Novel tigecycline resistance mechanisms in Acinetobacter baumannii mediated by mutations in adeS, rpoB and rrf

Abstract

Acinetobacter baumannii is an important pathogen in hospital acquired infections. Although tigecycline currently remains a potent antibiotic for treating infections caused by multidrug resistant A. baumannii (MDRAB) strains, reports of tigecycline resistant isolates have substantially increased. The resistance mechanisms to tigecycline in A. baumannii are far more complicated and diverse than what has been described in the literature so far. Here, we characterize in vitro -selected MDRAB strains obtained by increasing concentrations of tigecycline. We have identified mutations in adeS , rrf and rpoB that result in reduced susceptibility to tigecycline. Using in situ complementation experiments, we confirm that mutations in rrf , rpoB , and two types of mutations in adeS correlate with tigecycline resistance. By Western blot and polysome profile analysis, we demonstrate that the rrf mutation results in decreased expression of RRF, which affects the process of ribosome recycling ultimately leading to increased tigecycline tolerance. A transcriptional analysis shows that the mutated rpoB gene plays a role in regulating the expression of the SAM-dependent methyltransferase ( trm ) and transcriptional regulators, to confer moderate tigecycline resistance. This study provides direct in vitro evidence that mutations in the adeS , rpoB and rrf are associated with tigecycline resistance in A. baumannii .

Interactions between host epithelial cells and Acinetobacter baumannii promote the emergence of highly antibiotic resistant and highly mucoid strains

“…Individual libraries were assessed on the QIAxcel Advanced Automatic nucleic acid analyzer and then were quantitated through qPCR by the use of KAPA SYBR FAST qPCR Kits (Kapabio systems, Boston, US). The bacterial genome was sequenced on an Illumina HiSeq platform (Illumina, San Diego, CA, USA) as described previously [ 22 ]. Breseq v. 0.33.0 was used for comparative genome analyses [ 23 ], referencing the original genome of ATCC17978 (GenBank accession NZ_CP018664.1).…”

Molecular Mechanisms Driving the In Vivo Development of KPC-71-Mediated Resistance to Ceftazidime-Avibactam during Treatment of Carbapenem-Resistant Klebsiella pneumoniae Infections

“…The growth curve, the area under the curve (AUC), and the relative growth rate were used as indicators of fitness and were assessed as previously described ( 29 ). Four independent cultures of each strain were grown overnight in MH broth.…”

Dissemination and prevalence of plasmid-mediated high-level tigecycline resistance gene tet (X4)

“…Mutation of rpsJ in Enterococci also leads to resistance to tigecycline (Cattoir et al, 2015). Mutations in the rff, ropB and adeS genes in A. baumannii can affect the normal function of the ribosome and thus confer tigecycline resistance to the strain (Hua et al, 2021).…”