Antimicrobial resistance profiles and molecular epidemiology of Klebsiella pneumoniae isolates from Scottish bovine mastitis cases

Abstract

Klebsiella pneumoniae are opportunistic pathogens which can cause mastitis in dairy cattle. K. pneumoniae mastitis often has a poor cure rate and can lead to the development of chronic infection, which has an impact on both health and production. However, there are few studies which aim to fully characterize K. pneumoniae by whole-genome sequencing from bovine mastitis cases. Here, K. pneumoniae isolates associated with mastitis in dairy cattle were identified using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and whole-genome sequencing. Furthermore, whole-genome sequence data were used for phylogenetic analyses and both virulence and antimicrobial resistance (AMR) prediction, in parallel with phenotypic AMR testing. Forty-two isolates identified as K. pneumoniae were subject to whole-genome sequencing, with 31 multi-locus sequence types being observed, suggesting the source of these isolates was likely environmental. Isolates were examined for key virulence determinants encoding acquired siderophores, colibactin, and hypermucoidy. The majority of these were absent, except for ybST (encoding yersiniabactin) which was present in six isolates. Across the dataset, there were notable levels of phenotypic AMR against streptomycin (26.2%) and tetracycline (19%), and intermediate susceptibility to cephalexin (26.2%) and neomycin (21.4%). Of importance was the detection of two ESBL-producing isolates, which demonstrated multi-drug resistance to amoxicillin-clavulanic acid, streptomycin, tetracycline, cefotaxime, cephalexin, and cefquinome.

Keywords: AMR; Klebsiella; MALDI-TOF; WGS; mastitis.

Figure 1.

Mid-point rooted, neighbour-joining tree showing phylogenetic relationships among K. pneumoniae mastitis isolates from Scotland. Tree constructed using pairwise SNP distances across 1972 K. pneumoniae core genes and produced by Pathogenwatch [25]. Multiple isolates came from Farms B (7 isolates) and V (5 isolates), and these are highlighted in green and yellow, respectively. ST107 isolates are highlighted in a black box. The presence of yersiniabactin is denoted by red star and antimicrobial resistance genes are shown by squares as being either present (filled black square) or absent (empty square).

Figure 2.

Mid-point rooted, neighbour-joining tree showing phylogenetic relationships among international isolates K. pneumoniae ST107. Tree constructed using pairwise SNP distances across 1972 K. pneumoniae core genes and produced by Pathogenwatch [25]. Geographical location of origin and host are indicated by a coloured key. Labels of study isolates are shaded grey, and UK is differentiated from Europe for the purposes of this figure.