Clonal Spread of Highly Successful ST15-CTX-M-15 Klebsiella Pneumoniae in Companion Animals and Horses

Objectives: To investigate the clinical relevance and molecular epidemiology of extended-spectrum β-lactamase (ESBL)-producing Klebsiella species in animals.

Methods: Antimicrobial susceptibilities and presence of ESBLs were examined among Klebsiella spp. (n = 1519) from clinical samples (>1200 senders from Germany and other European countries) mainly from companion animals and horses from October 2008 to March 2010. Multilocus sequence typing (MLST) and PFGE were performed including human isolates for comparative purposes.

Results: The overall ESBL rate was 8% for Klebsiella pneumoniae subsp. pneumoniae. Most K. pneumoniae subsp. pneumoniae ESBL producers were isolated from soft tissue infections (29.3%) and urinary tract infections (14.9%). The major ESBL type was CTX-M-15 (85.4%), located on different plasmid scaffolds (HI2, I1, FIA, FIB, FII, A/C, R and N). Other ESBL genes, such as bla(CTX-M-1) (5.6%), bla(CTX-M-3), bla(CTX-M-9), bla(SHV-2) and bla(SHV-12) (1.1% each), were also detected. Additional resistances, e.g. to fluoroquinolones (89.9%), were frequently present. ST15-CTX-M-15, a clonal group that recently emerged in humans, accounted for 75.8% of the strains analysed by MLST and there was evidence for nosocomial events in five veterinary clinics. Human ST15-CTX-M-15 strains shared PFGE clusters with animal isolates, suggesting the dissemination of this clonal group between both populations.

Conclusions: Our data indicate a wide spread of ST15-CTX-M-15 K. pneumoniae subsp. pneumoniae, which should be considered as a zoonotic agent of high clinical relevance for humans and animals. Further research should be undertaken to unravel both microevolutionary and biological aspects probably contributing to this global success.