OBJECTIVETo study the change of nucleic acid sequence and the germicidal effect of an E. coli bacteriophage with broad host range isolated from hospital sewage as well as to study the mechanism of phage host specificity and the effect of killed bacteria by phage-disinfectant to the samples from sewage water.

METHODSTo extract the nucleic acid from phage f(2) and phage with broad host range using anti-serum-carbamidine hydrochloride assay. Purity with agarose gel electrophoresis was then evaluated. Differences of nucleic acid sequence between phage f(2) and phage with broad host range with reverse transcription-polymerase chain reaction (RT-PCR) and random amplified polymorphic DNA (RAPD)-PCR were also comparing and analysed. Through observing the germicidal test of phage f(2) and phage with broad host range to samples from environment, different sterilization effects between the two phages were compared.

RESULTSAnalystic test for nucleic acid revealed that the two phages both belonged to 6000 bp, single-stranded RNA bacteriophage. Significant differences in their specificity of RAPD-PCR and RT-PCR were found during the changed of host range; with 26 RAPD-cDNA differential fragments found that in two phages RAPD-PCR products. The RT-PCR product of phage f(2) was 450 bp cDNA fragment, but the phage with broad host range did not show PCR product. Treating the sewage water with phage under broad host range, the germicidal test showed that the cleaning rate of E. coli bacteria and phage f(2) in water samples from environment could reach 36.75% - 56.28%, 30.84% - 47.96%, 19.19% - 35.06% and 13.05% - 27.85%, respectively.

CONCLUSIONThe cleaning rates to E. coli and bacteria by phage with broad host range were obviously higher than phage f(2) (P = 0.000). Analytic test for nucleic acid indicated that host-specific lytic effect of phage with broad host range had been changed at genetic level.