Table 3.

Intestinal colonization, CTX-KmΦ phage transduction, and CT release

StrainMouse CIa (no. of mice)CTX-KmΦ transductionbCT productioncHAP secretiond
P27459 -S (lac+)1.6 (3)+++
P27459galU0.03 (5)+++
P27459res290.01 (6)+++
P27459res29/pACYC1770.01 (6)NDeNDND
P27459res29/pACYCgalU1.94 (5)NDNDND
P27459 ΔgalE::cm0.96 (6)+++
P27459 ΔwbeW0.024 (5)+++
P27459 ΔwbeW/pJNwbeW0.8 (4)NDNDND
P27459res46, P27459res118f<10−4 (5)+++
  • a The competitive index (CI) for colonization is defined as the output ratio of mutant to wt bacteria divided by the input ratio of mutant (lac+) to wt bacteria (lac). Strains P27459galU, P27459res29, P27459res29/pACYC177, P27459 ΔwbeW, and P27459res46 had significant differences in colonization compared to the wt strain (P27459 ) as determined by Student's two-tailed ttest (P < 0.01) ; all other strains showed less significant differences (P > 0.01) . In vitro competition assays were also done for galU mutants: P27459res29, CI 0.7; P27459res29/pACYC177, CI 4.7;P27459galU, CI 1. The in vitro CIs demonstrate thatgalU mutants had no handicap or growth defect versus the wt under in vitro conditions.

  • b Determined in triplicate (Materials and Methods). The frequency of transduction ranged from 10−4to 10−5, with no significant differences between the strains tested.

  • c Measured in duplicate (Materials and Methods). The levels of CT present found in the culture supernatants were between 0.5 and 2 μg ml−1/OD600, with no significant differences between the strains tested.

  • d Detected as a zone of clearing on 1% nonfat milk agar plates.

  • e ND, not determined.

  • f Mouse colonization assays were initially performed with strain P27459res46, an R-LPS mutant which lacks O antigen and has an altered core, like P27459res118. All other experiments were done with strain P27459res118. To preserve mice, we did not repeat the colonization assays with strain P27459res118.