First Detection of AmpC β-LactamaseblaCMY-2on a Conjugative IncA/C Plasmid in a Vibrio parahaemolyticus Isolate of Food Origin

Abstract

ABSTRACTVibrio parahaemolyticusis an important causative agent of gastroenteritis, with the consumption of contaminated seafood being the major transmission route. Resistance to penicillin is common amongV. parahaemolyticusstrains, whereas cephalosporin resistance remains rare. In an attempt to assess the current prevalence and characteristics of antibiotic resistance of this pathogen in common food samples, a total of 54 (17% of the total samples)V. parahaemolyticusstrains were isolated from 318 meat and seafood samples purchased from supermarkets and wet markets in Shenzhen, China, in 2013. These isolates exhibited high-level resistance to ampicillin, yet they were mostly susceptible to other antimicrobials, except for two that were resistant to extended-spectrum cephalosporins. The β-lactamase geneblaPER-1was detectable in one strain,V. parahaemolyticusV43, which was resistant to both third- and fourth-generation cephalosporins. Compared to otherblaPER-1-positiveV. parahaemolyticusstrains reported in our previous studies, strain V43 was found to harbor an ∼200-kb conjugative plasmid carrying genes that were different from the antimicrobial resistance genes reported from the previous studies. The β-lactamase geneblaCMY-2was detectable for the first time in anotherV. parahaemolyticusisolate, V4, which was resistant to third-generation cephalosporins. ThisblaCMY-2gene was shown to be located in an ∼150-kb IncA/C-type conjugative plasmid with a genetic structure consisting oftraB-traV-traA-ISEcp1-blaCMY-2-blc-sugE-encR-orf1-orf2-orf3-orf4-dsbC-traC, which is identical to that of other IncA/C conjugative plasmids inEnterobacteriaceae, albeit with a different size. These findings indicate that the transmission of extended-spectrum-β-lactamase (ESBL) and AmpC β-lactamase genes via conjugative plasmids can mediate the development of extended-spectrum cephalosporin resistance inV. parahaemolyticus, thereby posing a potential threat to public health.