Detection of Mutations in Ciprofloxacin Resistant Salmonella Enterica serotypes typhi and Paratyphi A

Background: Typhoid fever is a systemic infection caused by Salmonella species. Fluoroquinolones are mostly the antibiotic of choice for treatment. Resistance to ciprofloxacin has been noticed to increase due to the emergence of new mutations in bacterial DNA. Aims: Analyse the plasmid DNA profile and to detect any mutations in DNA gyrase responsible for ciprofloxacin resistance. Methods: In clinical isolates 160 were Salmonella typhi and 132 were Salmonella paratyphi A collected over five years. The antimicrobial susceptibility was studied. DNA sequencing of gyrA, gyrB, and parC genes was performed in 8 isolates. Results: Four enteric fever Salmonella isolates in the present study showing ciprofloxacin MIC of 1µg/ml and 4 other randomly chosen isolates with MIC < 1µg/ml were subjected for molecular sequencing by PCR. The 4 ciprofloxacin resistant strains showed a point mutation (CT or CA) at 128 th base corresponding to amino acid sequence change of SerTyr or SerPhe at 83 rd position, which was not detected in other 4 strains. Plasmid DNA analysis did not reveal any abnormal R-Plasmid. Conclusions: It is very important to keep searching for new mutations and continuously monitor drug resistance in order to efficiently