Nutrients influence the dynamics of Klebsiella pneumoniae carbapenemase producing enterobacterales in transplanted hospital sinks

A narrative review and update on drain-related outbreaks

BACKGROUND

Outbreaks linked to hospital drainage systems are well reported, and continue to present challenges to incident management teams. Such outbreaks can be protracted and complex, with multi-modal strategies being required for remediation.

AIM

To summarize recent drain-related outbreaks, investigate whether multi-modal control measures are being implemented, and determine any antecedent factors.

METHODS

Databases were searched for drain-related outbreaks over a 5-year period. Search terms employed included 'healthcare drainage outbreaks', 'drain outbreaks', 'drainage system outbreaks', 'sink outbreaks' and 'shower outbreaks'. Information was collected on country of origin, pathogens involved, unit affected, drain types, patient numbers, drainage system interventions, type of drain disinfectant, infection control interventions, typing method, outcomes and any antecedent factors.

FINDINGS

Nineteen drain-related outbreak studies were reviewed. The majority of incidents were due to carbapenemase-producing Enterobacterales, and were from critical care settings. Most (16/19) studies recognized the need for a multi-modal approach. Information on the success of interventions was not documented for all incidents, but 13/19 studies reported no further cases after control measures. Variation in the choice of agent and frequency of application exists with regards to drain disinfection. Seven studies discussed antecedent factors.

CONCLUSION

Despite drain-related outbreaks being reported for the last 24 years and review articles on the subject, outbreaks continue to pose significant challenges. There is currently no UK guidance on the management of drain-related outbreaks or the design of new buildings to mitigate the risk. Addressing the challenges from hospital drainage systems should be considered a priority by agencies and guidance developers.

Carbapenemase-producing Enterobacterales isolated from hospital sinks: molecular relationships with isolates from patients and the change in contamination status after daily disinfection with sodium hypochlorite

Objective

This study aimed to investigate the contamination status of hospital sinks with carbapenemase-producing Enterobacterales (CPE), the efficacy of daily cleaning with sodium hypochlorite, and the relationships between CPEs isolated from contaminated sinks and patients.

Design

Pre/postintervention surveys of the CPE-contaminated sinks.

Setting

Hospital wards including pediatric intensive care unit in a children's hospital.

Participants

Consenting CPE-colonized patients admitted between November 2018 and June 2021 in our hospital.

Methods

Environmental culture of 180 sinks from nine wards in our hospital was performed three times with an interval of 2 years (2019, 2021, 2023). Molecular typing of the isolated strains from the sinks and patients was performed. After the first surveillance culture, we initiated daily disinfection of the sinks using sodium hypochlorite.

Results

Before the intervention, we detected 30 CPE-positive sinks in 2019. After the intervention with sodium hypochlorite, we observed a substantial decline in the number of sinks contaminated with CPE; 13 in 2021 and 6 in 2023. However, the intervention did not significantly reduce the number of CPE-contaminated sinks used for the disposal of nutrition-rich substances. The CPE isolates from the patients and those from the sinks of the wards or floors where they were admitted tended to have similar pulse-field gel electrophoresis patterns.

Conclusion

Contaminated sinks could be reservoirs of disseminating CPE to the patients. Daily disinfection of sinks with sodium hypochlorite may be effective in eliminating CPE, although the effect could be weaker in sinks with a greater risk of contact with nutrition-rich substances.

Evaluating the antibacterial efficacy of a silver nanocomposite surface coating against nosocomial pathogens as an antibiofilm strategy to prevent hospital infections

