Isolation and Diagnosis of Salmonella Typhimurium from Pigeon (Columba livia domestica) with Diarrheal Disease in Thi-Qar Province, Iraq

Abstract

Salmonella enterica serovar typhimurium is a major avian enteric pathogen and zoonotic agent, which has considerable veterinary and public health impacts. The synanthropic nature of pigeons may contribute to the spread of multidrug-resistant Salmonella, but their epidemiology in salmonellosis is poorly understood.

Aim: This study aims to detect and isolate S. typhimurium from diarrheic pigeons, to study the antibiotic resistance patterns of the isolated S. typhimurium, and to evaluate the public health issues obtained by the results of the study.

Methods: 100 samples of diarrheic pigeon's fecal matter were aseptically collected. These were cultured on nutrient agar, and then subcultured on Xylose Lysine Deoxycholate (XLD) agar and Salmonella-Shigella agar (SSA). Potential Salmonella colonies were identified by appearance and confirmed using the VITEK 2 identification system. Drug susceptibility patterns were determined and Fisher's exact test was used to measure statistical significance.

Results: Results showed that the most common isolate was Escherichia coli (70%), followed by Klebsiella (15%), Enterobacter spp. (10%), and Salmonella Typhimurium (5%). S. typhimurium appeared as red colonies with a black centre (hydrogen sulfide production) on XLD agar media. A high level of multidrug resistance was observed. Full resistance (100%) was found against Fosfomycin 200 µg, Ampicillin 10 µg, Cefotaxime 30 µg, Gentamicin 10 µg, Trimethoprim-Sulfamethoxazole 1.25/23.75 µg, Ciprofloxacin 5 µg, Amoxicillin-Clavulanic acid 20/10 µg and Imipenem 10 µg (p < 0.05). Resistance to Levofloxacin 5 µg (80%), Streptomycin 10 µg (80%), Ceftazidime 30 µg (80%) and Doxycycline  30 µg (60%) was not significant (p > 0.05). Conclusion: Diarrheal disease can be caused by multidrug-resistant S. typhimurium in pigeons, suggesting the animals may serve as a reservoir and spreaders of resistant strains. Combining selective media with the VITEK 2 system was a successful strategy. These results highlight the importance of ongoing surveillance of avian salmonellosis, biosecurity, and appropriate use of antibiotics to reduce the zoonotic risk associated with resistant Salmonella