Abstract
Pandemic uropathogenic E. coli strain ST131 has been associated with multi-drug resistance and an increased likelihood of recurrent or persistent infections. Type-1-fimbriae have been implicated in ST131 biofilm formation, which can contribute to a persistent infection after antibiotic treatment. This suggests that type-1-fimbriae may contribute to the pandemic state of ST131. The type-1-fimbriae operon, beginning with fimA, is regulated by a promoter located on a region of DNA (fimS) that can be inverted by fim recombinases FimB and FimE. I hypothesized that ST131 strains upregulate fimA and have a higher percentage of the population with fimS in the On orientation compared to other sequence types. While three out of the four ST131 strains did have higher levels of fimA expression compared to the clinical isolate comparator (ST648), they did not have a higher percent of the population with fimS in the On orientation. These data suggest that the individual ST131 bacterium with fimS in the On orientation are upregulating fimA expression compared to the individual bacterium of the comparator strain. Decreases in outer membrane protein X (OmpX) have been implicated in increased type-1-fimbriae adhesion in E. coli lab strains. Therefore, I evaluated fimA expression in a lab parent strain and an ompX knockout strain. I also evaluated ompX expression in clinical isolates, including the ST131 strains, to compare changes in ompX expression with changes in fimA expression. While fimA expression increased in the ompX knockout strain, none of the ST131 strains showed a change in ompX expression compared to the clinical isolate comparator. The OmpC and OmpF protein production in the isolates from this study had previously been evaluated by doctoral candidate Corey Suelter. OmpC and OmpF form porins through which antibiotics can enter the cell. The ST131 strain with the greatest downregulation of OmpC had the highest percentage of fimS in the On orientation. To evaluate whether a decrease in either OmpC or OmpF impact fimA expression or the orientation of fimS, I evaluated fimA and the fimS orientation in ompC and ompF lab strain knockouts. The ompF knockout had the greatest increase in fimA expression and the percent of fimS in the On orientation. The ompC deletion clone showed an increase in the population with fimS in the On orientation while fimA expression in the population did not change. These data suggest that porins play a role in type-1-fimbriae production. Clinical isolates also contain plasmids with a variety of factors, including genes that encode antibiotic resistant enzymes such as ESBLs. The clinical isolates in this study, regardless of sequence type, with elevated levels of ESBL protein production had an increase in the percent of the population with fimS in the On orientation compared to the clinical isolate comparator. Taken together, these data suggest that ST131 clinical isolates differentially regulate type-1-fimbriae and that the regulation of this process is controlled by multiple mechanisms including OmpC protein production and perhaps unknown factors encoded on plasmids harboring ESBLs.