Control of bacterial contamination in microfiltered water dispensers (MWDs) by disinfection.

Three microfiltered water dispensers (MWDs) for domestic use were bacteriologically monitored over a period of 1 year to evaluate their hygienic status and to compare the ability of two disinfectants (peracetic acid and hydrogen peroxide) to ensure adequate bacteriological quality of the dispensed water. To this end, two dispensers were purposely contaminated with a strain of Pseudomonas aeruginosa of environmental origin. A total of 324 samples of input and output water were analyzed. Heterotrophic plate count (HPC) bacteria at 22 degrees C and 36 degrees C, total coliforms (CT), Escherichia coli (EC), enterococci (ENT), P. aeruginosa and Staphylococcus aureus were enumerated. Throughout the study period, the supply water was always of excellent bacteriological quality. All water samples taken from the MWDs complied with the legal requirements for drinking water: CT, EC, ENT and S. aureus were all consistently absent. P. aeruginosa was never isolated from the uncontaminated dispenser. However, an increase in HPCs up to levels of 10(3)-10(4) cfu/mL was found in the dispensed water. Under the present operative conditions, hydrogen peroxide was seen to be more effective than peracetic acid in controlling bacterial contamination in the water circuits. Periodic disinfection with hydrogen peroxide made it possible to obtain water with HPC levels conforming to Italian regulations for drinking water (< or =100 cfu/mL) as well as to the levels recommended by the American Dental Association (ADA) (< or =200 cfu/mL). Furthermore, in the contaminated circuits, H(2)O(2) disinfection led to a reduction in the concentrations of P. aeruginosa to only a few colony forming units/100 mL or to a complete, albeit temporary, disappearance of the microorganism. In conclusion, hydrogen peroxide at 3% can be proposed as a suitable product for periodic disinfection of domestic MWDs, taking into consideration also its low cost and easy availability.

Comparative study on the efficiency of peracetic acid and chlorine dioxide at low doses in the disinfection of urban wastewaters.

A comparison was made between the efficiency of low doses of peracetic acid (PAA: 1.5 mg/l) and chlorine dioxide (ClO(2): 1.5 and 2.0 mg/l) in the disinfection of secondary effluents of a wastewater treatment plant. Peracetic acid was seen to be more active than chlorine dioxide and less influenced by the organic content of the waste. Both PAA and ClO(2) (2.0 mg/l) lead to a higher reduction in total and faecal coliforms and E. coli than in phages (somatic coliphages and F-specific RNA bacteriophages) and enterococci. Detection of faecal coliforms and E. coli should therefore be accompanied by a search for these more resistant microorganisms when assessing the conformity of wastewater for irrigation use, or for discharge into surface waters. Coliphages are also considered suitable indicators of the presence of enteric viruses. Although the application of low doses of both disinfectants offers advantages in terms of costs and produces not significant quantities of byproducts, it is not sufficient to obtain wastewater suitable for irrigation according to the Italian norms (E. coli < 10/100 ml in 80 % of samples and <100/100 ml in the remaining samples). Around 65 % of the samples, however, presented concentrations of E. coli lower than the limit of 5,000/100 ml established by Italian norms for discharge into surface waters.

Rapid and sensitive detection of MS2 coliphages in wastewater samples by quantitative reverse transcriptase PCR.

Coliphage MS2 is used in place of pathogens in many studies and is considered one of the indicators of pathogenetic viruses in wastewater. We developed a quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) assay to quantify MS2 coliphages in treated wastewater samples. The format used was SYBR Green. The assay included an internal control to disclose the presence of PCR-product inhibitors. The method had a wide dynamic range (8 logs) with a correlation coefficient of 0.999 and is capable of detecting as few as 4x10(2) genome equivalents/100 ml of wastewater sample. The method was validated by using artificially contaminated water samples. The validated method was then applied to naturally contaminated samples collected in a wastewater treatment plant and the results were compared with those obtained by a plaque assay. In comparison with the plaque assay the PCR-method yielded viral counts about 1.5 orders of magnitude higher. The entire detection method, including sample processing and real-time PCR amplification, was completed within 4 hours, making it a rapid single-day method.

Active surveillance of legionnaires disease during a prospective observational study of community- and hospital-acquired pneumonia.

