Spatio-temporal analysis of infra-specific genetic variations among a Pseudomonas aeruginosa water network hospital population: invasion and selection of clonal complexes

Cross-contamination of carbapenem-resistant Gram-negative bacteria between patients and the hospital environment in the first year of a newly built surgical ward

BACKGROUND

Transmission and outbreaks of carbapenem-resistant Gram-negative bacteria (CRGN) in hospitals are often associated with contamination of the wastewater environment. We performed a prospective observational study to investigate the colonization of the hospital wastewater environment during the first year of occupancy of the surgical intermediate and intensive care units of a newly constructed building at the University Hospital of Heidelberg, Germany.

METHODS

We performed monthly screening of the wastewater system (toilets and sinks) for 12 months, starting 1 month before opening (1st October 2020 to 30th October 2021). Admission and weekly rectal screening of patients for CRGN were also performed in parallel. Bacterial isolates were characterized by whole-genome sequencing.

RESULTS

Twenty-seven of 1978 (1.4%) admitted patients were colonized/infected with CRGN. A total of 29 CRGN isolates from 24 patients and 52 isolates were available for sequencing. Within the first month of occupancy, we identified seven patients colonized/infected with CRGN, while none were found in the environmental reservoirs. The first detection of CRGN isolates in the sewage system started five months after the first occupancy. Two previously non-colonized patients were colonized/infected with Pseudomonas aeruginosa strains colonizing the sewage system. The significant identity of plasmids carrying the carbapenemase gene suggests that long-term colonization of the sewage system facilitates the emergence of new carbapenem-resistant clones.

CONCLUSION

Cross-contamination between patients and the hospital environment is bidirectional. Our study demonstrated that contamination of the hospital wastewater environment may lead to persistent colonization and may serve as a reservoir for nosocomial acquisition of CRGN.

Premise Plumbing Pipe Materials and In-Building Disinfectants Shape the Potential for Proliferation of Pathogens and Antibiotic Resistance Genes

In-building disinfectants are commonly applied to control the growth of pathogens in plumbing, particularly in facilities such as hospitals that house vulnerable populations. However, their application has not been well optimized, especially with respect to interactive effects with pipe materials and potential unintended effects, such as enrichment of antibiotic resistance genes (ARGs) across the microbial community. Here, we used triplicate convectively mixed pipe reactors consisting of three pipe materials (PVC, copper, and iron) for replicated simulation of the distal reaches of premise plumbing and evaluated the effects of incrementally increased doses of chlorine, chloramine, chlorine dioxide, and copper-silver disinfectants. We used shotgun metagenomic sequencing to characterize the resulting succession of the corresponding microbiomes over the course of 37 weeks. We found that both disinfectants and pipe material affected ARG and microbial community taxonomic composition both independently and interactively. Water quality and total bacterial numbers were not found to be predictive of pathogenic species markers. One result of particular concern was the tendency of disinfectants, especially monochloramine, to enrich ARGs. Metagenome assembly indicated that many ARGs were enriched specifically among the pathogenic species. Functional gene analysis was indicative of a response of the microbes to oxidative stress, which is known to co/cross-select for antibiotic resistance. These findings emphasize the need for a holistic evaluation of pathogen control strategies for plumbing.

Bacteria isolated from equine uteri in The United Arab Emirates: A retrospective study

The United Arab Emirates (UAE) presents a unique environment in which to breed horses with a non-physiological breeding season coupled with high temperatures and humidity for much of the year. This study aimed to describe bacterial isolates from the uteri of mares in the UAE and compare them to those reported elsewhere in the world. Bacterial antibiotic resistance was also analysed to give a starting point for future monitoring. A total of 2022 swabs taken over 5 breeding seasons from the endometrium (n = 1350) or from uterine lavages (n = 672) were submitted for microbiological culture and antibiotic sensitivity testing. At 48h post inoculation 616/2022 (30.5%) of cultures showed microbial growth from which 690 isolates were identified. Most positive plates (548/616; 89%) grew one isolate; 68 cultures had two (62/616; 10.1%) or three (6/616; 1%) isolates. The most frequently isolated bacteria were β-haemolytic Streptococcus (36.5%; 252/690), E. coli (10.6%; 73/690), P. aeruginosa (10.1%; 70/690), K. pneumoniae (8.8%; 61/690) and Aeromonas hydrophila (4.1%; 28/690). The lowest level of antibiotic susceptibility for all isolates was shown by trimethoprim-sulphonamide (36.4%; 198/544), with amikacin showing the highest (76.1%; 271/356). A significant decrease in susceptibility to doxycycline, enrofloxacin and erythromycin, but a significant increase for amoxicillin with clavulanic acid, was seen for β-haemolytic Streptococcus. Decreasing susceptibility of trimethoprim-sulphonamide between two time periods was seen for E. coli. Compared to other studies UAE-based mares had a high incidence of P. aeruginosa and K. pneumoniae isolates, whereas E. coli was represented far less frequently as an isolate.

