Waterborne Pseudomonas aeruginosa transmission in a hematology unit?

Investigation of an outbreak of metallo-β-lactamase producing Pseudomonas aeruginosa linked to the water distribution system in a Hematopoietic Stem Cell Transplantation Unit

Introduction

Pseudomonas aeruginosa (PA) is an opportunistic pathogen. Metallo-β-lactamase producing PA (MBL-PA) poses a problematic issue given limited available treatments. In Argentina, it accounts for less than one percent of healthcare-associated infections.

Objectives

To describe an outbreak of verona integron-encoded metallo-β-lactamase (VIM) Pseudomonas aeruginosa in a Hematopoietic Stem Cell Transplantation Unit (HSCTU), and the strategies implemented to control it.

Materials and methods

Investigation of an outbreak by MBL-PA in an HSCTU in May 2023. Active case search, environmental sampling, identification and susceptibility pattern of strains, mitigation strategies. Case: patient admitted to the HSCTU with positive sample for MBL-PA after 48 hours of admission. Mitigation strategies: biweekly rectal swabbing, contact precautions, dedicated nursing staff, waterless patient care, and disinfection of bacterial reservoirs.

Results

In May 2023 two cases were identified. A retrospective search determined an additional case. One (10%) of the environmental samples was positive for VIM type MBL-PA in the drain of the hand hygiene station in the nurse's office. Strains were susceptible to colistin and fosfomycin and intermediate to aztreonam. Incidence density (ID) of colonization and infection by MBL-PA in the HSCTU were .68/1,000 patient-days (pd) and 0, respectively, in the second semester of 2022. In the first semester of 2023, ID rose to 2.93/1,000 pd for colonization and .73/1,000 pd for infection.Mitigation strategies aimed at reducing exposure of immunocompromised hosts to water. No new cases have been identified since.

Conclusions

We report an MBL-PA outbreak probably linked to the water distribution system in an HSCTU, and mitigation strategies put in place.

Waterborne infections in haemato-oncology units - a narrative review

Bone marrow transplant and haemato-oncology patients are at risk of healthcare associated infections due to waterborne pathogens. We undertook a narrative review of waterborne outbreaks in haemato-oncology patients from 2000-2022. Databases searched included Pubmed, DARE and CDSR and were undertaken by two authors. We analysed the organisms implicated, sources identified and infection prevention and control strategies implemented. The most commonly implicated pathogens were Pseudomonas aeruginosa, non-tuberculous mycobacteria and Legionella pneumophila. Bloodstream infection was the most common clinical presentation. The majority of incidents employed multimodal strategies to achieve control, addressing both the water source and routes of transmission. This review highlights the risk to haemato-oncology patients from waterborne pathogens and discusses future preventative strategies and the requirement for new UK guidance for haemato-oncology units.

Development and Application of a Core Genome Multilocus Sequence Typing Scheme for the Health Care-Associated Pathogen Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic human pathogen that frequently causes health care-associated infections (HAIs). Due to its metabolic diversity and ability to form biofilms, this Gram-negative nonfermenting bacterium can persist in the health care environment, which can lead to prolonged HAI outbreaks. We describe the creation of a core genome multilocus sequence typing (cgMLST) scheme to provide a stable platform for the rapid comparison of P. aeruginosa isolates using whole-genome sequencing (WGS) data. We used a diverse set of 58 complete P. aeruginosa genomes to curate a set of 4,440 core genes found in each isolate, representing ∼64% of the average genome size. We then expanded the alleles for each gene using 1,991 contig-level genome sequences. The scheme was used to analyze genomes from four historical HAI outbreaks to compare the phylogenies generated using cgMLST to those of other means (traditional MLST, pulsed-field gel electrophoresis [PFGE], and single-nucleotide variant [SNV] analysis). The cgMLST scheme provides sufficient resolution for analyzing individual outbreaks, as well as the stability for comparisons across a variety of isolates encountered in surveillance studies, making it a valuable tool for the rapid analysis of P. aeruginosa genomes.

