Modifying Plaque assay and Clearance test as tools in determination of phage typing for Escherichia coli bacterial interspecies


Bacteriophage of Escherichia coliinterspecies from sewage samples were isolated , The phage particles were isolated from two different sewage samples , First sample was collected from sewage sample of Baghdad university and second sample was isolated from domestic sewage sample , first sample showed phages specialized for three E. Coli interspecies bacteria (first plate ) and two E. Coli interspecies bacteria (second plate ) , meanwhile second sample showed phage specialized for two E. Coli. interspeciesStudy of appearance of Escherichia coli phages from first sample showed three types of E. coli phages with different size of inhibition zone 2 , 1.5,1 mm respectively ( first plate ) , meanwhile E. Coli interspecies bacteria showed phages related with two interspecies with size of inhibition zone 1.5 ,1 mm respectively ( second plate ), on other hand , The second sample showed also two interspecies E. coli with inhibition zone (1,2)mm . We designed experimental method which showed the modifying method of phage assay to determine phage typing assay .We tested phage particles with different bacterial strains ( E. coli , shegilla and Serratia ) from different sources and the control was the host of each bacteriophages by taking the O.D for all the tests and controls , to setup new criteria for phage typing .:and this test is called ( Clearance Test ) The result showed that O.D for Test 1 , 2 , 3, was ( 1.6 , 1.2 . 1.7) for ( E. coli , shegilla and Serratia ) bacterial strains , meanwhile the control tests was ( 0.3 , 0.2, 0.4 ) for strains isolated from first sample (first and second plate ) and second samples with different interspecies respectively . This result can predict high specificity of phage strain and this method can be used to determine interspecies strains .So from this experimental we can identify only Clearance Test by measuring only O.D. of bacterial strain with different phages a instead of going through plaque assay .