Antibiotic-resistant organisms establish reservoirs in new hospital built environments and are related to patient blood infection isolates

Background

Healthcare-associated infections due to antibiotic-resistant organisms pose an acute and rising threat to critically ill and immunocompromised patients. To evaluate reservoirs of antibiotic-resistant organisms as a source of transmission to patients, we interrogated isolates from environmental surfaces, patient feces, and patient blood infections from an established and a newly built intensive care unit.

Methods

We used selective culture to recover 829 antibiotic-resistant organisms from 1594 environmental and 72 patient fecal samples, in addition to 81 isolates from blood cultures. We conducted antibiotic susceptibility testing and short- and long-read whole genome sequencing on recovered isolates.

Results

Antibiotic-resistant organism burden is highest in sink drains compared to other surfaces. Pseudomonas aeruginosa is the most frequently cultured organism from surfaces in both intensive care units. From whole genome sequencing, different lineages of P. aeruginosa dominate in each unit; one P. aeruginosa lineage of ST1894 is found in multiple sink drains in the new intensive care unit and 3.7% of blood isolates analyzed, suggesting movement of this clone between the environment and patients.

Conclusions

These results highlight antibiotic-resistant organism reservoirs in hospital built environments as an important target for infection prevention in hospitalized patients.

Detection and distribution of vbnc/viable pathogenic bacteria in full-scale drinking water treatment plants

Viable but non-culturable (VBNC) bacteria have attracted widespread attention since they are inherently undetected by traditional culture-dependent methods. Importantly, VBNC bacteria could resuscitate under favorable conditions leading to significant public health concerns. Although the total number of viable bacteria has been theorized to be far greater than those that can be cultured, there have been no reports quantifying VBNC pathogenic bacteria in full-scale drinking water treatment plants (DWTPs). In this work, we used both culture-dependent and quantitative PCR combination with propidium monoazide (PMA) dye approaches to characterize cellular viability. Further, we established a method to quantify viable pathogens by relating specific gene copies to viable cell numbers. Ratios of culturable bacteria to viable 16S rRNA gene copies in water and biological activated carbon (BAC) biofilms were 0-4.75% and 0.04-56.24%, respectively. The VBNC E. coli, E. faecalis, P. aeruginosa, Salmonella sp., and Shigella sp. were detected at levels of 0-10³ cells/100 mL in source water, 0-10² cells/100 mL in chlorinated water, and 0-10³ cells/g in BAC biofilms. In addition, differences between the total and viable community structures after ozonation and chlorination were investigated. The relative abundance of opportunistic pathogens such as Mycobacterium, Sphingomonas, etc. increased in final water, likely due to their chlorine resistance. In summary, we detected significant quantities of viable/VBNC opportunistic pathogens in full-scale DWTPs, confirming that traditional, culture-dependent methods are inadequate for detecting VBNC bacteria. These findings suggest a need to develop and implement rapid, accurate methods for the detection of VBNC pathogenic bacteria in DWTPs to ensure the safety of drinking water.

Metabotypes of Pseudomonas aeruginosa Correlate with Antibiotic Resistance, Virulence and Clinical Outcome in Cystic Fibrosis Chronic Infections

Pseudomonas aeruginosa (P.a) is one of the most critical antibiotic resistant bacteria in the world and is the most prevalent pathogen in cystic fibrosis (CF), causing chronic lung infections that are considered one of the major causes of mortality in CF patients. Although several studies have contributed to understanding P.a within-host adaptive evolution at a genomic level, it is still difficult to establish direct relationships between the observed mutations, expression of clinically relevant phenotypes, and clinical outcomes. Here, we performed a comparative untargeted LC/HRMS-based metabolomics analysis of sequential isolates from chronically infected CF patients to obtain a functional view of P.a adaptation. Metabolic profiles were integrated with expression of bacterial phenotypes and clinical measurements following multiscale analysis methods. Our results highlighted significant associations between P.a “metabotypes”, expression of antibiotic resistance and virulence phenotypes, and frequency of clinical exacerbations, thus identifying promising biomarkers and therapeutic targets for difficult-to-treat P.a infections

Impact of intensive care unit relocation and role of tap water on an outbreak of Pseudomonas aeruginosa expressing OprD-mediated resistance to imipenem

BACKGROUND

To assess the impact of the incidental relocation of an intensive care unit (ICU) on the risk of colonizations/infections with Pseudomonas aeruginosa exhibiting OprD-mediated resistance to imipenem (PA-OprD).

