Water disinfection for international and wilderness travelers

Sequential Approach for Water Purification Using Seashell-Derived Calcium Oxide through Disinfection and Flocculation with Polyphosphate for Chemical Pollutant Removal

Safe water supply is usually inadequate in areas without water treatment plants and even in a city under emergency conditions due to a disaster, even though safe water is essential for drinking and other various purposes. The purification of surface water from a river, lake, or pond requires disinfection and removal of chemical pollutants. In this study, we report a water purification strategy using seashell-derived calcium oxide (CaO) via disinfection and subsequent flocculation with polyphosphate for chemical pollutant removal. Seashell-derived CaO at a concentration (2 g L-1) higher than its saturation concentration caused the >99.999% inactivation of bacteria, mainly due to the alkalinity of calcium hydroxide (Ca(OH)2) produced by hydration. After the disinfection, the addition of sodium polyphosphate at 2 g L-1 allowed for the flocculation of CaO/Ca(OH)2 particles with adsorbing chemical pollutants, such as Congo red, dichlorodiphenyltrichloroethane, di(2-ethylhexyl)phthalate, and polychlorinated biphenyls, for removing these pollutants; purified water was obtained through filtration. Although this purified water was initially highly alkaline (pH ∼ 12.5), its pH decreased into a weak alkaline region (pH ∼ 9) during exposure to ambient air by absorbing carbon dioxide from the air with the precipitating calcium carbonate. The advantages of this water purification strategy include the fact that the saturation of CaO/Ca(OH)2 potentially serves as a visual indicator of disinfection, that the flocculation by polyphosphate removes excessive CaO/Ca(OH)2 as well as chemical pollutants, and that the high pH and Ca2+ concentrations in the resulting purified water are readily decreased. Our findings suggest the usability of seashell-derived material-polymer assemblies for water purification, especially under emergency conditions due to disasters.

A Tent-Inspired Portable Solar-Driven Water Purification Device for Wilderness Explorers

Wilderness adventure favored by many enthusiasts often endanger lives due to lacking freshwater or drinking contaminated water. Therefore, compared to the inefficient methods of filtration, steaming, and direct solar heating, it is of great meaningfulness to develop a solar-driven water purification device with efficiency, lightweight, portability, and multi-water-quality purification by taking full advantage of solar-driven interfacial evaporation. Here, a tent-inspired portable solar-driven water purification device consisting of Janus-structured bacterial cellulose aerogel (JBCA) solar evaporator and tent-type condensation recovery device is reported. For the JBCA solar evaporator, it is prepared from biomass bacterial cellulose (BC) as raw material and hydroxylated carbon nanotubes (HCNT) as photothermal material, and the Janus property is achieved by the assistance of hydrophobic and hydrophilic chemical cross-linking. It exhibits lightweight, unibody, high photothermal conversion, efficient evaporation, and multi-water-quality purification capability for representative seawater, urine, and bacterial river water. For the tent-type condensation recovery device, it is based on the prototype of tent and uses flexible ultra-transparent polyvinyl chloride (PVC) film as raw material. Thanks to the rational prototype and material selection, it displays outstanding portability and lightweight through the folding/unfolding method. Therefore, the designed tent-inspired portable solar-driven water purification device demonstrates great potential application in wilderness exploration.

A Crosslinked Ionic Organic Framework for Efficient Iodine and Iodide Remediation in Water

Iodine is widely used as an antimicrobial reagent for water disinfection in the wilderness and outer space, but residual iodine and iodide need to be removed for health reasons. Currently, it is challenging to remove low concentrations of iodine and iodide in water (≈5 ppm). Furthermore, the remediation of iodine and iodide across a broad temperature range (up to 90 °C) has not previously been investigated. In this work, we report a nitrate dimer-directed synthesis of a single-crystalline ionic hydrogen-bonded crosslinked organic framework (H_C OF-7). H_C OF-7 removes iodine and iodide species in water efficiently through halogen bonding and anion exchange, reducing the total iodine concentration to 0.22 ppm at room temperature. Packed H_C OF-7 columns were employed for iodine/iodide breakthrough experiments between 23 and 90 °C, and large breakthrough volumes were recorded (≥18.3 L g^-1 ). The high iodine/iodide removal benchmarks recorded under practical conditions make H_C OF-7 a promising adsorbent for water treatment.

