title: Effect of enrofloxacin in the carrier stage of Haemophilus parasuis in naturally colonized pigs.
abstract: The purpose of this study was to determine the effect of enrofloxacin in the carrier stage of Haemophilus parasuis in naturally colonized weaned pigs. Twenty-three pigs colonized by H. parasuis received either 7.5 mg/kg body weight (BW) of enrofloxacin or a saline solution intramuscularly at weaning. Nasal and tonsillar swab samples were collected daily throughout the study and at necropsy and tested by quantitative polymerase chain reaction (qPCR). The H. parasuis isolates obtained from samples collected at necropsy were subjected to genotyping by enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) and a multiplex PCR for the detection of the virulence-associated trimeric autotransporter (vtaA) genes. Haemophilus parasuis was detected in the nasal cavity and tonsils of pigs in the control group throughout the study. Antibiotic-treated pigs tested negative for H. parasuis at 1 d post-treatment and the proportion of nasal samples that tested positive was higher for control pigs than for treated pigs at 1, 2, 3, 4, 5, 6, and 7 d post-treatment and at 2, 4, and 5 d post-treatment for tonsil samples (P < 0.003). Genotyping by ERIC-PCR demonstrated that pigs were colonized with a common H. parasuis strain at the end of the study. Isolates were negative for the vtaA gene, which indicates the absence of vtaA virulence factor. In conclusion, enrofloxacin significantly reduced the H. parasuis load in naturally colonized pigs, but was unable to completely eliminate the organism.
authors.affiliation: Swine Disease Eradication Center, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota 55108, USA (Macedo, Rovira, Oliveira, Torremorell); Bayer Animal Health, Shawnee, Kansas, USA (Holtcamp).
authors.forename: Nubia
authors.initials: N
authors.lastname: Macedo
authors.affiliation: Swine Disease Eradication Center, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota 55108, USA (Macedo, Rovira, Oliveira, Torremorell); Bayer Animal Health, Shawnee, Kansas, USA (Holtcamp).
authors.forename: Albert
authors.initials: A
authors.lastname: Rovira
authors.affiliation: Swine Disease Eradication Center, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota 55108, USA (Macedo, Rovira, Oliveira, Torremorell); Bayer Animal Health, Shawnee, Kansas, USA (Holtcamp).
authors.forename: Simone
authors.initials: S
authors.lastname: Oliveira
authors.affiliation: Swine Disease Eradication Center, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota 55108, USA (Macedo, Rovira, Oliveira, Torremorell); Bayer Animal Health, Shawnee, Kansas, USA (Holtcamp).
authors.forename: Andrew
authors.initials: A
authors.lastname: Holtcamp
authors.affiliation: Swine Disease Eradication Center, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota 55108, USA (Macedo, Rovira, Oliveira, Torremorell); Bayer Animal Health, Shawnee, Kansas, USA (Holtcamp).
authors.forename: Montserrat
authors.initials: M
authors.lastname: Torremorell
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D002353:Carrier State; D000077422:Enrofloxacin; D024841:Fluoroquinolones / Q000627:therapeutic use*; D006192:Haemophilus Infections / Q000188:drug therapy / Q000662:veterinary*; D044137:Haemophilus parasuis / Q000302:isolation & purification* / Q000472:pathogenicity; D013552:Swine; D013553:Swine Diseases / Q000188:drug therapy* / Q000382:microbiology; D014774:Virulence
chemical_list: D000907:Antibodies, Bacterial; D024841:Fluoroquinolones; D000077422:Enrofloxacin