Effect of point-of-use disinfection, flocculation and combined flocculation-disinfection on drinking water quality in western Kenya.

AIMS: Point-of-use drinking water disinfection with sodium hypochlorite has been shown to improve water quality and reduce diarrhoeal disease. However, the chlorine demand of highly turbid water may render sodium hypochlorite less effective. METHODS AND RESULTS: We evaluated a novel combined flocculant-disinfectant point-of-use water treatment product and compared its effect on drinking water quality with existing technologies in western Kenya. In water from 30 sources, combined flocculant-disinfectant reduced Escherichia coli concentrations to <1 CFU100 ml(-1) for 29 (97%) and reduced turbidity to <5 nephelometric turbidity units (NTU) for 26 (87%). By contrast, water from 30 sources treated with sodium hypochlorite reduced E. coli concentrations to <1 CFU 100 ml(-1) for 25 (83%) and turbidity to <5 NTU for 5 (17%). CONCLUSIONS: For source waters over a range of turbidities in western Kenya, combined flocculant-disinfectant product effectively reduces turbidity to <5 NTU and reduces E. coli concentrations to <1 CFU 100 ml(-1). SIGNIFICANCE AND IMPACT OF THE STUDY: The novel flocculant-disinfectant product may be acceptable to consumers and may be effective in reducing diarrhoeal disease in settings where source water is highly turbid.

A modified cup scrub method for assessing the antibacterial substantivity of personal cleansing products.

An improved in vivo method for evaluating the antibacterial substantivity or residual effectiveness of bar soaps and other personal cleansing products is presented. The effectiveness of an antibacterial bar soap containing 1.5% 3, 4, 4'-trichlorocarbanilide (TCC) versus its soap vehicle was evaluated under simulated conditions considered optimal for bacterial growth, proliferation, and possible infection. A washout period to clear the skin of any antimicrobial agents previously used was followed by a treatment period in which the subjects washed one of their forearms with the antibacterial soap and the other forearm with the soap vehicle. Either immediately or 24 hours following the final wash, three test sites on both forearms were inoculated with S. aureus and occluded with Hill Top Chamber patches. At intervals of 30 minutes, two hours and five hours, the patches were removed. The bacteria on the skin were harvested using the Williamson-Kligman scrub technique (1,2) to determine the number of surviving CFUs at each time period. The method successfully demonstrated that sufficient TCC had remained on the skin for 24 hours after the final wash to effectively inhibit the growth of S. aureuso on the skin for as long as five hours after inoculation.

The effect of antibacterial soap with 1.5% triclocarban on Staphylococcus aureus in patients with atopic dermatitis.

This double-blind study determined whether daily bathing with an antibacterial soap would reduce the number of Staphylococcus aureus on the skin and result in clinical improvement of atopic dermatitis. For 9 weeks, 50 patients with moderately severe atopic dermatitis bathed daily with either an antimicrobial soap containing 1.5% triclocarban or the placebo soap. They also used a nonmedicated moisturizer and 0.025% triamcinolone acetonide cream as needed, but the availability of the corticosteroid cream was discontinued after 6 weeks. The antimicrobial soap regimen caused significantly greater improvement in the severity and extent of skin lesions than the placebo soap regimen, which correlated with reductions both in S aureus in patients with positive cultures at baseline and in total aerobic organisms. Outcome measures included reductions in S aureus, total aerobic organisms, and dermatologic assessments. Overall, daily bathing with an antibacterial soap was well tolerated, provided clinical improvement, and reduced levels of skin microorganisms.

Leg wash protocol to assess the skin moisturization potential of personal cleansing products.

Many personal cleansers claim to provide a skin moisturization benefit, but there has been relatively little discussion in the scientific literature of the clinical methods that provide the basis for such claims. We have developed a leg wash method to assess the dry skin improvement potential of personal cleansing products. The protocol is performed on 'natural' dry leg skin to avoid potential confounds that may result from applying cleansers to soap-damaged skin. Washes are conducted over a period of days or weeks, with visual and instrumental assessments performed at various times throughout the period to characterize products' short-term and cumulative skin effects. Studies conducted with a variety of personal cleansing technologies demonstrate the method's ability to discriminate products on the basis of their dry skin improvement potential. Further, results from a series of eleven leg wash studies conducted with the same treatment pair under different test conditions (time of year, test facility, expert grader) demonstrate the protocol's robustness. The data generated under this protocol show that personal cleansing products differ widely in their ability to improve dry skin. Our results indicate that there is a wide range of efficacy among moisturizing personal cleansing products, with some products delivering a significant dry skin improvement benefit even for periods as long as 24 hours.

