Abstract
BackgroundIn recent years the emergence of multidrug resistant Klebsiella pneumoniae strains has been an increasingly common event. This opportunistic species is one of the five main bacterial pathogens that cause hospital infections worldwide and multidrug resistance has been associated with the presence of high molecular weight plasmids. Plasmids are generally acquired through horizontal transfer and therefore is possible that systems that prevent the entry of foreign genetic material are inactive or absent. One of these systems is CRISPR/Cas. However, little is known regarding the clustered regularly interspaced short palindromic repeats and their associated Cas proteins (CRISPR/Cas) system in K. pneumoniae. The adaptive immune system CRISPR/Cas has been shown to limit the entry of foreign genetic elements into bacterial organisms and in some bacteria it has been shown to be involved in regulation of virulence genes. Thus in this work we used bioinformatics tools to determine the presence or absence of CRISPR/Cas systems in available K. pneumoniae genomes.ResultsThe complete CRISPR/Cas system was identified in two out of the eight complete K. pneumoniae genomes sequences and in four out of the 44 available draft genomes sequences. The cas genes in these strains comprises eight cas genes similar to those found in Escherichiacoli, suggesting they belong to the type I-E group, although their arrangement is slightly different. As for the CRISPR sequences, the average lengths of the direct repeats and spacers were 29 and 33 bp, respectively. BLAST searches demonstrated that 38 of the 116 spacer sequences (33%) are significantly similar to either plasmid, phage or genome sequences, while the remaining 78 sequences (67%) showed no significant similarity to other sequences. The region where the CRISPR/Cas systems were located is the same in all the Klebsiella genomes containing it, it has a syntenic architecture, and is located among genes encoding for proteins likely involved in metabolism and resistance to antibiotics.ConclusionsThe CRISPR/Cas system is not widely distributed in K. pneumoniae genomes, those present most likely belong to type I-E with few differences from the arrangement of the cse3 gene and most of the spacers have not been are not described yet. Given that the CRISPR/Cas system is scarcely distributed among K. pneumoniae genomes it is not clear whether it is involved in either immunity against foreign genetic material or virulence. We consider that this study represents a first step to understand the role of CRISPR/Cas in K. pneumoniae.Electronic supplementary materialThe online version of this article (doi:10.1186/s13104-015-1285-7) contains supplementary material, which is available to authorized users.
Highlights
In recent years the emergence of multidrug resistant Klebsiella pneumoniae strains has been an increas‐ ingly common event
Given that the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR elements and their associated Cas proteins (Cas) system is scarcely distributed among K. pneumoniae genomes it is not clear whether it is involved in either immunity against foreign genetic material or virulence
A system that allows bacteria to limit the entry of genetic elements is the adaptive immune system CRISPR/ Cas, which has been described in many Bacteria and Archaea
Summary
In recent years the emergence of multidrug resistant Klebsiella pneumoniae strains has been an increas‐ ingly common event. Plasmids are generally acquired through horizontal transfer and is possible that systems that prevent the entry of foreign genetic material are inactive or absent One of these systems is CRISPR/Cas. little is known regarding the clustered regularly interspaced short palindromic repeats and their associated Cas proteins (CRISPR/ Cas) system in K. pneumoniae. The ability of bacteria to adapt to new environments has been favored by the acquisition of genes through horizontal gene transfer (HGT) [1] Despite this apparent advantage, each organism must balance the need to acquire beneficial characteristics through HGT with the need to prevent the entry of genetic elements that impose additional energy costs. The CRISPR/Cas expression is tightly regulated but the information is limited to some genera [3, 5, 8–13]
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