Antimicrobial resistance patterns and genetic determinants of emerging Gallibacterium anatis isolates from poultry in...

Gallibacteriosis is a disease in poultry caused by the bacterium Gallibacterium anatis that can lead to respiratory disorders or decreased production. This bacterium causes infections that are similar to those caused by other bacteria, which may lead to misdiagnosis. Infections caused by G. anatis are increasingly associated with reduced susceptibility to antibiotics.

This study aimed to investigate the antibiotic resistance, antibiogram profile, and antibiotic resistance genes associated with emerging G. anatis infections in poultry.

Using a targeted sampling method, G. anatis was isolated from broiler, layer, and breeder chickens exhibiting respiratory disorders and reduced egg production in eight poultry farms in West Java, Indonesia. Bacteriological isolation was performed, and the recovered isolates were subsequently tested for antimicrobial susceptibility by determining the minimum inhibitory concentration (MIC) and by polymerase chain reaction (PCR)-based detection of antibiotic resistance genes.

A total of 14 G. anatis isolates were obtained. The resistance profiles indicated that resistance was present in the tetracycline (TET), quinolone, and β-lactam groups. TET, ciprofloxacin, and levofloxacin antibiotics had the highest rates of resistance at 100%. Furthermore, 75.14% of the isolated G. anatis were multidrug- resistant. None of the isolates experienced resistance to amikacin, gentamicin, tigecycline, imipenem, tobramycin, and piperacillin (0%). The multiple antibiotic resistance index ranged from 0.13 to 0.59. PCR revealed that the G. anatis isolate in this study carried the following genes: gyr(A) (100%), tet(B) (92.85%), blaSHV (87.5%), and qnrA (85.71%).

Antibiotic resistance testing of G. anatis using the MIC method revealed that many isolates were resistant to tetracyclines, β-lactams, and quinolones, which was supported by the detection of the resistance genes tet(B), blaSHV, gyrA, and qnrB. This study advances the understanding of antibiotic resistance in G. anatis strains circulating in Indonesia, highlighting resistance to antibiotics commonly used in poultry and human medicine.