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Objective: To assess the residual risk of waterborne contamination by Pseudomonas aeruginosa from a water network colonized by a single genotype [sequence type (ST) 299] despite the presence of antimicrobial filters in a medical intensive care unit (ICU)., Methods: During the first 19-month period since the ICU opened, contamination of the water network was assessed monthly by collecting water upstream of the filters. Downstream water was also sampled to assess the efficiency of the filters. P. aeruginosa isolates from patients were collected and compared with the waterborne ST299 P. aeruginosa by multiplex-rep polymerase chain reaction (PCR), pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing. Cross-transmission events by other genotypes of P. aeruginosa were also assessed., Results: Overall, 1.3% of 449 samples of filtered water were positive for P. aeruginosa in inoculum, varying between 1 and 10 4  colony-forming units/100 mL according to the tap. All P. aeruginosa hydric isolates belonged to ST299 and displayed fewer than two single nucleotide polymorphisms (SNPs). Among 278 clinical isolates from 122 patients, 10 isolates in five patients showed identical profiles to the hydric ST299 clone on both multiplex-rep PCR and PFGE, and differed by an average of fewer than five SNPs, confirming the water network reservoir as the source of contamination by P. aeruginosa for 4.09% of patients. Cross-transmission events by other genotypes of P. aeruginosa were responsible for the contamination of 1.75% of patients., Discussion/conclusion: Antimicrobial filters are not sufficient to protect patients from waterborne pathogens when the water network is highly contaminated. A microbiological survey of filtered water may be needed in units hosting patients at risk of P. aeruginosa infections, even when all water points-of-use are fitted with filters., (Copyright © 2024 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Background: Pseudomonas aeruginosa (PA) is a common cause of healthcare-associated infection (PA-HAI) in the intensive care unit (ICU)., Aim: To describe the epidemiology of PA-HAI in ICUs in Ontario, Canada, and to identify episodes of sink-to-patient PA transmission., Methods: This was a prospective cohort study of patients in six ICUs from 2018 to 2019, with retrieval of PA clinical isolates, and PA-screening of antimicrobial-resistant organism surveillance rectal swabs, and of sink drain, air, and faucet samples. All PA isolates underwent whole-genome sequencing. PA-HAI was defined using US National Healthcare Safety Network criteria. ICU-acquired PA was defined as PA isolated from specimens obtained ≥48 h after ICU admission in those with prior negative rectal swabs. Sink-to-patient PA transmission was defined as ICU-acquired PA with close genomic relationship to isolate(s) previously recovered from sinks in a room/bedspace occupied 3-14 days prior to collection date of the relevant patient specimen., Findings: Over ten months, 72 PA-HAIs occurred among 60/4263 admissions. The rate of PA-HAI was 2.40 per 1000 patient-ICU-days; higher in patients who were PA-colonized on admission. PA-HAI was associated with longer stay (median: 26 vs 3 days uninfected; P < 0.001) and contributed to death in 22/60 cases (36.7%). Fifty-eight admissions with ICU-acquired PA were identified, contributing 35/72 (48.6%) PA-HAIs. Four patients with five PA-HAIs (6.9%) had closely related isolates previously recovered from their room/bedspace sinks., Conclusion: Nearly half of PA causing HAI appeared to be acquired in ICUs, and 7% of PA-HAIs were associated with sink-to-patient transmission. Sinks may be an under-recognized reservoir for HAIs., (Crown Copyright © 2024. Published by Elsevier Ltd. All rights reserved.)

Aim: To determine whether pulsed-field gel electrophoresis (PFGE) accurately recognizes isolates belonging to clusters defined by techniques based on whole-genome sequencing (WGS) using Pseudomonas aeruginosa as a model., Methods: We selected 65 isolates of ST395 P. aeruginosa isolated in seven European hospitals between 1998 and 2012. Isolates were typed by PFGE and sequenced by WGS. A core genome multi-locus sequence typing (cgMLST) analysis based on 3831 genes was performed with a homemade pipeline., Findings: PFGE identified eight pulsotypes and cgMLST differentiated nine clusters and nine singletons. Five cgMLST clusters and pulsotypes (31/65 isolates) coincided perfectly. Isolates without evident epidemiological links grouped by PFGE were separated by cgMLST (16/65 isolates) differentiating cities, suggesting that PFGE should be kept for the investigation of local outbreaks. Importantly, hypermutator isolates still shared the pulsotype with their parents (16/65 isolates), whereas they were not recognized by cgMLST. This shows that PFGE was less affected than WGS-based typing by the accelerated genetic drift that occurs in epidemic P. aeruginosa., Conclusions: although WGS-based typing has logically become the new reference standard, we show here that the PFGE can be used with confidence for the investigation of local outbreaks caused by P. aeruginosa., (Copyright © 2020 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

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., (Copyright © 2018 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Objectives: Flexible endoscopes are difficult to decontaminate, and endoscope-associated infections are increasing. This report describes an outbreak of multi-drug resistant Pseudomonas aeruginosa identified following an increase in incidence of clinical infections associated with flexible ureteroscopy at a tertiary care centre in the UK., Methods: Clinical, laboratory and central decontamination unit (CDU) records were reviewed to determine the extent of the problem, and links to the used endoscopes. Audits of the ureteroscopy procedure, endoscopy unit and CDU were performed. Endoscopes were sampled, cultured and examined for structural integrity. All available isolates were typed., Results: Thirteen patients developed clinical infections linked to two flexible ureteroscopes. The first ureteroscope was likely colonized from a known infected patient and the second ureteroscope after use on another patient infected by the first. Risk factors identified include surface cuts, stretching and puckering of the outer cover in both ureteroscopes, absence of bedside cleaning, overnight delay between the ureteroscopy and decontamination, inadequate drying after decontamination and non-traceability of connector valves., Conclusions: The adequacy of flexible endoscope decontamination depends on numerous steps. With the increasing global incidence of multi-drug resistant organisms, stringent monitoring of the flexible endoscopy process by users and decontamination units is essential., (Copyright © 2019 The Healthcare Infection Society. All rights reserved.)

