Upper and lower urinary tract infection caused by Klebsiella pneumoniae serotype K2 and CTX-M-15 β-lactamase-producing serotype K1: a case report and characterization of serum killing resistance

CTX-M-15 beta-lactamase-producing Klebsiella pneumoniae serotype K1 was isolated from a patient with fatal upper urinary tract infection (UTI) complicated by sepsis caused by K. pneumoniae serotype K2. Transfer of a CTX-M-15 beta-lactamase plasmid from the K1 to the K2 strain was observed. However, plasmid acquisition by the K2 strain did not occur in vivo, suggesting that the K1 strain might not have contributed directly to the upper UTI. In addition, effects of K serotypes and plasmid acquisition on K. pneumoniae serum resistance were examined.