Antimicrobial nanocoatings may be a means of preventing nosocomial infections, which account for significant morbidity and mortality. The role of hospital sink traps in these infections is also increasingly appreciated. We describe the preparation, material characterization and antibacterial activity of a pipe cement-based silver nanocoating applied to unplasticized polyvinyl chloride, a material widely used in wastewater plumbing. Three-dimensional surface topography imaging and scanning electron microscopy showed increased roughness in all surface finishes versus control, with grinding producing the roughest surfaces. Silver stability within nanocoatings was >99.89% in deionized water and bacteriological media seeded with bacteria. The nanocoating exhibited potent antibiofilm (99.82-100% inhibition) and antiplanktonic (99.59-99.99% killing) activity against three representative bacterial species and a microbial community recovered from hospital sink traps. Hospital sink trap microbiota were characterized by sequencing the 16S rRNA gene, revealing the presence of opportunistic pathogens from genera including Pseudomonas, Enterobacter and Clostridioides. In a benchtop model sink trap system, nanocoating antibiofilm activity against this community remained significant after 11 days but waned following 25 days. Silver nanocoated disks in real-world sink traps in two university buildings had a limited antibiofilm effect, even though in vitro experiments using microbial communities recovered from the same traps demonstrated that the nanocoating was effective, reducing biofilm formation by >99.6% and killing >98% of planktonic bacteria. We propose that conditioning films forming in the complex conditions of real-world sink traps negatively impact nanocoating performance, which may have wider relevance to development of antimicrobial nanocoatings that are not tested in the real-world.

Infection prevention and control policy implementation for CPE: a cross-sectional national survey of healthcare workers reveals knowledge gaps and suboptimal practices

BACKGROUND

In 2017, Ireland pioneered a unique response to the worsening epidemiology of carbapenemase-producing Enterobacterales (CPE), declaring a national public health emergency. Subsequently, CPE mitigation guidelines and policies were implemented in acute hospitals, focused on patient screening and outbreak management, often by healthcare workers (HCWs) with limited background in infection prevention and control (IPC). CPE risks from sinks and drains remain inadequately controlled.

AIMS

To compare CPE awareness, perceptions of the role of the environment in CPE transmission, and disposal practices of liquid waste from clinical handwashing sinks between IPC HCWs and non-IPC HCWs in Ireland.

METHODS

Between December 2022 and March 2023, HCWs employed in acute hospitals in Ireland between 2017 and 2022 were invited to participate anonymously in a 30-question digital survey.

FINDINGS

Responses (N=283) were received across several clinical disciplines. In total, 21.6% of respondents were working or had previously worked in IPC roles, 84.1% of whom reported no IPC-related learning needs. In comparison with non-IPC HCWs, more IPC HCWs perceived a risk of pathogen transmission from clean water plumbing (68.9% vs 39.2%; P<0.001) and waste/drainage plumbing (81.2% vs 43.7%; P<0.001). Among nursing and medical staff, only 5.6% of IPC HCWs used clinical handwashing sinks for disposal of liquid waste, compared with 60% of non-IPC HCWs (P<0.001). In comparison with non-IPC HCWs, a greater proportion of IPC HCWs reported that they had witnessed colleagues routinely discarding liquid waste (including nutritional products, antimicrobials and patient body fluids) via clinical handwashing sinks (88.9% vs 77.9%) CONCLUSIONS: Although there is general awareness of the role of the built environment in pathogen transmission, including CPE, familiarity with sink/water-related transmission is greater among IPC HCWs. There may be opportunities to improve disposal practices for liquid waste through education targeting non-IPC HCWs.

Nutritional drinks and enteral feeds promote the growth of carbapenemase-producing Enterobacterales in conditions that simulate disposal in hospital sinks

BACKGROUND

Studies have shown that nutritional products are discarded via handwash sinks by healthcare workers, and this practice may promote bacterial growth, including growth of pathogens such as carbapenemase-producing Enterobacterales (CPE). Outbreaks and acquisition of CPE in nosocomial settings are associated with negative outcomes for patients and hospitals.

OBJECTIVES

To investigate the potential growth-promoting effect of nutritional support drinks (NSDs) and enteral tube-feed products (ETFPs) on CPE.

METHODS

Six different CPE strains were grown in five different diluted NSDs, five different diluted ETFPs, Mueller-Hinton broth (MHB) and M9 minimal salts media to simulate discarding a small volume of nutritional product in a u-bend, already containing liquid. CPE were enumerated at 0 h, 6 h and 24 h, and compared using two-way analysis of variance and Dunett test, with confidence levels at 95%. Spearman's r was used to measure the strength of correlation between component concentrations in nutritional products and CPE growth.

RESULTS

All NSDs and ETFPs promoted CPE growth that exceeded both M9 (negative growth control) and MHB (positive growth control). In several cases, growth in NSDs/ETFPs was significantly greater compared with growth in MHB.

