Persistence of Escherichia coli O157 on farm surfaces under different environmental conditions

How long do bacteria, fungi, protozoa, and viruses retain their replication capacity on inanimate surfaces? A systematic review examining environmental resilience versus healthcare-associated infection risk by "fomite-borne risk assessment"

SUMMARYIn healthcare settings, contaminated surfaces play an important role in the transmission of nosocomial pathogens potentially resulting in healthcare-associated infections (HAI). Pathogens can be transmitted directly from frequent hand-touch surfaces close to patients or indirectly by staff and visitors. HAI risk depends on exposure, extent of contamination, infectious dose (ID), virulence, hygiene practices, and patient vulnerability. This review attempts to close a gap in previous reviews on persistence/tenacity by only including articles (n = 171) providing quantitative data on re-cultivable pathogens from fomites for a better translation into clinical settings. We have therefore introduced the new term "replication capacity" (RC). The RC is affected by the degree of contamination, surface material, temperature, relative humidity, protein load, organic soil, UV-light (sunlight) exposure, and pH value. In general, investigations into surface RC are mainly performed in vitro using reference strains with high inocula. In vitro data from studies on 14 Gram-positive, 26 Gram-negative bacteria, 18 fungi, 4 protozoa, and 37 viruses. It should be regarded as a worst-case scenario indicating the upper bounds of risks when using such data for clinical decision-making. Information on RC after surface contamination could be seen as an opportunity to choose the most appropriate infection prevention and control (IPC) strategies. To help with decision-making, pathogens characterized by an increased nosocomial risk for transmission from inanimate surfaces ("fomite-borne") are presented and discussed in this systematic review. Thus, the review offers a theoretical basis to support local risk assessments and IPC recommendations.

Assessing the risk of E. coli contamination from manure application in Chinese farmland by integrating machine learning and Phydrus

This study aims to present a comprehensive study on the risks associated with the residual presence and transport of Escherichia coli (E. coli) in soil following the application of livestock manure in Chinese farmlands by integrating machine learning algorithms with mechanism-based models (Phydrus). We initially review 28 published papers to gather data on E. coli's die-off and attachment characteristics in soil. Machine learning models, including deep learning and gradient boosting machine, are employed to predict key parameters such as the die-off rate of E. coli and first-order attachment coefficient in soil. Then, Phydrus was used to simulate E. coli transport and survival in 23692 subregions in China. The model considered regional differences in E. coli residual risk and transport, influenced by soil properties, soil depths, precipitation, seasonal variations, and regional disparities. The findings indicate higher residual risks in regions such as the Northeast China, Eastern Qinghai-Tibet Plateau, and pronounced transport risks in the fringe of the Sichuan Basin fringe, the Loess Plateau, the North China Plain, the Northeast Plain, the Shigatse Basin, and the Shangri-La region. The study also demonstrates a significant reduction in both residual and transport risks one month after manure application, highlighting the importance of timing manure application and implementing region-specific standards. This research contributes to the broader understanding of pathogen behavior in agricultural soils and offers practical guidelines for managing the risks associated with manure use. This study's comprehensive method offers a potentially valuable tool for evaluating microbial contaminants in agricultural soils across the globe.

Persistence of 'wet wipes' in beach sand: An unrecognised reservoir for localised E. coli contamination

The flushing of wet wipes down toilets leads to blockages of sewerage systems. This, together with unregulated sewage discharge, often results in increasing numbers of wet wipes washing up onto beaches. However, it is unclear how long wet wipes can persist on the beach and whether they pose a prolonged public health risk if contaminated by E. coli. In this mesocosm study, three types of wet wipes (plastic containing, and home and commercially compostable) colonised with E. coli were buried in beach sand and their degradation, tensile strength, and concentration of E. coli was quantified over 15 weeks. Wet wipes containing plastic remained largely intact for 15 weeks, whilst both compostable wet wipes fragmented and degraded. Importantly, E. coli persisted on all three wet wipe types, representing localised reservoirs of E. coli in the sand, which could present a human health risk at the beach.

Relationship between Desiccation Tolerance and Biofilm Formation in Shiga Toxin-Producing Escherichia coli

Shiga toxin-producing Escherichia coli (STEC) is a major concern in the food industry and requires effective control measures to prevent foodborne illnesses. Previous studies have demonstrated increased difficulty in the control of biofilm-forming STEC. Desiccation, achieved through osmotic stress and water removal, has emerged as a potential antimicrobial hurdle. This study focused on 254 genetically diverse E. coli strains collected from cattle, carcass hides, hide-off carcasses, and processing equipment. Of these, 141 (55.51%) were STEC and 113 (44.48%) were generic E. coli. The biofilm-forming capabilities of these isolates were assessed, and their desiccation tolerance was investigated to understand the relationships between growth temperature, relative humidity (RH), and bacterial survival. Only 28% of the STEC isolates had the ability to form biofilms, compared to 60% of the generic E. coli. Stainless steel surfaces were exposed to different combinations of temperature (0 °C or 35 °C) and relative humidity (75% or 100%), and the bacterial attachment and survival rates were measured over 72 h and compared to controls. The results revealed that all the strains exposed to 75% relative humidity (RH) at any temperature had reduced growth (p < 0.001). In contrast, 35 °C and 100% RH supported bacterial proliferation, except for isolates forming the strongest biofilms. The ability of E. coli to form a biofilm did not impact growth reduction at 75% RH. Therefore, desiccation treatment at 75% RH at temperatures of 0 °C or 35 °C holds promise as a novel antimicrobial hurdle for the removal of biofilm-forming E. coli from challenging-to-clean surfaces and equipment within food processing facilities.