Biomimetic Core-Shell-Structured Nanofiber Membranes for Rapid and Portable Water Purification

Rapid and portable water purification (RPWP) technologies, helping travelers survive in the wild, have attracted increasing interest due to increasing activities, such as exploration, field hiking, and excursion. Field water is usually pathogenic because of various soluble and insoluble contaminants. In this study, fish-gill-like biomimetic core-shell-structured nanofiber membranes are designed and synthesized by an in situ oxidation polymerization coating process. A polyimide nanofiber membrane and a polypyrrole (PPy) coating layer are employed as a core and shell, respectively. The biomimetic membranes exhibit dual-functional capacities: a rapid removal of insoluble contaminants owing to the highly porous network and broad-spectrum adsorption of soluble contaminants enabled by the PPy shell. Model studies confirm the excellent ability of the membranes to purify Cr(VI)-contaminated water to drinkable water with a safe capacity of ∼1415 L m^-2. Actual application tests show that the membrane can efficiently remove coliform and suspended solids in a muddy water sample taken from a river in Suzhou, China. This study provides a promising route for the design of a single-layer membrane with dual functions for highly efficient RPWP.

Disinfection Performance of a Drinking Water Bottle System With a UV Subtype C LED Cap Against Waterborne Pathogens and Heterotrophic Contaminants

The purgaty One systems (cap+bottle) are portable stainless-steel water bottles with UV subtype C (UVC) disinfection capability. This study examines the bottle design, verifies disinfection performance against Escherichia coli, Pseudomonas aeruginosa, Vibrio cholerae, and heterotrophic contaminants, and addresses the public health relevance of heterotrophic bacteria. Bottles were inoculated with deliberately contaminated potable water and disinfection efficacy examined using colony forming unit (CFU) assay for each bacterial strain. The heterotrophic plate count (HPC) method was used to determine the disinfection performance against environmental contaminants at day 0 and after 3days of water in stationary condition without prior UVC exposure. All UVC irradiation experiments were performed under stationary conditions to confirm that the preset application cycle of 55s offers the desired disinfection performance under-tested conditions. To determine effectiveness of purgaty One systems (cap+bottle) in disinfection, inactivation efficacy or log reduction value (LRV) was determined using bacteria concentration between UVC ON condition and controls (UVC OFF). The study utilized the 16S ribosomal RNA (rRNA) gene for characterization of isolates by identifying HPC bacteria to confirm if they belong to groups that are of public health concern. Purgaty One systems fitted with Klaran UVC LEDs achieved 99.99% inactivation (LRV4) efficacy against E. coli and 99.9% inactivation (LRV3) against P. aeruginosa, V. cholerae, and heterotrophic contaminants. Based on the 16S rRNA gene analyses, the study determined that the identified HPC isolates from UVC irradiated water are of rare public health concern. The bottles satisfactorily inactivated the target pathogenic bacteria and HPC contaminants even after 3days of water in stationary condition.

Capture and Release Recyclable Dimethylaminomethyl-Calixarene Functional Cloths for Point-of-Use Removal of Highly Toxic Chromium Water Pollutants

Chromium(VI) contamination of drinking water arises from industrial activity wherever there is a lack of environmental legislation enforcement regarding the removal of such pollutants. Although it is possible to remove such harmful metal ions from drinking water through large-scale facilities, there currently exists no safe and simple way to filter chromium(VI) oxoanions at the point of use (which is potentially safer and necessary in remote locations or humanitarian scenarios). High-surface-area cloth substrates have been functionalized with calixarene molecules for the selective capture of aqueous chromium(VI) oxoanions in the presence of structurally similar anions. This is accomplished by pulsed plasmachemical deposition of a linker layer and subsequent functionalization with dimethylaminomethyl-calixarene (5,11,17,23-tetrakis[(dimethylamino)methyl]-25,26,27,28-tetrahydroxycalix[4]arene). Chromium(VI) oxoanions are captured by simply passing polluted water through the functionalized cloth, while other ions not harmful/beneficial to human health remain in the water. These cloth filters are simple to use, highly selective, and easily recyclable-thus making them attractive for point-of-use application in geographic regions lacking appropriate wastewater treatment plants or flawed environmental monitoring systems. Chromium(VI) pollutants have been successfully removed from real-world contaminated industrial wastewater streams using the dimethylaminomethyl-calixarene functionalized cloths.

