Resistance of Bacteria to Biocides

Discovery of sulfonamide resistance genes in deep groundwater below Patna, India

Global usage of pharmaceuticals has led to the proliferation of bacteria that are resistant to antimicrobial treatments, creating a substantial public health challenge. Here, we investigate the emergence of sulfonamide resistance genes in groundwater and surface water in Patna, a rapidly developing city in Bihar, India. We report the first quantification of three sulfonamide resistance genes (sulI, sulII and sulIII) in groundwater (12-107 m in depth) in India. The mean relative abundance of gene copies was found to be sulI (2.4 × 10-2 copies/16S rRNA gene) > sulII (5.4 × 10-3 copies/16S rRNA gene) > sulIII (2.4 × 10-3 copies/16S rRNA gene) in groundwater (n = 15) and surface water (n = 3). A comparison between antimicrobial resistance (AMR) genes and wastewater indicators, particularly tryptophan:fulvic-like fluorescence, suggests that wastewater was associated with AMR gene prevalence. Urban drainage channels, containing hospital and domestic wastes, are likely a substantial source of antimicrobial resistance in groundwater and surface water, including the Ganges (Ganga) River. This study is a reference point for decision-makers in the fight against antimicrobial resistance because it quantifies and determines potential sources of AMR genes in Indian groundwater.

Resistance or tolerance? Highlighting the need for precise terminology in the field of disinfection

The terms resistance and tolerance are well defined in the context of antibiotic research. However, in the field of disinfection, these terms are often used synonymously, which creates ambiguity and can lead to misunderstandings and misconceptions. In addition, this inconsistency in terminology makes it difficult to assess the risk of a disinfectant resistance. This general review aims to discuss existing definitions of the terms adaptation, susceptibility, tolerance, persistence, and resistance in the light of disinfectants. The most ambiguity is found between tolerance and resistance. Whereas the former describes the not necessarily heritable survival of transient exposure to usually lethal concentrations, resistance is the strictly heritable ability to survive otherwise lethal concentrations of an antimicrobial agent, regardless of exposure time. A simple transfer of experience from antibiotic research is not recommended when assessing the risk of resistance to disinfectants, as there are important differences between antibiotics and disinfectants, although both are antimicrobials: (i) disinfectants are usually applied at concentrations that exceed the minimum inhibitory concentration by orders of magnitude, (ii) the exposure times of disinfectants are in the range of seconds, minutes, or a few hours, (iii) the mode of action of disinfectants is less specific, and (iv) disinfectants often contain more than one active agent with additive or synergistic effects. It is important to recognise that disinfectants, like other antimicrobial agents such as antibiotics, have a dualistic nature and should be used correctly and with caution.

Improvements of weaned pigs barn hygiene to reduce the spread of antimicrobial resistance

The spread of antimicrobial resistance (AMR) in animal husbandry is usually attributed to the use of antibiotics and poor hygiene and biosecurity. We therefore conducted experimental trials to improve hygiene management in weaned pig houses and assessed the impact on the spread. For each of the two groups examined, the experimental group (EG) and the control group (CG), three replicate batches of piglets from the same pig breeder, kept in pre-cleaned flat decks, were analyzed. In the flat decks of the experimental groups, the hygiene conditions (cleaning, disinfection, dust removal and fly control) were improved, while regular hygiene measures were carried out in the control groups. The occurrence and spread of AMR were determined in Escherichia coli (E. coli; resistance indicator) using cultivation-dependent (CFU) and -independent (qPCR) methods as well as whole genome sequencing of isolates in samples of various origins, including feces, flies, feed, dust and swabs. Surprisingly, there were no significant differences (p > 0.05) in the prevalence of resistant E. coli between the flat decks managed with conventional techniques and those managed with improved techniques. Selective cultivation delivered ampicillin- and sulfonamide-resistant E. coli proportions of up to 100% and 1.2%, respectively. While 0.5% E. coli resistant to cefotaxime and no ciprofloxacin resistance were detected. There was a significant difference (p < 0.01) in the abundance of the blaTEM-1 gene in fecal samples between EG and CG groups. The colonization of piglets with resistant pathogens before arrival, the movement of flies in the barn and the treatment of bacterial infections with antibiotics obscured the effects of hygiene improvement. Biocide tolerance tests showed no development of resistance to the farm regular disinfectant. Managing hygiene alone was insufficient for reducing antimicrobial resistances in piglet rearing. We conclude that the complex factors contributing to the presence and distribution of AMR in piglet barns underscore the necessity for a comprehensive management strategy.

Analysis of Antimicrobial Resistance in Bacterial Pathogens Recovered from Food and Human Sources: Insights from 639,087 Bacterial Whole-Genome Sequences in the NCBI Pathogen Detection Database

Understanding the role of foods in the emergence and spread of antimicrobial resistance necessitates the initial documentation of antibiotic resistance genes within bacterial species found in foods. Here, the NCBI Pathogen Detection database was used to query antimicrobial resistance gene prevalence in foodborne and human clinical bacterial isolates. Of the 1,843,630 sequence entries, 639,087 (34.7%) were assigned to foodborne or human clinical sources with 147,788 (23.14%) from food and 427,614 (76.88%) from humans. The majority of foodborne isolates were either Salmonella (47.88%), Campylobacter (23.03%), Escherichia (11.79%), or Listeria (11.3%), and the remaining 6% belonged to 20 other genera. Most foodborne isolates were from meat/poultry (95,251 or 64.45%), followed by multi-product mixed food sources (29,892 or 20.23%) and fish/seafood (6503 or 4.4%); however, the most prominent isolation source varied depending on the genus/species. Resistance gene carriage also varied depending on isolation source and genus/species. Of note, Klebsiella pneumoniae and Enterobacter spp. carried larger proportions of the quinolone resistance gene qnrS and some clinically relevant beta-lactam resistance genes in comparison to Salmonella and Escherichia coli. The prevalence of mec in S. aureus did not significantly differ between meat/poultry and multi-product sources relative to clinical sources, whereas this resistance was rare in isolates from dairy sources. The proportion of biocide resistance in Bacillus and Escherichia was significantly higher in clinical isolates compared to many foodborne sources but significantly lower in clinical Listeria compared to foodborne Listeria. This work exposes the gaps in current publicly available sequence data repositories, which are largely composed of clinical isolates and are biased towards specific highly abundant pathogenic species. We also highlight the importance of requiring and curating metadata on sequence submission to not only ensure correct information and data interpretation but also foster efficient analysis, sharing, and collaboration. To effectively monitor resistance carriage in food production, additional work on sequencing and characterizing AMR carriage in common commensal foodborne bacteria is critical.

Tracking of Bacteriophage Predation on Pseudomonas aeruginosa Using a New Radiofrequency Biofilm Sensor

Confronting the challenge of biofilm resistance and widespread antimicrobial resistance (AMR), this study emphasizes the need for innovative monitoring methods and explores the potential of bacteriophages against bacterial biofilms. Traditional methods, like optical density (OD) measurements and confocal microscopy, crucial in studying biofilm-virus interactions, often lack real-time monitoring and early detection capabilities, especially for biofilm formation and low bacterial concentrations. Addressing these gaps, we developed a new real-time, label-free radiofrequency sensor for monitoring bacteria and biofilm growth. The sensor, an open-ended coaxial probe, offers enhanced monitoring of bacterial development stages. Tested on a biological model of bacteria and bacteriophages, our results indicate the limitations of traditional OD measurements, influenced by factors like sedimented cell fragments and biofilm formation on well walls. While confocal microscopy provides detailed 3D biofilm architecture, its real-time monitoring application is limited. Our novel approach using radio frequency measurements (300 MHz) overcomes these shortcomings. It facilitates a finer analysis of the dynamic interaction between bacterial populations and phages, detecting real-time subtle changes. This method reveals distinct phases and breakpoints in biofilm formation and virion interaction not captured by conventional techniques. This study underscores the sensor's potential in detecting irregular viral activity and assessing the efficacy of anti-biofilm treatments, contributing significantly to the understanding of biofilm dynamics. This research is vital in developing effective monitoring tools, guiding therapeutic strategies, and combating AMR.

