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Antimicrobial activity of enrofloxacin against Staphylococcus intermedius strains isolated from canine pyodermas
J P Ganière1, C Médaille, A Limet
1Unité de Pathologie Infectieuse, Ecole Nationale Vétérinaire, BP 40706, 44307 Nantes, France. ganiere@vet-nantes.fr
Abstract:
This study examined and compared the minimal inhibition concentrations (MICs) of enrofloxacin against 393 Staphylococcus intermedius strains isolated in France from canine pyodermas during three different years, 1995 (174 isolates), 1997 (101 isolates) and 1999 (118 isolates). The MICs of enrofloxacin against these strains ranged from 0.063 to 64 mg L-1, with MIC50 and MIC90 equal to 0.125 and 0.25 mg L-1, respectively. Two resistant strains were found, but only among isolates collected in 1999. The data show that resistance to enrofloxacin among S. intermedius strains is still rare in dogs, but the selection in vitro of variants in which the MICs were increased 4-16-fold after 10 serial passages in subinhibitory concentrations of enrofloxacin suggests that inappropriate use might favour the development of resistant strains in vivo.
Insights
Enrofloxacin resistance in Staphylococcus intermedius strains from canine pyoderma is rare in France. However, laboratory studies show that inappropriate antibiotic use could promote the development of resistant strains in vivo.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Resistance
- Canine Dermatology
Background:
- Staphylococcus intermedius is a common cause of canine pyoderma.
- Enrofloxacin is a fluoroquinolone antibiotic frequently used in veterinary medicine.
- Monitoring antimicrobial resistance is crucial for effective treatment strategies.
Purpose of the Study:
- To determine the minimal inhibition concentrations (MICs) of enrofloxacin against Staphylococcus intermedius strains isolated from canine pyodermas in France.
- To assess the prevalence of enrofloxacin resistance in these strains over time.
- To investigate the potential for in vitro selection of enrofloxacin-resistant variants.
Main Methods:
- Collection and isolation of 393 Staphylococcus intermedius strains from canine pyodermas in France between 1995 and 1999.
- Determination of enrofloxacin MICs using standard microbiological methods.
- In vitro serial passage experiments in subinhibitory enrofloxacin concentrations.
Main Results:
- Enrofloxacin MICs ranged from 0.063 to 64 mg L-1.
- MIC50 and MIC90 values were 0.125 and 0.25 mg L-1, respectively.
- Two resistant strains were identified exclusively in 1999 isolates; in vitro passages showed a 4-16 fold increase in MICs.
Conclusions:
- Enrofloxacin resistance in Staphylococcus intermedius remains uncommon in French canine pyoderma cases.
- The in vitro selection of resistant variants suggests a potential risk of resistance development with inappropriate enrofloxacin use.
- Continued surveillance and judicious antibiotic use are recommended to preserve enrofloxacin efficacy.