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., (Copyright © 2018 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Background: Pseudomonas aeruginosa (PA) is a Gram-negative environmental organism that can cause severe infection in immunosuppressed patients, including preterm neonates. In recent years, it has become common practice to screen neonates for PA colonization., Aim: To assess the value of screening neonates for PA in (1) predicting the risk of developing severe PA infection and (2) directing infection control practice., Methods: Between August 2012 and September 2015, babies admitted to the neonatal intensive care unit (NICU) at North Bristol NHS Trust were screened routinely for PA colonization on admission and weekly thereafter. Data were also collected on babies who developed PA infection. Environmental samples from the NICU were tested for the presence of PA. Variable number tandem repeat (VNTR) typing was performed on all strains of PA from babies and the environment., Findings: No babies with positive screens subsequently developed PA infection. There was no VNTR strain evidence supporting cross-infection from the environment or other babies., Conclusion: Screening neonates for PA did not identify babies who subsequently developed PA infection. Following cessation of screening in September 2015, there was no increase in the number of babies identified with PA infection., (Copyright © 2018 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Background: Carbapenem-resistant Gram-negative bacteria (CRGNB) infections constitute a global threat for critically ill patients and the outcome of their hospitalization. Early identification of CRGNB through rectal surveillance cultures and routine infection control measures including contact precautions, use of appropriate disinfectants, staff education on cleaning, and hand hygiene may reduce the dissemination of CRGNB., Aim: To assess the impact of enhanced infection control measures on CRGNB infections in a nine-bed polyvalent intensive care unit in a tertiary level hospital in an endemic area., Methods: A quasi-experimental study, which included patients with CRGNB infection retrospectively for six months and those participating in an active surveillance programme prospectively for the subsequent 22 months. Active surveillance programme (weekly rectal swabs) was implemented including two sub-periods with infection control measures and enhanced infection control measures. CRGNB incidence, prevalence, colonization pressure, infections and compliance with infection control measures and enhanced infection control measures were recorded. Analysis was performed through time-series and interrupted time-series., Findings: During the active surveillance programme, enhanced infection control measures led to a steeper downwards trend in incidence, prevalence, and colonization pressure for CRGNB compared to the infection control measures sub-period. The linear trend was for carbapenem-resistant Klebsiella pneumoniae (CRKP) and Pseudomonas aeruginosa (CRPA) infections to decrease from 19.6 to 8.1 infections per 1000 bed-days (IBD) (P = 0.001) and from 5.1 to 1.79 IBD (P = 0.043), respectively. By contrast, carbapenem-resistant Acinetobacter baumannii infections increased from 5.2 to 15.3 IBD (P = 0.001)., Conclusion: Enhanced infection control measures including enhanced hand hygiene, active surveillance combined with contact precautions, education, audits and feedback policies and interventions could reduce CRKP and CRPA in endemic areas., (Copyright © 2018 The Healthcare Infection Society. All rights reserved.)

