Effect of prolonged exposure to disinfectants in the antimicrobial resistance profile of relevant microorganisms: a systematic review.

Antimicrobial resistance (AMR) constitutes a major global health threat, to a very large extent due to the inadequate use of antibiotics. Additionally, the misuse of disinfectants can also trigger the selection of resistant clones, where microorganisms develop an adaptative response and progress to resistance mechanisms. Cross-resistance may occur when biocides selective pressure induce antimicrobial resistance. This study intends to acknowledge the potential relationship between repeated and/or prolonged exposure to disinfectants and antimicrobial resistance profile adjustment. This systematic review was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies published until December 2023 that were related to the interaction between disinfectants and antimicrobials were included. Further selection was based on the methodology of exposure. The selected studies were found that included testing about "exposure to sublethal concentrations" for seventeen disinfectants. The mechanism of action for the majority of the disinfectants involved interactions with the cell membrane. Chlorhexidine was the most studied disinfectant. Adaptation phenomena related to disinfectant exposure was documented and development of cross-resistance to antimicrobials was verified for several species, including Streptococcus, K. pneumoniae, A. baumannii, S. aureus, P. aeruginosa and Candida spp. Changes associated with disinfectant exposure also influenced biofilm formation, colony morphology and efflux pump activity, three relevant determinants of loss of antibiotic efficacy.

Does repeated exposure to hydrogen peroxide induce Candida auris resistance?

BACKGROUND: To minimize environmental colonization by microorganisms that may persist and thrive in healthcare settings, thus reducing healthcare-associated infections (HAIs), new insights over already known biocides are certainly of relevance. Although the efficacy of hydrogen peroxide (H2O2) against the emergent yeast Candida auris is moderately documented, concerns over the potential induction of resistance after repeated exposure do persist. The main objective of the present study was to evaluate the hypothetical induction of Candida auris resistance following 30 days of consecutive exposure to lethal and sublethal concentrations of H2O2. Furthermore, the authors aimed to elucidate about the rank of efficacy of H2O2 against C. auris comparing to other Candida species and whether different strains of C. auris may display different susceptibilities to H2O2. METHODS: During the induction of resistance assays, both type strains and clinical isolates of Candida auris, Candida albicans and Candida parapsilosis were exposed repeatedly to defined concentrations of H2O2, for 30 days. RESULTS: After that period, no significant differences were found when comparing the minimal inhibitory concentration values of H2O2 in case of the induced strains versus each respective positive control. Moreover, H2O2 displayed similar effectiveness against all the tested Candida species and no differences were demonstrated among the distinct strains of C. auris. CONCLUSIONS: The adoption of H2O2 solutions in routine protocols in order to promote disinfection standards against Candida auris, improving patient safety and reducing healthcare costs, is certainly welcomed.

Hard-to-heal wounds, biofilm and wound healing: an intricate interrelationship.

Hard-to-heal wounds are a major public health problem that incur high economic costs. A major source of morbidity, they can have an overwhelming impact on patients, caregivers and society. In contrast to acute wound healing, which follows an 'orderly and timely reparative process', the healing of hard-to-heal wounds is delayed because the usual biological progression is interrupted. This article discusses hard-to-heal wounds, the impact they have on patients and healthcare systems, and how biofilms and other factors affect the wound-healing process. Controlling and preventing infection is of utmost importance for normal wound healing. Rational use of anti-infectious agents is crucial and is particularly relevant in the context of rising healthcare costs. Knowledge of the complex relationship between hard-to-heal wounds, biofilm formation and wound healing is vital for efficient management of hard-to-heal wounds.

Effective Disinfection of a Burn Unit after Two Cases of Sepsis Caused by Multi-Drug-Resistant Acinetobacter baumannii.

