Martin Exner

Microbial Load of Drinking Water Reservoir Tributaries during Extreme Rainfall and Runoff

ABSTRACT Hygienic and microbiological examinations of watercourses are usually not carried out during heavy rainfall and runoff events. After rainfall or snowmelt, there are often massive increases in turbidity in flooding creeks in mountain ranges, which are frequently interpreted as an indication of microbial contamination. The aim of this study was to quantify the microbial loads of watercourses during such runoff events and to compare these loads with loads occurring during regular conditions. In a 14-month monitoring period we investigated the microbial loads of three tributaries of different drinking water reservoirs. A total of 99 water samples were taken under different runoff conditions and analyzed to determine physical, chemical, bacterial, and parasitic parameters. Thirty-two water samples were considered event samples during nine measuring series. The criteria for events, based on duration and intensity of precipitation, water depth gauge measurements, and dynamics, had been fixed before the investigation for each creek individually. Of the physical and chemical parameters examined, only the turbidity, pH, and nitrate values differed clearly from the values obtained for regular samples. Most of the bacteriological parameters investigated (colony, Escherichia coli, coliform, fecal streptococcal, and Clostridium perfringens counts) increased considerably during extreme runoff events. If relevant sources of parasitic contamination occurred in catchment areas, the concentrations of Giardia and Cryptosporidium rose significantly during events. The results show that substantial shares of the total microbial loads in watercourses and in drinking water reservoirs result from rainfall and extreme runoff events. Consequently, regular samples are considered inadequate for representing the microbial contamination of watercourse systems. The procedures for raw water surveillance in the context of multiple-barrier protection and risk assessment ought to include sampling during extreme runoff situations.

Occurrence of Toxigenic Aspergillus versicolor Isolates and Sterigmatocystin in Carpet Dust from Damp Indoor Environments

ABSTRACT Over the past decade, there has been growing concern regarding the role of toxigenic fungi in damp indoor environments; however, there is still a lack of field investigations on exposure to mycotoxins. The goal of our pilot study was to quantify the proportion of toxigenic Aspergillus versicolor isolates in native carpet dust from damp dwellings with mold problems and to determine whether sterigmatocystin can be detected in this matrix. Carpet dust samples (n = 11) contained from <2.5 × 101 to 3.6 × 105 (median, 3.1 × 104) A. versicolor CFU/g of dust, and the median proportion of A. versicolor from total culturable fungi was 18%. Based on thin-layer chromatography detection of sterigmatocystin, 49 of 50 A. versicolor isolates (98%) were found to be toxigenic in vitro. By using high-performance liquid chromatography-electrospray ionization tandem mass spectrometry, sterigmatocystin could be detected in low concentrations (2 to 4 ng/g of dust) in 2 of 11 native carpet dust samples. From this preliminary study, we conclude that most strains of A. versicolor isolated from carpet dust are able to produce sterigmatocystin in vitro and that sterigmatocystin may occasionally occur in carpet dust from damp indoor environments. Further research and systematic field investigation are needed to confirm our results and to provide an understanding of the health implications of mycotoxins in indoor environments.

Outbreaks of Serratia marcescens in neonatal and pediatric intensive care units: clinical aspects, risk factors and management.

The following recommendations are derived from a systematic analysis of 34 Serratia marcescens outbreaks described in 27 publications from neonatal and pediatric intensive care units (NICU, PICU), in which genotyping methods were used to confirm or exclude clonality. The clinical observation of two or more temporally related cases of nosocomial S. marcescens infection should raise the suspicion of an outbreak, particularly in the NICU or PICU setting. Since colonized or infected patients represent the most important reservoir for cross transmission, hygienic barrier precautions (contact isolation/cohortation, the use of gloves and gowns in addition to strictly performed hand disinfection, enhanced environmental disinfection) should immediately be implemented and staff education given. Well-planned sampling of potential environmental sources should only be performed when these supervised barrier precautions do not result in containment of the outbreak. The current strategy of empiric antibiotic treatment should be reevaluated by a medical microbiologist or an infectious disease specialist. Empiric treatment of colonized children should use combination therapy informed by in vitro susceptibility data; in this context the high propensity of S. marcescens to cause meningitis and intracerebral abscess formation should be considered. In vitro susceptibility patterns do not reliably prove or exclude the clonality of the outbreak isolate. Genotyping of the isolates by pulse-field gel electrophoresis or PCR-based methods should be performed, but any interventions to interrupt further nosocomial spread should be carried out without waiting for the results.

