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We performed epidemiologic studies at public freshwater bathing sites in Germany to provide a better scientific basis for the definition of recreational water quality standards. A total of 2,196 participants were recruited from the local population and randomized into bathers and nonbathers. Bathers were exposed for 10 min and had to immerse their head at least three times. Water samples for microbiological analysis were collected at 20-min intervals. Unbiased concentration-response effects with no-observed-adverse-effect levels (NOAELs) were demonstrated for three different definitions of gastroenteritis and four fecal indicator organisms. Relative risks for bathing in waters with levels above NOAELs compared with nonbathing ranged from 1.8 (95% CI, 1.2-2.6) to 4.6 (95% CI, 2.1-10.1), depending on the definition of gastroenteritis. The effect of swallowing water provided additional evidence for true dose-response relationships. Based on the NOAELs, the following guide values for water quality are suggested: 100 Escherichia coli, 25 intestinal enterococci, 10 somatic coliphages, or 10 Clostridium perfringens per 100 mL. Recreational water quality standards are intended to protect the health of those consumers who are not already immune or resistant to pathogens that may be associated with indicator organisms. In contrast to current World Health Organization recommendations, we concluded that standards should be based on rates of compliance with NOAELs rather than on attributable risks determined above NOAELs, because these risks depend mainly on the unpredictable susceptibility of the cohorts. Although in theory there is no threshold in real concentration-response relationships, we demonstrated that a NOAEL approach would be a more robust and practical solution to the complex problem of setting standards.

A recently described quantitative rapid cycle real time PCR (LightCycler) assay detects Cryptosporidium parvum after in vitro excystation, which is a surrogate marker for the viability of the organisms. In the original assay the quantification standard is a dilution series of C. parvum oocysts with a microscopically determined excystation rate. The need to keep suspensions of viable oocysts in stock and to continuously monitor their excystation rate, however, renders the assay impracticable for routine application. A synthetic standard was developed to replace the in vivo standard and was calibrated using oocysts with known excystation rates. The standard consists of a 486 bp DNA segment ranging from 229 bp upstream to 79 bp downstream of the actual PCR target site. Aliquots of the standard were frozen and stored at -20 degrees C and at -70 degrees C or lyophilised and stored at room temperature in the dark. For a period of one year samples preserved with each of the three methods were restored every four or five weeks. They were amplified in the LightCycler and the crossing points (CP) were monitored. No significant trend in the raw CP values could be observed for any of the three storage methods. However, when the methods were compared to each other by calculating the CP ratios (-20 degrees C/-70 degrees C; -20 degrees C/lyophilised; -70 degrees C/lyophilised) at the 10 monitoring dates, the CP ratios -20 degrees C/-70 degrees C and -20 degrees C/lyophilised showed a highly significant positive trend (p < 0.0001) while the CP ratio -70 degrees C/lyophilised did not differ from the null hypothesis (p = 0.53). It can be concluded that the latter two preservation methods are both appropriate, while storage at -20 degrees C is less advisable. Calculations based on the molecular weight of the standard and on the assumption of an average yield of three sporozoites per oocyst led to the conclusion that the target sequence is probably located on a double copy gene.

This report describes a new technique for the detection and identification of Salmonella species in food with the use of fluorescent in situ hybridization (FISH) with 23S rRNA-targeted oligonucleotide probes. Two species-specific 23S rRNA-targeted oligonucleotide probes (Sal-1 and Sal-3) were selected, and one (Sal-544) was newly designed. The relative specificities of these probes were compared with those of bacterial 23S rRNA sequences from the GenBank database and tested by in situ hybridization with bacterial cell smears of pure cultures. Fifty-one tested reference strains of Salmonella serovars belonging to subspecies I (enterica) hybridized with these probes. No cross-reactions with 46 other strains of the family Enterobacteriaceae or with another 14 bacterial strains from other families were observed. Storage of a Salmonella Panama test strain under various environmental conditions (2, 5, and 15% NaC1; -20 degrees C, 4 degrees C, and room temperature; pHs of 3.3 to 7.4) did not adversely affect the FISH method. No matrix effects were observed with 18 different kinds of foods. FISH was able to detect Salmonella spp. in 52 (probe Sal-1), 56 (probe Sal-3), and 35 (probe Sal-544) of 225 naturally contaminated food samples after 16 h of incubation in a preenrichment broth. When conventional culture and detection methods were used, Salmonella could be isolated from only 30 of these 225 samples. In contrast, FISH failed to identify Salmonella in only two of the culture-positive samples when Sal-1 and Sal-3 were used and in only three of the culture-positive samples when Sal-544 was used.

