Is reduced susceptibility to disinfectants and antiseptics a risk in healthcare settings? A point/counterpoint review

Development of a Broth Microdilution Method To Characterize Chlorhexidine MICs among Bacteria Collected from 2005 to 2019 at Three U.S. Sites

Chlorhexidine bathing to prevent transmission of multidrug-resistant organisms has been adopted by many U.S. hospitals, but increasing chlorhexidine use has raised concerns about possible emergence of resistance. We sought to establish a broth microdilution method for determining chlorhexidine MICs and then used the method to evaluate chlorhexidine MICs for bacteria that can cause health care-associated infections. We adapted a broth microdilution method for determining chlorhexidine MICs, poured panels, established quality control ranges, and tested Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae complex isolates collected at three U.S. sites. Chlorhexidine MICs were determined for 535 isolates including 129 S. aureus, 156 E. coli, 142 K. pneumoniae, and 108 E. cloacae complex isolates. The respective MIC distributions for each species ranged from 1 to 8 mg/L (MIC50 = 2 mg/L and MIC90 = 4 mg/L), 1 to 64 mg/L (MIC50 = 2 mg/L and MIC90 = 4 mg/L), 4 to 64 mg/L (MIC50 = 16 mg/L and MIC90 = 32 mg/L), and 1 to >64 mg/L (MIC50 = 16 mg/L and MIC90 = 64 mg/L). We successfully adapted a broth microdilution procedure that several laboratories were able to use to determine the chlorhexidine MICs of bacterial isolates. This method could be used to investigate whether chlorhexidine MICs are increasing. IMPORTANCE Chlorhexidine bathing to prevent transmission of multidrug-resistant organisms and reduce health care-associated infections has been adopted by many hospitals. There is concern about the possible unintended consequences of using this agent widely. One possible unintended consequence is decreased susceptibility to chlorhexidine, but there are not readily available methods to perform this evaluation. We developed a method for chlorhexidine MIC testing that can be used to evaluate for possible unintended consequences.

Bacterial Cross-Transmission between Inanimate Surfaces and Patients in Intensive Care Units under Real-World Conditions: A Repeated Cross-Sectional Study

Background/Objectives: Contaminated surfaces play an important role in the nosocomial infection of patients in intensive care units (ICUs). This study, conducted in two ICUs at Edouard Herriot Hospital (Lyon, France), aimed to describe rooms' microbial ecology and explore the potential link between environmental contamination and patients' colonization and/or infection. Methods: Environmental samples were realized once monthly from January 2020 to December 2021 on surfaces close to the patient (bedrails, bedside table, and dedicated stethoscope) and healthcare workers' high-touch surfaces, which were distant from the patient (computer, worktop/nurse cart, washbasin, and hydro-alcoholic solution/soap dispenser). Environmental bacteria were compared to the cultures of the patients hospitalized in the sampled room over a period of ± 10 days from the environmental sampling. Results: Overall, 137 samples were collected: 90.7% of the samples close to patients, and 87.9% of the distant ones were positives. Overall, 223 bacteria were isolated, mainly: Enterococcus faecalis (15.7%), Pantoea agglomerans (8.1%), Enterobacter cloacae/asburiae (6.3%), Bacillus cereus and other Bacillus spp (6.3%), Enterococcusfaecium (5.8%), Stenotrophomonas maltophilia (5.4%), and Acinetobacter baumannii (4.9%). Throughout the study, 142 patients were included, of which, n = 67 (47.2%) were infected or colonized by at least one bacterium. In fourteen cases, the same bacterial species were found both in environment and patient samples, with the suspicion of a cross-contamination between the patient-environment (n = 10) and environment-patient (n = 4). Conclusions: In this work, we found a high level of bacterial contamination on ICU rooms' surfaces and described several cases of potential cross-contamination between environment and patients in real-world conditions.

Phenotype and genetic determination of resistance to common disinfectants among biofilm-producing and non-producing Pseudomonas aeruginosa strains from clinical specimens in Iran

BACKGROUND

Pseudomonas aeruginosa is a common pathogen in Hospitalized patients, and its various resistance mechanisms contribute to patient morbidity and mortality. The main aims of the present study were to assess the susceptibility of biofilm-producing and non-producing P. aeruginosa isolates to the five commonly used Hospital disinfectants, to evaluate the synergistic effect of selected disinfectants and Ethylene-diamine-tetra acetic acid (EDTA), and the effect of exposure to sub-inhibitory concentrations of Sodium hypochlorite on antimicrobial susceptibility test.

RESULTS

The results showed that sodium hypochlorite 5% and Ethanol 70% were the most and least effective disinfectants against P. aeruginosa, respectively. The addition of EDTA significantly increased the effectiveness of the selected disinfectants. The changes in the antibiotic-resistance profiles after exposure to sub-inhibitory concentrations of disinfectants were observed for different classes of antibiotics (Carbapenems, Aminoglycosides, Cephalosporins, Fluoroquinolones). As well as near the all isolates harbored efflux pump genes and 117 (97.5%) of isolates produced biofilm.

CONCLUSION

In the current study, the mixture of disinfectant and EDTA were the most suitable selection to disinfect Hospital surfaces and instruments. Also, it was clear that exposure to sub-inhibitory concentrations of Sodium hypochlorite results in resistance to some antibiotics in P. aeruginosa species. Strong and intermediate biofilm formers belonged to MDR/XDR strains. Future studies should include more complex microbial communities residing in the Hospitals, and more disinfectants use in Hospitals.

Resisting disinfectants

van Dijk et al. discuss the potential for antimicrobial resistance as a consequence of disinfectant use. The authors advocate for the prudent use of disinfectants in all sectors of society.

Application of Whole Genome Sequencing to Aid in Deciphering the Persistence Potential of Listeria monocytogenes in Food Production Environments

Listeria monocytogenes is the etiological agent of listeriosis, a foodborne illness associated with high hospitalizations and mortality rates. This bacterium can persist in food associated environments for years with isolates being increasingly linked to outbreaks. This review presents a discussion of genomes of Listeria monocytogenes which are commonly regarded as persisters within food production environments, as well as genes which are involved in mechanisms aiding this phenotype. Although criteria for the detection of persistence remain undefined, the advent of whole genome sequencing (WGS) and the development of bioinformatic tools have revolutionized the ability to find closely related strains. These advancements will facilitate the identification of mechanisms responsible for persistence among indistinguishable genomes. In turn, this will lead to improved assessments of the importance of biofilm formation, adaptation to stressful conditions and tolerance to sterilizers in relation to the persistence of this bacterium, all of which have been previously associated with this phenotype. Despite much research being published around the topic of persistence, more insights are required to further elucidate the nature of true persistence and its implications for public health.

