Biophysical Society Thematic Meeting | Stockholm 2022

Physical and Quantitative Approaches to Overcome Antibiotic Resistance

Poster Abstracts

23-POS Board 23 CHROMOSOMAL DELETION OF ADEL GENE IN ACINETOBACTER BAUMANNII ATCC 17978 LEADS TO OVEREXPRESSION OF ADEAB EFFLUX PUMP Emrah Sariyer 1 ; Aysegul Saral Sariyer 2 ; Inga V. Leus 3 ; Helen I. Zgurskaya 3 ; 1 Artvin Coruh University, Vocational School of Health Services, Artvin, Turkey 2 Artvin Coruh University, Department of Nutrition and Dietetics, Artvin, Turkey 3 University of Oklahoma, Department of Chemistry and Biochemistry, Norman, OK, USA Multi-drug efflux pumps are one of the mechanisms that contribute to the MDR A. baumannii phenotype. Efflux pumps AdeIJK, AdeABC and AdeFGH contribute to the MDR phenotype in A. baumannii. A LysR-type transcriptional regulator (LTTR), AdeL, is encoded upstream from the adeFGH operon and is known as a negative regulator. The elucidation of efflux pump regulatory mechanisms may contribute to the discovery of new antibiotics. In this study, we deleted the 734 bp region of adeL gene in A. baumannii ATCC 17978 (AbWT) and its ΔAdeIJK mutant and characterized the effect of this chromosomal deletion on the antibiotic susceptibility profile and growth physiology. For deletion of the adeL gene, a gentamicin resistance gene cassette in pMo130-Gm and recombineering primers were used. The gentamicin resistance gene cassette was removed from ΔAdeIJK ΔAdeL:Gm and ΔAdeL:Gm by i ncorporating FLP recognition target (FRT) sites. Removal of the resistance gene cassette was confirmed by PCR. Broth microdilution method was used for determining minimal inhibitory concentrations (MIC) of antibiotics against ΔAdeIJK, ΔAdeIJK ΔAdeL, AbWT and ΔAdeL. Growth curves were analyzed for these strains grown in LB broth and in the presence of chloramphenicol (MIC/2). Compared to ΔAdeIJK, the ΔAdeL mutant had no changes in MIC values of antibiotics. The difference in MIC values was observed only between AbWT and its AdeL mutant for azithromycin, zeocin and gentamicin. According to growth curve assays, chromosomal deletion caused a growth defect in AbWT and its ΔAdeIJK mutant. This defect was more visible in the presence of chloramphenicol. Our results suggest that AdeL may have a different physiological role besides the control of AdeFGH expression. The changes in antibiotic susceptibility profile suggest that AdeL inactivation may cause the overexpression of AdeAB without changes in the expression of AdeFGH.

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