The Antibacterial Activity and Mechanism of Chlorogenic Acid Against Foodborne Pathogen Pseudomonas aeruginosa

Chlorogenic acid (CA), an ester of caffeic acid, is a major phenolic compound in herbs. The antimicrobial activity of CA against Pseudomonas aeruginosa P1, a foodborne pathogen, was investigated in this study. To understand how CA injured target cells, the influence of CA on cell morphology was assessed. A sunken cell surface and detachment of outer membrane components in P. aeruginosa P1 were observed after being treated by CA. Following this, the intracellular membrane permeability and the content of lipopolysaccharide (LPS), a main component of outer membrane, were determined. The release of intracellular protein and ATP from P. aeruginosa P1 indicated that CA increased intracellular membrane permeability and resulted in the leakage of intracellular materials. The uptake of propidium iodide, a compromised cell membrane nucleic acid stain, further demonstrated that CA acted on the intracellular membrane. CA resulted in the decrease of LPS contents of P. aeruginosa P1, which supported the detachment of outer membrane. CA also downregulated the expression of major genes in LPS biosynthesis, suggesting that CA may inhibit intracellular metabolism of P. aeruginosa P1 cells. Thus, CA increased the intracellular membrane permeability, induced the exfoliation of outer membrane, and disturbed the intracellular metabolism. Damage of intracellular and outer membranes as well as disruption of cell metabolism resulted in cell death eventually. The finding suggested that CA has the potential to be developed as a preservative to control P. aeruginosa-associated foodborne diseases.

Emerging therapies against infections with Pseudomonas aeruginosa

Infections with Pseudomonas aeruginosa have been marked with the highest priority for surveillance and epidemiological research on the basis of parameters such as incidence, case fatality rates, chronicity of illness, available options for prevention and treatment, health-care utilization, and societal impact. P. aeruginosa is one of the six ESKAPE pathogens that are the major cause of nosocomial infections and are a global threat because of their capacity to become increasingly resistant to all available antibiotics. This review reports on current pre-clinical and clinical advances of anti-pseudomonal therapies in the fields of drug development, antimicrobial chemotherapy, vaccines, phage therapy, non-bactericidal pathoblockers, outer membrane sensitizers, and host defense reinforcement.

Sink-Related Outbreaks and Mitigation Strategies in Healthcare Facilities

PURPOSE OF REVIEW

In this review, we summarize recent outbreaks attributed to hospital sinks and examine design features and behaviors that contributed to these outbreaks. The effectiveness of various risk mitigation strategies is presented. Finally, we examine investigational strategies targeted at reducing the risk of sink-related infections.

RECENT FINDINGS

Outbreaks of hospital sink-related infections involve a diverse spectrum of microorganisms. They can be attributed to defects in sink design and hospital wastewater systems that promote the formation and dispersion of biofilm, as well as healthcare practitioner and patient behaviors. Risk mitigation strategies are often bundled; while they may reduce clinical cases, sink colonization may persist. Novel approaches targeting biofilms show promise but require more investigation. Emphasis should be placed on optimizing best practices in sink design and placement to prevent infections. Hospitals should consider developing a rational surveillance and prevention strategy based on the current design and state of their sinks.

Tap out: reducing waterborne Pseudomonas aeruginosa transmission in an intensive care unit

BACKGROUND

Pseudomonas aeruginosa is a ubiquitous and important opportunistic pathogen in immunocompromised or critically ill patients. Nosocomial P. aeruginosa outbreaks have been associated with hospital water sources.

AIM

To describe engineering interventions to minimize contamination of water outlets and the subsequent clinical impact.

METHODS

New tap outlets were fitted at selected outlets across the intensive care unit (ICU). Laboratory testing demonstrated that, following artificial contamination with P. aeruginosa, these taps could be effectively decontaminated using a thermal washer-disinfector. Water samples were collected weekly from new outlets on the ICU over an eight-month period and tested for the enumeration of P. aeruginosa via membrane filtration. Surveillance of P. aeruginosa from clinical specimens was routinely undertaken.

FINDINGS

Prior to the interventions, water sampling on ICU indicated that 30% of the outlets were positive for P. aeruginosa at any one time, and whole genome sequencing data suggested at least 30% transmission from water to patient. Since their installation, weekly sampling of the new tap outlets has been negative for P. aeruginosa, and the number of P. aeruginosa clinical isolates has fallen by 50%.

CONCLUSION

Installation and maintenance of tap outlets free of P. aeruginosa can substantially reduce the number of P. aeruginosa clinical isolates in an ICU.