THE EFFECTS OF QUINOLONES ON THE ADHERENCE OF TYPE-1 FIMBRIATED ESCHERICHIA-COLI TO MANNOSYLATED AGAROSE BEADS

Bacterial adherence is reported to be antagonized by several classes o f antibiotics including quinolones, beta-lactams and tetracyclines, ba sed primarily on in-vitro studies in which bacterial cells are exposed to antimicrobials, incubated in the presence of uroepithelial cells ( UECs) and assessed for adherence by light microscopy. Some problems as sociated with the use of this approach, include low sensitivity, high variability and, in the case of adherence of mannose-sensitive Escheri chia coil interference by mannose-containing uromucoid. To avoid these problems, mannosylated agarose beads (MABs) were used as a model for UECs. Adherence of E. coli strain AAEC356, which is constitutive for t ype-1 fimbrial expression, was maximal with 3 x 10(4) beads/mL and 1 x 10(8) bacterial cells/mL co-incubated for 35 min at 37 degrees C. Tho se bacterial cultures showed 40-60% adherence to MABs but only 4-10% a dherence to UECs. This study reports a novel method to detect mannose- sensitive bacterial adherence, using MABs, in order to determine the e ffects of quinolones, cefdinir and tetracycline on E. coil adherence. Cefdinir and the quinolones ciprofloxacin, enoxacin and PD131628 cause d significant reductions in the adherence of AAEC356 to UECs at concen trations equivalent to 1/2 x MIG, while up to I x MIC of these antibio tics had no significant effect on adherence to MABs. A direct comparis on of UEC to MAB-based techniques showed that PD131628, at concentrati ons equivalent to 1/16x, 1/4x, 1/2x and 1 x MIG, had no effect on bact erial adherence to MABs, while reductions of 34%, 38%, 87% and 85% res pectively were seen in adherence to UECs. The anti-adherent effect med iated by quinolones may not therefore be related to the specific inter action between type-1 fimbriae and mannosylated receptors. While quino lones and cefdinir had no effect on overall bacterial adherence to MAB s, there was a decrease in the ability of alpha-methyl-D-mannoside (al pha-MM) to inhibit competitively this adherence. Concurrent exposure o f PD131628 or cefdinir with tetracycline prevented this, suggesting th at protein synthesis is required for this effect.