Disinfectants and antiseptics: mechanisms of action and resistance

Chemical biocides are used for the prevention and control of infection in health care, targeted home hygiene or controlling microbial contamination for various industrial processes including but not limited to food, water and petroleum. However, their use has substantially increased since the implementation of programmes to control outbreaks of methicillin-resistant Staphylococcus aureus, Clostridioides difficile and severe acute respiratory syndrome coronavirus 2. Biocides interact with multiple targets on the bacterial cells. The number of targets affected and the severity of damage will result in an irreversible bactericidal effect or a reversible bacteriostatic one. Most biocides primarily target the cytoplasmic membrane and enzymes, although the specific bactericidal mechanisms vary among different biocide chemistries. Inappropriate usage or low concentrations of a biocide may act as a stressor while not killing bacterial pathogens, potentially leading to antimicrobial resistance. Biocides can also promote the transfer of antimicrobial resistance genes. In this Review, we explore our current understanding of the mechanisms of action of biocides, the bacterial resistance mechanisms encompassing both intrinsic and acquired resistance and the influence of bacterial biofilms on resistance. We also consider the impact of bacteria that survive biocide exposure in environmental and clinical contexts.

Polyhexamethylene biguanide promotes adaptive cross-resistance to gentamicin in Escherichia coli biofilms

Antimicrobial resistance is a critical public health issue that requires a thorough understanding of the factors that influence the selection and spread of antibiotic-resistant bacteria. Biocides, which are widely used in cleaning and disinfection procedures in a variety of settings, may contribute to this resistance by inducing similar defense mechanisms in bacteria against both biocides and antibiotics. However, the strategies used by bacteria to adapt and develop cross-resistance remain poorly understood, particularly within biofilms -a widespread bacterial habitat that significantly influences bacterial tolerance and adaptive strategies. Using a combination of adaptive laboratory evolution experiments, genomic and RT-qPCR analyses, and biofilm structural characterization using confocal microscopy, we investigated in this study how Escherichia coli biofilms adapted after 28 days of exposure to three biocidal active substances and the effects on cross-resistance to antibiotics. Interestingly, polyhexamethylene biguanide (PHMB) exposure led to an increase of gentamicin resistance (GenR) phenotypes in biofilms formed by most of the seven E. coli strains tested. Nevertheless, most variants that emerged under biocidal conditions did not retain the GenR phenotype after removal of antimicrobial stress, suggesting a transient adaptation (adaptive resistance). The whole genome sequencing of variants with stable GenR phenotypes revealed recurrent mutations in genes associated with cellular respiration, including cytochrome oxidase (cydA, cyoC) and ATP synthase (atpG). RT-qPCR analysis revealed an induction of gene expression associated with biofilm matrix production (especially curli synthesis), stress responses, active and passive transport and cell respiration during PHMB exposure, providing insight into potential physiological responses associated with adaptive crossresistance. In addition, confocal laser scanning microscopy (CLSM) observations demonstrated a global effect of PHMB on biofilm architectures and compositions formed by most E. coli strains, with the appearance of dense cellular clusters after a 24h-exposure. In conclusion, our results showed that the PHMB exposure stimulated the emergence of an adaptive cross-resistance to gentamicin in biofilms, likely induced through the activation of physiological responses and biofilm structural modulations altering gradients and microenvironmental conditions in the biological edifice.

Mechanisms of emerging resistance associated with non-antibiotic antimicrobial agents: a state-of-the-art review

Although the development of resistance by microorganisms to antimicrobial drugs has been recognized as a global public health concern, the contribution of various non-antibiotic antimicrobial agents to the development of antimicrobial resistance (AMR) remains largely neglected. The present review discusses various chemical substances and factors other than typical antibiotics, such as preservatives, disinfectants, biocides, heavy metals and improper chemical sterilization that contribute to the development of AMR. Furthermore, it encompasses the mechanisms like co-resistance and co-selection, horizontal gene transfer, changes in the composition and permeability of cell membrane, efflux pumps, transposons, biofilm formation and enzymatic degradation of antimicrobial chemicals which underlie the development of resistance to various non-antibiotic antimicrobial agents. In addition, the review addresses the resistance-associated changes that develops in microorganisms due to these agents, which ultimately contribute to the development of resistance to antibiotics. In order to prevent the indiscriminate use of chemical substances and create novel therapeutic agents to halt resistance development, a more holistic scientific approach might provide diversified views on crucial factors contributing to the persistence and spread of AMR. The review illustrates the common and less explored mechanisms contributing directly or indirectly to the development of AMR by non-antimicrobial agents that are commonly used.

A Critical Review of AMR Risks Arising as a Consequence of Using Biocides and Certain Metals in Food Animal Production

The focus of this review was to assess what evidence exists on whether, and to what extent, the use of biocides (disinfectants and sanitizers) and certain metals (used in feed and other uses) in animal production (both land and aquatic) leads to the development and spread of AMR within the food chain. A comprehensive literature search identified 3434 publications, which after screening were reduced to 154 relevant publications from which some data were extracted to address the focus of the review. The review has shown that there is some evidence that biocides and metals used in food animal production may have an impact on the development of AMR. There is clear evidence that metals used in food animal production will persist, accumulate, and may impact on the development of AMR in primary animal and food production environments for many years. There is less evidence on the persistence and impact of biocides. There is also particularly little, if any, data on the impact of biocides/metal use in aquaculture on AMR. Although it is recognized that AMR from food animal production is a risk to human health there is not sufficient evidence to undertake an assessment of the impact of biocide or metal use on this risk and further focused in-field studies are needed provide the evidence required.

Biocides in the Hospital Environment: Application and Tolerance Development

Hospital-acquired infections are a rising problem with consequences for patients, hospitals, and health care workers. Biocides can be employed to prevent these infections, contributing to eliminate or reduce microorganisms' concentrations at the hospital environment. These antimicrobials belong to several groups, each with distinct characteristics that need to be taken into account in their selection for specific applications. Moreover, their activity is influenced by many factors, such as compound concentration and the presence of organic matter. This article aims to review some of the chemical biocides available for hospital infection control, as well as the main factors that influence their efficacy and promote susceptibility decreases, with the purpose to contribute for reducing misusage and consequently for preventing the development of resistance to these antimicrobials.

Fuse feeds as one: cross-modal framework for general identification of AMPs

Antimicrobial peptides (AMPs) are promising candidates for the development of new antibiotics due to their broad-spectrum activity against a range of pathogens. However, identifying AMPs through a huge bunch of candidates is challenging due to their complex structures and diverse sequences. In this study, we propose SenseXAMP, a cross-modal framework that leverages semantic embeddings of and protein descriptors (PDs) of input sequences to improve the identification performance of AMPs. SenseXAMP includes a multi-input alignment module and cross-representation fusion module to explore the hidden information between the two input features and better leverage the fusion feature. To better address the AMPs identification task, we accumulate the latest annotated AMPs data to form more generous benchmark datasets. Additionally, we expand the existing AMPs identification task settings by adding an AMPs regression task to meet more specific requirements like antimicrobial activity prediction. The experimental results indicated that SenseXAMP outperformed existing state-of-the-art models on multiple AMP-related datasets including commonly used AMPs classification datasets and our proposed benchmark datasets. Furthermore, we conducted a series of experiments to demonstrate the complementary nature of traditional PDs and protein pre-training models in AMPs tasks. Our experiments reveal that SenseXAMP can effectively combine the advantages of PDs to improve the performance of protein pre-training models in AMPs tasks.