AIM

The primary aim was to compare the proportion of PA-OprD among P. aeruginosa samples before and after an incidental relocation of the ICU. The role of tap water as a route of contamination for colonization/infection of patients with PA-OprD was assessed as a secondary aim.

METHODS

A single-centre, observational, before/after comparison study was conducted from October 2013 to October 2015. The ICU was relocated at the end of October 2014. All P. aeruginosa-positive samples isolated from patients hospitalized ≥48 h in the ICU were included. Tap water specimens were collected every three months in the ICU. PA-OprD strains isolated from patients and tap water were genotyped using pulse-field gel electrophoresis.

FINDINGS

A total of 139 clinical specimens of P. aeruginosa and 19 tap water samples were analysed. The proportion of PA-OprD strains decreased significantly from 31% to 7.7% after the relocation of the ICU (P = 0.004). All PA-OprD clinical specimens had a distinct genotype. Surprisingly, tap water was colonized with a single PA-OprD strain during both periods, but this single clone has never been isolated from clinical specimens.

CONCLUSION

Relocation of the ICU was associated with a marked decrease in P. aeruginosa strains resistant to imipenem. The polyclonal character of PA-OprD strains isolated from patients and the absence of tap-water-to-patient contamination highlight the complexity of the environmental impact on the endogenous colonization/infection with P. aeruginosa.

Molecular identification and phylogenetic analysis of Bothrops insularis bacterial and fungal microbiota

Bothrops insularis, known as the golden lancehead snake, has its natural habitat restricted to Queimada Grande Island on the southern coast of Brazil. This culture-dependent study aimed to identify microorganisms obtained from the mouth, eyes, and cloaca of this species. Swabs from 20 snakes were collected for fungal and bacterial isolation. DNA was extracted from all samples, and identification was performed by amplifying the ITS1-5.8S-ITS2 regions and the 16S rDNA gene, respectively. All strains were identified and deposited in the GenBank nucleotide database. MEGA v6.0 software was utilized to construct phylogenetic trees. In total, 100 strains were isolated and characterized, from which 42 fungi were distributed into 23 species and 58 bacteria into 13 species. The genus Fusarium was predominant since 11 strains and probably a new species was isolated from this fungus. Pseudomonas aeruginosa and Enterococcus faecalis were the predominant groups of aerobic bacteria isolated. Phylogenetic analyses between bacterial and fungal sequences suggest a similarity between the microorganisms found on the island and on the continent. These findings may be attributed to anthropic actions resulting from both expeditions to the island and actions of migratory birds, which are the main sources of food for snakes.

Hospital Drains as Reservoirs of Pseudomonas aeruginosa: Multiple-Locus Variable-Number of Tandem Repeats Analysis Genotypes Recovered from Faucets, Sink Surfaces and Patients

Identifying environmental sources of Pseudomonas aeruginosa (Pa) related to hospital-acquired infections represents a key challenge for public health. Biofilms in water systems offer protection and favorable growth conditions, and are prime reservoirs of microorganisms. A comparative genotyping survey assessing the relationship between Pa strains recovered in hospital sink biofilm and isolated in clinical specimens was conducted. Environmental strains from drain, faucet and sink-surface biofilm were recovered by a culture method after an incubation time ranging from 48 to 240 h. The genotyping of 38 environmental and 32 clinical isolates was performed using a multiple-locus variable-number of tandem repeats analysis (MLVA). More than one-third of Pa isolates were only cultivable following ≥48 h of incubation, and were predominantly from faucet and sink-surface biofilms. In total, 41/70 strains were grouped within eight genotypes (A to H). Genotype B grouped a clinical and an environmental strain isolated in the same ward, 5 months apart, suggesting this genotype could thrive in both contexts. Genotype E grouped environmental isolates that were highly prevalent throughout the hospital and that required a longer incubation time. The results from the multi-hospital follow-up study support the drain as an important reservoir of Pa dissemination to faucets, sink surfaces and patients. Optimizing the recovery of environmental strains will strengthen epidemiological investigations, facilitate pathway identification, and assist in identifying and controlling the reservoirs potentially associated to hospital-acquired infections.

