Improved Broth Microdilution Method for Antimicrobial Susceptibility Testing ofFrancisella Noatunensis Orientalis

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.

Francisella marina sp. nov., Etiologic Agent of Systemic Disease in Cultured Spotted Rose Snapper (Lutjanus guttatus) in Central America

“…orientalis and F. noatunensis subsp. noatunensis, including susceptibility to oxytetracycline, which reduced mortality in the epizootics described previously (19,20), and florfenicol (21). This is noteworthy, as oxytetracycline and florfenicol are approved therapeutants against piscine francisellosis in food fish in several fish-producing countries.…”

“…Additionally, archived Francisella noatunensis subsp. orientalis strains used for comparison in this study were isolated from a range of fish species and geographical locations, several of which were described previously (21). Other isolates were generously shared by John Hansen from the Interdisciplinary Program in Pathobiology, University of Washington, Seattle, WA, and Duncan J. Colquhoun at the Section for Bacteriology, Norwegian Veterinary Institute, Oslo, Norway (Table 7).…”

“…Antimicrobial susceptibility was assessed using a broth microdilution method adapted from Francisella tularensis to F. noatunensis subsp. orientalis (21,31). MICs of antimicrobial agents against isolates E103-15 and E95-16 were tested using the Sensititre AVIANF plate system (Sensititre; ThermoFisher, Cleveland, Ohio).…”

Therapeutic efficacy of enrofloxacin in treatment of Francisella orientalis infections in juvenile Nile tilapia (Oreochromis niloticus L.)

“…If the microenvironment in the host is favorable, the bacterium restores its metabolism and spreads. In addition, the pathogen may exhibit resistance to antimicrobial agents, which has not been previously reported in the literature for F. orientalis isolates (Ramírez-Paredes et al, 2017;Soto et al, 2012Soto et al, , 2016. Considering the above information, this could be one of the reasons for the treatment failures of OTC and FLO against francisellosis.…”

In vitro antibacterial activity of dried extract from Anredera vesicaria rhizomes

“…[9][10][11] The reagents and solvents used were of "pure" or "analytical" quality from Merck. The antibacterial activity of the extract was evaluated by the method of diffusion method in agar by Bauer-Kirby 12 surface disc dissemination and by the method of micro dilution in broth 13 against a battery composed of strains of Pseudomonas aeruginosa (wild), Staphylococcus aureus (wild), Escherichia coli (wild) and Salmonella typhimurium (ATCC 14028). 4 treatments were applied with 3 replications in each applied method, using as a negative control dimethyl sulfoxide (DMSO) that also served as solvent for the dry extract, and as a positive control disks of the commercial antibiotic chloramphenicol of 30μg/disc (Sensi-DiscTM, France).…”