Klebsiella pneumoniae in the marine environment

Abstract

<p><i>Klebsiella pneumoniae</i> is an opportunistic pathogen present in a wide range of environments. This species is often associated with antibiotic resistance and is a leading cause of health care associated infections but can also cause community acquired infections. Even though <i>K. pneumoniae</i> is extensively studied in clinical settings, less is known about its prevalence, antibiotic resistance, and pathogenic potential in the environment, especially the marine environment. In the present work, we sampled bivalve molluscs, seawater, fish and sediments to gain knowledge on <i>K. pneumoniae</i> in the marine environment. Overall, we found <i>K. pneumoniae sensu stricto</i> (<i>K. pneumoniae</i>) in 14 % (n=81) of examined samples of bivalve molluscs and 35 % (n=6) of seawater samples from coastal waters. No <i>K. pneumoniae</i> isolates were recovered from fish, sediments or seawater collected from open oceans. The prevalence of acquired antibiotic resistance was low, however, six (7%) <i>K. pneumoniae</i> isolates carried acquired antibiotic resistance genes (ARGs). Heavy metal resistance genes (HMRGs) were common, present in 72 % (n=62) of the isolates, also those carrying acquired ARGs. All antibiotic resistant isolates carried the ARGs on IncF family plasmids and most carried HMRGs on the same plasmid. Ten isolates harboured the yersiniabactin siderophore commonly present in isolates causing infection in humans. The results also revealed high genetic diversity, with 50 sequence types (STs) identified, also those associated with hypervirulence (ST25) and multidrug resistance (ST17, ST20, ST29 and ST37), whereas one <i>K. pneumoniae</i> ST25 isolate from bivalves was closely related to a clinical isolate. This work shows that <i>K. pneumoniae</i> was present in marine bivalve molluscs and coastal waters and that some of the obtained isolates carried antibiotic resistance genes and/or virulence genes. Thus, our work shows that the marine environment and seafood may potentially serve as a source of pathogenic bacteria and antibiotic resistance genes.