Beware biofilm! Dry biofilms containing bacterial pathogens on multiple healthcare surfaces; a multi-centre study

Biofilms and Antimicrobial Resistance in Healthcare: Evaluating Chlorine Dioxide as a Candidate to Protect Patient Safety

Healthcare-associated infections (HAIs) caused by the transmission of multi drug resistant organisms (MDROs) from contaminated surfaces are a major challenge for healthcare organisations. The presence of biofilm on surfaces makes effective environmental decontamination difficult to achieve and exacerbates antimicrobial resistance (AMR). In this study the performance of various chlorine dioxide-based disinfectants against a panel of MDROs, and biofilms formed by Pseudomonas aeruginosa and Staphylococcus aureus, was evaluated. All chlorine dioxide-based disinfectants tested demonstrated sufficient activity against MDROs meeting the relevant test standards and exhibited similar log reductions against organisms within the biofilm model. Sufficient log reductions when tested to the appropriate test standards in realistic contact times against planktonic MDROs, and comparable reductions against biofilms suggest chlorine dioxide is an attractive candidate for environmental decontamination strategies.

Exploring the bactericidal efficacy of a new potassium monopersulphate-based disinfectant

BACKGROUND

Staphylococcus aureus and Klebsiella pneumoniae are common pathogens responsible for hospital-acquired infections. Both species can survive on surfaces following desiccation and form dry surface biofilms (DSB), which complicates the disinfection process.

AIM

To evaluate the efficacy of an innovative potassium monopersulphate-based nanotechnology formulation (MPS) against both planktonic and sessile S. aureus and K. pneumoniae.

METHODS

The bactericidal efficacy of MPS was tested in comparison with sodium hypochlorite (NaOCl) and didecyldimethylammonium chloride (DDAC), which served as controls. The assessment was performed against planktonic bacteria, hydrated biofilm, and dry surface biofilm (DSB) using standard suspension and carrier tests. Scanning electron microscopy (SEM) was employed to identify any gross structural damage.

FINDINGS

MPS (2% w/v) achieved a ≥4 log10 reduction in K. pneumoniae with a short contact time, regardless of the test protocol. S. aureus proved more resilient, but the introduction of wiping reduced the contact time needed to achieve a 4 log10 reduction from 15 to 5 minutes. SEM analysis revealed gross structural damage in both species following MPS treatment. The other disinfectants tested were also bactericidal, achieving ≥4 log10 reduction within 1-5 minutes, with the exception of DDAC against hydrated biofilms.

CONCLUSIONS

The potassium monopersulphate-based formulation was found to be an effective bactericide, including against dry surface biofilms (DSB). Its efficacy compares favourably with other biocides commonly used in healthcare settings, and its biodegradability makes it a promising candidate for further development. However, optimisation of the mechanical removal process will be essential to enhance MPS efficacy in practical applications.

Degradation and Deactivation of Intracellular Bacterial Antibiotic Resistance Genes by Commonly Used Healthcare and Personal Care Disinfectants

This work investigated efficacies of commonly used healthcare and personal care disinfectants, including glutaraldehyde, chlorhexidine, ethanol, povidone-iodine, benzalkonium chloride, phenol, free chlorine, hydrogen peroxide (H2O2), and 254 nm UV light, in degrading (as measured by qPCR analyses of ∼1000 bp amplicon loss) and deactivating (as measured by transforming activity loss) bacterial antibiotic resistance genes (ARGs) during inactivation of antibiotic-resistant bacteria (ARB) on inanimate surfaces or in aqueous suspension. Intracellular ARGs (iARGs) blt, mecA, and ampC, within vegetative cells of Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa, respectively, were treated on PTFE and/or stainless-steel surfaces or in aqueous phosphate buffer (PB; H2O2 only), to simulate potential healthcare and personal care cleaning applications under representative disinfectant exposure conditions. No chemical disinfectant yielded more than limited (≤1.9log10) iARG degradation/deactivation under the conditions investigated, even when ARB cells were extensively inactivated (at levels from 3.1log10 to ≥6log10). In contrast, UV irradiation yielded up to ∼2.8-3.2log10 iARG degradation/deactivation at corresponding ARB inactivation levels up to ∼4log10 in the case of the blt gene within B. subtilis cells on PTFE surfaces, though levels of iARG degradation/deactivation and ARB inactivation were generally lower than expected based on prior aqueous-phase results, likely due to light-shielding effects at the typical ∼108-109 CFU/mL cell inoculum densities used for surface disinfection tests. During exposure to H2O2 in PB, iARG deactivation and ARB inactivation reached up to 1.7log10 and >3.5log10, respectively, while iARG degradation was minimal (≤0.2log10); this appears to be driven by DNA-strand fragmentation (as observed by pulsed-field gel electrophoresis analysis) likely resulting from reaction with endogenous HO• (or Fe(IV)) generated via intracellular iron-catalyzed H2O2 decomposition. While all investigated disinfectants were able to effectively inactivate ARB cells themselves, these results demonstrate that most are ineffective in simultaneously degrading and deactivating iARGs, highlighting the potential benefits of employing disinfectants such as 254 nm UV light, that selectively target bacterial DNA, to improve mitigation of antibiotic resistance dissemination.

Dry Surface Biofilm Formation by Candida auris Facilitates Persistence and Tolerance to Sodium Hypochlorite

Candida auris is an enigmatic fungal pathogen, recently elevated as a critical priority group pathogen by the World Health Organisation, linked with its ability to cause outbreaks within nosocomial care units, facilitated through environmental persistence. We investigated the susceptibility of phenotypically distinct C. auris isolates to sodium hypochlorite (NaOCl), and evaluated the role of biofilms in surviving disinfection using a dry-surface biofilm (DSB) model and transcriptomic profiling. Planktonic cells were tested for susceptibility to NaOCl, with biofilm formation using the 12-day DSB model, assessed using viable counts, biomass assays and microscopy. Disinfection efficacy was assessed using clinical protocols of 500-1,000 ppm for 1-5 min. RNA sequencing was performed on untreated DSBs in comparison to planktonic cells. Isolates were found to be susceptible planktonically, but grew NaOCl-tolerant biofilms, with only 2-4 log10 reductions in viable cells observed at highest concentrations. Transcriptomics identified DSB upregulation of ABC transporters and iron acquisition pathways relative to planktonic cells. Our findings optimized a DSB protocol in which C. auris can mediate tolerance to NaOCl disinfection, suggesting a lifestyle through which this problematic yeast can environmentally persist. Mechanistically, it has been shown for the first time that upregulation of small-molecule and iron transport pathways are potential facilitators of environmental survival.

A comparison of two cleaning methods applied in a small animal hospital

BACKGROUND

Environmental cleaning of near-patient surfaces in animal healthcare is an important infection prevention and control measure to lower the risk of spread of healthcare-associated infections (HAIs). There is a lack of reports on the effect of cleaning of near-patient surfaces in animal hospital wards. The aims of this study were to (1) determine bacterial load before cleaning, on near-patient surfaces in dog cages in a mixed medical and surgical ward and investigate factors associated with this bacterial load (2) compare the bacterial reduction on these surfaces after cleaning with (a) a scrubbing brush with detergent and rinsing before and after cleaning, and (b) a microfibre mop moistened with water, and after disinfection carried out after each cleaning method. In each cage the floor and the wall were sampled before cleaning, after cleaning, and after disinfection. Bacterial load and reduction were log10-transformed and for comparisons t-test, one-way Anova and Wilcoxon rank sum test were used. A generalized additive model was performed for analysis of the association between factors and bacterial load.

RESULTS

The bacterial load in dog cages before cleaning varied, higher loads were noted after longer stay in the cage. The bacterial reduction was in most cases more effective after cleaning with scrubbing brushes with detergent compared to cleaning with damp microfibre mops. After cleaning, a majority of the samples were below the suggested threshold value 2.5 CFU/cm2, except for floor samples after microfibre cleaning. No significant difference in bacterial load, between cleaning methods was noted after disinfection. Overall, the bacterial load was significantly lower on walls than on floors.

CONCLUSIONS

Overall, the bacterial load was below the suggested threshold value after decontamination, except after microfibre cleaning of the floor. Scrub cleaning with a detergent should be considered for cleaning of anti-slip surfaces like the cage floor. The study shows a need for evidence-based cleaning and disinfection routines for near-patient surfaces and evidence-based threshold values for bacterial load, to reduce the risk of HAIs.