Background: Pseudomonas aeruginosa healthcare outbreaks can be time consuming and difficult to investigate. Guidance does not specify which typing technique is most practical for decision-making., Aim: To explore the usefulness of whole-genome sequencing (WGS) in the investigation of a P. aeruginosa outbreak, describing how it compares with pulsed-field gel electrophoresis (PFGE) and variable number tandem repeat (VNTR) analysis., Methods: Six patient isolates and six environmental samples from an intensive care unit (ICU) positive for P. aeruginosa over two years underwent VNTR, PFGE and WGS., Findings: VNTR and PFGE were required to fully determine the potential source of infection and rule out others. WGS results unambiguously distinguished linked isolates, giving greater assurance of the transmission route between wash-hand basin water and two patients, supporting the control measures employed., Conclusion: WGS provided detailed information without the need for further typing. When allied to epidemiological information, WGS can be used to understand outbreak situations rapidly and with certainty. Implementation of WGS in real-time would be a major advance in day-to-day practice. It could become a standard of care as it becomes more widespread due to its reproducibility and lower costs., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Water networks in hospitals are frequently contaminated by opportunistic premise plumbing pathogens (OPPPs) leading to installation of antimicrobial filters on water points-of-use (POU) in order to limit patients' exposure., Aim: To assess the spread of OPPPs through secondary water routes (outside the plumbing system) in an adult haematology unit in which 52 out of 73 water POU were high risk for patients and protected by antimicrobial filters., Methods: An observational audit identified six secondary water routes for which bacteria tracking and typing were performed in 315 surface samplings. Bacterial isolates were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and compared to the infra-species level by multiplex repetitive element sequence-based polymerase chain reaction and/or by restriction fragment length polymorphism in pulse-field gel electrophoresis., Findings: Pseudomonas aeruginosa and Stenotrophomonas maltophilia, as well as non-pathogenic OPPP indicators, were detected in water collected upstream of antimicrobial filters. P. aeruginosa was the sole OPPP retrieved from tested surfaces (5.1%). The same clone of P. aeruginosa spread from water source to dry surfaces in the same room and cross-contaminated two sinks in different rooms. Three clones of non-pathogenic OPPP indicators spread more widely in different rooms., Conclusion: A strategy based on filtration of most (but not all) water POU in a haematology unit could be sufficient to limit the spread of OPPPs to the environment, provided a functional mapping of 'high-risk' POU has been undertaken. The residual spread of OPPPs and OPPP indicators linked to non-filtered water POU argues for careful monitoring of non-filtered water use., (Copyright © 2017 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Objective: To study the association between the results of water samples and Pseudomonas aeruginosa healthcare-associated cases in a French university hospital., Methods: Generalized Estimating Equations were used on complete case and imputed datasets. The spatial unit was the building and the time unit was the quarter., Results: For the period 2004-2013, 2932 water samples were studied; 17% were positive for P. aeruginosa. A higher incidence of P. aeruginosa cases was associated with a higher proportion of positive water samples (P=0.056 in complete case analysis and P=0.031 with the imputed dataset). The association was no longer observed when haematology and intensive care units were excluded, but was significant in analyses of data concerning intensive care units alone (P<0.001)., Conclusion: This study suggests that water outlet contamination in hospitals can lead to an increase in healthcare-associated P. aeruginosa cases in wards dealing with susceptible patients, but does not play a significant role in other wards., (Copyright © 2016 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Background: Pseudomonas aeruginosa is a leading cause of healthcare-associated infections in the intensive care unit (ICU)., Aim: To investigate an unexplained increase in the incidence of P. aeruginosa recovered from clinical samples in the ICU over a two-year period., Methods: After unsuccessful epidemiological investigation by conventional tools, P. aeruginosa clinical isolates of all patients hospitalized between January 2010 and July 2012 were typed by a novel double-locus sequence typing (DLST) method and compared to environmental isolates recovered during the investigation period., Findings: In total, 509 clinical isolates from 218 patients and 91 environmental isolates were typed. Thirty-five different genotypic clusters were found in 154 out of 218 patients (71%). The largest cluster, DLST 1-18, included 23 patients who were mostly hospitalized during overlapping periods in the burn unit. Genotype DLST 1-18 was also recovered from floor traps, shower trolleys and the shower mattress in the hydrotherapy rooms, suggesting environmental contamination of the burn unit as the source of the outbreak. After implementation of appropriate infection control measures, this genotype was recovered only once in a clinical sample from a burned patient and twice in the environment, but never thereafter during a 12-month follow-up period., Conclusion: The use of a novel DLST method allowed the genotyping of a large number of clinical and environmental isolates, leading to the identification of the environmental source of a large unrecognized outbreak in the burn unit. Eradication of the outbreak was confirmed after implementation of a continuous epidemiological surveillance of P. aeruginosa clones in the ICU., (Copyright © 2016 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Pseudomonas aeruginosa is an important nosocomial pathogen, colonizing hospital water supplies including taps and sinks. We report a cluster of P. aeruginosa acquisitions during a period of five months from tap water to patients occupying the same burns single room in a critical care unit. Pseudomonas aeruginosa cultured from clinical isolates from four different patients was indistinguishable from water strains by pulsed-field gel electrophoresis. Water outlets in critical care may be a source of P. aeruginosa despite following the national guidance, and updated guidance and improved control measures are needed to reduce the risks of transmission to patients., (Copyright © 2016 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Background: During an environmental investigation of Pseudomonas aeruginosa in intensive care units, the liquid hand soap was found to be highly contaminated (up to 8 × 10(5)cfu/g) with this pathogen. It had been used over the previous five months and was probably contaminated during manufacturing., Aim: To evaluate the burden of this contamination on patients by conducting an epidemiological investigation using molecular typing combined with whole genome sequencing (WGS)., Methods: P. aeruginosa isolates from clinical specimens were analysed by double locus sequence typing (DLST) and compared with isolates recovered from the soap. Medical charts of patients infected with a genotype identical to those found in the soap were reviewed. WGS was performed on soap and patient isolates sharing the same genotype., Findings: P. aeruginosa isolates (N = 776) were available in 358/382 patients (93.7%). Only three patients (0.8%) were infected with a genotype found in the soap. Epidemiological investigations showed that the first patient was not exposed to the soap, the second could have been exposed, and the third was indeed exposed. WGS showed a high number of core single nucleotide polymorphism differences between patients and soap isolates. No close genetic association was observed between soap and patient isolates, ruling out the hypothesis of transmission., Conclusion: Despite a highly contaminated soap, the combined investigation with DLST and WGS ruled out any impact on patients. Hand hygiene performed with alcohol-based solution for >15 years was probably the main reason. However, such contamination represents a putative reservoir of pathogens that should be avoided in the hospital setting., (Copyright © 2016 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Pseudomonas aeruginosa has been recovered in hospitals from many different sources including sinks and taps. Because P. aeruginosa is one of the main agents of nosocomial infections and increasingly resistant to antibiotics, environmental reservoirs in hospital settings are of great concern. We report here on a cluster of five cases of infection by P. aeruginosa expressing VIM carbapenemases (VIM-PA) in a nephrology intensive care unit. Our investigation pointed to transmission of VIM-PA via hands related to a contaminated tap. VIM-PA may be cross-transmitted to other patients if an environmental reservoir exists. Sinks and taps should be well designed and thoroughly cleaned and disinfected, and use of alcohol hand rub should be promoted., (Copyright © 2015 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Background: Pseudomonas aeruginosa is a major cystic fibrosis (CF) pathogen causing chronic respiratory infections and posing a risk for cross-infection between patients with CF., Aim: To propose an algorithm for long-term surveillance of P. aeruginosa and assess its suitability for monitoring the epidemiological situation at a CF centre with approximately 300 patients., Methods: Over a nine-year period, over 300 P. aeruginosa isolates from 131 infected patients were tested by multi-locus sequence typing (MLST) and/or random amplified polymorphic DNA (RAPD) assay., Findings: MLST analysis led to the identification of 97 different sequence types which were distributed among 17 RAPD-generated (pseudo)clusters. This indicates that the easy-to-perform RAPD assay is only suitable for intra-individual, not interindividual, strain analyses. No epidemic strains were observed. Longitudinal analysis revealed that 110 of the 131 patients were infected with the same strain over the observation period, whereas 21 patients had a strain replacement or a new infection. Chronic infection was found in 99 of the 131 patients, and the remaining 32 patients met the criteria for intermittent infection (as defined by the Leeds criteria). Eighteen of the 32 patients (56%) with intermittent infection were infected with the same strain for up to nine years., Conclusion: The strain type only changed in 16% of 131 patients with chronic or intermittent infection. As many as 56% of patients considered to have intermittent infection were actually chronically infected with the same strain for many years., (Copyright © 2015 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Over a four-month period, ten patients were suspected of having acquired nosocomial infection to P. aeruginosa in the ear, nose, and throat department. Environmental and clinical isolates were compared. Only water from a drinking water fountain was contaminated by P. aeruginosa. This isolate and those of three patients had indistinguishable random amplified polymorphic DNA profiles. These patients had serious oncology diseases. The drinking water fountain was used for their alimentation by percutaneous endoscopic gastrostomy and was the origin of the outbreak. Another type of drinking fountain with a terminal ultraviolet treatment was installed, following which no new infections linked to drinking water were identified., (Copyright © 2015 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Background: Metallo-β-lactamases (MBLs) have emerged as one of the most important bacterial resistance mechanisms because of their ability to hydrolyse virtually all β-lactam agents. MBL-producing Pseudomonas aeruginosa (MBL-PA) are an important cause of nosocomial infections, particularly in intensive care units (ICUs), where they are associated with serious infections and present a significant clinical risk., Aim: To assess the molecular epidemiology, risk factors and outcomes of nosocomial infections caused by MBL-PA in a teaching hospital in Southern Brazil., Methods: From January 2001 to December 2008, 142 carbapenem-resistant P. aeruginosa strains were isolated from distinct clinical samples from hospitalized patients. These isolates were screened for MBLs, and underwent polymerase chain reaction, sequencing and pulsed-field gel electrophoresis (PFGE). Patients infected with carbapenem-resistant MBL-PA were considered as cases, and patients infected with non-MBL-PA were considered as controls., Findings: Eighty-four of 142 patients with positive carbapenem-resistant P. aeruginosa cultures met the criteria of the Centers for Disease Control and Prevention for infection. Fifty-eight patients were infected with MBL-PA (69%) and 26 patients were infected with non-MBL-PA (31%). Multi-variate analysis revealed that ICU stay [P = 0.003, odds ratio (OR) 4.01, 95% confidence interval (CI) 1.15-14.01] and urinary tract infection (P = 0.001, OR 9.67, 95% CI 1.72-54.48) were important risk factors for MBL-PA infection. Patients infected with MBL-PA showed faster onset of infection (P = 0.002) and faster progression to death (P = 0.04)., Conclusions: These results showed the severity of MBL-PA infections, and demonstrated the urgent need for strategies to improve infection control measures to prevent an increase in these nosocomial infections., (Copyright © 2014 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Background: In December 2011 and early 2012 four neonates died from Pseudomonas aeruginosa bacteraemia in hospitals in Northern Ireland., Aim: To assess whether P. aeruginosa was associated with the neonatal unit taps and whether waterborne isolates were consistent with patient isolates., Methods: Thirty taps and eight flow straighteners from the relevant hospitals were categorized and dismantled into 494 components and assessed for aerobic colony and P. aeruginosa counts using non-selective and selective agars. P. aeruginosa isolates were typed by variable number tandem repeat (VNTR) analysis. Selected tap components were subjected to epifluorescence and scanning electron microscopy to visualize biofilm., Findings: The highest P. aeruginosa counts were from the flow straighteners, metal support collars and the tap bodies surrounding these two components. Complex flow straighteners had a significantly higher P. aeruginosa count than other types of flow straighteners (P < 0.05). Highest aerobic colony counts were associated with integrated mixers and solenoids (P < 0.05), but there was not a strong correlation (r = 0.33) between the aerobic colony counts and P. aeruginosa counts. Representative P. aeruginosa tap isolates from two hospital neonatal units had VNTR profiles consistent with strains from the tap water and infected neonates., Conclusion: P. aeruginosa was predominantly found in biofilms in flow straighteners and associated components in the tap outlets and was a possible source of the infections observed. Healthcare providers should be aware that water outlets can be a source of P. aeruginosa contamination and should take steps to reduce such contamination, monitor it and have strategies to minimize risk to susceptible patients., (Copyright © 2013 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