Current Understanding of Potential Linkages between Biocide Tolerance and Antibiotic Cross-Resistance

Antimicrobials (e.g., antibiotics and biocides) are invaluable chemicals used to control microbes in numerous contexts. Because of the simultaneous use of antibiotics and biocides, questions have arisen as to whether environments commonly treated with biocides (e.g., hospitals, food processing, wastewater, agriculture, etc.) could act as a reservoir for the development of antibiotic cross-resistance. Theoretically, cross-resistance could occur if the mechanism of bacterial tolerance to biocides also resulted in antibiotic resistance. On the other hand, biocides would likely present a higher evolutionary barrier to the development of resistance given the different modes of action between biocides and antibiotics and the broad-based physicochemical effects associated with most biocides. Published studies have shown that the induction of biocide tolerance in a laboratory can result in cross-resistance to some antibiotics, most commonly hypothesized to be due to efflux pump upregulation. However, testing of environmental isolates for biocide tolerance and antibiotic cross-resistance has yielded conflicting results, potentially due to the lack of standardized testing. In this review, we aim to describe the state of the science on the potential linkage between biocide tolerance and antibiotic cross-resistance. Questions still remain about whether the directed evolution of biocide tolerance and the associated antibiotic cross-resistance in a laboratory are or are not representative of real-world settings. Thus, research should continue to generate informative data to guide policies and preserve these tools' utility and availability.

Prevention of horizontal transfer of laboratory plasmids to environmental bacteria: comparison of the effectiveness of a few disinfection approaches to degrade DNA

The routine work of any molecular biology laboratory includes the daily use of microorganisms, including strains of E. coli, transformed with a variety of plasmids expressing at least one antibiotic resistance gene (ARG). Therefore, to avoid the accidental release of ARGs into environmental water, methods for disinfection of liquid laboratory waste must be effective in destroying nucleic acids. In support of this recommendation, the origin of replication of Enterobacteriaceae plasmids has been detected in strains of non-Enterobacteriaceae bacteria isolated from wastewater from laboratories and research institutes, suggesting that interspecific transfer of laboratory plasmids had occurred. Using quantitative polymerase chain reaction, we determined the decimal reduction value (D value, expressed as concentration of disinfectant or length of physical treatment) of several decontamination methods for their DNA degradation effect on cultures of E. coli Top10 transformed with a kanamycin resistant plasmid (pET28A + or pEGFP-C2). The estimated D values were 0.7 M for sulfuric acid, 6.3% for a commercial P3 disinfectant, 25 min for steam sterilization at 121 °C, and 49 min for disinfection by UVC. A 20-min treatment of bacteria cultures with a final concentration of 1-10% sodium hypochlorite was found to be ineffective in completely destroying a bacteria plasmid gene marker (coding for the pBR322 origin of replication). Residual DNA from NaClO-treated cells was 60%, while it decreased under 10% using the commercial disinfectant P3 diluted at 5%. As the degradation was incomplete in both cases, we recommend avoiding discharge of disinfected liquid waste to wastewater (even after chemical neutralization) without additional plasmid destruction treatment, to prevent horizontal transfer of laboratory ARGs to environmental bacteria.

Mechanisms of Antibiotic and Biocide Resistance That Contribute to Pseudomonas aeruginosa Persistence in the Hospital Environment

Pseudomonas aeruginosa is an opportunistic bacterial pathogen responsible for multiple hospital- and community-acquired infections, both in human and veterinary medicine. P. aeruginosa persistence in clinical settings is worrisome and is a result of its remarkable flexibility and adaptability. This species exhibits several characteristics that allow it to thrive under different environmental conditions, including the ability to colonize inert materials such as medical equipment and hospital surfaces. P. aeruginosa presents several intrinsic mechanisms of defense that allow it to survive external aggressions, but it is also able to develop strategies and evolve into multiple phenotypes to persevere, which include antimicrobial-tolerant strains, persister cells, and biofilms. Currently, these emergent pathogenic strains are a worldwide problem and a major concern. Biocides are frequently used as a complementary/combination strategy to control the dissemination of P. aeruginosa-resistant strains; however, tolerance to commonly used biocides has also already been reported, representing an impediment to the effective elimination of this important pathogen from clinical settings. This review focuses on the characteristics of P. aeruginosa responsible for its persistence in hospital environments, including those associated with its antibiotic and biocide resistance ability.

Emergence of Tobramycin Escherichia coli resistance in poultry meat linked to biocides overuse during COVID-19

The effect of excessive use of biocides during the COVID-19, on the resistance of Escherichia coli to Tobramycin in poultry, meat was examined in this observational epidemiological study (Before and after COVID–19). Tobramycin E. coli resistant strains isolated from poultry meat before COVID-19 appearance were compared with those isolated after COVID-19 emergence. Univariable analyses were performed using t-test and chi-squared test. Odds ratios and 95% confidence intervals were used for statistically significant risk factor. Multivariate analysis was done with the binary logistic regression to detect an independent predictor, and with the principal component analysis (PCA), to analyze whether the Tobramycin resistance in E. coli was linked with the COVID-19 outbreak. Statistical significance was set at P<0.05. The frequency of Tobramycin E. coli resistant isolates was more important after COVID-19 emergence (12.5%) than before COVID-19 (2.1%). Graphical representation of PCA qualitative variables shows the interfactor relationship. A significant relationship between Tobramycin E. coli resistance and COVID-19 emergence (P=0.014), and the effect of the emergence of COVID-19 on the Tobramycin E. coli resistance was OR = 6.57 (95% Confidence interval (CI) 1.61-7.94). The probability of Tobramycin E. coli resistance linked with poultry meat bought after COVID-19 was 1.88 times more than before COVID-19 emergence. Poultry meat purchased after COVID-19 found related to Tobramycin resistance in E. coli. It seems possible that the overuse of biocides during COVID-19 increased the risk of Tobramycin E. coli resistance in poultry meat.

Towards a Harmonized Terminology: A Glossary for Biocide Susceptibility Testing

Disinfection is a key strategy to reduce the burden of infections. The contact of bacteria to biocides-the active substances of disinfectants-has been linked to bacterial adaptation and the development of antimicrobial resistance. Currently, there is no scientific consensus on whether the excessive use of biocides contributes to the emergence and spread of multidrug resistant bacteria. The comprehensive analysis of available data remains a challenge because neither uniform test procedures nor standardized interpretive criteria nor harmonized terms are available to describe altered bacterial susceptibility to biocides. In our review, we investigated the variety of criteria and the diversity of terms applied to interpret findings in original studies performing biocide susceptibility testing (BST) of field isolates. An additional analysis of reviews summarizing the knowledge of individual studies on altered biocide susceptibility provided insights into currently available broader concepts for data interpretation. Both approaches pointed out the urgent need for standardization. We, therefore, propose that the well-established and approved concepts for interpretation of antimicrobial susceptibility testing data should serve as a role model to evaluate biocide resistance mechanisms on a single cell level. Furthermore, we emphasize the adaptations necessary to acknowledge the specific needs for the evaluation of BST data. Our approach might help to increase scientific awareness and acceptance.

In-use contamination of a hospital-grade disinfectant

BACKGROUND

Microbiological monitoring of disinfection of high-touch surfaces identified heavy growth of Serratia marcescens and Achromobacter xylosoxidans not present on surfaces before disinfection, suggesting contamination of the disinfectant used.