Deploying Elemental Iodine in a Vapor Form to Disinfect Water and to Clear Biofilms

Traditionally, iodine has been delivered as a solution, tablet or resin to disinfect water. In this study we evaluated the “I₂ vapor infusion” (I₂VP) technology which passes an airstream through a matrix containing elemental iodine (I₂) to produce I₂ vapor as an innovative method of iodine delivery for water disinfection. Pressured air was provided either by a compressor or hand pump. Testing was performed with water inoculated with either Gram-negative (Escherichia, Salmonella) or Gram-positive (Enterococcus) bacteria or with pre-formed Acinetobacter or Staphylococcus biofilms. Bacterial colony forming units were used to assess efficacy of the device. In distilled water all bacteria and biofilms were eliminated after brief exposures (<90 s). Culturable bacteria were also eliminated from pond and municipal sewer water, but the technology was mostly ineffective against dairy lagoon water with high turbidity and organic particulate. Longer duration infusion and higher air volumes used to overcome interference from organic matter were also associated with higher concentrations of residual iodine. We conclude that I₂ vapor infusion has the potential to be useful for emergency water treatment and potentially for reducing microbiological contamination of some waste streams.

Swedish isolates of Vibrio cholerae enhance their survival when interacted intracellularly with Acanthamoeba castellanii

Vibrio cholerae is a Gram-negative bacterium that occurs naturally in aquatic environment. Only V. cholerae O1 and V. cholerae O139 produce cholera toxin and cause cholera, other serogroups can cause gastroenteritis, open wounds infection, and septicaemia. V. cholerae O1 and V. cholerae O139 grow and survive inside Acanthamoeba castellanii. The aim of this study is to investigate the interactions of the Swedish clinical isolates V. cholerae O3, V. cholerae O4, V. cholerae O5, V. cholerae O11, and V. cholerae O160 with A. castellanii. The interaction between A. castellanii and V. cholerae strains was studied by means of amoeba cell counts, viable counts of the bacteria in the absence or presence of amoebae, and of the intracellularly growing bacteria, visualised by electron microscopy. These results show that all V. cholerae can grow and survive outside and inside the amoebae, disclosing that V. cholerae O3, V. cholerae O4, V. cholerae O5, V. cholerae O11, and V. cholerae O160 all can be considered as facultative intracellular bacteria.

Reusing larval rearing water and its effect on development and quality of Anopheles arabiensis mosquitoes

Background

There is growing interest in applying the sterile insect technique (SIT) against mosquitoes. Mass production of mosquitoes for large-scale releases demands a huge amount of water. Yet, many arid and/or seasonally arid countries face the difficulties of acute water shortage, deterioration of water quality and environmental constraints. The re-use of water to rear successive generations of larvae is attractive as a way to reduce water usage and running costs, and help to make this control method viable.

Methods

To determine whether dirty larval water was a suitable rearing medium for Anopheles arabiensis, in place of the ‘clean’ dechlorinated water routinely used, a series of three experiments was carried out to evaluate the effect of dirty water or mixed clean and dirty water on several parameters of insect quality. Batches of 100 fresh eggs were distributed in dirty water or added to clean water to test the effect of dirty water on egg hatching, whereas first-instar larvae were used to determine the effect on immature development time, pupation, adult emergence, body size, and longevity. Moreover, to assess the effect of dirty water on larval mortality, pupation rate, adult emergence, and longevity, L4 larvae collected after the tilting or larvae/pupae separation events were returned either to the dirty water or added to clean water.

Results

Results indicated that reusing dirty water or using a 50:50 mix of clean and dirty water did not affect egg hatching. Moreover, no difference was found in time to pupation, larval mortality or sex ratio when first-instar larvae were added to clean water, dirty water, or a 75:25, 50:50 or 25:75 mix of clean and dirty water and reared until emergence. When late-instar larvae were put back into their own rearing water, there was no effect on pupation rate, emergence rate or female longevity, though male longevity was reduced. When reared from first-instar larvae, however, dirty water decreased pupation rate, emergence rate, body size, and adult longevity.

