Carbon monoxide and nitric oxide as antimicrobial agents -- focus on ESBL-producing uropathogenic E. coli

Charlotte Sahlberg Bang (2016): Carbon monoxide and nitric oxide as antimicrobial agents -focus on ESBL-producing uropathogenic E. coli. Örebro Studies in Medicine 136. Urinary tract infections (UTI) are common in humans and most often caused by uropathogenic Escherichia coli (E. coli). Extended-spectrum beta-lactamase (ESBL)-producing E. coli are increasing worldwide and they are frequently multidrug-resistant with limited treatment options. The overall aim of this thesis was to study the role of the host-derived factors nitric oxide (NO) and carbon monoxide (CO) as antimicrobial agents against ESBL-producing uropathogenic strains of E. coli (UPEC). The NO-donor DETA/NO caused a temporary growth inhibition in ESBL-producing UPEC. The antibacterial effect of DETA/NO was improved when DETA/NO was combined with miconazole, a pharmacological inhibitor of NO-protective mechanisms. Combination treatment with DETA/NO, miconazole and polymyxin B nonapeptid prolonged the bacteriostatic effect in the majority of examined isolates. The CO-donor CORM2 showed a pronounced antibacterial effect in ESBL-producing UPEC with a fast bactericidal effect. Moreover, CORM-2 was shown to reduce the bacterial viability of ESBL-producing UPEC grown under biofilm-like conditions and to decrease the bacterial colonization of human bladder epithelial cells. A microarray analysis was performed to define transcriptomic targets of CORM-2 after a single exposure and after repeated exposure to CORM-2. Many processes were affected by CORM-2, including a downregulation in energy metabolism and biosynthesis pathways and upregulation of the SOS response and DNA repair. Repeated exposure to CORM2 did not change the gene expression patterns or fold changes and the growth inhibitory response to CORM-2 was not altered after repeated exposure. In conclusion, NOand CO-donors have antibacterial effects against ESBL-producing UPEC and may be interesting candidates for development of new antibiotics to treat UTI caused by multidrug-resistant uropathogens. Ke ywords: biofilm, carbon monoxide, CORM-2, DETA/NO, extendedspectrum beta-lactamases, nitric oxide, urinary tract infection, uropathogenic Escherichia coli. Charlotte Sahlberg Bang, School of Medical Sciences, Örebro University, SE-701 82 Örebro, Sweden, [email protected]