Ecology of Pseudomonas aeruginosa in the intensive care unit and the evolving role of water outlets as a reservoir of the organism

doi:10.1016/j.ajic.2005.03.006

American Journal of Infection Control

Volume 33, Issue 5, Supplement, June 2005, Pages S41-S49

https://doi.org/10.1016/j.ajic.2005.03.006 Get rights and content

In spite of the significant changes in the spectrum of organisms causing intensive care unit (ICU)-associated infections, Pseudomonas aeruginosa has held a nearly unchanged position in the rank order of pathogens causing ICU-related infections during the last 4 decades. Horizontal transmissions between patients have long been considered the most frequent source of P aeruginosa colonizations/infections. The application of molecular typing methods made it possible, during the last ∼7 years, to identify ICU tap water as a significant source of exogenous P aeruginosa isolates. A review of prospective studies published between 1998 and 2005 showed that between 9.7% and 68.1% of randomly taken tap water samples on different types of ICUs were positive for P aeruginosa, and between 14.2% and 50% of infection/colonization episodes in patients were due to genotypes found in ICU water. Faucets are easily accessable for preventive measures, and the installation of single-use filters on ICU water outlets appears to be an effective concept to reduce water-to-patient transmissions of this important nosocomial pathogen.

Section snippets

The changing microbial spectrum of infections in intensive care

The last 2 decades have witnessed significant changes in the spectrum of microorganisms causing nosocomial infections. Gram-negative enterobacteria, which in the 1970s and 1980s accounted for 30% to 50% of all disease-associated isolates in ICUs,2, 3 have been to a large extent replaced by gram-positive microorganisms such as staphylococci, enterocci, and corynebacteria.4, 5 The relative decrease of infections because of enterobacteria has been achieved by the successful implementation, in most

Role of Pseudomonas aeruginosa

In spite of these significant changes, P aeruginosa has held a nearly unchanged position in the rank order of pathogens causing ICU-related infections for more than 4 decades. In the newest US National Nosocomial Infections Surveillance (NNIS) system report, P aeruginosa continues to represent the third most frequent organism associated with wound or pulmonary infections, the fourth most frequent organism causing urinary tract infection, and the fifth most frequent organism isolated from blood

Antibiotic resistance of P aeruginosa and treatment costs

Of particular concern is the increasing antibiotic resistance of P aeruginosa isolated from ICUs. NNIS data show a rise of resistance rates against commonly used antibiotics such as imipenem, ciprofloxacin, and ceftazidime by 15%, 9%, and 20%, respectively, between the periods 1998-2002 and 2003.¹¹ Data from a single center in Denver, Colorado, showed a dramatic increase of resistance by more than 30% for fluoroquinolones, tobramycin, and imipenem.¹⁹ Multiresistance, defined as resistance to >3

Epidemiologic typing of P aeruginosa

Given the fact that P aeruginosa was discovered more than 100 years ago and that a multitude of scientific studies have dealt with the clinical manifestations, antibiotic resistance, and virulence factors of the organism, it is astonishing that relatively little insight into its reservoirs and transmission pathways has been gained. In contrast to gram-negative enterobacteria, no broadly applicable concept for the prevention of P aeruginosa infections has yet been developed.

One of the reasons

Reservoirs and modes of transmission

Using molecular methods, horizontal strain transmissions were proven to be one of the most frequent causes of acquisition of P aeruginosa in the ICU. A series of carefully performed studies examining the epidemiology of P aeruginosa came from a group of researchers from The Netherlands. In their first study, Bergmans et al described the sequence of colonization in 10 ICU patients later diagnosed with VAP.⁴⁰ Sequential samples taken from the oropharynx, trachea, stomach, and rectum were

Occurrence of P aeruginosa in moist habitats

P aeruginosa is known to thrive well in moist and humid habitats in which the organism can multiply to large numbers, even in the presence of minimal amounts of nutrients. The organism is also a common constituent of polymicrobial biofilms in plumbing systems and drain pipes. In the era of classical typing methods, numerous attempts have been made to identify relationships between disease-associated and waterborne strains.21, 23, 24, 25 However, both because of the variability of classical

Molecular typing data pointing to tap water as a source of P aeruginosa

Studies using molecular typing techniques and comparing water and patient isolates were first initiated in the early 1990s. Tredget et al³⁹ studied an outbreak of wound, respiratory, and bloodstream infections causing significant morbidity in a burn unit in Canada. As demonstrated by pilin gene typing, the strains infecting 59 patients were found to belong to a single genotye that was also detected in hydrotherapy tanks used for immersion of patients. After cessation of hydrotherapy, the strain

