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Response of Mycobacterium avium subsp. paratuberculosis isolates to reactive oxygen stress generated by treatment
P Steuer1, H W Barkema2, C Tejeda1
1Laboratorio de Enfermedades Infecciosas, Instituto de Medicina Preventiva Veterinaria, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Casilla P.O. Box 567, Valdivia, Chile.
Abstract:
Copper (Cu) ions have been recognized for their efficacy in inactivating bacteria, including Mycobacterium avium subsp. paratuberculosis (MAP), the causative agent of Johne's disease (JD) known for its resilience to unfavorable conditions. However, the response of MAP isolates isolated from cows to Cu exposure remains inadequately understood, as their responses may differ from those of laboratory-adapted reference strains. In this study, we examined the response of MAP isolates obtained from MAP-infected and affected cows to Cu ion treatment, comparing that with the response of the reference strain ATCC 19698 to the same treatment. Three MAP field isolates and the MAP reference strain were exposed to Cu ions, and their viability, protein/lipid damage, ROS production, and gene expression were evaluated in triplicate. Survival differed among isolates, with an isolate from a cow with clinical JD exhibiting increased tolerance to Cu exposure. While Cu treatment induced lipid peroxidation and ROS production across all isolates, genes associated with Cu detoxification and virulence were upregulated, particularly in the reference strain. Whole genome sequencing analysis revealed that, despite genomic similarities between field isolates and the reference strain ATCC 19698, there were differences regarding the presence/absence of genes related with certain virulence factors. Further research on Cu exposure with larger numbers of MAP isolates is needed to explain the stress-induced responses that influence MAP survival during natural infections and in challenging environments.
Insights
Copper ions show potential against Mycobacterium avium subsp. paratuberculosis (MAP), the cause of Johne's disease (JD). However, field isolates exhibit varied tolerance to copper, necessitating further investigation into MAP's resilience.
Area of Science:
- Veterinary Microbiology
- Bacteriology
- Environmental Health
Background:
- Copper (Cu) ions are known antimicrobials effective against various bacteria.
- Mycobacterium avium subsp. paratuberculosis (MAP) causes Johne's disease (JD) in cattle and is notably resilient.
- The specific response of MAP field isolates to copper exposure is not well-characterized compared to reference strains.
Purpose of the Study:
- To investigate the differential response of MAP field isolates from infected cows to copper ion treatment.
- To compare the copper tolerance and stress response mechanisms of MAP field isolates with a laboratory reference strain.
- To identify potential genetic factors influencing MAP survival under copper stress.
Main Methods:
- Exposure of three MAP field isolates and the ATCC 19698 reference strain to copper ions.
- Evaluation of bacterial viability, lipid peroxidation, reactive oxygen species (ROS) production, and gene expression.
- Whole genome sequencing of MAP isolates to identify genetic variations.
Main Results:
- Varied survival rates among MAP isolates upon copper exposure, with one clinical JD isolate showing higher tolerance.
- Copper treatment induced lipid peroxidation and ROS production in all tested MAP strains.
- Upregulation of copper detoxification and virulence genes was observed, particularly in the reference strain.
- Whole genome sequencing revealed genetic differences in virulence-associated genes between field isolates and the reference strain.
Conclusions:
- MAP field isolates display heterogeneous responses to copper exposure, indicating adaptive resilience.
- Copper-induced stress triggers conserved responses like ROS production and detoxification gene upregulation.
- Genetic variations, especially in virulence factors, may contribute to differential copper tolerance in MAP.
- Further studies with more isolates are crucial to understand MAP's survival strategies in diverse environments.
