The evaluation of the synergistic antimicrobial and antibiofilm activity of AamAP1-Lysine with conventional antibiotics against representative resistant strains of both Gram-positive and Gram-negative bacteria

Figures & data

Figure 1 Time-kill curves for AamAP1-Lysine-antibiotic combinations against (A) S. aureus ATCC 29213, (B) S. aureus ATCC 33591 and (C) P. aeruginosa ATCC BAA2114. Data represent the average of three different experiments.

Abbreviations: ATCC, American Type Culture Collection; MIC, Minimum Inhibitory Concentration; CFU, Colony Forming Unit.

Table 1 Minimum inhibitory concentrations (MICs) of AamAP1-Lysine and the antibiotics individually against the tested bacterial strains. Results represent triplicates

MIC (µM)
Antimicrobial agent	S. aureus (ATCC 29213)	S. aureus (ATCC 33591)	P. aeruginosa (ATCC 27853)	P. aeruginosa (ATCC BAA2114)
AamAP1-Lysine	3 µM	3 µM	35 µM	35
Levofloxacin	0.5 µM	10 µM	7.5 µM	12
Chloramphenicol	20 µM	130 µM	350 µM	200
Rifampicin	0.025 µM	0.04 µM	45 µM	50
Ampicillin	2.5 µM	85 µM	>500 µM	>500 µM
Erythromycin	0.5 µM	8 µM	150	125

Table 2 Minimum inhibitory concentrations (MICs) of AamAP1-Lysine and the antibiotics in combination against Gram-positive and Gram-negative bacteria. Results represent triplicates

Individual MIC values of AamAP1-Lysine and the antibiotics in combination (µM)
Antimicrobial agent	S. aureus (ATCC 29213)	S. aureus (ATCC 33591)	P. aeruginosa (ATCC 27853)	P. aeruginosa (ATCC BAA2114)
AamAP1-Lysine/levofloxacin	0.01/0.5 µM	0.01/1 µM	0.5/5 µM	1/10 µM
AamAP1-Lysine/Chloramphenicol	0.01/18 µM	0.01/25 µM	5/300 µM	0.5/80 µM
AamAP1-Lysine/Rifampicin	0.01/0.005 µM	0.01/0.005 µM	15/15 µM	0.5/80 µM
AamAP1-Lysine/Ampicillin	0.01/1.5 µM	0.01/75 µM	0.1/NA* µM	0.1/NA* µM
AamAP1-Lysine/Erythromycin	0.001/0.1 µM	2/7 µM	0.5/100 µM	5/100 µM

Note: *NA: Not achieved.

Table 3 The fractional inhibitory concentration (FIC) indices of the antimicrobial combinations.

FIC Index
Antimicrobial combination	S. aureus (ATCC 29213)	S. aureus (ATCC 33591)	P. aeruginosa (ATCC 27853)	P. aeruginosa (ATCC BAA2114)
AamAP1-Lysine-Levofloxacin	1.00	0.103	0.674	0.36
AamAP1-Lysine-Chloramphenicol	0.903	0.963	0.99	0.36
AamAP1-Lysine-Rifampicin	0.203	0.128	0.75	0.88
AamAP1-Lysine-Ampicillin	0.603	0.885	NA*	NA*
AamAP1-Lysine-Erythromycin	0.204	1.541	0.674	0.84

Note: * Not applicable.

Table 4 The MBEC values and the FIC index of the successful synergistic combinations of AamAP1-Lysine combined with antibiotics

Individual MBEC				MBEC in combination (µM)
Bacterial strain	Antibiotics		AamAP1-Lysine	Antibiotics		AamAP1-Lysine	FIC
S. aureus (ATCC 33591)	Rifampicin	>500 µM	60 µM	Rifampicin	2.5 µM	1 µM	0.058
P. aeruginosa (ATCC BAA2114)	Levofloxacin	>500 µM	70 µM	Levofloxacin	5 µM	2.5 µM	0.110

Abbreviation: ATCC, American Type Culture Collection.

Figure S1 High-performance liquid chromatography analysis of AamAP1-Lysine

Figure S2 ESI-MS analysis of AamAP1-Lysine identifying displaying major peaks in the +2, +3, +4 and +5 charge state of 1053.70, 702.85, 527.40 and 422 Da, respectively