METHODS

An investigation included interview of the housekeeper involved, level of bacterial contamination of the in-use quaternary ammonium (Quat) disinfectant, bactericidal activity of the contaminated disinfectant, pulsed field gel electrophoresis of S.marcescens and Achromobacter isolates, survival of S. marcescens on dry surfaces, and genome sequencing to identify possible Quat resistance genes.

RESULTS

The housekeeper, who seldom cleaned patient rooms, had used the disinfectant for months without emptying and drying the bucket between uses. The contaminated disinfectant contained 9.3 × 10⁴ CFU of S. marcescens plus A. xylosoxidans. The log₁₀ reduction of S. marcescens by fresh Quat was 10²-fold lower than that achieved against a control strain (S. marcescens ATCC 13380). Genome sequencing of S. marcescens isolates identified the following genes previously shown to encode for efflux pumps associated with Quat resistance: sdeXY, sdeAB, smfY, and a sugE-like gene.

CONCLUSIONS

Failure to follow existing guidelines and manufacturer's instructions for use resulted in contamination by A. xylosoxidans and by S. marcescens that possessed multiple genes associated with Quat resistance.

Hand disinfectants and their activity against clinical isolates of Bordetella pertussis

OBJECTIVES

The aim of the study was to investigate possible emergence of resistance to disinfectants in Bordetella pertussis strains isolated from patients with whooping cough in the Czech Republic in 2014 and 2015.

METHODS

In an EN1500-based study, clean and dry fingertips of volunteers were always contaminated with one of the two clinical isolates of B. pertussis. Clinical isolates of B. pertussis were obtained from the National Reference Laboratory for Pertussis and Diphtheria, National Institute of Public Health (NIPH), Prague, Czech Republic. Dry and contaminated fingertips were immersed in 10 ml medium and then rubbed with the fingers for 1 minute. After that, the hands were treated with isopropanol 60% v/v or tested products, and then the fingertips were rubbed again into 10 ml of pure medium for 1 minute. The suspensions obtained were immediately diluted and plated on charcoal medium.

RESULTS

Ethanol-based product A and propanol-based product B showed bactericidal activity after 30 s of contact. The confidence interval limit for product A and B was 0.12 and 0.19, respectively. Quaternary ammonium compound-based product C was found to be ineffective after 30 s of contact. The confidence interval limit for product C was 0.62.

CONCLUSION

Products A and B were assessed as effective against clinical isolates of B. pertussis in accordance with EN 1500. Quaternary ammonium compound-based product C did not comply with the requirements of EN 1500.

Contribution of RND-Type Efflux Pumps in Reduced Susceptibility to Biocides in Acinetobacter baumannii

Bacterial efflux pumps are among the key mechanisms of resistance against antibiotics and biocides. We investigated whether differential expression levels of the RND-type efflux pumps AdeABC and AdeIJK impacted the susceptibility to commonly used biocides in multidrug-resistant Acinetobacter baumannii. Susceptibility testing and time-kill assays of defined laboratory and clinical A. baumannii strains with different levels of efflux pump expression were performed after exposure to the biocides benzalkonium chloride, chlorhexidine digluconate, ethanol, glucoprotamin, octenidine dihydrochloride, and triclosan. While the impact of efflux pump expression on susceptibility to the biocides was limited, noticeable differences were found in kill curves, where AdeABC expression correlated with greater survival after exposure to benzalkonium chloride, chlorhexidine digluconate, glucoprotamin, and octenidine dihydrochloride. AdeABC expression levels did not impact kill kinetics with ethanol nor triclosan. In conclusion, these data indicate that the overexpression of the RND-type efflux pumps AdeABC and AdeIJK contributes to the survival of A. baumannii when exposed to residual concentrations of biocides.

Antimicrobial resistance: new insights and therapeutic implications

Antimicrobial resistance has not been a new phenomenon. Still, the number of resistant organisms, the geographic areas affected by emerging drug resistance, and the magnitude of resistance in a single organism are enormous and mounting. Disease and disease-causing agents formerly thought to be contained by antibiotics are now returning in new forms resistant to existing therapies. Antimicrobial resistance is one of the most severe and complicated health issues globally, driven by interrelated dynamics in humans, animals, and environmental health sectors. Coupled with various epidemiological factors and a limited pipeline for new antimicrobials, all these misappropriations allow the transmission of drug-resistant organisms. The problem is likely to worsen soon. Antimicrobial resistance in general and antibiotic resistance in particular is a shared global problem. Actions taken by any single country can adversely or positively affect the other country. Targeted coordination and prevention strategies are critical in stopping the spread of antibiotic-resistant organisms and hence its overall management. This article has provided in-depth knowledge about various methods that can help mitigate the emergence and spread of antimicrobial resistance globally. KEY POINTS: • Overview of antimicrobial resistance as a global challenge and explain various reasons for its rapid progression. • Brief about the intrinsic and acquired resistance to antimicrobials and development of antibiotic resistance in bacteria. • Systematically organized information is provided on different strategies for tackling antimicrobial resistance for the welfare of human health.

Microbial resistance to sanitizers in the food industry: review

Hygiene programs which comprise the cleaning and sanitization steps are part of the Good Hygiene Practices (GHP) and are considered essential to ensure food safety and quality. Inadequate hygiene practices may contribute to the occurrence of foodborne diseases, development of microbial resistance to sanitizers, and economic losses. In general, the sanitizer resistance is classified as intrinsic or acquired. The former is an inherent characteristic, naturally present in some microorganisms, whereas the latter is linked to genetic modifications that can occur at random or after continuous exposure to a nonnormal condition. The resistance mechanisms can involve changes in membrane permeability or in the efflux pump, and enzymatic activity. The efflux pump mechanism is the most elucidated in relation to the resistance caused by the use of different types of sanitizers. In addition, microbial resistance to sanitizers can also be favored in the presence of biofilms due to the protection given by the glycocalyx matrix and genetic changes. Therefore, this review aimed to show the main microbial resistance mechanisms to sanitizers, including genetic modifications, biofilm formation, and permeability barrier.

Pseudomonas fluorescens Cells’ Recovery after Exposure to BAC and DBNPA Biocides

A proper assessment of the effects of biocides on bacterial cells is key to the prevention of antimicrobial resistance and the implementation of suitable biocidal programmes. It is particularly relevant regarding the ability of dead-labelled cells to recover their functional processes once the biocide is removed. In the present work, we studied how Pseudomonas fluorescens cells previously exposed to different concentrations of BAC (benzalkonium chloride) and DBNPA (2,2-Dibromo-3-nitrilopropionamide) behave upon the restoration of optimum growth conditions. The following indicators were evaluated: culturability, membrane integrity, metabolic activity (resazurin), cellular energy (ATP), and cell structure and morphology (transmission electron microscopy (TEM)). The results demonstrated that cells previously labelled as ‘dead’ recovered to a greater extent in all indicators. Only cells previously exposed to BAC at 160 mg/L (concentration above the MBC) showed significant reductions on all the evaluated indicators. However, the obtained values were much higher than the ‘death’ thresholds found for the autoclaved cells. This suggests that cells exposed to this concentration take more time to rebuild their functional processes. The recovery of DBNPA-treated cells did not seem to be related to the biocide concentration. Finally, a reflection on what kind of cells were able to recover (remaining cells below the detection limit and/or dormant cells) is also presented.

In vitro activity of six biocides against carbapenemase-producing Klebsiella pneumoniae and presence of genes encoding efflux pumps

INTRODUCTION

Acquisition of reduced susceptibility to biocides may contribute to the dissemination of high-risk (HR) clones of carbapenemase-producing Klebsiella pneumoniae (CP-Kp). The aim of this study was (a) to determinate the activity of biocides against CP-Kp, and (b) to analyse the relationship between biocide activity and the presence of efflux pumps.

