Detection of carbapenemase-producing enterobacteriaceae in the baltic countries and st. Petersburg area

Abstract

The spread of carbapenemase-producing Enterobacteriaceae is a global problem; however, no exact data on the epidemiology of carbapenemase in the Baltic countries and St. Petersburg area is available. We aimed to evaluate the epidemiology of carbapenemase-producing Escherichia coli and Klebsiella pneumoniae in the Baltic States and St. Petersburg, Russia, and to compare the different methods for carbapenemase detection. From January to May 2012, all K. pneumoniae (n = 1983) and E. coli (n = 7774) clinical isolates from 20 institutions in Estonia, Latvia, Lithuania, and St. Petersburg, Russia were screened for carbapenem susceptibility. The IMP, VIM, GIM, NDM, KPC, and OXA-48 genes were detected using real-time PCR and the ability to hydrolyze ertapenem was determined using MALDI-TOF MS. Seventy-seven strains were found to be carbapenem nonsusceptible. From these, 15 K. pneumoniae strains hydrolyzed ertapenem and carried the bla NDM gene. All of these strains carried integron 1 and most carried integron 3 as well as genes of the CTX-M-1 group. No carbapenemase-producing E. coli or K. pneumoniae strains were found in Estonia, Latvia, or Lithuania; however, NDM-positive K. pneumoniae was present in the hospital in St. Petersburg, Russia. A MALDI-TOF MS-based assay is a suitable and cost-effective method for the initial confirmation of carbapenemase production.

Figure 1

Percentages of carbapenem nonsusceptible Klebsiella pneumoniae strains in particular hospitals (dots) and the country averages (lines). LT: Lithuania, LV: Latvia, RU: Russia, St. Petersburg, and EE: Estonia.

Figure 2

MALDI-TOF MS spectrum showing ertapenem and its degradation products. Spectrum related to (a) positive control (Klebsiella pneumoniae metallo-β-lactamase positive): hydrolyzed decarboxylated product of ertapenem (450.5 Da); (b) incubated ertapenem solution: hydrolyzed decarboxylated product of ertapenem (450.5 Da), ertapenem molecule (476.5 Da), and ertapenem sodium adduct (498.5 Da); (c) pure ertapenem solution: hydrolyzed decarboxylated product of ertapenem (450.5 Da), ertapenem molecule (476.5 Da), ertapenem sodium adduct (498.5 Da), and ertapenem disodium adduct (520.5 Da); (d) New Delhi Metallo-β-lactamase-positive strain (Klebsiella pneumoniae): hydrolyzed decarboxylated product of ertapenem (450.5 Da); (e) negative control (noncarbapenemase-producing Klebsiella pneumoniae): hydrolyzed decarboxylated product of ertapenem (450.5 Da), ertapenem molecule (476.5 Da), and ertapenem sodium adduct (498.5 Da).

Figure 3

Evaluation of the MALDI-TOF MS spectra of 16 different Klebsiella pneumoniae strains using the new software prototype. Differences in the hydrolysis rates of the different strains can easily be detected: green area: no hydrolysis; yellow area: intermediate hydrolysis; red area: hydrolysis.