Escherichia coli intestinal infection pathotypes are characterized by distinct adhesion patterns including the recently described clumpy adhesion phenotype. Here we identify and characterize genetic factors contributing to clumpy adhesion of E. coli strain 4972. In this strain, the transcriptome and proteome of adhered bacteria were found distinct from planktonic bacteria in supernatant. A total of 622 genes in the transcriptome were differentially expressed in bacteria present in clumps relative to the planktonic bacteria. Seven genes targeted for disruption had variable distribution in different pathotypes and nonpathogenic E. coli with pilV and spnT genes being the least frequent or absent from most groups. Deletion (Δ) of five differentially expressed genes, flgH, ffp, pilV, spnT and yggT affected motility, adhesion or antibiotic stress. ΔflgH exhibited 80 % decrease and ΔyggT depicted 145.5 % increase in adhesion, and upon complementation, adhesion significantly reduced to 13 %. ΔflgH lost motility and was regenerated when complemented whereas Δffp had significantly increased motility and reintroduction of the same gene reduced it to the wild-type level. The clumps produced by of Δffp and ΔspnT were more resistant and protected the bacteria with ΔspnT showing the best clump formation in terms of ampicillin stress protection. ΔyggT had the lowest tolerance to gentamicin where the antibiotic stress completely eliminated the bacteria. Overall, we were able to investigate the influence of clump formation on the cell surface adhesion and antimicrobial tolerance with the contribution of several factors crucial to clump formation on susceptibility to the selected antibiotics.