DNase I pretreatment of 16S rRNA gene PCR reagents was tested. The DNase I requirement for the elimination of false-positive results varied between 0.1 and 70 IU per master mix depending on the applied Taq polymerase. PCR sensitivity was mostly maintained when 0.1 IU of DNase I was used.

Current theories of CF pathogenesis predict different predisposing "local environmental" conditions and sites of bacterial infection within CF airways. Here we show that, in CF patients with established lung disease, Pseudomonas aeruginosa was located within hypoxic mucopurulent masses in airway lumens. In vitro studies revealed that CF-specific increases in epithelial O(2) consumption, linked to increased airway surface liquid (ASL) volume absorption and mucus stasis, generated steep hypoxic gradients within thickened mucus on CF epithelial surfaces prior to infection. Motile P. aeruginosa deposited on CF airway surfaces penetrated into hypoxic mucus zones and responded to this environment with increased alginate production. With P. aeruginosa growth in oxygen restricted environments, local hypoxia was exacerbated and frank anaerobiosis, as detected in vivo, resulted. These studies indicate that novel therapies for CF include removal of hypoxic mucus plaques and antibiotics effective against P. aeruginosa adapted to anaerobic environments.

We examined samples from the showers and the central water distribution system of a public building with an indoor swimming pool. The pool was used for school and recreational activities and as a sports therapy facility for patients with coronary heart disease. The building's hot water system was contaminated with Legionella pneumophila. Due to the building's intricate piping system, several attempts to completely eliminate legionellae by thermal and chemical disinfection had failed, so an external sanitation company was charged with the installation of a continuous chlorination device in order to keep Legionella concentrations low. The laboratory which was contracted by the sanitation company to monitor bacteria levels after installation of the chlorination device used sampling bottles without sodium thiosulfate and repeatedly reported an absence of Legionella. However, up to 69,000 colony forming particles (CFP) of Legionella pneumophila (Lp) per litre and up to 171 CFP/ml of heterotrophic bacteria could be detected when parallel samples were collected in bottles containing sodium thiosulfate at standard concentrations. Laboratories, epidemiologists, public health officials and technical staff who may be in charge of delivering, preparing or using sterile sampling devices for the collection of environmental samples to be tested for legionellae should be aware that cultures can return false negative results if the sampling containers used to collect chlorinated drinking water or chlorinated pool water samples do not contain a neutralizing agent to instantly inactivate residual halogen biocides. False negative results may lead to a false sense of security regarding the safety of water systems or the success of disinfection measures, and may thus endanger public health or even hinder the epidemiological clarification of outbreaks.

PCR has proved superior to conventional blood culture for diagnosing bacteraemia in the presence of antibiotics. Nevertheless, even PCR might yield false-negative results if the template DNA were to be cleaved by serum DNAases after antibiotics had induced bacterial death. To evaluate the cleavage of bacterial template DNA by human serum DNAase I, serum samples inoculated with purified Escherichia coli DNA were incubated with increasing amounts of recombinant human DNAase (rhDNAase) and then examined by a PCR specific for E. coli. As a prerequisite of potential DNAase attack, the release of E. coli DNA after antibiotic-induced bacterial death was quantified by fluorescence microscopy and flow cytometry. Finally, the influence of rhDNAase on the PCR-based detection of antibiotic-killed E. coli in serum was assessed. The results indicated that purified E. coli DNA is remarkably stable in human serum; positive PCR results did not decrease significantly until the ratio of recombinant human DNAase I:E. coli rose to 106:1. As only 14.8-28.4% of the total E. coli DNA was released after antibiotic killing, the PCR-based detection of E. coli fell by only 10% when cefotaxime-killed E. coli were incubated with rhDNAase. It was concluded that human serum DNAases and antibiotic killing do not compromise the reliability of PCR examinations for bacteraemia.

