Resistance profile study of pathogenic bacteria of genus Escherichia and Salmonella isolated from water environment tested positive for antibiotic residues in Ndjamena, Chad.

Objective: This study has conducted with aim to evaluate the resistance profile of Escherichia and Salmonella bacteria isolated from water environment tested positive for antibiotic in N’Djamena, Chad. Methodology: Isolates (35, including 15 of the Escherichia genus and 20 of the Salmonella genus) from the N'Djamena water environment tested positive for antibiotic residues were studied for their resistance profile. Antibiograms based on the diffusion of antibiotic disks in agar media (Mueller-Hinton Agar (MHA)) on 24-hour cultures were used for this purpose. Results: The proportion of isolates resistant to the antibiotics tested varied. Bacteria of the Escherichia genus were resistant with prevalence over 40% to Imipenem (100%), Ampicillin (93.3%), Amoxicillin (86.7%), Tetracycline (80%), Erythromycin (73.3%), Cotrimoxazole (66.7%) and Chloramphenicol and Cefoxitin (46.7%). This prevalence is less frequent with Amikacin (20%), Gentamicin (13.4%), Ciprofloxacin and Ceftriaxone (6.7%). The Salmonella genus were 95% resistant to imipenem, 65% to tetracycline and erythromycin, 55% to amikacin, 50% to gentamicin and amoxicillin, 45% to cotrimoxazole, 35% to Ampicillin and Ciprofloxacin, 25% to Chloramphenicol and Cefoxitin, 20% to Ceftriaxone, 15% to Chloramphenicol, 10% to Ceftriaxone and Amoxicillin and 5% to Ciprofloxacin and Cotrimoxazole. Conclusion: This study showed a variability of antibiotic resistance in E. coli and Salmonella strains in the water environment containing antibiotic residues in the city of Ndjamena, with resistance proportions ranging from 6.7 to 100% for E. coli and 5 to 95% for Salmonella. This high rate could be due to the presence of antibiotic residues in the water environment, which strongly contribute to the maintenance, emergence and dissemination of bacterial populations with a high level of resistance, ready to evolve towards multi-resistance. Population exposure to antibiotics and inter-individual or inter-animal transmission of resistant strains are therefore likely to be major determinants of the emergence and spread of bacterial resistance to antibiotics, which remains a real public health problem to this day. Surveillance is therefore essential to understand the scale of the problem and monitor its impact.