Table 1.
Minimal Inhibitory Concentrations (MIC) of quinolones against the strains of the two isogenic systems derived from E. coli CFT073.
Table 2.
In vitro growth parameters for the strains of the first isogenic system based on E. coli CFT073 carrying pBR322 derivatives harboring qnrA3 or not.
Table 3.
In vitro growth parameters for the strains of the second isogenic system based on acquisition of the multidrug resistant qnrA3-positive plasmid pHe96.
Figure 1.
Cell size measured by flow cytometry for the strains of the two isogenic systems.
Each graphic compares size measurement for bacterial cell populations consisting of the reference susceptible strain E. coli CFT073 (in black) and of the tested strain : E. coli CFT073(pBR322) (qnr-negative) in red (part A), E. coli CFT073(pBRAM1) (qnrA3-positive) in yellow (part B), E. coli CFT073(pBRAM2) (qnrA3-positive) in pink (part C), E. coli CFT073-SmR (qnr-negative) in blue (part D), E. coli CFT073-SmR(pHe96) (qnrA3-positive) in green (part E) and its variant R42 in purple (part F). Measurements were made separately, not in a competitive assay.
Figure 2.
Enhanced fitness observed in competitive infections for E. coli CFT073 after qnrA3 acquisition onto pBR322.
Each symbol represents the bacterial ratio (number of CFU for the qnr-positive strain/number of CFU for the qnr-negative isogenic strain) measured in organs (blue diamond = kidneys, red circle = bladder) collected five and ten days after inoculation of a 1∶1 mix of the two strains. When the ratio was equal to 1+/−0.2, it was considered as tie. Part A: competitions experiments opposing E. coli CFT073(pBR322) (qnr−, tetA+) and E. coli CFT073(pBRAM2) (qnrA3+, tetA−). Fifteen mice were inoculated, 15 bladders and 10 pairs of kidneys were efficiently infected. Competition was won 22 times by E. coli CFT073(pBRAM2) (qnrA3+, tetA−), was lost 2 times, and one was tie (p<0.0001). Part B: competitions opposing E. coli CFT073(pBRΔtetA) (qnr−, tet−) and E. coli CFT073(pBRAM2) (qnrA3+, tet−). Twenty-three mice were inoculated, 20 bladders and 17 pairs of kidneys were efficiently infected. Competition was won 24 times by E. coli CFT073(pBRAM2) (qnrA3+, tetA−), was lost 9 times, and 6 was tie (p<0.0001).
Figure 3.
Single strain urinary tract infections with the isogenic system of E. coli CFT073-SmR harboring or not the multidrug resistance plasmid pHe96 (qnrA3).
Part A: Bacterial density (log10CFU/g of tissue) in bladders collected two, five and ten days after inoculation by E. coli CFT073-SmR (qnr−, purple plot), E. coli CFT073-SmR(pHe96) (qnrA3+, light green plot) and E. coli CFT073-SmR(pHe96) R42 variant (qnrA3+, dark green plot). At day 2, bacterial density was 6.79+/−0.35, 4.95+/−0.8 (p<0.0001), and 4.9+/−0.65 (p<0.0001), respectively; at day 5, it was 4.61+/−0.25, 3.24+/−0.3 (p<0.0001) and 3.79+/−0.5 (p = 0.03), respectively; and at day 10, 5.47+/−0.8, 2.91+/−0.6 (p = 0.0004) and 2.85+/−0.5 (p = 0.001), respectively. At least 10 mice were studied per group. Part B : Bacterial density (log10CFU/g of tissue) in kidneys collected two, five and ten days after inoculation by E. coli CFT073-SmR (qnr−, purple plot), E. coli CFT073-SmR(pHe96) (qnrA3+, light green plot) and E. coli CFT073-SmR(pHe96) R42 variant (qnrA3+, dark green plot). Results were respectively 4.29+/−0.53, 3.14+/−0.64 (p = 0.005) and 3.53+/−0.46 (p = 0.053) at day 2; 4.29+/−0.61, 2.94+/−0.6 (p = 0.02), and 4.23+/−0.43 (p = 0.06) at day 5; and 4.81+/−0.6, 3.26+/0.63 (p = 0.012 and 3.3+/−1.59 (p = 0.04) at day 10. At least 10 mice were studied per group.
Figure 4.
Reduced fitness observed after pHe96 acquisition in competitive infections in absence of antimicrobial exposure.
Each symbol represents the ratio (number of CFU for the qnr-positive strain/number of CFU for the qnr-negative isogenic strain) in organs (blue diamond = kidneys, red circle = bladder), collected five and ten days after inoculation of a 1∶1 mix of the two strains. Part A: competition experiments opposing E. coli CFT073-SmR (qnr−) and E. coli CFT073-SmR(pHe96) (qnrA3+). Twenty mice were inoculated, 19 bladders and 16 pairs of kidneys were efficiently infected. Competition was lost 33 times by E. coli CFT073-SmR(pHe96) (qnrA3+), and won only 2 times (p<0.0001). Part B: competition experiments opposing E. coli CFT073-SmR (qnr−) and E. coli CFT073-SmR(pHe96) variant “R42” (qnrA3+). The R42 variant was selected from kidneys that were infected by E. coli CFT073-SmR(pHe96). Twenty mice were inoculated, 18 bladders and 16 pairs of kidneys were efficiently infected. Competition was lost 33 times by the qnrA3-positive strain with only one won (p<0.0001).