Superlattice Nanofilm on a Touchscreen for Photoexcited Bacteria and Virus Killing by Tuning Electronic Defects in the Heterointerface

Currently, the global COVID-19 pandemic has significantly increased the public attention toward the spread of pathogenic viruses and bacteria on various high-frequency touch surfaces. Developing a self-disinfecting coating on a touchscreen is an urgent and meaningful task. Superlattice materials are among the most promising photocatalysts owing to their efficient charge transfer in abundant heterointerfaces. However, excess electronic defects at the heterointerfaces result in the loss of substantial amounts of photogenerated charge carrier. In this study, a ZnOFe₂ O₃ superlattice nanofilm is designed via atomic layer deposition for photocatalytic bactericidal and virucidal touchscreen. Additionally, electronic defects in the superlattice heterointerface are engineered. Photogenerated electrons and holes will be rapidly separated and transferred into ZnO and Fe₂ O₃ across the heterointerfaces owing to the formation of ZnO, FeO, and ZnFe covalent bonds at the heterointerfaces, where ZnO and Fe₂ O₃ function as electronic donors and receptors, respectively. The high generation capacity of reactive oxygen species results in a high antibacterial and antiviral efficacy (>90%) even against drug-resistant bacteria and H1N1 viruses under simulated solar or low-power LED light irradiation. Meanwhile, this superlattice nanofilm on a touchscreen shows excellent light transmission (>90%), abrasion resistance (10⁶ times the round-trip friction), and biocompatibility.

Demonstrating the In Vitro and In Situ Antimicrobial Activity of Oxide Mineral Microspheres: An Innovative Technology to Be Incorporated into Porous and Nonporous Materials

The antimicrobial activity of surfaces treated with zinc and/or magnesium mineral oxide microspheres is a patented technology that has been demonstrated in vitro against bacteria and viruses. This study aims to evaluate the efficiency and sustainability of the technology in vitro, under simulation-of-use conditions, and in situ. The tests were undertaken in vitro according to the ISO 22196:2011, ISO 20473:2013, and NF S90-700:2019 standards with adapted parameters. Simulation-of-use tests evaluated the robustness of the activity under worst-case scenarios. The in situ tests were conducted on high-touch surfaces. The in vitro results show efficient antimicrobial activity against referenced strains with a log reduction of >2. The sustainability of this effect was time-dependent and detected at lower temperatures (20 ± 2.5 °C) and humidity (46%) conditions for variable inoculum concentrations and contact times. The simulation of use proved the microsphere's efficiency under harsh mechanical and chemical tests. The in situ studies showed a higher than 90% reduction in CFU/25 cm² per treated surface versus the untreated surfaces, reaching a targeted value of <50 CFU/cm². Mineral oxide microspheres can be incorporated into unlimited surface types, including medical devices, to efficiently and sustainably prevent microbial contamination.

Inanimate Surfaces as a Source of Hospital Infections Caused by Fungi, Bacteria and Viruses with Particular Emphasis on SARS-CoV-2

The carriers of nosocomial infections are the hands of medical personnel and inanimate surfaces. Both hands and surfaces may be contaminated as a result of contact with the patient, their body fluids, and touching contaminated surfaces in the patient's surroundings. Visually clean inanimate surfaces are an important source of pathogens. Microorganisms have properties thanks to which they can survive in unfavorable conditions, from a few days to several months. Bacteria, viruses and fungi are able to transmit from inanimate surfaces to the skin of the patient and the medical staff. These pathogens include SARS-CoV-2, which can survive on various types of inanimate surfaces, being a potential source of infection. By following the recommendations related to washing and disinfecting hands and surfaces, and using appropriate washing and disinfecting agents with a broad biocidal spectrum, high material compatibility and the shortest duration of action, we contribute to breaking the chain of nosocomial infections.

Study of the persistence of selected Gram-negative bacteria pathogens of healthcare-associated infections on hospital fabrics

BACKGROUND

The ability of healthcare associate infection (HAI) pathogens to persist on fomites is crucial to their transmission within the healthcare setting, this study evaluated the persistence of 3 common HAI pathogens on fabrics materials commonly used in healthcare settings.

METHODS

Persistence of bacteria species on fabric was investigate by inoculating standardized inoculum prepared from the clinical isolates of Pseudomonas aeruginosa, Escherichia coli and Acinetobacter baumannii on sterile swatches of 100% cotton, microfiber and polyester. Viable bacteria persisting on the inoculated fabrics were evaluated immediate after inoculation and subsequently at 96-hour interval for 32 days using the drop plate technique. The effect of moisture on the persistence of the studied bacteria isolates was also evaluated.

RESULTS

Between 3 and 6 log reduction in the viability of the inoculated bacteria cells were observed after 32 days of inoculation on fabrics. Generally, lower viable cells were recovered from the microfiber fabrics compared to others, while higher viable cells were recovered from wet fabrics compared to the dry fabrics in this study.

DISCUSSION AND CONCLUSIONS

This study demonstrated that HAI bacteria pathogens can persist for more than a month on hospital fabrics, and that their persistence can be enhanced by moisture.

Manual emptying of ventilated improved pit latrines and hygiene challenges - a baseline survey in a peri-urban community in KwaZulu-Natal, South Africa

The presence of Escherichia coli and Staphylococcus spp. was determined on the skin, personal protective equipment, the municipal vehicle, and various surfaces at ten households in a peri-urban community (KwaZulu-Natal, South Africa) before and after manual emptying of ventilated improved pit latrines. Surface samples (n = 14) were collected using sterile wet wipes, and target bacteria were detected using standard procedures. Additionally, E. coli was enumerated in soil samples from an area of open defecation (log₁₀ 3.7 MPN/g) and areas where geophagia occurred (log₁₀ 2.7 - log₁₀ 3.3 MPN/g), using a most probable number (MPN) method. The detection frequency for the target bacteria on household surfaces (e.g., the walkway between the pit latrine and the municipal vehicle) and on municipal workers' hands (which were frequently contaminated before pit emptying), occasionally increased after the pits were emptied, indicating that manual pit emptying might pose a potential health risk to workers and community members.

