A Novel and Validated Protocol for Performing MIC Tests to Determine the Susceptibility of Piscirickettsia salmonis Isolates to Florfenicol and Oxytetracycline

This paper presents a validated protocol, using a novel, specifically formulated medium, to perform broth microdilution antimicrobial susceptibility assays of the salmonid bacterial pathogen . The minimum inhibitory concentrations (MIC) for florfenicol and oxytetracycline against 58 isolates recover...

Full description

Saved in:

Bibliographic Details
Published in:	Frontiers in microbiology Vol. 8; p. 1255
Main Authors:	Contreras-Lynch, Sergio, Smith, Peter, Olmos, Paola, Loy, María E, Finnegan, William, Miranda, Claudio D
Format:	Journal Article
Language:	English
Published:	Switzerland Frontiers Media S.A 06-07-2017
Subjects:	antimicrobial susceptibility epidemiological cut-off value fish pathogen MIC protocol Microbiology Piscirickettsia salmonis salmon farming Piscirickettsia salmonis antimicrobial susceptibility salmon farming epidemiological cut-off value MIC protocol fish pathogen
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	This paper presents a validated protocol, using a novel, specifically formulated medium, to perform broth microdilution antimicrobial susceptibility assays of the salmonid bacterial pathogen . The minimum inhibitory concentrations (MIC) for florfenicol and oxytetracycline against 58 isolates recovered from various outbreaks occurred in Chilean salmonid farms were determined using this protocol. Normalized resistance interpretation (NRI) analysis was applied to these data to calculate appropriate protocol-specific epidemiological cut-off values. These cut-off values allow the isolates to be categorized as either fully susceptible wild type (WT) members of this species, or as manifesting reduced susceptibility non-wild type (NWT). The distribution of MIC values of florfenicol was bimodal and the distribution of the normalized values for the putative WT observation had a standard deviation of 0.896 log μg mL . This analysis calculated a cut-off value of ≤0.25 μg mL and categorized 33 (56%) of the isolates as manifesting reduced susceptibility to florfenicol. For the oxytetracycline MIC data the NRI analysis also treated the distribution as bimodal. The distribution of the normalized values for the putative WT observation had a standard deviation of 0.951 log μg mL . This analysis gave a cut-off value of ≤0.5 μg mL and categorized five isolates (9%) as manifesting reduced susceptibility to oxytetracycline. The susceptibility testing protocol developed in this study was capable of generating MIC data from all the isolates tested. On the basis of the precision of the data it generated, and the degree of separation of values for WT and NWT it achieved, it is argued that this protocol has the performance characteristics necessary for it to be considered as a standard protocol.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Edited by: Hongyue Dang, Xiamen University, China Reviewed by: Max Maurin, Université Grenoble Alpes, France; Oystein Evensen, Norwegian University of Life Sciences, Norway This article was submitted to Aquatic Microbiology, a section of the journal Frontiers in Microbiology
ISSN:	1664-302X 1664-302X
DOI:	10.3389/fmicb.2017.01255