title: IS5 element integration, a novel mechanism for rapid in vivo emergence of tigecycline nonsusceptibility in Klebsiella pneumoniae.
abstract: Tigecycline nonsusceptibility is concerning because tigecycline is increasingly relied upon to treat carbapenem- or colistin-resistant organisms. In Enterobacteriaceae, tigecycline nonsusceptibility is mediated by the AcrAB-TolC efflux pump, among others, and pump activity is often a downstream effect of mutations in their transcriptional regulators, cognate repressor genes, or noncoding regions, as demonstrated in Enterobacteriaceae and Acinetobacter isolates. Here, we report the emergence of tigecycline nonsusceptibility in a longitudinal series of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Klebsiella pneumoniae isolates collected during tigecycline therapy and the elucidation of its resistance mechanisms. Clinical isolates were recovered prior to and during tigecycline therapy of a 2.5-month-old Honduran neonate. Antimicrobial susceptibility tests to tigecycline determined that the MIC increased from 1 to 4 μg/ml prior to the completion of tigecycline therapy. Unlike other studies, we did not find increased expression of ramA, ramR, oqxA, acrB, marA, or rarA genes by reverse transcription-quantitative PCR (qRT-PCR). Whole-genome sequencing revealed an IS5 insertion element in nonsusceptible isolates 85 bp upstream of a putative efflux pump operon, here named kpgABC, previously unknown to be involved in resistance. Introduction of the kpgABC genes in a non-kpgABC background increased the MIC of tigecycline 4-fold and is independent of a functional AcrAB-TolC pump. This is the first report to propose a function for kpgABC and identify an insertion element whose presence correlated with the in vivo development of tigecycline nonsusceptibility in K. pneumoniae.
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network (MRSN), Walter Reed Army Institute of Research, Silver Spring, Maryland, USA Lindsey.e.nielsen2.mil@mail.mil.
authors.forename: Lindsey E
authors.initials: LE
authors.lastname: Nielsen
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network (MRSN), Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors.forename: Erik C
authors.initials: EC
authors.lastname: Snesrud
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network (MRSN), Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors.forename: Fatma
authors.initials: F
authors.lastname: Onmus-Leone
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network (MRSN), Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors.forename: Yoon I
authors.initials: YI
authors.lastname: Kwak
authors.affiliation: Soto Cano Air Base, Comayagua, Honduras.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Avilés
authors.affiliation: MRSN, San Antonio Military Medical Center, Fort Sam Houston, San Antonio, Texas, USA.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Steele
authors.affiliation: Division of Pediatric Infectious Disease, San Antonio Military Medical Center, Fort Sam Houston, San Antonio, Texas, USA.
authors.forename: Deena E
authors.initials: DE
authors.lastname: Sutter
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network (MRSN), Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors.forename: Paige E
authors.initials: PE
authors.lastname: Waterman
authors.affiliation: Multidrug-Resistant Organism Repository and Surveillance Network (MRSN), Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors.forename: Emil P
authors.initials: EP
authors.lastname: Lesho
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D024881:Drug Resistance, Bacterial / Q000235:genetics; D007711:Klebsiella pneumoniae / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D008911:Minocycline / Q000031:analogs & derivatives* / Q000494:pharmacology; D008969:Molecular Sequence Data; D000078304:Tigecycline
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D000078304:Tigecycline; D008911:Minocycline
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