TABLE 4.

Internalization of S. aureus by A549 cells^a

S. aureus strain or mutantb,c	CFU/monolayer	CFU/monolayer (S. aureus plus Res)d
RN6390	(2.4 ± 0.005) × 106	(2.2 ± 0.008) × 106
QT7 (tet38::cat)	(0.4 ± 0.001) × 106	(0.3 ± 0.015) × 106
QT7 (pLI50)	(0.3 ± 0.015) × 106	(0.3 ± 0.010) × 106
QT7 (pLI50-tet38)	(2.5 ± 0.001) × 106	(1.2 ± 0.015) × 106
QT7 (pLI50-tet38-R106C)	(2.0 ± 0.002) × 106	(1.5 ± 0.020) × 106
QT7 (pLI50-tet38-G151C)	(2.3 ± 0.008) × 106	(1.3 ± 0.012) × 106
QT7 (pLI50-tet38-ΔL1)	(2.1 ± 0.001) × 106	(2.0 ± 0.011) × 106
QT7 (pLI50-tet38-ΔL7)	(0.5 ± 0.002) × 106	(0.4 ± 0.020) × 106

^aExperiments were done in triplicate and with three separate biological samples. The differences between the tet38 overexpressor and tet38-ΔL7 overexpressor in QT7 were statistically significant as determined by a Student's t test (P < 0.05). The differences between the tet38 overexpressor in QT7 in the absence or presence of reserpine were statistically significant as determined by a Student's t test (P < 0.05).

^bAll strains harboring plasmid pLI50 were grown in the presence of chloramphenicol 20 μg/ml at 37°C.

^cQT7, tet38 mutant. QT7 transformed with plasmids carrying the wild-type or mutated tet38 gene are given in parentheses.

^dRes, reserpine at 50 μg/ml final concentration.