Antimicrobial susceptibility of Haemophilus parasuis isolated from swine

Abstract

This study was conducted to determine the antimicrobial susceptibility of H. parasuis isolated from the nasal fluid and lung samples of pigs with respiratory disease symptoms. The minimum inhibitory concentration (MIC) was performed to evaluate the antimicrobial susceptibility of 13 H. parasuis isolates with 13 tested antibiotics according to CLSI guidelines (2018). Up to the present time, according to the reference of the professional journals, this was the first publication in Viet Nam on applying the MIC method to evaluate the antibiotic susceptibility of respiratory pathogens in pigs in general and H.
parasuis in particular. The studied results showed that most of antibiotics had MIC 50 and MIC90 for H. parasuis isolates higher than the break point of the minimum bacterial inhibition concentration (MIC breakpoint) according to CLSI. Most of H. parasuis isolates were susceptible with tylosin, tilmicosin, trimethoprime/ sulfamethoxazole (60%). H. parasuis isolates were susceptible with other antibiotics from 15% to less than 50%. H. parasuis isolates were strongly resistant to amoxicillin, gentamicin, tetracycline and
ceftiofur. This result showed that H. parasuis isolates were still susceptible with the tested antibiotics but at low levels and it is necessary to regularly determine the antibiotic susceptibility of this bacteria for effective treatment.