A prospective surveillance study of legionnaires disease and an environmental survey of Legionella species were performed simultaneously in a general hospital. During a period of 3 years, 705 patients with pneumonia were screened with a Legionella urinary antigen test, and pneumonia was confirmed by culture and serological tests. Twelve cases of legionnaires disease were identified, none of which were hospital acquired, despite the fact that 60% of hospital water samples were contaminated with Legionella pneumophila at a concentration of more than 10(3) colony-forming units/L. The probable source of infection was identified for only 2 community-acquired cases. The results show that environmental contamination alone is not able to predict the risk of legionnaires disease. If no cases are present, monitoring of hospital water systems is of little significance; clinical surveillance is much more important.

Influence of material and tube size on DUWLs contamination in a pilot plant.

Numerous studies have shown that the water discharged from dental unit waterlines (DUWLs) contains high densities of bacteria, especially non-fermenting Gram negative bacteria. The aim of the present study was to investigate how the material (polyethylene-PE and polytetrafluorethylene-PTFE) and size (1.6 and 4.0 mm) of 4 waterlines in a pilot plant influence the level of contamination in the output water. The water contamination was assessed by analyzing the trend of the heterotrophic plate counts at 22 degrees C as a function of time and by testing for non-fermenting Gram negative bacteria. In all waterlines, the bacterial density increased exponentially during the first months and thereafter remained between 10(4) and 10(6) cfu/ml. However, the plate count at 22 degrees C was lower in the water from PTFE tubes and from larger size tubes. Comamonas acidovorans, Pseudomonas aeruginosa and Pseudomonas fluorescens were isolated. Pseudomonas aeruginosa, responsible for infections associated with dental practice, was never isolated in the output water from PTFE tubes. In order to control bacterial contamination the results suggest the use of waterlines made of PTFE on account of their ability to inhibit the colonization and growth of Pseudomonas aeruginosa.

Microbial contamination in dental unit waterlines: comparison between Er:YAG laser and turbine lines.

The investigation was carried out by evaluating the microbiological characteristics of the water before and after treatment with Er:YAG laser and turbine. The study was carried out in 2 dental surgeries. In both cases the laser and dental units were served by two independent circuits, fed by the same potable tap water. Samples were taken from the water supplying and the water leaving the turbine and laser before and after treatment on the same patient. Total heterotrophic plate count was measured at 36 degrees C and at 22 degrees C, and the presence of Staphylococcus species and non-fermenting Gram negative bacteria was investigated. Bacterial contamination was found within the circuit, especially in the laser device. Pseudomonas aeruginosa was detected in only 1 sample of supply water, in 11.1 % and in 19.4 % of the samples from the turbine and the laser respectively. No evidence of Staphylococcus aureus was found. The contamination of supply water was low, whereas that of the water leaving the handpieces of the 2 devices was high, especially in the laser. Attention should be paid to the control of the water leaving laser devices, given the increasingly wide use of such instruments in dental treatment exposed to risk of infection.

Compulsory and recommended vaccination in Italy: evaluation of coverage and non-compliance between 1998-2002 in Northern Italy.

BACKGROUND: Since vaccinations are an effective prevention tool for maintaining the health of society, the monitoring of immunization coverage allows us to identify areas where disease outbreaks are likely to occur, and possibly assist us in predicting future outbreaks. The aim of this study is the investigation of the coverage achieved for compulsory (diphtheria, tetanus, polio, hepatitis B,) and recommended (pertussis, Haemophilus influenzae, measles-mumps-rubella) vaccinations between 1998 and 2002 in the municipality of Bologna and the identification of the subjects not complying with compulsory and recommended vaccinations. METHODS: The statistics regarding vaccinal coverage were elaborated from the data supplied by the Bologna vaccinal registration system (1998-2000) and the IPV4 program (2001-2002). To calculate the coverage for compulsory vaccinations and cases of non-compliance reference was made to the protocol drawn up by the Emilia Romagna Regional Administration. The reasons for non-compliance were divided into various categories RESULTS: In Bologna the levels of immunization for the four compulsory vaccinations are satisfactory: over 95% children completed the vaccinal cycle, receiving the booster for anti-polio foreseen in their 3rd year and for anti-diphtheria, tetanus, pertussis at 6 years. The frequency of subjects with total non-compliance (i.e. those who have not begun any compulsory vaccinations by the age of one year) is generally higher in Bologna than in the region, with a slight increase in 2002 (2.52% and 1.06% in the city and the region respectively). The frequency of the anti-measles vaccination is higher than that of mumps and rubella, which means that the single vaccine, as opposed to the combined MMR (measles-mumps-rubella) was still being used in the period in question. The most common reason for non compliance is objection of parents and is probably due to reduction of certain diseases or anxiety about the possible risks. CONCLUSION: In Bologna the frequency of children aged 12 and 24 months who have achieved compulsory vaccination varied, in 2002, between 95% and 98%. As regards recommended vaccinations the percentage of coverage against Haemophilus influenzae is 93.3%, while the levels for measles, mumps and pertussis range from 84% to approx. 92%. Although these percentages are higher if compared to those obtained by other Italian regions, every effort should be made to strengthen the aspects that lead to a successful vaccinal strategy.

