Studies on enhanced surface disinfection and skin antisepsis using chlorhexidine and eucalyptus oil

Healthcare associated infections may arise from many sources, including patient?s own skin flora and the clinical environment, and inflict a significant burden within the health service. Adequate and effective skin antisepsis and surface disinfection are therefore essential factors in infection control. Current EPIC guidelines recommend 2 % chlorhexidine (CHG) in 70 % isopropyl alcohol (IPA) for skin antisepsis however poor penetration has been reported. Eucalyptus oil (EO) is a known permeation enhancer, producing synergistic antimicrobial activity when combined with CHG. In this current study, the antimicrobial efficacy of EO and its main constituent 1,8-cineole were assessed against a panel of clinically relevant microorganisms, alone and in combination with CHG. The superior antimicrobial efficacy of EO compared with 1,8-cineole, and synergistic effects with CHG against planktonic and biofilm cultures, confirmed its suitability for use in subsequent studies within this thesis. Impregnation of EO, CHG and IPA onto prototype hard surface disinfectant wipes demonstrated significantly improved efficacy compared with CHG/IPA wipes, with clear reductions in the time required to eliminate biofilms. Optimisation of the EO/CHG/IPA formulation resulted in the development of Euclean® wipes, with simulated-use and time kill studies confirming their ability to remove microbial surface contamination, prevent cross contamination and eliminate biofilms within 10 minutes. The employment of isothermal calorimetry provided additional information on the type and rate of antimicrobial activity possessed by Euclean® wipes. A clinical audit of the Euclean® wipes at Birmingham Children?s Hospital, Birmingham, U.K. revealed divided staff opinion, with the highest cited advantage and disadvantage concerning the odour. Finally, skin penetration and cell toxicity studies of EO/CHG biopatches and Euclean® solution developed during this study, revealed no permeation into human skin following biopatch application, and no significant toxicity. These current studies enhance the knowledge regarding EO and its potential applications.

An outbreak of Serratia marcescens on the neonatal unit:a tale of two clones

Serratia spp. are an important cause of hospital-acquired infections and outbreaks in high-risk settings. Twenty-one patients were infected or colonized over a nine-month period during 2001-2002 on a neonatal unit. Twenty-two isolates collected were examined for antibiotic susceptibility, β-lactamase production and genotype. Random-amplified polymorphic DNA polymerase chain reaction and pulsed-field gel electrophoresis revealed that two clones were present. The first clone caused invasive clinical infection in four babies, and was subsequently replaced by a non-invasive clone that affected 14 babies. Phenotypically, the two strains also differed in their prodigiosin production; the first strain was non-pigmented whereas the second strain displayed pink-red pigmentation. Clinical features suggested a difference in their pathogenicity. No environmental source was found. The outbreak terminated following enhanced compliance with infection control measures and a change of antibiotic policy. Although S. marcescens continued to be isolated occasionally for another five months of follow-up, these were sporadic isolates with distinct molecular typing patterns. © 2005 The Hospital Infection Society.

The antimicrobial efficacy of copper alloy furnishing in the clinical environment:a crossover study

Objective. To determine whether copper incorporated into hospital ward furnishings and equipment can reduce their surface microbial load. Design. A crossover study. Setting. Acute care medical ward with 19 beds at a large university hospital. Methods. Fourteen types of frequent-touch items made of copper alloy were installed in various locations on an acute care medical ward. These included door handles and push plates, toilet seats and flush handles, grab rails, light switches and pull cord toggles, sockets, overbed tables, dressing trolleys, commodes, taps, and sink fittings. Their surfaces and those of equivalent standard items on the same ward were sampled once weekly for 24 weeks. The copper and standard items were switched over after 12 weeks of sampling to reduce bias in usage patterns. The total aerobic microbial counts and the presence of indicator microorganisms were determined. Results. Eight of the 14 copper item types had microbial counts on their surfaces that were significantly lower than counts on standard materials. The other 6 copper item types had reduced microbial numbers on their surfaces, compared with microbial counts on standard items, but the reduction did not reach statistical significance. Indicator microorganisms were recovered from both types of surfaces; however, significantly fewer copper surfaces were contaminated with vancomycin-resistant enterococci, methicillin-susceptible Staphylococcus aureus, and coliforms, compared with standard surfaces. Conclusions. Copper alloys (greater than or equal to 58% copper), when incorporated into various hospital furnishings and fittings, reduce the surface microorganisms. The use of copper in combination with optimal infection-prevention strategies may therefore further reduce the risk that patients will acquire infection in healthcare environments.

Efficacy of Adding 2% (w/v) Chlorhexidine Gluconate to 70% (v/v) Isopropyl Alcohol for Skin Disinfection Prior to Peripheral Venous Cannulation

We undertook a clinical trial to compare the efficacy of 2% (w/v) chlorhexidine gluconate in 70% (v/v) isopropyl alcohol with the efficacy of 70% (v/v) isopropyl alcohol alone for skin disinfection to prevent peripheral venous catheter colonization and contamination. We found that the addition of 2% chlorhexidine gluconate reduced the number of peripheral venous catheters that were colonized or contaminated. © 2008 by The Society for Healthcare Epidemiology of America. All rights reserved.

