[Infections on catheters in hemodialysis: Temporal fluctuations of the infectious risk]. / Infections sur cathéters d'hémodialyse : variations du risque en fonction de la durée de cathétérisme.

BACKGROUND: International guidelines recommend to limit the long-term use of central-veinous catheters in patients undergoing hemodialysis, because they expose the patient to a higher infectious risk than the fistulas. However, for some patients with comorbidity, switching to a permanent vascular access is not possible. In such case, the catheter is used for a longer period. It seems therefore important to study the influence of a prolonged duration of catheterization on infectious complications. The temporal fluctuation profile of the infectious risk is poorly studied in the literature and the results published may be contradictory. METHODS: This multicentric prospective study included 1053 incident tunneled catheters. Multivariate logistic regression was used to identify significant risk factors of infection. An infection-free survival analysis was performed afterwards to estimate the variation of the instantaneous infectious risk during catheterization. RESULTS: The major risks factors of infections on tunneled catheters were: previous Staphylococcus aureus infection (aOR=1.95 [1.16-3.27]; P=0.012), diabetes (aOR=1.67 [1.16-2.41]; P=0.006), and long duration of catheterization (0-3months vs.≥24months: aOR=2.42 [1.34-4.36]; P=0.003). The survival analysis showed a higher risk of infections of tunneled catheters during the first months after placement. Risk declines over time. CONCLUSIONS: The fluctuation profile of the infectious risk show that preventive precautions should target the first months of catheterization.

Simplified protocol for evaluating the genotoxic risk of hospital wastewater.

To evaluate the genotoxicity of hospital wastewater, we drew up a simplified protocol based on two well-known tests: the SOS chromotest and the Ames fluctuation test. Three concentrations of wastewater samples were directly tested without extraction or concentration. By fixing three significance levels in genotoxicity response for each test, we could classify the samples in five categories ranging from nongenotoxic to highly genotoxic. This simplified classification thus constitutes an invaluable help in making the nonscientist public aware of the genotoxic risk of hospital wastewater and can be applied in a screening approach to chemicals in the environment.

Hospital wastewater genotoxicity.

Hospitals represent an incontestable release source of many chemicals compounds in their wastewaters, and which may have an impact on the environment and human health. Indeed, some of the substances found in wastewaters are genotoxic and are suspected to be a possible cause of the cancers observed in the last decades. To study the toxicity and the risk associated with these releases biological tests, such as genotoxicity tests, can be used. An evaluation of the genotoxic potential of the wastewaters from a university hospital was performed with the SOS chromotest and the Salmonella fluctuation test. The samples were taken for six 1-week periods between May 2001 and April 2003. Out of a total of 38 samples tested, 31 were positive in at least one assay (82%). Distribution, proportion and intensity of the genotoxic response were different among the six sampling periods. The two genotoxicity tests had different sensitivities. It must be emphasized that whatever the sampling period, Monday samples were always genotoxic in at least one assay. This work shows that this hospital wastewaters samples are very often genotoxic, the response intensity being inflected by rain levels. Efforts must be undertaken by hospitals to integrate the knowledge and the control of their wastewaters in infection and environmental control programs.

Efficacy of two wastewater treatment plants in removing genotoxins.

The genotoxic potential of influents and effluents of two different wastewater treatment plants (WTP-A and WTP-B) located in the Rouen, France, area was evaluated by the SOS chromotest without metabolic activation (on Escherichia coli PQ37) and the Ames fluctuation test (on Salmonella typhimurium strains TA 98, 100, TA 102) with and without metabolic activation. The wastewater samples were taken during two 1-week periods in January and April 2003. The simultaneous use of the SOS chromotest and Ames fluctuation test allowed us to evaluate the efficacy of the wastewater treatment plants at removing genotoxins. Genotoxins were detected with the Ames test but not with the SOS chromotest. Out of a total of 24 influents tested (14 for WTP-A and 10 for WTP-B), almost all were genotoxic in at least one Ames test strain (71% for WTP-A and 100% for WTP-B). In contrast, all of the tested effluents were nongenotoxic. This work showed that the treatment process used in the 2 wastewater treatment plants studied (activated sludge) was able to remove the genotoxins detected in their influents. Nevertheless, studies could be undertaken to determine which step of the treatment process removes genotoxins and whether WTP sludge use could be a source of genotoxic contamination for humans and the environment.

