Phage Conversion in Salmonella typhi

Abstract

Objective and background: This work aimed to convert Chloramphenicol resistant S. typhi into sensitive state genetically through transduction since Chloramphenicol resistant S. typhi is increasing all around the world.Methodology: sixty patients were the subjects of this work. Each specimen collected from blood samples of having typhoid fever was subjected to well known microbiological methods for isolation and identification of S. typhi ,30 isolates of S. typhi were tested for sensitivity or resistance to the commonly used drug employing Kirby-Bauer technique, cross-lysis technique is followed to determine the sensitive isolates. Transduction was performed by mixing a phage lysates of certain isolates in separated system followed by expression on selective media. Antibiotics sensitivity test were performed looking for converted S. typhi.Results: Out of 60 bloods collected from attending Sulaimayiah teaching hospital 30 isolates of S. typhi were obtained. Testing all isolates for antimicrobial susceptibility using Kirby-bauer disc diffusion method revealed that 93.3% of the isolates were Chloramphenicol resistant. Multidrug resistance in addition of Chloramphenicol have been observed in which the resistant pattern of S. typhi isolates showed Streptomycin is 86.6% ,Tetracycline 66.6%,Ampicillin 86.6%, Amoxicillin 80%, Ciprofloxacin 33.3% and Rifampicin 73.3%. Phages were induced [1] from Chloramphenicol sensitive isolates no 7 and 8. Employing cross-lysis [2] technique it has been found that isolates no.16 and 23 Chloramphenicol resistant S. typhi can be considered as indicator strains, In this work through application of transduction it was been found that Chloramphenicol resistant isolates no.16 and 23 were converted to Chloramphenicol sensitive ones following infection by phages induced from Chloramphenicol sensitive isolates no 7 and 8 respectively. Antibiotics sensitivity test were performed for all isolates treated with phage lysate looking for converted isolates.Conclusion: It is concluded that Chloramphenicol resistant S. typhi were converted to Chloramphenicol sensitive S. typhi through transduction by phages from Chloramphenicol sensitive isolates. Keyword: Transduction, Chloramphenicol resistance S. typhi