Detection of DNA Gyrase Mutation among Clinical and Environmental Isolates of Salmonella enterica Serovar Typhi from Some Parts of Adamawa State, Nigeria

The emergence of quinolone resistance among Salmonella enterica serovar Typhi is a growing  concern in the treatment and management of typhoid fever especially in developing countries. The  quinolone resistance is attributed to point mutation in GyrA gene of the organism. This study was aimed at  identifying the occurrence of point mutation in the GyrA gene of Salmonella Typhi from some parts of  Adamawa state. Results from the study showed that only 30% of the isolates from the study area were  susceptibly to ciprofloxacin while 45% demonstrated reduced susceptibility to it. Two isolates S. Typhi  MUB34 and S. Typhi GMB 1 bored plasmids coding for resistance to nalidixic acid. BLAST sequence  analysis of the GyrA gene with reference S. Typhi isolate from the NCBI website revealed that 14 (56%) of  the isolates had point mutations at position 83-serine while 6 (24%) had mutation at position 87. Further  observation of the mutation pattern indicated that 12 (48%) of isolates had single point mutation at position  ser 83 while 4(16%) had double mutation at points 83 and 87 of QRDR of gyrA gene. The remaining  isolates had no point mutations in the gyrA gene at either position 83 or 87. The mutation observed in the  QRDR of GyrA gene of Salmonella enterica Typhi will mean that the selection of fluoroquinolones for  treatment of S. Typhi in the study area must be done with caution to avoid treatment failure. This is  because the presence of single mutation in the Gyr A gene is associated with reduced susceptibility to  quinolone antibiotic while double mutation confers resistance to quinolones.