Hospital water as the source of healthcare-associated infection and antimicrobial-resistant organisms

Drinking water plumbing systems are a hot spot for antimicrobial-resistant pathogens

BACKGROUND

Antimicrobial-resistant (AMR) pathogens in drinking water plumbing systems represent a significant yet underestimated public health threat.

METHODS

This is the first study to use qPCR and culture-based methods to investigate the prevalence of key AMR threats, meticillin resistant Staphylococcus aureus (MRSA) and carbapenem resistant Pseudomonas aeruginosa and Acinetobacter baumannii, in Australian hospital and residential drinking water and biofilm samples.

FINDINGS

Seventy-three per cent of residential water and biofilm samples were qPCR positive for at least one target pathogen compared with 38% of hospital samples, and 45% of residential plumbing fixtures harboured at least two target pathogens. Thirty-seven per cent of water and biofilm samples were qPCR positive for P. aeruginosa, 22.3% for A. baumannii and 21.7% for S. aureus. Using culture, 10% of samples were positive for P. aeruginosa, 8% for A. baumannii and 7% for S. aureus. Of these, 29% of P. aeruginosa and 28% of A. baumannii culture isolates were carbapenem resistant, and 54% of S. aureus isolates were identified as MRSA. Drain biofilms were the most common reservoir for AMR A. baumannii, S. aureus and P. aeruginosa. Carbapenem resistance genes including blaNDM-1, blaOXA-48, blaKPC-2 and blaVIM were found in biofilm samples otherwise negative for P. aeruginosa, indicating plumbing biofilms may act as eDNA reservoirs.

CONCLUSIONS

These findings underscore the critical role of plumbing biofilms as hotspots for diverse AMR pathogens, amplifying risks for vulnerable populations, particularly in home healthcare settings. This study highlights an urgent need for enhanced surveillance and targeted interventions to mitigate AMR risks in drinking water plumbing systems.

Assessing the role of environment in Pseudomonas aeruginosa healthcare-associated bloodstream infections: a one-year prospective survey

BACKGROUND

Deciphering precise sources and patterns of healthcare-associated Pseudomonas aeruginosa colonization/infection is crucial in defining strategies of prevention and control.

AIM

To prospectively investigate the role of hospital environment in P. aeruginosa nosocomial bloodstream infections (Pa-BSIs) during one year in a tertiary-care hospital.

METHODS

Clinical records of patients presenting Pa-BSIs after >48 h of hospitalization were investigated to confirm the nosocomial character of BSIs and identify the routes of entry and risk factors. Environmental investigations were performed to track P. aeruginosa source/reservoir along the care pathway. Clinical and environmental strains were compared by whole-genome sequencing to identify the route of contamination from hospital environment to patients.

FINDINGS

Fifty-three BSIs episodes in 49 patients were considered as nosocomial, mostly involving men (73%), with an average age of 62.4 years, immunosuppressed in >40% of cases, and after previous antibiotic therapy in almost 92% of cases. BSIs occurred after 27 days of hospitalization on average. The main routes of entry were urinary (30%, on indwelling catheters for two-thirds of cases) and cutaneous (17%, catheter-related in almost 80% of cases). P. aeruginosa was found in 16 out of 49 investigations, representing 34 positive samples, including 54% of sink traps, 23% of water, and 20% of tap aerators. An epidemiological link was established between environmental and clinical strains only for eight patients, representing 15% of nosocomial BSIs.

CONCLUSION

The hospital environment usually considered as the main source of P. aeruginosa healthcare-associated infections was identified as responsible for nosocomial BSIs in only 15% of patients. Since the implementation of water and hospital environment management, one may hypothesize that P. aeruginosa has become a community-acquired pathogen with a nosocomial expression in infection.