We report a nosocomial outbreak of urinary tract infection by extremely drug resistant Pseudomonas aeruginosa, susceptible only to colistin. Infection in three patients followed urodynamic studies. Two of the three patients were children, one of whom also developed urosepsis. The investigation led to detection of contaminated pressure transducers. Genotyping confirmed that patient and transducer isolates were identical. These transducers were not labelled as 'single use only' despite the possibility that contaminated urine may reflux and mix with the fluid in the device. The issue of re-usable versus single-use urodynamic devices is discussed., (Copyright © 2013 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Background: Multidrug-resistant Pseudomonas aeruginosa (MDR-P) expressing VIM-metallo-beta-lactamase is an emerging infection control problem. The source of many such infections is unclear, though there are reports of hospital outbreaks of P. aeruginosa related to environmental contamination, including tap water., Aim: We describe two outbreaks of MDR-P, sensitive only to colistin, in order to highlight the potential for hospital waste-water systems to harbour this organism., Methods: The outbreaks were investigated by a combination of descriptive epidemiology, inspection and microbiological sampling of the environment, and molecular strain typing., Findings: The outbreaks occurred in two English hospitals; each involved a distinct genotype of MDR-P. One outbreak was hospital-wide, involving 85 patients, and the other was limited to four cases in one specialized medical unit. Extensive environmental sampling in each outbreak yielded MDR-P only from the waste-water systems. Inspection of the environment and estates records revealed many factors that may have contributed to contamination of clinical areas, including faulty sink, shower and toilet design, clean items stored near sluices, and frequent blockages and leaks from waste pipes. Blockages were due to paper towels, patient wipes, or improper use of bedpan macerators. Control measures included replacing sinks and toilets with easier-to-clean models less prone to splashback, educating staff to reduce blockages and inappropriate storage, reviewing cleaning protocols, and reducing shower flow rates to reduce flooding. These measures were followed by significant reductions in cases., Conclusion: The outbreaks highlight the potential of hospital waste systems to act as a reservoir of MDR-P and other nosocomial pathogens., (Copyright © 2012 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

An outbreak of multidrug-resistant (MDR) Pseudomonas aeruginosa occurred in an acute care hospital in Japan, which lasted for more than three years. During January 2006 to June 2009, 59 hospitalised patients with MDR P. aeruginosa were mainly detected by urine culture in the first half, whereas isolation from respiratory tract samples became dominant in the latter half of the outbreak. Non-duplicate MDR P. aeruginosa isolates were available from 51 patients and all isolates were positive for bla(VIM-2). Pulsed-field gel electrophoresis (PFGE) analysis categorised the isolates into three major clusters; types A, B and C with eight, 19 and 21 isolates, respectively. The outbreak started with patients harbouring PFGE type A strains, followed by type B, and type C strains. Multivariate analysis demonstrated that patients with PFGE type C strains were more likely to be detected by respiratory tract samples (odds ratio: 11.87; 95% confidence interval: 1.21-116.86). Improved aseptic urethral catheter care controlled PFGE type A and type B strains and improvement in respiratory care procedures finally contained the transmission of PFGE type C strains., (Copyright © 2011 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