In Staphylococcus aureus infection hemolysis caused by the extracellular protein alpha-toxin encoded by hla is thought to contribute significantly to its multifactorial virulence. In vitro, subinhibitory concentrations of beta-lactam antibiotics and fluoroquinolones increase the levels of hla and alpha-toxin expression, whereas aminoglycosides decrease the levels of hla and alpha-toxin expression. In the present study we investigated the effects of subinhibitory concentrations of amoxicillin, gentamicin, and moxifloxacin on hla and alpha-toxin expression and total hemolysis of S. aureus strain 8325-4, a high-level alpha-toxin producer, and its alpha-toxin-negative mutant, DU 1090, in vitro and in a rat model of chronic S. aureus infection. The levels of expression of hla and alpha-toxin and total hemolysis did not differ significantly when amoxicillin, gentamicin, or moxifloxacin was added to cultures of S. aureus strain 8325-4. In vivo, strain 8325-4 induced a significantly increased level of hemolysis in infected pouches compared to that in uninfected control pouches, but the hemolysis was reduced to control levels by treatment with doses of amoxicillin, gentamicin, or moxifloxacin that reduced bacterial numbers by 2 orders of magnitude. Additionally, the effects of subinhibitory concentrations of the three antibiotics on total hemolysis of four methicillin-resistant S. aureus and three methicillin-sensitive S. aureus (MSSA) clinical isolates were assessed in vitro. A significant increase in total hemolysis was observed for only one MSSA strain when it was treated with amoxicillin but not when it was treated with moxifloxacin or gentamicin. When purified alpha-toxin was incubated with purified human neutrophil elastase, alpha-toxin was cleaved nearly completely. The results suggest that the penicillin-induced increases in S. aureus alpha-toxin expression are strain dependent, that reduction of bacterial numbers in vivo counteracts this phenomenon effectively, and finally, that in localized S. aureus infections alpha-toxin activity is controlled by neutrophil elastase.

The aim of this study was to rapidly identify bacteria of the family of Enterobacteriaceae using fluorescent in situ hybridization (FISH). A comparative sequence analysis was carried out and a 23S rRNA signature sequence for Enterobacteriaceae was identified. A 23S rRNA-targeted oligonucleotide probe (EBAC1790) was constructed and subsequently tested against 40 reference strains. Nearly all of the Enterobacteriaceae used in this study yielded positive results with EBAC1790, except for Edwardsiella tarda (ATCC 15947). None of the non-Enterobacteriaceae reference strains gave positive signals with the probe. The possibility of a rapid detection of Enterobacteriaceae in groundwater was demonstrated using colony hybridization.

The molecular epidemiology of Staphylococcus aureus nasal commensal strains and community-acquired infecting strains was assessed by comparison of prevalence, persistence, transmission rate, and clonal distribution of S. aureus in families with and without cystic fibrosis (CF) patients. Isolates were typed by pulsed-field gel electrophoresis. CF patients without antibiotic treatment had a significantly higher nasal prevalence (66%) of S. aureus than did treated patients (29%; P<.001) or healthy controls (32%; P<.001), suggesting that persons with CF have a higher susceptibility to this organism. Strain transmission was frequent within both CF (55%) and non-CF (62%) families. After 3 and 19 months, 57% and 21%, respectively, of all persons still harbored the same S. aureus strain. Most of the isolates (78%) belonged to 8 of 38 genome types common in CF patients and in healthy persons. The predominant occurrence of a limited number of S. aureus clones within the community suggests evolutionary mechanisms for the selection of certain strains without an obvious association with disease.

Trefoil factor family domain peptides (TFF) are thought to be involved in mucosal epithelial restitution and wound healing of the gastrointestinal tract and are up-regulated in ulceration and in a variety of solid tumours. It was hypothesized that TFFs are also expressed on mucosal surfaces of the human respiratory tract. Lung tissue, nasal polyps, and sputum samples from seven patients with cystic fibrosis (CF), two with chronic and acute bronchitis, and non-dysplastic material from two cases of bronchial adenocarcinoma were analysed for TFF expression by immunohistochemistry, immunofluorescence, western blot and RT-PCR. Expression of TFF1 and TFF3 was observed in material from all patients. TFFs were localized in goblet and ciliated cells, as well as in some submucosal cells of tracheobronchial tissues and nasal polyps from normal and CF individuals. In sputa of patients with CF and with chronic or acute bronchitis, TFF1 and TFF3 were detected by western blotting. Freshly cultivated nasal epithelial cells transcribed and secreted TFFs and mucins, whereas nasal cells cultivated for 6 weeks still expressed mucins, but not TFFs. Secreted TFFs and mucins also bound to the surface of Staphylococcus aureus in infected CF airways. In conclusion, TFF1 and TFF3 are expressed and secreted in normal and inflamed airways. The association of TFFs with bacteria may contribute to the anti-microbial mucociliary defence system., (Copyright 2000 John Wiley & Sons, Ltd.)

