Thermotolerance and multidrug resistance in bacteria isolated from equids and their environment.
Authors: Singh B R
Journal: The Veterinary record
Summary
# Editorial Summary Singh's 2009 investigation characterised thermotolerant and multidrug-resistant bacteria recovered from 195 horses and their environment, examining whether heat tolerance correlates with antimicrobial resistance profiles in equine-associated pathogens. Rectal and vaginal swabs from horses, alongside soil samples from farm premises, were cultured for bacteria surviving 60°C for one hour, with isolates then challenged by pasteurisation (63.8°C for 30 minutes) and tested against multiple antimicrobial classes. The survey identified concerning patterns: 41 of 138 rectal swabs yielded thermotolerant *E. coli*, with seven isolates surviving pasteurisation, whilst *Enterobacter* species demonstrated particularly robust heat tolerance and were more resistant to pasteurisation than *E. coli*; critically, 95% of rectal isolates and all soil isolates were multidrug resistant, though notably none showed resistance to chloramphenicol, ciprofloxacin or cotrimoxazole. For practitioners, these findings underscore the prevalence of multidrug-resistant gram-negative bacteria in equine reproductive and gastrointestinal tracts, raising questions about therapeutic choices for conditions like metritis or septic arthritis, and highlighting that heat tolerance itself does not necessarily indicate antimicrobial resistance—suggesting that resistance patterns should guide antibiotic selection rather than assumptions based on bacterial thermotolerance alone.
Read the full abstract on PubMed
Practical Takeaways
- •High prevalence of multidrug-resistant thermotolerant bacteria in equid gastrointestinal and reproductive tracts indicates potential food safety and antimicrobial stewardship concerns for equine operations
- •Enterobacter species are more heat-tolerant than E. coli, suggesting different sanitation protocols may be needed for effective pathogen control in equine facilities
- •Environmental contamination (soil samples) also harbored multidrug-resistant thermotolerant bacteria, highlighting the need for farm biosecurity and hygiene practices to prevent spread
Key Findings
- •Thermotolerant E. coli was isolated from 41 of 138 rectal swabs (29.7%) and 11 of 69 vaginal swabs (15.9%) from equids
- •7 of 48 E. coli isolates and 2 of 18 Enterobacter isolates survived pasteurization at 63.8°C for 30 minutes
- •All isolates except 6 total were multidrug resistant; 9 of 10 pasteurization-resistant isolates were multidrug resistant
- •No isolated bacteria grew at 46°C or above, and Enterobacter species showed greater pasteurization tolerance than E. coli