Basic comments about AB resistance
- All antibiotics select for resistance...you look for it- you find it....
- Antibiotics used in animal health just like all AB's
- AB resistance poses threat to human health
- Many factors that contribute to emergence and dissemination of antibiotic resistance
- Not possible to quantify 'attributable risk' for any of the complex factors that contribute to resistance
Microbes of resistance concern in horses
- Salmonella [3rd generation cephalosporins, fluoroquinolones]
- E. coli [same as above]
- Enterococci [ fluoroquinolones, gentamicin, vancomycin, macrolides]
- MRSA [3rd generation cephlosporins, fluoroquinolones, macrolides]
Patient file
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Factors that increase resistance
- Inadequate dosing
- Indiscriminate use of antibiotics
- Inadequate duration of therapy
- Noncompliant owners
- Close physical contact between horses & owners
- Public awareness- increasing attention in literature
- Evidence of bidirectional transfer
- Strong evidence of carrier states for both pets and humans
- MRSAs documented to arise from both human and veterinary hospitals
Veterinary Microbiology
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Salmonella
Gram-negative, flagellated facultatively anaerobic bacilli
Possessing 3 major antigens:
* H (flagellar): phase 1/phase 2
* O (somatic): surface of outer membrane, determined by specific sugar sequences on cell surface
* Vi : superficial antigen overlying the O antigen, present in only a few serovars (S typhi)
- Cell envelope contains complex LPS
- 2449 serotypes
Pathogenesis
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Pathogenesis:
1) ability to invade cells
2) complete LPS coat
3) ability to replicate intracellularly
4) elaboration of toxin(s)
Methicillin-Resistant Staphylococcus aureus (MRSA) in Horses
Equine Salmonellosis
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- Most important hospital associated pathogen in human medicine
- Increasingly reported in animals
- MRSA infection of horses + horse personnel is emerging problem
- Disease can occur in either species and interspecies transmission propagates MRSA
