DESCRIPTIVE CLINICAL REPORT
Temporal trends in in vitro antimicrobial susceptibility patterns of bacteria isolated from foals with sepsis: 1979–2010
Article first published online: 11 SEP 2013
© 2013 EVJ Ltd
Equine Veterinary Journal
Volume 46, Issue 2, pages 161–168, March 2014
How to Cite
Theelen, M. J. P., Wilson, W. D., Edman, J. M., Magdesian, K. G. and Kass, P. H. (2014), Temporal trends in in vitro antimicrobial susceptibility patterns of bacteria isolated from foals with sepsis: 1979–2010. Equine Veterinary Journal, 46: 161–168. doi: 10.1111/evj.12130
- Issue published online: 18 FEB 2014
- Article first published online: 11 SEP 2013
- Accepted manuscript online: 1 JUL 2013 05:09AM EST
- Manuscript Accepted: 22 JUN 2013
- Manuscript Received: 20 FEB 2013
- Center for Equine Health
- State of California Pari-Mutuel Fund
- temporal trends;
- Enterococcus spp
Reasons for performing the study
Monitoring the development of antimicrobial resistance is important for the rational selection of appropriate antimicrobial drugs to initiate treatment of foals with sepsis.
To identify temporal trends in antimicrobial susceptibility patterns of bacteria isolated from foals with sepsis.
Retrospective review of medical records.
Foals aged <30 days with a diagnosis of sepsis, confirmed by culture of bacteria, were included. Susceptibility data, expressed as minimum inhibitory concentrations (MICs) (MIC50, MIC90, MIC range) and percent of isolates that were susceptible to a particular antimicrobial drug, were compared for bacteria isolated from foals during 3 different time periods: 1979–1990, 1991–1997 and 1998–2010. The Cochran-Armitage trend test and the Jonckheere-Terpstra test were used for statistical analysis.
A total of 1091 bacterial isolates were cultured from 588 foals. Enterobacteriaceae, Actinobacillus spp. and β-haemolytic Streptococcus spp. showed a decrease in percent of isolates susceptible to gentamicin over time. Enterobacteriaceae, Actinobacillus spp. and β-haemolytic Streptococcus spp. showed an increase in MIC values for amikacin. Enterobacteriaceae showed a decrease in percent of isolates susceptible to ceftiofur. Enterococcus spp. and Pseudomonas spp. showed increased MIC values to ceftiofur. Enterobacteriaceae showed increased MIC values to ceftizoxime. Enterococcus spp. became more resistant to imipenem and showed increased MIC values to ticarcillin/clavulanic acid. In contrast, several trends in increased susceptibility were also seen.
Based on these in vitro results, the combination of amikacin and ampicillin remains an appropriate choice for initiating treatment of sepsis in foals while awaiting culture and susceptibility test results, although increasing development of resistance to amikacin was demonstrated. The decrease in in vitro activity of ceftiofur against Enterobacteriaceae is of concern. Similarly, the development of resistance of Enterococcus spp. to imipenem is an important finding that warrants monitoring in the future. Judicious use of antimicrobials is therefore crucial.