The Fate of Foodborne Pathogens in Manure Treated Soil

The aim of this review was to provide an update on the complex relationship between manure application, altered pathogen levels and antibiotic resistance. This is necessary to protect health and improve the sustainability of this major farming practice in agricultural systems based on high levels of manure production. It is important to consider soil health in relation to environment and land management practices in the context of the soil microflora and the introduction of pathogens on the health of the soil microbiome. Viable pathogens in manure spread on agricultural land may be distributed by leaching, surface run-off, water source contamination and contaminated crop removal. Thus it is important to understand how multiple pathogens can persist in manures and on soil at farm-scale and how crops produced under these conditions could be a potential transfer route for zoonotic pathogens. The management of pathogen load within livestock manure is a potential mechanism for the reduction and prevention of outbreaks infection with Escherichia coli, Listeria Salmonella, and Campylobacter. The ability of Campylobacter, E. coli, Listeria and Salmonella to combat environmental stress coupled with their survival on food crops and vegetables post-harvest emphasizes the need for further study of these pathogens along with the emerging pathogen Providencia given its link to disease in the immunocompromised and its’ high levels of antibiotic resistance. The management of pathogen load within livestock manure has been widely recognized as a potential mechanism for the reduction and prevention of outbreaks infection but any studies undertaken should be considered as region specific due to the variable nature of the factors influencing pathogen content and survival in manures and soil. Mediocre soils that require nutrients could be one template for research on manure inputs and their influence on soil health and on pathogen survival on grassland and in food crops.

Biological Indicators for Fecal Pollution Detection and Source Tracking: A Review

Fecal pollution, commonly detected in untreated or less treated sewage, is associated with health risks (e.g., waterborne diseases and antibiotic resistance dissemination), ecological issues (e.g., release of harmful gases in fecal sludge composting, proliferative bacterial/algal growth due to high nutrient loads) and economy losses (e.g., reduced aqua farm harvesting). Therefore, the discharge of untreated domestic sewage to the environment and its agricultural reuse are growing concerns. The goals of fecal pollution detection include fecal waste source tracking and identifying the presence of pathogens, therefore assessing potential health risks. This review summarizes available biological fecal indicators focusing on host specificity, degree of association with fecal pollution, environmental persistence, and quantification methods in fecal pollution assessment. The development of practical tools is a crucial requirement for the implementation of mitigation strategies that may help confine the types of host-specific pathogens and determine the source control point, such as sourcing fecal wastes from point sources and nonpoint sources. Emerging multidisciplinary bacterial enumeration platforms are also discussed, including individual working mechanisms, applications, advantages, and limitations.

Persistence of Pathogens on Inanimate Surfaces: A Narrative Review

For the prevention of infectious diseases, knowledge about transmission routes is essential. In addition to respiratory, fecal-oral, and sexual transmission, the transfer of pathogens via surfaces plays a vital role for human pathogenic infections-especially nosocomial pathogens. Therefore, information about the survival of pathogens on surfaces can have direct implications on clinical measures, including hygiene guidelines and disinfection strategies. In this review, we reviewed the existing literature regarding viral, bacterial, and fungal persistence on inanimate surfaces. In particular, the current knowledge of the survival time and conditions of clinically relevant pathogens is summarized. While many pathogens persist only for hours, common nosocomial pathogens can survive for days to weeks under laboratory conditions and thereby potentially form a continuous source of transmission if no adequate inactivation procedures are performed.

Investigation of On-Farm Transmission Routes for Contamination of Dairy Cows with Top 7 Escherichia coli O-Serogroups

Shiga toxin-producing Escherichia coli (STEC) are foodborne bacterial pathogens, with cattle a significant reservoir for human infection. This study evaluated environmental reservoirs, intermediate hosts and key pathways that could drive the presence of Top 7 STEC (O157:H7, O26, O45, O103, O111, O121 and O145) on pasture-based dairy herds, using molecular and culture-based methods. A total of 235 composite environmental samples (including soil, bedding, pasture, stock drinking water, bird droppings and flies and faecal samples of dairy animals) were collected from two dairy farms, with four sampling events on each farm. Molecular detection revealed O26, O45, O103 and O121 as the most common O-serogroups, with the greatest occurrence in dairy animal faeces (> 91%), environments freshly contaminated with faeces (> 73%) and birds and flies (> 71%). STEC (79 isolates) were a minor population within the target O-serogroups in all sample types but were widespread in the farm environment in the summer samplings. Phylogenetic analysis of whole genome sequence data targeting single nucleotide polymorphisms revealed the presence of several clonal strains on a farm; a single STEC clonal strain could be found in several sample types concurrently, indicating the existence of more than one possible route for transmission to dairy animals and a high rate of transmission of STEC between dairy animals and wildlife. Overall, the findings improved the understanding of the ecology of the Top 7 STEC in open farm environments, which is required to develop on-farm intervention strategies controlling these zoonoses.

Testing the Antimicrobial Characteristics of Wood Materials: A Review of Methods

Some wood species have antimicrobial properties, making them a better choice over inert surfaces in certain circumstances. However, the organic and porous nature of wood raises questions regarding the use of this material in hygienically important places. Therefore, it is reasonable to investigate the microbial survival and the antimicrobial potential of wood via a variety of methods. Based on the available literature, this review classifies previously used methods into two broad categories: one category tests wood material by direct bacterial contact, and the other tests the action of molecules previously extracted from wood on bacteria and fungi. This article discusses the suitability of these methods to wood materials and exposes knowledge gaps that can be used to guide future research. This information is intended to help the researchers and field experts to select suitable methods for testing the hygienic safety and antimicrobial properties of wood materials.

Designing a typhoid environmental surveillance study: A simulation model for optimum sampling site allocation

Environmental surveillance can be used for monitoring enteric disease in a population by detecting pathogens, shed by infected people, in sewage. Detection of pathogens depends on many factors: infection rates and shedding in the population, pathogen fate in the sewerage network, and also sampling sites, sample size, and assay sensitivity. This complexity makes the design of sampling strategies challenging, which creates a need for mathematical modeling to guide decision making.

In the present study, a model was developed to simulate pathogen shedding, pathogen transport and fate in the sewerage network, sewage sampling, and detection of the pathogen. The simulation study used Salmonella enterica serovar Typhi (S. Typhi) as the target pathogen and two wards in Kolkata, India as the study area. Five different sampling strategies were evaluated for their sensitivity of detecting S. Typhi, by sampling unit: sewage pumping station, shared toilet, adjacent multiple shared toilets (primary sampling unit), pumping station + shared toilets, pumping station + primary sampling units. Sampling strategies were studied in eight scenarios with different geographic clustering of risk, pathogen loss (decay, leakage), and sensitivity of detection assays. A novel adaptive sampling site allocation method was designed, that updates the locations of sampling sites based on their performance. We then demonstrated how the simulation model can be used to predict the performance of environmental surveillance and how it is improved by optimizing the allocation of sampling sites.