Light-activated antimicrobial coatings: the great potential of organic photosensitizers

Contamination of inanimate surfaces with microorganisms is considered one of the routes for transmission of pathogens, which is a matter of concern not only in healthcare-related facilities, but also in public areas. Durable antimicrobial coatings have emerged as the one of most promising strategies for reducing the accumulation of microorganisms on high-touch surfaces. Light-activated antimicrobial layers are of particular interest for such a purpose, as they generate singlet oxygen and other reactive oxygen species that are effective against a broad spectrum of bacteria, viruses, and fungi. In this review, the antimicrobial coatings containing organic photosensitizers are discussed, focusing on the recent advances in the strategies for PSs' immobilization on solid surfaces. The review attempts to assess the advantages and limitations of those systems, and the challenges that still need to be overcome.

Biofilm Resilience: Molecular Mechanisms Driving Antibiotic Resistance in Clinical Contexts

Healthcare-associated infections pose a significant global health challenge, negatively impacting patient outcomes and burdening healthcare systems. A major contributing factor to healthcare-associated infections is the formation of biofilms, structured microbial communities encased in a self-produced extracellular polymeric substance matrix. Biofilms are critical in disease etiology and antibiotic resistance, complicating treatment and infection control efforts. Their inherent resistance mechanisms enable them to withstand antibiotic therapies, leading to recurrent infections and increased morbidity. This review explores the development of biofilms and their dual roles in health and disease. It highlights the structural and protective functions of the EPS matrix, which shields microbial populations from immune responses and antimicrobial agents. Key molecular mechanisms of biofilm resistance, including restricted antibiotic penetration, persister cell dormancy, and genetic adaptations, are identified as significant barriers to effective management. Biofilms are implicated in various clinical contexts, including chronic wounds, medical device-associated infections, oral health complications, and surgical site infections. Their prevalence in hospital environments exacerbates infection control challenges and underscores the urgent need for innovative preventive and therapeutic strategies. This review evaluates cutting-edge approaches such as DNase-mediated biofilm disruption, RNAIII-inhibiting peptides, DNABII proteins, bacteriophage therapies, antimicrobial peptides, nanoparticle-based solutions, antimicrobial coatings, and antimicrobial lock therapies. It also examines critical challenges associated with biofilm-related healthcare-associated infections, including diagnostic difficulties, disinfectant resistance, and economic implications. This review emphasizes the need for a multidisciplinary approach and underscores the importance of understanding biofilm dynamics, their role in disease pathogenesis, and the advancements in therapeutic strategies to combat biofilm-associated infections effectively in clinical settings. These insights aim to enhance treatment outcomes and reduce the burden of biofilm-related diseases.

Antimicrobial efficacy of an experimental UV-C robot in controlled conditions and in a real hospital scenario

BACKGROUND

Among no-touch automated disinfection devices, ultraviolet-C (UV-C) radiation has been proven to be one of the most effective against a broad spectrum of micro-organisms causing healthcare-associated infections.

AIM

To evaluate the antimicrobial efficacy of an experimental UV-C robotic platform, under controlled conditions and in a real hospital scenario, when used to implement the standard cleaning operating protocol (SOP).

METHODS

In vitro, following dose calibration tests, bactericidal and virucidal efficacy were tested in accordance with American Society for Testing and Materials International Standard E3135-18. In hospital settings, 12 high-touch surfaces were sampled after healthcare activity (dirty condition), after SOP alone, and after SOP + UV-C treatment, with a total of 180 samples.

FINDINGS

In vitro, <4 mJ/cm2 was required to remove Staphylococcus aureus and Pseudomonas aeruginosa completely, 194 mJ/cm2 was required to inactivate adenovirus HadV5 completely, and 38.8 mJ/cm2 was sufficient to inactivate coronavirus 229E completely. In the real hospital scenario, the mean UV-C dose emitted on the sampled surfaces was 29.31 mJ/cm2. A significant difference was found after SOP alone (P=0.022) and after SOP + UV-C treatment (P=0.007) compared with the dirty condition. The average percentage reduction in the total viable count (TVC) was 67% after SOP alone and 96% after SOP + UV-C treatment.

CONCLUSIONS

Comparison of the tests conducted in vitro and in the real hospital scenario showed that the efficacy of the UV-C robot was reduced in the hospital setting, as a higher dose was needed to obtain a reduction in the TVC.

Effect of Doping Cement Mortar with Triclosan, Hypochlorous Acid, Silver Nanoparticles and Graphene Oxide on Its Mechanical and Biological Properties

In order to improve the performance of cement mortar (Portland cement), it was enriched with triclosan, hypochlorous acid, silver nanoparticles and graphene oxide. Cement mortar is used, among other things, to fill the gaps between the tiles of building porcelain stoneware. A number of structural, mechanical and biological tests were carried out. The structural tests included microscopic analysis and contact angle, reflectance and IR spectra, while the mechanical tests involved static bending and compression testing. These tests showed that the additions of graphene oxide and hypochlorous acid were most beneficial. These additions, although not detected by spectral methods, resulted in a significant increase in contact angle and mechanical properties. Studies of the viability of the bacteria Pseudomonas aeruginosa and Staphylococcus aureus showed that all the additives used resulted in a decrease in viability compared to the undoped cement mortar. There was also a beneficial decrease in the viability of fungi of the genus Fusarium on cement mortar mainly doped with silver nanoparticles.

Does Antibiotic Use Contribute to Biofilm Resistance in Sink Drains? A Case Study from Four German Hospital Wards

Backgound. As biofilms are known to harbour (multi-)resistant species, their presence in health settings must be considered critical. Although there is evidence that bacteria spread from drains to the outside, there is still a lack of research data focusing on drain biofilms from hospitals. Methods. We sampled biofilms from various wards of Helios Hospital Krefeld (Germany), where comprehensive antibiotic consumption data were available. Biofilms were analysed by cell counting, isolation of relevant bacterial groups and genetic and phenotypical resistance parameters. Data were correlated with the prescribed antibiotics of the respective ward. Furthermore, an ex situ biofilm model was employed to investigate the influence of sub-inhibitory antibiotics on the bacterial community and the prevalence of class 1 integrons. Results. Our results show that every ward harboured medically relevant bacterial species. While no significant differences were found in cell counts, the median prevalence of the resistance marker gene intI1 correlated with the amount of prescribed antibiotics. In contrast, phenotypical resistances showed no similar tendency. In addition, melting curve analysis data and changes in intI1 prevalence show that the composition of the bacterial community shifted depending on the biofilm and antibiotic. Conclusions. To the best of our knowledge, our study is the first considering possible correlations between the consumption data of hospital wards and resistances in drain biofilms the way we did. Based on our results, we conclude that sub-inhibitory concentrations of antibiotics have no general effect on biofilms in terms of bacterial community shift and occurrence of antibiotic-resistant species. Amongst other things, the effect depends on the initial composition of the bacterial community, the antibiotic used and the intrinsic bacterial resistance, e.g., prevalence of class 1 integrons.

Photodynamic coatings kill bacteria on near-patient surfaces in intensive care units with low light intensities

BACKGROUND

Surfaces in close proximity to patients within hospitals may cause healthcare-associated infections. These surfaces are repositories for pathogens facilitating their transmission among staff and patients. Regular cleaning and disinfection of these surfaces provides only a temporary elimination of pathogens with inevitable recontamination. Antimicrobial coatings (AMCs) of such surfaces may additionally reduce the risk of pathogen transmissions.

AIM

To evaluate the efficacy of a standard and a novel photodynamic AMC, even at very low light intensities, in a field study conducted in two ICUs at our university hospital.

METHODS

The microbial burden was determined on three coatings: standard photodynamic AMC (A), a novel photodynamic AMC (B), and an inactive AMC as control (C). The control coating C was identical to standard coating A, but it contained no photosensitizer. During a three-month period, 699 samples were collected from identical surfaces using eSwab and were analysed (cfu/cm2).

FINDINGS

Mean values of all surfaces covered with control coating (C) showed a microbial burden of 5.5 ± 14.8 cfu/cm2. Photodynamic AMC showed significantly lower mean value of 1.6 ± 4.6 cfu/cm2 (coating A; P < 0.001) and 2.7 ± 9.6 (coating B; P < 0.001). When considering a benchmark of 2.5 cfu/cm2, the relative risk for higher microbial counts was reduced by 52% (coating A) or 40% (coating B), respectively.

CONCLUSION

Both photodynamic AMCs offer a substantial, permanent risk reduction of microbial counts on near-patient surfaces in ICUs with low light intensities.

Evaluation of the long-term protection conferred by an organosilicon-based disinfectant formulation against bacterial contamination of surfaces

AIMS

The aim of this work was to evaluate the efficacy of an organosilicon-based, commercially available antimicrobial formulation in the My-shield® product line against bacterial surface contamination.

