TABLE 3.

Accumulation of antibiotics in macrophages and calculated C_c-to-MIC ratios^a

Antibiotic	Cc/Ceb		Cc/MICc
	Noninfected cells	Infected cells
Ampicillin	0.93 ± 0.20 (12)	0.92 ± 0.19 (12)	153
Meropenem	0.96 ± 0.19 (12)	1.00 ± 0.36 (12)	694
Ciprofloxacin	7.36 ± 0.66 (6)	7.75 ± 1.03 (6)	24
Moxifloxacin	8.22 ± 0.87 (6)d	6.96 ± 1.05 (6)e	48

^aThe cells were incubated in the presence of the maximum extracellular concentrations tested in this study (ampicillin, 50 mg/liter; meropenem, 50 mg/liter; ciprofloxacin, 4.3 mg/liter; moxifloxacin, 4 mg/liter), and the levels of accumulation were determined after 5 h of incubation.

^bThe C_c-to-C_e ratio was calculated from the drug contents per milligram of cell protein by using a conversion factor of 5 μl per mg of cell protein the numbers of independent determinations are given in parentheses.

^cRatio of apparent C_c to the MIC (Table 1).

^dFluorescence assay; an independent assay with [¹⁴C]moxifloxacin gave a value of 8.45 ± 1.56 (n = 6).

^eP < 0.05 by statistical analysis by Student's t test (none of the other differences between uninfected and infected cells was significant).