The prevalence of trimethoprim-resistance-conferring dihydrofolate reductase genes in multidrug resistant bacteria from clinical isolates in Malaysia

Yu, Lee Wen (2024) The prevalence of trimethoprim-resistance-conferring dihydrofolate reductase genes in multidrug resistant bacteria from clinical isolates in Malaysia. Final Year Project, UTAR.

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Abstract

Antibiotic resistance has been a global issue since the appearance of drug-resistant microorganisms. With the limited medicines available, the treatment of bacterial infections is now at risk of failure. Trimethoprim is commonly used as a first- or second-line antibiotic in combination with sulfamethoxazole to treat uncomplicated urinary tract infections. However, the rising rate of antibiotic resistance renders this affordable drug ineffective. Gram-negative bacteria typically develop resistance to trimethoprim-sulfamethoxazole by gaining the dfr and sul genes, which are transferable between bacteria. The dfr genes are frequently found on the gene cassette located on the integron. The purpose of this study was to investigate the prevalence of dfrA genes in 60 clinical bacterial isolates, as well as their antimicrobial susceptibility to seven antibiotics from five classes: β-lactam combination agents, folate pathway antagonists, quinolones, aminoglycosides, and polymyxin. Triplex polymerase chain reaction (PCR) was performed to detect the presence of dfrA genes in total DNA extracted using the fast boil method. The susceptibility of the isolates was then determined using the Kirby-Bauer disc diffusion method. The antimicrobial susceptibility data revealed that 76.67% of the bacterial isolates were resistant to amoxicillin-clavulanic acid, 70.00% to trimethoprim-sulfamethoxazole, 68.33% to ciprofloxacin, 61.67% to nalidixic acid, 18.33% to tobramycin, 8.33% to netillin, and 5.00% to polymyxin B. In triplex PCR, eight isolates were positive for dfrA1 (13.33%), nine for dfrA7 (15.00%), and none for dfrA17. Co-carriage of the dfrA genes was not seen. The Chi-square or Fisher's exact test was used to evaluate the association between the dfrA genes and trimethoprim-sulfamethoxazole resistance, as well as the patient's age and gender. The findings indicate that dfrA7 was positively associated with ciprofloxacin and trimethoprim-sulfamethoxazole resistance. However, the patient's age and gender showed no significant association with the presence of dfrA genes.

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