The results are summarized as a decision tree to guide the sampling strategy based on disease incidence, geographic distribution of risk, pathogen loss, and the sensitivity of the detection assay. The adaptive sampling site allocation method consistently outperformed alternatives with fixed site locations in most scenarios. In some cases, the optimum allocation method increased the median sensitivity from 45% to 90% within 20 updates.

Escherichia coli concentrations in waters of a reservoir system impacted by cattle and migratory waterfowl

Recent pathogenic Escherichia coli contamination of fresh vegetables that originated from irrigation water has increased awareness and importance of identifying sources of E. coli entering agroecosystems. However, inadequate methods for accurately predicting E. coli occurrence and sources in waterways continue to limit the identification of appropriate and effective prevention and treatment practices. Therefore, the primary objectives of this study were to: (1) Determine the concentration of E. coli during storm events in a hydrologic controlled stream situated in a livestock research operation that is located in the Central Flyway for avian migration in the United States. Great Plains; and (2) Identify trends between E. coli concentrations, grazing rotations, and avian migration patterns. The study sampled five rainfall events (three summer and two fall) to measure E. coli concentrations throughout storm events. A combination of cattle density and waterfowl migration patterns were found to significantly impact E. coli concentrations in the stream. Cattle density had a significant impact during the summer season (p < .0001), while waterfowl density had a significant impact on E. coli concentrations during the fall (p = .0422). The downstream reservoir had exceedance probabilities above the Environmental Protection Agency freshwater criteria > 85% of the growing season following rainfall events. Based on these findings, implementation of best management practices for reducing E. coli concentrations during the growing season and testing of irrigation water prior to application are recommended.

Quantifying the Influence of Relative Humidity, Temperature, and Diluent on the Survival and Growth of Enterobacter aerogenes

Survival of bacteria on surfaces plays an important role in the cross-contamination of food. Temperature, relative humidity (RH), surface type, and inoculum diluent can affect bacterial survival. This study was conducted to examine how temperature, RH, and diluent affect the survival of Enterobacter aerogenes on stainless steel, polyvinyl chloride, and ceramic tile. Although surface type had little effect on survival, temperature had a clear effect. E. aerogenes survival was highest at 7°C and 15 and 50% RH on all surfaces. Some diluents allowed growth under high RH conditions. Cell populations in distilled water inoculated onto each surface decreased initially compared with populations in 1% phosphate-buffered saline (PBS) and 0.1% peptone broth. At 15 and 50% RH, cell populations in 1% PBS declined more sharply after 120 h than did those 0.1% peptone, but populations in both diluents had similar declines up to 3 weeks. Cell populations in 0.1% peptone had the greatest growth and reached the highest population density (∼8 log CFU/mL). Cell populations in PBS and distilled water increased by ∼2 log CFU/mL. When cells in 0.1% peptone were inoculated onto stainless steel at 100% RH, populations increased to ∼7 log CFU per coupon, whereas cells in 1% PBS increased to ∼5 log CFU per coupon followed by a decline over 3 weeks. DMFit and GInaFiT software modeled inactivation on surfaces at all conditions other than 100% RH at 21°C. These findings have important implications for experiments in which microorganisms are inoculated onto foods or food contact surfaces because the growth observed may be affected more by the inoculum diluent at high or uncontrolled RH than by the type of inoculated surface.

Duodenoscope-associated infections: a review

Flexible digestive endoscopes are used for the management of various conditions with hundreds of thousands of therapeutic procedures performed worldwide each year. Duodenoscopes are indispensable tools for the delivery of minimally invasive vital care of numerous pancreaticobiliary disorders. Despite the fact that nosocomial infections after endoscopic retrograde cholangiopancreatography (ERCP) have always been among the most frequently cited postprocedural complications, recent emergence of duodenoscope-transmitted multiple drug-resistant bacterial infections has led to intense research and debate yet with no clearly delineated solution. Duodenoscope-transmitted nosocomial infections have become one of the most visible topics in the recent literature. Hundreds of high-impact articles have therefore been published in the last decade. This review article discusses how such infections were seen in the past and what is the current situation in both research and practice and thus tries to solve some of the unanswered questions for the future. With the persistence of nosocomial infections despite strict adherence to both manufacturer-issued reprocessing protocols and international guidelines and regulations, an urgent and proper microbiologically driven common action is needed for controlling such nosocomial worldwide threat.

A spatial and temporal analysis of risk factors associated with sporadic Shiga toxin-producing Escherichia coli O157 infection in England between 2009 and 2015

Infection with STEC O157 is relatively rare but has potentially serious sequelae, particularly for children. Large outbreaks have prompted considerable efforts designed to reduce transmission primarily from food and direct animal contact. Despite these interventions, numbers of infections have remained constant for many years and the mechanisms leading to many sporadic infections remain unclear.Here, we show that two-thirds of all cases reported in England between 2009 and 2015 were sporadic. Crude rates of infection differed geographically and were highest in rural areas during the summer months. Living in rural areas with high densities of cattle, sheep or pigs and those served by private water supplies were associated with increased risk. Living in an area of lower deprivation contributed to increased risk but this appeared to be associated with reported travel abroad. Fresh water coverage and residential proximity to the coast were not risk factors.To reduce the overall burden of infection in England, interventions designed to reduce the number of sporadic infections with STEC should focus on the residents of rural areas with high densities of livestock and the effective management of non-municipal water supplies. The role of sheep as a reservoir and potential source of infection in humans should not be overlooked.

Microorganisms @ materials surfaces in aircraft: Potential risks for public health? - A systematic review

BACKGROUND

Civil air travel is increasingly recognized as an important potential source for the rapid spread of infectious diseases that were geographically confined in the past, creating international epidemics with great health and socio-economic impact.

OBJECTIVE

The objective of this systematic review is to elucidate the correlations of materials surfaces (composition, structure, properties) and microbial dependences on them in aircraft.

METHODS

The review was prepared according to PRISMA guidelines. Based on a systematic search for studies published before 30 June 2018 in English, we selected and reviewed the contamination, tenacity, and transmission of microorganisms related to specific surfaces within the aircraft cabin. We also reviewed the chemical composition and properties of these surface materials applied within aircraft.

