Sharing is not always a good thing: Use of a DNA marker to investigate the potential for ward-to-ward dissemination of healthcare-associated pathogens

Outbreak simulation on the neonatal ward using silica nanoparticles with encapsulated DNA: unmasking of key spread areas

BACKGROUND

Nosocomial infections pose a serious threat. In neonatal intensive care units (NICUs) especially, there are repeated outbreaks caused by micro-organisms without the sources or dynamics being conclusively determined.

AIM

To use amorphous silica nanoparticles with encapsulated DNA (SPED) to simulate outbreak events and to visualize dissemination patterns in a NICU to gain a better understanding of these dynamics.

METHODS

Three types of SPED were strategically placed on the ward to mimic three different dissemination dynamics among real-life conditions and employee activities. SPED DNA, resistant to disinfectants, was sampled at 22 predefined points across the ward for four days and quantitative polymerase chain reaction analysis was conducted.

FINDINGS

Starting from staff areas, a rapid ward-wide SPED dissemination including numerous patient rooms was demonstrated. In contrast, a primary deployment in a patient room only led to the spread in the staff area, with no distribution in the patient area.

CONCLUSION

This study pioneers SPED utilization in simulating outbreak dynamics. By unmasking staff areas as potential key trigger spots for ward-wide dissemination the revealed patterns could contribute to a more comprehensive view of outbreak events leading to rethinking of hygiene measures and training to reduce the rate of nosocomial infections in hospitals.

Silica nanoparticles with encapsulated DNA (SPED) to trace the spread of pathogens in healthcare

Background

To establish effective infection control protocols, understanding pathogen transmission pathways is essential. Non-infectious surrogate tracers may safely explore these pathways and challenge pre-existing assumptions. We used silica nanoparticles with encapsulated DNA (SPED) for the first time in a real-life hospital setting to investigate potential transmission routes of vancomycin-resistant enterococci in the context of a prolonged outbreak.

Methods

The two study experiments took place in the 900-bed University Hospital Zurich, Switzerland. A three-run ‘Patient experiment’ investigated pathogen transmission via toilet seats in a two-patient room with shared bathroom. First, various predetermined body and fomite sites in a two-bed patient room were probed at baseline. Then, after the first patient was contaminated with SPED at the subgluteal region, both patients sequentially performed a toilet routine. All sites were consequently swabbed again for SPED contamination. Eight hours later, further spread was tested at predefined sites in the patient room and throughout the ward. A two-run ‘Mobile device experiment’ explored the potential transmission by mobile phones and stethoscopes in a quasi-realistic setting. All SPED contamination statuses and levels were determined by real-time qPCR.

Results

Over all three runs, the ‘Patient experiment’ yielded SPED in 59 of 73 (80.8%) predefined body and environmental sites. Specifically, positivity rates were 100% on subgluteal skin, toilet seats, tap handles, and entertainment devices, the initially contaminated patients’ hands; 83.3% on patient phones and bed controls; 80% on intravenous pumps; 75% on toilet flush plates and door handles, and 0% on the initially not contaminated patients’ hands. SPED spread as far as doctor’s keyboards (66.6%), staff mobile phones (33.3%) and nurses’ keyboards (33.3%) after eight hours. The ‘Mobile device experiment’ resulted in 16 of 22 (72.7%) positive follow-up samples, and transmission to the second patient occurred in one of the two runs.

Conclusions

For the first time SPED were used to investigate potential transmission pathways in a real hospital setting. The results suggest that, in the absence of targeted cleaning, toilet seats and mobile devices may result in widespread transmission of pathogens departing from one contaminated patient skin region.

Silica-encapsulated DNA tracers for measuring aerosol distribution dynamics in real-world settings

Aerosolized particles play a significant role in human health and environmental risk management. The global importance of aerosol-related hazards, such as the circulation of pathogens and high levels of air pollutants, have led to a surging demand for suitable surrogate tracers to investigate the complex dynamics of airborne particles in real-world scenarios. In this study, we propose a novel approach using silica particles with encapsulated DNA (SPED) as a tracing agent for measuring aerosol distribution indoors. In a series of experiments with a portable setup, SPED were successfully aerosolized, recaptured, and quantified using quantitative polymerase chain reaction (qPCR). Position dependency and ventilation effects within a confined space could be shown in a quantitative fashion achieving detection limits below 0.1 ng particles per m³ of sampled air. In conclusion, SPED show promise for a flexible, cost-effective, and low-impact characterization of aerosol dynamics in a wide range of settings.

