Table 2.

Nasopharyngeal colonization of BALB/cByJ mice by A66 derivativesa

Strain (phenotype)Capsule production (± SEM)bColonizationcNasal washd log CFU (± SEM)
A66 (type 3 parent)100 (11.2)8/153.68 (0.25)
AM161 (insertion control)82 (1.8)3/43.32 (0.34)
AM179 (ΔCps3UM)87.7 (4.5)4/53.41 (0.30)
AM188 (Cps3Dr)19.2 (3.3)17/253.19 (0.14)
AM199 (Cps3S)00/10e
A66 + AM188Cps+/Cpsr3/10 (both)f4.32 (0.20) (A66)
3.85 (0.29) (AM188)
2/10 (A66)402 (0.20)
AM161 + AM199Cps+/Cps0/10e (both)
6/10 (AM161)3.60 (0.31)
  • a Mice were inoculated i.n. with 107 bacteria.

  • b Cell-associated capsule levels were determined using the Strains-All assay. Values are the percentages of capsule produced ± standard errors of the means relative to the parent A66 and represent the means of at least four independent determinations. A66 produced 41.5 ± 4.7 μg of capsule/ml of culture/unit of optical density at 600 nm. Capsule production by AM188 was significantly different from that by A66 (P = 0.0004) . AM199 was nonreactive with antibody to type 3 polysaccharide, and its Stains-All value was subtracted as background from the other samples. Cps+, parental levels of capsule; Cpsr, reduced capsule production; Cps, nonencapsulated.

  • c Values are the numbers of mice colonized per total numbers of mice. Except as noted, none were significantly different from values for A66.

  • d Values are the log CFU per milliliter (± standard errors of the means) recovered from nasal washes. The total volume of the wash was ∼200 μl, and the minimum detectable number of bacteria was 10 CFU per wash, equivalent to 50 CFU/ml. Em dashes indicate that no bacteria were recovered from any of the mice. Where bacteria were recovered, none of the values were significantly different from those for A66. The colony morphologies of bacteria recovered from the nasal washes were identical to those of the bacteria in the inocula.

  • e Significantly different from value for A66 (P < 0.05) .

  • f The presence of both strains was distinguished by colony morphology.