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Staphylococcus aureus and Pseudomonas aeruginosa are the most common bacteria co-isolated from chronic infected wounds. Their interactions remain unclear but this coexistence is beneficial for both bacteria and may lead to resistance to antimicrobial treatments. Besides, developing an in vitro model where this coexistence is recreated remains challenging, making difficult their study. The aim of this work was to develop a reliable polymicrobial in vitro model of both species to further understand their interrelationships and the effects of different antimicrobials in coculture. In this work, bioluminescent and fluorescent bacteria were used to evaluate the activity of two antiseptics (chlorhexidine and thymol) against these bacteria planktonically grown, or when forming single and mixed biofilms. At the doses tested (0.4-1,000 mg/L), thymol showed selective antimicrobial action against S. aureus in planktonic and biofilm states, in contrast with chlorhexidine which exerted antimicrobial effects against both bacteria. Furthermore, the initial conditions for both bacteria in the co-culture determined the antimicrobial outcome, showing that P. aeruginosa impaired the proliferation and metabolism of S. aureus . Moreover, S. aureus showed an increased tolerance against antiseptic treatments when co-cultured, attributed to the formation of a thicker mixed biofilm compared to those obtained when monocultured, and also, by the reduction of S. aureus metabolic activity induced by diffusible molecules produced by P. aeruginosa. This work underlines the relevance of polymicrobial populations and their crosstalk and microenvironment in the search of disruptive and effective treatments for polymicrobial biofilms.

Following a single blind, cross-over and non-randomized design we investigated the effect of 7-day use of chlorhexidine (CHX) mouthwash on the salivary microbiome as well as several saliva and plasma biomarkers in 36 healthy individuals. They rinsed their mouth (for 1 min) twice a day for seven days with a placebo mouthwash and then repeated this protocol with CHX mouthwash for a further seven days. Saliva and blood samples were taken at the end of each treatment to analyse the abundance and diversity of oral bacteria, and pH, lactate, glucose, nitrate and nitrite concentrations. CHX significantly increased the abundance of Firmicutes and Proteobacteria, and reduced the content of Bacteroidetes, TM7, SR1 and Fusobacteria. This shift was associated with a significant decrease in saliva pH and buffering capacity, accompanied by an increase in saliva lactate and glucose levels. Lower saliva and plasma nitrite concentrations were found after using CHX, followed by a trend of increased systolic blood pressure. Overall, this study demonstrates that mouthwash containing CHX is associated with a major shift in the salivary microbiome, leading to more acidic conditions and lower nitrite availability in healthy individuals.

BackgroundProspective randomized controlled studies have demonstrated that addition of chlorhexidine (CHG) dressings reduces the rate of catheter (central venous and arterial)-associated bloodstream infections (CABSIs). However, studies confirming their impact in a real-world setting are lacking.MethodsWe conducted a real-world data study evaluating the impact of incrementally introducing chlorhexidine dressings (sponge or gel) in addition to an ongoing catheter bundle on the rates of CABSI, expressed as incidence density rates per 1000 catheter-days measured as part of a surveillance program. Poisson regression models were used to compare infection rates over time. Both dressings were used simultaneously during one of the five study periods.ResultsFrom 2006 to 2014, 18,286 patients were admitted (91,292 ICU-days and 155,242 catheter-days). We recorded 111 CABSIs. We observed a progressive but significant decrease of CABSI rates from 1.48 (95% CI 1.09–2.01) without CHG dressings to 0.69 (95% CI 0.43–1.09) and 0.23 (95% CI 0.11–0.48) episodes per 1000 catheter-days when CHG sponge and CHG gel dressings were used (p = 0.0007; p < 0.001). A non-significant lower rate of infections occurred with CHG gel compared with CHG sponge dressings. An identical low rate of allergic skin reactions (0.3/1000 device-days) was observed with both types of CHX dressings. Post-study data until 2018 confirmed a sustained decrease of infection rates over 11 years.ConclusionsThe addition of chlorhexidine dressings to all CVC and arterial lines to an ongoing catheter bundle was associated with a sustained 11-year reduction of all catheter-associated bloodstream infections. This large real-world data study further supports the current recommendations for the systematic use of CHG dressings on all catheters of ICU patients.