METHODS AND RESULTS

The antimicrobial product was tested in vitro for its long-term persistence on surfaces and effectiveness against Staphylococcus aureus biofilms in comparison to 70% ethanol and 0.1% or 0.6% sodium hypochlorite. Field testing was also conducted over 6 weeks at a university athletic facility. In vitro studies demonstrated the log reductions achieved by the test product, 70% ethanol, and 0.1% sodium hypochlorite were 3.6, 3.1, and 3.2, respectively. The test product persisted on surfaces after washing and scrubbing, and pre-treatment with this product prevented S. aureus surface colonization for up to 30 days. In comparison, pre-treatment with 70% ethanol or 0.6% sodium hypochlorite was not protective against S. aureus biofilm formation after seven days. The field test demonstrated that weekly applications of the test product were more effective at reducing surface bacterial load than daily applications of a control product.

CONCLUSIONS

The test product conferred greater long-term protection against bacterial growth and biofilm formation by S. aureus than ethanol and sodium hypochlorite. Even with less frequent applications, the test product maintained a high level of antimicrobial activity.

Formation of Single-Species and Multispecies Biofilm by Isolates from Septic Transfusion Reactions in Platelet Bag Model

During 2018-2021, eight septic transfusion reactions occurred from transfusion of platelet units contaminated with Acinetobacter spp., Staphylococcus saprophyticus, Leclercia adecarboxylata, or a combination of those environmental organisms. Whether biofilm formation contributed to evasion of bacterial risk mitigations, including bacterial culture, point-of-care testing, or pathogen-reduction technology, is unclear. We designed a 12-well plate-based method to evaluate environmental determinants of single-species and multispecies biofilm formation in platelets. We evaluated bacteria isolated from septic transfusion reactions for biofilm formation by using crystal violet staining and enumeration of adherent bacteria. Most combinations of bacteria had enhanced biofilm production compared with single bacteria. Combinations involving L. adecarboxylata had increased crystal violet biofilm production and adherent bacteria. This study demonstrates that transfusion-relevant bacteria can produce biofilms well together. More work is needed to clarify the effect of biofilms on platelet bacterial risk control strategies, but US Food and Drug Administration-recommended strategies remain acceptable.

[Multi-resistant pathogens - are they also resistant to disinfectants?]

Epidemiological studies show that the care of patients in rooms with a previous stay by a person with evidence of multi-resistant pathogens (MRP) is associated with an increased risk of these pathogens occurring. The question therefore regularly arises as to whether MRP also exhibit resistance to the disinfectants used. To date, there are no standardised definitions for "resistance" to disinfectants. However, disinfectants authorised on the market are also effective against multi-resistant pathogens and the failure of efficient disinfection is mainly caused by application errors (insufficient cleaning, incomplete wetting, incorrect application concentration or exposure time etc.). The effectiveness of disinfectants depends on a variety of environmental factors (especially accompanying contamination). A reduced sensitivity to disinfectants can occur in individual isolates due to selection under sub-inhibitory concentrations of disinfectants. Resistance mechanisms to antibiotics do not mediate cross-resistance to disinfectants, but a change in the permeability of bacterial cells can influence sensitivity to disinfectants and antibiotics. In general, the success of routine disinfection can be improved by suitable process controls and contribute to reducing the transmission of MRP.

Transfer of micro-organisms from dry surface biofilms and the influence of long survival under conditions of poor nutrition and moisture on the virulence of Staphylococcusaureus

BACKGROUND

Biofilms on dry hospital surfaces can enhance the persistence of micro-organisms on dry harsh clinical surfaces and can potentially act as reservoirs of infectious agents on contaminated surfaces.

AIM

This study was conducted to quantify the transfer of viable Staphylococcus aureus cells from dry biofilms through touching and to investigate the impact of nutrient and moisture deprivation on virulence levels in S. aureus.

METHODS

Dry biofilms of S. aureus ATCC 25923 and a defective biofilm-forming ability mutant, S. aureus 1132, were formed in 24-well plates under optimized conditions mimicking dry biofilm formation on clinical surfaces. Microbial cell transfer was induced through the touching of the dry biofilms, which were quantified on nutrient agar. To investigate the impact of nutrient and moisture deprivation on virulence levels, dry and standard biofilms as well as planktonic cells of S. aureus ATCC 25923 were inoculated into Galleria mellonella and their kill rates compared.

FINDINGS

Results of this study showed that viable cells from dry biofilms of S. aureus ATCC 25923 were significantly more virulent and readily transferrable from dry biofilms through a touch test, therefore representing a greater risk of infection. The biofilm-forming capability of S. aureus strains had no significant impact on their transferability with more cells transferring when biofilm surfaces were wet.

CONCLUSIONS

These findings indicate that dry biofilms on hospital surfaces may serve as a reservoir for the dissemination of pathogenic micro-organisms in hospitals, thus highlighting the importance of regular cleaning and adequate disinfection of hospital surfaces.

Biofilms, mobile genetic elements and the persistence of pathogens on environmental surfaces in healthcare and food processing environments

Biofilms are the natural state for bacterial and fungal species. To achieve surface hygiene in commercial facilities, the presence of biofilms must be adequately considered. However, standard disinfectant and sanitizer efficacy tests required by the US-EPA and the European Committee for Standardization (CEN) do not currently consider the role of environmental biofilms. This selective review will discuss what biofilms are and why they are important. We will also cover where they are commonly found in healthcare and food processing facilities and explore how current antimicrobial test methods required for product registration do not test for the presence of biofilms. Additionally, we will explore how a lack of efficacy against biofilms may play a role in the development of antimicrobial resistance in healthcare facilities due to the exchange of mobile genetic elements that occur readily in a biofilm matrix.

Infection prevention control in practice: a survey of healthcare professionals' knowledge and experiences

Background

Laboratory experiments are crucial in understanding efficacy of disinfectant products, but without compliance and appropriate application, the effectiveness of products is compromised. This study aims to understand current perceptions and knowledge of healthcare professionals (HCPs) to common cleaning and disinfection routines and microbial contamination, including biofilms, in healthcare environments.

Methods

An online survey, including open and closed questions, was developed. Non-probability convenience and purposive sampling were used: those currently or previously in a healthcare profession were eligible. Survey responses were taken over 24 months, including the COVID-19 pandemic.

Discussion

137 participants completed the survey; over 50% were nurses. Surface cleaning frequency increased post COVID-19 from 'twice a day' to 'three/more times a day'. Disinfection frequency reduced from 'between every patient' before COVID-19 to 'twice a day' afterwards. A multimethod approach to cleaning and disinfection (70.8%) was predominant when considering the best method to deliver infection control. Most areas of clinical settings were identified as high risk (13/19). Most (87.6%) participants had heard the term 'biofilm', mainly at conference/study days (60%). 39.1% said they were aware of dry surface biofilms (DSB) in the healthcare environment.

Conclusions

There remain mixed views on surface cleaning and disinfection within healthcare. Education is important for understanding microbial contamination and tackling problems. More people than expected had heard the term DSB. Infection control practices seemed consistent across responses, however whether this is reality is unknown. This study provides an initial insight into current opinions/knowledge of HCPs and can form basis for further in-depth investigation.

Critical analysis of methods to determine growth, control and analysis of biofilms for potential non-submerged antibiofilm surfaces and coatings

The potential uses for antibiofilm surfaces reach across different sectors with significant resultant economic, societal and health impact. For those interested in using antibiofilm surfaces in the built environment, it is important that efficacy testing methods are relevant, reproducible and standardised where possible, to ensure data outputs are applicable to end-use, and comparable across the literature. Using pre-defined keywords, a review of literature reporting on antimicrobial surfaces (78 articles), within which a potential application was described as non-submerged/non-medical surface or coating with antibiofilm action, was undertaken. The most used methods utilized the growth of biofilm in submerged and static systems. Quantification varied (from most to least commonly used) across colony forming unit counts, non-microscopy fluorescence or spectroscopy, microscopy analysis, direct agar-contact, sequencing, and ELISA. Selection of growth media, microbial species, and incubation temperature also varied. In many cases, definitions of biofilm and attempts to quantify antibiofilm activity were absent or vague. Assessing a surface after biofilm recovery or assessing potential regrowth of a biofilm after initial analysis was almost entirely absent. It is clear the field would benefit from widely agreed and adopted approaches or guidance on how to select and incorporate end-use specific conditions, alongside minimum reporting guidelines may benefit the literature.

Trends in viable microbial bioburden on surfaces within a paediatric bone marrow transplant unit

BACKGROUND

Despite their role being historically overlooked, environmental surfaces have been shown to play a key role in the transmission of pathogens causative of healthcare-associated infection. To guide infection prevention and control (IPC) interventions and inform clinical risk assessments, more needs to be known about microbial surface bioburdens.