METHODS

The minimal inhibitory concentrations (MICs) of 6 biocides (sodium hypochlorite, chlorhexidine digluconate, benzalkonium chloride, povidone-iodine, ethanol and triclosan) were determined in triplicate at 25°C and 37°C in Mueller-Hinton broth (MHB) and M9 minimum medium, against 17 CP-Kp isolates representing different clones (HR and no-HR), sequence-types (STs) and carbapenemases. Efflux pumps genes were detected by whole genome sequencing (MiSeq).

RESULTS

Median MICs were slightly higher at 37°C than at 25°C (p≤0.05), except for benzalkonium chloride, triclosan and ethanol. MIC medians were much higher in MHB than in M9, except for triclosan. No significant differences were observed in the median MICs, regarding the type of clone, ST or carbapenemase; cepA, acrAB, kpnEF and oqxAB genes were detected in all isolates, whereas qacE and qacA were not detected; smvAR, and qacΔE genes were detected in 94% and 47% of isolates, respectively.

CONCLUSIONS

Triclosan, chlorhexidine digluconate, benzalkonium chloride and ethanol were the most active biocides. The activity of some biocides is affected by temperature and growth media, suggesting that standardised procedures for biocide susceptibility testing based on MIC determination are required. This activity, in terms of MICs, are not related to the type of clone, ST, carbapenemase or the presence of the efflux pump genes.

Evaluation of Antimicrobial and Chemopreventive Properties and Phytochemical Analysis of Solanum nigrum L. Aerial Parts and Root Extracts

This study evaluated in vitro antibacterial, antifungal, anticancer and antioxidant activities of methanolic leaf and root extracts from Solanum nigrum L. and determined its chemical composition. The chemical profile of S. nigrum L. extract was tested using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Disc diffusion and microdilution assays were used for the antibacterial activities. Antifungal activity was measured using the poisoned food technique. In vitro activity on the cell culture model was assessed by MTT assay, viability measurement and by determination of cellular ROS by DCFDA assay. The minimal inhibitory concentrations for extracts from aerial parts ranged from 125 to 500 μg/mL for gram-positive cocci and Pectobacterium strains. The growth inhibition coefficient ranged from 17–56%, depending on the dosage. The antifungal effect of S. nigrum extracts on the tested filamentous fungi depended on the dose. An inhibitory effect of 50–56% on fungi was observed against Alternaria alternata and Chaetomium globosum. The study showed a reduction in cellular vitality of THP1, A549, MCF7 and HeLa cancer lines using both extracts. In addition, there was a decrease in the number of viable cells in cultures incubated with the extract of aerial parts and a reduction in oxygen radicals in the cells. The obtained results indicate the possibility of using S. nigrum extracts from the aerial part as antimicrobial factors. Both extracts show chemopreventive properties by inhibiting the growth of cancer cells and reducing the level of free radicals. Both extracts show chemopreventive properties by inhibiting cancer cell growth and lowering free radical levels. The broad biological activity of the studied extracts can be used in agriculture, veterinary usages and medicine.

Enterococcus Virulence and Resistant Traits Associated with Its Permanence in the Hospital Environment

Enterococcus are opportunistic pathogens that have been gaining importance in the clinical setting, especially in terms of hospital-acquired infections. This problem has mainly been associated with the fact that these bacteria are able to present intrinsic and extrinsic resistance to different classes of antibiotics, with a great deal of importance being attributed to vancomycin-resistant enterococci. However, other aspects, such as the expression of different virulence factors including biofilm-forming ability, and its capacity of trading genetic information, makes this bacterial genus more capable of surviving harsh environmental conditions. All these characteristics, associated with some reports of decreased susceptibility to some biocides, all described in this literary review, allow enterococci to present a longer survival ability in the hospital environment, consequently giving them more opportunities to disseminate in these settings and be responsible for difficult-to-treat infections.

Disinfection Strategies for Carbapenem-Resistant Klebsiella pneumoniae in a Healthcare Facility

Disinfectant resistance is evolving into a serious problem due to the long-term and extensive use of disinfectants, which brings great challenges to hospital infection control. As a notorious multidrug-resistant bacterium, carbapenem-resistant Klebsiella pneumoniae (CRKP) is one of the most common and difficult pathogens of nosocomial infection. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests of seven kinds of disinfectants (0.1% benzalkonium bromide, 4% aqueous chlorhexidine, 75% alcohol, entoiodine II, 2% glutaraldehyde, 2000 mg/L chlorine-containing disinfectants, and 3% hydrogen peroxide) were detected by the broth dilution method. Three efflux pump genes (oqxA, oqxB, and qacE∆1-sul1) were detected by PCR. The mean MIC value of aqueous chlorhexidine from the intensive care unit (ICU) (0.0034%) was significantly higher than that from non-ICUs (0.0019%) (p < 0.05). The positive rates of three efflux pump genes oqxA, oqxB and qacE∆1-sul1 were 60.9% (39/64), 17.2% (11/64) and 71.9% (46/64) in the detected CRKP isolates, respectively. This study discovered that CRKP strains demonstrated extensive resistance to clinical disinfectants and suggest that it is necessary to perform corresponding increases in the concentration of aqueous chlorhexidine and chlorine-containing disinfectants on the basis of current standards in the healthcare industry.

It is complicated: Potential short- and long-term impact of coronavirus disease 2019 (COVID-19) on antimicrobial resistance—An expert review

As of December 2021, the coronavirus disease 2019 (COVID-19) pandemic has claimed millions of deaths and caused disruptions in health systems around the world. The short- and long-term effects of COVID-19 on antimicrobial resistance (AMR), which was already a global threat before the pandemic, are manifold and complex. In this expert review, we summarize how COVID-19 might be affecting AMR in the short term (by influencing the key determinants antibiotic use, infection control practices and international/local mobility) and which additional factors might play a role in the long term. Whereas reduced outpatient antibiotic use in high-income countries, increased awareness for hand hygiene, and reduced mobility have likely mitigated the emergence and spread of AMR in the short term, factors such as overuse of antibiotics in COVID-19 patients, shortage of personal protective equipment, lack of qualified healthcare staff, and patient overcrowding have presumably facilitated its propagation. Unsurprisingly, international and national AMR surveillance data for 2020 show ambiguous trends. Although disruptions in antibiotic stewardship programs, AMR surveillance and research might promote the spread of AMR, other developments could prove beneficial to the cause in the long term. These factors include the increased public awareness for infectious diseases and infection control issues, the strengthening of the One Health perspective as outlined by the Centers for Disease Control and Prevention, and the unprecedented number of international research collaborations and platforms. These factors could even serve as leverage and provide opportunities to better combat AMR in the future.

Development of Quality Control Ranges for Biocide Susceptibility Testing

Every laboratory test needs validation by quality controls. For biocide susceptibility testing (BST), neither quality control (QC) strains nor QC ranges applicable to these strains are currently available. As QC strains, four well-defined laboratory reference strains (Staphylococcus aureus ATCC® 6538, Enterococcus hirae ATCC® 10541, Escherichia coli ATCC® 10536 and Pseudomonas aeruginosa ATCC® 15442), which have been used previously for biocide efficacy testing, were selected. In an interlaboratory trial with eleven participating laboratories, BST QC ranges should be developed for the aforementioned four strains and the four biocides benzalkonium chloride, chlorhexidine, octenidine and polyhexanide. The performance of three different lots of tryptic soy broth was explored using the broth microdilution method and the data were subsequently evaluated using the RangeFinder software. As a result, QC ranges were defined for all reference strain–biocide combinations, except for P. aeruginosa ATCC® 15442 with the two biocides chlorhexidine and polyhexanide. The development of the latter two QC ranges was not possible, due to the limited solubility of the biocides in the test range required for P. aeruginosa ATCC® 15442. The newly developed QC ranges comprise three to five dilution steps. The establishment of QC ranges will contribute to the validation of BST in the future.