Disinfectant resistance in bacteria: Mechanisms, spread, and resolution strategies

Disinfectants are widely acknowledged for removing microorganisms from the surface of the objects and transmission media. However, the emergence of disinfectant resistance has become a severe threat to the safety of life and health and the rational allocation of resources due to the reduced disinfectant effectiveness. The horizontal gene transfer (HGT) of disinfectant resistance genes has also expanded the resistant flora, making the situation worse. This review focused on the resistance mechanisms of disinfectant resistant bacteria on biofilms, cell membrane permeability, efflux pumps, degradable enzymes, and disinfectant targets. Efflux can be the fastest and most effective resistance mechanism for bacteria to respond to stress. The qac genes, located on some plasmids which can transmit resistance through conjugative transfer, are the most commonly reported in the study of disinfectant resistance genes. Whether the qac genes can be transferred through transformation or transduction is still unclear. Studying the factors affecting the resistance of bacteria to disinfectants can find breakthrough methods to more adequately deal with the problem of reduced disinfectant effectiveness. It has been confirmed that the interaction of probiotics and bacteria or the addition of 4-oxazolidinone can inhibit the formation of biofilms. Chemicals such as eugenol and indole derivatives can increase bacterial sensitivity by reducing the expression of efflux pumps. The role of these findings in anti-disinfectant resistance has proved invaluable.

The antiseptic Miramistin: a review of its comparative in vitro and clinical activity

Miramistin is a topical antiseptic with broad antimicrobial action, including activity against biofilms and a clinical profile showing good tolerability. Miramistin was developed within a framework of the Soviet Union Cold War Space Program. It is available for clinical use in several prior Soviet bloc countries, but barely known outside of these countries and there is almost no mention of miramistin in the English literature. However, considering emerging antimicrobial resistance, the significant potential of miramistin justifies its re-evaluation for use in other geographical areas and conditions. The review consists of two parts: (i) a review of the existing literature on miramistin in English, Russian and Ukrainian languages; (ii) a summary of most commonly used antiseptics as comparators of miramistin. The oral LD50 was 1200 mg/kg, 1000 mg/kg and 100 g/L in rats, mice and fish, respectively. Based on the results of the review, we suggest possible applications of miramistin and potential benefits over currently used agents. Miramistin offers a novel, low toxicity antiseptic with many potential clinical uses that need better study which could address some of the negative impact of antimicrobial, antiseptic and disinfectant resistance.

Mutant Strains of Escherichia coli and Methicillin-Resistant Staphylococcus aureus Obtained by Laboratory Selection To Survive on Metallic Copper Surfaces

Artificial laboratory evolution was used to produce mutant strains of Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) able to survive on antimicrobial metallic copper surfaces. These mutants were 12- and 60-fold less susceptible to the copper-mediated contact killing process than their respective parent strains. Growth levels of the mutant and its parent in complex growth medium were similar. Tolerance to copper ions of the mutants was unchanged. The mutant phenotype remained stable over about 250 generations under nonstress conditions. The mutants and their respective parental strains accumulated copper released from the metallic surfaces to similar extents. Nevertheless, only the parental strains succumbed to copper stress when challenged on metallic copper surfaces, suffering complete destruction of the cell structure. Whole-genome sequencing and global transcriptome analysis were used to decipher the genetic alterations in the mutant strains; however, these results did not explain the copper-tolerance phenotypes on the systemic level. Instead, the mutants shared features with those of stressed bacterial subpopulations entering the early or "shallow" persister state. In contrast to the canonical persister state, however, the ability to survive on solid copper surfaces was adopted by the majority of the mutant strain population. This indicated that application of solid copper surfaces in hospitals and elsewhere has to be accompanied by strict cleaning regimens to keep the copper surfaces active and prevent evolution of tolerant mutant strains.IMPORTANCE Microbes are rapidly killed on solid copper surfaces by contact killing. Copper surfaces thus have an important role to play in preventing the spread of nosocomial infections. Bacteria adapt to challenging natural and clinical environments through evolutionary processes, for instance, by acquisition of beneficial spontaneous mutations. We wish to address the question of whether mutants can be selected that have evolved to survive contact killing on solid copper surfaces. We isolated such mutants from Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) by artificial laboratory evolution. The ability to survive on solid copper surfaces was a stable phenotype of the mutant population and not restricted to a small subpopulation. As a consequence, standard operation procedures with strict hygienic measures are extremely important to prevent the emergence and spread of copper-surface-tolerant persister-like bacterial strains if copper surfaces are to be sustainably used to limit the spread of pathogenic bacteria, e.g., to curb nosocomial infections.

Decolonization of Staphylococcus aureus

Staphylococcus aureus infections are associated with increased morbidity, mortality, hospital stay, and health care costs. S aureus colonization has been shown to increase risk for invasive and noninvasive infections. Decolonization of S aureus has been evaluated in multiple patient settings as a possible strategy to decrease the risk of S aureus transmission and infection. In this article, we review the recent literature on S aureus decolonization in surgical patients, patients with recurrent skin and soft tissue infections, critically ill patients, hospitalized non-critically ill patients, dialysis patients, and nursing home residents to inform clinical practice.

Evaluation of 1,2-Benzothiazine 1,1-dioxide Derivatives In Vitro Activity towards Clinical-Relevant Microorganisms and Fibroblasts

The global concern related with growing number of bacterial pathogens, resistant to numerous antibiotics, prone scientific environment to search for new antimicrobials. Antiseptics appear to be suitable candidates as adjunctive agents to antibiotics or alternative local treatment option aiming to prevent and treat infections. 1,2-benzothiazines are considered one the most promising of them. In this research twenty 1,2-benzothiazine 1,1-dioxide derivatives were scrutinized with regard to their biological activity. Three of them are new. For evaluation of compounds' activity against microbial pathogens, disk diffusion method and serial microdilution method was applied. To establish the cytotoxicity profile of tested 1,2-benzothiazines 1,1-dioxides derivatives, the cytotoxicity assay using fibroblasts L292 was performed. Antimicrobial activity of all tested compounds against Gram-positive Staphylococcus aureus and Enterococcus faecalis strains was higher than antimicrobial activity of DMSO solvent, which possesses antimicrobial activity itself. Gram-negative P. aeruginosa, E. coli and K. pneumoniae have shown susceptibility only to compounds 3e, 7i and 7l. None of tested compounds was effective against C. albicans. Compound 6g has demonstrated the strongest antimicrobial potency (MIC = 0.00975 mg/mL) among compounds of series 6. Compounds of series 7, namely 7d, 7f, 7g had the lowest minimum inhibitory concentration (MIC). Compound 7f displayed also the lowest cytotoxic effect against fibroblast cell line among series 7 compounds. All tested derivatives displayed lower MIC against Gram-positive bacteria than commercially applied antiseptic, povidone iodine, which MIC value range for tested Gram-positive bacteria was 1.56-6.25 mg/mL.