European countries follow different procedures to monitor the quality of the water of swimming pools open to the public: some use generally accepted technical standards, some officially recommended guidelines, some rules or regulations by local authorities and some have national laws or regulations. These agree insofar as in every country the water of swimming pools must be disinfected. The microbiological limits are to a certain extent identical with drinking water threshold values, e.g., no faecal coliforms must be present in 100 ml. Other microorganisms as for instance legionellae, staphylococci or Pseudomonas aeruginosa ar not uniformly considered. In all countries the water must be disinfected by chlorination. Big differences exist, however, in respect of the maximum admissible concentrations of free or total chlorine, haloforms and organic carbons. With regard to the common goals, harmonization of the regulations appears possible.

Critically ill patients often develop symptoms of sepsis and therefore require microbiological tests for bacteremia that use conventional blood culture (BC) techniques. However, since these patients frequently receive early empirical antibiotic therapy before diagnostic procedures are completed, examination by BC can return false-negative results. We therefore hypothesized that PCR could improve the rate of detection of microbial pathogens over that of BC. To test this hypothesis, male Wistar rats were challenged intravenously with 10(6) CFU of Escherichia coli. Blood was then taken at several time points for detection of E. coli by BC and by PCR with E. coli-specific primers derived from the uidA gene, encoding beta-glucuronidase. In further experiments, cefotaxime (100 or 50 mg/kg of body weight) was administered intravenously to rats 10 min after E. coli challenge. Without this chemotherapy, the E. coli detection rate decreased at 15 min and at 210 min after challenge from 100% to 62% of the animals with PCR and from 100% to 54% of the animals with BC (P, >0.05). Chemotherapy decreased the E. coli detection rate at 25 min and at 55 min after challenge from 100% to 50% with PCR and from 100% to 0% with BC (P, <0.05). Thus, at clinically relevant serum antibiotic levels, PCR affords a significantly higher detection rate than BC in this rat model. The results suggest that PCR could be a useful adjunct tool supplementing conventional BC techniques in diagnosing bacteremia.

The exposure of employees to airborne dust and microorganisms was assessed in a waste processing plant established to recover reusable materials from unsorted domestic and industrial waste. Exposure criteria considered relevant were the quantity of the individual size-selected particle fractions, the morphological properties of the particles, their heavy metal content, and the degree of their contamination with various microorganisms and mold. In addition, separate microbiological analyses to determine potential pathogen concentrations in the air were made. The highest concentrations of total and fine dust were measured in the waste delivery area. A close correlation between the frequency of deliveries and the level of dust exposure was observed. In this area, fine dust concentrations exceeded the threshold limit value of 6 mg/m3 repeatedly for shorter periods. The average fine dust concentration during an entire work-shift, however, was considerably lower than this value. Particles with an aerodynamic diameter of 2 to 7 microns predominated both in the waste delivery and the processing areas. Fibrous dust particles were present in smaller numbers than spherical particles and consisted mainly of organic materials. Natural and artificial inorganic fibers were found only occasionally. The concentrations of lead, cadmium, nickel and mercury were considerably lower than the corresponding MAK and TRK values, and were--with the exception of lead--in the range of the respective metal concentrations in the atmosphere of urban areas. Microscopical examinations of used protective masks (protection category P2) revealed that dust particles were deposited even on the inner side of the masks. Most of the particles on this side were very small and carried nickel or titanium. Microorganism concentrations measured in air from the highly dust-exposed areas of the plant showed values up to 6.9 x 10(5) cfu/m3, with a mold content of 6.6 x 10(4) cfu/m3. Approximately 90% of the microorganisms were deposited on particles of the fine dust fraction (particle size < 7 microns), and more than 50% contaminated particles with an aerodynamic diameter of 2 to 4.7 microns. In the compost facility, mold concentrations of up to 8.4 x 10(5) cfu/m3 were measured. In contrast, the level of microbial contamination in the filtered air from the compost facility did not exceed the concentration measured in air outside the plant. The data which were obtained during the winter months are probably at the lower end of the average exposure range over the entire year. In regard to exposure assessment, it should be mentioned that particles with a size of 4 to 7 microns are not really "inert" particles, since they are preferential carriers for heavy metals and microorganisms. More studies in the future should be performed to establish, whether the level of exposure to microorganisms can be estimated indirectly by the determination of dust exposure.

