Present study was designed to explore the influences of different categories of chemical factors, such as organic solvents, oxidizing agents, anionic detergent and dye on persistence of locally isolated coliphages and shigaphages from clinical sewage samples. Thirty percent ethanol initiated 83.20 and 62.86% reduction in the number of coliphage and shigaphage plaques in our study respectively. Chloroform mediated decrease in our observation was 53.13 and 88.33% for coliphages and shigaphages, respectively. The number of the shigaphage plaques was reduced by 62.5% following biphasic diethyl ether (DEE) treatment. About 72.66% of coliphages were deactivated after exposure to biphasic diethyl ether. Exposure of the isolated coliphages and shigaphages to 1% formalin had completely destroyed the viability of the bacteriophages. Coliphage survival in this investigation was 37.5% and 2.4% following treatment with 0.3 and 3.0% hydrogen peroxide respectively. The decrease in overall coliphage and shigaphage population was 95.83% and 94.14% while treated with 0.5% sodium dodecyl sulfate (SDS). The number increased for the viruses infecting E. coli by 9.52% where the number of shigaphages declined by 14.63% while growing in presence of a divalent cation [Ca(NO3)2]. Coliphage and shigaphage populations were diminished by 61. 76% and 53.48% respectively after treatment with the neutral red (0.0075%) followed by exposure to visible light.Bangladesh J Microbiol, Volume 31, Number 1-2,June-Dec 2014, pp 47-52

Bacteriophages can survive under unfavorable conditions and their abilities of survivality are highly diversified. The influence of different physical and chemical conditions, such as temperature, pH and salts on the survivability of coliphages and shigaphages isolated from local clinical sewage samples have been summarized. Temperature at 45°C for 30 min caused 53.13% decrease in the number of coliphages but rather increased the number of shigaphages in present study. Temperature at 56°C for 30 min caused 91.41 and 100% fall in the number of coli- and shigaphages, respectively. pH 4 mediated 96.88% and pH 11 caused 100% decline in the number of plaques for coliphages. On the other hand, number of plaques of shigaphages was diminished by 100% at pH 4 and 91.67% at pH 11. MgCl2, MgSO4 and Na2SO4 salt solutions increased the number of coliphage plaques by 287.5, 125 and 37.5%. On the contrary, the decrease in the number of shigaphages was 79.31, 10.34 and 44.83%, respectively through the treatment. The various physical and chemical conditions investigated in this research have affected the test bacteriophages diversely. Temperature while applied at higher level (56ºC) affected the growth of both coliphages and shigaphages. Acidic and alkaline pH modified coli- and shigaphages' survivality and growth negatively. The three salts in question augmented the growth of isolated coliphages profoundly. However, the same three salts failed to do so for the isolated shigaphages. Dhaka Univ. J. Biol. Sci. 25(2): 185-194, 2016 (July)