Detection of Mycobacterium chimaera in medical device water samples by customised real time PCR using a InGenius platform

Mycobacterium chimaera, belonging to the Mycobacterium avium complex, is an opportunistic environmental mycobacterium which has been isolated from medical device water samples such as Heater Cooler Units (HCU). Laboratories currently use culture-based diagnostic methods to detect M. chimaera, but these take a long time to obtain results. The aim of this study is to test and define the Limit of Detection (LoD) of a Real-Time Polymerase Chain Reaction test (RT-PCR) specific for M. chimaera, using a sample-to-result InGenius platform, performed on medical device water samples collected at the referral centre for the detection of mycobacteria from environmental specimens of Bologna, Italy. A total of 285 water samples were included in this study. The sensitivity and specificity of RT-PCR compared to culture were 60.5% and 98.8% respectively, with an overall agreement of 82.1% and a positive predictive value of 97.4%. The LoD calculated was approximately 2900 CFU/ml. In conclusion, this study confirmed that detection of M. chimaera with RT-PCR could support culture-based methods in reducing the time necessary to identify highly colonised HCUs, with high positive predictive values. Therefore, we suggest performing this customised RT-PCR on concentrated decontaminated water samples, shutting down and thoroughly disinfecting positive HCUs, to reduce the risk of patient infection.

Understanding Quorum-Sensing and Biofilm Forming in Anaerobic Bacterial Communities

Biofilms are complex, highly organized structures formed by microorganisms, with functional cell arrangements that allow for intricate communication. Severe clinical challenges occur when anaerobic bacterial species establish long-lasting infections, especially those involving biofilms. These infections can occur in device-related settings (e.g., implants) as well as in non-device-related conditions (e.g., inflammatory bowel disease). Within biofilms, bacterial cells communicate by producing and detecting extracellular signals, particularly through specific small signaling molecules known as autoinducers. These quorum-sensing signals are crucial in all steps of biofilm formation: initial adhesion, maturation, and dispersion, triggering gene expression that coordinates bacterial virulence factors, stimulates immune responses in host tissues, and contributes to antibiotic resistance development. Within anaerobic biofilms, bacteria communicate via quorum-sensing molecules such as N-Acyl homoserine lactones (AHLs), autoinducer-2 (AI-2), and antimicrobial molecules (autoinducing peptides, AIPs). To effectively combat pathogenic biofilms, understanding biofilm formation mechanisms and bacterial interactions is essential. The strategy to disrupt quorum sensing, termed quorum quenching, involves methods like inactivating or enzymatically degrading signaling molecules, competing with signaling molecules for binding sites, or noncompetitively binding to receptors, and blocking signal transduction pathways. In this review, we comprehensively analyzed the fundamental molecular mechanisms of quorum sensing in biofilms formed by anaerobic bacteria. We also highlight quorum quenching as a promising strategy to manage bacterial infections associated with anaerobic bacterial biofilms.

A multicentric survey and single-centre observational study of usage behaviour of sinks in intensive care: training is needed to minimize risk

INTRODUCTION

Sinks have been introduced near patients to improve hand hygiene as part of infection prevention and control measures. However, sinks are a known reservoir for gram-negative bacterial pathogens in particular and their removal to prevent bacterial infections in intensive care patients is currently recommended by several international guidelines.

METHODS

Healthcare workers (HCWs) in 15 intensive care units (ICUs) in Germany were given the opportunity to complete an anonymous survey on the use of sinks between August 2022 and January 2023. Observations were then made in three participating ICUs to determine the frequency and reason for contact with the sink.

RESULTS

258 questionnaires were returned (nurses 87%). 90% found it useful to very useful to have a sink in the patient room, and 56% reported using it daily for hand hygiene. We observed 33 contacts between nurses and sinks over 17 h. In 20/33 (60%) cases, the sink was used for waste disposal. In 3/33 (10%) it was used for hand washing.

DISCUSSION

Sinks are still used for daily care in intensive care units. Educational Interventions in existing buildings to minimise risk through "sink hygiene" (i.e. separation of sinks for water disposal and uptake) can make an important contribution to infection prevention.

Handwashing basins and healthcare associated infections: Bacterial diversity in biofilms on faucets and drains

BACKGROUND

Increasingly, hospital handwashing basins have been identified as a source of healthcare-associated infections. Biofilms formed on the faucet and drains of handbasins can potentially harbour pathogenic microbes and promote the dissemination of antimicrobial resistance. However, little is known about the diversity of these biofilm communities and the routes of contamination.

AIM

The aim of this paper was to use 16S rRNA gene amplicon sequencing to investigate the diversity of prokaryote communities present in faucet and drain biofilm samples taken from hospital and residential handbasins.

FINDINGS

The biofilm prokaryotes communities were diverse, with high abundances of potentially corrosive, biofilm forming and pathogenic genera, including those that are not typically waterborne. The β-diversity showed statistically significant differences in the variation of bacterial communities on the basis on building type (hospital vs residential p = 0.0415). However, there was no statistically significant clustering based on sampling site (faucet vs drain p = 0.46). When examining the β-diversity between individual factors, there was a significant difference between drain biofilms of different buildings (hospital drain vs residential drain p = 0.0338).