Short- and Long-Term Transcriptomic Responses of Escherichia coli to Biocides: a Systems Analysis

The mechanisms of the bacterial response to biocides are poorly understood, despite their broad application. To identify the genetic basis and pathways implicated in the biocide stress response, we exposed Escherichia coli populations to 10 ubiquitous biocides. By comparing the transcriptional responses between a short-term exposure (30 min) and a long-term exposure (8 to 12 h) to biocide stress, we established the common gene and pathway clusters that are implicated in general and biocide-specific stress responses. Our analysis revealed a temporal choreography, starting from the upregulation of chaperones to the subsequent repression of motility and chemotaxis pathways and the induction of an anaerobic pool of enzymes and biofilm regulators. A systematic analysis of the transcriptional data identified a zur-regulated gene cluster to be highly active in the stress response against sodium hypochlorite and peracetic acid, presenting a link between the biocide stress response and zinc homeostasis. Susceptibility assays with knockout mutants further validated our findings and provide clear targets for downstream investigation of the implicated mechanisms of action.IMPORTANCE Antiseptics and disinfectant products are of great importance to control and eliminate pathogens, especially in settings such as hospitals and the food industry. Such products are widely distributed and frequently poorly regulated. Occasional outbreaks have been associated with microbes resistant to such compounds, and researchers have indicated potential cross-resistance with antibiotics. Despite that, there are many gaps in knowledge about the bacterial stress response and the mechanisms of microbial resistance to antiseptics and disinfectants. We investigated the stress response of the bacterium Escherichia coli to 10 common disinfectant and antiseptic chemicals to shed light on the potential mechanisms of tolerance to such compounds.

Hyper-expression of the efflux pump gene adeB was found in Acinetobacter baumannii with decreased triclosan susceptibility

OBJECTIVES

Triclosan is usually employed as a disinfectant in a wide range of medical and consumer care products, which may have imposed a selective pressure on bacteria. This study was designed to evaluate the resistance mechanisms of triclosan and molecular epidemiology of triclosan-resistant isolates of Acinetobacter baumannii in Wenzhou, China.

METHODS

A collection of 626 A. baumannii were isolated from the First Affiliated Hospital of Wenzhou Medical University during 2016-2017 and antimicrobial susceptibility testing of these isolates were performed via agar dilution method. Molecular mechanisms of triclosan resistance, including the existence of mutations in reductase (FabI) were investigated by PCR and sequencing. Furthermore, quantitative RT-PCR was conducted to evaluate the expression levels of the fabI gene and efflux pump genes (adeB, adeG, adeJ, abeM, amvA and abeS) at normal condition and sub-inhibitory concentration of triclosan, and the epidemiological characteristics were analyzed by PFGE and MLST.

RESULTS

2.7% (17/626) of A. baumannii exhibited resistance to triclosan. The FabI mutation Gly95Ser was found in one triclosan resistant strain. The expression of fabI and adeB gene were significant difference between triclosan-resistant and susceptible strains (P < 0.05). The expression of fabI, adeG, adeJ and abeM were increased after triclosan induction. The clones of these resistant isolates were diverse and sporadic.

CONCLUSIONS

The hyper-expression of fabI was probably the main mechanism of triclosan resistance in this study, and the efflux pump AdeB, AdeG, AdeJ and AbeM might also be related to decreased triclosan susceptibility.

Determining the susceptibility of carbapenem resistant Klebsiella pneumoniae and Escherichia coli strains against common disinfectants at a tertiary hospital in China

Background

Carbapenem-resistant Enterobacteriaceae (CRE) infections have become a global health threat. Controlling CRE transmission in hospitals is increasingly dependent on the use of disinfectants to restrict the risk of infection. Here, the susceptibility of patient-derived carbapenem resistant Klebsiella pneumoniae (CRKP) and Escherichia coli (CREC) strains against three common disinfectants and the determinants of resistance to disinfectants were investigated.

Methods

The minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of three common chemical disinfectants: chlorhexidine, trichloroisocyanuric (TCCA) acid and Povidone iodine (PVP-I) against 50 CRE strains were measured. The drug-resistance genes -qacEΔ1, qacA/B and cepA-were determined using polymerase chain reaction.

Results

A total of 36 CRKP and 14 CREC strains were collected in our hospital from 2016 to 2018. The MIC ranges of 36 CRKP strains against chlorhexidine, TCCA and PVP-I were 8~512 mg/L, 64~128 mg/L and 8~128 mg/L, respectively. For 14 CREC strains, the MIC ranges against chlorhexidine, TCCA and PVP-I were 4~128 mg/L, 64~128 mg/L and 4~128 mg/L, respectively. Moreover, against chlorhexidine and PVP-I, the MIC₉₀ of 36 CRKP strains was higher than that of 50 CSKP strains. The qacE△1 gene was detected in 15 isolates among 36 CRKP strains (41.7%), and 8 isolates among 14 CREC strains (57.1%); while the qacA/B gene was not detected. Specifically, the cepA gene was much more prevalent than the qacEΔ1; it reached over 80% among CRKP strains. Compared to the CSKP strains, the presence of the qacEΔ1 and cepA genes was significantly higher among the CRKP strains (p < 0.05).

Conclusion

CRE strains collected from patients in our hospital exhibit various degree of resistance to the commonly used chemical disinfectants. It is of great help to keep monitoring the tendency of the reduced susceptibility of the pan-resistant strains against disinfectants, in order to effectively control and prevent the spread of the super resistant bacteria.

Molecular mechanism of antimicrobial activity of chlorhexidine against carbapenem-resistant Acinetobacter baumannii

Acinetobacter baumannii causes hospital-acquired infections, especially in those with impaired immune function. Biocides or disinfectants are widely used antibacterial agents used to eradicate the effect of A. baumannii on inanimate objects and health care environments. In the current study, the antimicrobial activity of chlorhexidine has been investigated against carbapenem-resistant (RS-307, RS-7434, RS-6694, and RS-122), and sensitive (ATCC-19606 and RS-10953) strains of A. baumannii. We have determined growth kinetics, antimicrobial susceptibility, ROS production, lipid peroxidation, cell viability using flow cytometry assay (FACS), and membrane integrity by scanning electron microscope (SEM). The effect of chlorhexidine on the bacterial membrane has also been investigated using Fourier transform infrared (FTIR) spectroscopy. The present study showed that 32μg/ml chlorhexidine treatment results in the decreased bacterial growth, CFU count and cell viability. The antibacterial activity of chlorhexidine is due to the elevated ROS production and higher lipid peroxidation. These biochemical changes result in the membrane damage and alteration in the membrane proteins, phospholipids, carbohydrates, nucleic acids as evident from the FTIR and SEM data. Therefore, chlorhexidine has the potential to be used in the hospital setups to remove the spread of A. baumannii.