Assessing the Risk of Resistance to Cationic Biocides incorporating Realism-based and Biophysical Approaches

The control of microorganisms is a key objective in disease prevention and in medical, industrial, domestic, and food-production environments. Whilst the effectiveness of biocides in these contexts is well-evidenced, debate continues about the resistance risks associated with their use. This has driven an increased regulatory burden, which in turn could result in a reduction of both the deployment of current biocides and the development of new compounds and formulas. Efforts to balance risk and benefit are therefore of critical importance and should be underpinned by realistic methods and a multi-disciplinary approach, and through objective and critical analyses of the literature. The current literature on this topic can be difficult to navigate. Much of the evidence for potential issues of resistance generation by biocides is based on either correlation analysis of isolated bacteria, where reports of treatment failure are generally uncommon, or laboratory studies that do not necessarily represent real biocide applications. This is complicated by inconsistencies in the definition of the term resistance. Similar uncertainties also apply to cross-resistance between biocides and antibiotics. Risk assessment studies that can better inform practice are required. The resulting knowledge can be utilised by multiple stakeholders including those tasked with new product development, regulatory authorities, clinical practitioners, and the public. This review considers current evidence for resistance and cross-resistance and outlines efforts to increase realism in risk assessment. This is done in the background of the discussion of the mode of application of biocides and the demonstrable benefits as well as the potential risks.

Biocide resistance in Acinetobacter baumannii: appraising the mechanisms

A global upsurge in antibiotic-resistant Acinetobacter baumannii requires supervised selection of biocides and disinfectants to avert nosocomial infections by reducing its spread. Moreover, inadequate and improper biocides have been reported as a contributing factor in antimicrobial resistance. Regardless of the manner of administration, a biocidal concentration that does not kill the target bacteria creates a stress response, propagating the resistance mechanisms. This is an essential aspect of the disinfection programme and the overall bio-contamination management plan. Knowing the mechanisms of action of biocides and resistance modalities may open new avenues to discover novel agents. This review describes the mechanisms of action of some biocides, resistance mechanisms, and approaches to study susceptibility/resistance to these agents.

The Influencing Factors of Bacterial Resistance Related to Livestock Farm: Sources and Mechanisms

Bacterial resistance is a complex scientific issue. To manage this issue, we need to deeply understand the influencing factors and mechanisms. Based on the background of livestock husbandry, this paper reviews the factors that affect the acquisition of bacterial resistance. Meanwhile, the resistance mechanism is also discussed. “Survival of the fittest” is the result of genetic plasticity of bacterial pathogens, which brings about specific response, such as producing adaptive mutation, gaining genetic material or changing gene expression. To a large extent, bacterial populations acquire resistance genes directly caused by the selective pressure of antibiotics. However, mobile resistance genes may be co-selected by other existing substances (such as heavy metals and biocides) without direct selection pressure from antibiotics. This is because the same mobile genetic elements as antibiotic resistance genes can be co-located by the resistance determinants of some of these compounds. Furthermore, environmental factors are a source of resistance gene acquisition. Here, we describe some of the key measures that should be taken to mitigate the risk of antibiotic resistance. We call on the relevant governments or organizations around the world to formulate and improve the monitoring policies of antibiotic resistance, strengthen the supervision, strengthen the international cooperation and exchange, and curb the emergence and spread of drug-resistant strains.

Environmental antimicrobial resistance and its drivers: a potential threat to public health

Imprudent and overuse of clinically relevant antibiotics in agriculture, veterinary and medical sectors contribute to the global epidemic increase in antimicrobial resistance (AMR). There is a growing concern among researchers and stakeholders that the environment acts as an AMR reservoir and plays a key role in the dissemination of antimicrobial resistance genes (ARGs). Various drivers are contributing factors to the spread of antibiotic-resistant bacteria and their ARGs either directly through antimicrobial drug use in health care, agriculture/livestock and the environment or antibiotic residues released from various domestic settings. Resistant micro-organisms and their resistance genes enter the soil, air, water and sediments through various routes or hotspots such as hospital wastewater, agricultural waste or wastewater treatment plants. Global mitigation strategies primarily involve the identification of high-risk environments that are responsible for the evolution and spread of resistance. Subsequently, AMR transmission is affected by the standards of infection control, sanitation, access to clean water, access to assured quality antimicrobials and diagnostics, travel and migration. This review provides a brief description of AMR as a global concern and the possible contribution of different environmental drivers to the transmission of antibiotic-resistant bacteria or ARGs through various mechanisms. We also aim to highlight the key knowledge gaps that hinder environmental regulators and mitigation strategies in delivering environmental protection against AMR.

Biocide-tolerance and antibiotic-resistance in community environments and risk of direct transfers to humans: Unintended consequences of community-wide surface disinfecting during COVID-19?

During the current pandemic, chemical disinfectants are ubiquitously and routinely used in community environments, especially on common touch surfaces in public settings, as a means of controlling the virus spread. An underappreciated risk in current regulatory guidelines and scholarly discussions, however, is that the persisting input of chemical disinfectants can exacerbate the growth of biocide-tolerant and antibiotic-resistant bacteria on those surfaces and allow their direct transfers to humans. For COVID-19, the most commonly used disinfecting agents are quaternary ammonium compounds, hydrogen peroxide, sodium hypochlorite, and ethanol, which account for two-thirds of the active ingredients in current EPA-approved disinfectant products for the novel coronavirus. Tolerance to each of these compounds, which can be either intrinsic or acquired, has been observed on various bacterial pathogens. Of those, mutations and horizontal gene transfer, upregulation of efflux pumps, membrane alteration, and biofilm formation are the common mechanisms conferring biocide tolerance in bacteria. Further, the linkage between disinfectant use and antibiotic resistance was suggested in laboratory and real-life settings. Evidence showed that substantial bacterial transfers to hands could effectuate from short contacts with surrounding surfaces and further from fingers to lips. While current literature on disinfectant-induced antimicrobial resistance predominantly focuses on municipal wastes and the natural environments, in reality the community and public settings are most severely impacted by intensive and regular chemical disinfecting during COVID-19 and, due to their proximity to humans, biocide-tolerant and antibiotic-resistant bacteria emerged in these environments may pose risks of direct transfers to humans, particularly in densely populated urban communities. Here we highlight these risk factors by reviewing the most pertinent and up-to-date evidence, and provide several feasible strategies to mitigate these risks in the scenario of a prolonging pandemic.

In vitro activity of six biocides against carbapenemase-producing Klebsiella pneumoniae and presence of genes encoding efflux pumps

INTRODUCTION

Acquisition of reduced susceptibility to biocides may contribute to the dissemination of high-risk (HR) clones of carbapenemase-producing Klebsiella pneumoniae (CP-Kp). The aim of this study was (a) to determinate the activity of biocides against CP-Kp, and (b) to analyse the relationship between biocide activity and the presence of efflux pumps.

METHODS

The minimal inhibitory concentrations (MICs) of 6 biocides (sodium hypochlorite, chlorhexidine digluconate, benzalkonium chloride, povidone-iodine, ethanol and triclosan) were determined in triplicate at 25°C and 37°C in Mueller-Hinton broth (MHB) and M9 minimum medium, against 17 CP-Kp isolates representing different clones (HR and no-HR), sequence-types (STs) and carbapenemases. Efflux pumps genes were detected by whole genome sequencing (MiSeq).