Conclusions

Re-used larval-rearing water has no impact on egg hatching, development time or mortality of the immature stages of An. arabiensis. However, dirty water is not suitable for the production of high quality adult mosquitoes. Recycling processes to improve water quality and increase insect quality will be investigated, since it may have important implications for the implementation of the SIT in areas where clean water is a scarce or costly resource.

Drinking water treatment with ultraviolet light for travelers -- Evaluation of a mobile lightweight system

BACKGROUND

The SteriPEN(®) is a handheld device for disinfecting water with ultraviolet (UV) radiation. The manufacturer claims a reduction of at least 99.9% of bacteria, viruses, and protozoa. The present study intends to verify the general effectiveness of the device. Furthermore, the influence of bottle geometry and water movement is examined and the issue of user safety with regard to UV-C radiation is addressed.

METHODS

The device was applied on water containing a known number of microorganisms (Escherichia coli, Staphylococcus aureus, and the spore of Geobacillusstearothermophilus) and the survival rate was examined. Three different types of bottles commonly used among travelers served as test containers. All tests were conducted with and without agitating the water during irradiation. Furthermore, a spectral analysis was performed on the light of the device.

RESULTS

The SteriPEN(®) reached a mean reduction of more than 99.99% of bacteria and 99.57% of the spores when applied correctly. However, the results of the trials without agitating the water only yielded a 94.98% germ reduction. The device's maximal radiation intensity lies at 254 nm which is the wavelength most efficient in inactivating bacteria. The UV-C fraction is filtered out completely by common bottle materials. However, when applied in larger containers a portion of the UV-C rays exits the water surface.

CONCLUSIONS

If applied according to the instructions the device manages a satisfactory inactivation of bacteria. However, it bears the danger of user errors relevant to health. Therefore, education on the risks of incorrect application should be included in the travel medical consultation. Also there are still aspects that need to be subject to further independent research.

Development of nitrocellulose membrane filters impregnated with different biosynthesized silver nanoparticles applied to water purification

Bactericidal water filters were developed. For this purpose, nitrocellulose membrane filters were impregnated with different biosynthesized silver nanoparticles. Silver nanoparticles (AgNPs) from Aspergillus niger (AgNPs-Asp), Cryptococcus laurentii (AgNPs-Cry) and Rhodotorula glutinis (AgNPs-Rho) were used for impregnating nitrocellulose filters. The bactericidal properties of these nanoparticles against Escherichia coli, Enterococcus faecalis and Pseudomona aeruginosa were successfully demonstrated. The higher antimicrobial effect was observed for AgNPs-Rho. This fact would be related not only to the smallest particles, but also to polysaccharides groups that surrounding these particles. Moreover, in this study, complete inhibition of bacterial growth was observed on nitrocellulose membrane filters impregnated with 1 mg L(-1) of biosynthesized AgNPs. This concentration was able to reduce the bacteria colony count by over 5 orders of magnitude, doing suitable for a water purification device.

A compact point-of-use water purification cartridge for household use in developing countries

Simple, low-cost household interventions are known to be effective in lowering the incidence of waterborne diseases in developing countries. However, high costs along with operational and maintenance issues have prevented the successful adoption of these interventions among the affected communities. To address these limitations, a cost-effective, gravity-driven water purification cartridge has been developed by employing the synergistic disinfection action of low concentrations of silver and chlorine on bacteria and viruses. The silver and chlorine treatment components within the cartridge have been developed using inexpensive materials and integrated with a life indicator and auto-shut-off-mechanism within a compact form factor. The antibacterial as well as antiviral performance of the cartridge was tested by using ground water spiked with Escherichia coli and MS2 bacteriophage. The results show that, although individually, the silver and chlorine treatment systems were unable to inactivate the test strains, the integrated cartridge inactivates both bacteria as well as viruses up to the log reduction requirement of the USEPA guide standard for microbiological water purifiers over its designated life of 2,000 liters.

A blinded, randomized, palatability study comparing variations of 2 popular field water disinfection tablets

OBJECTIVE

Halogen-based water disinfection tablets may render an unpleasant taste to treated water. Proposed safe additives such as ascorbic acid may reduce this objectionable taste. We compared the palatability of 2 field water disinfectants: iodine-based tetraglycine hydroperiodide (TGHP) and chlorine-based chlorine dioxide (CD) both with and without the concomitant use of an ascorbic acid taste neutralizer.

