Aerial dissemination of Clostridium difficile spores

Evaluating the risk of Clostridioides difficile infection from toilet flushing: a quantitative microbial risk assessment and implications for infection control

BACKGROUND

Despite stringent infection control measures, Clostridioides difficile infection (CDI) remains a challenge in healthcare settings, partly due to overlooked transmission vectors such as toilet plume bioaerosols.

AIM

To systematically quantify the risks associated with CDI transmission via toilet flushing and provide critical insights to inform CDI preventive strategies.

METHODS

Impaction sampling was used to quantify airborne C. difficile post-flush and high-contact surfaces were swabbed to assess contamination levels, in a controlled toilet environment. A quantitative microbial risk assessment (QMRA) approach was then used to estimate the risk to subsequent users from contamination by a previously colonized individual.

FINDINGS

A single flush can release C. difficile into the air, with bioaerosol concentrations up to 29.50 ± 10.52 cfu/m3 and deposit about 8-11 cfu on immediate surfaces. Despite a 4.4 log reduction in bacterial concentration within the toilet bowl post-flush, bacteria persist on its inner walls. Relative humidity increases by approximately 31.28% within the first 10 min post-flush, potentially enhancing the viability and transmission of aerosolized C. difficile. The flush button contact and inhalation-followed-by-ingestion in frequent-use hospital settings present the highest risks and exceed US EPA and WHO acceptable infection risk thresholds.

CONCLUSION

The findings of this study necessitate a review of current toilet designs, public health policies and facility management practices to mitigate the overlooked risks of CDI transmission through toilet plume bioaerosols in healthcare settings. Additionally, this study lays a foundation for developing evidence-based interventions aimed at achieving substantial behavioural and infrastructural changes in infection control practices.

Current and Ongoing Developments in Targeting Clostridioides difficile Infection and Recurrence

Clostridioides difficile is a Gram-positive, spore-forming anaerobic bacterial pathogen that causes severe gastrointestinal infection in humans. This review provides background information on C. difficile infection and the pathogenesis and toxigenicity of C. difficile. The risk factors, causes, and the problem of recurrence of disease and current therapeutic treatments are also discussed. Recent therapeutic developments are reviewed including small molecules that inhibit toxin formation, disrupt the cell membrane, inhibit the sporulation process, and activate the host immune system in cells. Other treatments discussed include faecal microbiota treatment, antibody-based immunotherapies, probiotics, vaccines, and violet-blue light disinfection.

Ceragenins and Ceragenin-Based Core-Shell Nanosystems as New Antibacterial Agents against Gram-Negative Rods Causing Nosocomial Infections

The growing number of infections caused by multidrug-resistant bacterial strains, limited treatment options, multi-species infections, high toxicity of the antibiotics used, and an increase in treatment costs are major challenges for modern medicine. To remedy this, scientists are looking for new antibiotics and treatment methods that will effectively eradicate bacteria while continually developing different resistance mechanisms. Ceragenins are a new group of antimicrobial agents synthesized based on molecular patterns that define the mechanism of antibacterial action of natural antibacterial peptides and steroid-polyamine conjugates such as squalamine. Since ceragenins have a broad spectrum of antimicrobial activity, with little recorded ability of bacteria to develop a resistance mechanism that can bridge their mechanism of action, there are high hopes that this group of molecules can give rise to a new family of drugs effective against bacteria resistant to currently used antibiotics. Experimental data suggests that core-shell nanosystems, in which ceragenins are presented to bacterial cells on metallic nanoparticles, may increase their antimicrobial potential and reduce their toxicity. However, studies should be conducted, among others, to assess potential long-term cytotoxicity and in vivo studies to confirm their activity and stability in animal models. Here, we summarized the current knowledge on ceragenins and ceragenin-containing nanoantibiotics as potential new tools against emerging Gram-negative rods associated with nosocomial infections.

Impact of supplementary air filtration on aerosols and particulate matter in a UK hospital ward: a case study

BACKGROUND

Aerosol spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a major problem in hospitals, leading to an increase in supplementary high-efficiency particulate air filtration aimed at reducing nosocomial transmission. This article reports a natural experiment that occurred when an air cleaning unit (ACU) on a medicine for older people ward was switched off accidentally while being commissioned.

AIM

To assess aerosol transport within the ward and determine whether the ACU reduced airborne particulate matter (PM) levels.

METHODS

An ACU was placed in a ward comprising two six-bedded bays plus three single-bed isolation rooms which had previously experienced several outbreaks of coronavirus disease 2019. During commissioning, real-time measurements of key indoor air quality parameters (PM1-10, CO2, temperature and humidity) were collected from multiple sensors over 2 days. During this period, the ACU was switched off accidentally for approximately 7 h, allowing the impact of the intervention on PM to be assessed.

FINDINGS

The ACU reduced the PM counts considerably (e.g. PM1 65.5-78.2%) throughout the ward (P<0.001 all sizes), with positive correlation found for all PM fractions and CO2 (r=0.343-0.817; all P<0.001). PM counts rose/fell simultaneously when the ACU was off, with correlation of PM signals from multiple locations (e.g. r=0.343-0.868; all P<0.001) for particulates <1 μm).

CONCLUSION

Aerosols migrated rapidly between the various ward subcompartments, suggesting that social distancing alone cannot prevent nosocomial transmission of SARS-CoV-2 as this fails to mitigate longer-range (>2 m) transmission. The ACU reduced PM levels considerably throughout the ward space, indicating its potential as an effective intervention to reduce the risk posed by infectious airborne particles.