CONCLUSION

This study demonstrated that biofilms from hospital and residential handbasins contain complex and diverse microbial communities that differ significantly by building type. It also showed biofilms formed on the faucet and drain of a hospital's handbasins were not significantly different. Future research is needed to understand the potential mechanisms of transfer between drains and faucets of hospital handbasins. This information will inform improved infection control guidelines to control this underrecognized source of infections.

Risk factors for Pseudomonas aeruginosa VIM colonization or infection in the ICU: Case-control study

BACKGROUND

Carbapenem-resistant strains of Pseudomonas aeruginosa (CRPA) have become a major health care concern in many countries, against which anti-infective strategies are limited and which require adequate infection control interventions. Knowing the different modes of transmission of CRPA in intensive care units (ICUs) would be helpful to adapt the means of prevention.

METHODS

The aim of this retrospective case-control study was conducted between January 1, 2017 and February 28, 2022 to identify the risk factors for the acquisition of CRPA in ICUs.

RESULTS

During the study period, 147 patients were included (49 cases and 98 controls). Among the 49 patients, 31 (63%) acquired CRPA in clusters and 18 (37%) sporadically. A univariate analysis showed that 4 variables were associated with CRPA acquisition, including (1) prior antibiotic prescriptions, (2) admission to rooms 203 and 207, (3) severity of illness at admission, and (4) use of mechanical ventilation. Multivariate analysis identified 3 factors of CRPA acquisition, including admission to room 203 (odds ratio [OR] = 29.5 [3.52-247.09]), previous antibiotic therapy (OR = 3.44 [1.02-11.76]), and severity of condition at admission (OR = 1.02 [1-1.04]).

CONCLUSIONS

Our study suggests the role of a contaminated environment in the acquisition of CRPA in the ICU, along with antibiotic use.

Ecological and evolutionary mechanisms driving within-patient emergence of antimicrobial resistance

The ecological and evolutionary mechanisms of antimicrobial resistance (AMR) emergence within patients and how these vary across bacterial infections are poorly understood. Increasingly widespread use of pathogen genome sequencing in the clinic enables a deeper understanding of these processes. In this Review, we explore the clinical evidence to support four major mechanisms of within-patient AMR emergence in bacteria: spontaneous resistance mutations; in situ horizontal gene transfer of resistance genes; selection of pre-existing resistance; and immigration of resistant lineages. Within-patient AMR emergence occurs across a wide range of host niches and bacterial species, but the importance of each mechanism varies between bacterial species and infection sites within the body. We identify potential drivers of such differences and discuss how ecological and evolutionary analysis could be embedded within clinical trials of antimicrobials, which are powerful but underused tools for understanding why these mechanisms vary between pathogens, infections and individuals. Ultimately, improving understanding of how host niche, bacterial species and antibiotic mode of action combine to govern the ecological and evolutionary mechanism of AMR emergence in patients will enable more predictive and personalized diagnosis and antimicrobial therapies.

Occurrence of chlorine-resistant Pseudomonas aeruginosa in hospital water systems: threat of waterborne infections for patients

BACKGROUND

Several healthcare-associated infection outbreaks have been caused by waterborne Pseudomonas aeruginosa exhibiting its ability to colonize water systems and resist conventional chlorine treatment. This study aims to investigate the occurrence of Pseudomonas aeruginosa in hospital drinking water systems and the antimicrobial resistance profiles (antibiotic and chlorine resistance) of isolated strains.

METHODS

We investigated the presence of Pseudomonas aeruginosa in water and biofilms developed in nine hospital water systems (n = 192) using culture-based and molecular methods. We further assessed the survival of isolated strains after exposure to 0.5 and 1.5 ppm concentrations of chlorine. The profile of antibiotic resistance and presence of antibiotic resistance genes in isolated strains were also investigated.

