Antibiotic Resistance in Citrobacter, Isolated in Elderly Patients with Urinary Tract Infections in the Abidjan District, Ivory Coast

Background: Urinary tract infections are common among older adults, and the emergence of antibiotic-resistant Citrobacter spp. complicates therapeutic management. Aims: The objective of this study was to characterise antibiotic resistance genes in Citrobacter isolates from elderly patients presenting with urinary tract infections. Study Design: This was a retrospective study. Place and Duration of Study: The study was conducted at the Bacteriology and Virology Laboratory of the Pasteur Institute, Abidjan, Ivory Coast, from February 2023 to March 2024. Methodology: A retrospective study was conducted using 47 clinical Citrobacter isolates collected at the Institut Pasteur de Côte d’Ivoire. Antimicrobial susceptibility was assessed by disc diffusion, extended-spectrum β-lactamase production was evaluated using a double-disc synergy test, and polymerase chain reaction was used to detect blaTEM, blaSHV, and blaCTX-M-1 genes. Results: Citrobacter strains were isolated from 59.57% of the urine samples. Two species of Citrobacter were identified: Citrobacter freundii 85% (40/47) and Citrobacter koseri 15% (7/47). Generally, a low resistance rate (10.71%) was observed among the Citrobacter isolates in the presence of kanamycin. However, they exhibited a high resistance rate of 89.36% (42/47) to cefixime. Except for amikacin and kanamycin, the susceptibility profile of Citrobacter freundii showed resistance rates of 100% to both cefixime and aztreonam. Regarding Citrobacter koseri, a high resistance rate of 87.5% (35/40) was observed for cefixime, whereas a low resistance rate of 10.63% (5/47) was observed for kanamycin. In this study, the prevalence of Citrobacter strains producing extended-spectrum β-lactamases (ESBL) was 78.72% (37/47). Among the 47 strains, 14.9% (7/47) harbored the blaCTX-M-1 gene, 12.77% (6/47) carried the blaTEM gene, and 4.26% (2/47) possessed the blaSHV gene. Conclusion: The high resistance rates obtained compromise treatment efficacy. Consequently, there is an urgent need to implement surveillance strategies and develop new therapeutic alternatives to address this growing public health threat.