Practical observations on the use of fluorescent reporter systems in Clostridioides difficile

Fluorescence microscopy is a valuable tool to study a broad variety of bacterial cell components and dynamics thereof. For Clostridioides difficile, the fluorescent proteins CFP^opt, mCherry^Opt and phiLOV2.1, and the self-labelling tags SNAP^Cd and HaloTag, hereafter collectively referred as fluorescent systems, have been described to explore different cellular pathways. In this study, we sought to characterize previously used fluorescent systems in C. difficile cells. We performed single cell analyses using fluorescence microscopy of exponentially growing C. difficile cells harbouring different fluorescent systems, either expressing these separately in the cytosol or fused to the C-terminus of HupA, under defined conditions. We show that the intrinsic fluorescence of C. difficile cells increases during growth, independent of sigB or spo0A. However, when C. difficile cells are exposed to environmental oxygen autofluorescence is enhanced. Cytosolic overexpression of the different fluorescent systems alone, using the same expression signals, showed heterogeneous expression of the fluorescent systems. High levels of mCherry^Opt were toxic for C. difficile cells limiting the applicability of this fluorophore as a transcriptional reporter. When fused to HupA, a C. difficile histone-like protein, the fluorescent systems behaved similarly and did not affect the HupA overproduction phenotype. The present study compares several commonly used fluorescent systems for application as transcriptional or translational reporters in microscopy and summarizes the limitations and key challenges for live-cell imaging of C. difficile. Due to independence of molecular oxygen and fluorescent signal, SNAP^Cd appears the most suitable candidate for live-cell imaging in C. difficile to date.

Effectiveness of air purifiers in intensive care units: an interventional study

BACKGROUND

Effective design and operation of Intensive Care Unit (ICU) ventilation systems is important to prevent hospital-acquired infections. Air purifiers may contribute to that.

AIM

In this study we aimed at detecting the number and types of microorganisms present in the air and on the high touch surfaces in the ICU; evaluating the effectiveness of the air purifying device in reducing the microbial load and thus the rate of nosocomial infections in the ICU.

METHOD

This interventional study was conducted in two similar ICUs between December 2019 and May 2020. Novaerus brand air purifiers were located in the "intervention ICU" for two months. Routine cleaning procedures and HEPA filtered ventilation continued in "control ICU" as well as in the "Intervention ICU". After two months the units were moved to the other ICU for the next two months to reduce any possible bias in the results. Air and surface samples were evaluated.

FINDINGS

The evaluation of the change in the interventional ICU over time revealed a significantly lower colony concentration in the air and on surfaces on Day 60 compared to Day 1 (p_air<0.001 and p_surface<0.001). There was a significant positive correlation between the number of colonies detected and the rate of hospital-acquired infections in the interventional ICU (r:0.406, p:0.049) and in the control ICU (r:0.698, p:0.001).

CONCLUSION

Using air purifiers in addition to the hospital HVAC systems might be an effective way to reduce the microbial load in the air and surfaces and thus hospital-acquired infections.

Bacterial Contamination in Health Care Centers: Differences between Urban and Rural Settings

This study aims to assess the airborne bioburden of rural and urban Portuguese Primary Health Care Centers (PHCC) using active and passive sampling methods and identify the potential differences in airborne microbiota between both environments. The highest total aerobic mesophilic bacterial load in indoor air were found in the Vaccination Room (448 CFU.m−3) in the Rural PHCC and in the Waiting Room (420 CFU.m−3) for Urban PHCC. The total coliforms contamination level in indoor air was detected only in the Cleaning Supplies Room (4 CFU.m−3) in the Urban PHCC. The most frequent bacteria genera identified was Micrococcus (21% Rural PHCC; 31% Urban PHCC). The surface samples showed a highest total aerobic mesophilic bacterial contamination in the Treatment Room (86 × 103 CFU.m−2) from the Rural PHCC and in the Front Office (200 × 103 CFU.m−2) from the Urban PHCC. The electrostatic dust cloth (EDC) samples showed a highest bacterial load in the Urban PHCC. Total aerobic mesophilic bacterial load in settled dust and in the Heating, Ventilating and Air Conditioning (HVAC) filter samples in the Urban PHCC (8 CFU.g−1 and 6 × 103 CFU.m−2) presented higher values compared with the Rural PHCC (1 CFU.g−1 and 2.5 × 103 CFU.m−2). Urban PHCC presented higher bacterial airborne contamination compared with the Rural PHCC for the majority of sampling sites, and when compared with the indoor air quality (IAQ) Portuguese legislation it was the Rural PHCC in two sampling places who did not comply with the established criteria.

One Health in hospitals: how understanding the dynamics of people, animals, and the hospital built-environment can be used to better inform interventions for antimicrobial-resistant gram-positive infections

Despite improvements in hospital infection prevention and control, healthcare associated infections (HAIs) remain a challenge with significant patient morbidity, mortality, and cost for the healthcare system. In this review, we use a One Health framework (human, animal, and environmental health) to explain the epidemiology, demonstrate key knowledge gaps in infection prevention policy, and explore improvements to control Gram-positive pathogens in the healthcare environment. We discuss patient and healthcare worker interactions with the hospital environment that can lead to transmission of the most common Gram-positive hospital pathogens – methicillin-resistant Staphylococcus aureus, Clostridioides (Clostridium) difficile, and vancomycin-resistant Enterococcus – and detail interventions that target these two One Health domains. We discuss the role of animals in the healthcare settings, knowledge gaps regarding their role in pathogen transmission, and the absence of infection risk mitigation strategies targeting animals. We advocate for novel infection prevention and control programs, founded on the pillars of One Health, to reduce Gram-positive hospital-associated pathogen transmission.

Heating, ventilation and air conditioning (HVAC) in intensive care unit

The aim of this review is to describe variation in standards and guidelines on ‘heating, ventilation and air-conditioning (HVAC)’ system maintenance in the intensive care units, across the world, which is required to maintain good ‘indoor air quality’ as an important non-pharmacological strategy in preventing hospital-acquired infections. An online search and review of standards and guidelines published by various societies including American Institute of Architects (AIA), American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), Centers for Disease Control and Prevention (CDC), Department of Health Estates and Facilities Division, Health Technical Memorandum 2025 (HTM) and Healthcare Infection Control Practices Advisory Committee (HICPAC) along with various national expert committee consensus statements, regional and hospital-based protocols available in a public domain were retrieved. Selected publications and textbooks describing HVAC structural aspects were also reviewed, and we described the basic structural details of HVAC system as well as variations in the practised standards of HVAC system in the ICU, worldwide. In summary, there is a need of universal standards for HVAC system with a specific mention on the type of ICU, which should be incorporated into existing infection control practice guidelines.