The aim of this study was to assess the incidence and molecular epidemiology of multidrug-resistant (MDR) Pseudomonas aeruginosa in our university hospital. Analysis included antimicrobial susceptibility profiling, bla gene identification and pulsed-field gel electrophoresis (PFGE). During the one-year study, 654 patients had at least one sample that tested positive for P. aeruginosa, of whom 38 (5.8%) were colonised or infected with an MDR isolate, giving an incidence of 0.1 patient per 1000 patient-days. The 38 non-duplicate isolates yielded 12 different PFGE patterns, three of which included isolates from four patients and one of which included isolates from 15 patients. Two isolates produced acquired extended-spectrum β-lactamase (one OXA-14 and one OXA-28). Genotyping showed that cross-transmission was responsible for about 70% of MDR P. aeruginosa cases although spatio-temporal analysis failed to demonstrate when this might have occurred for most cases. The major epidemic and the three main micro-epidemic clones were already present in our hospital with a more susceptible phenotype. It is likely that some P. aeruginosa clones are endemic in our hospital and that, within these clones, MDR isolates emerge under antibiotic pressure. Our results indicate that cross-transmission plays a major role in the spread of MDR P. aeruginosa and suggest that priority should be given to the improvement of standard hygienic precautions., (Copyright © 2010 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.)

A genotypically indistinguishable strain of Pseudomonas aeruginosa (Australian epidemic strain III: AES III) has previously been found in a proportion of adults with cystic fibrosis (CF) in Tasmania, Australia. The aim of this study was to identify a source of these infections within the major tertiary referral hospital for the State of Tasmania, and to determine if this strain could be isolated from settings other than the CF lung. A total of 120 isolates of P. aeruginosa were collected from clinical and environmental sources within the hospital and from environmental locations in the hospital vicinity. These isolates were genotyped by random amplification of polymorphic DNA (RAPD)-polymerase chain reaction (PCR) and antimicrobial susceptibility testing was performed using the Clinical and Laboratory Standards Institute method. Confirmation of similar genotypes identified by RAPD-PCR was performed using pulsed-field gel electrophoresis with restriction enzyme SpeI. AES III was not recovered from any source other than the respiratory secretions of CF patients. P. aeruginosa in the non-CF settings was found to be panmictic, and no cross-infection or acquisition of hospital environment strains by patients was observed.

This study examined tap water as a source of Pseudomonas aeruginosa in a medical intensive care setting. We prospectively screened specimens of patients, tap water and hands of healthcare workers (HCWs) over a six-month period in a 16-bed medical intensive care unit. Molecular relatedness of P. aeruginosa strains was investigated by pulsed-field gel electrophoresis. A total of 657 tap water samples were collected from 39 faucets and 127 hands of HCWs were sampled. P. aeruginosa was found in 11.4% of 484 tap water samples taken from patients' rooms and in 5.3% of 189 other tap water samples (P<0.01). P. aeruginosa was isolated from 38 patients. Typing of 73 non-replicate isolates (water samples, hands of HCWs and patients) revealed 32 major DNA patterns. Eleven (52.4%) of the 21 faucets were contaminated with a patient strain, found before isolation from tap water in the corresponding room in nine cases, or from the neighbouring room in two cases. Among seven P. aeruginosa strains isolated from HCW hands, the genotype obtained was the same as that from the last patient they had touched in six cases, and in the seventh with the last tap water sample used. More than half of P. aeruginosa carriage in patients was acquired via tap water or cross-transmission. Carriage of P. aeruginosa by patients was both the source and the consequence of tap water colonisation. These results emphasise the need for studies on how to control tap water contamination.

Non-touch taps, now common in hospitals, can easily be contaminated with Pseudomonas aeruginosa. We report our experience with 87 non-touch taps in a newly built wing of our teaching hospital contaminated with P. aeruginosa from the central pipe water system. Serotyping and genotyping of strains revealed genetic diversity of isolates, but also showed that major clones were able to persist for long periods of time in non-touch taps despite chlorination. It is notoriously difficult to decontaminate such taps with biocides and disinfectants. We describe an easy and economical procedure for the eradication of P. aeruginosa contamination from non-touch taps that does not require their removal.

A total of 85 Pseudomonas aeruginosa isolates were obtained from October 1999 to April 2000 in a tertiary care hospital in Rio de Janeiro, Brazil. The imipenem susceptibility was evaluated by disk diffusion and agar dilution methods, and the clonal relationship among 67 isolates was examined by macrorestriction profile analysis following pulsed-field gel electrophoresis. Imipenem resistance was observed in 52 (61.2%) isolates. Imipenem-resistant P. aeruginosa isolates were separated into 10 genotypes, 73% of which belonged to genotype A. Identification of a single P. aeruginosa clone with a high rate of imipenem resistance emphasizes the need to control the transmission of this organism among patients.

