TABLE 1.

Association and invasion of Caco-2 cells by wild-type L. monocytogenes 12067 and the isogenic flagellum and chemotaxis mutants

Growth temp (°C) and strain	Without centrifugation		With centrifugation
	No.a (%)b of cell-associated bacteria (CFU/ml)	No.a (%) of invading bacteria (CFU/ml)	No. (%) of cell-associated bacteria (CFU/ml)	No. (%) of invading bacteria (CFU/ml)
24
WT	(3.3 ± 0.1) × 106 (100)	(2.7 ± 0.3) × 105 (100)	(6.6 ± 0.5) × 106 (100)	(1.4 ± 0.4) × 106 (100)
ΔflaA mutant	(3.5 ± 0.6) × 105c (10.6)	(3.8 ± 0.5) × 103c (1.4)	(5.2 ± 0.4) × 106d (78.8)	(3.6 ± 0.9) × 105d (25.7)
ΔcheY mutant	(4.2 ± 0.2) × 105c (12.7)	(1.2 ± 0.2) × 104c (4.4)	ND	ND
ΔcheA mutant	(4.0 ± 0.3) × 105c (12.1)	(1.9 ± 0.1) × 104c (7.0)	ND	ND
ΔcheYA mutant	(4.1 ± 0.1) × 105c (12.4)	(1.6 ± 0.2) × 104c (5.9)	(5.0 ± 0.4) × 106d (75.8)	(8.4 ± 0.6) × 105d (60.0)
37
WT	(2.6 ± 0.2) × 105 (100)	(1.2 ± 0.3) × 105 (100)	ND	ND
ΔflaA mutant	(2.4 ± 0.2) × 105 (NS)e (92.3)	(1.1 ± 0.1) × 105 (NS) (91.7)	ND	ND
ΔcheYA mutant	(2.2 ± 0.1) × 105d (84.6)	(9.3 ± 0.7) × 104 (NS) (77.5)	ND	ND

^aAssociation and invasion assays were performed without or with centrifugation of the bacteria onto the monolayer. Bacteria were grown in BHI broth at either 24 or 37°C, and invasion assays carried out as described in Materials and Methods. Each experiment was repeated twice, and the mean number of associated (both attached and intracellular) and invading bacteria were recorded. Results are given as mean ± standard deviation.

^bThe values for association and invasion were normalized to the values for the WT strain (under identical culture and centrifugation conditions), which were arbitrarily set at 100.

^cSignificantly different from the WT strain under identical culture and centrifugation conditions (P < 0.001).

^dSignificantly different from the WT strain under identical culture and centrifugation conditions (P < 0.005).

^eNS, not significantly different from the WT strain under identical culture and centrifugation conditions.