De-repression of the smvA efflux system arises in clinical isolates of Proteus mirabilis and reduces susceptibility to chlorhexidine and other biocides

Proteus mirabilis is a common pathogen of the catheterised urinary tract and often described as intrinsically resistant to the biocide chlorhexidine (CHD). Here we demonstrate that de-repression of the smvA efflux system has occurred in clinical isolates of P. mirabilis and reduces susceptibility to CHD and other cationic biocides. Compared to other isolates examined, P. mirabilis RS47 exhibited a significantly higher CHD MIC (≥512 μg/ml) and significantly greater expression of smvA. Comparison of the RS47 smvA and cognate smvR repressor with sequences from other isolates, indicated that RS47 encodes an inactivated smvR. Complementation of RS47 with a functional smvR from isolate RS50a (which exhibited the lowest smvA expression and lowest CHD MIC) reduced smvA expression by ∼59-fold, and markedly lowered the MIC of CHD and other cationic biocides. Although complementation of RS47 did not reduce MICs to concentrations observed in isolate RS50a, the significantly lower polymyxin B MIC of RS50a indicated that differences in LPS structure are also a factor in P. mirabilis CHD susceptibility. To determine if exposure to CHD can select for mutations in smvR, clinical isolates with the lowest CHD MICs were adapted to grow at increasing concentrations of CHD up to 512 μg/ml. Analysis of the smvR in adapted populations indicated that mutations predicted to inactivate smvR occurred following CHD exposure in some isolates. Collectively, our data show that smvA de-repression contributes to reduced biocide susceptibility in P. mirabilis, but differences in LPS structure between strains are also likely to be an important factor.

Use of germicides in health care settings-is there a relationship between germicide use and antimicrobial resistance: A concise review

Despite the widespread use of disinfectants and antiseptics in hospitals, acquired resistance to current disinfectants has rarely been reported. Germicides, as with medications, should only be used when their benefit as demonstrated by scientific studies exceeds possible risks to human health or the environment.

SmvA is an important efflux pump for cationic biocides in Klebsiella pneumoniae and other Enterobacteriaceae

The multidrug resistant (MDR) opportunistic pathogen Klebsiella pneumoniae has previously been shown to adapt to chlorhexidine by increasing expression of the MFS efflux pump smvA. Here we show that loss of the regulator SmvR, through adaptation to chlorhexidine, results in increased resistance to a number of cationic biocides in K. pneumoniae and other members of the Enterobacteriaceae. Clinical Enterobacteriaceae isolates which lack smvA and smvR also have an increased susceptibility to chlorhexidine. When smvA from Salmonella and K. pneumoniae are expressed in Escherichia coli, which lacks a homologue to SmvAR, resistance to chlorhexidine increased (4-fold) but plasmid carriage of smvA alone was detrimental to the cell. Challenge of K. pneumoniae with chlorhexidine and another cationic biocide, octenidine, resulted in increased expression of smvA (approx. 70 fold). Adaptation to octenidine was achieved through mutating key residues in SmvA (A363V; Y391N) rather than abolishing the function of SmvR, as with chlorhexidine adaptation. Molecular modelling was able to predict that octenidine interacted more strongly with these mutated SmvA forms. These results show that SmvA is a major efflux pump for cationic biocides in several bacterial species and that increased efflux through SmvA can lead to increased chlorhexidine and octenidine tolerance.

Surgical field and skin preparation

Surgical site infection (SSI) is the third most frequent healthcare-associated infection in France. SSI rates in total hip or knee replacement are around 2%. The main bacteria implicated in SSI in clean surgery are those of the skin flora, whence the importance of skin preparation to eliminate transient flora and reduce resident flora. Guidelines for the prevention of SSI have progressed in recent years in France: firstly in 2013, and then in 2016. That preoperative hair removal and scrubbing of clean skin ahead of cutaneous asepsis is non-contributive was confirmed in 2013. A shower with normal soap taken as close to the beginning of surgery as possible is still recommended, as is use of alcoholic antiseptics for cutaneous asepsis. The debate remains open between chlorhexidine and povidone-iodine in several surgical specialties in the absence of any multicenter studies. Future choices of antiseptic may need to take account of resistance, especially to chlorhexidine, and possible side-effects. Finally, antimicrobial skin sealants and adhesive surgical drapes are not recommended for the prevention of infection.

Antimicrobial Resistance in Listeria Species

For nearly a century the use of antibiotics to treat infectious diseases has benefited human and animal health. In recent years there has been an increase in the emergence of antibiotic-resistant bacteria, in part attributed to the overuse of compounds in clinical and farming settings. The genus Listeria currently comprises 17 recognized species found throughout the environment. Listeria monocytogenes is the etiological agent of listeriosis in humans and many vertebrate species, including birds, whereas Listeria ivanovii causes infections mainly in ruminants. L. monocytogenes is the third-most-common cause of death from food poisoning in humans, and infection occurs in at-risk groups, including pregnant women, newborns, the elderly, and immunocompromised individuals.

Surface-attached sulfonamide containing quaternary ammonium antimicrobials for textiles and plastics

With the risks associated with healthcare-associated infections and the rise of antibiotic resistant microorganisms, there is an important need to control the proliferation of these factors in hospitals, retirement homes and other institutions. This work explores the development and application of a novel class of sulfonamide-based quaternary ammonium antimicrobial coatings, anchored to commercially and clinically relevant material surfaces. Synthesized in high yields (60–97%), benzophenone-anchored antimicrobials were spray-coated and UV grafted onto plastic surfaces, while silane-anchored variants were adhered to select textiles via dip-coating. Surface modified samples were characterised by advancing contact angle, anionic dye staining, X-ray photoelectron spectroscopy and atomic force microscopy. After verifying coating quality through the above characterization methods, microbiological testing was performed on batch samples in conditions that simulate the natural inoculation of surfaces and objects (solid/air) and water containers (solid/liquid). Using the previously established Large Drop Inoculum (LDI) protocol at solid/air interfaces, all treated samples showed a full reduction (10⁵–10⁷ CFU) of viable Arthrobacter sp., S. aureus, and E. coli after 3 h of contact time. Additional testing of the walls of plastic LDPE vials treated with a UV-cured sulfonamide antimicrobial at a solid/liquid interface using the newly developed Large Reservoir Inoculum (LRI) protocol under static conditions revealed a complete kill (>10⁶ reduction) of Gram-positive Arthrobacter sp., and a partial kill (>10⁴ reduction) of Gram-negative E. coli within 24–48 h of contact.

A series of surface attached silane or benzophenone sulfonamide quaternary ammonium antimicrobials show potent efficacy at solid/air and solid/liquid interfaces.