METHODS

Blinded participants randomly sampled 5 different distilled water samples containing combinations of disinfectant tablets and ascorbic acid: 1) water; 2) water with TGHP; 3) water with CD; 4) water with TGHP plus ascorbic acid; and 5) water with CD plus ascorbic acid. Participants rated beverage taste via a 100 mm visual analogue scale (VAS) and ranked the samples from "most pleasant" to "least pleasant."

RESULTS

Sixty participants evaluated the samples. On the VAS, water with TGHP tasted worst and water with CD tasted second worst. Water with TGHP plus ascorbic acid, water alone, and water with CD plus ascorbic acid measured similarly as significantly best tasting. Water with TGHP was ranked by 58% as "least pleasant" tasting, while water with TGHP and ascorbic acid was ranked by 40% as "most pleasant" tasting.

CONCLUSIONS

Participants found halogen-based disinfected water significantly less palatable prior to the addition of ascorbic acid. Addition of ascorbic acid to treated water created a beverage of similar preference to distilled water. These results may increase compliance with the use of disinfecting tablets by increasing the palatability of drinking water made potable via addition of ascorbic acid to halogen-based chemical disinfection.

Increased persistence of Salmonella enterica serovar Typhi in the presence of Acanthamoeba castellanii

Salmonella enterica serovar Typhi (S. Typhi) is the etiological agent of the systemic disease typhoid fever. Transmission occurs via ingestion of contaminated food or water. S. Typhi is specific to humans, and no animal or environmental reservoirs are known. As the free-living amoeba Acanthamoeba castellanii is an environmental host for many pathogenic bacteria, this study investigates interactions between S. Typhi and A. castellanii by using cocultures. Growth of both organisms was estimated by cell count, viable count, flow cytometry, and fluorescence microscopy. Results indicate that S. Typhi can survive at least 3 weeks when grown with A. castellanii, as opposed to less than 10 days when grown as singly cultured bacteria under the same conditions. Interestingly, growth rates of amoebae after 14 days were similar in cocultures or when amoebae were singly cultured, suggesting that S. Typhi is not cytotoxic to A. castellanii. Bacteria surviving in coculture were not intracellular and did not require a physical contact with amoebae for their survival. These results suggest that S. Typhi may have a selective advantage when it is associated with A. castellanii and that amoebae may contribute to S. Typhi persistence in the environment.

Detection of Vibrio cholerae and Acanthamoeba species from same natural water samples collected from different cholera endemic areas in Sudan

Background

Vibrio cholerae O1 and V. cholerae O139 infect humans, causing the diarrheal and waterborne disease cholera, which is a worldwide health problem. V. cholerae and the free-living amoebae Acanthamoeba species are present in aquatic environments, including drinking water and it has shown that Acanthamoebae support bacterial growth and survival. Recently it has shown that Acanthamoeba species enhanced growth and survival of V. cholerae O1 and O139. Water samples from different cholera endemic areas in Sudan were collected with the aim to detect both V. cholerae and Acanthamoeba species from same natural water samples by polymerase chain reaction (PCR).

Findings

For the first time both V. cholerae and Acanthamoeba species were detected in same natural water samples collected from different cholera endemic areas in Sudan. 89% of detected V. cholerae was found with Acanthamoeba in same water samples.

Conclusions

The current findings disclose Acanthamoedae as a biological factor enhancing survival of V. cholerae in nature.

10% Povidone-iodine may be a practical field water disinfectant

OBJECTIVE

A paucity of data exists regarding the use of iodophores such as povidone-iodine (PVI) to disinfect water. We sought to determine a practical minimal disinfecting concentration of 10% PVI over different contact times and temperatures when added to water inoculated with E. coli.

METHODS

1:100, 1:1,000, and 1:10,000 dilutions of 10% PVI were created. Escherichia coli was exposed to these dilutions for 5, 15, and 30 minutes at 10, 20, and 30°C. Bactericidal activity was neutralized with 0.5% sodium thiosulfate. Mean viable colony forming units (CFUs) was determined after triplicate plating on Luria-bertani agar and 24 hours of incubation at 37°C. Effective bactericidal activity was defined as a 5-log reduction.