Within six months of opening of the new Dublin Dental Hospital in September 1998, areas of corrosion were observed on many of the baseplates of the hospital's 103 dental chair units (DCUs) at the site of attachment of the suction hoses. The corroded areas were heavily contaminated with Pseudomonas spp. and related genera posing a risk of cross-infection, particularly for immunocompromised patients. These species were used as marker organisms to investigate the source of the contamination. P. aeruginosa was the predominant species recovered from 41 selected DCU baseplates (61% prevalence), whereas P. putida (46% prevalence) and P. aeruginosa (43% prevalence) were predominant at the attachment ends of 37 selected high-volume suction hoses. Forty-one selected isolates of P. aeruginosa from 13 DCU baseplates, 16 high-volume suction hoses and 12 coarse filter housings (another suction system site) from 19 separate DCUs were serotyped to determine the similarity of isolates at each site. The majority of isolates (68.3%) belonged to serotype O:10, while the remainder belonged to serotypes O:6 (7.3%), O:11 (7.3%), O:14 (9.8%) and O:5/O:16 (7.3%). Of the isolates from DCU baseplates, additional isolates with the same serotype were recovered from other suction system sites in 10/13 (77%) cases. Isolates of only one serotype were recovered from each of the 19 DCUs investigated. Forty-one serotyped isolates were also subject to computer-assisted analysis of SpeI-generated DNA fingerprint profiles, and similarity coefficient (S(AB)s) values were calculated for each pairwise combination of isolate profiles. The data obtained showed that the isolates consisted of two distinct main populations, each containing separate clades corresponding to specific serotypes. Serotype O:6 (three isolates), O:11 (three isolates) and O:5/O:16 (three isolates) belonged to a single strain in each case. Serotypes O:14 (four isolates) and O:10 (28 isolates) belonged to two strains in each case. The two serotype O:10 strains, termed fingerprint groups I (four isolates from three DCUs) and II (24 isolates from 10 DCUs), were the most distantly related of all the strains identified. These findings demonstrated that the hospital DCUs had become colonized with a small number of P. aeruginosa strains, one of which (serotype O:10, fingerprint group II) predominated. These results also confirmed that DCU baseplate contamination was most likely to be due to leakage from suction system hoses at the baseplate attachment sites, probably due to loosening during use. Replacement hose connectors that firmly retained the suction hoses in the attachment sites so that they could not be loosened by movement of the suction hoses solved this problem, and eliminated further contamination of the DCU baseplates.

We conducted an environmental survey in the Liverpool adult cystic fibrosis (CF) centre in order to determine the extent of environmental contamination with an epidemic strain of Pseudomonas aeruginosa that colonizes most CF patients in Liverpool, and to identify possible reservoirs and routes of cross-infection. In addition, we studied the survival of this strain on dry surfaces, compared with that of other CF P. aeruginosa strains, to explore factors that might contribute to its high transmissibility. Samples were collected from staff, patients and the environment (drains, bath tubs, showers, dry surfaces, respiratory equipment and air) in the inpatient ward and outpatient clinic. P. aeruginosa strains were tested using a new polymerase chain reaction amplification assay specific for the Liverpool epidemic strain (LES). LES was isolated from patients' hands, clothes and bed linen. Environmental contamination with LES was only detected in close proximity to colonized patients (external surfaces of their respiratory equipment, and spirometry machine tubing and chair) and was short-lived. No persistent environmental reservoirs were found. LES was detected in the majority of air samples from inside patients' rooms, the ward corridor and the outpatient clinic. Survival of LES on dry surfaces was significantly longer than that for some other strains tested, but not compared with other strains shown not to be transmissible. Improved environmental survival on its own, therefore, cannot explain the high transmissibility of this epidemic strain. Our study suggests that airborne dissemination plays a significant role in patient-to-patient spread of LES, and confirms the need to segregate those patients colonized by epidemic P. aeruginosa strains from all other CF patients.

Because of a high prevalence of Pseudomonas aeruginosa infections, we conducted an epidemiological study to assess the need for systematic surveillance, as well as the value of applying barrier precautions toP. aeruginosa carriers. From July 1997 to February 1998, we conducted a prospective cohort study in an 18-bed medical intensive care unit (ICU), which is part of the infectious diseases department in a 1200-bed tertiary-care teaching hospital. Rectal and oropharyngeal swabs were obtained on admission and twice weekly. Acquired strains were genotypically characterized by pulsed-field gel electrophoresis (PFGE). A risk factor analysis for carriage, colonization and infection was performed. Among 269 eligible patients, 116 (43%) were P. aeruginosa carriers, with 46 (17%) detected on admission and 70 (26%) who acquired carriage during their stay in ICU. Among these 70 patients, 29 became colonized (N=13) or developed infection (N=16). Conversely, in the 121 patients who remained free of carriage, no colonization or infection were detected. Genotyping analysis using PFGE was performed for 81/85 (95%) acquired strains in 67 patients. The same genotype I was observed for 58/81 (70%) of these strains issued from 47 patients, and a distinct genotype II affected two other patients (three strains). The last 20 strains were not genetically related. In a multivariate model, mechanical ventilation was associated with the acquisition of P. aeruginosa carriage. Antibiotics ineffective against P. aeruginosa significantly increased the risk of colonization or infection in ICU. Although several recent studies concluded that endogenous sources account for the majority of P. aeruginosa colonizations or infections, we conclude that epidemiology may vary according to the ICU, and that cross-colonization (i.e., exogenous source) may occur and warrant reinforced barrier precautions.

Clinical isolates of Pseudomonas aeruginosa were obtained during a half-year screening period of five different wards of the La Rabta Hospital (Tunis). Distinct clinical isolates (N= 82) were obtained from patients, 40 (48%) of which originated from the Department of Otolaryngology. In order to define the local epidemiology of this opportunistic organism, all strains were serotyped, analysed for pyocin production and genetically characterized with the help of pulsed-field gel electrophoresis (PFGE). The data show that, despite the frequent occurrence of identical serotypes, most of the isolates represent unique pyocin types (N= 53) and genotypes (N= 64). A combination of the pyocin and PFGE data showed that nearly all strains were of unique types, except for two pairs of strains. A limited number of strain clusters was observed on the basis of DNA typing data alone. This involved eight genotypes, some of which were clustered with respect to clinical environment or time. Genotype 22 occurred most frequently (6/83, 7%) and independently of time and locale, indicating that it may represent either a clonal type constituting a major fraction of all P. aeruginosa isolates in the region or a more prevalent organism. Despite a relatively high incidence of P. aeruginosa infections, the polyclonality of these strains shows that, in La Rabta Hospital, pseudomonal infections are not primarily due to excessive spread of a single bacterial genotype., (Copyright 2001 The Hospital Infection Society.)

