2 research outputs found
Antimicrobial susceptibility patterns of Brazilian Haemophilus parasuis field isolates
12 p.Haemophilus parasuis is the etiological agent of Glässer’s disease (GD), an ubiquitous infection of swine
characterized by systemic fibrinous polyserositis, polyarthritis and meningitis. Intensive use of antimicrobial
agents in swine husbandries during the last years triggered the development of antibiotic resistances in bacterial
pathogens. Thus, regular susceptibility testing is crucial to ensure efficacy of different antimicrobial agents to
this porcine pathogen. In this study, 50 clinical isolates from South Brazilian pig herds were characterized and
analyzed for their susceptibility to commonly used antibiotic. The identification and typing of clinical isolates
was carried out by a modified indirect hemagglutination assay combined with a multiplex PCR. The susceptibility
of each isolate was analyzed by broth microdilution method against a panel of antimicrobial compounds. We
found that field isolates are highly resistance to gentamycin, bacitracin, lincomycin and tiamulin, but sensitive to
ampicillin, clindamycin, neomycin, penicillin, danofloxacin and enrofloxacin. Furthermore, an individual
susceptibility analysis indicated that enrofloxacin is effective to treat clinical isolates with the exception of those
classified as serovarS
Altered indirect hemagglutination method for easy serotyping of Haemophilus parasuis
P. 15-21Glässer’s disease is an emergent bacterial disease that affects swine husbandries worldwide causing
important economic losses. The aetiological agent, Haemophilus parasuis, is currently divided in fifteen
serovars but an increasing number of non-typeable serovars have been reported. Indirect
hemagglutination (IHA) is indicated as a serotyping method for H. parasuis. In the present study, we
describe an additional step that aims to work around a possible obstacle in the original protocol that may
compromise the outcome of this assay. We observed that the choice of anticoagulant for blood collection
influences and/or impairs spontaneous adsorption of H. parasuis antigens on sheep red blood cells
(SRBCs). However, regardless of the anticoagulant used, chemical treatment of SRBCs with tannic acid
induces a stable antigen adsorption (sensitization step). The addition of 1% BSA to SRBCs washing
buffer and to antisera dilution augments IHA specificity. Tannic acid treated SRBCs combined with
thermo-resistant H. parasuis antigens increases the assay resolution. Thus, our results demonstrate an
improvement in the technique of H. parasuis serotyping that will prove valuable to understand Glässer’s
disease epidemiology and to better characterize serovars involved in outbreaksS