Long-term effects of disinfectants on the community composition of drinking water biofilms

Numerous investigations have demonstrated efficiencies of different disinfection methods, but until now only little is known about long-term effects on community compositions of drinking water biofilms. Changes in the community structure, especially regrowth of hygienically relevant microorganisms could be critical for the drinking water quality. In this study the long-term effect of disinfection methods on biofilm communities in drinking water systems was analysed. Old drinking water biofilms grown in silicone tubes were exposed to different preparations of disinfectants (free chlorine, chlorine dioxide, hydrogen peroxide combined with fruit acid, silver and silver with peracetic acid, respectively) and subsequently further exposed in the original drinking water. The comparison of the treated and regrown biofilm populations with untreated ones by the DNA-fingerprinting method denaturing gradient gel electrophoresis (DGGE) revealed a considerable population shift caused by the disinfectants. The disinfection methods induced a selection pressure on the biofilm populations depending on the composition and concentrations. The similarities between the treated and untreated biofilms were generally low. Compared to preparations with peracetic acid the disinfection with hydrogen peroxide and silver resulted in higher similarities of the treated and untreated biofilms, but the microbial diversity increased. It can be concluded that the disinfectants have a major impact on the drinking water biofilm communities and that possibly the intervention selects persisters and microorganisms, which can live on the residuals of the dead biofilm cells. For the evaluation of the efficiency of disinfection methods in drinking water installations it is necessary not only to consider reduction of certain bacteria but also to pay attention to the biofilm community.

Rotavirus infections in paediatric oncology patients: A matched-pairs analysis

Objective. To conduct a systematic investigation of the clinical relevance of rotavirus infection in the setting of paediatric cancer patients receiving intensive chemotherapy. Material and methods. Twenty-eight paediatric cancer patients with positive rotavirus antigen tests were eligible for a retrospective case-control study (January 1995–December 2004). Rota-positive patients were compared with 28 rota-negative patients matched for age, underlying disease and chemotherapy. The National Cancer Institute Common Toxicity Criteria were used to determine clinical severity. Results. Median duration of rota-related symptoms (diarrhoea, fever and vomiting) was 7 days (range 4–34 days; 75th percentile 9 days). Median duration of viral shedding was 17 days (4–73 days; 75th percentile 39.5 days). The rota infection was nosocomially acquired in 19 patients (68%). The proportions of patients with diarrhoea ≥NCI II, fever >39°C, clinically relevant dehydration, metabolic acidosis, mucositis and neutropenia were significantly higher in rota-positive patients. Rota-positive patients tended to have a prolonged period of hospitalization (median 8 versus 4 days; p=0.008). A higher proportion of rota-positive patients had to receive parenteral nutrition and tube feeding (p<0.001). Conclusions. Rotavirus is a clinically relevant but preventable pathogen in paediatric cancer patients, since many cases seem to be nosocomial in origin. Rapid microbiological testing and contact precautions should be strictly applied to any symptomatic patient and to their immediate contacts. Prolonged viral shedding in immunocompromised paediatric patients necessitates repeated testing in order to determine the duration of isolation.

Surveillance for nosocomial infections and fever of unknown origin among adult hematology-oncology patients.

OBJECTIVE To determine the incidence of nosocomial infections (NIs) and fever of unknown origin among adult hematology-oncology patients. DESIGN Prospective surveillance study. SETTING The 18-bed hematology-oncology unit at the University Hospital Bonn, Bonn, Germany. PATIENTS All hematology-oncology patients admitted during a total of 8 months in 1998 and 1999. METHODS Standardized surveillance system based on the Centers for Disease Control and Preventions National Nosocomial Infections Surveillance system. Rates of NI and fever of unknown origin were calculated for patient-days and patient-days at risk (ie, days with neutropenia of < 500/mm3 or leukopenia of < 1,000/mm3). RESULTS Of 116 patients hospitalized for a total of 4,002 days (172 admissions; mean length of stay, 25.2 days), 32 (27.6%) had a total of 44 documented NIs (19 bloodstream infections, 15 pneumonias, 7 urinary tract infections, and 3 others). In addition, 33 fevers of unknown origin were documented in 28 patients. No patient had thrush while receiving antifungal prophylaxis. The overall rates for NI and fever of unknown origin were 11.0 and 8.2 per 1,000 patient-days (25.3 and 15.4 per 1,000 patient-days at risk), respectively. The risks for NI and fever of unknown origin were significantly higher during neutropenic days, with 34 (77.3%) of the 44 NIs and 22 (66.7%) of the 33 fevers of unknown origin occurring during 1,345 patient-days at risk. CONCLUSIONS Prospective surveillance for NIs on hematology-oncology units should include fever of unknown origin as the single most common and clinically important entity. For a meaningful comparison of surveillance data for hematology-oncology patients, the reported infection rates should include rates based on days with neutropenia, for which days with leukopenia could serve as a surrogate marker under routine conditions.