CONCLUSION

Nutritional products support CPE growth under in-vitro conditions. The propensity of CPE to survive in drain pipework suggests that inappropriate product disposal may further nourish established CPE in these environmental reservoirs. The growth observed in diluted NSDs and ETFPs shows that modifiable practices should be optimized to mitigate the potential risk of CPE transmission from these reservoirs.

Environmental Contamination and Persistence of Clostridioides difficile in Hospital Wastewater Systems

Clostridioides difficile produces an environmentally resistant dormant spore morphotype that infected patients shed to the hospital environment. C. difficile spores persist in clinical reservoirs that are not targeted by hospital routine cleaning protocols. Transmissions and infections from these reservoirs present a hazard to patient safety. This study aimed to assess the impact of patients acutely suffering from C. difficile-associated diarrhea (CDAD) on C. difficile environmental contamination to identify potential reservoirs. Twenty-three hospital rooms accommodating CDAD inpatients with corresponding soiled workrooms of 14 different wards were studied in a German maximum-care hospital. Additionally, four rooms that never accommodated CDAD patients were examined as negative controls. Stagnant water and biofilms from sinks, toilets, and washer disinfector (WD) traps as well as swabs from cleaned bedpans and high-touch surfaces (HTSs) were sampled. For detection, a culture method was used with selective medium. A latex agglutination assay and a Tox A/B enzyme-linked immunosorbent assay were performed with suspect colonies. Stagnant water and biofilms in hospital traps (29%), WDs (34%), and HTSs (37%) were found to be reservoirs for large amounts of C. difficile during the stay of CDAD inpatients that decreased but could persist 13 ± 6 days after their discharge (13%, 14%, and 9.5%, respectively). Control rooms showed none or only slight contamination restricted to WDs. A short-term cleaning strategy was implemented that reduced C. difficile in stagnant water almost entirely. IMPORTANCE Wastewater pipes are microbial ecosystems. The potential risk of infection emanating from the wastewater for individuals is often neglected, since it is perceived to remain in the pipes. However, sewage systems start with siphons and are thus naturally connected to the outside world. Wastewater pathogens do not only flow unidirectionally to wastewater treatment plants but also retrogradely, e.g., through splashing water from siphons to the hospital environment. This study focused on the pathogen C. difficile, which can cause severe and sometimes fatal diarrheas. This study shows how patients suffering from such diarrheas contaminate the hospital environment with C. difficile and that contamination persists in siphon habitats after patient discharge. This might pose a health risk for hospitalized patients afterward. Since this pathogen's spore morphotype is very environmentally resistant and difficult to disinfect, we show a cleaning measure that can almost entirely eliminate C. difficile from siphons.

Aspects and problems associated with the water services to be considered in intensive care units

Background

Water is a product taken for granted and assumed to be a safe commodity in intensive care units (ICU). Biofilm readily becomes established in complex water services presenting a risk to vulnerable patients. Harboured within biofilms are opportunistic pathogens which can be transmitted via hand contact, splashing, aerosol and indirect contact through medical equipment. Evidence linking the role of water services in transmission of infection to patients in ICUs has increased in recent years.

Aims

This research based commentary set out to identify current problems with water and wastewater systems in ICU settings.

Methods

Databases and open source information was used to obtain data on current water and wastewater-related issues in ICU settings. This and the authors experiences have been used to describe current challenges.

Findings

the authors found a number of problems with water systems in ICU to which there has not been a cohesive response in terms of guidance to support users and designers. The resultant void permits new projects to proceed with suboptimal and designs which place patients and staff at risk.

Discussion

Hand hygiene stations are frequently misused or close enough to patients such that splashing poses a transmission risk. The wastewater system (drain) also presents a risk, from where Gram-negative antibiotic resistant organisms may be dispersed resulting in untreatable patient infections. The water and wastewater system provide a superhighway for the movement of pathogenic microorganisms and these risks need to be addressed if we are to safeguard vulnerable users in ICU.