AIM

To identify the trends in culturable bacterial contamination across communal touch sites over time in a hospital setting.

METHODS

Swab samples were collected over nine weeks from 22 communal touch sites in a paediatric bone marrow transplant unit. Samples were cultured on Columbia blood agar and aerobic colony counts (ACC) per 100 cm2 were established for each site. Individual colony morphologies were grouped and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry or 16s rDNA sequencing.

FINDINGS

Highest mean counts were observed for sites associated with ward management activity and computer devices (3.29 and 2.97 ACC/100 cm2 respectively). A nurses' station keyboard had high mean ACC/100 cm2 counts (10.67) and diversity, while laundry controls had high mean ACC/100 cm2 counts (4.70) and low diversity. Micrococcus luteus was identified in all sampling groups. Clinical staff usage sites were contaminated with similar proportions of skin and environmental flora (52.19-46.59% respectively), but sites associated with parental activities were predominantly contaminated by environmental microflora (86.53%).

CONCLUSION

The trends observed suggest patterns in microbial loading based on site activities, surface types and user groups. Improved understanding of environmental surface contamination could help support results interpretation and IPC interventions, improving patient safety.

How long do nosocomial pathogens persist on inanimate surfaces? A scoping review

Healthcare hygiene plays a crucial role in the prevention of healthcare-associated infections. Patients admitted to a room where the previous occupant had a multi-drug-resistant bacterial infection are at an increased risk of colonization and infection with the same organism. A 2006 systematic review by Kramer et al. found that certain pathogens can survive for months on dry surfaces. The aim of this review is to update Kramer et al.'s previous review and provide contemporary data on the survival of pathogens relevant to the healthcare environment. We systematically searched Ovid MEDLINE, CINAHL and Scopus databases for studies that described the survival time of common nosocomial pathogens in the environment. Pathogens included in the review were bacterial, viral, and fungal. Studies were independently screened against predetermined inclusion/exclusion criteria by two researchers. Conflicts were resolved by one of two senior researchers. A spreadsheet was developed for the data extraction. The search identified 1736 studies. Following removal of duplicates and application of the search criteria, the synthesis of results from 62 included studies were included. 117 organisms were reported. The longest surviving organism reported was Klebsiella pneumoniae which was found to have persisted for 600 days. Common pathogens of concern to infection prevention and control, can survive or persist on inanimate surfaces for months. This data supports the need for a risk-based approach to cleaning and disinfection practices, accompanied by appropriate training, audit and feedback which are proven to be effective when adopted in a 'bundle' approach.

Prevalence of Infections and Antimicrobial Resistance of ESKAPE Group Bacteria Isolated from Patients Admitted to the Intensive Care Unit of a County Emergency Hospital in Romania

The ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella Pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp.) is a group of bacteria very difficult to treat due to their high ability to acquire resistance to antibiotics and are the main cause of nosocomial infections worldwide, posing a threat to global public health. Nosocomial infections with MDR bacteria are found mainly in Intensive Care Units, due to the multitude of maneuvers and invasive medical devices used, the prolonged antibiotic treatments, the serious general condition of these critical patients, and the prolonged duration of hospitalization.

MATERIALS AND METHODS

During a period of one year, from January 2023 to December 2023, this cross-sectional study was conducted on patients diagnosed with sepsis admitted to the Intensive Care Unit of the Sibiu County Emergency Clinical Hospital. Samples taken were tracheal aspirate, catheter tip, pharyngeal exudate, wound secretion, urine culture, blood culture, and peritoneal fluid.

RESULTS

The most common bacteria isolated from patients admitted to our Intensive Care Unit was Klebsiella pneumoniae, followed by Acinetobacter baumanii and Pseudomonas aeruginosa. Gram-positive cocci (Enterococcus faecium and Staphilococcus aureus) were rarely isolated. Most of the bacteria isolated were MDR bacteria.

CONCLUSIONS

The rise of antibiotic and antimicrobial resistance among strains in the nosocomial environment and especially in Intensive Care Units raises serious concerns about limited treatment options.

Effective elimination of bacteria on hard surfaces by the combined use of bacteriophages and chemical disinfectants

Hospital-acquired infections (HAIs) represent one of the significant causes of morbidity and mortality worldwide, and controlling pathogens in the hospital environment is of great importance. Currently, the standard disinfection method in the hospital environment is chemical disinfection. However, disinfectants are usually not used strictly according to the label, making them less effective in disinfection. Therefore, there is an emergent need to find a better approach that can be used in hospitals to control pathogenic bacteria in the clinical environment. Bacteriophages (phages) are effective in killing bacteria and have been applied in the treatment of bacterial infections but have not received enough attention regarding the control of contamination in the clinical environment. In this study, we found that various phages remain active in the presence of chemical disinfectants. Moreover, the combined use of specific phages and chemical disinfectants is more effective in removing bacterial biofilms and eliminating bacteria on hard surfaces. Thus, this proof-of-concept study indicates that adding phages directly to chemical disinfectants might be an effective and economical approach to enhance clinical environment disinfection.

IMPORTANCE

In this study, we investigated whether the combination of bacteriophages and chemical disinfectants can enhance the efficacy of reducing bacterial contamination on hard surfaces in the clinical setting. We found that specific phages are active in chemical disinfectants and that the combined use of phages and chemical disinfectants was highly effective in reducing bacterial presence on hard surfaces. As a proof-of-concept, we demonstrated that adding specific phages directly to chemical disinfectants is an effective and cost-efficient strategy for clinical environment disinfection.

TiO2 Nanocomposite Coatings and Inactivation of Carbapenemase-Producing Klebsiella Pneumoniae Biofilm-Opportunities and Challenges

The worldwide increase of multidrug-resistant Gram-negative bacteria is a global threat. The emergence and global spread of Klebsiella pneumoniae carbapenemase- (KPC-) producing Klebsiella pneumoniae represent a particular concern. This pathogen has increased resistance and abilities to persist in human reservoirs, in hospital environments, on medical devices, and to generate biofilms. Mortality related to this microorganism is high among immunosuppressed oncological patients and those with multiple hospitalizations and an extended stay in intensive care. There is a severe threat posed by the ability of biofilms to grow and resist antibiotics. Various nanotechnology-based strategies have been studied and developed to prevent and combat serious health problems caused by biofilm infections. The aim of this review was to evaluate the implications of nanotechnology in eradicating biofilms with KPC-producing Klebsiella pneumoniae, one of the bacteria most frequently associated with nosocomial infections in intensive care units, including in our department, and to highlight studies presenting the potential applicability of TiO2 nanocomposite materials in hospital practice. We also described the frequency of the presence of bacterial biofilms on medical surfaces, devices, and equipment. TiO2 nanocomposite coatings are one of the best long-term options for antimicrobial efficacy due to their biocompatibility, stability, corrosion resistance, and low cost; they find their applicability in hospital practice due to their critical antimicrobial role for surfaces and orthopedic and dental implants. The International Agency for Research on Cancer has recently classified titanium dioxide nanoparticles (TiO2 NPs) as possibly carcinogenic. Currently, there is an interest in the ecological, non-toxic synthesis of TiO2 nanoparticles via biological methods. Biogenic, non-toxic nanoparticles have remarkable properties due to their biocompatibility, stability, and size. Few studies have mentioned the use of nanoparticle-coated surfaces as antibiofilm agents. A literature review was performed to identify publications related to KPC-producing Klebsiella pneumoniae biofilms and antimicrobial TiO2 photocatalytic nanocomposite coatings. There are few reviews on the antibacterial and antibiofilm applications of TiO2 photocatalytic nanocomposite coatings. TiO2 nanoparticles demonstrated marked antibiofilm activity, but being nano in size, these nanoparticles can penetrate cell membranes and may initiate cellular toxicity and genotoxicity. Biogenic TiO2 nanoparticles obtained via green, ecological technology have less applicability but are actively investigated.

Bacterial viability in dry-surface biofilms in healthcare facilities: a systematic review

BACKGROUND

Bacteria are known to live inside architectural structures called biofilms. Though standard biofilms have been studied extensively for more than 50 years, little is known about dry-surface biofilms (DSBs). Since 2012, DSBs have been described in several scientific papers, but basic knowledge about the viability and culturability of bacteria remains limited.

AIM

To conduct a systematic review to determine whether bacteria inside DSBs are viable, culturable, and enumerable.

METHODS

Eligible articles had to deal with DSBs containing at least one bacterial species involved in healthcare-associated infections, which developed in actual healthcare environments (in-situ) or with the help of any biofilm model (in-vitro).