Effectiveness of barrier precautions for prevention of patient-to-patient transfer of a viral DNA surrogate marker

BACKGROUND

Gloves and gowns are used during patient care to reduce contamination of personnel and prevent pathogen transmission.

OBJECTIVE

To determine whether the use of gowns adds a substantial benefit over gloves alone in preventing patient-to-patient transfer of a viral DNA surrogate marker.

METHODS

In total, 30 source patients had 1 cauliflower mosaic virus surrogate marker applied to their skin and clothing and a second to their bed rail and bedside table. Personnel caring for the source patients were randomized to wear gloves, gloves plus cover gowns, or no barrier. Interactions with up to 7 subsequent patients were observed, and the percentages of transfer of the DNA markers were compared among the 3 groups.

RESULTS

In comparison to the no-barrier group (57.8% transfer of 1 or both markers), there were significant reductions in transfer of the DNA markers in the gloves group (31.1% transfer; odds ratio [OR], 0.16; 95% confidence interval [CI], 0.02-0.73) and the gloves-plus-gown group (25.9% transfer; OR, 0.11; 95% CI, 0.01-0.51). The addition of a cover gown to gloves during the interaction with the source patient did not significantly reduce the transfer of the DNA marker (P = .53). During subsequent patient interactions, transfer of the DNA markers was significantly reduced if gloves plus gowns were worn and if hand hygiene was performed (P < .05).

CONCLUSIONS

Wearing gloves or gloves plus gowns reduced the frequency of patient-to-patient transfer of a viral DNA surrogate marker. The use of gloves plus gowns during interactions with the source patient did not reduce transfer in comparison to gloves alone.

Use of simulations to evaluate the effectiveness of barrier precautions to prevent patient-to-patient transfer of healthcare-associated pathogens

BACKGROUND

There is controversy regarding whether the addition of cover gowns offers a substantial benefit over gloves alone in reducing personnel contamination and preventing pathogen transmission.

DESIGN

Simulated patient care interactions.

OBJECTIVE

To evaluate the efficacy of different types of barrier precautions and to identify routes of transmission.

METHODS

In randomly ordered sequence, 30 personnel each performed 3 standardized examinations of mannequins contaminated with pathogen surrogate markers (cauliflower mosaic virus DNA, bacteriophage MS2, nontoxigenic Clostridioides difficile spores, and fluorescent tracer) while wearing no barriers, gloves, or gloves plus gowns followed by examination of a noncontaminated mannequin. We compared the frequency and routes of transfer of the surrogate markers to the second mannequin or the environment.

RESULTS

For a composite of all surrogate markers, transfer by hands occurred at significantly lower rates in the gloves-alone group (OR, 0.02; P < .001) and the gloves-plus-gown group (OR, 0.06; P = .002). Transfer by stethoscope diaphragms was common in all groups and was reduced by wiping the stethoscope between simulations (OR, 0.06; P < .001). Compared to the no-barriers group, wearing a cover gown and gloves resulted in reduced contamination of clothing (OR, 0.15; P < .001), but wearing gloves alone did not.

CONCLUSIONS

Wearing gloves alone or gloves plus gowns reduces hand transfer of pathogens but may not address transfer by devices such as stethoscopes. Cover gowns reduce the risk of contaminating the clothing of personnel.

Use of viral DNA surrogate markers to study routes of transmission of healthcare-associated pathogens

BACKGROUND

The hands of healthcare personnel are the most important source for transmission of healthcare-associated pathogens. The role of contaminated fomites such as portable equipment, stethoscopes, and clothing of personnel in pathogen transmission is unclear.

