Molecular Characterization of Bacteria Isolated from Urinary Tract Infections and Detection of Antibiotic Resistance Genes

Abstract

The study aimed to identify the causative agents of urinary tract infections in patients with urinary tract stones.

A total of 50 urine samples were collected from patients with urinary tract stones, comprising 30 samples from females and 20 samples from males. Blood agar and MacConkey agar media were used for culturing the samples by the streaking method. Following the incubation period, 20 bacterial isolates were obtained, including 17 Gram-negative isolates and 3 Gram-positive isolates. The study was conducted from January 2018 to March 2019.

The results showed that females had a higher incidence of bacterial infections causing urinary tract infections among patients with urinary tract stones. The total number of isolates obtained from females was 16 out of 20, representing 80%, whereas 4 isolates out of 20 were obtained from males, representing 20%.

The study also demonstrated that Escherichia coli (E. coli) was the most prevalent bacterial pathogen among patients with urinary tract stones, with 9 isolates out of 20 (45%). Proteus mirabilis ranked second, with 4 isolates out of 20 (20%), while Staphylococcus spp. ranked third, with 3 isolates (10%). Klebsiella ranked fourth, with 2 isolates (10%), whereas Proteus and Salmonella ranked last, with one isolate each out of 20 (5%).The disc diffusion method was used to assess antimicrobial susceptibility. Ten antibiotics were used for Gram-negative bacteria, while seven antibiotics were used for Gram-positive bacteria. The diameter of the inhibition zone was measured in millimeters, and the results were compared and classified as either susceptible (S) or resistant (R) according to the international standards of the Clinical and Laboratory Standards Institute (CLSI, 2017).

The results demonstrated differences in the inhibitory activity of the tested antibiotics against the isolated bacterial species, with some antibiotics showing relatively low inhibitory effects.

Ciprofloxacin produced the highest inhibition rate, reaching approximately 75% against Gram-negative bacteria. It also showed the highest inhibitory effect against Gram-positive bacteria, with an inhibition rate of 100%.

In contrast, trimethoprim showed the lowest effect against Gram-negative bacteria, with an inhibition rate of 0%, while penicillin showed the lowest effect against Gram-positive bacteria, also with an inhibition rate of 0%. The effects of the other antibiotics ranged between these values, as presented in the tables accompanying the study.