Determination of antibiotic resistance (phenotype and genotype) of Pasteurella multocida isolated from swines

Abstract

We investigated the antimicrobial susceptibility of 83 P. multocida strains with 15 different antibiotics. The studied results showed that P. multocida strains were resistant to amoxicillin (75.9%), tetracycline (59%), and followed by kanamycin (15.7%), amikacin (15.7%), gentamicin (14.5%), ampicillin (9.6%) and erythromycin (9.6%). Less than 5% of the strains were resistant
to chloramphenicol (4.8%). All of the 83 strains were susceptible to: cephalexin, cefortaxime, ceftriaxone, ofloxacin, pefloxaxin, ciprofloxacin and enrofloxaxin. The results of Polymerase Chain Reactions (PCR) detecting ampicillin, gentamicin, chloramphenicol and tetracycline resistance
genes showed that 63 out of 83 P. multocida strains carried at least one of four antibiotic resistance genes. Among 83 strains tested: 12 strains harbored Bla_TEM and/or Bla _ROB1gene; 5 strains possessed floR resistance gene; 52 strains carried at least one of three tetracycline resistance genes (tetB, tetH, and tetO), of which tetB resistance gene was the most prevalent (38/52),
followed by tetH (18/52) and tetO (4/52) resistance genes; and 12 strains were positive for aacA. There were 8 out of 63 strains carried several antibiotic resistance genes in each. There was a positive correlation between phenotype and genotype in the strains resistant to gentamicin and tetracycline as 7 out of 12 strains resistant to gentamicin carried aacA gene and 39 out of 49 strains
resistant to tetracycline harbored at least one of three resistance genes (tetB, tetH and tetO).