Bloodstream Infections caused by Klebsiella pneumoniae and Serratia marcescens isolates co-harboring NDM-1 and KPC-2

Carbapenem-resistant Enterobacteriaceae are a worldwide health problem and isolates carrying both bla(KPC-2) and bla(NDM-1) are unusual. Here we describe the microbiological and clinical characteristics of five cases of bloodstream infections (BSI) caused by carbapenem-resistant Klebsiella pneumoniae and Serratia marcescens having both bla(KPC-2) and bla(NDM-1). Of the five blood samples, three are from hematopoietic stem cell transplantation patients, one from a renal transplant patient, and one from a surgical patient. All patients lived in low-income neighbourhoods and had no travel history. Despite antibiotic treatment, four out of five patients died. The phenotypic susceptibility assays showed that meropenem with the addition of either EDTA, phenylboronic acid (PBA), or both, increased the zone of inhibition in comparison to meropenem alone. Molecular tests showed the presence of bla(KPC-2) and bla(NDM-1) genes. K. pneumoniae isolates were assigned to ST258 or ST340 by whole genome sequencing. This case-series showed a high mortality among patients with BSI caused by Enterobacteriae harbouring both carbapenemases. The detection of carbapenemase-producing isolates carrying both bla(KPC-2) and bla(NDM-1) remains a challenge when using only phenotypic assays. Microbiology laboratories must be alert for K. pneumoniae isolates producing both KPC-2 and NDM-1.

Automated summary

This study highlights the clinical and microbiological characteristics of five cases of bloodstream infections caused by carbapenem-resistant Enterobacteriaceae carrying both bla(KPC-2) and bla(NDM-1). Despite antibiotic treatment, a high mortality rate was observed among the patients. Phenotypic susceptibility assays showed that the addition of EDTA, phenylboronic acid (PBA), or both can increase the inhibition zone in comparison to meropenem alone. Detection of carbapenemase-producing isolates carrying both bla(KPC-2) and bla(NDM-1) remains a challenge, especially with only phenotypic assays.