BackgroundThe mechanism by which proton pump inhibitors (PPIs) alter gut microbiota remains to be elucidated. We aimed to learn whether PPI induced gut microbiota alterations by promoting oral microbial translocation.MethodsHealthy adult volunteers were randomly assigned: PP group (n=8, 40 mg esomeprazole daily for seven days) and PM group (n=8, 40 mg esomeprazole along with chlorhexidine mouthwash after each meal for seven days). Fecal and saliva samples were analysed using 16S ribosomal RNA sequencing. Mouse models were introduced to confirm the findings in vivo, while the effect of pH on oral bacteria proliferation activity was investigated in vitro.ResultsTaxon-based analysis indicated that PPI administration increased Streptococcus abundance in gut microbiota (P<0.001), and the increased species of Streptococcus were found to be from the oral site or oral/nasal sites, in which Streptococcus anginosus was identified as the significantly changed species (P<0.004). Microbial source tracker revealed that PPI significantly increased the contribution of oral bacteria to gut microbiota (P=0.026), and no significant difference was found in PM group (P=0.467). Compared to the baseline, there was a 42-fold increase in gut abundance of Streptococcus anginosus in PP group (P=0.002), and the times decreased to 16-fold in PM group (P=0.029). Mouse models showed that combination of PPI and Streptococcus anginosus significantly increased the gut abundance of Streptococcus anginosus compared with using PPI or Streptococcus anginosus only. Furthermore, Streptococcus anginosus cannot survive in vitro at a pH lower than 5.ConclusionsPPIs altered gut microbiota by promoting oral-originated Streptococcus translocation into gut.

Surface contamination is an important, if under-discussed, route of infection transmission. In this study, we suspended chlorhexidine digluconate (CHX) in epoxy resin. CHX was found to be stably incorporated into the material, and its addition to epoxy resin was found to have minimal effects on the optical transparency of the material. After application of the epoxy resin to steel surfaces, time-of-flight secondary ion mass spectrometry revealed that CHX was uniformly present over the surface. Surfaces painted with CHX-resin were found to have significant, reproducible antimicrobial efficacy against E. coli , S. aureus , and C. albicans . We have shown that the addition of CHX has minimal effects on the adhesion of the epoxy resin to surfaces, as well as a high durability of the antimicrobial efficacy. We believe that this material has a wide array of applications, and could be utilised to confer significant, low-cost antimicrobial efficacy to existing surfaces, to prevent surface contamination, and to stop the transmission of infectious disease.

The COVID-19 pandemic has demonstrated the real need for mechanisms to control the spread of airborne respiratory pathogens. Thus, preventing the spread of disease from pathogens has come to the forefront of the public consciousness. This has brought an increasing demand for novel technologies to prioritise clean air. In this study we report on the efficacy of novel biocide treated filters and their antimicrobial activity against bacteria, fungi and viruses. The antimicrobial filters reported here are shown to kill pathogens, such as Candida albicans , Escherichia coli and MRSA in under 15 min and to destroy SARS-CoV-2 viral particles in under 30 s following contact with the filter. Through air flow rate testing, light microscopy and SEM, the filters are shown to maintain their structure and filtration function. Further to this, the filters are shown to be extremely durable and to maintain antimicrobial activity throughout the operational lifetime of the product. Lastly, the filters have been tested in field trials onboard the UK rail network, showing excellent efficacy in reducing the burden of microbial species colonising the air conditioning system.

Chlorhexidine (CHX) was introduced for use as an antimicrobial more than 70 years ago. CHX has been and continues to be used broadly for disinfecting surfaces in medical and food service facilities as well as directly on skin of humans and animals. Considering its widespread use over many decades, questions of resistance to CHX have been raised. Additionally, questions of possible coincident resistance to the biocide and resistance to clinically relevant antibiotics have also been raised. A number of important questions remain, including is there consistent evidence of resistance, what is the degree of resistance, especially among clinically isolated microbial strains, and what is the degree of resistance compared to the typical concentrations of the biocide used? Data for microbial species isolated over the last 70+ years were compiled to construct as complete a picture as practical regarding possible resistance, especially among species in which resistance to commonly used antibiotics has been noted to be increasing. This is a compilation and analysis of individual MIC values for CHX reported in the literature, not a compilation of the conclusions individual authors reached. The data were analyzed using straight-forward and robust statistical procedures to detect changes in susceptibility to CHX over time, i.e. linear regression. Linear regression was supplemented with the use of nonlinear least squares regression analysis to detect the presence of population parameters associated with subpopulations of microbial strains which exhibit increased resistance to CHX. Pseudomonas aeruginosa , Klebsiella pneumoniae , and Acinetobacter baumannii were all found to have an increased resistance to CHX over time with the most profound change detected in A . baumannii . Additionally, subpopulations with log-normal distributions were found consistent with the presence of a baseline subpopulation of susceptible strains and a subpopulation with increased resistance to CHX. However, the CHX-resistant subpopulations did not correlate exactly with antibiotic resistance, so details of the relationship remain to be addressed. Increased resistance over time was not detected for Escherichia coli , Enterobacter faecalis , Staphylococcus aureus , or Candida albicans , although a subpopulation with greater than baseline resistance to CHX was detected among strains of E . faecalis and C . albicans . A difference in susceptibility to CHX was also detected between methicillin-resistant (MRSA) and methicillin-sensitive (MSSA) S . aureus strains. The levels of resistance to CHX detected were all markedly lower than concentrations routinely used in medical and food service applications. Reaching conclusions regarding the relationship between antibiotic and CHX resistance was complicated by the limited overlap between tests of CHX and antibiotic resistance for several species. The results compiled here may serve as a foundation for monitoring changes in resistance to CHX and possible relationships between the use of CHX and resistance to antibiotics commonly used in clinical medicine.