Bioaerosols generated from toilet flushing in rooms of patients with Clostridioides difficile infection

BACKGROUND

Clostridioides difficile infection (CDI) is the most frequently reported hospital-acquired infection in the United States. Bioaerosols generated during toilet flushing are a possible mechanism for the spread of this pathogen in clinical settings.

OBJECTIVE

To measure the bioaerosol concentration from toilets of patients with CDI before and after flushing.

DESIGN

In this pilot study, bioaerosols were collected 0.15 m, 0.5 m, and 1.0 m from the rims of the toilets in the bathrooms of hospitalized patients with CDI. Inhibitory, selective media were used to detect C. difficile and other facultative anaerobes. Room air was collected continuously for 20 minutes with a bioaerosol sampler before and after toilet flushing. Wilcoxon rank-sum tests were used to assess the difference in bioaerosol production before and after flushing.

SETTING

Rooms of patients with CDI at University of Iowa Hospitals and Clinics.

RESULTS

Bacteria were positively cultured from 8 of 24 rooms (33%). In total, 72 preflush and 72 postflush samples were collected; 9 of the preflush samples (13%) and 19 of the postflush samples (26%) were culture positive for healthcare-associated bacteria. The predominant species cultured were Enterococcus faecalis, E. faecium, and C. difficile. Compared to the preflush samples, the postflush samples showed significant increases in the concentrations of the 2 large particle-size categories: 5.0 µm (P = .0095) and 10.0 µm (P = .0082).

CONCLUSIONS

Bioaerosols produced by toilet flushing potentially contribute to hospital environmental contamination. Prevention measures (eg, toilet lids) should be evaluated as interventions to prevent toilet-associated environmental contamination in clinical settings.

Clostridium difficile Infection of a Total Hip Arthroplasty: Case Report and Review of the Literature

CASE

We describe the case of an 85-year-old woman who presented with worsening right hip pain after a conversion hip replacement. Subsequent imaging demonstrated a gas-containing collection in the lateral thigh. She was taken to the operating room for irrigation and debridement, where intraoperative cultures returned positive for Clostridium difficile. Surgical management was followed by a prolonged course of antibiotics.

CONCLUSIONS

Clostridium difficile as the etiology of infection in a conversion arthroplasty is exceedingly rare. Orthopaedic surgeons and infectious disease specialists should consider C. diff as a potential cause of infection in conversion hip arthroplasty because management options will need to be tailored.

Indoor hospital air and the impact of ventilation on bioaerosols: a systematic review

Healthcare-acquired infections (HAIs) continue to persist in hospitals, despite the use of increasingly strict infection-control precautions. Opportunistic airborne transmission of potentially pathogenic bioaerosols may be one possible reason for this persistence. Therefore, this study aimed to systematically review the concentrations and compositions of indoor bioaerosols in different areas within hospitals and the effects of different ventilation systems. Electronic databases (Medline and Web of Science) were searched to identify articles of interest. The search was restricted to articles published from 2000 to 2017 in English. Aggregate data was used to examine the differences in mean colony forming units per cubic metre (cfu/m³) between different hospital areas and ventilation types. A total of 36 journal articles met the eligibility criteria. The mean total bioaerosol concentrations in the different areas of the hospitals were highest in the inpatient facilities (77 cfu/m³, 95% confidence interval (CI): 55-108) compared with the restricted (13cfu/m³, 95% CI: 10-15) and public areas (14 cfu/m³, 95% CI: 10-19). Hospital areas with natural ventilation had the highest total bioaerosol concentrations (201 cfu/m³, 95% CI: 135-300) compared with areas using conventional mechanical ventilation systems (20 cfu/m³, 95% CI: 16-24). Hospital areas using sophisticated mechanical ventilation systems (such as increased air changes per hour, directional flow and filtration systems) had the lowest total bioaerosol concentrations (9 cfu/m³, 95% CI: 7-13). Operating sophisticated mechanical ventilation systems in hospitals contributes to improved indoor air quality within hospitals, which assists in reducing the risk of airborne transmission of HAIs.

Characterization of Clostridioides difficile isolates recovered from hospitalized patients and the hospitals environment and air: A multicenter study

In healthcare settings, contamination of environment with toxigenic and hypervirulent Clostridioides difficile strains is a serious concern. Here, we assessed whether patients with C. difficile have a role to play in the dissemination of C. difficile in our settings or other sources are implicated in its circulation. A total of 700 fecal specimens and 1435 environmental samples from surfaces, equipment and air of rooms occupied by patients suspected of C. difficile infection were taken from 4 tertiary hospitals in Tehran, Iran between April 2016 and August 2017. Antibiotic susceptibility testing and detection of resistance genes were performed for the environmental isolates. The clinical and environmental isolates of C. difficile were subjected to Pulsed Field Gel Electrophoresis (PFGE) analysis. Forty three (6.14%) and 2 (0.13%) isolates of C. difficile were recovered from the clinical and environmental samples, respectively. In the clinical settings, 2 patients were suspected of recurrent C. difficile infection. Thirty distinct pulsotypes were found among the C. difficile isolates including 28 singletons and 2 common types. One of the two environmental isolates was isolated from floor in the Medical ward, of pulsotype/ribotype/toxinotype PT10/New ribotype/toxinotype V, harbored cdtA/B and tcdC-A, and resistant to ciprofloxacin. The other one was isolated from air of a room in ICU, assigned to PT11/RT001/toxinotype 0, belonged to tcdC-sc3 genotypes and resistant to metronidazole. The environmental isolates did not generate amplicons in PCR assays targeting vanA and nim genes. This study provided evidence for dissemination of genetically diverse strains of C. difficile in hospitalized patients, presence of C. difficile in hospital air, existence of binary toxin positive/antibiotic-resistant isolate on the floor and intra-hospital dissemination of this pathogen.

Toilet plume aerosol generation rate and environmental contamination following bowl water inoculation with Clostridium difficile spores

INTRODUCTION

Clostridium difficile is the leading cause of health care-associated gastric illness. Environmental contamination with C difficile spores is a risk factor for contact transmission, and toilet flushing causes such contamination. This work explores toilet contamination persistence and environmental contamination produced over a series of flushes after contamination.

METHODS

A flushometer toilet was seeded with C difficile spores in a sealed chamber. The toilet was flushed 24times, with postflush bowl water samples and settle plates periodically collected for culturing and counting. Air samples were collected after each of 12 flushes using rotating plate impactors.