OBJECTIVE

To study routes of transmission of cauliflower mosaic virus DNA markers from 31 source patients and from environmental surfaces in their rooms.

DESIGN

A 3-month observational cohort study.

SETTING

A Veterans' Affairs hospital.

METHODS

After providing care for source patients, healthcare personnel were observed during interactions with subsequent patients. Putative routes of transmission were identified based on recovery of DNA markers from sites of contact with the patient or environment. To assess plausibility of fomite-mediated transmission, we assessed the frequency of transfer of methicillin-resistant Staphylococcus aureus (MRSA) from the skin of 25 colonized patients via gloved hands versus fomites.

RESULTS

Of 145 interactions involving contact with patients and/or the environment, 41 (28.3%) resulted in transfer of 1 or both DNA markers to the patient and/or the environment. The DNA marker applied to patients' skin and clothing was transferred most frequently by stethoscopes, hands, and portable equipment, whereas the marker applied to environmental surfaces was transferred only by hands and clothing. The percentages of MRSA transfer from the skin of colonized patients via gloved hands, stethoscope diaphragms, and clothing were 52%, 40%, and 48%, respectively.

CONCLUSIONS

Fomites such as stethoscopes, clothing, and portable equipment may be underappreciated sources of pathogen transmission. Simple interventions such as decontamination of fomites between patients could reduce the risk for transmission.

Silica nanoparticles with encapsulated DNA (SPED) - a novel surrogate tracer for microbial transmission in healthcare

Background

The increase in antimicrobial resistance is of worldwide concern. Surrogate tracers attempt to simulate microbial transmission by avoiding the infectious risks associated with live organisms. We evaluated silica nanoparticles with encapsulated DNA (SPED) as a new promising surrogate tracer in healthcare.

Methods

SPED and Escherichia coli were used to implement three experiments in simulation rooms and a microbiology laboratory in 2017–2018. Experiment 1 investigated the transmission behaviour of SPED in a predefined simulated patient-care scenario. SPED marked with 3 different DNA sequences (SPED1-SPED3) were introduced at 3 different points of the consecutive 13 touch sites of a patient-care scenario that was repeated 3 times, resulting in a total of 288 values. Experiment 2 evaluated SPED behaviour following hand cleaning with water and soap and alcohol-based handrub. Experiment 3 compared transfer dynamics of SPED versus E. coli in a laboratory using a gloved finger touching two consecutive sites on a laminate surface after a first purposefully contaminated site.

Results

Experiment 1: SPED adhesiveness on bare skin after a hand-to-surface exposure was high, leading to a dissemination of SPED1–3 on all consecutive surface materials with a trend of decreasing recovery rates, also reflecting touching patterns in concordance with contaminated fingers versus palms. Experiment 2: Hand washing with soap and water resulted in a SPED reduction of 96%, whereas hand disinfection led to dispersal of SPED from the palm to the back of the hand. Experiment 3: SPED and E. coli concentration decreased in parallel with each transmission step – with SPED showing a trend for less reduction and variability.

Conclusions

SPED represent a convenient and safe instrument to simulate pathogen spread by contact transmission simultaneously from an infinite number of sites. They can be further developed as a central asset for successful infection prevention in healthcare.

Germicidal irradiation of portable medical equipment: Mitigating microbes and improving the margin of safety using a novel, point of care, germicidal disinfection pod

Portable medical equipment (PME) can be an important reservoir of pathogens causing health care-associated infections. To address this, a novel, portable ultraviolet disinfection pod (UVDP) that allows for full 360-degree disinfection was developed. This investigation examined efficacy of the UVDP against microorganisms on clean, patient-ready PME. We found that the UVDP significantly reduced the number of recoverable bacteria on PME.

Beyond high-touch surfaces: Portable equipment and floors as potential sources of transmission of health care-associated pathogens

Efforts to improve environmental cleaning and disinfection typically focus primarily on high-touch surfaces in patient rooms. This review highlights evidence that portable equipment and other shared devices and floors may be underappreciated as sources of dissemination of health care-associated pathogens. Practical approaches to address these sites of contamination are emphasized.