Natasha Sushenko, M.S. Candidate

Department of Biological Sciences

Quaternary Ammonium Compound Resistance of Klebsiella pneumoniae  and
Klebsiella quasipneumoniae  Strains Isolated from the International Space

Committee Members:

• Dr. Brian Hedlund, Chair
• Dr. Duane Moser, Advisory Committee Member
• Dr. Helen Wing, Advisory Committee Member
• Dr. Elisabeth Hausrath, Graduate College Representative

Abstract:

• Recent metagenome studies of International Space Station (ISS) interior
  surfaces have shown *Klebsiella pneumoniae* to be the most prevalent
  biosafety level 2 (BSL-2) organism in the ISS microbiome. Multi-drug
  resistant (MDR) strains of *Klebsiella *species are known to carry genes
  encoding carbapenamases, which confer resistance to broad-spectrum
  antibiotics as well as common disinfectants such as quaternary ammonium
  compounds (QACs). QACs are used to sanitize surfaces on the ISS, but the
  effects of QACs on *Klebsiella *are poorly understood. For my master’s
  thesis, I studied strains of *Klebsiella pneumoniae *and *Klebsiella
  quasipneumoniae, *opportunistic BSL-2 pathogens that were isolated from the
  surface microbiome of the ISS, with particular emphasis on how these
  ISS-adapted strains differ from an Earth-origin type strain when exposed to
  QACs. The first research chapter (Chapter 2) consists primarily of *in
  silico *work to complete the genome of *Klebsiella quasipneumoniae *subsp.
  *similipneumoniae *strain IF3SW-P1, isolated from the ISS; this included
  assembly and annotation of the genome based on long-read Oxford Nanopore
  Technology sequencing data. The completed genome was then analyzed for the
  presence of putative virulence and antimicrobial resistance genes. The
  second research chapter (Chapter 3) consists of experimental approaches to
  study the responses to QAC disinfectants by both ISS- and Earth-origin
  strains of *Klebsiella. *This work included determining the minimum
  inhibitory concentration (MIC) of QACs for each strain before conducting
  viability assays at both sub-lethal and standard QAC concentrations. These
  viability assays included viability qPCR using the viability dye PMAxx, as
  well as fluorescence microscopy conducted using LIVE/DEAD BacLight
  viability dyes. This work showed significant differences in the response of
  the two ISS-origin strains of *Klebsiella, *as well as differences between
  the ISS-origin strains and the Earth-origin type strain, in both the amount
  of QACs required to inhibit growth of the strains and in the responses of
  the strains after exposure to lethal QAC concentrations. This suggests
  frequent cleaning of ISS surfaces with QACs is selecting for strains that
  are resistant to QACs, which may increase risk of infection among
  astronauts; based on these results, more research should be done to
  elucidate the prevalence of QAC resistance on the ISS so NASA can determine
  whether their use should be discontinued.