Genotyping and antibiotic susceptibility testing were used to analyze Pseudomonas aeruginosa and Burkholderia cepacia strains from sink drain from 14 pediatric patients with cystic fibrosis (CF) and from hospital personnel as part of a 4 week prospective study of strain transmission in a pediatric ward. A total of 87.5% of all washbasin drains were contaminated with P. aeruginosa [10(2) to 10(5) colony forming units (CFU)/ml sink fluid], whereas B. cepacia was found only once in a sink drain. From the eight CF patients already infected with P. aeruginosa upon entering the ward, we isolated six genotypes that were identical with strains found in sink drains of the ward. Four of the 16 members of the personnel had one positive P. aeruginosa hand culture. B. cepacia was never found in patients or on personnel hands. Hand washing in contaminated sinks (> or = 10(3) CFU/ml) led to positive P. aeruginosa or B. cepacia hand cultures. P. aeruginosa or B. cepacia embedded in sputum were transmissable by hand shaking for up to 180 min, whereas both pathogens suspended in physiological saline were transmissable to other hands only up to 30 min. Genotyping of P. aeruginosa revealed strain transmission from CF patients or the environment to other patients or the personnel, as well as one transmission from the environment to a CF patient. The ability of CF sputum to prolong survival of P. aeruginosa and B. cepacia may be important for strain transmission. The results suggest that improved hygienic measures are required to prevent routes of bacterial transmission via the hands and sink drains.

Although the diagnosis of cryptosporidiosis in diarrheic patients is relatively simple, as large amounts of oocysts are usually shed, environmental samples can contain only few oocysts which have a comparatively high epidemiological relevance. Very sensitive detection methods are therefore requested in environmental hygiene. Additionally these methods should allow a statement about the viability of the detected organisms. The combination of a DNA-digest and a viability assay followed by a PCR might reveal a very promising method. A DNA-digest destroys free DNA in the sample. In the following excystation protocol only viable sporozoites excyst. A PCR carried out now gives definitive proof of viable oocysts. Dead sporozoites within intact oocyst-walls are not detected.

Viruses can pass disinfection steps of water treatment plants without being inactivated. Investigations during the last 15 years revealed repeatedly the presence of enteric viruses in finished water meeting standards for coliform bacteria. Methods for the detection of viruses in water which implicate their growth on specific cell cultures are very time consuming and do not cover many viral species. Molecular detection methods including PCR techniques may help in the development of alternate methods for virus detection particularly in drinking water which usually does not contain PCR inhibiting factors.

The microbicidal effect of ozone in air was tested at concentrations between 50 and 600 micrograms/m3 against the species: Staphylococcus epidermidis, Micrococcus luteus, Arthrobacter citreus, Bacillus subtilis (veg.), Escherichia coli, Salmonella typhimurium, Serratia marcescens, Pseudomonas fluorescens and Candida albicans. The microorganisms were exposed on membrane filters at 60-75% relative humidity and 21.5-22.5 degrees C. After exposure times between 1 min and 60 min, the filters were incubated on appropriate agar media. The effect of ozone was determined by comparing the number of colonies on exposed filters to the number on nonexposed filters. The die-off curves (colony count against time) proved not to be rectilinear, but to become steeper with increasing time of exposure. Furthermore, the velocity of reduction increased more than proportional with increasing concentration of ozone. Therefore, the bacterial decay seems not to follow first order reaction kinetics. The values presented for k (constant of the velocity of die-off) and D (decimal reduction time) are valid only for narrow ranges of the initial part of the exposure. Concentrations of 50 to 100 micrograms (0)3/m3 for 1 h resulted only in little reduction, whereas 500 to 600 micrograms/m3 for one hour led to 99% reduction in all bacterial species tested. The gram-positive species seemed to be more sensitive than the gram-negative species, C. albicans proved to be more resistant than the bacteria.

Physiotherapy involves manifold measures that are partly not clearly separated from other methods of therapy. In most cases the skin or mucosa are not injured so that the danger of infectious complications is relatively low. On the other hand, patients with severe underlying diseases which are problematic from the aspect of hygiene in connection with infections, may have to be treated (for example, intensive-care patients, patients with decubital ulcers etc.) In such patients physiotherapy must comply with hygienic precautions that are employed with other diseases and treatments to prevent the transfer of pathogens. Special rules govern the composition of the water and the servicing of equipment used in hydrotherapy (German DIN standard specification No. 1964). Guidelines for the water used in municipal swimming pools and baths are in preparation. Other rules to be observed concern the recognition, treatment and prevention of nosocomial infections. In addition, every establishment must set up definite rules for regular measures to prevent infections and to monitor these measures, especially with regard to cleaning and disinfecting.