RESULTS

Spores were present in bowl water even after 24 flushes. Large droplet spore deposition accumulated over the 24-flush period. Droplet nuclei spore bioaerosol was produced over at least 12 flushes.

CONCLUSIONS

Toilets contaminated with C difficile spores are a persistent source of environmental contamination over an extended number of flushes.

The influence of air-dispersed essential oils from lemon (Citrus limon) and silver fir (Abies alba) on airborne bacteria and fungi in hospital rooms

Airborne bacteria and fungi are an ongoing problem in hospitals. Because of the antimicrobial activities of essential oils (EOs) dispersion of EOs into the air may help to reduce this contamination. The aim of this study was to evaluate the efficacy of the dispersion of selected EOs in reducing the microbial contamination in two hospital wards. The study was carried out at two wards of a 1,227-bed acute-care hospital in Austria. The concentration of airborne bacteria and fungi was measured in patient rooms before and after dispersion of a mixture of Citrus limon EO and Abies alba EO. Before dispersion of the EOs in both wards the mean concentration of bacteria was in a typical range (123 colony forming units (CFU) m^-3 and 104 CFU m^-3) while the mean concentration of fungi differed substantially (155 CFU m^-3 and 28 CFU m^-3). After dispersion of the EOs, a reduction in both bacterial and fungal contamination was observed. In the first two hours the mean concentration of airborne bacteria and fungi was reduced by approximately 40% and 30%-60% respectively. The selected EO mixture is effective in reducing the microbial contamination of the indoor air.

ASID/ACIPC position statement - Infection control for patients with Clostridium difficile infection in healthcare facilities

BACKGROUND

In 2011, the Australasian Society for Infectious Diseases (ASID) and the Australian Infection Control Association (AICA), now known as the Australasian College of Infection Prevention and Control (ACIPC), produced a position statement on infection control requirements for preventing and controlling Clostridium difficile infection (CDI) in healthcare settings.

METHODS

The statement updated in 2017 to reflect new literature available .The authors reviewed the 2011 position statement and critically appraised new literature published between 2011 and 2017 and relevant current infection control guidelines to identify where new evidence had become available or best practice had changed.

RESULTS

The position statement was updated incorporating the new findings. A draft version of the updated position statement was circulated for consultation to members of ASID and ACIPC. The authors responded to all comments received and updated the position statement.

CONCLUSIONS

This updated position statement emphasizes the importance of health service organizations having evidence-based infection prevention and control programs and comprehensive antimicrobial stewardship programs, to ensure the risk of C. difficile acquisition, transmission and infection is minimised.

Cleaning the air with ultraviolet germicidal irradiation lessened contact infections in a long-term acute care hospital

BACKGROUND

This study was designed to determine whether removing bacteria from the air with ultraviolet germicidal irradiation (UV-C) at the room level would reduce infection rates.

METHODS

We reviewed infection data for 12 months before and after UV-C installation in the special care unit (SCU) of a long-term acute care hospital. All patients admitted to the SCU during the study time frame were included. Microbiologic impactor air sampling was completed in August 2015. Shielded UV-C units were installed in 16 patient rooms, the hallway, and the biohazard room. Air sampling was repeated 81 days later.

RESULTS

After UV-C installation, airborne bacteria (colony forming units [CFU] per cubic meter of air) in patient rooms were reduced an average of 42% (175 vs 102 CFU/m³). Common health care-associated infections (HAIs) (Clostridium difficile [8 cases annually vs 1 case, P = .01] and catheter-associated urinary tract infection [20 cases annually vs 9 cases, P = .012]) were reduced significantly as were overall infections, in number of cases (average 8.8 per month vs 3.5, P < .001), and infection rate (average monthly rate 20.3 vs 8.6, P = .001), despite no reported changes to the amount or type of cleaning done, infection control protocols, or reporting procedures. Other infections, traditionally considered contact transmissible (central line-associated bloodstream infection and methicillin-resistant Staphylococcus aureus), also declined noticeably.

CONCLUSIONS

Continuous shielded UV-C reduced airborne bacteria and may also lower the number of HAIs, including those caused by contact pathogens. Reduced infections result in lessened morbidity and lower costs. Health care facilities might wish to consider continuous shielded UV-C at the room level as a possible addition to their infection prevention and control protocols.

Deposition of Bacteria and Bacterial Spores by Bathroom Hot-Air Hand Dryers

Hot-air hand dryers in multiple men's and women's bathrooms in three basic science research areas in an academic health center were screened for their deposition on plates of (i) total bacteria, some of which were identified, and (ii) a kanamycin-resistant Bacillus subtilis strain, PS533, spores of which are produced in large amounts in one basic science research laboratory. Plates exposed to hand dryer air for 30 s averaged 18 to 60 colonies/plate; but interior hand dryer nozzle surfaces had minimal bacterial levels, plates exposed to bathroom air for 2 min with hand dryers off averaged ≤1 colony, and plates exposed to bathroom air moved by a small fan for 20 min had averages of 15 and 12 colonies/plate in two buildings tested. Retrofitting hand dryers with HEPA filters reduced bacterial deposition by hand dryers ∼4-fold, and potential human pathogens were recovered from plates exposed to hand dryer air whether or not a HEPA filter was present and from bathroom air moved by a small fan. Spore-forming colonies, identified as B. subtilis PS533, averaged ∼2.5 to 5% of bacteria deposited by hand dryers throughout the basic research areas examined regardless of distance from the spore-forming laboratory, and these were almost certainly deposited as spores. Comparable results were obtained when bathroom air was sampled for spores. These results indicate that many kinds of bacteria, including potential pathogens and spores, can be deposited on hands exposed to bathroom hand dryers and that spores could be dispersed throughout buildings and deposited on hands by hand dryers.IMPORTANCE While there is evidence that bathroom hand dryers can disperse bacteria from hands or deposit bacteria on surfaces, including recently washed hands, there is less information on (i) the organisms dispersed by hand dryers, (ii) whether hand dryers provide a reservoir of bacteria or simply blow large amounts of bacterially contaminated air, and (iii) whether bacterial spores are deposited on surfaces by hand dryers. Consequently, this study has implications for the control of opportunistic bacterial pathogens and spores in public environments including health care settings. Within a large building, potentially pathogenic bacteria, including bacterial spores, may travel between rooms, and subsequent bacterial/spore deposition by hand dryers is a possible mechanism for spread of infectious bacteria, including spores of potential pathogens if present.

