Clinical and molecular features of NDM-producing Acinetobacter baumannii in a multicenter study in Israel

NDM-producing Acinetobacter baumannii (NDMAb) were reported sporadically worldwide but little is known about the transmission, epidemiology and clinical features of NDMAb-infected patients. The goals of this study were to characterize (1) the epidemiology and clinical features of NDMAb-infected patients; (2) the microbiological and molecular features of NDMAb isolates and (3) the transmission networks of NDMAb within healthcare facilities.

The study was conducted at the Tel-Aviv Sourasky, Rambam and Sha'are-Zedek Medical centers (TASMC, RMC and SZMC, respectively) in Israel. All cases detected between January 2018 and July 2019 were included. Phylogenetic analysis was based on core genome SNP distances. Clonal transmission was defined according to molecular (≤ 5 SNP) and epidemiological criteria (overlapping hospital stay). NDMAb cases were compared at a ratio of 1:2 with non-NDM carbapenem-resistant A. baumannii (CRAb) cases.

The study included 54 NDMAb-positive out of 857 CRAb patients, including 6/179 (3.3%) in TASMC, 18/441 (4.0%) in SZMC and 30/237 (12.6%) in RMC. Patients infected by NDMAb had similar clinical features and risk factors as patients with non-NDM CRAb. The length-of-stay was higher in NDMAb cases (48.5 days vs. 36 days, respectively, p = 0.097) and the in-hospital mortality was similarly high in both groups. Most isolates (41/54, 76%) were first detected from surveillance culture. The majority of isolates harbored the bla_{NDM-2 gene} allele (n = 33), followed by the bla_NDM-1 (n = 20) allele and the bla_NDM-4 allele (n = 1). The majority of isolates were related within the ST level to other isolates in SZMC and RMC: 17/18 and 27/30 isolates, respectfully. The common ST's were the bla_NDM-1 harboring ST-2 (n = 3) and ST-107 (n = 8) in SZMC and the bla_NDM-2 harboring ST-103 in SZMC (n = 6) and in RMC (n = 27). All bla_NDM alleles were located within a conserved mobile genetic environment flanked by the ISAb125 and IS91 family transposon. Clonal transmission was identified in most hospital-acquired cases in RMC and SZMC.

NDMAb constitutes a minor part of CRAb cases and are clinically similar to non-NDM CRAb. Transmission of NDMAb occurs mostly by clonal spread.