However, a diversity of phenotypes was identified in the E. coli UTI isolates, including: (i) an absence of OmpF and increased efflux (isolates F14 and F18); (ii) no OM alterations but reduced accumulation due only to increased active efflux (isolates F5, F8 and F9); and (iii) decreased OmpF expression coupled with active efflux (isolate F13). The differential accumulation of ciprofloxacin by isolates F14 and F18 might be attributed to differences in LPS and/or potentially in MarR, which would affect the expression of the AcrAB efflux pump.