RESULTS

From a total of 828 records 15 articles were included for further analysis in this systematic review, indicating that the aircraft interior surfaces in seat areas (tray tables, armrests, seat covers) and lavatories (door knob handles, toilet flush buttons) are generally colonized by various types of potentially hazardous microorganisms.

CONCLUSIONS

The interior surfaces in seat and lavatory areas could pose higher health risks by causing infections due to their relatively high microbial contamination compared with other interior surfaces. The classification, chemical composition, surface structures and physicochemical properties of materials surfaces have a varied effect on the adhesion, colonization, tenacity and potential transmission of microorganisms within the aircraft cabin. Strategies are proposed for the interruption of surface-related infection chains in the aircraft field.

Quantitative study about the role of environmental conditions in the survival capability of multidrug-resistant bacteria

BACKGROUND

Healthcare-associated infections (HAIs) caused by multidrug-resistant bacteria (MDRB) are of global concern and hospital textiles can contribute to their transmission. MDRB are able to survive on textiles for more than enough time to spread in the environment. Some studies summarized the effect of environmental factors on the duration of bacterial survival, but it remained an open question how these factors influence the quantity of surviving bacteria in a period of a few days, which is relevant from the perspective of HAIs. Investigating this effect can contribute to better understand the spread of MDRB and the emergence of hospital outbreaks.

METHODS

We investigated quantitatively the survival capability of 15 vancomycin-resistant Enterococcus faecium (VRE), 15 methicillin-resistant Staphylococcus aureus (MRSA), 15 multidrug-resistant Acinetobacter baumannii (MACI) and 15 multidrug-resistant Klebsiella pneumoniae (MRKP) in five environmental conditions using the plate count method. We examined the role of nutrients, textile types, temperature and level of relative humidity on bacterial survival after 1-7days of incubation.

RESULTS

Each bacterial group showed higher survival capability on 100% cotton towel than on 100% cotton sheet (P<0.01). MRSAs and VREs showed higher (P<0.01), MACIs showed lower (P=0.02) CFU/swatch values on 100% polyester sheet than on cotton sheet. The survival capability of MRKPs and MRSAs was higher inoculated in nutrient broth than in saline solution (P<0.01). Each bacterial group showed lower survival capability (P<0.01) at body condition (T=35°C, Rh=83%) than at control (T=25°C, Rh=52%).

CONCLUSIONS

Towels proved to be excellent conditions for each bacteria to survive, however chemical composition of the textiles affected differently the survival of Gram-positive and Gram-negative bacteria. These findings could be useful in searching for the source of outbreaks. Organic contamination of the textiles can increase the survival of desiccation-sensitive bacteria, therefore nutrient-rich inoculating medium is recommended in survival studies.

Investigation of Polyaniline and a Functionalised Derivative as Antimicrobial Additives to Create Contamination Resistant Surfaces

Antimicrobial surfaces can be applied to break transmission pathways in hospitals. Polyaniline (PANI) and poly(3-aminobenzoic acid) (P3ABA) are novel antimicrobial agents with potential as non-leaching additives to provide contamination resistant surfaces. The activity of PANI and P3ABA were investigated in suspension and as part of absorbent and non-absorbent surfaces. The effect of inoculum size and the presence of organic matter on surface activity was determined. PANI and P3ABA both demonstrated bactericidal activity against Escherichia coli and Staphylococcus aureus in suspension and as part of an absorbent surface. Only P3ABA showed antimicrobial activity in non-absorbent films. The results that are presented in this work support the use of P3ABA to create contamination resistant surfaces.

Within-Compound Versus Public Latrine Access and Child Feces Disposal Practices in Low-Income Neighborhoods of Accra, Ghana

In crowded urban settlements in low-income countries, many households rely on shared sanitation facilities. Shared facilities are not currently considered "improved sanitation" because of concerns about whether hygiene conditions sufficiently protect users from the feces of others. Prevention of fecal exposure at a latrine is only one aspect of sanitary safety. Ensuring consistent use of latrines for feces disposal, especially child feces, is required to reduce fecal contamination in households and communities. Household crowding and shared latrine access are correlated in these settings, rendering latrine use by neighbors sharing communal living areas as critically important for protecting one's own household. This study in Accra, Ghana, found that household access to a within-compound basic latrine was associated with higher latrine use by children of ages 5-12 years and for disposal of feces of children < 5 years, compared with households using public latrines. However, within-compound access was not associated with improved child feces disposal by other caregivers in the compound. Feces was rarely observed in household compounds but was observed more often in compounds with latrines versus compounds relying on public latrines. Escherichia coli and human adenovirus were detected frequently on household surfaces, but concentrations did not differ when compared by latrine access or usage practices. The differences in latrine use for households sharing within-compound versus public latrines in Accra suggest that disaggregated shared sanitation categories may be useful in monitoring global progress in sanitation coverage. However, compound access did not completely ensure that households were protected from feces and microbial contamination.

Plasma-activated water: a new and effective alternative for duodenoscope reprocessing

INTRODUCTION

Duodenoscopes have been widely used for both diagnostic and therapeutic endoscopic retrograde cholangiopancreatography procedures. Numerous outbreaks of duodenoscope-associated infections involving multidrug-resistant bacteria have recently been reported. Plasma activated water (PAW) has been widely considered an effective agent for surface decontamination and is increasingly used for disinfection of medical equipment. The aim of this study was to evaluate whether the duodenoscopes currently on market are suited for the repeated use of PAW and to test the efficacy of PAW for their disinfection.

MATERIALS AND METHODS

In order to evaluate the disinfection efficacy and the required time of contact, the duodenoscope samples were contaminated by immersing them in fasted-state simulated intestinal fluid containing Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa, prior to PAW exposure. In order to test the duodenoscope polymer compatibility with PAW, a challenge test was conducted by immersing the samples in PAW for 30 minutes daily for 45 consecutive days.

RESULTS

Significant reductions in bacterial populations were achieved after 30 minutes of PAW treatment, indicating a high-level disinfection. Atomic force microscopy and scanning electron microscopy were used to demonstrate that repeated PAW treatment of duodenoscope coating polymer samples did not result in significant differences in morphological surface between the treated and untreated samples. Energy-dispersive X-ray spectroscopy analysis also showed no significant differences between the elemental composition of the duodenoscope coating polymer samples before and after repeated PAW treatment.