Digluconate and isopropyl alcohol biocide formulation

Effective surface disinfection is a fundamental infection control strategy within healthcare. This study assessed the antimicrobial efficacy of novel biocide formulations comprising 5% and 2% eucalyptus oil (EO) combined with 2% chlorhexidine digluconate (CHG) and 70% isopropyl alcohol (IPA) contained within a wipe. The efficacy of this novel antimicrobial formulation to remove and eliminate methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli and Candida albicans from steel surfaces was investigated. Adpression studies of pre-contaminated wipes were also utilised to assess their potential to induce cross-contamination between hard surfaces. Furthermore, the bactericidal nature of the EO-formulation was established in addition to time-kill. The EO-containing formulations demonstrated bactericidal antimicrobial efficacy against all microorganisms and did not induce surface cross-contamination. There was no significant difference (p < 0.05) between the 5% and 2% EO formulations in their ability to remove microorganisms from steel surfaces, however both significantly (p < 0.05) removed more than the control formulations. Microbial biofilms were eliminated within 10 min (p < 0.05) when exposed to the EO formulations. Our novel EO-formulation demonstrated rapid antimicrobial efficacy for potential disinfection and elimination of microbial biofilms from hard surfaces and may therefore be a useful adjunct to current infection control strategies currently employed within healthcare facilities.

Isolation and characterisation of bacteria associated with flying insects in hospitals, with particualr emphasis on Clostridum difficile

Clostridium difficile is a bacterial healthcare-associated infection, which houseflies Musca domestica may transfer due to their synanthropic nature. The aims of this thesis were to determine the ability of M. domestica to transfer C. difficile mechanically and to collect and identify flying insects in UK hospitals and classify any associated bacteria. M. domestica exposed to independent suspensions of vegetative cells and spores of C. difficile were able to mechanically transfer the bacteria on to agar for up to 4 hours following exposure. C. difficile could be recovered from fly excreta for 96hrs and was isolated from the M. domestica alimentary canal. Also confirmed was the carriage of C. difficile by M. domestica larvae, although it was not retained in the pupae or in the adults that subsequently developed. Flying insects were collected from ultra-violet light flytraps in hospitals. Flies (order Diptera) were the most commonly identified. Chironomidae were the most common flies, Calliphora vicina were the most common synanthropic fly and ‘drain flies’ were surprisingly numerous and represent an emerging problem in hospitals. External washings and macerates of flying insects were prepared and inoculated onto a variety of agars and following incubation bacterial colonies identified by biochemical tests. A variety of flying insects, including synanthropic flies (e.g. M. domestica and C. vicina) collected from UK hospitals harboured pathogenic bacteria of different species. Enterobacteriaceae were the group of bacteria most commonly isolated, followed by Bacillus spp, Staphylococci, Clostridia, Streptococci and Micrococcus spp. This study highlights the potential for M. domestica to contribute to environmental persistence and spread of C. difficile in hospitals. Also illustrated is the potential for flying insects to contribute to environmental persistence and spread of other pathogenic bacteria in hospitals and therefore the need to implement pest control as part of infection control strategies.

Methicillin-resistant Staphylococcus aureus bacteremia:epidemiology, outcome, and laboratory characteristics in a tertiary referral center in the UK

Objective: To analyze the recent epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia in a UK tertiary referral center. Methods: We collected epidemiological and laboratory data on all cases of MRSA bacteremia from September 1, 2005 to December 31, 2007. Results: There were 195 clinically significant episodes. Most were hospital-acquired. Only one episode occurred in patients without a history of hospital admission in the previous 12 months. An intravascular device was the most common focus of infection (37%), with no identifiable source found in 35% of episodes. Twenty-eight percent of patients died within 30 days of bacteremia. Mortality was significantly higher in the absence of an identifiable focus. Failure to include an antibiotic active against MRSA in the empirical treatment was only significantly associated with death in patients showing signs of hemodynamic instability (p < 0.001). No isolates had a minimum inhibitory concentration to vancomycin above 1.5. mg/l and no heteroresistance to glycopeptide antibiotics (heteroresistant vancomycin-intermediate Staphylococcus aureus; hVISA) was detected. All isolates were sensitive to daptomycin, tigecycline, and linezolid. Conclusions: Despite improvement in infection control measures, medical devices remain the most common source of infection. Inappropriate empirical antibiotic usage is associated with a poor outcome in patients with signs of severe sepsis. Susceptibility to glycopeptides and newer antibiotics remains good. © 2010 International Society for Infectious Diseases.