Pseudomonas aeruginosa was isolated from sinks of washing basins, showers, toilets and bathtubs, from the personnel and patients of a mixed infectious disease ward in a German children's hospital during a prospective 4-week epidemiological study. 81% of all sinks were contaminated with P. aeruginosa strains. Upon entering the hospital, all personnel hand cultures were P. aeruginosa-negative. However, during duty, 42.5% of the personnel members carried different P. aeruginosa strains on their hands. Detection of P. aeruginosa strains in sinks preceding the isolation of identical genotypes from personnel hands suggested a transmission route from sinks to hands. Opening of water taps generated aerosols containing P. aeruginosa sink organisms which contaminated hands during hand washing. Survival times of various P. aeruginosa strains in aerosols was dependent on strain characteristics, light and humidity, and t 1/2 differed between 3-76 min. Heating of washing basin sinks to 70 degrees C with a new, safe and inexpensive device inhibited bacterial growth in sinks, generation of P. aeruginosa aerosols, and resulted in hand cultures negative for P. aeruginosa after washing.

It can be shown, that under certain conditions commercially available indicators with Bacillus stearothermophilus and packages of native spores from soil prepared according to DIN 58 946/4 react differently to treatment in a lab-type steam sterilizer. The differences were most evident when incomplete evacuation of air had to be supposed. These results lead to the conclusion that some bioindicators are not able to show the inefficient function of steam sterilizers caused by local residuals of air. This may be caused by the properties of the selected strain, by the conditions of growth and preparation of the spores and by the culture medium used after exposition. The results of our experiments as well as the resistance of mesophilic spore forming bacilli against dry heat described by other authors make it necessary to test the resistance of bioindicators for steam sterilization not only against steam according to DIN 58946/4 but also against dry heat or mixtures of steam and air.

In a new hospital building, cold and warm water systems were examined for microbiological parameters before opening. All of the 35 sampling sites showed elevated colony counts, i.e. greater than 100 cfu/ml. 11 of these contained Legionella species at various times. While Escherichia coli, coliform bacteria and Pseudomonas aeruginosa could not be found, Legionella longbeachae serogroup 1 + 2 was identified in 13 samples. Only one sample contained Legionella pneumophila serogroup 3. Legionella species were detected using a commercial gene probe assay and culture techniques. The gene probe method proved to be superior to the culture techniques insofar as significantly positive results were obtained more frequently, and evidence for the presence of Legionella of different species and serogroups could be obtained with a single procedure. The gene probe method appears to be a suitable screening method for the detection of Legionella species.

The mixture of substances in the photochemical smog could be detected by different reduction rates of exposed bacteria. Beside ozone other products of the ozone/olefine-reaction could reduce the survival of exposed bacteria. For Staph. epidermidis a toxic influence from the reaction products could be found only after UV-irradiation. The main components were aldehydes, hydrocarbons, radicals, peroxiradicals and radicaloxides. For peroxiacetylnitrate (PAN) no bactericidal effect could be found for bacteria adsorbed on membrane filters in concentrations of 300 ppb in the smog (UV-irradiation was put off for two hours) and even in concentrations of 1000 ppb prepared by gaschromatography. The influence on lipopolysaccharide (lps) defective mutants of Salmonella minnesota showed the protection of the lps-layer against e.g. relative humidity and ozone (500 ppb), but no specific protection against smog components.

84 Pseudomonas aeruginosa strains from 29 paraplegic patients with urinary tract infections (UTI) and from the water reservoirs of specialized wards in two German hospitals were typed using a P. aeruginosa-specific DNA probe. P. aeruginosa strains were present in 51% of all accessible water reservoirs, including sinks of wash-basins and toilets in the wards. 14 of the 29 patients with UTI (48%) were infected by P. aeruginosa strains which were also isolated from these sources. Groups of up to four patients were infected by single strains. Some of the strains persisted in the wards and were isolated from the water reservoirs five to eight months after causing UTI. 89.5% of the investigated water samples yielded P. aeruginosa strains which were identical with strains from up to nine other sites. The wide distribution of single P. aeruginosa genotypes in the ward, the isolation of strains causing UTI from rooms inaccessible to the patients, and the outbreak of UTI caused by single, identical P. aeruginosa strains in groups of patients within short time periods, suggest that the strains are distributed by the personnel rather than by the patients who for the most part are immobile.