RESULTS

Of the 200,000 E. coli plated, no CFUs were observed after exposure to the 1:100 dilution. After 5 minutes of contact time with the 1:1,000 dilution, at 10°C CFUs were too numerous to count (TNTC), at 20°C the mean CFU count was 92 (standard error ±11), and at 30°C the mean CFU count was 25 (standard error ±8). No CFUs were observed after 15 minutes of exposure to the 1:1,000 dilution across experimental temperatures. The 1:10,000 dilution always yielded CFU growth that was TNTC.

CONCLUSIONS

The lowest disinfecting concentration of 10% PVI was the 1:1,000 dilution at 15 minutes of contact time. This supports the use of PVI for water disinfection against E. coli, the organism most commonly responsible for traveler's diarrhea. Further studies may assess its effectiveness against more virulent water borne pathogens.

A comparison of bacterial colony-forming units in water bottles and hydration bags among outdoor enthusiasts

OBJECTIVE

Transporting clean drinking water in an easily accessible container is a priority for many outdoor enthusiasts. Two basic hydration systems are commonly used to provide water: the water bottle and the hydration bladder. The authors tested the hypothesis that there were different levels of microbiologic contamination between these 2 systems.

METHODS

Sixty-seven water samples were collected using sterile techniques from outdoor enthusiasts at several outdoor recreational locations. These users were then asked to complete a brief survey that reported demographic information and details of water container use. Water samples were then plated on sheep blood agar, and the colony-forming units were counted after 24 hours of growth. The 2 groups were compared using Student's t test.

RESULTS

The 2 groups using water bottles or hydration bladders did not show significant differences in container age, duration of outdoor activity, or duration since last cleaning. The groups differed slightly in their composition of hikers/walkers/runners vs cyclists. The water bottle group had a mean colony-forming unit count per 100 mL of 37 (95% CI 26-48), and the hydration bladder had a mean of 27 (95% CI 17-35).

CONCLUSIONS

There was no statistically significant difference between hydration bladders and water bottles in microbial contamination or colonization. Judging from the available data, outdoor enthusiasts should select their water container based on criteria other than the relative exposure to microbes. Additional study is required to replicate this finding in other locations and with improved sample methodology.

Vibrio cholerae O139 requires neither capsule nor LPS O side chain to grow inside Acanthamoeba castellanii

Vibrio cholerae, the causative agent of cholera, has the ability to grow and survive in the aquatic free-living amoeba Acanthamoeba castellanii. The aim of the present study was to examine the ability of the clinical isolate V. cholerae O139 MO10 to grow in A. castellanii and to determine the effect of the bacterial capsule and LPS O side chain on intracellular growth. Results from co-cultivation, viable counts, a gentamicin assay, electron microscopy and statistical analysis showed that the association of V. cholerae O139 MO10 with A. castellanii did not inhibit growth of the amoeba, and enhanced growth and survival of V. cholerae O139 MO10 occurred. The wild-type V. cholerae O139 MO10 and a capsule mutant or capsule/LPS double mutant grew inside A. castellanii. Neither the capsule nor the LPS O side chain of V. cholerae O139 was found to play an important role in the interaction with A. castellanii, disclosing the ability of V. cholerae to multiply and survive inside A. castellanii, as well as the role of A. castellanii as an environmental host for V. cholerae.

IMS method performance analyses for Giardia in water under differing conditions

Immunomagnetic separation (IMS) has been specified as a standard method for the measurement of Giardia under USEPA Method 1623. In this study, IMS was evaluated on the basis of recovery efficiencies for Giardia cysts under various IMS operation conditions. Significant change in recovery was observed by altering the debris ratio of water samples. Notably, cyst recovery efficiencies utilizing IMS dropped with increased turbidity, and results for varying dosages of magnetic beads and cysts indicate that 1 / 100 immunomagnetic beads is sufficient to conjugate large numbers of cysts. Changing vessel volume and replacing the sample buffer had no significant effect on cyst recovery efficiencies.

