Abstract
and
are naturally occurring estuarine bacteria and are the leading causes of seafood-associated infections and mortality in the United States. Though multiple-antibiotic-resistant
and
strains have been reported, resistance patterns in vibrios are not as well documented as those of other foodborne bacterial pathogens. Salinity relaying (SR) is a postharvest processing (PHP) treatment to reduce the abundances of these pathogens in shellfish harvested during the warmer months. The purpose of this study was to evaluate the antimicrobial susceptibility (AMS), pathogenicity, and genetic profiles of
and
recovered from oysters during an oyster relay study. Isolates (
[
= 296] and
[
= 94]) were recovered from oysters before and during the 21-day relaying study to detect virulence genes (
and
) and genes correlated with virulence (
) using multiplex quantitative PCR (qPCR). AMS to 20 different antibiotics was investigated using microbroth dilution, and pulsed-field gel electrophoresis (PFGE) was used to study the genetic profiles of the isolates. Twenty percent of
isolates were
, while 1 and 2% of
were
and
, respectively. More than 77% of the
isolates and 30% of the
isolates were resistant to at least one antimicrobial. Forty-eight percent of
and 8% of
isolates were resistant to two or more antimicrobials. All isolates demonstrated a high genetic diversity, even among those isolated from the same site and having a similar AMS profile. No significant effects of the relaying process on AMS, virulence genes, or PFGE profiles of
and
were observed.
Analysis of the antibiotic resistance profiles of
and
isolated from oysters during this study indicated that more than 48% of
isolates were resistant to two or more antimicrobials, including those recommended by the CDC for treating
infections. Also, the
isolates showed high MICs for some of the
infection treatment antibiotics. Monitoring of AMS profiles of this bacterium is important to ensure optimal treatment of infections and improve food safety. Our study showed no significant differences in the AMS profiles of
(
= 0.26) and
(
= 0.23) isolated from the oysters collected before versus after relaying. This suggests that the salinity of the relaying sites did not affect the AMS profiles of the
isolates, although it did reduce the numbers of these bacteria in oysters (S. Parveen et al., J Food Sci 82:484-491, 2017, https://doi.org/10.1111/1750-3841.13584).