Novel insights related to the rise of KPC-producing Enterobacter cloacae complex strains within the nosocomial niche

ÁLVAREZ VE, MASSÓ MG, GONZÁLEZ GD, GAMBINO AS, KNECHT CA, CORMICK BPM, LEGUINA C, PIEKAR M, POKLÉPOVICH T, CAMPOS J, ARDUINO S, CENTRÓN D, QUIROGA MP; ALVAREZ VE; QUIROGA MP; CENTRON DANIELA

Front Cell Infect Microbiol

Frontiers Media SA

Lugar: Lausanne; Año: 2022

2235-2988

According to the World Health Organization, carbapenem-resistant Enterobacteriaceae (CRE) belong to the highest priority group to develop new antibiotics. Argentina-WHONET data showed that Gram-negative resistance frequencies to imipenem have been increasing since 2010 mostly in two CRE species: Klebsiella pneumoniae and Enterobacter cloacae Complex (ECC). This scenario is mirrored in our hospital, with K. pneumoniae accounting for 85% of carbapenem-resistant strains, and in second place the ECC with 12%. Our aim was to contribute to the understanding of the steady rise of ECC in Argentina, taking as a biological model both a patient colonized with two KPC-producing strains (one K. pneumoniae and one Enterobacter hormaechei) and competition assays with prevalent KPC-producing ECC (KPC-ECC) versus KPC-producing K. pneumoniae (KPC-Kp) high-risk international clones from our institution. A KPC-producing E. hormaechei (KPC-Eho) strain that belonged to the pandemic lineage ST45 (HA2pEho), and later a KPC-Kp strain which belonged to ST18 (HA7pKpn) were colonizing the same patient. Both strains were multidrug-resistant and shared a novel conjugative IncM1 plasmid (77.2 Kb) with blaKPC-2 embedded in the genetic platform ISKpn27-blaKPC-2-ISKpn6-HP-Tn3. In addition, a total of 19 KPC-ECC and 58 KPC-Kp strains isolated from nosocomial infections r in the period 10/2018 until 05/2020 from our institution were sequenced. International high-risk clones KPC-Kp ST11 and ST258 as well as KPC-ECC ST66 and ST78 were also found and tested in competition assays. Fitness of K. pneumoniae ST258 over E. hormaechei ST45 and ST78 were statistically significant while the rest of assays showed the same biological cost (S=0). As a whole, these assays evidenced that high-risk clones of KPC-ECC and KPC-Kp can coexist in the same hospital environment including the same patient. These findings offer hints to explain the worldwide rise of KPC-ECC strains based on the ability of some pandemic clones to compete and occupy a certain niche. Also, both the presence of the new plasmid, and fitness results that showed that both strains can coexist within the same patient, suggest that horizontal genetic transfer (HGT) of blaKPC-2 within the patient cannot be ruled out which highlights the constant interaction that these two species have in the hospital environment.