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Antimicrobial resistance genes in Actinobacillus pleuropneumoniae , Haemophilus parasuis and Pasteurella multocida isolated from Australian pigs
Author(s) -
Dayao DAE,
Gibson JS,
Blackall PJ,
Turni C
Publication year - 2016
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/avj.12458
Subject(s) - pasteurella multocida , microbiology and biotechnology , actinobacillus pleuropneumoniae , tetracycline , ampicillin , haemophilus , penicillin , biology , antibiotic resistance , amp resistance , antimicrobial , haemophilus influenzae , pasteurellaceae , tilmicosin , antibiotics , virology , serotype , bacteria , genetics
Objective To identify genes associated with the observed antimicrobial resistance in Actinobacillus pleuropneumoniae , Haemophilus parasuis and Pasteurella multocida isolated from Australian pigs. Design Isolates with known phenotypic resistance to β‐lactams, macrolides and tetracycline were screened for the presence of antimicrobial resistance genes. Procedure A total of 68 A. pleuropneumoniae , 62 H. parasuis and 20 P. multocida isolates exhibiting phenotypic antimicrobial resistance ( A. pleuropneumoniae and P. multocida ) or elevated minimal inhibitory concentrations ( MICs ) ( H. parasuis ) to any of the following antimicrobial agents − ampicillin, erythromycin, penicillin, tetracycline, tilmicosin and tulathromycin − were screened for a total of 19 associated antimicrobial resistance genes ( ARGs ) by PCR . Results The gene bla ROB‐1 was found in all ampicillin‐ and penicillin‐resistant isolates, but none harboured the bla TEM‐1 gene. The tet B gene was found in 76% (74/97) of tetracycline‐resistant isolates, 49/53 A. pleuropneumoniae, 17/30 H. parasuis and 8/14 P. multocida . One A. pleuropneumoniae isolate harboured the tet H gene, but none of the 97 isolates had tet A, tet C, tet D, tet E, tet L, tet M or tet O. A total of 92 isolates were screened for the presence of macrolide resistance genes. None was found to have erm A, erm B, erm C, erm 42, mph E, mef A, msr A or msr E. Conclusion The current study has provided a genetic explanation for the resistance or elevated MIC of the majority of isolates of Australian porcine respiratory pathogens to ampicillin, penicillin and tetracycline. However, the macrolide resistance observed by phenotypic testing remains genetically unexplained and further studies are required.