TY - JOUR
T1 - Vibrio ordalii antimicrobial susceptibility testing-Modified culture conditions required and laboratory-specific epidemiological cut-off values
AU - Poblete-Morales, Matías
AU - Irgang, Rute
AU - Henríquez-Núñez, Hernán
AU - Toranzo, Alicia E.
AU - Kronvall, Göran
AU - Avendaño-Herrera, Ruben
N1 - Funding Information:
Funding for this study was provided in part by Grant FONDECYT 1110219 from the Comisión Nacional de Investigación Científica y Tecnológica (CONICYT, Chile) and also by Grant DI-99-12/R from the Universidad Andres Bello . RA-H also acknowledges to the CONICYT/FONDAP/15110027. Special thanks are expressed to Juan P. Maldonado for her technical help, and to Professor Peter Smith for fruitful discussions.
PY - 2013/8/30
Y1 - 2013/8/30
N2 - The present study aimed to determine oxytetracycline (OTC), florfenicol (FLO) and oxolinic acid (OXO) MICs and zone diameters for 24 Chilean Vibrio ordalii isolates using the methods for broth dilution susceptibility testing of bacteria isolated from aquatic animals and the methods for antimicrobial disk susceptibility testing of bacteria isolated from aquatic animals guidelines published by the Clinical Laboratory Standards Institute (CLSI). The results were then used in a normalized resistance interpretation (NRI) analysis to establish tentative laboratory-specific epidemiological cut-off (ECOFF) values. MIC results were similar at the two tested temperatures (22. °C and 18. °C). At 18. °C, the NRI analysis of OTC, FLO and OXO MIC data calculated laboratory-specific ECOFF values and non-wild-type (NWT) rates to be ≤4. mg/l (24%), ≤16. mg/l (4%) and ≤8. mg/l (25%), respectively. Tests performed with all V. ordalii isolates following the officially recommended incubation temperature (22. °C) revealed difficulties in measuring inhibition zone diameters. When disk diffusion tests were performed using Mueller-Hinton agar with 1% NaCl (MHA-1) at 18. °C the inhibition zone diameter distributions showed the formation of WT populations which could be defined using NRI analysis. For OTC the laboratory-specific ECOFF value was ≥38. mm with NWT rate of 16.7%. For FLO and OXO, the laboratory-specific ECOFF values were ≥38 and ≥40, respectively, generating NWT rates of 25 and 46%, respectively. Although the CLSI suggests testing Vibrio spp. on MHA-1 at 22. °C, we found measurements of the 24 isolates were better defined and normally distributed at 18. °C. This is the first study determining the MIC and disk diffusion test of V. ordalii isolated from diseased salmonids, where laboratory-specific ECOFF values could be established. Also resistance to OTC, FLO and OXO among some Chilean isolates was demonstrated.
AB - The present study aimed to determine oxytetracycline (OTC), florfenicol (FLO) and oxolinic acid (OXO) MICs and zone diameters for 24 Chilean Vibrio ordalii isolates using the methods for broth dilution susceptibility testing of bacteria isolated from aquatic animals and the methods for antimicrobial disk susceptibility testing of bacteria isolated from aquatic animals guidelines published by the Clinical Laboratory Standards Institute (CLSI). The results were then used in a normalized resistance interpretation (NRI) analysis to establish tentative laboratory-specific epidemiological cut-off (ECOFF) values. MIC results were similar at the two tested temperatures (22. °C and 18. °C). At 18. °C, the NRI analysis of OTC, FLO and OXO MIC data calculated laboratory-specific ECOFF values and non-wild-type (NWT) rates to be ≤4. mg/l (24%), ≤16. mg/l (4%) and ≤8. mg/l (25%), respectively. Tests performed with all V. ordalii isolates following the officially recommended incubation temperature (22. °C) revealed difficulties in measuring inhibition zone diameters. When disk diffusion tests were performed using Mueller-Hinton agar with 1% NaCl (MHA-1) at 18. °C the inhibition zone diameter distributions showed the formation of WT populations which could be defined using NRI analysis. For OTC the laboratory-specific ECOFF value was ≥38. mm with NWT rate of 16.7%. For FLO and OXO, the laboratory-specific ECOFF values were ≥38 and ≥40, respectively, generating NWT rates of 25 and 46%, respectively. Although the CLSI suggests testing Vibrio spp. on MHA-1 at 22. °C, we found measurements of the 24 isolates were better defined and normally distributed at 18. °C. This is the first study determining the MIC and disk diffusion test of V. ordalii isolated from diseased salmonids, where laboratory-specific ECOFF values could be established. Also resistance to OTC, FLO and OXO among some Chilean isolates was demonstrated.
KW - Antimicrobial resistance and susceptibility
KW - Laboratory-specific epidemiological cut-off values
KW - Normalized resistance interpretation
KW - Vibrio ordalii
UR - http://www.scopus.com/inward/record.url?scp=84892998474&partnerID=8YFLogxK
U2 - 10.1016/j.vetmic.2013.04.024
DO - 10.1016/j.vetmic.2013.04.024
M3 - Article
C2 - 23726222
AN - SCOPUS:84892998474
SN - 0378-1135
VL - 165
SP - 434
EP - 442
JO - Veterinary Microbiology
JF - Veterinary Microbiology
IS - 3-4
ER -