Effect of air pollution on the total bacteria and pathogenic bacteria in different sizes of particulate matter

In recent years, air pollution events have occurred frequently in China during the winter. Most studies have focused on the physical and chemical composition of polluted air. Some studies have examined the bacterial bioaerosols both indoors and outdoors. But few studies have focused on the relationship between air pollution and bacteria, especially pathogenic bacteria. Airborne PM samples with different diameters and different air quality index values were collected in Hangzhou, China from December 2014 to January 2015. High-throughput sequencing of 16S rRNA was used to categorize the airborne bacteria. Based on the NCBI database, the "Human Pathogen Database" was established, which is related to human health. Among all the PM samples, the diversity and concentration of total bacteria were lowest in the moderately or heavily polluted air. However, in the PM2.5 and PM10 samples, the relative abundances of pathogenic bacteria were highest in the heavily and moderately polluted air respectively. Considering the PM samples with different particle sizes, the diversities of total bacteria and the proportion of pathogenic bacteria in the PM10 samples were different from those in the PM2.5 and TSP samples. The composition of PM samples with different sizes range may be responsible for the variances. The relative humidity, carbon monoxide and ozone concentrations were the main factors, which affected the diversity of total bacteria and the proportion of pathogenic bacteria. Among the different environmental samples, the compositions of the total bacteria were very similar in all the airborne PM samples, but different from those in the water, surface soil, and ground dust samples. Which may be attributed to that the long-distance transport of the airflow may influence the composition of the airborne bacteria. This study of the pathogenic bacteria in airborne PM samples can provide a reference for environmental and public health researchers.

Bioaerosol concentrations generated from toilet flushing in a hospital-based patient care setting

Background

In the United States, 1.7 million immunocompromised patients contract a healthcare-associated infection, annually. These infections increase morbidity, mortality and costs of care. A relatively unexplored route of transmission is the generation of bioaerosols during patient care. Transmission of pathogenic microorganisms may result from inhalation or surface contamination of bioaerosols. The toilet flushing of patient fecal waste may be a source of bioaerosols. To date, no study has investigated bioaerosol concentrations from flushing fecal wastes during patient care.

Methods

Particle and bioaerosol concentrations were measured in hospital bathrooms across three sampling conditions; no waste no flush, no waste with flush, and fecal waste with flush. Particle and bioaerosol concentrations were measured with a particle counter bioaerosol sampler both before after a toilet flushing event at distances of 0.15, 0.5, and 1 m from the toilet for 5, 10, 15 min.

Results

Particle concentrations measured before and after the flush were found to be significantly different (0.3-10 μm). Bioaerosol concentrations when flushing fecal waste were found to be significantly greater than background concentrations (p-value = 0.005). However, the bioaerosol concentrations were not different across time (p-value = 0.977) or distance (p-value = 0.911) from the toilet, suggesting that aerosols generated may remain for longer than 30 min post flush. Toilets produce aerosol particles when flushed, with the majority of the particles being 0.3 μm in diameter. The particles aerosolized include microorganisms remaining from previous use or from fecal wastes. Differences in bioaerosol concentrations across conditions also suggest that toilet flushing is a source of bioaerosols that may result in transmission of pathogenic microorganisms.

Conclusions

This study is the first to quantify particles and bioaerosols produced from flushing a hospital toilet during routine patient care. Future studies are needed targeting pathogens associated with gastrointestinal illness and evaluating aerosol exposure reduction interventions.

A model for choosing an automated ultraviolet-C disinfection system and building a case for the C-suite: Two case reports

Environmental disinfection has become the new frontier in the ongoing battle to reduce the risk of health care-associated infections. Evidence demonstrating the persistent contamination of environmental surfaces despite traditional cleaning and disinfection methods has led to the widespread acceptance that there is both a need for reassessing traditional cleaning protocols and for using secondary disinfection technologies. Ultraviolet-C (UV-C) disinfection is one type of no-touch technology shown to be a successful adjunct to manual cleaning in reducing environmental bioburden. The dilemma for the infection preventionist, however, is how to choose the system best suited for their facility among the many UV-C surface disinfection delivery systems available and how to build a case for acquisition to present to the hospital administration/C-suite. This article proposes an approach to these dilemmas based in part on the experience of 2 health care networks.

Presence of Clostridium difficile in pig faecal samples and wild animal species associated with pig farms

AIMS

To determine the presence of Clostridium difficile on fattening pig farms in north-eastern Spain.

METHODS AND RESULTS

Twenty-seven farms were sampled. Pools of pig faecal samples (n = 210), samples of intestinal content from common farm pest species (n = 95) and environment-related samples (n = 93) were collected. Isolates were tested for toxin genes of C. difficile, and typed by PCR-ribotyping and toxinotyping. The minimal inhibitory concentrations of six antimicrobial agents were determined using Etest. Thirty-four isolates were obtained from 12 farms, and 30 (88·2%) had toxin genes. Seven ribotypes were identified. Ribotype 078 and its variant 126 were predominant (52·9%). The same ribotypes were isolated from different animal species on the same farm. None of the isolates were resistant to metronidazole or vancomycin.

CONCLUSIONS

Clostridium difficile was common within the pig farm environment. Most of the positive samples came from pest species or were pest-related environmental samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

Pest species were colonized with toxigenic and antimicrobial-resistant C. difficile strains of the same ribotypes that are found in humans and pigs. Rodents and pigeons may transmit toxigenic and antimicrobial-resistant C. difficile strains that are of the same ribotypes as those occuring in humans.