BACKGROUND: The healthcare environment is a potential source of microbial pathogens, which may promote infectious cross-transmission. Terminal automated cleaning methods such as hydrogen peroxide systems have proven to be more successful than manual techniques. The aim of this study was to evaluate the effectiveness of an automated aerosolized hydrogen peroxide/silver cations dry-mist system. The goal was to prevent microbial transmission to patients in a clinical setting after two cases of sepsis caused by multi-drug resistant Acinetobacter baumannii had been diagnosed in a burn unit that relied on manual cleaning techniques. MATERIALS AND METHODS: Samples were taken from room surfaces before and after the dry-mist system cycle, which was used to disinfect all burn unit rooms after patient discharge. The disinfection effectiveness was assessed using contact plate cultures, with microbial growth represented as the total number of colony forming units per square centimeter (CFUs/cm2). RESULTS: No positive cultures from surface samples were observed after the intervention with the dry-mist system. Specifically, no further Acinetobacter baumannii growth was detected. CONCLUSIONS: Our results support the use of the hydrogen peroxide/silver cations dry-mist system as an adjunct to standard manual cleaning and disinfection protocols used in the healthcare environment because of its broad-spectrum and high antimicrobial activity. This system may be a valuable option to consider, particularly in the control of microbial outbreaks.

In vitro antifungal activity and in vivo antibiofilm activity of cerium nitrate against Candida species.

OBJECTIVES: The objective of this study was to clarify the antifungal properties of cerium, a lanthanide member, against Candida species. A comprehensive study with planktonic and sessile cells was performed. The ability of cerium nitrate (CN) to impair in vitro and in vivo biofilm formation was evaluated and its potential use in biofilm treatment was also evaluated. METHODS: Forty-eight clinical isolates of different Candida species and the type strain ATCC 90028 were tested according to the protocol M27-A3. The MICs and minimum lethal concentrations were determined. A time-kill assay was performed and a cytometric kinetic study was performed using live/dead markers. Biofilm inhibition and biofilm susceptibility in the presence of cerium was evaluated by quantification of the biofilm metabolic activity and total biomass with XTT and crystal violet assays, respectively. CN in vivo efficacy as a coating for medical indwelling devices was evaluated for the first time for Candida parapsilosis, using a mouse subcutaneous foreign body model using polyurethane catheter segments. Scanning electron microscopy was used to assess biofilm architecture after CN treatment. RESULTS: The MICs for planktonic cells correlated with severe cellular metabolic activity impairment and membrane damage after 3 h of incubation. Moreover, CN efficiently prevented biofilm formation both in vitro and in vivo in segments of polyurethane catheters. At higher concentrations, it was also able to disorganize and almost eradicate preformed biofilms. CONCLUSIONS: Our results strongly suggest that CN application in the clinical setting might be effective in preventing the formation of biofilm-associated infections, namely through catheter coating and ultimately as an antimicrobial lock therapy.

Animal model of implant capsular contracture: effects of chitosan.

BACKGROUND: The mechanism(s) responsible for breast capsular contracture (CC) remain unknown, but inflammatory pathways play a role. Various molecules have been attached to implant shells in the hope of modifying or preventing CC. The intrinsic antibacterial and antifungal activities of chitosan and related oligochitosan molecules lend themselves well to the study of the infectious hypothesis; chitosan's ability to bind to growth factors, its hemostatic action, and its ability to activate macrophages, cause cytokine stimulation, and increase the production of transforming growth factor (TGF)-ß1 allow study of the hypertrophic scar hypothesis. OBJECTIVE: The authors perform a comprehensive evaluation, in a rabbit model, of the relationship between CC and histological, microbiological, and immunological characteristics in the presence of a chitooligosaccharide (COS) mixture and a low molecular weight chitosan (LMWC). METHODS: Eleven adult New Zealand rabbits were each implanted with three silicone implants: a control implant, one impregnated with COS, and one impregnated with LMWC. At four-week sacrifice, microdialysates were obtained in the capsule-implant interfaces for tumor necrosis factor alpha (TNF-α) and interleukin-8 (IL-8) level assessment. Histological and microbiological analyses were performed. RESULTS: Baker grade III/IV contractures were observed in the LMWC group, with thick capsules, dense connective tissue, and decreased IL-8 levels (p < .05) compared to control and COS groups. Capsule tissue bacterial types and microdialysate TNF-α levels were similar among all groups. CONCLUSIONS: Chitosan-associated silicone implantation in a rabbit model resulted in Baker grade III/IV CC. This preclinical study may provide a model to test various mechanistic hypotheses of breast capsule formation and subsequent CC.