Methodological approaches for monitoring opportunistic pathogens in premise plumbing: A review

Opportunistic premise (i.e., building) plumbing pathogens (OPPPs, e.g., Legionella pneumophila, Mycobacterium avium complex, Pseudomonas aeruginosa, Acanthamoeba, and Naegleria fowleri) are a significant and growing source of disease. Because OPPPs establish and grow as part of the native drinking water microbiota, they do not correspond to fecal indicators, presenting a major challenge to standard drinking water monitoring practices. Further, different OPPPs present distinct requirements for sampling, preservation, and analysis, creating an impediment to their parallel detection. The aim of this critical review is to evaluate the state of the science of monitoring OPPPs and identify a path forward for their parallel detection and quantification in a manner commensurate with the need for reliable data that is informative to risk assessment and mitigation. Water and biofilm sampling procedures, as well as factors influencing sample representativeness and detection sensitivity, are critically evaluated with respect to the five representative bacterial and amoebal OPPPs noted above. Available culturing and molecular approaches are discussed in terms of their advantages, limitations, and applicability. Knowledge gaps and research needs towards standardized approaches are identified.

Pseudomonas aeruginosa in premise plumbing of large buildings

Pseudomonas aeruginosa is an opportunistic bacterial pathogen that is widely occurring in the environment and is recognized for its capacity to form or join biofilms. The present review consolidates current knowledge on P. aeruginosa ecology and its implication in healthcare facilities premise plumbing. The adaptability of P. aeruginosa and its capacity to integrate the biofilm from the faucet and the drain highlight the role premise plumbing devices can play in promoting growth and persistence. A meta‐analysis of P. aeruginosa prevalence in faucets (manual and electronic) and drains reveals the large variation in device positivity reported and suggest the high variability in the sampling approach and context as the main reason for this variation. The effects of the operating conditions that prevail within water distribution systems (disinfection, temperature, and hydraulic regime) on the persistence of P. aeruginosa are summarized. As a result from the review, recommendations for proactive control measures of water contamination by P. aeruginosa are presented. A better understanding of the ecology of P. aeruginosa and key influencing factors in premise plumbing are essential to identify culprit areas and implement effective control measures.

Impact of new water systems on healthcare-associated colonization or infection with Pseudomonas aeruginosa

AIM

We aimed to study the impact of new water systems, which were less contaminated with P. aeruginosa, on the incidence of healthcare-associated P. aeruginosa cases (colonizations or infections) in care units that moved to a different building between 2005 and 2014.

METHODS

Generalized Estimated Equations were used to compare the incidence of P. aeruginosa healthcare-associated cases according to the building.

RESULTS

Twenty-nine units moved during the study period and 2,759 cases occurred in these units. No difference was observed when the new building was compared with older buildings overall.

CONCLUSION

Our results did not support our hypothesis of a positive association between water system contamination and the incidence of healthcare-associated P. aeruginosa cases. These results must be confirmed by linking results of water samples and patients' data.

Low occurrence of Pseudomonas aeruginosa in agricultural soils with and without organic amendment

The occurrence of Pseudomonas aeruginosa was monitored at a broad spatial scale in French agricultural soils, from various soil types and under various land uses to evaluate the ability of soil to be a natural habitat for that species. To appreciate the impact of agricultural practices on the potential dispersion of P. aeruginosa, we further investigated the impact of organic amendment at experimental sites in France and Burkina Faso. A real-time quantitative PCR (qPCR) approach was used to analyze a set of 380 samples selected within the French RMQS (“Réseau de Mesures de la Qualité des Sols”) soil library. In parallel, a culture-dependent approach was tested on a subset of samples. The results showed that P. aeruginosa was very rarely detected suggesting a sporadic presence of this bacterium in soils from France and Burkina Faso, whatever the structural and physico-chemical characteristics or climate. When we analyzed the impact of organic amendment on the prevalence of P. aeruginosa, we found that even if it was detectable in various manures (at levels from 10³ to 10⁵ CFU or DNA targets (g drywt)⁻¹ of sample), it was hardly ever detected in the corresponding soils, which raises questions about its survival. The only case reports were from a vineyard soil amended with a compost of mushroom manure in Burgundy, and a few samples from two fields amended with raw urban wastes in the sub-urban area of Ouagadougou, Burkina Faso. In these soils the levels of culturable cells were below 10 CFU (g drywt)⁻¹.

