TABLE 2.

Physiological costs due to mutations in the 23S rRNA gene associated with Azmr in C. caviae SP6

C. caviae strain23S rRNA mutationaPlaque sizeb (mm)Duration of eclipse phase (h)cRate of 2-fold EB increase (min)c,eEB generation rate (fold increase)fCompetition indexg at indicated no. of passages
One (43 h p.i.)Two (86 h p.i.)h
SP6None (wild type)0.98 ± 0.1419201,530 ± 427NANA
SP6AZ1A2058C0.65 ± 0.1319-22d29113 ± 510.15 ± 0.030.06 ± 0.01
SP6AZ2A2059C0.46 ± 0.172221.6256 ± 940.28 ± 0.050.17 ± 0.07
  • a E. coli numbering system.

  • b The sizes of a minimum of 34 individual plaques were determined for each strain in the absence of antibiotic at 7 days p.i. and averaged.

  • c Data obtained from Fig. 1.

  • d The eclipse phase lasted for more than 19 h but less than 22 h.

  • e The rate of 2-fold EB increase was estimated as described in Materials and Methods.

  • f The number of IFU produced at 43 h p.i. divided by the number used at the time of infection was different for each of the three C. caviae strains (P < 0.0001; t test).

  • g The competition index is defined as the ratio of the output mutant/wild-type ratio at the indicated time p.i. to the input mutant/wild-type ratio. NA, not applicable.

  • h Determined after a second 43-h passage.