CONCLUSION

Considering these preliminary results, PAW could be considered as a new alternative for duodenoscope reprocessing.

'Super' or just 'above average'? Supershedders and the transmission of Escherichia coli O157:H7 among feedlot cattle

Supershedders have been suggested to be major drivers of transmission of Escherichia coli O157:H7 (E. coli O157:H7) among cattle in feedlot environments, despite our relatively limited knowledge of the processes that govern periods of high shedding within an individual animal. In this study, we attempt a data-driven approach, estimating the key characteristics of high shedding behaviour, including effects on transmission to other animals, directly from a study of natural E. coli O157:H7 infection of cattle in a research feedlot, in order to develop an evidence-based definition of supershedding. In contrast to the hypothesized role of supershedders, we found that high shedding individuals only modestly increased the risk of transmission: individuals shedding over 10(3) cfu g(-1) faeces were estimated to pose a risk of transmission only 2.45 times greater than those shedding below that level. The data suggested that shedding above 10(3) cfu g(-1) faeces was the most appropriate definition of supershedding behaviour and under this definition supershedding was surprisingly common, with an estimated prevalence of 31.3% in colonized individuals. We found no evidence that environmental contamination by faeces of shedding cattle contributed to transmission over timescales longer than 3 days and preliminary evidence that higher stocking density increased the risk of transmission.

Eradication of methicillin-resistant Staphylococcus aureus and of Enterobacteriaceae expressing extended-spectrum beta-lactamases on a model pig farm

Colonization of livestock with bacteria resistant to antibiotics is considered a risk for the entry of drug-resistant pathogens into the food chain. For this reason, there is a need for novel concepts to address the eradication of drug-resistant commensals on farms. In the present report, we evaluated the decontamination measures taken on a farm contaminated with methicillin-resistant Staphylococcus aureus (MRSA) and Enterobacteriaceae expressing extended-spectrum β-lactamases (ESBL-E). The decontamination process preceded the conversion from piglet breeding to gilt production. Microbiological surveillance showed that the decontamination measures eliminated the MRSA and ESBL-E strains that were detected on the farm before the complete removal of pigs, cleaning and disinfection of the stable, and construction of an additional stable meeting high-quality standards. After pig production was restarted, ESBL-E remained undetectable over 12 months, but MRSA was recovered from pigs and the environment within the first 2 days. However, spa (Staphylococcus aureus protein A gene) typing revealed acquisition of an MRSA strain (type t034) that had not been detected before decontamination. Interestingly, we observed that a farmworker who had been colonized with the prior MRSA strain (t2011) acquired the new strain (t034) after 2 months. In summary, this report demonstrates that decontamination protocols similar to those used here can lead to successful elimination of contaminating MRSA and ESBL-E in pigs and the stable environment. Nevertheless, decontamination protocols do not prevent the acquisition of new MRSA strains.

Laboratory development and field testing of sentinel toys to assess environmental faecal exposure of young children in rural India

BACKGROUND

Sentinel toys are increasingly used as a method of assessing young children's exposure to faecal pathogens in households in low-income settings. However, there is no consensus on the suitability of different approaches.

METHODS

We evaluated three types of toy balls with different surfaces (plastic, rubber, urethane) in the laboratory to compare the uptake of faecal indicator bacteria (Escherichia coli) on their surface. We performed bacteria survival analysis under different environmental conditions and tested laboratory methods for bacteria removal and recovery. In a field study we distributed sterile urethane balls to children <5 from 360 households in rural India. After 24 hours, we collected and rinsed the toys in sterile water, assayed for thermotolerant coliforms (TTC) and explored associations between the level of contamination and household characteristics.

RESULTS

In the laboratory, urethane foam balls took up more indicator bacteria than the other balls. Bacteria recovery did not differ based on mechanic vs no agitation. Higher temperatures and moisture levels increased bacterial yield. In the field, the only factor associated with a decreased recovery of TTC from the balls was having a soil (unpaved) floor.

CONCLUSIONS

Sentinel toys may be an effective tool for assessing young children's exposure to faecal pathogens. However, even using methods designed to increase bacterial recovery, limited sensitivity may require larger sample sizes.

Veterinary Public Health Approach to Managing Pathogenic Verocytotoxigenic Escherichia coli in the Agri-Food Chain

Verocytoxigenic Escherichia coli (VTEC) comprises many diverse serogroups, but seven serogroups, O157, O26, O103, O145, O111, O21, and O45, have been most commonly linked to severe human infections, though illness has also been reported from a range of other VTEC serogroups. This poses challenges in assessing the risk to humans from the diverse range of VTEC strains that may be recovered from animals, the environment, or food. For routine assessment of risk posed by VTEC recovered from the agri-food chain, the concept of seropathotype can be used to rank the human risk potential from a particular VTEC serogroup on the basis of both serotype (top seven serogroups) and the presence of particular virulence genes (vt in combination with eae, or aaiC plus aggR). But for other VTEC serogroups or virulence gene combinations, it is not currently possible to fully assess the risk posed. VTEC is shed in animal feces and can persist in the farm environment for extended periods ranging from several weeks to many months, posing an ongoing reservoir of contamination for grazing animals, water courses, and fresh produce and for people using farmland for recreational purposes. Appropriate handling and treatment of stored animal waste (slurries and manures) will reduce risk from VTEC in the farm environment. Foods of animal origin such as milk and dairy products and meat may be contaminated with VTEC during production and processing, and the pathogen may survive or grow during processing operations, highlighting the need for well-designed and validated Hazard Analysis Critical Control Point management systems. This article focuses on a veterinary public health approach to managing VTEC, highlighting the various routes in the agri-food chain for transmission of human pathogenic VTEC and general approaches to managing the risk.

