Multidrug resistance is the ongoing burning issue in Salmonella typhi around the whole globe. This study was conducted to investigate changing trends in antibiotics resistance and mechanism of resistance against Nalidixic acid among multidrug resistant Salmonella typhi strains isolated from Islamabad Capital Territory, Pakistan.
Methodology: Prior to blood sampling, demographic data of patients was recorded. A total of 103 clinical isolates from blood of typhoid patients were identified using microbiological techniques such as colony morphology, Gram’s staining and confirmed using standard biochemical techniques. For molecular confirmation, hyper variable region VI of flagellin fliC gene was targeted using PCR. Antibiogram of the isolates was tested by Kirby Bauer disc diffusion method using fifteen regularly used antibiotics. Efficacy of antibiotics was evaluated in respect to various seasons, age groups and gender of patients. Relevant genes gyrA and gyrB were targeted and quinolone resistance determining region (QRDR) of these genes was sequenced to analyze mutations.
Results: Antibiogram study demonstrated that 90.3% isolates were multidrug resistant. 75.7% isolates were sensitive to cefipime while 80.58% were resistant to nalidixic acid. 66.02% isolates were found to be ciprofloxacin resistant exposing reduced susceptibility of salmonella typhi to fluoroquinolones. Molecular studies revealed a single point mutation with substitution of serine-83 by phenyl-alanine. This single point mutation seems to be responsible for resistance against nalidixic acid in S. typhi.
Conclusion: The incidence of typhoid is high in Islamabad with significant resistance of S. typhi isolates against currently administrated antibiotics due to the presence of one point mutation. Therefore, it must be mandatory for the health care professionals to test for the antibiogram before prescribing appropriate antibiotics.
Muhammad Zubair Saleem, Abida Arshad, Mazhar Qayyum, Muhammad Imran Shabbir, Aamir Ali, Ishfaq Ahmad and Muhammad Arshad