Scavenging of reactive oxygen species effectively reduces Pseudomonas aeruginosa biofilms through disrupting policing

Biofilm formation is likely to contribute greatly to antibiotic resistance in bacteria and therefore the efficient removal of bacterial biofilms needs addressing urgently. Here, we reported that the supplement of non-inhibitory concentration of N-acetyl-L-cysteine (NAC), a common reactive oxygen species (ROS) scavenger, can significantly reduce the biomass of mature Pseudomonas aeruginosa biofilms (corroborated by crystal violet assay and laser scanning confocal microscopy). 1 mM NAC increased the cheater (ΔlasR mutant) frequency to 89.4 ± 1.5% in the evolved PAO1 after the 15-day treatment. Scavenging of ROS by NAC induced the collapse of P. aeruginosa biofilms, but it did not alter quorum sensing-regulated genes expression (e.g., hcnC and cioAB) and hydrogen cyanide production. The replenishment of public good protease contributed to the recovery of biofilm biomass, indicating the role of disrupting policing in biofilm inhibition. Furthermore, 7 typical ROS scavengers (e.g., superoxide dismutase, catalase and peroxidase, etc.) also effectively inhibited mature P. aeruginosa biofilms. This study demonstrates that scavenging of ROS can promote the selective control of P. aeruginosa biofilms through policing disruption as a targeted biofilm control strategy in complex water environments.

Hospital sink traps as a potential source of the emerging multidrug-resistant pathogen Cupriavidus pauculus: characterization and draft genome sequence of strain MF1

Introduction.Cupriavidus pauculus is historically found in soil and water but has more recently been reported to cause human infection and death. Hospital sink traps can serve as a niche for bacterial persistence and a platform for horizontal gene transfer, with evidence of dissemination of pathogens in hospital plumbing systems driving nosocomial infection.

Gap Statement. This paper presents the first C. pauculus strain isolated from a hospital sink trap. There are only six genome assemblies available on NCBI for C. pauculus; two of these are PacBio/Illumina hybrids. This paper presents the first ONT/Illumina hybrid assembly, with five contigs. The other assemblies available consist of 37, 38, 111 and 227 contigs. This paper also presents data on biofilm formation and lethal dose in Galleria mellonella; there is little published information describing these aspects of virulence.

Aim. The aims were to identify the isolate found in a hospital sink trap, characterize its genome, and assess whether it could pose a risk to human health.

Methodology. The genome was sequenced, and a hybrid assembly of short and long reads produced. Antimicrobial susceptibility was determined by the broth microdilution method. Virulence was assessed by measuring in vitro biofilm formation compared to Pseudomonas aeruginosa and in vivo lethality in Galleria mellonella larvae.

Results. The isolate was confirmed to be a strain of C. pauculus, with a 6.8 Mb genome consisting of 6468 coding sequences and an overall G+C content of 63.9 mol%. The genome was found to contain 12 antibiotic resistance genes, 8 virulence factor genes and 33 metal resistance genes. The isolate can be categorized as resistant to meropenem, amoxicillin, amikacin, gentamicin and colistin, but susceptible to cefotaxime, cefepime, imipenem and ciprofloxacin. Clear biofilm formation was seen in all conditions over 72 h and exceeded that of P. aeruginosa when measured at 37 °C in R2A broth. Lethality in G. mellonella larvae over 48 h was relatively low.

Conclusion. The appearance of a multidrug-resistant strain of C. pauculus in a known pathogen reservoir within a clinical setting should be considered concerning. Further work should be completed to compare biofilm formation and in vivo virulence between clinical and environmental strains, to determine how easily environmental strains may establish human infection. Infection control teams and clinicians should be aware of the emerging nature of this pathogen and further work is needed to minimize the impact of contaminated hospital plumbing systems on patient outcomes.