RESULTS

Using direct PCR method, Pseudomonas aeruginosa was detected in 22% (21/96) of water and 28% (27/96) of biofilm samples. However, culturable Pseudomonas aeruginosa was isolated from 14 samples. Most of P. aeruginosa isolates (86%) were resistant to at least one antibiotic (mainly β-lactams), with 50% demonstrating multidrug resistance. Moreover, three isolates harbored intI1 gene and two isolates contained blaOXA-24,blaOXA-48, and blaOXA-58‌ genes. Experiments with chlorine disinfection revealed that all tested Pseudomonas aeruginosa strains were resistant to a 0.5 ppm concentration. However, when exposed to a 1.5 ppm concentration of chlorine for 30 min, 60% of the strains were eliminated. Interestingly, all chlorine-resistant bacteria that survived at 30-minute exposure to 1.5 ppm chlorine were found to harbor the intI1 gene.

CONCLUSIONS

The detection of antimicrobial resistant Pseudomonas aeruginosa in hospital water systems raises concerns about the potential for infections among hospitalized patients. The implementation of advanced mitigation measures and targeted disinfection methods should be considered to tackle the evolving challenges within hospital water systems.

Genomic portraits of methicillin-resistant staphylococci (MRS) from food fish unveiled the genes associated with staphylococcal food poisoning (SFP), virulence and antimicrobial resistance

BACKGROUND

Characteristics of non-clinical strains of methicillin-resistant Staphylococcus aureus (MRSA) especially from fishery environment are poorly understood. This research, in addition to comprehensive characterisation, sought to delineate the genetic relatedness between the MRSA strains originating from clinical as well as non-clinical settings. Out of 39 methicillin-resistant staphylococcal isolates from 197 fish samples, 6 (Three each of methicillin-resistant S. haemolyticus (MRSH) and MRSA) with distinct resistance profiles were selected for whole-genome sequencing. Using respective bioinformatics tools, MRSA genomes were comprehensively characterized for resistome, virulomes, molecular epidemiology and phylogenetic analysis. Simultaneously, MRSH genomes were specifically examined to characterize antimicrobial resistance genes (ARGs), owing to the fact that MRSH is often recognized as a reservoir for resistance determinants.

RESULTS

Three MRSA clones identified in this study include ST672-IVd/t13599 (sequence type-SCCmec type/spa type), ST88-V/t2526, and ST672-IVa/t1309. Though, the isolates were phenotypically vancomycin-sensitive, five of the six genomes carried vancomycin resistance genes including the VanT (VanG cluster) or VanY (VanM cluster). Among the three MRSA, only one harbored the gene encoding Panton-Valentine Leukocidin (PVL) toxin, while staphylococcal enterotoxin (SEs) genes such as sea and seb, associated with staphylococcal food poisoning were identified in two other MRSA. Genomes of MRSH carried a composite of type V staphylococcal cassette chromosome mec (SCCmec) elements (5C2 & 5). This finding may be explained by the inversion and recombination events that may facilitate the integration of type V elements to the SCC elements of S. aureus with a methicillin-susceptible phenotype. Phylogenetically, MRSA from a non-clinical setting displayed a considerable relatedness to that from clinical settings.

CONCLUSION

This study highlights the genetic diversity and resistance profiles of MRSA and MRSH, with non-clinical MRSA showing notable relatedness to clinical strains. Future research should explore resistance gene transfer mechanisms and environmental reservoirs to better manage MRSA spread.

Drinking Water Microbiota, Entero-Mammary Pathways, and Breast Cancer: Focus on Nontuberculous Mycobacteria

The prospect of drinking water serving as a conduit for gut bacteria, artificially selected by disinfection strategies and a lack of monitoring at the point of use, is concerning. Certain opportunistic pathogens, notably some nontuberculous mycobacteria (NTM), often exceed coliform bacteria levels in drinking water, posing safety risks. NTM and other microbiota resist chlorination and thrive in plumbing systems. When inhaled, opportunistic NTM can infect the lungs of immunocompromised or chronically ill patients and the elderly, primarily postmenopausal women. When ingested with drinking water, NTM often survive stomach acidity, reach the intestines, and migrate to other organs using immune cells as vehicles, potentially colonizing tumor tissue, including in breast cancer. The link between the microbiome and cancer is not new, yet the recognition of intratumoral microbiomes is a recent development. Breast cancer risk rises with age, and NTM infections have emerged as a concern among breast cancer patients. In addition to studies hinting at a potential association between chronic NTM infections and lung cancer, NTM have also been detected in breast tumors at levels higher than normal adjacent tissue. Evaluating the risks of continued ingestion of contaminated drinking water is paramount, especially given the ability of various bacteria to migrate from the gut to breast tissue via entero-mammary pathways. This underscores a pressing need to revise water safety monitoring guidelines and delve into hormonal factors, including addressing the disproportionate impact of NTM infections and breast cancer on women and examining the potential health risks posed by the cryptic and unchecked microbiota from drinking water.