A comparative study to evaluate surface microbial contamination associated with copper-containing and stainless steel pens used by nurses in the critical care unit

A clinical study was undertaken to compare the surface microbial contamination associated with pens constructed of either a copper alloy or stainless steel used by nurses on intensive care units. A significantly lower level of microbial contamination was found on the copper alloy pens. Copyright © 2011 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

The source, cost and prevention of central venous catheter-related infection

Central venous catheters have become an integral part of patient management however they are associated with many complications including infection. Despite efforts being made to reduce the incidence of such infect ions the problem continues to increase and has resource implications for the Health Service. Studies relating to the source of microorganisms causing CVC-associated infection, the cost of such infections and the efficacy of an antimicrobial catheter have been undertaken. Thirty patients who required a CVC as part of their medical management and underwent cardiac surgery had the distal tips of their catheters sampled whilst in situ. Sampling took place within 1 h of catheter placement. Bacteria were isolated from 16% of the catheter distal tips sampled in situ. The guidewires used to insert the devices were also contaminated (50%). When CVC were inserted via a protective sheath, avoiding contact with the skin. the incidence of microbial contamination was reduced. These findings suggest that despite rigorous skin disinfection and strict aseptic technique, viable microorganisms are impacted onto the distal tip of CVC during the insertion procedure. Needleless intravascular access devices have been introduced in order to reduce the incidence of need1estick injury. However, it was unclear whether such connectors would act as a portal of entry for microorganisms to CVC. The efficacy of these devices was investigated. Within the controlled laboratory environment it was demonstrated that needleless devices, when challenged with microorganisms, did not allow the passage of microbes when flu id was injected. This therefore suggested that the devices should not increase the risk of catheter colonisation. When used in clinical practice however microbial contamination of the needleless connectors was 55 % in comparison to the routinely used luer connectors (23%). The cost of infections associated with CVC was determined. Twenty patients catheterised with a CVC designed for long term use who were admitted to hospital with a presumptive diagnosis of catheter-related infection were studied. The treatment given specifically for this infection was costed. The mean cost of such an infection was £ 1781.81. Throughout the UK this may amount to £1.565.906 per annum. The cost of infections associated with CVC designed for short term use was estimated to be between 5 and 7 million pounds per annum in the UK. In an attempt to reduce both the incidence and cost of catheter- related infection antimicrobial CVC have been developed. The efficacy of a novel polyurethane CVC impregnated on both the internal and external catheter surface with the quaternary ammonium compound benzalkonium chloride was investigated. Eighty eight patients received an antimicrobial catheter and 78 patients a conventional polyurethane CVC. The anti-microbial CVC resulted in a reduction in microbial colonisation of the external and internal polymer surfaces as compared to the control device. The observed reduction in microbial colonisation with the anti-microbial CVC may decrease the likelihood of subsequent infection offering a useful approach to the prevention of catheter-related infections.

Rapid serodiagnosis of Staphylococcus aureus surgical site infection following median sternotomy

Objectives: To determine the sensitivity and specificity of a novel ELISA for the serodiagnosis of surgical site infection (SSI) due to staphylococci following median sternotomy. Methods: Twelve patients with a superficial sternal SSI and 19 with a deep sternal SSI due to Staphylococcus aureus were compared with 37 control patients who also underwent median sternotomy for cardiac surgery but exhibited no microbiological or clinical symptoms of infection. A further five patients with sternal SSI due to coagulase-negative (CoNS) staphylococci were studied. An ELISA incorporating a recently recognised exocellular short chain form of lipoteichoic acid (lipid S) recovered from CoNS, was used to determine serum levels of anti-lipid S IgG in all patient groups. Results: Serum anti-lipid S IgG titres of patients with sternal SSI due to S. aureus were significantly higher than the control patients (P<0.0001). In addition, patients with deep sternal SSI had significantly higher serum anti-lipid S IgG titres than patients with superficial sternal SSI (P=0.03). Serum anti-lipid S IgG titres of patients with sternal SSI due to CoNS were significantly higher than the control patients (P=0.001). Conclusion: The lipid S ELISA may facilitate the diagnosis of sternal SSI due to S. aureus and could also be of value with infection due to CoNS. © 2005 Published by Elsevier Ltd. on behalf of The Bristish Infection Society.

Greater CD8+ TCR heterogeneity and functional flexibility in HIV-2 compared to HIV-1 infection

Virus-specific CD8+ T cells are known to play an important role in the control of HIV infection. In this study we investigated whether there may be qualitative differences in the CD8+ T cell response in HIV-1- and HIV-2-infected individuals that contribute to the relatively efficient control of the latter infection. A molecular comparison of global TCR heterogeneity showed a more oligoclonal pattern of CD8 cells in HIV-1- than HIV-2-infected patients. This was reflected in restricted and conserved TCR usage by CD8+ T cells recognizing individual HLA-A2- and HLA-B57-restricted viral epitopes in HIV-1, with limited plasticity in their response to amino acid substitutions within these epitopes. The more diverse TCR usage observed for HIV-2-specific CD8 T cells was associated with an enhanced potential for CD8+ expansion and IFN- production on cross-recognition of variant epitopes. Our data suggest a mechanism that could account for any possible cross-protection that may be mediated by HIV-2-specific CD8+ T cells against HIV-1 infection. Furthermore, they have implications for HIV vaccine development, demonstrating an association between a polyclonal, virus-specific CD8+ T cell response and an enhanced capacity to tolerate substitutions within T cell epitopes.