Supplemental nutrients stimulate the amplification of carbapenemase-producing Klebsiella pneumoniae (CPKP) in a sink drain in vitro biofilm reactor model

Liquid wastes (LW) disposed in hospital handwashing sinks may affect colonization of sink P-traps by carbapenemase-producing Klebsiella pneumoniae (CPKP), causing CPKP dispersal into the patient care environment. This study aimed to determine the effect of LW on biofilm formation and CPKP colonization in a P-Trap model (PTM). PTMs containing polymicrobial biofilms grown in autoclaved municipal tap water (ATW) supplemented with 5% dextrose in water (D5W), nutritional shake (Shake), sugar-based soft drink (Soda), or ATW were inoculated with K. pneumoniae ST258 KPC+ (ST258) or K. pneumoniae CAV1016 (CAV1016) and sampled after 7, 14, and 21 d. Biofilm bio-volume, mean thickness, and heterotrophic plate counts were significantly reduced and roughness coefficient significantly increased by Soda compared with D5W, Shake, or ATW. CPKP were significantly reduced by Soda but significantly amplified by D5W (ST258; CAV1016, 7 d) and Shake (ST258) suggesting that reducing LW disposal in sinks may reduce CPKP dispersal into patient care environments.

Long-term contamination of sink drains by carbapenemase-producing Enterobacterales in three intensive care units: characteristics and transmission to patients

This study aimed to describe the contamination of sink drains (SDs) with carbapenemase-producing Enterobacterales (CPE) in three intensive care units (ICUs), and to assess the risk of transmission to hospitalized patients. All SDs were sampled monthly for CPE screening by culture. Rectal screening for CPE carriage was conducted weekly for hospitalized patients. CPE were isolated from 22% of SD samples. Some SDs remained colonized with the same strain for several months. No CPE acquisition occurred among hospitalized patients during the study. Certain strategies, such as systematic sampling of SDs in ICUs for screening for contamination by CPE, should be discouraged apart from during outbreaks.

Risk Factors Associated with Carbapenemase-Producing Enterobacterales (CPE) Positivity in the Hospital Wastewater Environment

Klebsiella pneumoniae carbapenemase-producing organisms (KPCOs) are bacteria that are resistant to most antibiotics and thus are challenging to treat when they cause infections in patients. These organisms can be acquired by patients who are hospitalized for other reasons, complicating their hospital stay and even leading to death. Hospital wastewater sites, such as sink drains and toilets, have played a role in many reported outbreaks over the past decade. The significance of our research is in identifying risk factors for environmental positivity for KPCOs, which will facilitate further work to prevent transmission of these organisms to patients from the hospital environment.

Hospital wastewater is an increasingly recognized reservoir for resistant Gram-negative organisms. Factors involved in establishment and persistence of Klebsiella pneumoniae carbapenemase-producing organisms (KPCOs) in hospital wastewater plumbing are unclear. This study was conducted at a hospital with endemic KPCOs linked to wastewater reservoirs and robust patient perirectal screening for silent KPCO carriage. Over 5 months, both rooms occupied and rooms not occupied by KPCO-positive patients were sampled at three wastewater sites within each room (sink drain, sink P-trap, and toilet or hopper). Risk factors for KPCO positivity were assessed using logistic regression. Whole-genome sequencing (WGS) identified environmental seeding by KPCO-positive patients. A total of 219/475 (46%) room sampling events were KPCO positive in at least one wastewater site. KPCO-positive patient exposure was associated with increased risk of environmental positivity for the room and toilet/hopper. Previous positivity and intensive care unit room type were consistently associated with increased risk. Tube feeds were associated with increased risk for the drain, while exposure to patients with Clostridioides difficile was associated with decreased risk. Urinary catheter exposure was associated with increased risk of P-trap positivity. P-trap heaters reduced risk of P-trap and sink drain positivity. WGS identified genomically linked environmental seeding in 6 of 99 room occupations by 40 KPCO-positive patients. In conclusion, KPCO-positive patients seed the environment in at least 6% of opportunities; once positive for KPCOs, wastewater sites are at greater risk of being positive subsequently. Increased nutrient exposure, e.g., due to tube food disposal down sinks, may increase risk; frequent flushing may be protective.

IMPORTANCEKlebsiella pneumoniae carbapenemase-producing organisms (KPCOs) are bacteria that are resistant to most antibiotics and thus are challenging to treat when they cause infections in patients. These organisms can be acquired by patients who are hospitalized for other reasons, complicating their hospital stay and even leading to death. Hospital wastewater sites, such as sink drains and toilets, have played a role in many reported outbreaks over the past decade. The significance of our research is in identifying risk factors for environmental positivity for KPCOs, which will facilitate further work to prevent transmission of these organisms to patients from the hospital environment.