title: Serovar identification, antimicrobial sensitivity, and virulence of Avibacterium paragallinarum isolated from chickens in Thailand.
abstract: Avibacterium paragallinarum causes infectious coryza in chickens, an acute respiratory disease that has worldwide economic significance. The objectives of this study were to determine the serovars, antimicrobial resistance, and pathogenicity of A. paragallinarum isolated from chickens in Thailand. Eighteen field isolates of A. paragallinarum were confirmed by PCR. When examined by serotyping in a hemagglutination inhibition test, 10 isolates were serovar A, five isolates were serovar B, and three isolates were serovar C. The susceptibility of the isolates to 16 antimicrobial agents was tested by a disk diffusion method. All isolates were susceptible to amoxicillin-clavulanic acid. There was a high level of resistance to lincomycin and erythromycin. All isolates were resistant to cloxacillin and neomycin. A study of bacterial entry into, and survival within, chicken macrophages showed variation between isolates but no clear connection to serovar. A virulence test was performed by challenging 4-wk-old layers via the nasal route with 400 dl of bacteria (10(8) colony-forming units/ml). Clinical signs were observed daily for 7 days, and the birds were subjected to a postmortem necropsy at 7 days postchallenge. All 18 field isolates caused the typical clinical signs of infectious coryza and could be re-isolated at 7 days after challenge. There was no significant difference in the clinical scores of the isolates except that two isolates (112179 and 102984, serovars A and B, respectively) gave a significantly higher score than did isolate CMU1009 (a serovar A isolate). No correlation between serovar and severity of clinical signs was found.
authors.affiliation: Avian Health Research Unit, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Kridda
authors.initials: K
authors.lastname: Chukiatsiri
authors.forename: Jiroj
authors.initials: J
authors.lastname: Sasipreeyajan
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Blackall
authors.forename: Sommai
authors.initials: S
authors.lastname: Yuwatanichsampan
authors.forename: Niwat
authors.initials: N
authors.lastname: Chansiripornchai
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology; D002460:Cell Line; D002642:Chick Embryo; D002645:Chickens; D004196:Disease Outbreaks / Q000662:veterinary; D024881:Drug Resistance, Bacterial; D005260:Female; D005347:Fibroblasts / Q000382:microbiology; D006192:Haemophilus Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D044134:Haemophilus paragallinarum / Q000145:classification* / Q000187:drug effects / Q000302:isolation & purification / Q000472:pathogenicity*; D006386:Hemagglutination Tests / Q000662:veterinary; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D009569:Nitric Oxide / Q000378:metabolism; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011201:Poultry Diseases / Q000453:epidemiology / Q000382:microbiology*; D012703:Serotyping / Q000662:veterinary; D013785:Thailand / Q000453:epidemiology; D014774:Virulence
chemical_list: D000890:Anti-Infective Agents; D009569:Nitric Oxide