Antibiotic resistance pattern of waterborne causative agents of healthcare-associated infections: A call for biofilm control in hospital water systems

BACKGROUND

In recent years, the global spread of antimicrobial resistance has become a concerning issue, often referred to as a "silent pandemic". Healthcare-associated infections (HAIs) caused by antibiotic-resistant bacteria (ARB) are a recurring problem, with some originating from waterborne route. The study aimed to investigate the presence of clinically relevant opportunistic bacteria and antibiotic resistance genes (ARGs) in hospital water distribution systems (WDSs).

METHODS

Water and biofilm samples (n = 192) were collected from nine hospitals in Isfahan and Kashan, located in central Iran, between May 2022 and June 2023. The samples were analyzed to determine the presence and quantities of opportunistic bacteria and ARGs using cultural and molecular methods.

RESULTS

Staphylococcus spp. were highly detected in WDS samples (90 isolates), with 33 % of them harboring mecA gene. However, the occurrences of E. coli (1 isolate), Acinetobacter baumannii (3 isolates), and Pseudomonas aeruginosa (14 isolates) were low. Moreover, several Gram-negative bacteria containing ARGs were identified in the samples, mainly belonging to Stenotrophomonas, Sphingomonas and Brevundimonas genera. Various ARGs, as well as intI1, were found in hospital WDSs (ranging from 14 % to 60 %), with higher occurrences in the biofilm samples.

CONCLUSION

Our results underscore the importance of biofilms in water taps as hotspots for the dissemination of opportunistic bacteria and ARG within hospital environments. The identification of multiple opportunistic bacteria and ARGs raises concerns about the potential exposure and acquisition of HAIs, emphasizing the need for proactive measures, particularly in controlling biofilms, to mitigate infection risks in healthcare settings.

Infection prevention and control and related practices in African neonatal units: The Pan-African neonatal care assessment study (PANCAS)

BACKGROUND

The burden of neonatal mortality is primarily borne by low- and middle-income countries (LMICs), including deaths due to healthcare-associated infections (HAIs). Few studies have assessed infection prevention and control (IP&C) practices in African units caring for small and/or sick newborns aimed to reduce HAIs.

METHODS

We performed a mixed-methods study composed of a survey and virtual tour to assess IP&C and related practices. We created a survey composed of multiple-choice and open-ended questions delivered to site respondents via Zoom or video equivalent. Respondents provided a virtual tour of their unit via video and the study team used a checklist to evaluate specific practices.

RESULTS

We recruited 45 units caring for small and sick newborns in 20 African countries. Opportunities to optimize hand hygiene, Water, Sanitation and Hygiene (WASH) practices, Kangaroo Mother Care, and IP&C training were noted. The virtual tour offered further understanding of IP&C challenges unique to individual sites. All respondents expressed the need for additional space, equipment, supplies, education, and IP&C staff and emphasized that attention to maternal comfort was important to IP&C success.

DISCUSSION

This study identified opportunities to improve IP&C practices using low-cost measures including further education and peer support through learning collaboratives. Virtual tours can be used to provide site-specific assessment and feedback from peers, IP&C specialists and environmental engineering experts.

Comparing the Effects of Two Culture Methods to Determine the Total Heterotrophic Bacterial Colony Count in Hospital Purified Water

BACKGROUND

Accurately detecting the quantity of microorganisms in hospital purified water is of significant importance for early identification of microbial contamination and reducing the occurrence of water-borne hospital infections. The choice of detection method is a prerequisite for ensuring accurate results. Traditional Plate Count Agar (PCA) belongs to a high-nutrient medium, and there may be limitations in terms of accuracy or sensitivity in detecting microorganisms in hospital purified water. On the other hand, Reasoner's 2A agar (R2A) has characteristics, such as low-nutrient levels, low cultivation temperature, and extended incubation time, providing advantages in promoting the growth of aquatic microorganisms. This study, through comparing the differences in total colony counts between two detection methods, aims to select the method more suitable for the growth of aquatic microorganisms, offering new practical insights for accurately detecting the total count of heterotrophic bacteria in hospital purified water.