Tolerance of MRSA ST239-TW to chlorhexidine-based decolonization: Evidence for keratinocyte invasion as a mechanism of biocide evasion

OBJECTIVES

Information on genetic determinants of chlorhexidine tolerance (qacA carriage and MIC) in vitro is available, although evidence of the clinical impact and mechanisms remain poorly understood. We investigated why, following chlorhexidine intervention, prevalent epidemic MRSA ST22 and ST36 clones declined at an ICU, whilst an ST239-TW clone did not. The chlorhexidine tolerant ST239-TW phenotypes were assessed for their protein binding, cell adhesion and intracellular uptake potential.

METHODS

Six ST22, ST36 and ST239-TW bloodstream infection isolates with comparable chlorhexidine MICs were selected from a 2-year outbreak in an ICU at Guy's and St. Thomas' Hospital. Isolates were tested for fibrinogen and fibronectin binding, and adhesion/internalization into human keratinocytes with and without biocide.

RESULTS

Binding to fibrinogen and fibronectin, adhesion and intracellular uptake within keratinocytes (P < 0.001) and intracellular survival in keratinocytes under chlorhexidine pressure (ST22 3.18%, ST36 4.57% vs ST239-TW 12.79%; P < 0.0001) was consistently higher for ST239-TW.

CONCLUSIONS

We present evidence that MRSA clones with similarly low in vitro tolerance to chlorhexidine exhibit different in vivo susceptibilities. The phenomenon of S. aureus adhesion and intracellular uptake into keratinocytes could therefore be regarded as an additional mechanism of chlorhexidine tolerance, enabling MRSA to evade infection control measures.

Conflicts of interest in infection prevention and control research: no smoke without fire. A narrative review

Conflicts of interest (COIs) do occur in healthcare research, yet their impact on research in the field of infection prevention and control (IPC) is unknown. We conducted a narrative review aiming to identify examples of COIs in IPC research. In addition to well-known instances, we conducted PubMed and Google searches to identify and report case studies of COIs in IPC and antimicrobial resistance (AMR), which were chosen arbitrarily following consensus meetings, to illustrate different types of COIs. We also searched the Retraction Watch database and blog to systematically identify retracted IPC and/or infectious disease-related papers. Our review highlights COIs in academic research linked to ties between industry and physicians, journal editors, peer-reviewed journals' choice for publication, and guideline committees participants and authors. It explores how COIs can affect research and could be managed. We also present several selected case studies that involve (1) the chlorhexidine industry and how it has used marketing trials and key opinion leaders to promote off-label use of its products; (2) the copper industry and how reporting of its trials in IPC have furthered their agenda; (3) the influence of a company developing "closed infusion systems" for catheters and how this affects networks in low- and middle-income countries and guideline development; (4) potential perverse incentives hospitals may have in reporting healthcare-associated infection or AMR rates and how government intervention may restrict AMR research for fear of bad publicity and subsequent negative economic consequences. Finally, the analysis of reasons for the retraction of previously published papers highlights the fact that misconduct in research may have other motivations than financial gain, the most visible form of COIs. COIs occur in the field of research in general, and IPC and AMR are no exceptions. Their effects pervade all aspects of the research and publication processes. We believe that, in addition to improvements in management strategies of COIs, increased public funding should be available to decrease researchers' dependency on industry ties. Further research is needed on COIs and their management.

Comparative mechanism based study on disinfectants against multidrug-resistant Acinetobacter baumannii

Acinetobacter baumannii has emerged as a hospital-acquired pathogen and has spread in the hospital settings, leading to enhanced nosocomial outbreaks associated with high death rates. Therefore, the aim of the current study is to determine the effective concentration of disinfectants like sodium hypochlorite, hydrogen peroxide, and chlorine dioxide, against multidrug-resistant (MDR) strains of A. baumannii. In this study, we have investigated the effect of disinfectants on different MDR strains i.e. RS307, RS6694, RS7434, RS10953, RS122, and sensitive strain ATCC-19606 of A. baumannii, via differential growth curves analysis, disc diffusion assay, estimation of reactive oxygen species (ROS), lipid peroxidation, and protein carbonylation. All the results collectively showed that 1% sodium hypochlorite (P value < 0.0027), 2.5% hydrogen peroxide (P value = 0.0032), and 10 mM (P value = 0.017) chlorine dioxide significantly inhibit the growth of MDR strains of A. baumannii. A significant increase in the ROS generations, altered lipid peroxidation, and a decrease in protein carbonylation was also observed after treatment with disinfectants, which confirmed its ROS-dependent damage mechanism. These disinfectants also enhance the membrane leakage of reducing sugar, protein, and DNA. The current study highlights and recommends the use of 2.5% hydrogen peroxide to control the MDR strains of A. baumannii in the hospital setup. Therefore, the present results will help in selecting concentrations of different disinfectants for regular use in hospital setups to eradicate the multidrug-resistant A. baumannii from the hospital setup.

Germicidal Activity against Carbapenem/Colistin-Resistant Enterobacteriaceae Using a Quantitative Carrier Test Method

Susceptibility to germicides for carbapenem/colistin-resistant Enterobacteriaceae is poorly described. We investigated the efficacy of multiple germicides against these emerging antibiotic-resistant pathogens using the disc-based quantitative carrier test method that can produce results more similar to those encountered in health care settings than a suspension test. Our study results demonstrated that germicides commonly used in health care facilities likely will be effective against carbapenem/colistin-resistant Enterobacteriaceae when used appropriately in health care facilities.

Increased Usage of Antiseptics Is Associated with Reduced Susceptibility in Clinical Isolates of Staphylococcus aureus

Hospital-acquired infection is a major cause of morbidity and mortality, and regimes to prevent infection are crucial in infection control. These include the decolonization of vulnerable patients with methicillin-resistant Staphylococcus aureus (MRSA) carriage using antiseptics, including chlorhexidine and octenidine. Concern has been raised, however, regarding the possible development of biocide resistance. In this study, we assembled a panel of S. aureus isolates, including isolates collected before the development of chlorhexidine and octenidine and isolates, from a major hospital trust in the United Kingdom during a period when the decolonization regimes were altered. We observed significant increases in the MIC and minimum bactericidal concentration (MBC) of chlorhexidine in isolates from periods of high usage of chlorhexidine. Isolates with increased MICs and MBCs of octenidine rapidly emerged after octenidine was introduced in the trust. There was no apparent cross-resistance between the two biocidal agents. A combination of variable-number tandem repeat (VNTR) analysis, PCR for qac genes, and whole-genome sequencing was used to type isolates and examine possible mechanisms of resistance. There was no expansion of a single strain associated with decreased biocide tolerance, and biocide susceptibility did not correlate with carriage of qac efflux pump genes. Mutations within the NorA or NorB efflux pumps, previously associated with chlorhexidine export, were identified, however, suggesting that this may be an important mechanism of biocide tolerance. We present evidence that isolates are evolving in the face of biocide challenge in patients and that changes in decolonization regimes are reflected in changes in susceptibility of isolates.