Seroepidemiology of cholera in Gulf coastal Texas.

Single serum samples from 559 volunteers from a Texas Gulf Coast area were examined for vibriocidal antibody to Vibrio cholerae O1 (biotype El Tor, serotype Inaba) by a microtiter method. Elevated levels of vibriocidal antibody were present in 14% of the subjects. Also, 6.8% of the subjects had elevated levels of antibody to the enterotoxin of V. cholerae O1 by the immunoglobulin G enzyme-linked immunosorbent assay. Recent infection, defined on the basis of elevations in both vibriocidal and antitoxin antibodies, had occurred in 1.3% of the subjects. When subjects who reported Brucella infection, travel to a cholera-endemic area, and/or cholera vaccination within a year of the study were removed from the analysis, a prevalence of recent infection of 0.89% was obtained. Significantly higher titers of vibriocidal antibody were found in those with exposure to seawater (fishermen, shrimpers, merchant marines, and dock workers) than in those without such exposure (P less than 0.005). Furthermore, titers of antitoxin antibody were significantly higher in those who consumed shellfish than in nonconsumers. Finally, titers of vibriocidal antibody were significantly higher in Vietnamese subjects than in non-Vietnamese subjects. The results of this study indicate that an endemic focus of infection with V. cholerae occurs in this area.

Modified scrub technique for sampling infant skin microflora.

Two techniques for quantitatively recovering normal-flora microorganisms from the skin of infants were compared. A technique using a swab to dislodge microorganisms from the skin compared favorably to a technique using a rubber policeman. The swab was easier to use and is suitable for use on infant skin.

Clinical effects of diaper types on the skin of normal infants and infants with atopic dermatitis.

Cloth diapers, cellulose core diapers (conventional disposable diapers), and cellulose core diapers containing absorbent gelling material were examined for their effects on diaper rash and skin microbiology of normal infants and infants with atopic dermatitis in a 26-week double-blind clinical trial. Infants with atopic dermatitis wearing the diapers containing absorbent gelling material had significantly lower diaper rash grades than infants with atopic dermatitis wearing cloth diapers at five of eight grading visits. Infants with atopic dermatitis wearing conventional cellulose core diapers had statistically less rash at one of eight visits. There was no statistically significant difference between diaper types at three of the eight visits. At no time did the cloth group have less diaper rash than the conventional cellulose or absorbent gelling material disposable diaper group. A statistical correlation between the severity of general atopic dermatitis outside the diaper area and the diaper rash condition under the diaper occurred only in the atopic dermatitis group wearing cloth diapers. Isolation of microorganisms from the intact, uninvolved skin surface both inside and outside the diaper showed no biologically significant changes in the presence or numbers of selected skin organisms. Repeated isolation, at multiple grading visits of Staphylococcus aureus from uncompromised skin inside the diaper area was infrequent but correlated with the diagnosis of atopic dermatitis when observed.

Norwalk virus antigen and antibody response in an adult volunteer study.

To better define the optimum timing of specimen collection and identify alternate ways to diagnose Norwalk virus outbreaks, we looked at the timing of the antibody response and virus excretion in a human volunteer study. The Norwalk virus antibody titers and antigen in stool specimens were examined by biotin-avidin immunoassay. Our data suggest that in epidemic situations, convalescent-phase sera could be collected as soon as 13 days after the onset of illness and acute-phase sera could be collected as late as 5 days after onset. Our data also suggest that if sufficient serum samples are collected, convalescent-phase case and control serum samples can be used to identify Norwalk virus outbreaks. Antigen detection was much less sensitive than seroconversion for detecting infection.

Diaper area skin microflora of normal children and children with atopic dermatitis.

In vitro studies established that neither cloth nor disposable diapers demonstrably contributed to the growth of Escherichia coli, Proteus vulgaris, Staphylococcus aureus, or Candida albicans when urine was present as a growth medium. In a clinical study of 166 children, the microbial skin flora of children with atopic dermatitis was compared with the flora of children with normal skin to determine the influence of diaper type. No biologically significant differences were detected between groups wearing disposable or cloth diapers in terms of frequency of isolation or log mean recovery of selected skin flora. Repeated isolation of S. aureus correlated with atopic dermatitis. The log mean recovery of S. aureus was higher in the atopic groups. The effects of each diaper type on skin microflora were equivalent in the normal and atopic populations.

