Introduction: Gallibacterium anatis a Gram-negative bacteria which can be transmitted horizontally and vertically. In birds it is constitutes as part of the normal microflora in the occurrence with the coexistence of other relevant factors leads to serious economic losses in the poultry industry (1). G. anatis biovar haemolytica is a bacteria causing salpingitis, peritonitis, drop in egg production, and also respiratory signs (2–4).
Methods: In this study, 18 isolates obtained from laying hens from the respiratory and reproductive systems were selected. G. anatis biovar haemolytica was identified by MALDI TOF after culturing on Columbia agar with 5% sheep blood and PCR. The susceptibility of G. anatis biovar haemolytica to 11 different antimicrobials (Oxoid discs) was carried using bacterial dose of 100 uL of 1.5 × 107 CFU/mL (0.5 McFarland scale) distributed uniformly onto the Columbia agar 5% blood. The inhibition zones were interpreted visually. Plates containing different concentrations of 6 different antibiotics were also used to determine MIC (Sensititre). In addition, isolates of G. anatis biovar haemolytica were tested for virulence gene  gyrB and antibiotic resistance genes (blaROB, fifA1, tetB) by PCR (4).
Results: The most prevalent antibiotic resistances were Tilmicosin, Tylosin  and Enrofloxacin  followed by Erythromycin, Tetracycline, Ciprofloxacin, Teicoplanin and Vancomycin. Multiple resistance to at least 12 antibiotics occurred in 33.3% of isolates while 100% of isolates showed multiple resistance to at least 9 antibiotics. The occurrence of virulence gen gyrB  was in 72%.  The antibiotic genes, detected by PCR, was 100 % for tetB, 6 % for  blaROB and  60 % for fifA1.
Conclusions: Of great concern is the high antibiotic resistance of the tested strains of G. anatis biovar haemolytica obtained from chicken flocks. Due to the constant variability of antibiotic resistance of these bacteria over the years, therefore, it seems reasonable to periodically control their occurrence in poultry flocks.