Mechanisms for floor surfaces or environmental ground contamination to cause human infection: a systematic review

Shoe soles have been shown to transfer infectious microorganisms to floor and ground surfaces. However, the possible modes of transmission of infectious agents from floors or ground surfaces to human contact for infection have not been systematically reviewed. A systematic review was performed on articles indexed in medical databases (Medline, EMBASE, PubMed) using a pre-defined search strategy and MeSH terms (date of last search: 15 March 2016). Only primary research studies in English that investigated the transmission dynamics of infectious microorganisms from floor or ground surfaces to human infection were included. Extraction of articles was performed two independent reviewers using pre-defined data fields in an Excel sheet. Disagreements were resolved by consensus. Thirty studies met the inclusion criteria. Almost all hospital-associated microorganisms including methicillin-resistant Staphylococcus aureus, Clostridium difficile, and multidrug-resistant Gram-negative species were identified on floor or ground surfaces. Several modes of transmission dynamics, most commonly direct contact or aerosolization, were identified. In conclusion, interventions such as efficient cleaning of floor surfaces and vectors that transfer infectious organisms to floors such as shoe soles could be an effective infection control strategy to prevent human disease.

Assessing microbial decontamination of indoor air with particular focus on human pathogenic viruses

Transmission of bacterial, fungal, and viral pathogens is of primary importance in public and occupational health and infection control. Although several standardized protocols have been proposed to target microbes on fomites through surface decontamination, use of microbicidal agents, and cleaning processes, only limited guidance is available on microbial decontamination of indoor air to reduce the risk of pathogen transmission between individuals. This article reviews the salient aspects of airborne transmission of infectious agents, exposure assessment, in vitro assessment of microbicidal agents, and processes for air decontamination for infection prevention and control. Laboratory-scale testing (eg, rotating chambers, wind tunnels) and promising field-scale methodologies to decontaminate indoor air are also presented. The potential of bacteriophages as potential surrogates for the study of airborne human pathogenic viruses is also discussed.

Modeling environmental contamination in hospital single- and four-bed rooms

Aerial dispersion of pathogens is recognized as a potential transmission route for hospital acquired infections; however, little is known about the link between healthcare worker (HCW) contacts' with contaminated surfaces, the transmission of infections and hospital room design. We combine computational fluid dynamics (CFD) simulations of bioaerosol deposition with a validated probabilistic HCW-surface contact model to estimate the relative quantity of pathogens accrued on hands during six types of care procedures in two room types. Results demonstrate that care type is most influential (P < 0.001), followed by the number of surface contacts (P < 0.001) and the distribution of surface pathogens (P = 0.05). Highest hand contamination was predicted during Personal care despite the highest levels of hand hygiene. Ventilation rates of 6 ac/h vs. 4 ac/h showed only minor reductions in predicted hand colonization. Pathogens accrued on hands decreased monotonically after patient care in single rooms due to the physical barrier of bioaerosol transmission between rooms and subsequent hand sanitation. Conversely, contamination was predicted to increase during contact with patients in four-bed rooms due to spatial spread of pathogens. Location of the infectious patient with respect to ventilation played a key role in determining pathogen loadings (P = 0.05).

PRACTICAL IMPLICATIONS

We present the first quantitative model predicting the surface contacts by HCW and the subsequent accretion of pathogenic material as they perform standard patient care. This model indicates that single rooms may significantly reduce the risk of cross-contamination due to indirect infection transmission. Not all care types pose the same risks to patients, and housekeeping performed by HCWs may be an important contribution in the transmission of pathogens between patients. Ventilation rates and positioning of infectious patients within four-bed rooms can mitigate the accretion of pathogens, whereby reducing the risk of missed hand hygiene opportunities. The model provides a tool to quantitatively evaluate the influence of hospital room design on infection risk.

Environmental contamination and hospital-acquired infection: factors that are easily overlooked

There is an ongoing debate about the reasons for and factors contributing to healthcare-associated infection (HAI). Different solutions have been proposed over time to control the spread of HAI, with more focus on hand hygiene than on other aspects such as preventing the aerial dissemination of bacteria. Yet, it emerges that there is a need for a more pluralistic approach to infection control; one that reflects the complexity of the systems associated with HAI and involves multidisciplinary teams including hospital doctors, infection control nurses, microbiologists, architects, and engineers with expertise in building design and facilities management. This study reviews the knowledge base on the role that environmental contamination plays in the transmission of HAI, with the aim of raising awareness regarding infection control issues that are frequently overlooked. From the discussion presented in the study, it is clear that many unknowns persist regarding aerial dissemination of bacteria, and its control via cleaning and disinfection of the clinical environment. There is a paucity of good-quality epidemiological data, making it difficult for healthcare authorities to develop evidence-based policies. Consequently, there is a strong need for carefully designed studies to determine the impact of environmental contamination on the spread of HAI.

CLINICAL AND EPIDEMIOLOGIC CONSIDERATIONS OF CLOSTRIDIUM DIFFICILE IN HARBOR SEALS (PHOCA VITULINA) AT A MARINE MAMMAL REHABILITATION CENTER

Between 1998 and 2008, 15 cases of segmental to diffuse hemorrhagic to necrohemorrhagic enterocolitis were diagnosed in neonatal and weaned juvenile harbor seals (Phoca vitulina) presented from the Vancouver Aquarium Marine Mammal Rescue Centre for rehabilitation. Based on a combination of gross pathology, histopathology, bacterial isolation, and toxin testing, Clostridium difficile enterocolitis was diagnosed. Most pups were anorexic or inappetant and died acutely with few other premonitory signs. Due to ongoing clinical concerns and possible emergence of this pathogen at the facility, efforts to better characterize the disease and understand the epidemiology of C. difficile was initiated in 95 harbor seal pups presented for rehabilitation in a single stranding season. Fecal samples were collected on admission, following completion of antibiotic treatment, and also prerelease or postmortem. All samples were collected fresh and submitted either directly or stored frozen. Fecal samples were inoculated into selective media for culture and screened by enzyme-linked immunosorbant assay (ELISA) for C. difficile toxins A, B, or both. Results of the 95 seals in the study were as follows: on hospital admit 72 seals were sampled, 10 were culture positive, 12 were ELISA positive; following antibiotic therapy 46 seals were sampled noting three culture positive and nine ELISA positive; prior to release 58 seals were sampled noting zero culture positive and one ELISA positive; and on postmortem exam seven seals were sampled noting zero culture positive and two ELISA positive. Clostridium difficile was not deemed to be the cause of death in any of the animals. Although the exact mechanism of disease is unknown, this study suggests that C. difficile infection is not a significant cause of mortality and may be part of the normal flora in harbor seals undergoing rehabilitation. Morbidity and mortality from this bacterium can likely be minimized by judicious use of antibiotics, effective biosecurity-biocontainment protocols, and clean husbandry practices.

