Isolation and Partial Characterization of Bacteriophages

Abstract

Bacteriophages were isolated from sewage samples obtained from the Tema Sewage Disposal Plant and the Legon vicinity using the indicator bacteria strains Shigella dysenteriae. Salmonella typhi. Escherichia coli, and Salmonella typhi Group D. Ten phages were isolated and partially characterized by electron microscopy, DNA fingerprinting and protein profiles by SDS-PAGE. The relatedness of the phages was determined by immunological studies. Some of the phages were screened for their ability to transduce antibiotic resistance markers. The phages were found to be similar to T-even phages and P phages. The morphology possessed by a phage was independent of the host specificity, which is phages of different morphologies could attack one bacteria strain. The restriction fragment lengths of the phage DNA ranged between 0.125-33.113 kilobasepairs (kbp) and one fragment of fragment length 23.000kbp was common to nine phages, suggesting a relationship between phage nucleic acid and morphologies. Phage EcRCL24 for which antisera was raised was found to show an appreciable cross reactivity with the other EcRCL phages and they are therefore closely related. The phages are presumed to be capable of generalized transduction and the frequency of 3 x 10-6 for penicillin-V sulfoxide and 3 x 10-7 for tetracycline and erythromycin suggests a relatedness of the indicator bacteria strains' chromosomes. The additional information obtained within the scope of the project, involved comparison of minimum inhibitory concentration (MIC) values and those obtained by the induction of increased tolerance levels of antibiotics in the clinical isolates. It showed that, these pathogens could tolerate about double their MIC values in the increased tolerance level experiments. Furthermore their MIC values were considerably higher than the chemotherapeutic dosages.