Detection of Helicobacter pylori in biofilms by real-time PCR

Helicobacter pylori is a cause of peptic ulcer disease and a causative agent of gastric cancer. Currently, a possible waterborne route of transmission or a possible survival in drinking water biofilms is discussed. H. pylori, like many other bacterial strains, has the ability to enter the viable but nonculturable state (vbnc) in case of unfavorable conditions. Therefore it is necessary to develop new analysis tools for vbnc bacteria. We established a fast and reliable method to detect H. pylori in drinking water biofilms by quantitative real-time PCR which makes it redundant to use difficult cultivation methods for nonculturable bacteria. With this method it was possible to identify water biofilms as a niche for H. pylori. The real-time PCR analysis targets the ureA subunit of the Helicobacter pylori urea gene which showed high specificity and sensitivity. The quantitative real-time PCR was used to detect H. pylori in biofilms of different age, unspiked and spiked with predetermined levels of cells. The drinking water biofilms were generated in a silicone-tube model. The DNA-sequences for probe and primers showed no cross-homologies to other related bacteria and it was possible to detect less than 10 genomic units of H. pylori. This novel method is a useful tool for a fast screening of drinking water biofilms for H. pylori. The results suggest that drinking water biofilms may act as a reservoir for H. pylori which raises new concerns about the role of biofilms as vectors for pathogens like Helicobacter pylori.

Impact of portable air filtration units on exposure of haematology–oncology patients to airborne Aspergillus fumigatus spores under field conditions

We undertook a one-year study to investigate the impact of the NSA model 7100A/B portable air filtration unit on exposure of haematology-oncology patients to airborne Aspergillus fumigatus spores under field conditions. Weekly measurements for airborne A. fumigatus were conducted in indoor and outdoor air, and surveillance for invasive aspergillosis was based on a combination of ward liaison, targeted chart review and consultation with the medical staff. The mean indoor A. fumigatus counts (8.1 cfu/m3; range, <0.8 to 42 cfu/m3) reflected the fungal load of outdoor air (9.4 cfu/m3; range, <0.8 to 50 cfu/m3), and were reduced by only about one third in rooms with portable air filtration units (5.3 cfu/m3; range, <0.8 to 41 cfu/m3). During the study period, a total of five cases (incidence density, 0.8 per 1000 patient-days) of invasive aspergillosis (one proven case, four suspected cases; case fatality rate 40%) were recorded. None of these five patients was allocated to a room with portable air filtration unit, however, the difference between incidence densities in rooms with and without portable air filtration units was non-significant (Fishers exact test, P=0.33). Due to the noise level and thermal discomfort, patient compliance with the air filtration units was poor. We conclude that under field conditions this air filtration unit cannot be recommended for prevention of invasive aspergillosis in neutropenic haematology-oncology patients.

Air sampling of Aspergillus fumigatus and other thermotolerant fungi: Comparative performance of the Sartorius MD8 airport and the Merck MAS-100 portable bioaerosol sampler

The purpose of our field study was to compare the performance of two portable bioaerosol samplers (Sartorius MD8 airport, and Merck MAS-100) for sampling Aspergillus fumigatus and other airborne thermotolerant fungi. From October 2001 to November 2001, a total of 336 samples were analyzed at 12 sampling days. During the sampling period fungal plate counts ranged from <1 to 300 CFU/m(3) for total thermotolerant fungi and from <1 to 76 CFU/m(3) for A. fumigatus. As compared to the MD8, the relative recovery of the MAS 100 was 0.96 for total thermotolerant fungi and 0.84 for A. fumigatus. We found a good correlation (Pearsons r=0.94 for single, 0.95 for the mean of two, and 0.96 for the mean of three sequential samples) between both portable bioaerosol samplers. The spectrum of thermotolerat fungal genera and Aspergillus species showed only minor differences. We conclude that under the given conditions the results of both samplers are approximately comparable.

A Geographical Information System (CIS) as a tool for microbial risk assessment in catchment areas of drinking water reservoirs

The main tributaries of three drinking water reservoirs of Northrhine-Westfalia (Germany) were monitored within a 14-month period mainly for bacterial and parasitic contamination. In this context a detailed geo-ecological characterisation within the differing catchment areas was carried out to reveal a reliable informational basis for tracing back the origin of microbial loads present in the watercourses. To realise a microbial risk assessing geo-ecological information system (MRA-GIS), a Geographical Information System (GIS) has been implemented for the study areas. The results of the microbiological investigations of the watercourses showed an input of pathogens into all three of the tributaries. It could be demonstrated that the use of MRA-GIS database and some GIS-techniques substantially support the spatial analysis of the microbial contamination patterns. From the hygienic point of view, it is of the utmost importance to protect catchment areas of surface water reservoirs from microbial contamination stemming from human activities and animal sources. This constitutes essential part of the multi-barrier concept which stresses the importance of reducing diffuse and point pollution in catchment areas of water resources intended for human consumption. MRA-GIS proves to be helpful to manage multi-barrier water protection in catchment areas and ideally assists the application of the HACCP concept on drinking water production.