Clinical and microbial effects of cloth, cellulose core, and cellulose core/absorbent gel diapers in atopic dermatitis.

Atopic dermatitis (AD) is an inherited cutaneous inflammatory condition which may affect 10% of infants. Persons with this diathesis are more susceptible to irritants and to superficial infections. Little is known about diaper rash and diapering materials in AD. In this study we set firm criteria to identify a large group of infants with AD for comparison with a nonatopic, normal control group in terms of severity of diaper dermatitis; relationship of diaper dermatitis to diaper materials; and influence of modifying factors (bacterial and candidal colonization/infection, diarrhea, antibiotics, other illnesses, food allergy or intolerance). Babies with eczema were recruited and, from a group of 2,443 respondents, 87 satisfied carefully defined criteria for atopic dermatitis. A similarly sized (90) control group matched for age, sex, and weight was selected for absence of features of atopy or familial atopic history. Infants were assigned into balanced subgroups wearing cloth diapers, conventional cellulose diapers, or diapers containing cellulose and absorbent gelling material (AGM). Assessment of grading for atopic parameters showed statistically significant differences between the AD and normal groups at every visit. Mean diaper rash grades, as assessed by the same physicians at each visit, were significantly higher in the AD group wearing cloth diapers compared with those in AGM subgroups at five of eight visits. There was significant correlation between AD severity and diaper rash scores overall and in the AD cloth group, but not in other subgroups. Quantitative total bacterial plate counts were significantly lower in AGM than cloth diaper areas on three of eight sampling periods in the AD group.(ABSTRACT TRUNCATED AT 250 WORDS)

Inactivation of Norwalk virus in drinking water by chlorine.

Norwalk virus in water was found to be more resistant to chlorine inactivation than poliovirus type 1 (LSc2Ab), human rotavirus (Wa), simian rotavirus (SA11), or f2 bacteriophage. A 3.75 mg/liter dose of chlorine was found to be effective against other viruses but failed to inactivate Norwalk virus. The Norwalk virus inoculum remained infectious for five of eight volunteers, despite the initial presence of free residual chlorine. Infectivity in volunteers was demonstrated by seroconversion to Norwalk virus. Fourteen of 16 subjects receiving untreated inoculum seroconverted to Norwalk virus. Illness was produced in four of the eight volunteers and in 11 of 16 control subjects. A similar Norwalk virus inoculum treated with a 10 mg/liter dose of chlorine produced illness in only one and failed to induce seroconversion in any of eight volunteers. Free chlorine (5 to 6 mg/liter) was measured in the reaction vessel after a 30-minute contact period. Norwalk virus appears to be very resistant to chlorine which may explain its importance in outbreaks of waterborne disease.

Detection of enteric viruses in treated drinking water.

The occurrence of viruses in conventionally treated drinking water derived from a heavily polluted source was evaluated by collecting and analyzing 38 large-volume (65- to 756-liter) samples of water from a 9 m3/s (205 X 10(6) gallons [776 X 10(6) liters] per day) water treatment plant. Samples of raw, clarified, filtered, and chlorinated finished water were concentrated by using the filter adsorption-elution technique. Of 23 samples of finished water, 19 (83%) contained viruses. None of the nine finished water samples collected during the dry season contained detectable total coliform bacteria. Seven of nine finished water samples collected during the dry season met turbidity, total coliform bacteria, and total residual chlorine standards. Of these, four contained virus. During the dry season the percent removals were 25 to 93% for enteric viruses, 89 to 100% for bacteria, and 81% for turbidity. During the rainy season the percent removals were 0 to 43% for enteric viruses, 80 to 96% for bacteria, and 63% for turbidity. None of the 14 finished water samples collected during the rainy season met turbidity standards, and all contained rotaviruses or enteroviruses.

Evaluation of filters for recovery of Campylobacter jejuni from water.

Campylobacter jejuni has been incriminated in several large waterborne outbreaks, but it has rarely been isolated from water itself. Better methodology is needed for the isolation of C. jejuni from water. We evaluated three types of 0.45-micron microporous filters and three different pore sizes of positively charged depth filters for their ability to recover C. jejuni from seeded, sterile tap and surface water. The microporous filters tested were Millipore HA, Gelman GN6, and Zetapor. Three pore sizes of Zeta Plus depth filters (05S, 30S, and 50S) were evaluated by using an adsorption-elution technique. The overall percent recovery in both tap and surface water by microporous filters was: Zetapor, 66%; Millipore HA, 33%; and Gelman GN6, 33%. Adsorption-elution with Zeta Plus 50S allowed 89% recovery of C. jejuni. These data suggest that both the positively charged Zetapor microporous filter and the Zeta Plus 50S depth filter are effective filters for the recovery of C. jejuni from water.