Infection in hospitals remains a major cause of death and disease. One way in which we combat this is by decolonizing at-risk patients from carriage of bacteria which can cause disease such as MRSA. This is done with antiseptics, including chlorhexidine and octenidine. There is concern, however, that bacteria may be able to become resistant to these antiseptics. In this study, we looked at isolates of MRSA and found that there was a correlation between the use of antiseptics and increased resistance in the isolates. We also suggest that the mechanism by which these more tolerant isolates may become resistant to antiseptics is that of changing a transport pump that exports these agents. This information suggests that we need to study the impact of antiseptics on clinically important bacteria more closely.

Imidazolium ionic liquids as effective antiseptics and disinfectants against drug resistant S. aureus: In silico and in vitro studies

This paper describes Quantitative Structure-Activity Relationships (QSAR) studies, molecular docking and in vitro antibacterial activity of several potent imidazolium-based ionic liquids (ILs) against S. aureus ATCC 25923 and its clinical isolate. Small set of 131 ILs was collected from the literature and uploaded in the OCHEM database. QSAR methodologies used Associative Neural Networks and Random Forests (WEKA-RF) methods. The predictive ability of the models was tested through cross-validation, giving cross-validated coefficients q² = 0.82-0.87 for regression models and overall prediction accuracies of 80-82.1% for classification models. The proposed QSAR models are freely available online on OCHEM server at https://ochem.eu/article/107364 and can be used for estimation of antibacterial activity of new imidazolium-based ILs. A series of synthesized 1,3-dialkylimidazolium ILs with predicted activity were evaluated in vitro. The high activity of 7 ILs against S. aureus strain and its clinical isolate was measured and thereafter analyzed by the molecular docking to prokaryotic homologue of a eukaryotic tubulin FtsZ.

Antimicrobial effect of copper alloys on Acinetobacter species isolated from infections and hospital environment

Background

An increased proportion of Gram-negative bacteria have recently been reported among etiologic agents of infection. In Poland, Acinetobacter baumannii is a big problem for hospitals, especially intensive care units. Touch surfaces made from materials with antimicrobial properties, especially copper alloys, are recommended as a supplementary method of increasing biological safety in the hospital environment.

Aim of the study

The objective of this study is to determine the susceptibility to selected copper alloys of three clinical Acinetobacter baumannii strains, one Acinetobacter lwoffi and an A. pittii strain isolated from the hospital environment.

Material and method

The modification of the Japanese Standard, which the ISO 22196:2011 norm was used for testing antimicrobial properties of CuZn37, CuSn6 and CuNi18Zn20 and Cu-ETP and stainless steel as positive and negative control, respectively.

Results

The highest cidal efficiency, expressed as both time and the degree of reduction of the initial suspension density, against all of the tested Acinetobacter strains was found for ETP copper. But, the results of our study also confirmed effective activity (bacteriocidal or bacteriostatic) of copper alloys selected for the study, contrary to the stainless steel. The reduction in bacterial suspension density is significantly different depending on the strain and copper alloy composition.

Conslusions

The results of our study confirmed the effective antibacterial activity of copper and its selected alloys against clinical Acinetobacter baumannii and Acinetobacter lwoffii strains, and Acinetobacter pittii strain isolated from the hospital environment.

Antimicrobial Properties of Selected Copper Alloys on Staphylococcus aureus and Escherichia coli in Different Simulations of Environmental Conditions: With vs. without Organic Contamination

Background: Hospital equipment made from copper alloys can play an important role in complementing traditional methods of disinfection. Aims of the study: The aim of this study was to assess the dynamics of the antimicrobial properties of selected copper alloys in different simulations of environmental conditions (with organic contamination vs. without organic contamination), and to test alternatives to the currently used testing methods. Materials and Methods: A modification of Japanese standard JIS Z 2801 as well as Staphylococcus aureus (SA) and Escherichia coli (EC) suspended in NaCl vs. tryptic soy broth (TSB) were used in tests performed on seven commonly used copper alloys, copper, and stainless steel. Results: A much faster reduction of the bacterial suspension was observed for the inoculum prepared in NaCl than in TSB. A faster reduction for EC than for SA was observed in the inoculum prepared in NaCl. The opposite results were found for the inoculum based on TSB. A significant correlation between the copper concentration in the copper alloys and the time and degree of bacterial suspension reduction was only observed in the case of EC. Conclusions: This study confirmed the antimicrobial properties of copper alloys, and additionally showed that Staphylococcus aureus was more resistant than Escherichia coli in the variant of the experiment without organic contamination. However, even for SA, a total reduction of the bacterial inoculum’s density took no longer than 2 h. Under conditions simulating organic contamination, all of the tested alloys were shown to have bactericidal or bacteriostatic properties, which was contrary to the results from stainless steel.

A novel method to detect bacterial resistance to disinfectants

In clinical practice, the important hygienic prevention of bacterial pathogen spread is disinfection of potentially contaminated area. Benzalkonium bromide and chlorhexidine acetate are commonly used disinfectants with a broad spectrum of anti-microbial effect. It is vital to inhibit the spread of pathogen in hospital. However, a large number of pathogens with the decreased antiseptic susceptibility have been isolated from clinical samples which showed an increased minimal inhibitory concentration (MIC) against those antiseptics. These resistant pathogens are the major causes for nosocomial cross-infections in hospital. The present study demonstrated the utility of Oxford plate assay system in determining the potential disinfectant resistance of bacteria. The microbiological assay is based on the inhibitory effect of tested disinfectants upon the strains of Staphylococcus aureus and Escherichia coli. Statistical analysis of the bioassay results indicated the linear correlation (r = 0.87–0.99, P < 0.01) between the diameter of growth inhibition zone and the log dosage of the tested disinfectants. Moreover, comparison of inhibitory efficacy of benzalkonium bromide upon 29 S. aureus strains isolated from clinical samples by both Oxford plate method and broth dilution method showed that the diameter of growth inhibition zone has significantly negative correlation with the minimal inhibitory concentration (MIC) (r = −0.574, P < 0.001). These results suggest that the Oxford plate is a simple and time-saving method in detecting potential clinical disinfectant resistance and its usefulness for routine surveillance of pathogenic resistance to disinfectants warrants further investigation.

Reduction in chlorhexidine efficacy against multi-drug-resistant Acinetobacter baumannii international clone II

BACKGROUND

Nosocomial infections caused by Acinetobacter baumannii international clone II (IC II) can cause severe clinical outcomes.

