Peter J. Jenks

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.

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.

Helicobacter pylori mutants defective in RuvC Holliday junction resolvase display reduced macrophage survival and spontaneous clearance from the murine gastric mucosa

ABSTRACT Homologous recombination contributes to the extraordinary genetic diversity of Helicobacter pylori and may be critical for surface antigen expression and adaptation to environmental challenges within the stomach. We generated isogenic, nonpolar H. pylori ruvC mutants to investigate the function of RuvC, a Holliday junction endonuclease that resolves recombinant joints into nicked duplex products. Inactivation of ruvC reduced the frequency of homologous recombination of H. pylori between 17- and 45-fold and increased sensitivity to DNA-damaging agents and the antimicrobial agents levofloxacin and metronidazole. The H. pylori ruvC mutants were more susceptible to oxidative stress and exhibited reduced survival within macrophages. Experiments with the H. pylori SS1 mouse model revealed that the 50% infective dose of the ruvC mutant was approximately 100-fold higher than that of the wild-type SS1 strain. Although the ruvC mutant was able to establish colonization with bacterial loads that were initially similar to those of the parental SS1 strain, infection was spontaneously cleared from the murine gastric mucosa over periods that varied from 36 to 67 days. These results demonstrate that, in this infection model, RuvC is essential for continued survival of H. pylori in vivo and raises the possibility that inactivation of ruvC might be of value in an attenuated vaccine strain.

Frequent Association between Alteration of the rdxA Gene and Metronidazole Resistance in French and North African Isolates of Helicobacter pylori

ABSTRACT 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 inrdxA 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.

Causes of failure of eradication of Helicobacter pylori.

Eradication of Helicobacter pylori from the gastric and duodenal mucosa of infected patients is the most important goal in the management of peptic ulcer disease and other conditions associated with H pylori .1 The survival capabilities of H pylori in the stomach make it difficult to eradicate, and effective treatment requires multidrug regimens consisting of two antibiotics (usually selected from clarithromycin, metronidazole, amoxicillin, and tetracycline), combined with acid suppressants and bismuth compounds.2 A significant proportion of patients do not respond to treatment, and adverse treatment outcome is associated with advanced age, smoking, high intragastric bacterial load before treatment, bacterial genotype, and host genetic polymorphisms of the cytochrome-P450 isoenzymes that are specifically involved in the metabolism of proton pump inhibitors.3 Adherence to the drug regimen is particularly important for successful eradication of infection and can be improved by education of patients and programmes to improve compliance.4 But as in many other infectious diseases, antibiotic resistance is the major cause of treatment failure. Meta-analyses have established beyond doubt that resistance to either the macrolide or 5-nitroimidazole component …

Comparison of Automated Processing of Flocked Swabs with Manual Processing of Fiber Swabs for Detection of Nasal Carriage of Staphylococcus aureus

ABSTRACT The sensitivity of automated culture of Staphylococcus aureus from flocked swabs versus that of manual culture of fiber swabs was prospectively compared using nasal swabs from 867 patients. Automated culture from flocked swabs significantly increased the detection rate, by 13.1% for direct culture and 10.2% for enrichment culture.

Evaluation of Nitrofurantoin Combination Therapy of Metronidazole-Sensitive and -Resistant Helicobacter pylori Infections in Mice

ABSTRACT The main objectives of this study were to determine whether the nitroreductase enzyme encoded by the rdxA gene ofHelicobacter 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 isogenicrdxA 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 μg/ml. There was no significant difference between the susceptibility to nitrofurantoin of the parental strains and those of respectiverdxA 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 therdxA mutant (P ≤ 0.001). The regimen with nitrofurantoin failed to eradicate infection from any of the six SS1-infected mice (P ≤ 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.

Differentiation of Metronidazole-Sensitive and -Resistant Clinical Isolates of Helicobacter pylori by Immunoblotting with Antisera to the RdxA Protein

ABSTRACT 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.

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.

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.