Inactivation of vegetative bacterial threat agents on environmental surfaces

Following a wide-area biological terror attack, numerous decontamination technologies, techniques, and strategies will be required for rapid remediation. Establishing an understanding of how disinfectants will perform under field conditions is of critical importance. The purpose of this study was to determine the efficacy of several liquid decontaminants, when used to inactivate vegetative biological agents on environmental surfaces. Aluminum, carpet, concrete, glass, and wood coupons were inoculated with 1×10(8) CFU of Burkholderia mallei, Francisella tularensis, Vibrio cholerae, or Yersinia pestis. Using spray-based application methods, decontamination was then attempted with pH-adjusted bleach, 1% citric acid, 70% ethanol, quaternary ammonia, or Pine-Sol®. Results indicated that decontamination efficacy varied significantly by decontaminant and organism. Materials such as wood are difficult to decontaminate, even when using sporicides. The data presented here will help responders develop efficacious remediation strategies following a large-scale contamination incident.

Escherichia coli in the Environment: Implications for Water Quality and Human Health

Escherichia coli is naturally present in the intestinal tracts of warm-blooded animals. Since E. coli is released into the environment through deposition of fecal material, this bacterium is widely used as an indicator of fecal contamination of waterways. Recently, research efforts have been directed towards the identification of potential sources of fecal contamination impacting waterways and beaches. This is often referred to as microbial source tracking. However, recent studies have reported that E. coli can become "naturalized" to soil, sand, sediments, and algae in tropical, subtropical, and temperate environments. This phenomenon raises issues concerning the continued use of this bacterium as an indicator of fecal contamination. In this review, we discuss the relationship between E. coli and fecal pollution and the use of this bacterium as an indicator of fecal contamination in freshwater systems. We also discuss recent studies showing that E. coli can become an active member of natural microbial communities in the environment, and how this bacterium is being used for microbial source tracking. We also discuss the impact of environmentally-"naturalized" E. coli populations on water quality.

Insight into the prevalence and distribution of microbial contamination to evaluate water management in the fresh produce processing industry

This study provided insight into the degree of microbial contamination in the processing chain of prepacked (bagged) lettuce in two Belgian fresh-cut produce processing companies. The pathogens Salmonella and Listeria monocytogenes were not detected. Total psychrotrophic aerobic bacterial counts (TPACs) in water samples, fresh produce, and environmental samples suggested that the TPAC is not a good indicator of overall quality and best manufacturing practices during production and processing. Because of the high TPACs in the harvested lettuce crops, the process water becomes quickly contaminated, and subsequent TPACs do not change much throughout the production process of a batch. The hygiene indicator Escherichia coli was used to assess the water management practices in these two companies in relation to food safety. Practices such as insufficient cleaning and disinfection of washing baths, irregular refilling of the produce wash baths with water of good microbial quality, and the use of high product/water ratios resulted in a rapid increase in E. coli in the processing water, with potential transfer to the end product (fresh-cut lettuce). The washing step in the production of fresh-cut lettuce was identified as a potential pathway for dispersion of microorganisms and introduction of E. coli to the end product via cross-contamination. An intervention step to reduce microbial contamination is needed, particularly when no sanitizers are used as is the case in some European Union countries. Thus, from a food safety point of view proper water management (and its validation) is a critical point in the fresh-cut produce processing industry.

Mechanism of copper surface toxicity in Escherichia coli O157:H7 and Salmonella involves immediate membrane depolarization followed by slower rate of DNA destruction which differs from that observed for Gram-positive bacteria

We have reported previously that copper I and II ionic species, and superoxide but not Fenton reaction generated hydroxyl radicals, are important in the killing mechanism of pathogenic enterococci on copper surfaces. In this new work we determined if the mechanism was the same in non-pathogenic ancestral (K12) and laboratory (DH5α) strains, and a pathogenic strain (O157), of Escherichia coli. The pathogenic strain exhibited prolonged survival on stainless steel surfaces compared with the other E. coli strains but all died within 10 min on copper surfaces using a 'dry' inoculum protocol (with approximately 10(7)  cfu cm(-2) ) to mimic dry touch contamination. We observed immediate cytoplasmic membrane depolarization, not seen with enterococci or methicillin resistant Staphylococcus aureus, and loss of outer membrane integrity, inhibition of respiration and in situ generation of reactive oxygen species on copper and copper alloy surfaces that did not occur on stainless steel. Chelation of copper (I) and (II) ionic species still had the most significant impact on bacterial survival but protection by d-mannitol suggests hydroxyl radicals are involved in the killing mechanism. We also observed a much slower rate of DNA destruction on copper surfaces compared with previous results for enterococci. This may be due to protection of the nucleic acid by the periplasm and the extensive cell aggregation that we observed on copper surfaces. Similar results were obtained for Salmonella species but partial quenching by d-mannitol suggests radicals other than hydroxyl may be involved. The results indicate that copper biocidal surfaces are effective for Gram-positive and Gram-negative bacteria but bacterial morphology affects the mechanism of toxicity. These surfaces could not only help to prevent infection spread but also prevent horizontal gene transmission which is responsible for the evolution of virulent toxin producing and antibiotic resistant bacteria.

Spread of E. coli O157 infection among Scottish cattle farms: stochastic models and model selection

Identifying risk factors for the presence of Escherichia coli O157 infection on cattle farms is important for understanding the epidemiology of this zoonotic infection in its main reservoir and for informing the design of interventions to reduce the public health risk. Here, we use data from a large-scale field study carried out in Scotland to fit both "SIS"-type dynamical models and statistical risk factor models. By comparing the fit (assessed using maximum likelihood) of different dynamical models we are able to identify the most parsimonious model (using the AIC statistic) and compare it with the model suggested by risk factor analysis. Both approaches identify 2 key risk factors: the movement of cattle onto the farm and the number of cattle on the farm. There was no evidence for a role of other livestock species or seasonality, or of significant risk of local spread. However, the most parsimonious dynamical model does predict that farms can infect other farms through routes other than cattle movement, and that there is a nonlinear relationship between the force of infection and the number of infected farms. An important prediction from the most parsimonious model is that although only approximately 20% farms may harbour E. coli O157 infection at any given time approximately 80% may harbour infection at some point during the course of a year.

