The antibacterial activity of acetic acid against biofilm-producing pathogens of relevance to burns patients

Introduction: Localised infections, and burn wound sepsis are key concerns in the treatment of burns patients, and prevention of colonisation largely relies on biocides. Acetic acid has been shown to have good antibacterial activity against various planktonic organisms, however data is limited on efficacy, and few studies have been performed on biofilms. Objectives: We sought to investigate the antibacterial activity of acetic acid against important burn wound colonising organisms growing planktonically and as biofilms. Methods: Laboratory experiments were performed to test the ability of acetic acid to inhibit growth of pathogens, inhibit the formation of biofilms, and eradicate pre-formed biofilms. Results: Twenty-nine isolates of common wound-infecting pathogens were tested. Acetic acid was antibacterial against planktonic growth, with an minimum inhibitory concentration of 0.16-0.31% for all isolates, and was also able to prevent formation of biofilms (at 0.31 %). Eradication of mature biofilms was observed for all isolates after three hours of exposure. Conclusions: This study provides evidence that acetic acid can inhibit growth of key burn wound pathogens when used at very dilute concentrations. Owing to current concerns of the reducing efficacy of systemic antibiotics, this novel biocide application offers great promise as a cheap and effective measure to treat infections in burns patients

Hypervirulent Clostridium difficile PCR-Ribotypes Exhibit Resistance to Widely Used Disinfectants

The increased prevalence of Clostridium difficile infection (CDI) has coincided with enhanced transmissibility and severity of disease, which is often linked to two distinct clonal lineages designated PCR-ribotype 027 and 017 responsible for CDI outbreaks in the USA, Europe and Asia. We assessed sporulation and susceptibility of three PCR-ribotypes; 012, 017 and 027 to four classes of disinfectants; chlorine releasing agents (CRAs), peroxygens, quaternary ammonium compounds (QAC) and biguanides. The 017 PCR-ribotype, showed the highest sporulation frequency under these test conditions. The oxidizing biocides and CRAs were the most efficacious in decontamination of C. difficile vegetative cells and spores, the efficacy of the CRAs were concentration dependent irrespective of PCR-ribotype. However, there were differences observed in the susceptibility of the PCR-ribotypes, independent of the concentrations tested for Virkon®, Newgenn®, Proceine 40® and Hibiscrub®. Whereas, for Steri7® and Biocleanse® the difference observed between the disinfectants were dependent on both PCR-ribotype and concentration. The oxidizing agent Perasafe® was consistently efficacious across all three PCR ribotypes at varying concentrations; with a consistent five Log10 reduction in spore titre. The PCR-ribotype and concentration dependent differences in the efficacy of the disinfectants in this study indicate that disinfectant choice is a factor for llimiting the survival and transmission of C. difficile spores in healthcare settings

Use of UV-C radiation to disinfect non-critical patient care items: a laboratory assessment of the Nanoclave Cabinet

<p>Abstract</p> <p>Background</p> <p>The near-patient environment is often heavily contaminated, yet the decontamination of near-patient surfaces and equipment is often poor. The Nanoclave Cabinet produces large amounts of ultraviolet-C (UV-C) radiation (53 W/m²) and is designed to rapidly disinfect individual items of clinical equipment. Controlled laboratory studies were conducted to assess its ability to eradicate a range of potential pathogens including <it>Clostridium difficile</it> spores and Adenovirus from different types of surface.</p> <p>Methods</p> <p>Each test surface was inoculated with known levels of vegetative bacteria (10⁶ cfu/cm²), <it>C. difficile</it> spores (10²-10⁶ cfu/cm²) or Adenovirus (10⁹ viral genomes), placed in the Nanoclave Cabinet and exposed for up to 6 minutes to the UV-C light source. Survival of bacterial contaminants was determined via conventional cultivation techniques. Degradation of viral DNA was determined via PCR. Results were compared to the number of colonies or level of DNA recovered from non-exposed control surfaces. Experiments were repeated to incorporate organic soils and to compare the efficacy of the Nanoclave Cabinet to that of antimicrobial wipes.</p> <p>Results</p> <p>After exposing 8 common non-critical patient care items to two 30-second UV-C irradiation cycles, bacterial numbers on 40 of 51 target sites were consistently reduced to below detectable levels (≥ 4.7 log₁₀ reduction). Bacterial load was reduced but still persisted on other sites. Objects that proved difficult to disinfect using the Nanoclave Cabinet (e.g. blood pressure cuff) were also difficult to disinfect using antimicrobial wipes. The efficacy of the Nanoclave Cabinet was not affected by the presence of organic soils. <it>Clostridium difficile</it> spores were more resistant to UV-C irradiation than vegetative bacteria. However, two 60-second irradiation cycles were sufficient to reduce the number of surface-associated spores from 10³ cfu/cm² to below detectable levels. A 3 log₁₀ reduction in detectable Adenovirus DNA was achieved within 3 minutes; after 6 minutes, viral DNA was undetectable.</p> <p>Conclusion</p> <p>The results of this study suggest that the Nanoclave Cabinet can provide rapid and effective disinfection of some patient-related equipment. However, laboratory studies do not necessarily replicate ‘in-use’ conditions and further tests are required to assess the usability, acceptability and relative performance of the Nanoclave Cabinet when used <it>in situ</it>.</p