RESULTS

Median MICs were slightly higher at 37°C than at 25°C (p≤0.05), except for benzalkonium chloride, triclosan and ethanol. MIC medians were much higher in MHB than in M9, except for triclosan. No significant differences were observed in the median MICs, regarding the type of clone, ST or carbapenemase; cepA, acrAB, kpnEF and oqxAB genes were detected in all isolates, whereas qacE and qacA were not detected; smvAR, and qacΔE genes were detected in 94%and 47% of isolates, respectively.

CONCLUSIONS

Triclosan, chlorhexidine digluconate, benzalkonium chloride and ethanol were the most active biocides. The activity of some biocides is affected by temperature and growth media, suggesting that standardised procedures for biocide susceptibility testing based on MIC determination are required. This activity, in terms of MICs, are not related to the type of clone, ST, carbapenemase or the presence of the efflux pump genes.

Environmental Spread of Antibiotic Resistance

Antibiotic resistance represents a global health concern. Soil, water, livestock and plant foods are directly or indirectly exposed to antibiotics due to their agricultural use or contamination. This selective pressure has acted synergistically to bacterial competition in nature to breed antibiotic-resistant (AR) bacteria. Research over the past few decades has focused on the emergence of AR pathogens in food products that can cause disease outbreaks and the spread of antibiotic resistance genes (ARGs), but One Health approaches have lately expanded the focus to include commensal bacteria as ARG donors. Despite the attempts of national and international authorities of developed and developing countries to reduce the over-prescription of antibiotics to humans and the use of antibiotics as livestock growth promoters, the selective flow of antibiotic resistance transmission from the environment to the clinic (and vice-versa) is increasing. This review focuses on the mechanisms of ARG transmission and the hotspots of antibiotic contamination resulting in the subsequent emergence of ARGs. It follows the transmission of ARGs from farm to plant and animal food products and provides examples of the impact of ARG flow to clinical settings. Understudied and emerging antibiotic resistance selection determinants, such as heavy metal and biocide contamination, are also discussed here.

Evaluation of a Biocide Used in the Biological Isolation and Containment Unit of a Veterinary Teaching Hospital

Hospital-acquired infections (HAIs) are a rising problem worldwide, and the best way of coping with them is through infection tracking and surveillance systems, combined with prevention strategies, namely efficient disinfection protocols, that employ various biocides. However, increasing reports about reductions in biocide susceptibility and the development of cross-resistance to antimicrobials emphasize the need for identifying the factors influencing biocide efficiency. In this study, 29 bacterial isolates (n = 3 E. coli, n = 2 Pseudomonas spp., n = 23 Enterococcus spp., and n = 1 Staphylococcus pseudintermedius), obtained from environmental samples collected from the Biological Isolation and Containment Unit (BICU), of the Veterinary Teaching Hospital of the Faculty of Veterinary Medicine, University of Lisbon, were tested in order to determine their antimicrobial susceptibility to various antibiotics. Thirteen of these isolates were further selected in order to determine their antimicrobial susceptibility to Virkon™ S, with and without the presence of organic matter. Afterward, seven of these isolates were incubated in the presence of sub-lethal concentrations of this formulation and, subsequently, new susceptibility profiles were determined. Fourteen of the 29 isolates (48.3%) were classified as multidrug resistant, all previously identified as enterococci. Concerning Virkon™ S's susceptibility, the Minimal Bactericidal Concentration (MBC) of this biocide regarding all isolates was at least eight times lower than the concentration regularly used, when no organic matter was present. However, when organic matter was added, MBC values rose up to 23 times. After exposure to sub-lethal concentrations of Virkon™ S, four enterococci presented a phenotypical change regarding antimicrobial susceptibility towards gentamicin. Virkon™ S also resulted in higher MBC values, up to 1.5 times, in the presence of low concentrations of organic matter, but no rise in these values was observed in assays without interfering substance. Virkon™ S seemed to be an efficient formulation in eliminating all bacteria isolates isolated from the BICU. However, organic matter could represent a hindrance to this ability, which emphasizes the importance of sanitization before disinfection procedures. The changes seen in antimicrobial susceptibility could be explained by a general stress-induced response promoted by the sub-lethal levels of Virkon™ S. Additionally, when no organic matter was present, a decrease in susceptibility to this biocide seemed to be non-existent.

Biocidal Resistance in Clinically Relevant Microbial Species: A Major Public Health Risk

Antimicrobial resistance is one of the greatest dangers to public health of the 21st century, threatening the treatment and prevention of infectious diseases globally. Disinfection, the elimination of microbial species via the application of biocidal chemicals, is essential to control infectious diseases and safeguard animal and human health. In an era of antimicrobial resistance and emerging disease, the effective application of biocidal control measures is vital to protect public health. The COVID-19 pandemic is an example of the increasing demand for effective biocidal solutions to reduce and eliminate disease transmission. However, there is increasing recognition into the relationship between biocide use and the proliferation of Antimicrobial Resistance species, particularly multidrug-resistant pathogens. The One Health approach and WHO action plan to combat AMR require active surveillance and monitoring of AMR species; however, biocidal resistance is often overlooked. ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens and numerous fungal species have demonstrated drug and biocidal resistance where increased patient mortality is a risk. Currently, there is a lack of information on the impact of biocide application on environmental habitats and ecosystems. Undoubtedly, the excessive application of disinfectants and AMR will merge to result in secondary disasters relating to soil infertility, loss of biodiversity and destruction of ecosystems.

Screening of Concentration and Antimicrobial Effectiveness of Antimicrobial Preservative in Betastatin Besylate Nasal Spray

Objective

To explore the optimal concentration and antimicrobial effectiveness of antimicrobial preservative in betastatin besylate nasal spray.

Methods

By using Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, and Aspergillus niger as test strains, the antimicrobial effectiveness of betastatin besylate nasal spray containing different concentrations of antimicrobial preservative (0.02%, 0.0125%, and 0.005% benzalkonium chloride, respectively) was determined by using bacteriostatic effect test (Chinese Pharmacopoeia, 2015 edition).

Results

The antimicrobial effectiveness of betastatin besylate nasal spray containing 0.02% and 0.0125% benzalkonium chloride, respectively, complied with the regulations of Chinese Pharmacopoeia (2015 Edition) against five test strains. However, the antimicrobial effectiveness of betastatin besylate nasal spray containing 0.005% benzalkonium chloride against P. aeruginosa did not meet the requirements of Chinese Pharmacopoeia.

Conclusion

Benzalkonium chloride at a concentration of 0.125% can be used as an added antimicrobial preservative in betastatin besylate nasal spray.

Effect of Exposure to Chlorhexidine Residues at "During Use" Concentrations on Antimicrobial Susceptibility Profile, Efflux, Conjugative Plasmid Transfer, and Metabolism of Escherichia coli

There is no standardized protocol to predict the concentration levels of microbicides that are left on surfaces as a result of the use of these products, and there is no standardized method to predict the potential risk that such levels pose to emerging antibacterial resistance. The ability to distinguish between selection and adaption processes for antimicrobial resistance in bacteria and the impact of different concentrations of microbicide exposure have not been fully investigated to date. This study considers the effect of exposure to a low concentration of chlorhexidine digluconate (CHX) on selected phenotypes of Escherichia coli and relates the findings to the risk of emerging antimicrobial resistance. A concentration of 0.006 mg/ml CHX is a realistic "during use" exposure concentration measured on surfaces. At this concentration, it was possible for CHX-susceptible bacteria to survive, adapt through metabolic alterations, exhibit a transient decrease in antimicrobial susceptibility, and express stable clinical cross-resistance to front-line antibiotics. Efflux activity was present naturally in tested isolates, and it increased in the presence of 0.00005 mg/ml CHX but ceased with 0.002 mg/ml CHX. Phenotypic microarray assays highlighted a difference in metabolic regulation at 0.00005 mg/ml and 0.002 mg/ml CHX; more changes occurred after growth with the latter concentration. Metabolic phenotype changes were observed for substrates involved with the metabolism of some amino acids, cofactors, and secondary metabolites. It was possible for one isolate to continue transferring ampicillin resistance in the presence of 0.00005 mg/ml CHX, whilst 0.002 mg/ml CHX prevented conjugative transfer. In conclusion, E. coli phenotype responses to CHX exposure are concentration dependent, with realistic residual CHX concentrations resulting in stable clinical cross-resistance to antibiotics.