FINDINGS

Twenty-four articles were included in the review. Whereas most of them isolated viable bacteria (87% in situ; 100% in vitro), no in-situ study quantified culturable bacteria in the biofilm per unit area. Conversely, 100% of in-vitro studies cultured the bacteria from controls and 94.4% supplied an enumeration of them. Culturable bacteria also grew after 78% of the cleaning, disinfection, or sterilization protocols tested. Microscopic observations after staining the samples with live/dead fluorescent probes (Baclight®) showed large amounts of viable cells in culture-negative samples.

CONCLUSION

Our study questions the efficacy of current methods for microbiological monitoring of surfaces, since these methods are only based on bacterial culturability. To improve both surface monitoring and cleaning and disinfection protocols, it is necessary to integrate the concept of DSBs which appears to contain a significant amount of viable but non-culturable bacteria.

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.

Dynamics of Staphylococcus aureus in patients and the hospital environment in a tertiary care hospital in the Netherlands

BACKGROUND

The dynamics of Staphylococcus aureus in patients and the hospital environment are relatively unknown. We studied these dynamics in a tertiary care hospital in the Netherlands.

METHODS

Nasal samples were taken from adult patients at admission and discharge. Isolates cultured from clinical samples taken before and during hospitalization from these patients were included. Environmental samples of patient rooms were taken over a three-year period. Finally, isolates from clinical samples from patients with an epidemiological link to S. aureus positive rooms were included. Staphylococcal protein A (spa) typing was performed.

RESULTS

Nasal samples were taken from 673 patients. One hundred eighteen (17.5%) were positive at admission and discharge, 15 (2.2%) patients acquired S. aureus during hospitalization. Nineteen patients had a positive clinical sample during hospitalization, 15.9% of the S. aureus were considered as from an exogenous source. One hundred and forty (2.8%) environmental samples were S. aureus positive. No persistent contamination of surfaces was observed. Isolates were highly diverse: spa typing was performed for 893 isolates, identifying 278 different spa types, 161 of these spa types were observed only once.

CONCLUSION

Limited transmission could be identified between patients and the hospital environment, and from patient-to-patient. Exogenous acquisition was assumed to occur in 15% of clinical samples. Environmental contamination was infrequent, temporarily, and coincided with the strain from the patient admitted to the room at that time. MRSA was rare and not found in the environment.

Bacillus-based probiotic cleansers reduce the formation of dry biofilms on common hospital surfaces

In the absence of liquid suspension, dry biofilms can form upon hard surfaces within a hospital environment, representing a healthcare-associated infection risk. Probiotic cleansers using generally recognized as safe organisms, such as those of the Bacillus genus, represent a potential strategy for the reduction of dry biofilm bioburden. The mechanisms of action and efficacy of these cleaners are, however, poorly understood. To address this, a preventative dry biofilm assay was developed using steel, melamine, and ceramic surfaces to assess the ability of a commercially available Bacillus spp. based probiotic cleanser to reduce the surface bioburden of Escherichia coli and Staphylococcus aureus. Via this assay, phosphate-buffered saline controls were able to generate dry biofilms within 7 days of incubation, with the application of the probiotic cleanser able to prevent >97.7% of dry biofilm formation across both pathogen analogs and surface types. Further to this, surfaces treated with the probiotic mixture alone also showed a reduction in dry biofilm across both pathogen and surface types. Confocal laser scanning microscopy imaging indicated that the probiotic bacteria were able to germinate and colonize surfaces, likely forming a protective layer upon these hard surfaces.

Biofilms on medical instruments and surfaces: Do they interfere with instrument reprocessing and surface disinfection

BACKGROUND

Biofilms are surface-attached communities of bacteria embedded in an extracellular matrix. This matrix shields the resident cells from desiccation, chemical perturbation, invasion by other bacteria, and confers reduced susceptibility to antibiotics and disinfectants. There is growing evidence that biofilms on medical instruments (especially endoscopes) and environmental surfaces interfere with cleaning and disinfection.

METHODS

The English literature on the impact of biofilms in medicine was reviewed with a focus on the impact of biofilms on reusable semicritical medical instruments and hospital environmental surfaces.

RESULTS

Biofilms are frequently present on hospital environmental surfaces and reusable medical equipment. Important health care...associated pathogens that readily form biofilms on environmental surfaces include Staphylococcus aureus, Pseudomonas aeruginosa, and Candida auris. Evidence has demonstrated that biofilms interfere with cleaning and disinfection.

DISCUSSION

New technologies such as ..úself-disinfecting..Ñ surfaces or continuous room disinfection systems may reduce or disrupt biofilm formation and are under study to reduce the impact of the contaminated surface environment on health care...associated infections.

CONCLUSIONS

Future research is urgently needed to develop methods to reduce or eliminate biofilms from forming on implantable medical devices, reusable medical equipment, and hospital surfaces.

Modelling hospital disinfectant against multi-drug-resistant dry surface biofilms grown under artificial human sweat

BACKGROUND

Dry surface biofilms (DSBs) have been found abundantly across hospital surfaces within intensive care units and may explain how nosocomial pathogens can remain virulent and persist on surfaces for extended periods. Testing standards governing the performance of disinfectant products employ planktonic models under routine growth conditions, which are known to be less tolerant than their biofilm counterpart.

AIM

To evaluate biofilm models cultured under artificial human sweat (AHS), a source of nutrient expected on touch surfaces, to assess the antimicrobial performance of common cleaning agents, including a quaternary ammonium, hydrogen peroxide and active chlorine.

METHODS

Five single-species biofilms, using pathogenic bacteria such as Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus faecalis, were generated on stainless-steel substrates using a sedimentation protocol under both AHS and nutrient-rich conditions for a direct comparison of phenotypic tolerance. The biofilm models were grown over five days followed by desiccation cycles, before being submerged into the disinfectant solutions for up to 25 min. Epifluorescence (EF) microscopy using LIVE/DEAD™ stain was used to visualize microcolony viability.

FINDINGS

The results revealed biofilms cultured under AHS exhibited a greater antimicrobial tolerance and reduced speed of kill for all cleaning agents compared with the routine media; an average reduction of 72.4% vs 96.9%, respectively. EF microscopy revealed traces of viable bacteria across all coupons after disinfection indicating a potential opportunity for regrowth and recontamination.

CONCLUSION

The notable difference in biocidal performance between the two growth conditions highlights potential pitfalls within current antimicrobial test standards, and the importance of accurate representation of the microbial challenge.

An automated contact model for transmission of dry surface biofilms of Acinetobacter baumannii in healthcare

BACKGROUND

Dry surface biofilms (DSBs) have been recognized across environmental and equipment surfaces in hospitals and could explain how microbial contamination can survive for an extended period and may play a key role in the transmission of hospital-acquired infections. Despite little being known on how they form and proliferate in clinical settings, DSB models for disinfectant efficacy testing exist.

AIM

In this study we develop a novel biofilm model to represent formation within hospitals, by emulating patient to surface interactions.

METHODS

The model generates a DSB through the transmission of artificial human sweat (AHS) and clinically relevant pathogens using a synthetic thumb capable of emulating human contact. The DNA, glycoconjugates and protein composition of the model biofilm, along with structural features of the micro-colonies was determined using fluorescent stains visualized by epifluorescence microscopy and compared with published clinical data.

RESULTS

Micrographs revealed the heterogeneity of the biofilm across the surface; and reveal protein as the principal component within the matrix, followed by glycoconjugates and DNA. The model repeatably transferred trace amounts of micro-organisms and AHS, every 5 min for up to 120 h on to stainless-steel coupons to generate a biofilm model averaging 1.16 × 103 cfu/cm2 falling within the reported range for clinical DSB (4.20 × 102 to 1.60 × 107 bacteria/cm2).

CONCLUSION

Our in vitro DSB model exhibits many phenotypical characteristics and traits to those reported in situ. The model highlights key features often overlooked and the potential for downstream applications such as antibiofilm claims using more realistic microbial challenges.

Detection, survival, and persistence of Staphylococcus capitis NRCS-A in neonatal units in England

BACKGROUND

The multidrug-resistant Staphylococcus capitis clone, NRCS-A, is increasingly associated with late-onset sepsis in low birthweight newborns in neonatal intensive care units (NICUs) in England and globally. Understanding where this bacterium survives and persists within the NICU environment is key to developing and implementing effective control measures.

AIM

To investigate the potential for S. capitis to colonize surfaces within NICUs.

METHODS

Surface swabs were collected from four NICUs with and without known NRCS-A colonizations/infections present at the time of sampling. Samples were cultured and S. capitis isolates analysed via whole-genome sequencing. Survival of NRCS-A on plastic surfaces was assessed over time and compared to that of non-NRCS-A isolates. The bactericidal activity of commonly used chemical disinfectants against S. capitis was assessed.

