Tetracycline Resistance in Diarrheagenic Escherichia coli in Southern Iran

Backgrounds: Diarrhea is a predominant contributor to childhood mortality in developing nations, particularly among those under the age of five. Diarrheagenic Escherichia coli is one of the main causes of endemic and epidemic diarrhea worldwide. This study aimed to assess the frequency of antibiotic resistance and tetracycline resistance genes in diarrheagenic E. coli strains obtained from children under five years of age.
Materials & Methods: 550 pediatric fecal samples were obtained from the laboratory archives of three Shiraz hospitals between April 2018 and December 2019. Bacteria were isolated and identified using standard bacteriological procedures. Antimicrobial susceptibility testing was performed using the disk diffusion method according to CLSI (Clinical and Laboratory Standards Institution) 2019 guidelines. Molecular analysis of tetracycline resistance genes (tetA, tetB, and tetC) was performed using multiplex PCR.
Findings: A total of 112 diarrheagenic E. coli strains were isolated. Antibiogram analysis revealed a high antibiotic resistance to tetracycline (57.1%) and the lowest antibiotic resistance to amikacin and nitrofurantoin (3.3%). Ninety-three (83%) isolates showed a multidrug-resistance (MDR) pattern. Of the 64 tetracycline-resistant isolates, 56 (87.50%) contained tetracycline resistance genes. The frequencies of tetracycline resistance genes tetA, tetB, and tetC in tetracycline-resistant isolates were 58.9, 44.6, and 14.3%, respectively.
Conclusion: Tetracycline-resistance is more common among diarrheagenic E. coli strains. Furthermore, resistance to antimicrobial agents is more common in E. coli strains isolated from pediatric patients and is correlated with increased antibiotic use among patients with gastroenteritis. However, the influence of unsupervised antibiotic administration on specific antibiotics remains unclear.