The evaluation of chlorhexidine-carrier nanosystems based on iron oxide magnetic nanoparticles (IOMNPs), has gained significant attention in recent years due to the unique properties of the magnetic nanoparticles (NPSs). Chlorhexidine (CHX), a well-established antimicrobial agent, has been widely used in medical applications, including oral hygiene and surgical antisepsis. This study aims to report an in vitro and in ovo toxicological screening of the synthesized CHX-NPS nanosystem, of the carrier matrix (maghemite NPSs) and of the drug to be delivered (CHX solution), by employing two types of cell lines—HaCaT immortalized human keratinocytes and JB6 Cl 41-5a murine epidermal cells. After the characterization of the CHX-NPS nanosystem through infrared spectroscopy and electronic microscopy, the in vitro results showed that the CHX antimicrobial efficacy was enhanced when delivered through a nanoscale system, with improved bioavailability and reduced toxicity when this was tested as the newly CHX-NPS nanosystem. The in ovo screening exhibited that the CHX-NPS nanosystem did not cause any sign of irritation on the chorioallantoic membrane vasculature and was classified as a non-irritant substance. Despite this, future research should focus on optimizing this type of nanosystem and conducting comprehensive in vivo studies to validate its therapeutic efficacy and safety in clinical settings.

Sutures can cause challenging surgical site infections, due to capillary effects resulting in bacteria permeating wounds. Anti-microbial sutures may avoid these complications by inhibiting bacterial pathogens. Recently, first triclosan-resistances were reported and therefore alternative substances are becoming clinically relevant. As triclosan alternative chlorhexidine, the \"gold standard\" in oral antiseptics was used. The aim of the study was to optimize novel slow release chlorhexidine coatings based on fatty acids in surgical sutures, to reach a high anti-microbial efficacy and simultaneously high biocompatibility. Sutures were coated with chlorhexidine laurate and chlorhexidine palmitate solutions leading to 11, 22 or 33 µg/cm drug concentration per length. Drug release profiles were determined in aqueous elutions. Antibacterial efficacy against Staphylococcus aureus was assessed in agar diffusion tests. Biocompatibility was evaluated via established cytotoxicity assay (WST-1). A commercially triclosan-containing suture (Vicryl Plus), was used as anti-microbial reference. All coated sutures fulfilled European Pharmacopoeia required tensile strength and proved continuous slow drug release over 96 hours without complete wash out of the coated drug. High anti-microbial efficacy for up to 5 days was observed. Regarding biocompatibility, sutures using 11 µg/cm drug content displayed acceptable cytotoxic levels according to ISO 10993-5. The highest potential for human application were shown by the 11 µg/cm chlorhexidine coated sutures with palmitic acid. These novel coated sutures might be alternatives to already established anti-microbial sutures such as Vicryl Plus in case of triclosan-resistance. Chlorhexidine is already an established oral antiseptic, safety and efficacy should be proven for clinical applications in anti-microbial sutures.

Background and Objective Chlorhexidine (CH) and povidone-iodine (PI) are the most commonly used preoperative skin antiseptics at present. However, the prevention of the surgical site infection (SSI) and the incidence of skin adverse events do not reach a consistent statement and conclusion. This meta-analysis aimed to evaluate the efficacy of chlorhexidine and povidone-iodine in the prevention of postoperative surgical site infection and the incidence of corresponding skin adverse events. Method Substantial studies related to “skin antiseptic” and “surgical site infection” were consulted on PUBMED, Web of Science, EMBASE, and CNKI. The primary outcome was the incidence of postoperative SSI. The secondary outcome was associated with skin adverse events. All data were analyzed with Revman 5.3 software. Results A total of 30 studies were included, including 29,006 participants. This study revealed that chlorhexidine was superior to povidone-iodine in the prevention of postoperative SSI (risk ratio [RR], 0.65; 95% confidence interval [CI], 0.55–0.77; p  < 0.00001, I 2  = 57%). Further subgroup analysis showed that chlorhexidine was superior to povidone-iodine in the prevention of postoperative SSI in clean surgery (risk ratio [RR], 0.81; 95% confidence interval [CI], 0.67–0.98; p  = 0.03), I 2  = 28%) and clean-contaminated surgery (risk ratio [RR], 0.58; 95% confidence interval [CI], 0.47–0.73; p  < 0.00001, I 2  = 43%). However, there was no statistically significant difference in the incidence of skin adverse events between CH and PI groups. Conclusion Chlorhexidine was superior to povidone-iodine in preventing postoperative SSI, especially for the clean-contaminated surgery. However, there was no statistically significant difference in the incidence of skin adverse events between CH and PI groups.