indicate that testing for the absence of the RdxA protein would identify the majority of clinical isolates that will respond poorly to metronidazole-containing eradication regimens and have implications for the development of assays capable of detecting metronidazole resistance in H. pylori.

The deplorable state of the description of the use of certified reference materials in the literature.

A detailed survey of 26 scientific journals showed that journal editors and a majority of authors of the re- c viewed papers seem unconcerned by the importance of correctly reporting their use of certified reference materials (CRMs). Only around 55% of the abstracts surveyed mention the use of CRMs described in these papers. This, however, is of key importance as the abstract of a paper is most widely available in electronic media. Many authors mentioned the use of CRMs in passing, often in incomplete form and without giving any details of the results obtained. Some are confused about the source of the reference material used, as they fail to report the type or the producer of CRMs applied. Others use materials that do not match the samples analyzed or do not see the need to use any CRM, despite the availability of suitable materials. Even in cases where correct data were given for type and producer of the CRMs, frequently the proper use and statistical evaluation are questionable. To improve this situation it is necessary that publishers should give recommendations where and how the use of CRMs should be described.

Short-term infection with Helicobacter pylori and 1 week exposure to metronidazole does not enhance gastric mutation frequency in transgenic mice.

The aim of this study was to determine whether exposure of Helicobacter pylori-infected mice to metronidazole resulted in the delivery of mutagenic compounds to the gastric epithelium via the oxygen-insensitive NADPH nitroreductase (RdxA) of H. pylori. C57BL/6 transgenic mice containing the lambda/lacI transgene were inoculated with peptone trypsin broth, H. pylori SS1 or SS1-rdxA(-), an SS1-derived mutant in rdxA. Twelve weeks after inoculation, the mice were treated for 7 days with a control solution or with the mouse equivalent of a human dose of metronidazole 1 g od. Three weeks after completion of treatment, the animals were killed and mutations in the target lacI gene assessed by a transgenic mutagenesis assay system. There was no increase in lacI mutations in cells harvested from mice infected with H. pylori and/or exposed to metronidazole. These data suggest that short-term infection with H. pylori and exposure to metronidazole does not enhance the mutation frequency in the gastric cells of mice. Whether chronic infection and/or repeated exposure to metronidazole or other nitroaromatic compounds causes genetic damage to gastric epithelial cells remains to be determined.

Evaluation of nitrofurantoin combination therapy of metronidazole-sensitive and -resistant Helicobacter pylori infections in mice.

The main objectives of this study were to determine whether the nitroreductase enzyme encoded by the rdxA gene of Helicobacter pylori was responsible for reductive activation of nitrofurantoin and whether a triple-therapy regimen with nitrofurantoin was able to eradicate metronidazole-sensitive and -resistant H. pylori infections from mice. The susceptibilities to nitrofurantoin of parent and isogenic rdxA mutant strains (three pairs), as well as a series of matched metronidazole-sensitive and -resistant strains isolated from mice (30) and patients (20), were assessed by agar dilution determination of the MIC. Groups of mice colonized with the metronidazole-sensitive H. pylori SS1 strain or a metronidazole-resistant rdxA SS1 mutant were treated with either metronidazole or nitrofurantoin as part of a triple-therapy regimen. One month after the completion of treatment the mice were sacrificed and their stomachs were cultured for H. pylori. The nitrofurantoin MICs for all strains tested were between 0.5 and 4.0 microg/ml. There was no significant difference between the susceptibility to nitrofurantoin of the parental strains and those of respective rdxA mutants or between those of matched metronidazole-sensitive and -resistant H. pylori isolates. The regimen with metronidazole eradicated infection from all eight SS1-infected mice and from one of eight mice inoculated with the rdxA mutant (P < or =0.001). The regimen with nitrofurantoin failed to eradicate infection from any of the six SS1-infected mice (P < or =0.001) and cleared infection from one of seven mice inoculated with the rdxA mutant. These results demonstrate that, despite the good in vitro activity of nitrofurantoin against H. pylori and the lack of cross-resistance between metronidazole and nitrofurantoin, eradication regimens involving nitrofurantoin are unable to eradicate either metronidazole-sensitive or -resistant H. pylori infections from mice.

Frequent association between alteration of the rdxA gene and metronidazole resistance in French and North African isolates of Helicobacter pylori.

Mutations in the rdxA gene have been associated with the acquisition of resistance to metronidazole in Helicobacter pylori. This gene encodes an NADPH nitroreductase whose expression is necessary for intracellular activation of the drug. We wished to examine whether mutations in rdxA were present in resistant H. pylori isolates infecting either French or North African patients. We determined the complete nucleotide sequences of the rdxA genes from seven French and six North African patients infected with paired resistant and sensitive strains. Genotyping by random amplified polymorphic DNA analysis confirmed the close genetic relatedness of the susceptible and resistant isolates from individual biopsies. Eight French and five North African individual resistant strains were also studied. For the French strains, an alteration in rdxA most probably implicated in resistance was found in 10 cases (seven frameshift mutations, two missense mutations, and one deletion of 211 bp). One to three putative missense mutations were identified in four cases, and a missense mutation possibly not implicated in resistance was discovered in the last case. For the North African strains, an alteration in rdxA was found in eight cases (three frameshift mutations, three missense mutations, one deletion of 6 bp, and one insertion of a variant of IS605). Two strains contained putative missense mutations, and no change was observed in rdxA of the last strain. Thus, inactivation of the rdxA gene is frequently, but not always, associated with resistance to metronidazole in French and North African clinical isolates of H. pylori. In addition, a variety of alterations of rdxA are associated with the resistant phenotype.

The role of the rdxA gene in the evolution of metronidazole resistance in Helicobacter pylori.

It was recently demonstrated that inactivation of the rdxA gene, which encodes an oxygen-insensitive NADPH nitroreductase, is associated with the development of resistance to metronidazole by Helicobacter pylori. In order to further evaluate the contribution of rdxA to metronidazole resistance, the sequence of the rdxA gene was determined for a series of metronidazole-sensitive and -resistant isolates derived from a single, metronidazole-sensitive strain using an H. pylori mouse model. These strains were cultured from the stomachs of mice experimentally infected with H. pylori strain SS1 and then treated orally with metronidazole. The sequence of the rdxA gene of all 10 sequenced metronidazole-sensitive and two (7%) of the 27 metronidazole-resistant isolates was identical to that of the parental strain. In contrast, the rdxA gene of the other 25 metronidazole-resistant isolates contained between one and three frameshift or missense mutations. This suggests that while the development of metronidazole resistance in H. pylori is frequently associated with mutational inactivation of the rdxA gene, other mechanisms of resistance are likely to exist in this bacterium.