Reducing antibiotic prescribing and addressing the global problem of antibiotic resistance by targeted hygiene in the home and everyday life settings: A position paper

Antimicrobial resistance (AMR) continues to threaten global health. Although global and national AMR action plans are in place, infection prevention and control is primarily discussed in the context of health care facilities with home and everyday life settings barely addressed. As seen with the recent global SARS-CoV-2 pandemic, everyday hygiene measures can play an important role in containing the threat from infectious microorganisms. This position paper has been developed following a meeting of global experts in London, 2019. It presents evidence that home and community settings are important for infection transmission and also the acquisition and spread of AMR. It also demonstrates that the targeted hygiene approach offers a framework for maximizing protection against colonization and infections, thereby reducing antibiotic prescribing and minimizing selection pressure for the development of antibiotic resistance. If combined with the provision of clean water and sanitation, targeted hygiene can reduce the circulation of resistant bacteria in homes and communities, regardless of a country's Human Development Index (overall social and economic development). Achieving a reduction of AMR strains in health care settings requires a mirrored reduction in the community. The authors call upon national and international policy makers, health agencies, and health care professionals to further recognize the importance of targeted hygiene in the home and everyday life settings for preventing and controlling infection, in a unified quest to tackle AMR.

Evaluation of a Newly Developed Vacuum Dried Microtiter Plate for Rapid Biocide Susceptibility Testing of Clinical Enterococcus Faecium Isolates

We investigated the suitability of a newly developed biocide susceptibility test system based on microtiter plates containing vacuum dried biocides as a fast and reliable screening method. The evaluated substances included the cationic biocides benzalkonium chloride (BAC), chlorhexidine dihydrochloride (CHX), cetylpyridinium chloride, didecyldimethylammonium chloride, and octenidine dihydrochloride. Testing a selection of Escherichia coli and enterococci, the biocide microtiter plates provided results comparable to those obtained from broth microdilution according to ISO 20776-1. Broad MIC ranges allowed for testing gram-positive and gram-negative species with the same plate design. In the second part of our study, we applied the established method to analyze the susceptibility of 90 clinical Enterococcus faecium isolates from a German university hospital, as previous studies have indicated a link between reduced susceptibility to substances such as CHX and BAC and vancomycin resistance. We therefore determined MIC and minimum bactericidal concentrations (MBC) for 48 non-clonal vancomycin susceptible and 42 non-clonal vancomycin resistant isolates, but MIC95 and MBC95 were quite similar in both groups. Our easy to handle and ready to use test system enables the routine surveillance of bacterial tolerance towards disinfectants in hospitals. As a result, hygiene measures can be adapted and nosocomial infections controlled despite increasing prevalence of antibiotic-resistant bacteria.

Hydroxyethoxy phenyl butanone, a new cosmetic preservative, does not cause bacterial cross-resistance to antimicrobials

Introduction.

Biocide-induced cross-resistance to antimicrobials in bacteria has been described and is a concern for regulators. We have recently reported on a new protocol to predict the propensity of biocide to induce phenotypic resistance in bacteria.

Aim.

To measure bacterial propensity to develop antimicrobial resistance following exposure to a new cosmetic preservative developed by L’Oréal R and I.

Methodology.

Well-established antimicrobials including triclosan (TRI) and benzalkonium chloride (BZC) and a new molecule hydroxyethoxy phenyl butanone (HEPB) were investigated for their antimicrobial efficacy, effect on bacterial growth, and their potential to induce resistance to chemotherapeutic antibiotics using a new predictive protocol.

Results.

The use of this predictive protocol with Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa showed that TRI and BZC significantly affected bacterial growth, MICs and minimum bactericidal concentrations (MBCs). There was no change in antibiotic susceptibility profile following exposure to BZC, but E. coli became intermediate resistant to tobramycin following treatment with TRI (0.00002 % w/v). HEPB did not change the antimicrobial susceptibility profile in P. aeruginosa and S. aureus but E. coli became susceptible to gentamicin. TRI exposure resulted in bacterial susceptibility profile alteration consistent with the literature and confirmed the use of TRI as a positive control in such a test.

Conclusion.

Data produced on the propensity of a molecule to induce bacterial resistance is useful and appropriate when launching a new preservative.

Intracellular Behaviour of Three Legionella pneumophila Strains within Three Amoeba Strains, Including Willaertia magna C2c Maky

Legionella pneumophila is a facultative intracellular pathogen found in aquatic environments as planktonic cells within biofilms and as intracellular parasites of free-living amoebae such as Acanthamoeba castellanii. This pathogen bypasses the elimination mechanism to replicate within amoebae; however, not all amoeba species support the growth of L. pneumophila. Willaertia magna C2c Maky, a non-pathogenic amoeba, was previously demonstrated to possess the ability to eliminate the L. pneumophila strain Paris. Here, we study the intracellular behaviour of three L. pneumophila strains (Paris, Philadelphia, and Lens) within W. magna C2c Maky and compare this strain to A. castellanii and W. magna Z503, which are used as controls. We observe the intracellular growth of strain Lens within W. magna Z503 and A. castellanii at 22 °C and 37 °C. Strain Paris grows within A. castellanii at any temperature, while it only grows at 22 °C within W. magna Z503. Strain Philadelphia proliferates only within A. castellanii at 37 °C. Within W. magna C2c Maky, none of the three legionella strains exhibit intracellular growth. Additionally, the ability of W. magna C2c Maky to decrease the number of internalized L. pneumophila is confirmed. These results support the idea that W. magna C2c Maky possesses unique behaviour in regard to L. pneumophila strains.

Occurrence and Characteristics of Mobile Colistin Resistance (mcr) Gene-Containing Isolates from the Environment: A Review

The emergence and spread of mobile colistin (COL) resistance (mcr) genes jeopardize the efficacy of COL, a last resort antibiotic for treating deadly infections. COL has been used in livestock for decades globally. Bacteria have mobilized mcr genes (mcr-1 to mcr-9). Mcr-gene-containing bacteria (MGCB) have disseminated by horizontal/lateral transfer into diverse ecosystems, including aquatic, soil, botanical, wildlife, animal environment, and public places. The mcr-1, mcr-2, mcr-3, mcr-5, mcr-7, and mcr-8 have been detected in isolates from and/or directly in environmental samples. These genes are harboured by Escherichia coli, Enterobacter, Klebsiella, Proteus, Salmonella, Citrobacter, Pseudomonas, Acinetobacter, Kluyvera, Aeromonas, Providencia, and Raulotella isolates. Different conjugative and non-conjugative plasmids form the backbones for mcr in these isolates, but mcr have also been integrated into the chromosome of some strains. Insertion sequences (IS) (especially ISApl1) located upstream or downstream of mcr, class 1–3 integrons, and transposons are other drivers of mcr in the environment. Genes encoding multi-/extensive-drug resistance and virulence are often co-located with mcr on plasmids in environmental isolates. Transmission of mcr to/among environmental strains is clonally unrestricted. Contact with the mcr-containing reservoirs, consumption of contaminated animal-/plant-based foods or water, international animal-/plant-based food trades and travel, are routes for transmission of MGCB.