Caracterização fenotípica e determinação do perfil de sensibilidade antimicrobiana de isolados clínicos de haemophilus parasuis

Abstract

Haemophilus parasuis (HPS), a member of the Pasteurellaceae, is a small gram-negative bacillum that causes Glässer s disease (GD). This pathology is characterized by poliserositis and high mortality rate of infected animals. Modern approaches to swine industry and high sanitary herd conditions contribute to increase the incidence of GD. Up to now, HPS is classified in 15 serotypes of reference, each one having a distinct antigen profile. There are no data about HPS presences, distribution and prevalence in Brazil. This is true also for Southern Brazil (Rio Grande do Sul and Santa Catarina), where pig industry is an important economical source of income. Against this background, we isolated and analyzed 78 samples of swine lungs with pleuritis and confirmed HPS infection by molecular biology. We evaluated the resistance profile of 35 HPS isolates to 10 antimicrobials using the microdilution technique. We further propose a modified protocol for the indirect hemagglutination (IHA) in order to serotype HPS. Our results demonstrate a high prevalence of HPS positive lung samples (44.4%) coming from piglets with signs suggestive of GD. All lungs from finishing pigs collected at slaughter were negative for HPS, however, 18 of them (54.5%) were PCR positive for Actinobacillus pleuropneumoniae. The susceptibility profile to antimicrobials revealed that all isolates were susceptible ceftiofur, gentamycin and erythromycin. A low degree of resistance was observed with ampicillin (2.8%) and moderate with penicillin (11.4%). Kanamycin and lincomycin were effective at the lowest minimal inhibitory concentration (MIC) used. Similar results were obtained with cefalotin. In contrast, bacitracin and sulfatiazol were effective with the highest MICs used. For IHA we obtained from Wistar rats a high titration of polyclonal antibodies against all 15 serotypes. Treating lamb red blood cells with tannic acid (1:20.000) enables a better adhesion of HPS antigens, resulting in a more accurate technique to serotype clinical isolates. In conclusion, the results presented here, demonstrate a high prevalence of H. parasuis in swine farms of southern Brazil and describe a set of effective antimicrobial drugs for the treatment of DG. Lastly, the HIm exhibited suitable sensitivity and specificity for serotyping of H. parasuis, and its main advantage over classical HI, is the greater capacity for adsorption of H. parasuis antigens