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Biomedical subjects

R A Raphael

Publications and source records attributed to R A Raphael.

8 recordsLinked to original sources
PubMed1985

Rotavirus concentration from raw water using positively charged filters.

Positively charged (PC) Zeta Plus (30 S) filters and talc-Celite (TC) layers were tested for their ability to concentrate human rotavirus (strain Wa) from seeded samples of raw water (RW), collected from the Ottawa River. In the TC technique, the RW sample was preconditioned by adding Earle's balanced salt solution (1:100) and reducing the pH to 6.0 before passing it through the TC layer. Almost 6% of the input virus was lost in the filtrate. Using 1 X tryptose phosphate broth (TPB) at pH 9.0 as an eluent, 48% of the virus could be recovered from the layers. With the 30 S PC filters, no sample preconditioning was required and no virus was detected in the filtrates. In virus elution from these filters, 1 X TPB (pH 9.0), and a mixture of 6% glycine + 6% arginine (pH 9.0) gave virus recoveries of 44% and 46%, respectively. When these same two eluents were used in sequence to recover the rotavirus from 30 S PC filters, a virus recovery of about 70% was obtained. However, when 20 1 vols. of seeded raw water were concentrated using 30 S PC filters (142 mm diameter), and polyethylene glycol hydroextraction was used for second-step concentration of the eluates, only 16% of the input infectious virus could be recovered. The 30 S PC filters were then used to recover naturally occurring rotaviruses from the waters of the Ottawa River. After concentration, these viruses were detected and quantitated in MA-104 cells using an indirect immunoperoxidase staining technique.

Adsorption↗
PubMed1985

Long-term survival of human rotavirus in raw and treated river water.

This study was aimed at assessing the role of water as a vehicle for rotavirus spread by determining how well these viruses survive in the water environment. A cell culture adapted strain of human rotavirus subgroup 2, grown in MA-104 cells, was used as a model. Virus survival was tested in the following types of water samples, derived from the Ottawa River, at two different times of the year: (i) raw water (RW), (ii) muncipally treated tap water (TW), and (iii) raw water that had been filtered (FW) through a membrane (0.22 micron). The water samples, with approximately 5.0 X 10(4) plaque-forming units (PFU) of the virus, were held at either 4 or 20 degrees C and tested for infectious virus over a period of 64 days. The TW samples had a total and free chlorine content of 0.05 and less than 0.05 mg/L, respectively. The chlorine in these samples was not neutralized before virus contamination. Irrespective of the holding temperature, the virus titre in FW remained essentially unaltered throughout the test period. In TW held at 4 degrees C, there was no significant drop in the virus titre even after 64 days, whereas at 20 degrees C the titre in TW was reduced by about 2 log10 over the same period. Even though the loss of virus infectivity was most rapid in RW held at 20 degrees C, it took about 10 days for a 99.0% reduction in the plaque titre of the virus. These findings, therefore, indicate that rotaviruses can survive for several days in raw and treated river water thus making recreational and potable waters potential vehicles for the transmission of rotavirus infections.

Animals↗
PubMed1984

Rotavirus survival in conventionally treated drinking water.

Samples of conventionally treated drinking water collected either as effluent (PE) at a treatment plant or out of a tap (TW) in our laboratory were seeded with simian rotavirus SA-11, which closely resembles rotavirus of human origin. The virus, grown in MA-104 cells, was suspended either in distilled water, Earle's balanced salt solution (EBSS), or tryptose phosphate broth (TPB), and added to the water samples to a final concentration of 5.7 X 10(3) plaque-forming units (PFU) per millilitre. After a contact time of 1 h at 22 degrees C, the samples were diluted and plaque assayed. There was no significant reduction in the virus titre in samples of TW (less than 0.05 mg/L free chlorine). The titre also remained almost the same in PE (0.75 mg/L free chlorine) when EBSS or TPB was used for virus suspension. There was, however, nearly a 1 log10 loss in the titre of the virus when it was suspended in distilled water before the contamination of PE. To study the long-term survival of the rotavirus in TW, the inoculated samples (5.0 X 10(4) PFU/mL) were held at either 4 or 20 degrees C in the dark and tested over a period of 64 days. At 20 degrees C it took 64 days to reduce the virus titre by 2 log10, whereas at 4 degrees C the virus titre dropped only 0.7 log10 during the same period. Rotaviruses could, therefore, survive well enough in conventionally treated drinking water to make it a possible vehicle for their transmission.

Animals↗
PubMed1983

Rotavirus inactivation by chemical disinfectants and antiseptics used in hospitals.

Nosocomial outbreaks of rotaviral gastroenteritis are a common occurrence. Although proper disinfection practices in the hospital environment are considered to be important in the prevention and control of such outbreaks, very little information has been available on the rotavirus-inactivating capacity of chemical disinfectants and antiseptics commonly used in hospitals. In view of this, 11 such products were selected and screened for their capacity to bring about at least a 3 log10 reduction in the plaque titre of rotavirus SA-11 after a contact time of 1-30 min. Consept "D" (1:100), D.R.X. (1:80), Dustbane Germicidal (1:80), Hibitane, and Wescodyne (1:200) were found to be ineffective under these test conditions even in the absence of an added organic load. The virucidal capacity of Savlon (1:200) and Zephiran was completely neutralized when single-strength tryptose phosphate broth was added to the virus-disinfectant mixture to simulate an organic load. Cidex (2% acid glutaraldehyde), Proviodine (10% solution of povidone-iodine), Septisol (0.75% hexachlorophene), and Sana Rinse (70% isopropylalcohol, 0.1% hexachlorophene) were able to produce at least a 3 log10 (99.9%) reduction in the virus plaque titre even in the presence of added organic matter. These findings should be of help in the prevention and control of outbreaks of rotaviral diarrhea in the hospital environment.

Anti-Infective Agents, Local↗