METHODS

The most commonly used plate count agar (PCA) method, and the R2A agar culture were adopted to detect microorganisms and determine the total number of bacterial colonies in the water for oral diagnosis and treatment water and terminal rinse water for endoscopes in medical institutions. The two water samples were inoculated by pour plate and membrane filtration methods, respectively. Using statistical methods including Spearman and Pearson correlation, Wilcoxon signed-rank sum test, paired-Chi-square test, and linear regression, we analyze the differences and associations in the bacterial counts cultivated through two different methods.

RESULTS

In 142 specimens of the water, the median and interquartile range of the heterotrophic bacterial colony number under the R2A culture method and under the PCA culture method were 200 (Q1-Q3: 25-18,000) and 6 (Q1-Q3: 0-3700). The total number of heterotrophic bacteria colonies cultured in R2A medium for 7 days was more than that cultured in PCA medium for 2 days (P < 0.05). The linear regression results showed a relatively strong linear correlation between the number of colonies cultured by the R2A method and that cultured by the PCA method (R2 = 0.7264). The number of bacterial species detected on R2A agar medium is greater than that on PCA agar medium.

CONCLUSION

The R2A culture method can better reflect the actual number of heterotrophic bacterial colonies in hospital purified water. After logarithmic transformation, the number of colonies cultured by the two methods showed a linear correlation.

Sink interventions in the ICU to reduce risk of infection or colonization with Gram-negative pathogens: a systematic review of the literature

BACKGROUND

Healthcare-associated infections (HAIs) are a major problem in intensive care units (ICUs). The hospital water environment is a potential reservoir for Gram-negative bacteria (GNB), and it has been shown that contaminated sinks contribute to the spread of GNB in outbreak and non-outbreak settings. This study aimed to investigate which sink interventions may reduce GNB infection and colonization rates in the ICU.

METHODS

A database search (MEDLINE via PubMed, EMBASE via Ovid and ClinicalTrials.gov) was undertaken without restrictions on language or date of publication. Studies of any design were included if they described an intervention on the water fixtures in patient rooms, and presented data about HAI or colonization rates in non-outbreak settings. Acquisition (infection and/or colonization) rates of GNB and Pseudomonas aeruginosa were analysed as outcomes.

RESULTS

In total, 4404 records were identified. Eleven articles were included in the final analysis. No randomized controlled trials were included in the analysis, and all studies were reported to have moderate to serious risk of bias. Removing sinks and applying filters on taps had a significant impact on GNB acquisition, but there was high heterogeneity among reported outcomes and sample size among the studies.

CONCLUSION

Few studies have investigated the association of sinks in patient rooms with healthcare-associated acquisition of GNB in non-outbreak settings. Heterogeneity in study design made it impossible to generalize the results. Prospective trials are needed to further investigate whether removing sinks from patient rooms can reduce the endemic rate of HAIs in the ICU.

Interphylum dissemination of NDM-5-positive plasmids in hospital wastewater from Fuzhou, China: a single-centre, culture-independent, plasmid transmission study

BACKGROUND

The global spread of plasmid-borne carbapenem resistance is an ongoing public health challenge; however, the nature of such horizontal gene transfer events among complex bacterial communities remains poorly understood. We examined the in-situ transfer of the globally dominant New Delhi metallo-β-lactamase (NDM)-5-positive IncX3 plasmid (denoted pX3_NDM-5) in hospital wastewater to simulate a real-world, One Health antimicrobial resistance context.

METHODS

For this transmission study, we tagged pX3_NDM-5 with the green fluorescent protein gene, gfp, using a CRISPR-based method and transferred the plasmid to a donor Escherichia coli strain. Bacteria were extracted from a hospital wastewater treatment plant (Fujian Provincial Maternity and Children's Hospital, Fuzhou, China) as the bacterial recipient community. We mixed this recipient community with the E coli donor strain carrying the gfp-tagged plasmid, both with and without sodium hypochlorite (NaClO) as an environmental stressor, and conducted several culture-based and culture-independent conjugation assays. The conjugation events were observed microscopically and quantified by fluorescence-activated cell sorting. We analysed the taxonomic composition of the sorted transconjugal pool by 16S rRNA gene amplicon sequencing and assessed the stability of the plasmid in the isolated transconjugants and its ability to transfer back to E coli.

