Antimicrobial susceptibility patterns of Brazilian Haemophilus parasuis field isolates

Abstract

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 21 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 serovar 1. The results presented here firstly demonstrate the susceptibility of Brazilian clinical isolates of H. parasuis to antimicrobials widely used by swine veterinary practitioners and strengthen the need to perform susceptibility test prior to antibiotic therapy during GD outbreaks. In addition, because only six antimicrobial drugs (28.6%) were found effective against field isolates, a continuous surveillance of the susceptibility profile should be of major concern to the swine industry.

The amino acid selected for generating mutant TbpB antigens defective in binding transferrin can compromise the in vivo protective capacity

“…Six conventional male piglets (Large-White × Landrace) of 42 days of age, negative for H. parasuis [Microbiologically: upper respiratory tract free of H. parasuis confirmed by culturing on agar chocolate containing 64 μg/mL of bacitracin (Sigma-Aldrich, USA) as recommended by Miani, et al . 45 and PCR from swab using the primers HPS_219690793 as described by Howell, et al . 3 .…”

Tildipirosin: An effective antibiotic against Glaesserella parasuis from an in vitro analysis

“…(2015) showed cross-resistance between Tiamulin and Valnemulin, observed as well between Lincomycin and Tylosin Pringle et al., 2004 . These evidences need to be carefully interpreted in our particular case; in 2017 we demonstrated the circulation of G. parasuis clinical isolates highly resistant to Lincomycin, Tiamulin and Tylosin Miani et al., 2017 . Although the cross-resistance between macrolides would be a logical explanation for understanding the presence of resistant strains to Tildipirosin in Brazil, further studies need to be done to investigate the evolutionary process of G. parasuis resistance to Tildipirosin in regions with high resistance to Lincomycin.…”

“…As an evolutionary mechanism, microorganism can also develop cross-resistances between macrolides and lincosamides ( Roberts, 2008 ), possibly by plasmids carrying lnu(C) inactivanting gene of Lincosamyn ( Chen et al., 2010 ), raising a warning light on these two antimicrobial classes. In a previous study, we demonstrated a concern about the resistance trend of G. parasuis field strains to Tylosin Miani et al., 2017 . Here, we evaluated the in vitro efficacy of Tildipirosin, a semi‐synthetic derivative of the naturally occurring 16‐membered macrolide Tylosin on clinical isolates of G. parasuis .…”

“…Then, G. parasuis (5 × 10 4 organisms quantified by flow cytometry as described by Barasuol et al. ( Barasuol et al., 2017 ) was added to each well and incubated at 37ºC and 5% CO 2 for 24 h, as previously described ( Miani et al., 2017 ). The minimal inhibitory concentration (MIC) was defined as the lowest Tildipirosin concentration able to inhibit G. parasuis growth.…”

Glässer’s disease in swine from Northeastern Brazil

“…For Brazilian strains, a study showed that field isolates were highly resistant to gentamicin, bacitracin, lincomycin and tiamulin, but sensitive to ampicillin, clindamycin, neomycin, penicillin, danofloxacin and enrofloxacin. However, a susceptibility test prior to antibiotic therapy during GD outbreaks should be considered by veterinarians (Miani et al 2017). Particularly for population-level prophylaxis, the emphasis should be on vaccination strategies to prevent systemic infection and mortality combined with good biosecurity practices (Aragon et al 2012, Luning et al 2015.…”