Development and field testing of low-cost, quantal microbial assays with volunteer reporting as scalable means of drinking water safety estimation

AIMS

To evaluate a low-cost water quality test for at-scale drinking water safety estimation in rural India.

METHODS AND RESULTS

Within a longitudinal study to characterize variability in household drinking water safety in rural Maharashtra, we piloted a low-cost presence-absence (LCPA) microbial test designed to be used by volunteer residents in rural areas. In comparing the LCPA results with standard laboratory methods for enumeration of Escherichia coli, we found that LCPA tests using modified mTec media were highly sensitive in detecting drinking water of moderate risk (88% of tests were positive at E. coli counts of 11-100 CFU per 100 ml) and high risk (96% of tests were positive at E. coli counts of 101 + CFU per 100 ml). The LCPA tests demonstrated low specificity for E. coli specifically, due to concurrent detection of Klebsiella: 38% of LCPA tests were positive even when E. coli was not detected in a 100 ml sample by membrane filtration, suggesting the test would be conservative in risk estimation. We also found that 47% of participants in rural villages in India were willing to conduct tests and return results after a brief training, with 45% of active participants sending their water testing results via short message service.

CONCLUSIONS

Given their low cost (~US$0.50 as piloted) and open-source format, such tests may provide a compelling alternative to standard methods for rapid water quality assessments, especially in resource-limited settings.

SIGNIFICANCE AND IMPACT OF THE STUDY

The lack of availability of water quality data constrains efforts to monitor, evaluate and improve the safety of water and sanitation infrastructure in underserved settings. Current water testing methods are not scalable because of laboratory and cost constraints. Our findings indicate the LCPA or similar low-cost microbial tests could be useful in rapid water safety estimation, including via crowdsourcing.

One-year follow-up of titanium/zirconium alloy X commercially pure titanium narrow-diameter implants placed in the molar region of the mandible: a randomized controlled trial

OBJECTIVE

To analyze marginal bone loss (MBL) and clinical parameters around narrow-diameter implants (NDIs - 3.3 mm) made of titanium/zirconium alloy (TiZr) in comparison with commercially pure titanium (cpTi) installed in the molar region of the mandible after 1 year in function.

MATERIALS AND METHODS

Ten patients participated in the study. A TiZr and a cpTi NDI were randomly installed in contralateral molar sites of the mandible of each patient in a split-mouth design. Eight weeks after healing, all metal-ceramic single crowns were adapted to the implants and patients were enrolled in a plaque control program. MBL at the mesial and distal aspects of the implants were evaluated by comparing periapical radiographs taken immediately after prosthesis installation (T1) and 1 year after loading (T2). Clinical probing depth, bleeding on probing, suppuration, visible plaque and implant mobility were evaluated to determine implant success and survival rates.

RESULTS

Mean MBL at the interproximal aspects of TiZr implant sites was 0.32 ± 0.27 mm, while at cpTi implant sites mean MBL was 0.35 ± 0.24 mm (P = 0.60). Both TiZr and cpTi NDIs presented 100% implant survival and success rates, with no significant differences in the clinical parameters studied (P > 0.05).

CONCLUSION

TiZr and cpTi NDIs presented similar outcomes after 1 year in function in the molar region of the mandible. The results suggest that TiZr and cpTi NDIs may be equally used to support single crowns in the posterior area of the mouth. However, further studies with longer follow-up periods are necessary to confirm these findings.

Pharmacokinetics of Moclobemide in Male, Virgin Female, Pregnant and Nursing Rats

The disposition of moclobemide, a reversible inhibitor of monoamine oxidase isoenzyme A was studied in male, virgin female, pregnant and nursing rats. The average clearance in control rats (male and female) was 36 mL min−1 kg−1, the initial volume of distribution 1·4 L kg−1, the volume of distribution at steady state 2·3 L kg−1 and the terminal half-life 59 min. The blood-to-plasma concentration ratio of moclobemide was 0·84 giving rise to an average blood clearance of 30 mL min−1 kg−1. The clearance values in rats were higher than in man but as a fraction of hepatic blood flow were similar (36 vs 45%). The volume of distribution at steady state was approximately twice as high as in man while the half-life was similar. Pregnant and nursing rats showed no statistically significant differences in their disposition parameters for moclobemide compared with virgin female rats. Nursing rats had statistically significantly lower concentrations of the moclobemide N-oxide metabolite than did pregnant and control rats. Generally lower concentrations of the lactam metabolite were also found in this group although the differences did not reach statistical significance. Moclobemide as well as the N-oxide and lactam metabolites were found in the amniotic fluid suggesting that moclobemide is capable of crossing the placental barrier.

Glucocorticoid-dextran conjugates as potential prodrugs for colon-specific delivery: steady-state pharmacokinetics in the rat

Chronic colitis, e.g., ulcerative colitis and Crohn's disease, is presently treated with glucocorticoids and other antiinflammatory agents. Side-effects limit chronic glucocorticoid therapy. The dose, and consequently the side-effects, may be reduced by using prodrugs that selectively deliver drug to the colon. We previously synthesized glucocorticoid-dextran conjugates in which dexamethasone was attached to dextran (weight-average molecular weight = 72,600) using dicarboxylic acid linkers (succinate and glutarate). In the present study, dexamethasone-succinate-dextran and dexamethasone-glutarate-dextran were administered to two groups of male Sprague-Dawley rats by intragastric infusion. In two additional groups, disodium dexamethasone phosphate and dexamethasone hemisuccinate were each administered by subcutaneous infusion. In a fifth group, dexamethasone was administered by intragastric infusion. All groups were infused for sufficient time for steady state to be achieved. Colon-specific delivery was quantified using a drug-delivery index (DDI) in which steady-state dexamethasone concentrations in the cecum and colon were compared with those measured in blood after separate administrations of dexamethasone and dexamethasone-dextran conjugate. The colonic DDI values for dexamethasone-succinate-dextran and dexamethasone-glutarate-dextran were approximately seven and four, respectively. These values were a result of higher tissue concentrations and lower blood concentrations of dexamethasone after intragastric administration of the conjugates compared to subcutaneous and intragastric administration of dexamethasone. The pharmacokinetics of methyl-prednisolone was also investigated after subcutaneous infusion. Observed cecal and colonic tissue-to-blood ratios of 19:1 and 12:1, respectively, showed that this drug is extensively delivered to the large intestine even after subcutaneous administration.

Elimination of non-reactive and weakly reactive human alpha 1-acid glycoprotein after induction of the acute phase response in rats

The disposition of concanavalin A (Con A)-non-reactive and Con A-reactive human alpha 1-acid glycoprotein (AAG) was studied in normal male rats and in acute phase response-activated male rats. Activation of the acute phase response was made using a subcutaneous administration of ethynyloestradiol in sesame oil. This technique increased the endogenous AAG concentration 7-fold. In control rats the two forms of human AAG showed identical kinetics with an average clearance of 5.4 mL h-1 kg-1, terminal half-life of 13.5 h and a volume of distribution (steady state) of 91 mL kg-1. In the acute phase response-activated animals, both the clearance and volume of distribution were larger: the average clearance of the Con A-non-reactive AAG was 10.2 mL h-1 kg-1, the volume of distribution (steady state) 152 mL kg-1 and the terminal half-life 11.7 h. The Con A-reactive AAG had a clearance of 14.7 mL h-1 kg-1, a volume of distribution (steady state) of 262 mL kg-1 and a half-life of 15.8 h. The results indicate that not only does activation of the acute phase response alter the kinetics of AAG but that the change is different for the different types of AAG.