High stability of Stx2 phage in food and under food-processing conditions

Bacteriophages (phages) carrying Shiga toxin genes constitute a major virulence attribute in enterohemorrhagic Escherichia coli (EHEC). Several EHEC outbreaks have been linked to food. The survival of such strains in different foods has received much attention, while the fate of the mobile Shiga toxin-converting phages (Stx phages) has been less studied. We have investigated the stability of an Stx phage in several food products and examined how storage, food processing, and disinfection influence the infectivity of phage particles. The study involved a recombinant Stx phage (Δstx::cat) of an E. coli O103:H25 strain from a Norwegian outbreak in 2006. Temperature, matrix, and time were factors of major importance for the stability of phage particles. Phages stored at cooling temperatures (4°C) showed a dramatic reduction in stability compared to those stored at room temperature. The importance of the matrix was evident at higher temperatures (60°C). Phages in ground beef were below the detection level when heated to 60°C for more than 10 min, while phages in broth exposed to the same heating conditions showed a 5-log-higher stability. The phages tolerated desiccation poorly but were infective for a substantial period of time in solutions. Under moist conditions, they also had a high ability to tolerate exposure to several disinfectants. In a dry-fermented sausage model, phages were shown to infect E. coli in situ. The results show that Stx phage particles can maintain their infectivity in foods and under food-processing conditions.

Survival of Escherichia coli O157:H7 on cattle hides

The objective of this study was to determine the time period that Escherichia coli O157:H7 survives on the hides of cattle. Extensive research has been conducted and is ongoing to identify and develop novel preharvest intervention strategies to reduce the presence of E. coli O157:H7 on live cattle and subsequent transfer to processed carcasses. If a reduction of E. coli O157:H7 levels in feces can be achieved through preharvest intervention, it is not known how long it would take for such reductions to be seen on the hide. In the study presented herein, three trials were conducted to follow E. coli O157:H7 hide prevalence over time. For each trial, 36 animals were housed in individual stanchions to minimize or prevent hide contamination events. Through prevalence determination and isolate genotyping with pulsed-field gel electrophoresis, survival of E. coli O157:H7 on the hides of live cattle was determined to be short lived, with an approximate duration of 9 days or less. The results of this study suggest that any preharvest interventions that are to be administered at the end of the finishing period will achieve maximum effect in reducing E. coli O157:H7 levels on cattle hides if given 9 days before the cattle are presented for processing. However, it should be noted that interventions reducing pathogen shedding would also contribute to decreasing hide contamination through lowering the contamination load of the processing plant lairage environment, regardless of the time of application.

Escherichia coli O157:H7: animal reservoir and sources of human infection

This review surveys the literature on carriage and transmission of enterohemorrhagic Escherichia coli (EHEC) O157:H7 in the context of virulence factors and sampling/culture technique. EHEC of the O157:H7 serotype are worldwide zoonotic pathogens responsible for the majority of severe cases of human EHEC disease. EHEC O157:H7 strains are carried primarily by healthy cattle and other ruminants, but most of the bovine strains are not transmitted to people, and do not exhibit virulence factors associated with human disease. Prevalence of EHEC O157:H7 is probably underestimated. Carriage of EHEC O157:H7 by individual animals is typically short-lived, but pen and farm prevalence of specific isolates may extend for months or years and some carriers, designated as supershedders, may harbor high intestinal numbers of the pathogen for extended periods. The prevalence of EHEC O157:H7 in cattle peaks in the summer and is higher in postweaned calves and heifers than in younger and older animals. Virulent strains of EHEC O157:H7 are rarely harbored by pigs or chickens, but are found in turkeys. The bacteria rarely occur in wildlife with the exception of deer and are only sporadically carried by domestic animals and synanthropic rodents and birds. EHEC O157:H7 occur in amphibian, fish, and invertebrate carriers, and can colonize plant surfaces and tissues via attachment mechanisms different from those mediating intestinal attachment. Strains of EHEC O157:H7 exhibit high genetic variability but typically a small number of genetic types predominate in groups of cattle and a farm environment. Transmission to people occurs primarily via ingestion of inadequately processed contaminated food or water and less frequently through contact with manure, animals, or infected people.

Quantification of Persistence of Escherichia coli O157:H7 in Contrasting Soils

Persistence of Escherichia coli (E. coli) O157:H7 in the environment is a major concern to vegetable and fruit growers where farms and livestock production are in close proximity. The objectives were to determine the effects of preplant fumigation treatment on the survival of E. coli O157:H7 in two soils and the effects of indigenous bacterial populations on the survival of this pathogen. Real-time PCR and plate counts were used to quantify the survival of E. coli O157:H7 in two contrasting soils after fumigation with methyl bromide (MeBr) and methyl iodide (MeI). Ten days after fumigation, E. coli O157:H7 counts were significantly lower (P = .0001) in fumigated soils than in the non-fumigated. Direct comparison between MeBr and MeI within each soil indicated that these two fumigants showed similar impacts on E. coli O157:H7 survival. Microbial species diversity as determined by DGGE was significantly higher in clay soil than sandy soil and this resulted in higher initial decline in population in clay soil than in sandy soil. This study shows that if soil is contaminated with E. coli O157:H7, fumigation alone may not eliminate the pathogen, but may cause decrease in microbial diversity which may enhance the survival of the pathogen.

Antimicrobial mortar surfaces for the improvement of hygienic conditions

AIMS

To evaluate the effectiveness of various antimicrobial mortar formulations in inhibiting the growth of a selection of pathogens of environmental and hygienic concern.

METHODS AND RESULTS

Mortar prisms containing triclosan-incorporated fibres or different concentrations of silver copper zeolites were incubated with Escherichia coli, Listeria monocytogenes, Salmonella enterica or Staphylococcus aureus at 4 or 20 degrees C for 24 h. From plate counting, a substantial bactericidal effect (>4 log units) could only be observed for the mortar specimens containing more than 3% zeolites on cement weight base, the effect being more pronounced at 20 degrees C compared to 4 degrees C. No inhibitory effect could be observed for mortar specimens containing antimicrobial fibres. Adenosinetriphosphate (ATP) measurements allowed for a rapid indication of the occurrence of antimicrobial activity.

CONCLUSIONS

In order to obtain a bactericidal effect on mortar surfaces, concentrations of silver copper zeolites of more then 3% are required.

SIGNIFICANCE AND IMPACT OF THE STUDY

To our knowledge, this is the first study in which the effectiveness of various antimicrobial mortar mixtures towards the inhibition of pathogens has been evaluated in a quantitative way. Antimicrobial concrete mixtures can be used for the improvement of the hygienic conditions in a variety of environments.