Transcriptomic response of the opportunistic pathogen <i>Acinetobacter baumannii</i> to hospital biocides

<p><em>Acinetobacter baumannii</em> is a highly drug-resistant opportunistic pathogen, that the World Health Organisation has listed as a top priority against which new antibiotics are required. While antibiotic resistance in <em>A. baumannii</em> has been extensively studied, there are fewer studies investigating biocide resistance. It is extremely important to study biocide stress responses in bacteria, as there is mounting evidence of biocide-antibiotic cross-resistance among clinically relevant organisms. The work in this thesis describes the molecular response of <em>A. baumannii</em> AB5075-UW when exposed to four different hospital biocides: glutaraldehyde, ethanol, triclosan, and sodium hypochlorite. RNA-sequencing was used to elucidate the response of the organism to biocide stress. The transcriptomic analysis revealed that the most highly expressed genes in all the biocide treatments was the iron acquisition gene cluster encoding acinetobactin biosynthesis. Other pathways that were significantly impacted were the TCA cycle and respiration pathways and several catabolic pathways that feed intermediates into these two energy-producing cycles. Additionally, the unique responses of each individual biocide included downregulation of the <em>carO </em>gene by glutaraldehyde, upregulation of <em>adeABC </em>efflux pump genes under ethanol stress, increased expression of fatty acid biosynthesis pathways induced by triclosan treatment, and upregulation of an organic hydroperoxide resistance gene by sodium hypochlorite.</p>