Evaluation of industrial, hospital and domestic wastewater genotoxicity with the Salmonella fluctuation test and the SOS chromotest.

An evaluation of the genotoxic potential of different wastewaters collected in the Rouen area was performed with the SOS chromotest (on Escherichia coli PQ37) and the Salmonella fluctuation test on Salmonella typhimurium strains TA98, TA100 and TA102 with or without metabolic activation. The samples were taken during two 1-week periods, one in January and one in April 2003. Six sites were selected for wastewater sampling in order to allow a comparative study between an area of mixed discharge (industrial, hospital and domestic) and an area of primarily domestic discharge. Out of a total of 71 daytime samples tested, 46 (65%) were positive in at least one assay: 22 samples out of 33 in January (67%), and 24 samples out of 38 in April (63%). The two genotoxicity tests have different sensitivities. Indeed, the Salmonella fluctuation test allowed the detection of 56% of the samples as genotoxic in January (18 out of 33), and 63% in April (24 out of 38) while the SOS chromotest allowed the detection of 18% of the samples as genotoxic, whatever the sampling period. The samples collected in domestic wastewater are at least as genotoxic as the samples collected in mixed wastewater. The possible source of the detected genotoxicity (industrial, hospital or domestic) is discussed. The results of this study show that the different types of wastewaters present a genotoxic risk. Additional studies should be undertaken in the analytical field in order to try to identify and quantify the compounds responsible for the genotoxicity. This difficult task will be necessary in order to identify the sources of toxicants and thus to take preventive and/or curative measures to limit the toxicity of the wastewater.

Detection of hospital wastewater genotoxicity with the SOS chromotest and Ames fluctuation test.

The genotoxic potential of Rouen University Hospital wastewater was evaluated by the SOS chromotest (on Escherichia coli PQ37) and Ames fluctuation test on Salmonella typhimurium strains TA 98 and TA 100 without metabolic activation. The samples were taken during the hospital maximal activity period (8:00 a.m. to 6:00 p.m.) over three one-week periods of the year. The simultaneous use of SOS chromotest and Ames fluctuation test allows us to carry out a preliminary screening of the hospital wastewater and to gain some insight by which mechanism the genotoxic compounds act. Out of a total of 18 daytime unconcentrated samples tested, 10 (55%) are positive in at least one assay. The two tests have different sensitivity. Indeed, nine genotoxic samples (50%) are detected by the Ames test, and four (22%) by the SOS chromotest. Distribution and intensity of the genotoxic response are different at the three periods. In order to explain this phenomenon, the influence of the rain levels is discussed. This work showed that the hospital wastewater samples tested were overall genotoxic, the response intensity being inflected by the pluviometry. Efforts are now under way to try to identify one or several genotoxic compounds in order to take precautionary measures to limit their release in hospital wastewaters.

Glutaraldehyde in hospital wastewater.

Glutaraldehyde (GA) solutions are widely used in hospitals to disinfect reusable fiber-optic endoscopes. These solutions are dumped after use in the aquatic environment without any particular safety precautions. Taking into account the quantity of GA consumed daily and the released water volume, the predicted hospital wastewater concentration was estimated at 0.50 mg/L. To measure the real GA concentration present in hospital wastewater, we developed an analytical technique that is simple, sensitive, and reliable. This method consists of a water sample concentration and purification by solid phase extraction and then a spectrophotometric determination. This analytical method was used for a 1-week surveillance program at Rouen University Hospital (2,600 beds). The wastewater tested showed the presence of a concentrated peak approximately eight times higher than the predicted wastewater concentration. The environmental impact of GA release into the aquatic environment was then studied. A predicted no-effect concentration (PNEC) < 1 microg/L was calculated. In most situations the predicted environmental concentration (PEC) was found to be <0.5 microg/L taking into account the hospital wastewater dilution in its way to the sewage treatment plant and GA biodegradation. The PEC/PNEC ratio is then < 1, showing that this release are not expected to present a significant risk to the aquatic environment. However in situations of insufficient dilution or of major release, the PEC/PNEC ratio become > 1, and an environmental risk should be expected. An internal prevention program of the various hospital departments to assure GA rational use, and a release spreading would give an additional safety margin to consider GA as safe in terms of environmental risk.