FINDINGS

Of 173 surfaces sampled, 40 (21.1%) harboured S. capitis with 30 isolates (75%) being NRCS-A. Whereas S. capitis was recovered from surfaces across the NICU, the NRCS-A clone was rarely recovered from outside the immediate neonatal bedspace. Incubators and other bedside equipment were contaminated with NRCS-A regardless of clinical case detection. In the absence of cleaning, S. capitis was able to survive for three days with minimal losses in viability (<0.5 log10 reduction). Sodium troclosene and a QAC-based detergent/disinfectant reduced S. capitis to below detectable levels.

CONCLUSION

S. capitis NRCS-A can be readily recovered from the NICU environment, even in units with no recent reported clinical cases of S. capitis infection, highlighting a need for appropriate national guidance on cleaning within the neonatal care environment.

Klebsiella pneumoniae survives on surfaces as a dry biofilm

BACKGROUND

Dry surface biofilms (DSB) are widespread in healthcare settings presenting a challenge to cleaning and disinfection. Klebsiella pneumoniae has been a focus of attention due to antibiotic resistance and the emergence of hypervirulent strains. Few studies have demonstrated K pneumoniae survival on surfaces following desiccation.

METHODS

DSB were formed over 12 days. Bacterial culturability and transfer were investigated following DSB incubation up to 4 weeks. Bacterial viability in DSB was investigated with live/dead staining using flow cytometry.

RESULTS

K pneumoniae formed mature DSB. After 2 and 4 weeks of incubation, transfer from DSB was low (<55%) and reduced further (<21%) following wiping. Culturability at 2 and 4 weeks varied although viability remained high indicating viable but non culturable state (VBNC).

DISCUSSION

K pneumoniae was removed from surfaces by mechanical wiping as shown with DSB of other species. Although culturability was reduced over time, bacteria remained viable up to 4 weeks incubation, proving the need for robust cleaning regimens.

CONCLUSIONS

This is the first study confirming K pneumoniae survival on dry surfaces as a DSB. The presence of VBNC bacteria indicated that K pneumoniae can for extended periods, raising questions about its persistence on surfaces.

How biofilm changes our understanding of cleaning and disinfection

Biofilms are ubiquitous in healthcare settings. By nature, biofilms are less susceptible to antimicrobials and are associated with healthcare-associated infections (HAI). Resistance of biofilm to antimicrobials is multifactorial with the presence of a matrix composed of extracellular polymeric substances and eDNA, being a major contributing factor. The usual multispecies composition of environmental biofilms can also impact on antimicrobial efficacy. In healthcare settings, two main types of biofilms are present: hydrated biofilms, for example, in drains and parts of some medical devices and equipment, and environmental dry biofilms (DSB) on surfaces and possibly in medical devices. Biofilms act as a reservoir for pathogens including multi-drug resistant organisms and their elimination requires different approaches. The control of hydrated (drain) biofilms should be informed by a reduction or elimination of microbial bioburden together with measuring biofilm regrowth time. The control of DSB should be measured by a combination of a reduction or elimination in microbial bioburden on surfaces together with a decrease in bacterial transfer post-intervention. Failure to control biofilms increases the risk for HAI, but biofilms are not solely responsible for disinfection failure or shortcoming. The limited number of standardised biofilm efficacy tests is a hindrance for end users and manufacturers, whilst in Europe there are no approved standard protocols. Education of stakeholders about biofilms and ad hoc efficacy tests, often academic in nature, is thus paramount, to achieve a better control of biofilms in healthcare settings.

Hospital cleaning: past, present, and future

INTRODUCTION

The importance of hospital cleaning for controlling healthcare-associated infection (HAI) has taken years to acknowledge. This is mainly because the removal of dirt is inextricably entwined with gender and social status, along with lack of evidence and confusion over HAI definitions. Reducing so-called endogenous infection due to human carriage entails patient screening, decolonisation and/or prophylaxis, whereas adequate ventilation, plumbing and cleaning are needed to reduce exogenous infection. These infection types remain difficult to separate and quantitate. Patients themselves demonstrate wide-ranging vulnerability to infection, which further complicates attempted ranking of control interventions, including cleaning. There has been disproportionate attention towards endogenous infection with less interest in managing environmental reservoirs.

QUANTIFYING CLEANING AND CLEANLINESS

Finding evidence for cleaning is compromised by the fact that modelling HAI rates against arbitrary measurements of cleaning/cleanliness requires universal standards and these are not yet established. Furthermore, the distinction between cleaning (soil removal) and cleanliness (soil remaining) is usually overlooked. Tangible bench marking for both cleaning methods and all surface types within different units, with modification according to patient status, would be invaluable for domestic planning, monitoring and specification.

AIMS AND OBJECTIVES

This narrative review will focus on recent history and current status of cleaning in hospitals. While its importance is now generally accepted, cleaning practices still need attention in order to determine how, when and where to clean. Renewed interest in removal and monitoring of surface bioburden would help to embed risk-based practice in hospitals across the world.

Phenotypic Variation in Clinical S. aureus Isolates Did Not Affect Disinfection Efficacy Using Short-Term UV-C Radiation

Pigmentation, catalase activity and biofilm formation are virulence factors that cause resistance of Staphylococcus aureus to environmental stress factors including disinfectants. In recent years, automatic UV-C room disinfection gained greater importance in enhanced disinfection procedures to improve disinfection success in hospitals. In this study, we evaluated the effect of naturally occurring variations in the expression of virulence factors in clinical S. aureus isolates on tolerance against UV-C radiation. Quantification of staphyloxanthin expression, catalase activity and biofilm formation for nine genetically different clinical S. aureus isolates as well as reference strain S. aureus ATCC 6538 were performed using methanol extraction, a visual approach assay and a biofilm assay, respectively. Log10 reduction values (LRV) were determined after irradiation of artificially contaminated ceramic tiles with 50 and 22 mJ/cm2 UV-C using a commercial UV-C disinfection robot. A wide variety of virulence factor expression was observed, indicating differential regulation of global regulatory networks. However, no direct correlation with the strength of expression with UV-C tolerance was observed for either staphyloxanthin expression, catalase activity or biofilm formation. All isolates were effectively reduced with LRVs of 4.75 to 5.94. UV-C disinfection seems therefore effective against a wide spectrum of S. aureus strains independent of occurring variations in the expression of the investigated virulence factors. Due to only minor differences, the results of frequently used reference strains seem to be representative also for clinical isolates in S. aureus.

In situ generation of H2O2 using CaO2 as peroxide storage depot for haloperoxidase mimicry with surface-tailored Bi-doped mesoporous CeO2 nanozymes

Designing the size, morphology and interfacial charge of catalyst particles at the nanometer scale can enhance their performance. We demonstrate this with nanoceria which is a functional mimic of haloperoxidases, a group of enzymes that halogenates organic substrates in the presence of hydrogen peroxide. These reactions in aqueous solution require the presence of H₂O₂. We demonstrate in situ generation of H₂O₂ from a CaO₂ reservoir in polyether sulfone (PES) and poly(vinylidene fluoride) (PVDF) polymer beads, which circumvents the external addition of H₂O₂ and expands the scope of applications for haloperoxidase reactions. The catalytic activity of nanoceria was enhanced significantly by Bi³⁺ substitution. Bi-doped mesoporous ceria nanoparticles with tunable surface properties were prepared by changing the reaction time. Increasing reaction time increases the surface area S_BET of the mesoporous Bi_0.2Ce_0.8O_1.9 nanoparticles and the Ce³⁺/Ce⁴⁺ ratio, which is associated with the ζ-potential. In this way, the catalytic activity of nanoceria could be tuned in a straightforward manner. H₂O₂ required for the reaction was released steadily over a long period of time from a CaO₂ storage depot incorporated in polyether sulfone (PES) and poly(vinylidene fluoride) (PVDF) beads together with Bi_0.2Ce_0.8O_1.9 particles, which may be used as precision fillers and templates for biological applications. The spheres are prepared as a dry powder with no surface functionalization or coatings. They are inert, chemically stable, and safe for handling. The feasibility of this approach was demonstrated using a haloperoxidase assay.

