Molecular characterization of avian pathogenic Escherichia coli isolates from broiler farms in Northern Palestinian territories

Abstract

Background and aim: Colibacillosis is caused by avian pathogenic Escherichia coli (APEC), which results in significant losses for the poultry sector. It has zoonotic potential and acts as a source of antibiotic resistance and virulence genes for other E. coli. This study aimed to assess phylogenetic groups, virulence factors, and resistance phenotypes of APEC strains isolated from broiler farms in Northern Palestine.

Materials and methods: A total of 65 APEC isolates were recovered from diseased chickens with typical colibacillosis symptoms from broiler farms located in the northern region of Palestine from May to July 2024. Strains were identified using classical and molecular techniques. Antibiotic resistance was detected using the disk diffusion method. Phylotyping and virulence genotyping of the APEC isolates were performed using a polymerase chain reaction (PCR).

Results: This study showed a high detection rate of APEC strains (100%) in chickens. The most APEC strains, 56/65 (86.2%), belonged to group D. Other strains were assigned to groups B2 (5/65, 7.7%), B1 (3/65, 4.6%), and A (1/65, 1.5%). Antibiotic resistance ranged from 27.7% for Polymyxin E (colistin) to 100% for Amoxicillin. Polymyxin E (colistin) and fosfomycin are the most effective drugs. The most common virulence gene was iroN, which was detected in 61 isolates (93.8%). The APEC strains in Palestine exhibit a wide variety of resistance patterns and genetic variations.

Conclusion: Controlling APEC infections is essential for public health, especially when APEC isolates can pass on resistance and virulence genes to dangerous bacteria such as E. coli that are particular to humans. It is essential to understand APEC pathogenesis, antimicrobial therapy, and the development of measures to control colibacillosis.

Keywords: Palestinian territories; antibiotic resistance; avian pathogenic Escherichia coli; colibacillosis; phylogenetic group; virulence factors.

Figure-1

The polymerase chain reaction (PCR) product of Escherichia coli-specific phoA gene. Lane L: 100-bp ladder, lanes 1-10 the PCR product (622-bp) band of E. coli-specific phoA gene.

Figure-2

Phylogenetic groups of avian pathogenic Escherichia coli isolates recovered from broiler farms in Northern Palestine using Triplex polymerase chain reaction. Phylogenetic group D2 included lanes 1-6 and 10; Group D1 included lanes 7 and 8; Group B2 included lane 9; and lanes L comprised a 100-bp ladder.

Figure-3

Dendrogram of 65 APEC strains isolated from broiler farms in Northern Palestine based on the UPGMA method derived from analysis of the antibiotic resistance profile and Phylogenetic groups. Intermediate antibiotic results for APEC isolates indicate resistance. APEC=Avian pathogenic Escherichia coli, N=Neomycin sulfate, CT=Colistin sulfate, PB=Polymyxin B, DO=Doxycycline, FFC=Florfenicol, CL=Cephalexin, CN=Gentamicin, FUR=Ceftiofur, AX=Amoxicillin, NOR=Norfloxacin, ENR=Enrofloxacin, CIP=Ciprofloxacin, CRO=Ceftriaxone, STX=Sulfamethoxazole/Trimethoprim, FO=Fosfomycin, C=Cluster.

Figure-4

Multiplex polymerase chain reaction profiles specific to the avian pathogenic Escherichia coli virulence factors. Lane L has a 100-bp ladder. A: The genes utaA (302-bp), tsh (420-bp), hlyF (599-bp), and iroN (667-bp) are shown in Lanes 1, 2, 3, and 4. B: The papGII (190-bp) and papGI (461-bp) genes are shown in lanes 1, 3, 4, and 5.. C: The papC (501-bp) and cva/cvi (598-bp) are shown in lanes 1, 2, and 3.

Figure-5

Dendrogram of 65 avian pathogenic Escherichia coli strains isolated from broiler farms in Northern Palestine based on the UPGMA method derived from analysis of the virulence factor profile and phylogenetic groups.