Abstract

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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.

Keywords: Quinolone, GyrA gene, Resistant, Mutation Salmonella serovar Typhi