Presence of Colistin- and Tigecycline-Resistant <i>Klebsiella pneumoniae</i> ST29 in Municipal Wastewater Influents in Japan
Wataru Hayashi, Masaki Iimura, Eiji Soga, Shota Koide, Katsutoshi Izumi, Satoshi Yoshida, Yoshichika Arakawa, Yukiko Nagano, Noriyuki Nagano
Abstract
The aim of this study was to investigate the presence of colistin- and/or tigecycline-resistant Klebsiella spp. in influents from four wastewater treatment plants (WWTPs), which partly reflect the gut microbiome of human populations. Colistin- and tigecycline-resistant Klebsiella pneumoniae isolates (K30/ST29) were detected four times from the WWTP A during a period of 3 months. Disruptions of the mgrB and ramR genes by IS Ec68 and IS Kpn21 , respectively, were identified in those four isolates. They also shared the IncL/M 86,197-bp plasmids carrying a bla CTX-M-3 and Tn 1548 -associated armA [IS 26 - IntI1 - dfrA12 - gucF - aadA2 - qacEΔ1 - sul1 -IS CR1 -IS Ec28 - armA -IS Ec29 - msr (E)- mph (E)-IS 26 ]. Those isolates formed a distinct cluster within wgMLST clusters of ST29 K30 public reference strains of human origin and were unique due to harboring of Tn 21 -like mercury resistance operon transposons in addition to silver, copper, and arsenic resistance determinants. Five K. pneumoniae strains with different STs and 1 Klebsiella quasipneumoniae strain, exhibiting colistin resistance, were detected in WWTPs B, C, and D. For these isolates, disruptions of mgrB by IS Ec68 (three isolates) or IS Ecl1 (one isolate), insertion of IS 2 in the mgrB promoter region (one isolate), and inactivation of MgrB by a nonsense mutation (one isolate) were identified. Close monitoring of these mcr -negative colistin- and/or tigecycline-resistant bacteria in wastewater influents is imperative to avoid further limiting of treatment options.