Quality of Drinking Water Treated at Point of Use in Residential Healthcare Facilities for the Elderly.

Municipal tap water is increasingly treated at the point of use (POU) to improve the acceptability and palatability of its taste. The aim of this study was to assess the bacteriologic and nutritional characteristics of tap water treated at the point of use in residential healthcare facilities for the elderly. Two types of POU devices were used: microfiltered water dispensers (MWDs) and reverse-osmosis water dispensers (ROWDs). All samples of water entering the devices and leaving them were tested for the bacteriological parameters set by Italian regulations for drinking water and for opportunistic pathogens associated with various infections in healthcare settings; in addition, the degree of mineralization of the water was assessed. The results revealed widespread bacterial contamination in the POU treatment devices, particularly from potentially pathogenic species. As expected, the use of ROWDs led to a decrease in the saline content of the water. In conclusion, the use of POU treatment in healthcare facilities for the elderly can be considered advisable only if the devices are constantly and carefully maintained.

Detection of Escherichia coli O157 in bovine meat products in northern Italy.

Tests for Escherichia coli and E. coli O157 were carried out on meat samples collected from randomly chosen stores throughout the city of Bologna and suburban areas. The samples consisted of 25 g of loose minced beef, sometimes already shaped into meatballs or hamburgers, some of which were mixed with vegetables. The meat was purchased from retail outlets, open market stalls, and supermarket chains during 25 sampling visits from October 2000 to December 2001. For E. coli detection, Tryptone soya broth (TSB) supplemented with novobiocin and C-EC agar were used. Immunomagnetic separation with SMAC-BCIG-CT agar and chromogenic E. coli O 157 agar, API 20E system and agglutination latex test were used to detect E. coli O157; Vero cell assay and polymerase chain reaction (PCR) were used to assess toxin production and the presence of virulence genes.E. coli were detected in 45 (30.2%) of the 149 samples examined, mainly in the hamburger samples mixed with vegetables and in the loose minced beef. E. coli O157 was found in one sample of hamburger and two samples of hamburger mixed with vegetables (2%) collected from three different butcher's stores between July and October. All the strains of E. coli O157 and most cases of E. coli were found in meat from small retailers. The three strains of E. coli O157 were positive for verocytotoxin production. PCR analysis revealed genes coding for vt2 and one strain possessed the gene for eae A. Chromogenic E. coli O157 agar was found to be more selective and differential, allowing easier identification of suspected colonies with mixed flora and producing less false-positive colonies.

[Infection control in dental health care settings: results of a survey on current disinfection practices]. / La disinfezione in ambiente odontoiatrico: risultati di una indagine sulle procedure adottate.

This study was performed to identify which disinfection procedures are currently used in dental offices and to evaluate staff knowledge regarding infection control. Information was collected by means of a questionnaire to which 226 subjects responded. Glutaraldehyde was found to be the most commonly used disinfectant for surfaces/drill units, handpieces and instruments; however, half of the respondents did not specify which disinfectants they used. Eighty-four percent of the respondents reported contact times, which in some cases were found to be insufficient; 43,4% stated that containers are washed and disinfected each time the disinfectant is replaced; 58.8% reported that dental handpieces and instruments are precleaned prior to sterilization while 73% believe that increased attention during performance of work practices could reduce the risk of infection. These findings suggest that dental health care personnel need to be better sensitized toward infection control measures and should be offered periodical training on the proper implementation of practice guidelines.

Removal of indicator bacteriophages from municipal wastewater by a full-scale membrane bioreactor and a conventional activated sludge process: implications to water reuse.