Antimicrobial dressings: Comparison of the ability of a panel of dressings to prevent biofilm formation by key burn wound pathogens

UNLABELLED: Antimicrobial medicated dressings (AMD) are often used to reduce bacterial infection of burns and other wounds. However, there is limited literature regarding comparative efficacies to inform effective clinical decision making. OBJECTIVES: Following on from a previous study where we demonstrated good antibiofilm properties of acetic acid (AA), we assessed and compared the in vitro anti-biofilm activity of a range of AMDs and non-AMDs to AA. METHODS: Laboratory experiments determined the ability of a range of eleven commercial AMD, two nAMD, and AA, to prevent the formation of biofilms of a panel of four isolates of Pseudomonas aeruginosa and Acinetobacter baumannii. RESULTS: There is a large variation in ability of different dressings to inhibit biofilm formation, seen between dressings that contain the same, and those that contain other antimicrobial agents. The best performing AMD were Mepilex(®) Ag and Acticoat. AA consistently prevented biofilm formation. CONCLUSIONS: Large variation exists in the ability of AMD to prevent biofilm formation and colonisation of wounds. A standardised in vitro methodology should be developed for external parties to examine and compare the efficacies of commercially available AMDs, along with robust clinical randomised controlled trials. This is essential for informed clinical decision-making and optimal patient management

Graph showing the mean average biomass of the biofilms produced by all isolates, as measured through the crystal violet assay.

<p>Optical density on the y axis refers to the average biofilm biomass (in the absence of AA) for all the isolates shown on the x axis. White (unshaded) bars represent isolates that were excluded from further testing owing to poor biofilming ability when compared to their other species counterparts. Red bars represent the isolates with unreliable biofilm production. Error bars represent the standard error for each average value and asterisks denote values statistically significantly different from the broth only control.</p

Table showing the tests performed on the isolates and their MIC, MBIC and MBEC values of AA.

<p>^a ✓ denotes that the test was performed and the result.</p><p>^b denotes that there was statistically significant reduction in seeding at all concentrations of AA (t-test, p<0.05)</p><p>Table showing the tests performed on the isolates and their MIC, MBIC and MBEC values of AA.</p

Graph showing the MBEC results for isolates AB_AYE and MDR_A.

<p>Optical density on the y axis refers to the average biofilm seeding for isolates AB_AYE and MDR_A after 3 hours of exposure to AA at the range of dilutions tested. POS: positive control, NEG: negative (broth only) control. The vertical line represents the MBEC, the error bars represent the standard error, and asterisks denote dilutions with statistically significant reductions in the seeding of the biofilm according to the t-test.</p

List of the control and clinical isolates used in this study.

<p>^ Carbapenemase producing Enterobacteriaceae</p><p>⁺ New Delhi metallo-β-lactamase</p><p>* Carbapenem resistant Enterobacteriaceae</p><p>^@ Extended-Spectrum β-lactamase</p><p>^$ Verona integron-encoded metallo-β-lactamase</p><p>^# AmpC-type β-lactamase</p><p>^£ genotyping refers to VNTR profile for <i>P</i>. <i>aeruginosa</i> and PFGE data for <i>Acinetobacter</i>.</p><p>List of the control and clinical isolates used in this study.</p