Whole Genome Sequence Analysis of Pig Respiratory Bacterial Pathogens with Elevated Minimum Inhibitory Concentrations
Denise Ann Estarez Dayao1, Jennifer M Seddon1, Justine S Gibson1
11 School of Veterinary Science, The University of Queensland , Gatton, Queensland, Australia .
Abstract:
Macrolides are often used to treat and control bacterial pathogens causing respiratory disease in pigs. This study analyzed the whole genome sequences of one clinical isolate of Actinobacillus pleuropneumoniae, Haemophilus parasuis, Pasteurella multocida, and Bordetella bronchiseptica, all isolated from Australian pigs to identify the mechanism underlying the elevated minimum inhibitory concentrations (MICs) for erythromycin, tilmicosin, or tulathromycin. The H. parasuis assembled genome had a nucleotide transition at position 2059 (A to G) in the six copies of the 23S rRNA gene. This mutation has previously been associated with macrolide resistance but this is the first reported mechanism associated with elevated macrolide MICs in H. parasuis. There was no known macrolide resistance mechanism identified in the other three bacterial genomes. However, strA and sul2, aminoglycoside and sulfonamide resistance genes, respectively, were detected in one contiguous sequence (contig 1) of A. pleuropneumoniae assembled genome. This contig was identical to plasmids previously identified in Pasteurellaceae. This study has provided one possible explanation of elevated MICs to macrolides in H. parasuis. Further studies are necessary to clarify the mechanism causing the unexplained macrolide resistance in other Australian pig respiratory pathogens including the role of efflux systems, which were detected in all analyzed genomes.
Insights
A genetic mutation in Haemophilus parasuis explains elevated macrolide antibiotic resistance in pigs. This study identified a novel resistance mechanism in this key swine pathogen, crucial for controlling respiratory disease.
Area of Science:
- Veterinary Microbiology
- Genomics
- Antimicrobial Resistance
Background:
- Macrolide antibiotics are vital for managing bacterial respiratory diseases in pigs.
- Elevated minimum inhibitory concentrations (MICs) for macrolides in swine pathogens necessitate understanding resistance mechanisms.
Purpose of the Study:
- To investigate the genomic basis for elevated macrolide MICs in Australian swine respiratory pathogens: Actinobacillus pleuropneumoniae, Haemophilus parasuis, Pasteurella multocida, and Bordetella bronchiseptica.
- To identify specific genetic mutations or elements conferring macrolide resistance.
Main Methods:
- Whole genome sequencing of four bacterial species isolated from Australian pigs.
- Bioinformatic analysis to identify genetic variations and resistance genes.
- Comparison of identified sequences with known resistance mechanisms and plasmids.
Main Results:
- A specific nucleotide transition (A to G at position 2059) in the 23S rRNA gene of H. parasuis was identified, linked to macrolide resistance.
- This is the first report of this mutation as a mechanism for elevated macrolide MICs in H. parasuis.
- No known macrolide resistance mechanisms were found in A. pleuropneumoniae, P. multocida, or B. bronchiseptica, although aminoglycoside and sulfonamide resistance genes were detected in A. pleuropneumoniae.
Conclusions:
- A genetic mutation in H. parasuis provides a potential explanation for observed macrolide resistance.
- Further research is required to elucidate the causes of unexplained macrolide resistance in other Australian pig respiratory pathogens, including the role of efflux systems.