Staphylococcus aureus Cell Wall Phenotypic Changes Associated with Biofilm Maturation and Water Availability: A Key Contributing Factor for Chlorine Resistance

Staphylococcus aureus biofilms are resistant to both antibiotics and disinfectants. As Staphylococci cell walls are an important defence mechanism, we sought to examine changes to the bacterial cell wall under different growth conditions. Cell walls of S. aureus grown as 3-day hydrated biofilm, 12-day hydrated biofilm, and 12-day dry surface biofilm (DSB) were compared to cell walls of planktonic organisms. Additionally, proteomic analysis using high-throughput tandem mass tag-based mass spectrometry was performed. Proteins involved in cell wall synthesis in biofilms were upregulated in comparison to planktonic growth. Bacterial cell wall width (measured by transmission electron microscopy) and peptidoglycan production (detected using a silkworm larva plasma system) increased with biofilm culture duration (p < 0.001) and dehydration (p = 0.002). Similarly, disinfectant tolerance was greatest in DSB, followed by 12-day hydrated biofilm and then 3-day biofilm, and it was least in the planktonic bacteria--suggesting that changes to the cell wall may be a key factor for S. aureus biofilm biocide resistance. Our findings shed light on possible new targets to combat biofilm-related infections and hospital dry surface biofilms.

Using visible light to activate antiviral and antimicrobial properties of TiO2 nanoparticles in paints and coatings: focus on new developments for frequent-touch surfaces in hospitals

The COVID-19 pandemic refocused scientists the world over to produce technologies that will be able to prevent the spread of such diseases in the future. One area that deservedly receives much attention is the disinfection of health facilities like hospitals, public areas like bathrooms and train stations, and cleaning areas in the food industry. Microorganisms and viruses can attach to and survive on surfaces for a long time in most cases, increasing the risk for infection. One of the most attractive disinfection methods is paints and coatings containing nanoparticles that act as photocatalysts. Of these, titanium dioxide is appealing due to its low cost and photoreactivity. However, on its own, it can only be activated under high-energy UV light due to the high band gap and fast recombination of photogenerated species. The ideal material or coating should be activated under artificial light conditions to impact indoor areas, especially considering wall paints or frequent-touch areas like door handles and elevator buttons. By introducing dopants to TiO₂ NPs, the bandgap can be lowered to a state of visible-light photocatalysis occurring. Naturally, many researchers are exploring this property now. This review article highlights the most recent advancements and research on visible-light activation of TiO₂-doped NPs in coatings and paints. The progress in fighting air pollution and personal protective equipment is also briefly discussed.

Graphical Abstract

Indoor visible-light photocatalytic activation of reactive oxygen species (ROS) over TiO₂ nanoparticles in paint to kill bacteria and coat frequently touched surfaces in the medical and food industries.

A comprehensive comparison of biofilm formation and capsule production for bacterial survival on hospital surfaces

Biofilm formation and capsule production are known microbial strategies used by bacterial pathogens to survive adverse conditions in the hospital environment. The relative importance of these strategies individually is unexplored. This project aims to compare the contributory roles of biofilm formation and capsule production in bacterial survival on hospital surfaces. Representative strains of bacterial species often causing hospital-acquired infections were selected, including Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa. The importance of biofilm formation and capsule production on bacterial survival was evaluated by comparing capsule-positive wild-type and capsule-deficient mutant strains, and biofilm and planktonic growth modes respectively, against three adverse hospital conditions, including desiccation, benzalkonium chloride disinfection and ultraviolet (UV) radiation. Bacterial survival was quantitatively assessed using colony-forming unit (CFU) enumeration and the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay and qualitatively by scanning electron microscopy (SEM). Correlations between capsule production and biofilm formation were further investigated. Biofilm formation contributed significantly to bacterial survival on hospital surface simulators, mediating high resistance to desiccation, benzalkonium chloride disinfection and UV radiation. The role of capsule production was minor and species-specific; encapsulated A. baumannii but not K. pneumoniae cells demonstrated slightly increased resistance to desiccation, and neither showed enhanced resistance to benzalkonium chloride. Interestingly, capsule production sensitized K. pneumoniae and A. baumannii to UV radiation. The loss of capsule in K. pneumoniae and A. baumannii enhanced biofilm formation, possibly by increasing cell surface hydrophobicity. In summary, this study confirms the crucial role of biofilm formation in bacterial survival on hospital surfaces. Conversely, encapsulation plays a relatively minor role and may even negatively impact bacterial biofilm formation and hospital survival.

Evaluating the environmental microbiota across four National Health Service hospitals within England

Hospital surfaces contaminated with microbial soiling, such as dry surface biofilms (DSBs), can act as a reservoir for pathogenic micro-organisms, and inhibit their detection and removal during routine cleaning. Studies have recognized that such increases in bioburden can hinder the impact of disinfectants and mask the detection of potential pathogens. Cleanliness within healthcare settings is often determined through routine culture-based analysis, whereby surfaces that exhibit >2.5 colony-forming units (CFU) per cm² pose a risk to patient health; therefore, any underestimation could have detrimental effects. This study quantified microbial growth on high-touch surfaces in four hospitals in England over 19 months. This was achieved using environmental swabs to sample a variety of surfaces within close proximity of the patient, and plating these on to non-specific low nutrient detection agar. The presence of DSBs on surfaces physically removed from the environment was confirmed using real-time imaging through episcopic differential interference contrast microscopy combined with epifluorescence. Approximately two-thirds of surfaces tested exceeded the limit for cleanliness (median 2230 CFU/cm²), whilst 83% of surfaces imaged with BacLight LIVE/DEAD staining confirmed traces of biofilm. Differences in infection control methods, such as choice of surface disinfectants and cleaning personnel, were not reflected in the microbial variation observed and resulting risk to patients. This highlights a potential limitation in the effectiveness of the current standards for all hospital cleaning, and further development using representative clinical data is required to overcome this limitation.

Dry surface biofilms in the food processing industry: An overview on surface characteristics, adhesion and biofilm formation, detection of biofilms, and dry sanitization methods

Bacterial biofilm formation in low moisture food processing (LMF) plants is related to matters of food safety, production efficiency, economic loss, and reduced consumer trust. Dry surfaces may appear dry to the naked eye, however, it is common to find a coverage of thin liquid films and microdroplets, known as microscopic surface wetness (MSW). The MSW may favor dry surface biofilm (DSB) formation. DSB formation is similar in other industries, it occurs through the processes of adhesion, production of extracellular polymeric substances, development of microcolonies and maturation, it is mediated by a quorum sensing (QS) system and is followed by dispersal, leading to disaggregation. Species that survive on dry surfaces develop tolerance to different stresses. DSB are recalcitrant and contribute to higher resistance to sanitation, becoming potential sources of contamination, related to the spoilage of processed products and foodborne disease outbreaks. In LMF industries, sanitization is performed using physical methods without the presence of water. Although alternative dry sanitizing methods can be efficiently used, additional studies are still required to develop and assess the effect of emerging technologies, and to propose possible combinations with traditional methods to enhance their effects on the sanitization process. Overall, more information about the different technologies can help to find the most appropriate method/s, contributing to the development of new sanitization protocols. Thus, this review aimed to identify the main characteristics and challenges of biofilm management in low moisture food industries, and summarizes the mechanisms of action of different dry sanitizing methods (alcohol, hot air, UV-C light, pulsed light, gaseous ozone, and cold plasma) and their effects on microbial metabolism.

An explorative study on the antimicrobial effects and mechanical properties of 3D printed PLA and TPU surfaces loaded with Ag and Cu against nosocomial and foodborne pathogens

Antimicrobial 3D printed surfaces made of PLA and TPU polymers loaded with copper (Cu), and silver (Ag) nanoparticles (NPs) were developed via fused deposition modeling (FDM). The potential antimicrobial effect of the 3D printed surfaces against Escherichia coli, Listeria monocytogenes, Salmonella Typhimurium, and Staphylococcus aureus was evaluated. Furthermore, the mechanical characteristics, including surface topology and morphology, tensile test of specimens manufactured in three different orientations (XY, XZ, and ZX), water absorption capacity, and surface wettability were also assessed. The results showed that both Cu and Ag-loaded 3D printed surfaces displayed a higher inhibitory effect against S. aureus and L. monocytogenes biofilms compared to S. Typhimurium and E. coli biofilms. The results of SEM analysis revealed a low void fraction for the TPU and no voids for the PLA samples achieved through optimization and the small height (0.1 mm) of the printed layers. The best performing specimen in terms of its tensile was XY, followed by ZX and XZ orientation, while it indicated that Cu and Ag-loaded material had a slightly stiffer response than plain PLA. Additionally, Cu and Ag-loaded 3D printed surfaces revealed the highest hydrophobicity compared to the plain polymers making them excellent candidates for biomedical and food production settings to prevent initial bacterial colonization. The approach taken in the current study offers new insights for developing antimicrobial 3D printed surfaces and equipment to enable their application towards the inhibition of the most common nosocomial and foodborne pathogens and reduce the risk of cross-contamination and disease outbreaks.