FINDINGS

We show that the plasmid pX3_NDM-5 has a broad host range and can transfer across various bacterial phyla, including between Gram-negative and Gram-positive bacteria. Although environmental stress with NaClO did not affect the overall plasmid transfer frequency, it reduced the breadth of the transconjugant pool. The taxonomic composition of the transconjugal pool was distinct from that of the recipient communities, and environmental stress modulated the permissiveness of some operational taxonomic units towards the acquisition of pX3_NDM-5. Notably, pX3_NDM-5 transconjugants included the Gram-positive pathogen Enterococcus faecalis, and the plasmid could subsequently be reconjugated back to E coli. These findings suggest that E faecalis could act as a natural shuttle vector for the wide dissemination of pX3_NDM-5 plasmids.

INTERPRETATION

Our culture-independent conjugation model simulates natural environmental conditions and challenges the established theory that Gram-negative and Gram-positive bacteria rarely exchange clinically important plasmids. The data show that plasmids disseminate more widely across genera and phyla than previously thought. These findings have substantial implications when considering the spread of antimicrobial resistance across One Health sectors.

FUNDING

The Laboratory of Lingnan Modern Agriculture Project, the National Natural Science Foundation of China, the Natural Science Foundation of Fujian Province of China, and the Outstanding Young Research Talents Program of Fujian Agriculture and Forestry University.

Misidentification as Pseudomonas aeruginosa in hospital water supply samples

Drinking water in hospitals is often tested for Pseudomonas aeruginosa because of its virulence potential. This article describes a case where, based on EN ISO 16266, seven of 11 (64%) samples taken simultaneously from the drinking water system at a single hospital tested positive for P. aeruginosa. This resulted in extensive investigations and interventions, and a number of measures were implemented. However, supplementary analyses with more discriminatory power (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, 16S-rRNA sequencing) ruled out P. aeruginosa completely. The authors wish to raise awareness of this problem, and suggest that diagnostic uncertainty of results obtained by EN ISO 16266 should be indicated on laboratory reports. Wrongly assuming the presence of P. aeruginosa in hospital water supply systems can lead to unnecessary control measures, as analytical uncertainty massively influences the health risk assessment and the remediation measures initiated in medical environments.

Clinical Issues - February 2023

Frequency of OR wall and ceiling cleaning Key words: environmental surfaces, high-touch surfaces, contamination, cleaning frequency, hand contact. Waterborne pathogen development and associated risks Key words: Legionella, premise plumbing system, opportunistic pathogens, biofilm, electronic sensor faucet. Water management program teams and perioperative services Key words: water supply safety, facility water system, waterborne pathogen prevention plan, faucets, drains. Minimizing waterborne pathogens in perioperative areas Key words: waterborne pathogen dispersal, cross contamination, splash guards, high-risk hardware, sinks.

Formic acid, an organic acid food preservative, induces viable-but-non-culturable state, and triggers new Antimicrobial Resistance traits in Acinetobacter baumannii and Klebsiella pneumoniae

Numerous human pathogens, especially Gram-negative bacteria, are able to enter the viable-but-non-culturable (VBNC) state when they are exposed to environmental stressors and pose the risk of being resuscitated and causing infection after the removal of the trigger. Widely used food preservatives like weak organic acids are potential VBNC inducers in food processing and packaging facilities but have only been reported for food-borne pathogens. In the present study, it is demonstrated for the first time that one such agent, formic acid (FA), can induce a VBNC state at food processing, storage, and distribution temperatures (4, 25, and 37°C) with a varied time of treatment (days 4-10) in pathogenic Gram-negative bacteria Acinetobacter baumannii and Klebsiella pneumoniae. The use of hospital-associated pathogens is critical based on the earlier reports that demonstrated the presence of these bacteria in hospital kitchens and commonly consumed foods. VBNC induction was validated by multiple parameters, e.g., non-culturability, metabolic activity as energy production, respiratory markers, and membrane integrity. Furthermore, it was demonstrated that the removal of FA was able to resuscitate VBNC with an increased expression of multiple virulence and Antimicrobial Resistance (AMR) genes in both pathogens. Since food additives/preservatives are significantly used in most food manufacturing facilities supplying to hospitals, contamination of these packaged foods with pathogenic bacteria and the consequence of exposure to food additives emerge as pertinent issues for infection control, and control of antimicrobial resistance in the hospital setting.