1653. Transcriptional Variation of Adhesion and Biofilm Genes in CTX-M-15-Expressing Klebsiella pneumoniae

BACKGROUND: Klebsiella pneumoniae can produce a number of β-lactamases, including the cefotaximase, CTX-M-15. While classically associated with ST131 Escherichia coli, CTX-M-15 is associated with increased virulence in K. pneumoniae. Clinical isolates of K. pneumoniae have been shown to produce high levels of CTX-M-15 RNA. But, the overall transcriptomic changes due to CTX-M-15 expression are unknown. The purpose of this study was to determine if acquisition of CTX-M-15 altered the global transcriptome of K. pneumoniae in addition to decreasing β-lactam susceptibility. METHODS: The structural gene and native promoter of CTX-M-15 were cloned into a low copy number vector and transformed into Kp 23, a clinical isolate from the 1970s with no known acquired β-lactam resistance genes. CTX-M-15 production was confirmed by qRT PCR and western blot. MICs to cefotaxime, ceftazidime, cefepime, ceftolozane/tazobactam, ceftazidime/avibactam, meropenem, meropenem-vaborbactam, and imipenem-relebactam were determined by E-test according to CLSI guidelines. RNA-Seq analysis and bioinformatics were performed by MiGS. RESULTS: CTX-M-15 carriage led to non-susceptible MICs to cefotaxime, ceftazidime, and cefepime. CTX-M-15 production was associated with statistically significant upregulation of 204 genes and downregulation of 231 genes. Among these, the biofilm genes mrkA and two copies of mrkB were downregulated by 7.5, 4 and 3.5-fold, respectively. Additionally, ecpA, ecpB, ecpC, and ecpR – components of the E. coli Common Pilus (ECP) – were upregulated by 3, 2, 2, and 3-fold, respectively. CONCLUSION: High-level expression of CTX-15 β-lactamase has a significant impact on the transcriptome of K. pneumoniae. These changes include a down regulation of genes associated with biofilm formation with a concomitant increase in the expression of genes associated with adherence. These data indicate that overexpression of CTX-M-15 and perhaps other β-lactamases may help promote the pathogenicity of K. pneumoniae or influence its ability to colonize the tissue it infects. This may be important during urinary tract infections when an increase in adhesion by CTX-M-15 producing isolates may be required over biofilm formation to establish an active infection. DISCLOSURES: Nancy D. Hanson, PhD, Merck: Grant/Research Support.