Essential oils and their active components applied as: free, encapsulated and in hurdle technology to fight microbial contaminations. A review

Microbial contaminations are responsible for many chronic, healthcare, persistent microbial infections and illnesses in the food sector, therefore their control is an important public health challenge. Over the past few years, essential oils (EOs) have emerged as interesting alternatives to synthetic antimicrobials as they are biodegradable, extracted from natural sources and potent antimicrobials. Through their multiple mechanisms of actions and target sites, no microbial resistance has been developed against them till present. Although extensive documentation has been reported on the antimicrobial activity of EOs, comparisons between the use of whole EOs or their active components alone for an antimicrobial treatment are less abundant. It is also essential to have a good knowledge about EOs to be used as alternatives to the conventional antimicrobial products such as chemical disinfectants. Moreover, it is important to focus not only on planktonic vegetative microorganisms, but to study also the effect on more resistant forms like spores and biofilms. The present article reviews the current knowledge on the mechanisms of antimicrobial activities of EOs and their active components on microorganisms in different forms. Additionally, in this review, the ultimate advantages of encapsulating EOs or combining them with other hurdles for enhanced antimicrobial treatments are discussed.

Dehydration Tolerance in Epidemic versus Nonepidemic MRSA Demonstrated by Isothermal Microcalorimetry

Methicillin-resistant Staphylococcus aureus (MRSA) clusters are considered epidemic or nonepidemic based on their ability to spread effectively. Successful transmission could be influenced by dehydration tolerance. Current methods for determination of dehydration tolerance lack accuracy. Here, a climate-controlled in vitro dehydration assay using isothermal microcalorimetry (IMC) was developed and linked with mathematical modeling to determine survival of 44 epidemic versus 54 nonepidemic MRSA strains from France, the United Kingdom, and the Netherlands after 1 week of dehydration. For each MRSA strain, the growth parameters time to end of first growth phase (tmax [h]) and maximal exponential growth rate (μ_m) were deduced from IMC data for 3 experimental replicates, 3 different starting inocula, and before and after dehydration. If the maximal exponential growth rate was within predefined margins (±36% of the mean), a linear relationship between tmax and starting inoculum could be utilized to predict log reduction after dehydration for individual strains. With these criteria, 1,330 of 1,764 heat flow curves (data sets) (75%) could be analyzed to calculate the post-dehydration inoculum size, and thus the log reduction due to dehydration, for 90 of 98 strains (92%). Overall reduction was ~1 log after 1 week. No difference in dehydration tolerance was found between the epidemic and nonepidemic strains. Log reduction was negatively correlated with starting inoculum, indicating better survival of higher inocula. This study presents a framework to quantify bacterial survival. MRSA strains showed great capacity to persist in the environment, irrespective of epidemiological success. This finding strengthens the need for effective surface cleaning to contain MRSA transmission. IMPORTANCE Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of infections globally. While some MRSA clusters have spread worldwide, others are not able to disseminate successfully beyond certain regions despite frequent introduction. Dehydration tolerance facilitates transmission in hospital environments through enhanced survival on surfaces and fomites, potentially explaining differences in transmission success between MRSA clusters. Unfortunately, the currently available techniques to determine dehydration tolerance of cluster-forming bacteria like S. aureus are labor-intensive and unreliable due to their dependence on quantitative culturing. In this study, bacterial survival was assessed in a newly developed assay using isothermal microcalorimetry. With this technique, the effect of drying can be determined without the disadvantages of quantitative culturing. In combination with a newly developed mathematical algorithm, we determined dehydration tolerance of a large number of MRSA strains in a systematic, unbiased, and robust manner.

Technologies to decontaminate bacterial biofilm on hospital surfaces: a potential new role for cold plasma?

Healthcare-associated infections (HCAIs) are a major challenge and the near patient surface is important in harbouring causes such as methicillin-resistant Staphylococcus aureus (MRSA) and Clostridioides difficile. Current approaches to decontamination are sub-optimal and many studies have demonstrated that microbial causes of HCAIs may persist with onward transmission. This may be due to the capacity of these microbes to survive in biofilms on surfaces. New technologies to enhance hospital decontamination may have a role in addressing this challenge. We have reviewed current technologies such as UV light and hydrogen peroxide and also assessed the potential use of cold atmospheric pressure plasma (CAPP) in surface decontamination. The antimicrobial mechanisms of CAPP are not fully understood but the production of reactive oxygen and other species is believed to be important. CAPP systems have been shown to partially or completely remove a variety of biofilms including those caused by Candida albicans, and multi-drug-resistant bacteria such as MRSA. There are some studies that suggest promise for CAPP in the challenge of surface decontamination in the healthcare setting. However, further work is required to define better the mechanism of action. We need to know what surfaces are most amenable to treatment, how microbial components and the maturity of biofilms may affect successful treatment, and how would CAPP be used in the clinical setting.

Prevalence of the fimbrial operon mrkABCD, mrkA expression, biofilm formation and effect of biocides on biofilm formation in carbapenemase-producing Klebsiella pneumoniae isolates belonging or not to high-risk clones

BACKGROUND

The role of mrkA adhesin expression, biofilm production, biofilm viability and biocides in the biofilms of carbapenemase-producing K. pneumoniae isolates was investigated.

METHODS

Seventeen isolates representing different sequence types and carbapenemases were investigated. mrkA expression was determined by real-time RT-PCR. Biofilm production (25°C and 37°C, with and without humidity) was determined by the crystal violet assay. The effect of isopropanol, povidone-iodine, sodium hypochlorite, chlorhexidine digluconate, benzalkonium chloride, ethanol and triclosan on biofilms was determined. The effect of povidone-iodine on biofilm biomass and thickness was also determined by Confocal Laser Scanning Microscopy (CLSM).

RESULTS

mrkA expression ranged 28.2-1.3 (high or intermediate-level; 64% of HR clones) and 21.5-1.3 (50% of non-HR clones). At 25°C biofilm formation was observed in 41% of isolates (absence of humidity) and 35% of isolates (presence of humidity), whereas at 37°C it was observed in 76% of isolates, with and without humidity. At 25°C biofilm producers were more frequently observed in HR clones (45% with humidity and 55% without humidity) than non-HR clones (17% with and without humidity). Biofilm viability from day 21 was higher at 25°C than 37°C. The greatest decrease in biofilm formation was observed with povidone iodine (29% decrease), which also decrease biofilm thickness.

CONCLUSIONS

Biofilm formation in carbapenemase-producing K. pneumoniae is related to mrkA expression. Biofilm formation is affected by temperature (37°C>25°C) whereas humidity has little effect. Biofilm viability is affected by temperature (25°C>37°C). At 25°C, HR clones are more frequently biofilm producers than non-HR clones. Povidone-iodine can decrease biofilm production and biofilm thickness.

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.

Dry surface biofilms: what you need to know

Environmental dry surface biofilms are a new type of biofilm found on dry surfaces, that are not visible to the human eye. Dry surface biofilms harbour multidrug-resistant organisms, are resistant to cleaning and disinfection and cannot be detected by wet or dry swabbing, so may play an important role in the persistence of pathogens in the healthcare environment.

Dual species dry surface biofilms; Bacillus species impact on Staphylococcus aureus survival and surface disinfection

AIMS

Dry surface biofilms (DSB) survive on environmental surfaces throughout hospitals, able to resist cleaning and disinfection interventions. This study aimed to produce a dual species DSB and explore the ability of commercially available wipe products to eliminate pathogens within a dual species DSB and prevent their transfer.

METHODS AND RESULTS

Staphylococcus aureus was grown with two different species of Bacillus on stainless steel discs, over 12 days using sequential hydration and dehydration phases. A modified version of ASTM 2967-15 was used to test six wipe products including one water control with the Fitaflex Wiperator. Staphylococcus aureus growth was inhibited when combined with Bacillus subtilis. Recovery of S. aureus on agar from a dual DSB was not always consistent. Our results did not provide evidence that Bacillus licheniformis protected S. aureus from wipe action. There was no significant difference of S. aureus elimination by antimicrobial wipes between single and dual species DSB. B. licheniformis was easily transferred by the wipe itself and to new surfaces both in a single and dual species DSB, whilst several wipe products inhibited the transfer of S. aureus from wipe. However, S. aureus direct transfer to new surfaces was not inhibited post-wiping.

CONCLUSIONS

Although we observed that the dual DSB did not confer protection of S. aureus, we demonstrated that environmental species can persist on surfaces after disinfection treatment. Industries should test DSB against future products and hospitals should consider carefully the products they choose.

SIGNIFICANCE AND IMPACT OF THE STUDY

To our knowledge, this is the first study reporting on the production of a dual species DSB. Multispecies DSB have been identified throughout the world on hospital surfaces, but many studies focus on single species biofilms. This study has shown that DSB behave differently to hydrated biofilms.