Improved Broth Microdilution Method for Antimicrobial Susceptibility Testing of Francisella Noatunensis Orientalis

Authors

Esteban Soto, Department of Medicine and Epidemiology, School of Veterinary Medicine , University of California , Tupper Hall 2108, 1 Shields Avenue, Davis , California 95616 , USA.
Iona Halliday-Simmonds, Department of Biomedical Sciences , Ross University School of Veterinary Medicine , Post Office Box 334, Basseterre, St. Kitts, West Indies.
Stewart Francis, Department of Biomedical Sciences , Ross University School of Veterinary Medicine , Post Office Box 334, Basseterre, St. Kitts, West Indies.
Trellor Fraites, Department of Biomedical Sciences , Ross University School of Veterinary Medicine , Post Office Box 334, Basseterre, St. Kitts, West Indies.
Beatriz Martínez-López, Center for Animal Disease Modeling and Surveillance, Department of Medicine and Epidemiology, School of Veterinary Medicine , University of California , Tupper Hall 2108, 1 Shields Avenue, Davis , California 95616 , USA.
Judy Wiles, Department of Pathobiological Sciences , Louisiana State University, School of Veterinary Medicine ,1909 Skip Bertman Drive, Baton Rouge , Louisiana 70803 , USA.
John P. Hawke, Department of Pathobiological Sciences , Louisiana State University, School of Veterinary Medicine ,1909 Skip Bertman Drive, Baton Rouge , Louisiana 70803 , USA.
Richard D. Endris, Endris Consulting , Inc., 492 Foothill Road, Bridgewater , New Jersey 08807 , USA.

Document Type

Article

Publication Date

9-1-2016

Abstract

In this project we optimized a minimal inhibitory concentration testing protocol for Francisella noatunensis orientalis. Thirty-three F. noatunensis orientalis isolates recovered from different fish species and locations were tested, and Escherichia coli ATCC 25922 was used as a quality control reference strain. A modified cation-adjusted Mueller Hinton broth supplemented with 2% IsoVitalex and 0.1% glucose (MMH) was tested at a pH of 6.4 ± 0.1, 7.1 ± 0.1, and 7.3 ± 0.1. Growth curves generated for F. noatunensis orientalis indicated that MMH at a pH of 6.4 ± 0.1 provided optimal growth. There were no significant differences in the growth curves obtained from isolates recovered from different fish species or from fresh or marine water. The pH of 6.4 ± 0.1 in the MMH media interfered with the inhibitory properties of the potentiated sulfonamides (ormetoprim-sulfadimethoxine and trimethoprim-sulfamethoxazole) when using the E. coli ATCC reference strain. Minimal inhibitory concentrations of eight antimicrobials (gentamicin, enrofloxacin, ampicillin, oxytetracycline, erythromycin, florfenicol, flumequine, and oxolinic acid) were similar for all F. noatunensis orientalis isolates. The in vitro susceptibility data provided here can provide a baseline for monitoring the development of antimicrobial resistance among F. noatunensis orientalis isolates, as well as provide valuable data in the development of potential therapeutics. Received October 27, 2015; accepted April 13, 2016.

Publication Source (Journal or Book title)

Journal of aquatic animal health

First Page

199

Last Page

207

Recommended Citation

Soto, E., Halliday-Simmonds, I., Francis, S., Fraites, T., Martínez-López, B., Wiles, J., Hawke, J. P., & Endris, R. D. (2016). Improved Broth Microdilution Method for Antimicrobial Susceptibility Testing of Francisella Noatunensis Orientalis. Journal of aquatic animal health, 28 (3), 199-207. https://doi.org/10.1080/08997659.2016.1185051