AIM

Differential evaluation of bactericidal efficacy of chlorhexidine gluconate (CHX) and benzethonium chloride (BZT) disinfectants against IC II and non-IC II isolates.

METHODS

Minimum inhibitory concentrations (MICs) of CHX and BZT were determined for 137 A. baumannii IC II, 99 non-IC II and 69 non-baumannii isolates, further classified according to MIC values into disinfectant-reduced susceptible (DRS) and disinfectant-susceptible (DS) groups. Time-kill curves and minimum bactericidal concentrations (MBCs) were evaluated for representative isolates in each group.

RESULTS

CHX and BZT MIC₉₀s for IC II isolates were 100 and 175mg/L, respectively, but those for non-IC II and non-baumannii isolates were <100mg/L. Nevertheless, time-kill curves indicated that CHX and BZT reduced live bacterial cell number by 5 log₁₀ for IC II and non-IC II isolates within 30s when used at 1000mg/L, comparable to practical use concentrations. CHX MBC at 30s was 1000mg/L for IC II and non-IC II isolates, and was not influenced by addition of 3% bovine serum albumin (BSA); BZT MBC at 30s was 100mg/L without BSA and increased up to 500mg/L upon addition of BSA. No significant differences in BSA were found between DRS and DS isolates.

CONCLUSION

CHX and BZT were effective against Acinetobacter spp. including IC II at a concentration of 1000mg/L and exposure for at least 30s, but their concentrations should be considered carefully to ensure sufficient effects in both clinical and healthcare settings.

Decolonization in Prevention of Health Care-Associated Infections

Colonization with health care-associated pathogens such as Staphylococcus aureus, enterococci, Gram-negative organisms, and Clostridium difficile is associated with increased risk of infection. Decolonization is an evidence-based intervention that can be used to prevent health care-associated infections (HAIs). This review evaluates agents used for nasal topical decolonization, topical (e.g., skin) decolonization, oral decolonization, and selective digestive or oropharyngeal decontamination. Although the majority of studies performed to date have focused on S. aureus decolonization, there is increasing interest in how to apply decolonization strategies to reduce infections due to Gram-negative organisms, especially those that are multidrug resistant. Nasal topical decolonization agents reviewed include mupirocin, bacitracin, retapamulin, povidone-iodine, alcohol-based nasal antiseptic, tea tree oil, photodynamic therapy, omiganan pentahydrochloride, and lysostaphin. Mupirocin is still the gold standard agent for S. aureus nasal decolonization, but there is concern about mupirocin resistance, and alternative agents are needed. Of the other nasal decolonization agents, large clinical trials are still needed to evaluate the effectiveness of retapamulin, povidone-iodine, alcohol-based nasal antiseptic, tea tree oil, omiganan pentahydrochloride, and lysostaphin. Given inferior outcomes and increased risk of allergic dermatitis, the use of bacitracin-containing compounds cannot be recommended as a decolonization strategy. Topical decolonization agents reviewed included chlorhexidine gluconate (CHG), hexachlorophane, povidone-iodine, triclosan, and sodium hypochlorite. Of these, CHG is the skin decolonization agent that has the strongest evidence base, and sodium hypochlorite can also be recommended. CHG is associated with prevention of infections due to Gram-positive and Gram-negative organisms as well as Candida. Conversely, triclosan use is discouraged, and topical decolonization with hexachlorophane and povidone-iodine cannot be recommended at this time. There is also evidence to support use of selective digestive decontamination and selective oropharyngeal decontamination, but additional studies are needed to assess resistance to these agents, especially selection for resistance among Gram-negative organisms. The strongest evidence for decolonization is for use among surgical patients as a strategy to prevent surgical site infections.

In vitro activity of a polyhexanide-betaine solution against high-risk clones of multidrug-resistant nosocomial pathogens

OBJECTIVE

To determine the in vitro activity of a polyhexanide-betaine solution against collection strains and multidrug-resistant (MDR) nosocomial isolates, including high-risk clones.

METHODS

We studied of 8 ATCC and 21 MDR clinical strains of Staphylococcus aureus, Enterococcus faecium, Enterococcus faecalis, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa, including the multiresistant high-risk clones. The MICs and MBCs of a 0.1% polyhexanide-0.1% betaine solution were determined by microdilution. For each species, strains with the highest MICs were selected for further experiments. The dilution-neutralization test (PrEN 12054) was performed by incubating bacterial inocula of 10⁶CFU/mL for 1min with undiluted 0.1% polyhexanide-betaine solution. The CFUs were counted after neutralization. Growth curves and time-kill curves at concentrations of 0.25, 1, 4, and 8×MIC, were performed. MICs of recovered strains were determined when regrowth was observed in time-kill studies after 24h of incubation. Strains with reduced susceptibility were selected by serial passage on plates with increasing concentrations of polyhexanide-betaine, and MICs were determined.

RESULTS

Polyhexanide-betaine MIC range was 0.5-8mg/L. MBCs equalled or were 1 dilution higher than MICs. The dilution-neutralization method showed total inoculum clearance of all strains. In time-kill curves, no regrowth was observed at 4×MIC, except for S. aureus (8×MIC). Increased MICs were not observed in time-kill curves, or after serial passages after exposure to polyhexanide-betaine.

CONCLUSIONS

Polyhexanide-betaine presented bactericidal activity against all MDR clinical isolates tested, including high-risk clones, at significantly lower concentrations and time of activity than those commercially used.

Current Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in Elderly French People: Troublesome Clones on the Horizon

Objective: In 2015, we conducted at 44 healthcare facilities (HCFs) and 21 nursing homes (NHs) a 3-month bloodstream infection (BSI) survey, and a 1-day prevalence study to determine the rate of carriage of methicillin-resistant Staphylococcus aureus (MRSA) in 891 patients and 470 residents. We investigated the molecular characteristics of the BSI-associated and colonizing MRSA isolates, and assessed cross-transmission using double-locus sequence typing and pulsed-field gel electrophoresis protocol.

Results: The incidence of MRSA-BSI was 0.040/1000 patient-days (19 cases). The prevalence of MRSA carriage was 4.2% in patients (n = 39) and 8.7% in residents (n = 41) (p < 0.001). BSI-associated and colonizing isolates were similar: none were PVL-positive; 86.9% belonged to clonal complexes 5 and 8; 93.9% were resistant to fluoroquinolones. The qacA/B gene was carried by 15.8% of the BSI-associated isolates [3/3 BSI cases in intensive care units (ICUs)], and 7.7% of the colonizing isolates in HCFs. Probable resident-to-resident transmission was identified in four NHs.

