Antimicrobial activities of aminoreductone (AR), a product formed in the initial stages of the Maillard reaction, were investigated using eight clinical isolates of antibiotic-susceptible/resistant pathogenic bacteria: four Pseudomonas aeruginosa, one multi-drug-resistant Pseudomonas aeruginosa (MDRP), one Escherichia coli, one methicillin-susceptible Staphylococcus aureus, and one methicillin-resistant Staphylococcus aureus (MRSA). AR showed advanced growth inhibition effects compared to antibiotics (amikacin, ciprofloxacin, imipenem and levofloxacin) frequently used for the treatment of infectious diseases, and worked synergistically with these antibiotics. The minimum inhibitory concentrations (MIC) of AR ranged from 13 to 20 mM. The bactericidal activity of AR was dose and time dependent. The minimum bactericidal concentration (MSC) was lower for Gram-negative bacteria (32 to 40 mM). These findings suggest that AR, a naturally formed antimicrobial agent present in thermally processed foods, has promising potential for health promotion and for use in medical practices.