TABLE 1.

Summary of the effects of λ and gentamicin as extracellular killing agents on FimH⁺ or FimH⁻ E. coli bound to resident mouse peritoneal macrophages^a

Strain	Initial bactericidal rateb		Maximum % of internalized bacteria killedc		% of internalized bacteria surviving after 4 hc
	λ	Gentamicin	λ	Gentamicin	λ	Gentamicin
FimH+	3.5 ± 1.1d,e	10.9 ± 0.5e	45.2 ± 7.0d,e	94.6 ± 1.4e	548 ± 181e	4.4 ± 1.3e
FimH−	8.3 ± 1.2d	10.9 ± 0.4e	68 ± 5.6d,e	96.3 ± 1.0e	692 ± 275e	2.5 ± 0.4e

^aFimH⁺ strains ORN175 and ORN222 were mixed with their FimH⁻ counterparts (strains ORN204 and ORN223) and employed in BALB/c peritoneal macrophage binding and bactericidal assays as described in the text. All values represent the averages (± standard deviation) of at least four experiments performed in duplicate. Statistically significant differences between means were determined by Student's t test. P < 0.05.

^bThe initial bactericidal rate was measured as the percentage of internalized bacteria eliminated per 10 min as calculated from the negative slope of a regression line through at least three time points covering the first three assay time points (ca 1.25 h). Larger values indicate a more rapid decrease.

^cThe maximal percentage of internalized bacteria killed and the percentage of internalized bacteria surviving after 4 h are expressed as percentages of the internalized population. Values greater than 100% reflect growth of the internalized bacteria.

^dStatistically significant difference between the FimH⁺ and FimH⁻ samples with the same extracellular killing agent.

^eStatistically significant difference between λ and gentamicin as extracellular killing agents with the same bacterial sample.