Aerosol-Transmitted Infections-a New Consideration for Public Health and Infection Control Teams

Since the emergence of the 2003 severe acute respiratory syndrome (SARS), the 2003 reemergence of avian A/H5N1, the emergence of the 2009 pandemic influenza A/H1N1, the 2012 emergence of Middle East respiratory syndrome (MERS), the 2013 emergence of avian A/H7N9 and the 2014 Ebola virus outbreaks, the potential for the aerosol transmission of infectious agents is now routinely considered in the investigation of any outbreak. Although many organisms have traditionally been considered to be transmitted by only one route (e.g. direct/indirect contact and/or faecal-orally), it is now apparent that the aerosol transmission route is also possible and opportunistic, depending on any potentially aerosol-generating procedures, the severity of illness and the degree and duration of pathogen-shedding in the infected patient, as well as the environment in which these activities are conducted.This article reviews the evidence and characteristics of some of the accepted (tuberculosis, measles, chickenpox, whooping cough) and some of the more opportunistic (influenza, Clostridium difficile, norovirus) aerosol-transmitted infectious agents and outlines methods of detecting and quantifying transmission.

Sterilization of hydrogen peroxide resistant bacterial spores with stabilized chlorine dioxide

Bacillus pumilus SAFR-032 spores isolated from a clean room environment are known to exhibit enhanced resistance to peroxide, desiccation, UV radiation and chemical disinfection than other spore-forming bacteria. The survival of B. pumilus SAFR-032 spores to standard clean room sterilization practices requires development of more stringent disinfection agents. Here, we report the effects of a stabilized chlorine dioxide-based biocidal agent against spores of B. pumilus SAFR-032 and Bacillus subtilis ATCC 6051. Viability was determined via CFU measurement after exposure. Chlorine dioxide demonstrated efficacy towards sterilization of spores of B. pumilus SAFR-032 equivalent or better than exposure to hydrogen peroxide. These results indicate efficacy of chlorine dioxide delivered through a stabilized chlorine dioxide product as a means of sterilization of peroxide- and UV-resistant spores.

Potential sources of Clostridium difficile in human infection

The view of Clostridium difficile infection as a hospital-acquired infection transmitted only by symptomatic patients is changing. Although C difficile is present in food for human consumption, food-borne infection caused by C difficile has never been confirmed. More information on the infective dose and the level of contamination is needed to determine the risk for food-borne exposure to C difficile in humans. The emergence of C difficile polymerase chain reaction (PCR) ribotype 078 in humans is epidemiologically linked to its presence in piglets and calves and their environment, suggesting zoonotic transmission.

Clostridium difficile spores: a major threat to the hospital environment

Clostridium difficile is a Gram-positive, anaerobic spore former and is an important nosocomial and community-acquired pathogenic bacterium. C. difficile infections (CDI) are a leading cause of infections worldwide with elevated rates of morbidity. Despite the fact that two major virulence factors, the enterotoxin TcdA and the cytotoxin TcdB, are essential in the development of CDI, C. difficile spores are the main vehicle of infection, and persistence and transmission of CDI and are thought to play an essential role in episodes of CDI recurrence and horizontal transmission. Recent research has unmasked several properties of C. difficile's unique strategy to form highly transmissible spores and to persist in the colonic environment. Therefore, the aim of this article is to summarize recent advances in the biological properties of C. difficile spores, which might be clinically relevant to improve the management of CDI in hospital environments.

Clostridium difficile infection: molecular pathogenesis and novel therapeutics

The Gram-positive anaerobic bacterium Clostridium difficile produces toxins A and B, which can cause a spectrum of diseases from pseudomembranous colitis to C. difficile-associated diarrhea. A limited number of C. difficile strains also produce a binary toxin that exhibits ADP ribosyltransferase activity. Here, the structure and the mechanism of action of these toxins as well as their role in disease are reviewed. Nosocomial C. difficile infection is often contracted in hospital when patients treated with antibiotics suffer a disturbance in normal gut microflora. C. difficile spores can persist on dry, inanimate surface for months. Metronidazole and oral vancomycin are clinically used for treatment of C. difficile infection but clinical failure and concern about promotion of resistance are motivating the search for novel non-antibiotic therapeutics. Methods for controlling both toxins and spores, replacing gut microflora by probiotics or fecal transplant, and killing bacteria in the anaerobic gut by photodynamic therapy are discussed.

Best practice in healthcare environment decontamination

There is now strong evidence that surface contamination is linked to healthcare-associated infections (HCAIs). Cleaning and disinfection should be sufficient to decrease the microbial bioburden from surfaces in healthcare settings, and, overall, help in decreasing infections. It is, however, not necessarily the case. Evidence suggests that there is a link between educational interventions and a reduction in infections. To improve the overall efficacy and appropriate usage of disinfectants, manufacturers need to engage with the end users in providing clear claim information and product usage instructions. This review provides a clear analysis of the scientific evidence supporting the role of surfaces in HCAIs and the role of education in decreasing such infections. It also examines the debate opposing the use of cleaning versus disinfection in healthcare settings.

Control of Clostridium difficile infection in the hospital setting

Clostridium difficile infection (CDI) has emerged as a leading challenge in the control of healthcare-associated infection (HCAI). The epidemiology of CDI has changed dramatically, this is associated with emergence of 'hypervirulent' strains, particularly PCR ribotype 027. Despite the epidemic spread of these strains, there are recent reports of decreasing incidence from healthcare facilities where multi-facetted targeted control programs have been implemented. We consider these changes in epidemiology and reflect on the tools available to control CDI in the hospital setting. The precise repertoire of measures adopted and emphasis on different interventions will vary, not only between healthcare systems, but also within different institutions within the same healthcare system. Finally, we consider both the sustainability of reductions already achieved, and the potential to reduce CDI further. This takes account of newly emerging data on more recent changes in the epidemiology of CDI, and the potential of novel interventions to decrease the burden of disease.