A clonal origin for European isolates of antibiotic multi-resistant Pseudomonas aeruginosa serotype O12 has been suggested. This study was designed to assess the value and limitations of several typing methods for the investigation of outbreaks due to this serotype. In Hôpital de Rodez, France, this organism is endemic, and a prospective clinical epidemiological study was undertaken over a 15 month period, encompassing all patients at the hospital from whom P. aeruginosa O12 was isolated. All isolates were examined by auxanogram, antibiogram, phage-typing, electrophoresis of esterases and pulsed-field gel electrophoresis of DNA. The results suggest that (1) the methods used did not clearly differentiate between clinically-related and epidemiologically-unrelated European isolates, (2) in Hôpital de Rodez, while some isolates were likely to have been transmitted from patient-to-patient, most infections or colonizations with this organism were sporadic and their origin is unknown. The limits of typing methods for the investigation of outbreaks of nosocomial infection with multi-resistant P. aeruginosa O12 are emphasized.

We assessed the discriminatory power of pulsed-field gel electrophoresis (PFGE) for the analysis of DNA restriction fragment length polymorphism (RFLP) in Pseudomonas aeruginosa. We determined DraI PFGE-RFLP of DNA of unrelated clinical and environmental strains, and clinical strains isolated from two intensive care units of the Besançon University Hospital. The typeability and reproducibility was 100%. The discriminatory index was 0.998, and the DNA patterns were stable in vitro and in vivo. There was a very low correlation between PFGE-RFLP and traditional typing methods. The typeability, reproducibility, the high discriminatory power and the stability of PFGE-RFLP make this a valuable method to be used in conjunction with serotyping. Further standardization and quantitative interpretation are possible and should lead to this technique becoming a library typing system.

In order to study the long-term distribution and population dynamics of Pseudomonas aeruginosa strains in a highly contaminated hospital environment, two 4-week epidemiological studies, with an interval of 4 years, were carried out in the cystic fibrosis (CF) ward of the Paediatric Clinic of the Medical School of Hannover. Out of the 1948 specimens taken, P. aeruginosa was mainly identified in those from moist, inanimate sources (200 isolates) and hospitalized CF patients (168 isolates). A correlation was established between the frequency with which P. aeruginosa-positive patients came into contact with hospital facilities and the rate of contamination of these facilities. Rooms reserved for colonized patients were more frequently contaminated with P. aeruginosa in contrast to function rooms in the same ward and the outpatient clinic. However, no direct exchange between patients' strains and the inanimate hospital environment was detected. Out of the 11 genotypes of P. aeruginosa found in 1989 and the 13 genotypes found in 1993, four genotypes were present on both occasions. The most predominant clone was found in tap-water, sinks, wash-basins and creams with an incidence of 34 and 68% in the environmental isolates. The strains seemed to have spread into the adjacent control ward during the 4-year interval. Thus, the separation of colonized and non-colonized patients was undermined through the transfer of strains from a highly contaminated environment without additional hygiene precautions.

We report the use of pulsed-field gel electrophoresis (PFGE) and enterobacterial repetitive intergenic consensus (ERIC)-based polymerase chain reaction (PCR) to characterize clinical isolates of Pseudomonas aeruginosa serotype O11 collected from an incident of hospital-acquired infection. Both typing techniques differentiated 20 different strain types among seven epidemiologically related isolates and 22 epidemiologically unrelated isolates. There was complete concordance between these two techniques. Our results indicate that the ERIC-based PCR technique represents a rapid and simple means for typing P. aeruginosa serotype O11 with a level of discrimination equivalent to that of PFGE.

From July to September 1993 in the intensive care unit of the Royal Victoria Hospital there were 10 cases of pneumonia associated with sputum culture of Pseudomonas aeruginosa. The isolates had an identical biotype and pyocine typing profile. The same strain of P. aeruginosa was recovered from the sink plug-hole in two rooms, and the tap handles and ventilator tubing in a third room. All strains were retrospectively typed by the random amplification of polymorphic DNA (RAPD) method using a 26-mer oligonucleotide primer, and were identical in profile. Recommendations to medical and nursing staff included secretion isolation precautions, terminal disinfection after patient discharge, use of disposable vinyl gloves by hospital staff for all body substance contacts, thorough handwashing with 4% chlorhexidine gluconate before and after dealing with all patient contacts, and prompt, appropriate antibiotic treatment for P. aeruginosa pneumonia. RAPD is a simple and effective method to determine the relatedness of P. aeruginosa isolates, and typing results are available within a single working day; thus dramatically increasing its clinical relevance over existing molecular methods.

In order to identify the possible reservoirs and routes of cross-infection with Pseudomonas aeruginosa, samples were collected during a six-week period in autumn 1992 from patients, their visiting parents, staff and the inanimate environment of the Danish Cystic Fibrosis (CF) Centre and from a control ward with common paediatric diseases. All the P. aeruginosa strains were phage typed and serotyped. From 240 CF patients, 310 strains of P. aeruginosa were isolated, and of these 283 (91.3%) belonged to the polyagglutinable phenotype, most often with a short phage type (31/188 or 109). P. aeruginosa was isolated from only six (0.6%) of 1000 swabs taken from the environment. These six environmental strains and 20 P. aeruginosa strains from CF patients with identical serotype and phage type were examined with pulsed field gel electrophoresis. None of the patients harboured strains similar to the environmental strains, indicating the present isolation procedure and hygienic precautions were effective in our CF centre, and prevented contamination of the environment with P. aeruginosa.

Seventy-three environmental and clinical isolates of Pseudomonas aeruginosa recovered from a single hospital over a 6-month period were compared for epidemiological type characteristics. Environmental isolates were obtained from sinks, taps and water, in rooms where patients were treated. The strains represented only six O-antigenic types and 8.2% of them were not typable. Serotype 011 was most frequent in the environment, whereas serotypes 06, 012 and 02,5 predominated among clinical isolates. More than 60% of all isolates belonged to four pyocin types (1, 10, 33 and 45), and approximately 80% were phage typable. Environmental isolates were more sensitive to antibiotics than clinical isolates. There was little correspondence between the types of strains of P. aeruginosa isolated from patients and those isolated from the environment. However, isolates of identical type were frequently recovered from different patients within the same clinic and were found to be related in time and location. We conclude that the environment was not an important source of P. aeruginosa infection and that transfer of organisms was mainly from patient-to-patient.