Conclusion: Despite generally reassuring results, we identified two key concerns. First, a worryingly high prevalence of the qacA/B gene in MRSA isolates. Antisepsis measures being crucial to prevent healthcare-associated infections, our findings raise questions about the potential risk associated with chlorhexidine use in qacA/B⁺ MRSA carriers, particularly in ICUs. Second, NHs are a weak link in MRSA control. MRSA spread was not controlled at several NHs; because of their frequent contact with the community, conditions are favorable for these NHs to serve as reservoirs of USA300 clone for local HCFs.

Randomized, placebo-controlled, double-blind clinical trial to evaluate the efficacy of polyhexanide for topical decolonization of MRSA carriers

OBJECTIVES

The objective of this study was to evaluate the efficacy of polyhexanide (Prontoderm(®)) in eliminating MRSA carriage.

METHODS

In a 1900 bed teaching hospital, MRSA-colonized patients were randomized into a double-blind, placebo-controlled superiority trial between January 2011 and July 2014. Patients were treated with either polyhexanide or placebo applied to the anterior nares (thrice daily) and skin (once daily) for 10 days. The primary outcome was MRSA decolonization at day 28 (D28) after the end of treatment assessed by ITT responder and PP analyses (microbiological follow-up ± 7 days and topical treatment ≥ 5 days). Secondary outcomes included safety, emergence of resistance and MRSA genotype changes. Registered trial number ISRCTN02288276.

RESULTS

Of 2590 patients screened, 146 (polyhexanide group, 71; placebo group, 75) were included. ITT analysis showed that 24/71 (33.8%) patients in the polyhexanide group versus 22/75 (29.3%) in the placebo group were MRSA-free at D28 (risk difference, 4.5%; 95% CI, -10.6% to 19.5%; P = 0.56). PP analysis confirmed the results with 19/53 (35.8%) decolonized polyhexanide-treated patients versus 17/56 (30.4%) in the placebo arm (risk difference, 5.5%; 95% CI, -12.2% to 23%; P = 0.54). Nine serious adverse events occurred in the polyhexanide group versus 12 in the placebo group; none was attributable to study medication. Emergence of polyhexanide resistance or cross-resistance between polyhexanide and chlorhexidine was not observed. No case of exogenous recolonization by a genotypically different MRSA strain was documented.

CONCLUSIONS

This study suggests that under real-life conditions, a single polyhexanide decolonization course is not effective in eradicating MRSA carriage.

Determining the resistance of carbapenem-resistant Klebsiella pneumoniae to common disinfectants and elucidating the underlying resistance mechanisms

INTRODUCTION

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infection is a serious problem in hospitals worldwide, posing a particular risk to immunocompromised patients. Elimination strategies may prevent these drug-resistant bacteria from spreading within hospital environments. Here, the susceptibility of patient-derived CRKP strains to common chemical disinfectants and possible correlations between the presence of drug-resistance genes and increased resistance to disinfectants were investigated.

METHODS

The minimum inhibitory (MIC) and the minimum bactericidal concentrations (MBC) of common chemical disinfectants against each CRKP strain were determined using agar dilution; K. pneumoniae ATCC700603 served as a standard. The presence of the drug-resistance genes qacΔE, qacA, acrA and qacE was determined using PCR.

RESULTS

A total of 27 clinically isolated CRKP strains collected in our hospital from 2011 to 2013 exhibited sensitivity to the following common chemical disinfectants in decreasing order of sensitivity: 75% ethyl alcohol > 2% glutaraldehyde > "84" disinfectant > 0.2% benzalkonium bromide > 2% iodine tincture > 1% iodophor > 0.1% chlorhexidine acetate. Of the 27 strains, 59, 41, 19 and 15% contained qacΔE, qacA, acrA and qacE resistance genes; 15% carried acrA, qacΔE and qacA, and 26% carried both qacA and qacΔE. Comparative analysis indicated that drug-resistance genes were correlated with higher MIC values.

CONCLUSION

These pan-resistant pathogenic CRKP strains contained various drug-resistance genes and exhibited relatively high resistance to ethyl alcohol, chlorhexidine acetate and iodophor. Monitoring the drug-resistance rates of CRKP strains displaying disinfectant resistance may facilitate appropriate and effective sterilisation and thus preventing the spread of these pan-resistant strains.

Development of a protocol for predicting bacterial resistance to microbicides

Regulations dealing with microbicides in Europe and the United States are evolving and now require data on the risk of the development of resistance in organisms targeted by microbicidal products. There is no standard protocol to assess the risk of the development of resistance to microbicidal formulations. This study aimed to validate the use of changes in microbicide and antibiotic susceptibility as initial markers for predicting microbicide resistance and cross-resistance to antibiotics. Three industrial isolates (Pseudomonas aeruginosa, Burkholderia cepacia, and Klebsiella pneumoniae) and two Salmonella enterica serovar Typhimurium strains (SL1344 and 14028S) were exposed to a shampoo, a mouthwash, eye makeup remover, and the microbicides contained within these formulations (chlorhexidine digluconate [CHG] and benzalkonium chloride [BZC]) under realistic, in-use conditions. Baseline and postexposure data were compared. No significant increases in the MIC or the minimum bactericidal concentration (MBC) were observed for any strain after exposure to the three formulations. Increases as high as 100-fold in the MICs and MBCs of CHG and BZC for SL1344 and 14028S were observed but were unstable. Changes in antibiotic susceptibility were not clinically significant. The use of MICs and MBCs combined with antibiotic susceptibility profiling and stability testing generated reproducible data that allowed for an initial prediction of the development of resistance to microbicides. These approaches measure characteristics that are directly relevant to the concern over resistance and cross-resistance development following the use of microbicides. These are low-cost, high-throughput techniques, allowing manufacturers to provide to regulatory bodies, promptly and efficiently, data supporting an early assessment of the risk of resistance development.

Antimicrobial activity of Eucalyptus globulus oil, xylitol and papain: a pilot study

OBJECTIVE To evaluate the in vitro antimicrobial activity of the Eucalyptus globulus essential oil, and of the xylitol and papain substances against the following microorganisms: Pseudomonas aeruginosa; Samonella sp.; Staphylococus aureus; Proteus vulgaris; Escherichia coli and Candida albicans. METHOD The in vitro antimicrobial evaluation was used by means of the agar diffusion test and evaluation of the inhibition zone diameter of the tested substances. Chlorhexidine 0.5% was used as control. RESULTS The Eucalyptus globulus oil showed higher inhibition than chlorhexidine when applied to Staphylococcus aureus, and equal inhibition when applied to the following microorganisms: Escherichia coli, Proteus vulgaris and Candida albicans. Papain 10% showed lower antimicrobial effect than chlorhexidine in relation to Candida albicans. Xylitol showed no inhibition of the tested microorganisms. CONCLUSION The Eucalyptus globulus oil has antimicrobial activity against different microorganisms and appears to be a viable alternative as germicidal agent hence, further investigation is recommended.