Cleaning and decontamination of the healthcare environment

Evidence is accumulating for the role of cleaning in controlling hospital infections. Hospital pathogens such as meticillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), norovirus, multi-resistant Gram-negative bacilli and Clostridium difficile persist in the healthcare environment for considerable lengths of time. Cleaning with both detergent and disinfectant-based regimens help control these pathogens in both routine and outbreak situations. The most important transmission risk comes from organisms on frequently handled items because hand contact with a contaminated site could deliver a pathogen to a patient. Cleaning practices should be tailored to clinical risk, near-patient areas and hand-touch-sites and scientifically evaluated for all surfaces and equipment in today’s hospitals.

Particle size and pathogenicity in the respiratory tract

Particle size dictates where aerosolized pathogens deposit in the respiratory tract, thereafter the pathogens potential to cause disease is influenced by tissue tropism, clearance kinetics and the host immunological response. This interplay brings pathogens into contact with a range of tissues spanning the respiratory tract and associated anatomical structures. In animal models, differential deposition within the respiratory tract influences infection kinetics for numerous select agents. Greater numbers of pathogens are required to infect the upper (URT) compared with the lower respiratory tract (LRT), and in comparison the URT infections are protracted with reduced mortality. Pathogenesis in the URT is characterized by infection of the URT lymphoid tissues, cervical lymphadenopathy and septicemia, closely resembling reported human infections of the URT. The olfactory, gastrointestinal, and ophthalmic systems are also infected in a pathogen-dependent manner. The relevant literature is reviewed with respect to particle size and infection of the URT in animal models and humans.

Clostridium difficile exposure as an insidious source of infection in healthcare settings: an epidemiological model

BACKGROUND

Clostridium difficile is the leading cause of infectious diarrhea in hospitalized patients. Its epidemiology has shifted in recent years from almost exclusively infecting elderly patients in whom the gut microbiota has been disturbed by antimicrobials, to now also infecting individuals of all age groups with no recent antimicrobial use.

METHODS

A stochastic mathematical model was constructed to simulate the modern epidemiology of C. difficile in a healthcare setting, and, to compare the efficacies of interventions.

RESULTS

Both the rate of colonization and the incidence of symptomatic disease in hospital inpatients were insensitive to antimicrobial stewardship and to the prescription of probiotics to expedite healthy gut microbiota recovery, suggesting these to be ineffective interventions to limit transmission. Comparatively, improving hygiene and sanitation and reducing average length of stay more effectively reduced infection rates. Although the majority of new colonization events are a result of within-hospital ward exposure, simulations demonstrate the importance of imported cases with new admissions.

CONCLUSIONS

By analyzing a wide range of screening sensitivities, we identify a previously ignored source of pathogen importation: although capturing all asymptomatic as well as symptomatic introductions, individuals who are exposed but not yet colonized will be missed by even a perfectly sensitive screen on admission. Empirical studies to measure the duration of this latent period of infection will be critical to assessing C. difficile control strategies. Moreover, identifying the extent to which the exposed category of individual contributes to pathogen importation should be explicitly considered for all infections relevant to healthcare settings.

Roles of sunlight and natural ventilation for controlling infection: historical and current perspectives

BACKGROUND

Infections caught in buildings are a major global cause of sickness and mortality. Understanding how infections spread is pivotal to public health yet current knowledge of indoor transmission remains poor.

AIM

To review the roles of natural ventilation and sunlight for controlling infection within healthcare environments.

METHODS

Comprehensive literature search was performed, using electronic and library databases to retrieve English language papers combining infection; risk; pathogen; and mention of ventilation; fresh air; and sunlight. Foreign language articles with English translation were included, with no limit imposed on publication date.

FINDINGS

In the past, hospitals were designed with south-facing glazing, cross-ventilation and high ceilings because fresh air and sunlight were thought to reduce infection risk. Historical and recent studies suggest that natural ventilation offers protection from transmission of airborne pathogens. Particle size, dispersal characteristics and transmission risk require more work to justify infection control practices concerning airborne pathogens. Sunlight boosts resistance to infection, with older studies suggesting potential roles for surface decontamination.

CONCLUSIONS

Current knowledge of indoor transmission of pathogens is inadequate, partly due to lack of agreed definitions for particle types and mechanisms of spread. There is recent evidence to support historical data on the effects of natural ventilation but virtually none for sunlight. Modern practice of designing healthcare buildings for comfort favours pathogen persistence. As the number of effective antimicrobial agents declines, further work is required to clarify absolute risks from airborne pathogens along with any potential benefits from additional fresh air and sunlight.

Role of the environment in the transmission of Clostridium difficile in health care facilities

Recent data demonstrate that the contaminated hospital surface environment plays a key role in the transmission of Clostridium difficile. Enhanced environmental cleaning of rooms housing Clostridium difficile-infected patients is warranted, and, if additional studies demonstrate a benefit of "no-touch" methods (eg, ultraviolet irradiation, hydrogen peroxide systems), their routine use should be considered.

Clostridium difficile in foods and animals: history and measures to reduce exposure

Many articles have summarized the changing epidemiology of Clostridium difficile infections (CDI) in humans, but the emerging presence of C. difficile in foods and animals and possible measures to reduce human exposure to this important pathogen have been infrequently addressed. CDIs have traditionally been assumed to be restricted to health-care settings. However, recent molecular studies indicate that this is no longer the case; animals and foods might be involved in the changing epidemiology of CDIs in humans; and genome sequencing is disproving person-to-person transmission in hospitals. Although zoonotic and foodborne transmission have not been confirmed, it is evident that susceptible people can be inadvertently exposed to C. difficile from foods, animals, or their environment. Strains of epidemic clones present in humans are common in companion and food animals, raw meats, poultry products, vegetables, and ready-to-eat foods, including salads. In order to develop science-based prevention strategies, it is critical to understand how C. difficile reaches foods and humans. This review contextualizes the current understanding of CDIs in humans, animals, and foods. Based on available information, we propose a list of educational measures that could reduce the exposure of susceptible people to C. difficile. Enhanced educational efforts and behavior change targeting medical and non-medical personnel are needed.