BioMed Research International

Research Article

In Vitro Bactericidal Activity of 4- and 5-Chloro-2-hydroxy-N-[1-oxo-1-(phenylamino)alkan-2-yl]benzamides against MRSA

Table 3

Change in viable counts (log10 CFU/mL) of MRSA and S. aureus strains following incubation for 24 h with 5-chloro-2-hydroxy-N-[(2S)-3-methyl-1-oxo-1-{[4-(trifluoromethyl)-phenyl]amino}butan-2-yl]benzamide (1f), N-{(2S)-1-[(4-bromophenyl)amino]-3-methyl-1-oxobutan-2-yl}-4-chloro-2-hydroxybenzamide (1g), and 4-chloro-N-{(2S)-1-[(3,4-dichlorophenyl)amino]-3-methyl-1-oxobutan-2-yl}-2-hydroxybenzamide (1h) (bactericidal effect is expressed in bold).
StrainMIC/MBCConc.Log10 difference in CFU/mL from inoculum
4 h6 h8 h24 h
Comp. 1f      
 MRSA 637184/41× MIC0.340.560.661.68
2× MIC−3.08a−3.33−3.75−2.40b
4× MIC−5.30−5.30−5.30−5.30
 MRSA SA 6302/41× MIC0.651.161.360.65
2× MIC−0.26−0.77−1.40−2.07
4× MIC−0.83−3.26−2.52−3.22
 MRSA SA 32022/81× MIC1.211.561.751.57
2× MIC0.06−0.05−0.65−1.59
4× MIC−0.07−1.05−2.70−3.30
 S.a. 2/41× MIC0.821.001.141.21
2× MIC−0.25−0.74−1.52−2.52
4× MIC−1.17−2.85−3.88−3.65
Comp. 1g      
 MRSA 637188/161× MIC0.430.650.750.95
2× MIC−2.54−3.23−3.15−0.76
4× MIC−3.18−3.58−3.10−2.24
 MRSA SA 6304/81× MIC0.981.421.570.55
2× MIC−0.12−0.73 −1.50−0.28
4× MIC−1.00−1.54−2.37−3.38
 MRSA SA 32024/81× MIC0.561.471.702.14
2× MIC−0.03−0.07−0.82−0.69
4× MIC−0.35−0.56−1.49−4.01
 S.a. 4/81× MIC1.021.101.451.57
2× MIC0.160.100.80−0.34
4× MIC−0.07−0.11−1.65−2.33
Comp. 1h      
 MRSA 637182/41× MIC−0.76−1.09−0.710.89
2× MIC−1.77−2.07−1.970.47
4× MIC−2.90−3.54−3.31−2.65
 MRSA SA 6301/11× MIC−0.27−0.10−0.091.42
2× MIC0.19−1.19−1.39−0.30
4× MIC−2.72−3.21−3.39−3.18
 MRSA SA 32021/41× MIC0.270.820.961.12
2× MIC0.17−0.27−0.53−0.09
4× MIC−0.35−1.13−1.83−3.02
 S.a. 1/21× MIC0.270.060.001.43
2× MIC0.04−0.35−0.94−1.20
4× MIC−0.34−1.29−2.62−2.61
CFU: colony-forming units; Conc.: concentration (multiplicity of MIC).
≥3  reduction in CFU implies a bactericidal effect.
<3  reduction in CFU implies a bacteriostatic effect.