Methodologic aspects of testing for P aeruginosa

For future studies of this kind, it will be essential to use a standardized and sensitive technique for the investigation of taps and running water. The study by Blanc et al shows that examining small volumes of water is less sensitive than performing swabs from the inside of outlets.³⁵ We recommend the following procedure for sampling water that proved to be very sensitive in our studies: (1) take water from tap to be examined during a period of less intense use, eg, at 7 am on Monday mornings

Mechanical cleaning of taps and aerators

Uniformly, the above-mentioned studies showed that P aeruginosa colonization of water taps was not a matter of microbial contamination of drinking water supplied by the mains. The microorganism probably gains access to the taps by retrograde contamination, thereafter establishing itself deeply in the bushings of the aerator and mixing valves and in niches and threads of fittings and fixtures. Strategies to keep the organism at low densities should always include careful cleaning and regular

The concept of point-of-use water filtration

In our own study of the surgical ICU of a teaching hospital, we observed approximately 5 to 10 cases of P aeruginosa infection or colonization per month, along with uniformly positive tap water cultures. On this ward, we decided to start a program of point-of-use water filtration using disposable tap-mounted filters used for 7 days. Filtered water proved to be always sterile after mounting the filters. Thereafter, the number of infections and colonizations fell constantly, reaching a level of 1

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The study presents unconventional, bifunctional, heterogeneous antimicrobial agents – Cu₂O-loaded anion exchangers. The synergetic effect of a cuprous oxide deposit and polymeric support with trimethyl ammonium groups was studied against the reference strains of Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 27853. Biological testing (minimum bactericidal concentration, MBC), time- and dose-dependent bactericidal effect (under different conditions – medium composition and static/dynamic culture) demonstrated promising antimicrobial activity and confirmed its multimode character. The standard values of MBC, for all studied hybrid polymers and bacteria, were similar (64–128 mg/mL). However, depending on the medium conditions, due to the copper release into the bulk solution, bacteria were actively killed even at much lower doses of the hybrid polymer (25 mg/mL) and low Cu(II) concentrations in solution (0.01 mg/L). Simultaneously, confocal microscopic studies confirmed the effective inhibition of bacterial adhesion and biofilm formation on their surface. The studies conducted under different conditions showed also the influence of the structure and physical properties of studied materials on the biocidal efficacy and an antimicrobial action mechanism was proposed that could be significantly affected by electrostatic interactions and copper release to the solution. Although the antibacterial activity was also dependent on various strategies of bacterial cell resistance to heavy metals present in the aqueous medium, the studied hybrid polymers are versatile and efficient biocidal agents against bacteria of both types, Gram-positive and Gram-negative. Therefore, they can be a convenient alternative for point-of-use water disinfection systems providing water quality in medical devices such as dental units, spa equipment, and aesthetic devices used in the cosmetic sector.
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Hospital water is often an overlooked yet preventable source of hospital-acquired infections. CDC recommends annual cleaning of water reservoirs in health care settings. In our tertiary care hospital, periodic disinfection and microbiological surveillance of all the water tanks in hospital premises is carried out. The aim of this paper is to report the diversity of bacterial flora noted and the role of cleaning method adopted in our hospital.
This retrospective study was carried out from July 2015 to September 2020. Tanks were cleaned using hydrogen peroxide based method and swabs were collected, pre- and post-cleaning. Any growth noted was identified using MALDI-TOF MS.
A total of 398 swabs were collected during this period. In pre-cleaning samples, 144 (72%) showed growth of 219 microorganisms. Gram-negative organisms (53.7%, 116/216) were more frequently isolated than Gram-positive organisms (46.3%, 100/216). Although the overwhelming majority is generally regarded as non-pathogenic, a few pathogenic bacteria were also recovered. No bacteria were isolated in any of the post-cleaning samples.
Diverse bacteria colonize water tanks over time, some of which are known to cause infections. Hydrogen peroxide is a simple and highly efficacious method of water tank disinfection. More such studies are required with other disinfectants to generate evidence with the ultimate aim of increasing safety of water supplied in hospitals.
Failure of a hollow-fibre shower filter device to prevent exposure of patients to Pseudomonas aeruginosa
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Pseudomonas aeruginosa in hospital water is a risk for invasive infection. Point-of-use (POU) filters are used to reduce patient exposure to the organism, and hollow-fibre filters are becoming more popular. However, retrograde colonization of the filter mechanism may contaminate the effluent.
To assess the efficacy of POU filter head (polysulfone; hollow-fibre matrix) shower filters in preventing the exposure of high-risk patient groups to P. aeruginosa.
Pre-flush (opening the outlet and collecting the first 100 mL of water) samples were analysed to measure P. aeruginosa contamination from 25 shower outlets (∼21% of all showers on the six wards), with and without a hollow-fibre filter. P. aeruginosa was measured in a subset of outlets harbouring P. aeruginosa (sampling period 19^th August 2019 to 10^th January 2020).
Water from all 25 showers was heavily colonized [>300 colony-forming units (cfu)/mL] with P. aeruginosa at the showerhead. P. aeruginosa was found in 32% (8/25) of post-filter shower water effluent samples with a geometric mean of 4x10⁶ cfu/mL (N=4) (6.8x10⁴–2x10⁸). Filters were sampled at 15–150 days of use (median 15 days), with 26% (6/23) of filter units becoming colonized before the expiry date.
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Pseudomonas aeruginosa is a multidrug-resistant bacterial strain with the ability to produce exotoxin A which can pose a serious threat to freshwater ecosystems by having pathogenicity against eukaryotes. Detoxification of exotoxin A and disinfection of P. aeruginosa are the main aims of this study. Using a high dosage of antibiotics might have more toxic effects on ecosystems while cold atmospheric plasma (CAP) can promise reliable, rapid, and environmentally friendly detoxification and disinfection. In this study we produced CAP reinforced by H₂O₂/H₂O cold vapor to detoxify exotoxin A and inactivate P. aeruginosa in freshwater. We used Gammarus roeseli as the indicator of ecotoxicity in freshwater. The mortality of G. roeseli individuals elucidated that 420 s of CAP-based treatment under a surface dielectric barrier discharge (SDBD) set up can effectively passivize exotoxin A in freshwater. Meanwhile, a considerable decline in the concentration of exotoxin A was observed in treated samples due to the disruption of the protein structure. Ignorable side effects and changes to the physiochemical properties were observed. On the other hand, 8.2-log reduction of P. aeruginosa viable cells was observed after 300 s of treatment by our CAP-based strategy. This study also showed that the combination of hydrogen peroxide and CAP can significantly increase the decontamination power of hydrogen peroxide and our strategy can eliminate the need of using high concentrations of H₂O₂ which decreases environmental concerns.
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Ecology of Pseudomonas aeruginosa in the intensive care unit and the evolving role of water outlets as a reservoir of the organism