Vibrio cholerae O1 strains are facultative intracellular bacteria, able to survive and multiply symbiotically inside the aquatic free-living amoeba Acanthamoeba castellanii

Vibrio cholerae species are extracellular, waterborne, gram-negative bacteria that are overwhelmed by predators in aquatic environments. The unencapsulated serogroup V. cholerae O1 and encapsulated V. cholerae O139 cause epidemic and pandemic outbreaks of cholera. It has recently been shown that the aquatic and free-living amoeba Acanthamoeba castellanii is not a predator to V. cholerae O139; rather, V. cholerae O139 has shown an intracellular compatibility with this host. The aim of this study was to examine the ability of V. cholerae O1 classical and El Tor strains to grow and survive in A. castellanii. The interaction between A. castellanii and V. cholerae O1 strains was studied by means of amoeba cell counts and viable counts of the bacteria in the absence or presence of amoebae. The viable count of intracellularly growing bacteria was estimated by utilizing gentamicin assay. Confocal microscopy and electron microscopy were used to determine the intracellular localization of V. cholerae in A. castellanii. The results showed that V. cholerae O1 classical and El Tor strains grew and survived intracellularly in the cytoplasm of trophozoites, and that the bacteria were also found in the cysts of A. castellanii. The interaction showed a facultative intracellular behaviour of V. cholerae O1 classical and El Tor strains and a possible role of A. castellanii as an environmental host of V. cholerae species.

Elimination of botulinum neurotoxin (BoNT) type B from drinking water by small-scale (personal-use) water purification devices and detection of BoNT in water samples

Seven small-scale drinking water purification devices were evaluated for their capacity to eliminate botulinum neurotoxin (BoNT) type B from drinking water. Influent water inoculated with toxic Clostridium botulinum cultures and effluent purified water samples were tested for the presence of BoNT by using a standard mouse bioassay and two commercial rapid enzyme immunoassays (EIAs). The water purification devices based on filtration through ceramic or membrane filters with a pore size of 0.2 to 0.4 microm or irradiation from a low-pressure UV-lamp (254 nm) failed to remove BoNT from raw water (reduction of < 0.1 log10 units). A single device based on reverse osmosis was capable of removing the BoNT to a level below the detection limit of the mouse bioassay (reduction of > 2.3 log10 units). The rapid EIAs intended for the detection of BoNT from various types of samples failed to detect BoNT from aqueous samples containing an estimated concentration of BoNT of 396,000 ng/liter.

Pharmacotherapy, vaccines and malaria advice for HIV-infected travellers

Since the introduction of effective antiretroviral therapy (ART), HIV-infected individuals are travelling more frequently and international travel has become much safer. Specific concerns include the safety of ART during travel, drug adherence and interaction considerations, and effects of immunosuppression. This review describes potentially important infections, vaccine effectiveness, safety and special approaches for their use, and HIV-related issues regarding predeparture counselling. With advanced immunosuppression (CD4+ T-cell count < 200/microl or < 14%), the immunogenicity of several vaccines is reduced, complications could occur after live attenuated vaccines and certain infections acquired during travel may be more frequent or severe. Challenges include the best options for malaria chemoprophylaxis, standby treatment and medical follow-up of the increasing number of HIV-infected long-term travellers.

Influence of hygiene on gastrointestinal illness among wilderness backpackers

BACKGROUND

Gastrointestinal illness is a common risk for wilderness travelers, even among those who consistently disinfect their water, yet the importance of hygiene has not been characterized.

METHODS

In a prospective surveillance study, 334 Appalachian Trail backpackers who hiked for at least 7 days in 1997 were interviewed. Upon completion of their hike, a written questionnaire was sent, addressing illnesses, water disinfection methods, and hygiene. Hygiene inquiries focused on the frequency of behaviors concerning handwashing and cleaning cookware.

