Antibiotic Sensitivity Screening of Klebsiella spp. and Raoultella spp. Isolated from Marine Bivalve Molluscs Reveal Presence of CTX-M-Producing K. pneumoniae

Abstract

<i>Klebsiella</i> spp. are a major cause of both nosocomial and community acquired infections, with <i>K. pneumoniae</i> being responsible for most human infections. Although <i>Klebsiella</i> spp. are present in a variety of environments, their distribution in the sea and the associated antibiotic resistance is largely unknown. In order to examine prevalence of <i>K. pneumoniae</i> and related species in the marine environment, we sampled 476 batches of marine bivalve molluscs collected along the Norwegian coast. From these samples, <i>K. pneumoniae</i> (<i>n</i> = 78), <i>K. oxytoca</i> (<i>n</i> = 41), <i>K. variicola</i> (<i>n</i> = 33), <i>K. aerogenes</i> (<i>n</i> = 1), <i>Raoultella ornithinolytica</i> (<i>n</i> = 38) and <i>R. planticola</i> (<i>n</i> = 13) were isolated. The number of positive samples increased with higher levels of faecal contamination. We found low prevalence of acquired resistance in all isolates, with seven <i>K. pneumoniae</i> isolates showing resistance to more than one antibiotic class. The complete genome sequence of cefotaxime-resistant <i>K. pneumoniae sensu stricto</i> isolate 2016-1400 was obtained using Oxford Nanopore and Illumina MiSeq based sequencing. The 2016-1400 genome had two contigs, one chromosome of 5,088,943 bp and one plasmid of 191,744 bp and belonged to ST1035. The β-lactamase genes <i>bla</i>_CTX-M-3 and <i>bla</i>_TEM-1, as well as the heavy metal resistance genes <i>pco</i>, <i>ars</i> and <i>sil</i> were carried on a plasmid highly similar to one found in <i>K. pneumoniae</i> strain C17KP0055 from South-Korea recovered from a blood stream infection. The present study demonstrates that <i>K. pneumoniae</i> are prevalent in the coastal marine environment and that bivalve molluscs may act as a potential reservoir of extended spectrum β-lactamase (ESBL)-producing <i>K. pneumoniae</i> that may be transmitted through the food chain.