Section snippets

The changing microbial spectrum of infections in intensive care

Role of Pseudomonas aeruginosa

Antibiotic resistance of P aeruginosa and treatment costs

Epidemiologic typing of P aeruginosa

Reservoirs and modes of transmission

Occurrence of P aeruginosa in moist habitats

Molecular typing data pointing to tap water as a source of P aeruginosa

Methodologic aspects of testing for P aeruginosa

Mechanical cleaning of taps and aerators

The concept of point-of-use water filtration

Am J Med

Am J Infect Control

Diagn Microbiol Infect Dis

Nutrition

Crit Care Nurs Clin North Am

J Cardiothorac Vasc Anesth

Chest

J Hosp Infect

J Hosp Infect

J Hosp Infect

FEMS Immunol Med Microbiol

Clin Microbiol Infect

J Hosp Infect

J Hosp Infect

Ecotoxicol Environ Saf

J Hosp Infect

Nosocomial infection surveillance and control policies

Curr Opin Infect Dis

Predominant pathogens found in the European Prevalence of Infection in Intensive Care Study

Eur J Clin Microbiol Infect Dis

Nosocomial pneumonia in ventilated patients, a prospective randomized evaluation of the Stericath closed suctioning system

Intensive Care Med

Intranasal mupirocin to prevent postoperative Staphylococcus aureus infections

N Engl J Med

Nasal carriage as a source of Staphylococcus aureus bacteremia. Study Group

N Engl J Med

Data summary from January 1992 through June 2004, issued October 2004

Am J Infect Control

Nosocomial infections in combined medical-surgical intensive care units in the United States

Infect Control Hosp Epidemiol

Impact of appropriateness of initial antibiotic therapy on the outcome of ventilator-associated pneumonia

Intensive Care Med

Cefepime versus imipenem-cilastatin for treatment of nosocomial pneumonia in intensive care unit patients: a multicenter, evaluator-blind, prospective, randomized study

Antimicrob Agents Chemother

Nosocomial bloodstream infections in US hospitals: analysis of 24,179 cases from a prospective nationwide surveillance study

Clin Infect Dis

Aetiology and prognosis of bacteraemia in Italy

Epidemiol Infect

Health and economic outcomes of antibiotic resistance in Pseudomonas aeruginosa

Arch Intern Med