Association between healthcare water systems and Pseudomonas aeruginosa infections: a rapid systematic review

BACKGROUND

Pseudomonas aeruginosa is an opportunistic pathogen with a particular propensity to cause disease in the immunocompromised. Water systems have been reported to contribute to P. aeruginosa transmission in healthcare settings.

AIM

To systematically assess the evidence that healthcare water systems are associated with P. aeruginosa infection; to review aspects of design that can increase their potential to act as a reservoir; and to compare the efficacy of strategies for eradicating contamination and preventing infection.

METHODS

A rapid review methodology with a three-step search strategy was used to identify published studies. Scientific advisors were used to identify unpublished studies.

FINDINGS

Twenty-five relevant studies were included. There was plausible evidence of transmission of P. aeruginosa from water systems to patients and vice versa, although no direct evidence to explain the exact mode of transfer. Two studies provided plausible evidence for effective interventions: point-of-use filters and increasing chlorine disinfection. Non-touch taps and aspects of water system design were identified as probable risk factors for P. aeruginosa biofilm formation and subsequent transmission to patients. Poor hand hygiene or compliance with contact precautions were identified as potential contributory factors; plausible evidence to confirm this was not available.

CONCLUSIONS

Water systems can act as a source of P. aeruginosa infection in healthcare settings, although the route of transmission is unclear. Contamination appears to be confined to the distal ends of a water system and can persist for prolonged periods. Further studies are required to establish effective methods of preventing transmission and eradicating P. aeruginosa from plumbing systems.

Lagooning of wastewaters favors dissemination of clinically relevant Pseudomonas aeruginosa

The significance of wastewater treatment lagoons (WWTLs) as point sources of clinically relevant Pseudomonas aeruginosa that can disseminate through rural and peri-urban catchments was investigated. A panel of P. aeruginosa strains collected over three years from WWTLs and community-acquired infections was compared by pulsed field gel electrophoresis (PFGE) DNA fingerprinting and multilocus sequence typing (MLST). Forty-four distantly related PFGE profiles and four clonal complexes were found among the WWTL strains analyzed. Some genotypes were repeatedly detected from different parts of WWTLs, including the influent, suggesting an ability to migrate and persist over time. MLST showed all investigated lineages to match sequence types described in other countries and strains from major clinical clones such as PA14 of ST253 and "C" of ST17 were observed. Some of these genotypes matched isolates from community-acquired infections recorded in the WWTL geographic area. Most WWTL strains harbored the main P. aeruginosa virulence genes; 13% harbored exoU-encoded cytoxins, but on at least six different genomic islands, with some of these showing signs of genomic instability. P. aeruginosa appeared to be highly successful opportunistic colonizers of WWTLs. Lagooning of wastewaters was found to favor dissemination of clinically relevant P. aeruginosa among peri-urban watersheds.

Reliability of Pseudomonas aeruginosa semi-automated rep-PCR genotyping in various epidemiological situations

The purpose of this study was to evaluate the possibility of using a semi-automated repetitive DNA sequences-based polymerase chain reaction (rep-PCR) for typing Pseudomonas aeruginosa isolates. rep-PCR profiles obtained by the DiversiLab system of 84 P. aeruginosa isolates from distinct epidemiological situations were obtained. rep-PCR groupings were in good agreement with the origin of these isolates. Linked rep-PCR profiles were observed for isolates recovered from a same family of cystic fibrosis (CF) patients, for the etiological agents of clustered cases of nosocomial infections, and for some isolates recovered from a same hospital room. rep-PCR and pulsed-field gel electrophoresis SpeI restricted genomic DNA (PFGE-SpeI) profiles were compared. In a few instances, rep-PCR revealed genetic divergences among isolates of a same group of PFGE-SpeI profiles. These divergences could reflect genetic drifts among closely related isolates, as illustrated by those observed between clinical and environmental isolates of a same group of PFGE-SpeI profiles. The interpretation of such differences will require further studies, but the rep-PCR analysis of P. aeruginosa diversity appeared to be an appropriate method to investigate infra-specific genetic relatedness.