TABLE 6.

Effect of endosome pH-neutralizing reagents on E. coli HB101(pRI203) intracellular survival^a

E. coli strain and additive	Growth phase	No. of intracellular bacteria at 2 h	Intracellular survival at:
			24 h	48 h
HB101(pRI203)	Logarithmic	(9.3 ± 0.9) × 105	(4.6 ± 0.5) × 103	0
HB101(pRI203) plus NH4Cl		(3.3 ± 0.7) × 105	(5.9 ± 3.3) × 103	0
HB101(pRI203) plus bafilomycin		(8.4 ± 0.7) × 105	(2.8 ± 0.8) × 103	0
HB101(pRI203)	Stationary	(3.2 ± 0.5) × 105	0	0
HB101(pRI203) plus NH4Cl		(3.8 ± 0.7) × 105	0	0
HB101(pRI203) plus bafilomycin		(2.6 ± 0.5) × 105	0	0

^aEffect of 20 mM NH₄Cl or 100 nM bafilomycin A₁ on invasion efficiency (number of intracellular bacteria at 2 h) and intracellular survival of E. coli HB101(pRI203) infecting HeLa cell monolayers at an MOI of 100. Values are the means ± standard deviations of four independent experiments.