A total of 1896 isolates of Pseudomonas aeruginosa resistant to aminoglycosides and isolated during the period 1983-1989 in two Belgian general hospitals were included in this study. The most frequently encountered O serotypes were O4, O11, O12 and non-typable isolates. The majority of the isolates showed resistance to extended spectrum beta-lactam antibiotics (cefotaxime, ceftriaxone and cefepime). However, a low degree of resistance was found for ceftazidime. By contrast, amikacin and isepamicin, remained active on a significant number of aminoglycoside resistant isolates. In both hospitals, impermeability and AAC(3)II enzyme production were the most prevalent aminoglycoside resistance mechanisms. There were marked differences between the two hospitals with regard to the distribution of the O-serotypes and resistance profiles.

One hundred and twenty-one clinical isolates of Pseudomonas aeruginosa from patients with hospital-acquired urinary tract infections (UTIs) were studied to determine their major epidemiological markers, including API 20NE profile, O-serotype, pyocin type, phage type, lysogenic state and antibiotic susceptibility. Serotypes O4, O12, O11, O6 and O5 were found with a high frequency, accounting respectively for 23.9%, 23.1%, 12.3%, 8.2% and 5.7% of isolates. Pyocin type 10 was most common (32.2%) followed by types 1 (10.7%), 33 (7.5%) and 105 (4.1%); subtype h was predominant being characteristic of 34.7% of isolates. Most of the strains (69.4%) were either not phage typable or sensitive to phages 68 and 119x. Resistance to gentamicin, tobramycin, amikacin, imipenem and ciprofloxacin was more frequent among strains belonging to serotype O12. The O-serotypes were combined with API 20NE profiles, pyocin and phage types, lysogenic states and antibiotic resistance in order to identify epidemiologically related clones. Within predominant serotypes--O4 and O12--most strains displayed similar but not identical type characteristics, whereas other serotypes were less homogeneous. Our results support the concept that a combination of current typing techniques allows the identification of epidemiologically related P. aeruginosa isolates.

Pyrolysis mass spectrometry (PyMS) was used for rapid interstrain comparison of Pseudomonas aeruginosa isolates from a small outbreak of sternal wound infections in a cardiothoracic surgical ward. The PyMS results were compared with those obtained by conventional O-serotyping. All the isolates were phage non-typable. Evidence obtained from PyMS of identity/non-identity between isolates correlated completely with that obtained by O-typing and correctly identified those isolates comprising the epidemic strain, in one instance in advance of O-serotyping. The speed and versatility of PyMS make it an attractive technique for the initial screening of isolates from nosocomial outbreaks of infection with P. aeruginosa and other organisms.

Samples of fresh vegetables fed to patients in an Oncology and a University Hospital were examined for frequency of recovery and counts of Pseudomonas aeruginosa. Thirty-eight isolates from vegetables as well as 98 clinical isolates recovered during the same period of vegetable collection were serotyped and assayed for pyocin production in order to evaluate the role of vegetables as a source of microorganisms. Pseudomonas aeruginosa was recovered from 19.0% of the vegetable samples. Although 1% hypochlorite solution was used as a sanitizer, 50% of the positive samples were found to harbour more than 100 colony-forming units (cfu) g-1. Lettuce, chicory and watercress yielded the highest frequencies of isolation (P less than 0.05). The pyocin typing and serotyping of clinical strains revealed some types identical to those recovered from vegetables. Among those found in the University Hospital, serotype O4 and pyocin type PT10/b were detected in vegetables and in clinical specimens whereas types O1-PT22/e, O2a-PT10/a, O2a-PT10/b, O4-PT10/a, O11-PT10/a and O11-PT10/b were common in both groups of strains isolated in the Oncology Hospital. Our results strongly suggest that vegetables represent a source of endemic infection with P. aeruginosa for hospitalized patients.

Four neutropenic patients on a haematology ward developed orbital cellulitis due to different strains of Pseudomonas aeruginosa over a 7-month period. Investigation of patients and the ward environment revealed two P. aeruginosa isolates indistinguishable from the infecting strains in a plastic washing bowl and a sink in a single cubicle respectively. These items were unlikely to have been the sources of the infecting strains but were a potential cross infection hazard. Treatment of orbital cellulitis is discussed briefly.

Pseudomonas aeruginosa colonizes the respiratory tract of most older patients with cystic fibrosis. The means by which these bacteria are acquired and the risk for patient-to-patient spread among subjects with cystic fibrosis are poorly understood. We studied the spread of Ps. aeruginosa within a hospital environment. Pseudomonas was rarely recovered from the inanimate environment surrounding patients with cystic fibrosis or from hand or rectal cultures of patients who were colonized in the oropharynx. There was transient cross-colonization with Ps. aeruginosa between patients with cystic fibrosis sharing a hospital room in three of seven pairs studied. In all cases the "new" isolate was recoverable only once and was not found during a 2-year follow-up. Three of four sibling pairs with cystic fibrosis shared the same Ps. aeruginosa serotype(s). The risk of sustained cross-colonization by Ps. aeruginosa between patients with cystic fibrosis appears to be minimal, except under conditions of prolonged close contact.

As a result of occasional water discolouration, the hydrotherapy pool of a large teaching hospital was monitored for free and combined chlorine, alkalinity, calcium hardness, total dissolved solids and cyanuric acid levels together with bacteriological analysis. The hose pipe supplying the pool and the dual water pumps were also examined as potential sources of bacterial contamination. The pool water yielded high counts of Pseudomonas vesicularis, Pseudomonas aeruginosa, and CDC Group IV C2, even in the presence of adequate levels of free chlorine. This was found to be due to high concentrations of cyanuric acid which resulted in a 'chlorine lock'. The source of the P. vesicularis and CDC Group IV C2 was found to be the pool hose and this problem was alleviated by flushing it with water each day before use. The source of the P. aeruginosa was the pool pumps, and was eradicated by regularly shock dosing them with 6-8 ppm of free chlorine.