The effectiveness of a full scale membrane bioreactor (MBR) in the removal of bacteriophages and bacterial fecal indicators from municipal wastewater was compared with that obtained by conventional activated sludge process (CASP). Somatic coliphages (SOMCPH) and F-RNA specific bacteriophages (FRNAPH) were always detected in the pre-treated effluent (mean: 6Log10), while phages infecting Bacteroides fragilis were not always present (mean: 3.9Log10). The MBR process was able to achieve respectively 2.7 and 1.7Log10 higher reductions of SOMCPH and FRNAPH compared to CASP (significant differences: P<0.05). SOMCPH were found to be the most suitable indicators for assessing MBR performance, since they showed greater resistance to biofiltration than FRNAPH and a more regular distribution in pre-treated effluent than BFRAGPH. Moreover, since the traditional bacterial indicators were almost totally removed by biofiltration, SOMCPH proved to be the best indicators to evaluate the microbiological risk when MBR effluent is discharged into natural waters or reused.

Performance of a full-scale membrane bioreactor system in treating municipal wastewater for reuse purposes.

The microbial removal efficacy of membrane bioreactor (MBR) technology in a full-scale municipal wastewater treatment plant was evaluated. Total and faecal coliforms, thermo-tolerant coliforms, Escherichia coli, enterococci, somatic coliphages, F-RNA specific bacteriophages and bacteriophages infecting Bacteroides fragilis (BFRPH) were used as bacterial and viral indicators. Reclamation and reuse of MBR effluent were considered. The average Log(10) reductions of the bacterial indicators range from 6 Log(10) for enterococci to 7 Log(10) for E. coli and faecal coliforms. The average removal of FRNA coliphages was similar to that of enterococci. Complete removal of BFRPH was observed. Log(10) reductions of somatic coliphages were significantly lower than those of all other indicators. Somatic coliphages appear to be better indicators of the microbial removal efficiency of the MBR system than faecal bacterial indicators. The quality of the MBR permeate conforms largely with the microbiological standards for urban (e.g. street cleaning, vehicle washing) and agricultural reuse.

Control of Pseudomonas aeruginosa and Stenotrophomonas maltophilia contamination of microfiltered water dispensers with peracetic acid and hydrogen peroxide.

The abilities of peracetic acid and hydrogen peroxide to remove or reduce Pseudomonas aeruginosa and Stenotrophomonas maltophilia in output water from microfiltered water dispensers (MWDs) were investigated. Two MWDs were inoculated with strains of P. aeruginosa and S. maltophilia isolated from water. Dispensers A and B were disinfected with 10% (v/v) peracetic acid (PAA) and 3% (v/v) hydrogen peroxide (HP) respectively. Each dispenser was disinfected three times at monthly intervals with contact times of 10, 30 and 40 min. Water dispensed by the MWDs was collected immediately before and after each treatment and then twice weekly for the remaining period. Once a week a sample of the tap water entering the dispensers was tested. P. aeruginosa and S. maltophilia were enumerated in the 90 samples collected during 6 months. In the output water from the dispensers before the first treatment, the number of the bacteria was 3 to 4 log cfu/100 mL. Treatment with PAA greatly reduced the numbers of P. aeruginosa and S. maltophilia in the dispensed water initially. However, by 2 days after treatment, the numbers increased and remained high. In the case of disinfection with HP for 40 min, P. aeruginosa was not detected in most of the samples (73.7%). Numbers of S. maltophilia decreased with increasing time after treatment.

Legionella contamination in hot water of Italian hotels.

A cross-sectional multicenter survey of Italian hotels was conducted to investigate Legionella spp. contamination of hot water. Chemical parameters (hardness, free chlorine concentration, and trace element concentrations), water systems, and building characteristics were evaluated to study risk factors for colonization. The hot water systems of Italian hotels were strongly colonized by Legionella; 75% of the buildings examined and 60% of the water samples were contaminated, mainly at levels of > or =10(3) CFU liter(-1), and Legionella pneumophila was the most frequently isolated species (87%). L. pneumophila serogroup 1 was isolated from 45.8% of the contaminated sites and from 32.5% of the hotels examined. When a multivariate logistic model was used, only hotel age was associated with contamination, but the risk factors differed depending on the contaminating species and serogroup. Soft water with higher chlorine levels and higher temperatures were associated with L. pneumophila serogroup 1 colonization, whereas the opposite was observed for serogroups 2 to 14. In conclusion, Italian hotels, particularly those located in old buildings, represent a major source of risk for Legionnaires' disease due to the high frequency of Legionella contamination, high germ concentration, and major L. pneumophila serogroup 1 colonization. The possible role of chlorine in favoring the survival of Legionella species is discussed.