NDM-1-producing Vibrio parahaemolyticus isolated from imported seafood

Sir, Vibrio parahaemolyticus is a marine microorganism, frequently isolated from seafood, at water temperatures above 15°C.1 It is also a foodborne pathogen, often linked to consumption of raw or uncooked seafood, mostly encountered in patients in Asia or the USA.1 Ingestion of V. parahaemolyticus-contaminated seafood can lead to gastroenteritis. Symptoms are abdominal cramps, nausea, diarrhoea, fever, headache and chills.1 In most cases, V. parahaemolyticus infections are self-limiting but, in patients with underlying diseases, V. parahaemolyticus can cause septicaemia.1 To treat severe or prolonged infections, antibiotics such as fluoroquinolones, azithromycin or rifaximin can be prescribed.2 WT V. parahaemolyticus are characterized as being susceptible to all antibiotic classes, except penicillins.3 V. parahaemolyticus strain 16-B3PA-006 was isolated in January 2016, from a shelled shrimp tail imported from Vietnam to France. Antimicrobial susceptibility was tested by the disc diffusion method (Bio-Rad, Marne-La-Coquette, France), following CLSI recommendations.4 Genomic characterization of the isolate was performed by WGS on a NextSeq (Illumina, San Diego, CA, USA). The raw reads were trimmed (minimum length, 35 bp; quality score, 0.03) and assembled in CLC Genomics Workbench 7.5.1, firstly by mapping chromosome 1 and 2 from the V. parahaemolyticus reference genome (V. parahaemolyticus RIMD 2210633) and then de novo assembly of the remaining paired-end reads. A total of 190 contigs were obtained including 60 contigs that did not map the reference genome, indicating the presence of acquired genetic material. The Center for Genomic Epidemiology server (https://cge.cbs.dtu.dk/services/) was used to identify acquired antimicrobial resistance genes (Resfinder), plasmid presence (PlasmidFinder) and ST (MLST). Strain 16-B3PA-006 was assigned to V. parahaemolyticus ST-864. PlasmidFinder identified a unique IncA/C2 plasmid. V. parahaemolyticus strain 16-B3PA-006 was phenotypically resistant to amoxicillin/clavulanate, cefoxitin, cefotaxime, ceftazidime, cefuroxime, cefepime and trimethoprim/sulfamethoxazole, but remained susceptible to imipenem, tetracycline, ciprofloxacin and gentamicin. Resfinder identified with 100% identity the resistance genes blaNDM-1, sul1, sul2, dfrA16, strA, strB and aadA2. Moreover, floR and tet(A) were detected with 98.19% and 99.83% identity, respectively. No resistance gene was neighbouring blaNDM-1, only sul1 was on the opposite side of the contig, at a distance of 14 kb. A Blastn analysis of this contig with the National Center for Biotechnology Information nucleotide database identified a part of transposon Tn125: ΔISAba125, blaNDM-1, ble, trpF, tat, dct, groS, groL and IS91. Despite the apparent susceptibility to imipenem, the carbapenem inactivation method result was positive, confirming carbapenemase production by this strain.5 Even if the chromosomal or plasmidic location of blaNDM-1 had not been assessed so far, the carbapenemase phenotype had been successfully transferred to Escherichia coli UB5201 strain by conjugation assay. V. parahaemolyticus 16-B3PA-006 was confirmed to be MDR, by both genotype and phenotype, being resistant to more than three antibiotic classes: β-lactams, folate pathway inhibitors, phenicols, aminoglycosides and tetracyclines. The Tn125 transposon, carried by strain 16-B3PA-006, has been partially described in a clinical case of Vibrio fluvialis, but the transposon was not complete.6 Since its first description in 2009 in a patient returning from India, NDM-1 has been described in almost all parts of the world and is considered as one of the most clinically significant carbapenemases.7 In many of the first cases reported, patients were reporting recent inter-country travel history, not only to the Indian subcontinent, but also to the Balkan states, the Arabian Peninsula and North Africa; some of them having been repatriated for medical purposes.7 NDM-1-producing Vibrio spp. have been reported to a lesser extent in V. fluvialis and Vibrio cholerae clinical or environmental samples.6,8–10 To our knowledge, this report is the first description of a V. parahaemolyticus strain producing NDM-1 isolated from a food item. Other carbapenemase-producing bacteria isolated from foodstuffs have already been reported: NDM-1-producing Salmonella and Enterobacter cloacae from chicken and clam; and VIM-1-producing Salmonella and E. coli from pork and Venus clam.11–14 Nicol et al.12 and Roschanski et al.14 highlighted that the sampled food products in their studies were also imported. Interestingly, strain 16-B3PA-006 was proved to both carry the blaNDM-1 gene and display in vitro carbapenemase activity; nonetheless, the antibiogram categorized it as clinically susceptible to imipenem according to CLSI criteria. In vitro susceptibility to any carbapenem had not been described previously in NDM-1-producing Vibrio spp.6,8–10 Clinical microbiologists should be aware that NDM-1 carbapenemase activity in V. parahaemolyticus might be challenging to evidence through routine susceptibility tests. It is generally assumed that travellers, colonized by carbapenemase-producing bacteria, import it from endemic to non-endemic parts of the world.15 However, imported food should also be taken into consideration as a potential vector of dissemination of clinically significant carbapenemases such as NDM-1. The role of the global food trade should certainly not be underestimated anymore as an alternative route for carbapenemase dissemination. Strain 16-B3PA-006 sequence is available under GenBank accession number PETB00000000. We would like to thank Stéphanie Copin, Virginie Raguenet, Guylaine Leleu and Régine Quenu for their assistance. We are especially grateful to Didier Mazel for his assistance with the conjugation assay and for providing the recipient strain. We would like to thank the iGenSeq core facility (Brain & Spine Institute, Hôpital Pitié Salpêtrière, Paris, France) for excellent sequencing services. This work was supported by a doctoral fellowship from Région Hauts-de-France and by the French national effort to reduce antimicrobial resistance in veterinary medicine called ‘EcoAntibio2017’ from the Ministry of Agriculture. None to declare.

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