Survival and detection of rotaviruses on environmental surfaces in day care centers.

Previously, we demonstrated that children in day care centers commonly experience diarrhea due to rotavirus, giardia, and bacterial pathogens. Multiple agents frequently coexist, and the environment is heavily contaminated with enteric bacteria during outbreaks. A study of environmental surface contamination with rotavirus was performed during three non-outbreak periods. Of 25 samples collected from environmental surfaces and teachers hands at a day care center, 4 (16%) were positive for rotavirus antigen when a fluorescence assay was used. We also examined the survival of two animal viruses, rotavirus SA-11 and poliovirus type 1, and bacteriophage 12 on similar environmental surfaces in a laboratory. Poliovirus type 1 and bacteriophage f2 were more resistant to drying than rotavirus SA-11 and could be recovered after a 90-min exposure on a dry surface. Rotavirus SA-11 could be detected for 30 min. All three viruses survived longer when they were suspended in fecal material than when they were suspended in distilled water. These data suggest that several agents, including rotavirus, can remain viable on contaminated surfaces long enough to be transmitted to susceptible children. This finding helps explain why rotavirus shows a mode of spread like that of parasitic and bacterial agents within day care center settings.

Survival of enteric viruses adsorbed on electropositive filters.

Three viruses (poliovirus type 1, rotavirus SA-11, and bacteriophage f2) adsorbed on electropositive microporous filters survived at least 5 weeks at 4 degrees C. Poliovirus type 1 and bacteriophage f2 also survived at least 6 weeks at -20 degrees C. Rotavirus SA-11 was not recovered after 1 week at -20 degrees C. The stability of viruses adsorbed on electropositive filters may enable extensive monitoring of viruses in water.

Evaluation of a commercial enzyme immunoassay kit for rotavirus detection.

A commercial enzyme immunoassay kit (Rotazyme) was compared to electron microscopy for the detection of rotavirus in stool specimens collected during diarrhea outbreaks at day care centers in Houston. EIA was more sensitive than EM and detected SA-11 rotavirus which titered 2.0 X 10(3) PFU/ml.

Mechanism of poliovirus inactivation by bromine chloride.

The mechanism of poliovirus inactivation by BrCl was determined by exposing poliovirus to various concentrations of BrCl and correlating the loss of virus infectivity with structural changes of the virus. Concentrations of 0.3 to 5 mg of BrCl per liter resulted in 95% to total inactivation of poliovirus. However, the inactivated virus retained structural integrity, as determined by buoyant density measurements of poliovirus labeled with radioactivity. However, at concentrations of 10 to 20 mg of BrCl per liter, total inactivation of poliovirus was associated with the degradation of the structural integrity of the virus. Since infectious ribonucleic acid at similar concentrations could be recovered from untreated poliovirus and poliovirus treated with 0.3 mg of BrCl per liter, it was concluded that BrCl as HOBr or bromamines inactivates poliovirus by reacting with the protein coat of the virus. Moreover, this inactivating reaction does not result in the degradation of the structure of the virion, nor does it affect the biological activity of the internal ribonucleic acid of the virus.

Occurrence of enteroviruses in community swimming pools.

Municipal swimming pools and wading pools were examined for the presence of human enteric viruses using a portable virus concentrator at the site to concentrate viruses from 100-gallon to 500-gallon samples. Ten of 14 samples contained viruses; three of these were positive for virus in the presence of residual free chlorine. Enteroviruses were isolated from two pools which exceeded the 0.4 ppm free residual chlorine standard. This study appears to be supportive of recent evidence that indicates a higher incidence of enterovirus infection among bathers. All seven wading pool samples contained virus. Coxsackieviruses B3 and B4, poliovirus 1, and echovirus 7 were isolated. Total coliform bacteria were not adequate indicators of the presence of virus, as six of the samples were positive for virus but negative for coliforms. Total plate counts appeared to provide a better indication of the sanitary quality of the pool water, but viruses could still be detected in samples that met currently recommended bacterial levels. It is possible that swimming and wading pools may serve as a means of transmission of enteroviral disease, especially in children, during summer months.