RESULTS

Two hundred and eighty backpackers compiled 38,940 wilderness exposure days, with 56% (n=56) experiencing diarrhea. Diarrhea correlated with the frequency of drinking untreated surface water (relative risk (RR) 2.4, 95% confidence interval (CI) 1.0-4.7%, p5.03). Of those who consistently treated water, 45% suffered from diarrhea, whereas 69% of those who inconsistently treated water experienced diarrhea (RR 0.65, 95% CI 0.53-0.81%, p5.001). Hikers practicing "good hygiene", defined as handwashing post-defecation and cleaning cookware routinely, were less likely to ever experience diarrhea (RR 0.47, 95% CI 0.22-0.99, p5.04). Routine handwashing with soap and water after both urination and defecation reduced the risk of diarrhea (RR 0.11, 95% CI 0.04-0.31%, p,.001). In a case-control analysis of those experiencing diarrhea, decreased diarrhea was associated with routine consumption of multivitamins (RR 0.50, 95% CI 0.37-0.66%, p,.001), routine cleaning of utensils with warm, soapy water (RR 0.38, 95% CI 0.20-0.74%, p,.01), and post-defecation handwashing with soap and water (RR 0.61, 95% CI 0.39-0.93%, p5.006).

CONCLUSIONS

Lack of hygiene, specifically handwashing and cleaning of cookware, should be recognized as a significant contributor to wilderness gastrointestinal illness. Hikers should routinely disinfect water and avoid untreated surface water.

Coping with hygiene in South Africa, a water scarce country

The burden of infectious diseases may be reduced by adopting effective infection control measures. Some of these are dependent on the provision of adequate and safe water supplies for maintenance of basic standards of personal, domestic and healthcare hygiene. Consequences of scarce, and sometimes unsafe, waters supplies in South Africa are highlighted with reference to healthcare-associated infections, community acquired infectious intestinal diseases and domestic practices as infection sources. Availability of water in more than 67% of South African municipal hospitals and primary health care facilities (delivered by water tanker in 12.5% of satellite clinics, 5% from river or dam sources, 12.4% relying on rainwater) does not necessarily guarantee that it's quality is safe for utilisation. In the Northern Province and Mpumalanga, water needs to be purified prior to usage in 14.4 and 33% of satellite clinics respectively. Simple, low maintenance and low-cost interventions to maximise use and safety of limited water resources may be implemented: micro-organism (S. dysenteriae) inactivation by direct UV-exposure in sunlight abundant environments, water purification by filtration mechanisms and making use of iron pots in the community for pasteurisation, decontamination and boiling procedures. Education is paramount in promoting healthy domestic food handling practices, changing cultural perceptions of hygiene, hand-washing technique and mechanisms of domestic environmental decontamination. Water provision cannot be separated from other inter-related factors such as sanitation. Although the present government has taken initiatives to reduce the number of people not having access to water by 50% in 2002, provision of sanitation has been slower (>38% inadequate sanitation in 2002). Adoption of integrated environmental management approaches in conjunction with community participation (WASH Campaign--2002), by the government, aims to address the sanitation problems.

Medical risks of wilderness hiking

PURPOSE

We sought to determine the extent to which injuries and illnesses limit long-distance or endurance outdoor recreational activities.

METHODS

In a prospective surveillance study, 334 persons who hiked the Appalachian Trail for at least 7 days (mean [+/- SD] length of hike, 140 +/- 60 days) in 1997 were interviewed. At the end of their hike, subjects completed a questionnaire on injuries, illnesses, water purification methods, and hygiene practices.

RESULTS

Of the 280 backpackers who responded (a combined 38,940 days of wilderness exposure), 69% (n = 192) achieved their goal. The most important reasons for ending a hike prematurely were injury, time limitation, and psychosocial reasons. The most common medical complaints were feet blisters (64%; n = 180), diarrhea (56%, n = 156), skin irritation (51%, n = 143), and acute joint pain (36%, n = 102). The incidence of vector-borne disease was 4% (n = 11); physician-diagnosed Lyme disease was the most common, and 24% of hikers (n = 68) reported tick bites. The risk of diarrhea was greater among those who frequently drank untreated water from streams or ponds (odds ratio [OR] = 7.7; 95% confidence interval [CI]: 2.7 to 23; P <0.0001), whereas practicing "good hygiene" (defined as routine cleaning of cooking utensils and cleaning hands after bowel movements) was associated with a decreased risk (OR = 0.46; 95% CI: 0.22 to 0.97; P =0.04).

CONCLUSION

Diarrhea is the most common illness limiting long-distance hikers. Hikers should purify water routinely, avoiding using untreated surface water. The risk of gastrointestinal illness can also be reduced by maintaining personal hygiene practices and cleaning cookware.