Phylogenetic analysis and antibiotic resistance of Escherichia coli isolated from wild and domestic animals at an agricultural land interface area of Salaphra wildlife sanctuary, Thailand

Background and Aim: Domestic and wild animals are important reservoirs for antibiotic-resistant bacteria. This study aimed to isolate Escherichia coli from feces of domestic and wild animals at an agricultural land interface area of Salaphra Wildlife Sanctuary, Thailand, and study the phylogenic characteristics and antibiotic resistance in these isolates.

Materials and Methods: In this cross-sectional, descriptive study, we randomly collected ground feces from free-ranging wild animals (deer and elephants) and domestic animals (cattle and goats). All fecal samples were inoculated onto MacConkey agar plates, and lactose-fermenting colonies were identified as E. coli. Antibiotic susceptibility of the E. coli isolates was determined using the disc diffusion method. Polymerase chain reaction assays were used to detect antibiotic resistance and virulence genes.

Results: We obtained 362 E. coli isolates from the collected fecal samples. The E. coli isolates were categorized into four phylogenetic groups according to the virulence genes (chuA, vjaA, and TspE4C2). Phylogenetic Group D was predominant in the deer (41.67%) and elephants (63.29%), whereas phylogenetic Group B1 was predominant in the cattle (62.31%), and phylogenetic Groups A (36.36%) and B2 (33.33%) were predominant in the goats. Antibiotic susceptibility testing revealed that most antibiotic-resistant E. coli were isolated from domestic goats (96.96%). Among the 362 E. coli isolates, 38 (10.5%) were resistant to at least one antibiotic, 21 (5.8%) were resistant to two antibiotics, and 6 (1.66%) were resistant to three or more antibiotics. Ampicillin (AMP) was the most common antibiotic (48.48%) to which the E. coli were resistant, followed by tetracycline (TET) (45.45%) and trimethoprim-sulfamethoxazole (3.03%). One isolate from an elephant was resistant to five antibiotics: AMP, amoxicillin, sulfisoxazole, TET, and ciprofloxacin. Determination of antibiotic resistance genes confirmed that E. coli isolates carried antibiotic resistance genes associated with phenotypic resistance to antibiotics. Most antibiotic-resistant E. coli belonged to phylogenic Groups A and B1, and most non-resistant E. coli belonged to phylogenic Groups B2 and D.

Conclusion: Monitoring E. coli isolates from wild and domestic animals showed that all four phylogenic groups of E. coli have developed antibiotic resistance and are potential sources of multidrug resistance. High levels of antibiotic resistance have been linked to domestic animals. Our results support strengthening surveillance to monitor the emergence and effects of antibiotic-resistant microorganisms in animals.