Modulation of Antibiotic Activity against Pseudomonas aeruginosa by N-Acetylcysteine, Ambroxol and Ascorbic Acid

The possible synergy between antibiotics and each of N-acetylcysteine (NAC), ambroxol and ascorbic acid against five clinical isolates of Pseudomonas aeruginosa was evaluated. Synergy was found with 50% of isolates. NAC showed higher synergy than ambroxol and ascorbic acid. The synergy rates were 80%, 55% and 15% for NAC, ambroxol and ascorbic acid, respectively. Combinations of NAC with each of cefepime, ceftazidime, cefoperazone and meropenem and those of tetracycline with each of NAC and ambroxol showed the highest synergy. NAC showed synergy with all combinations except with levofloxacin with which indifference was found. The synergy rates were higher with β-lactam antibiotics. Antagonism was observed with gentamicin. Ambroxol showed stronger synergy with tetracycline, chloramphenicol and cefepime than with ceftazidime, meropenem, levofloxacin and cefoperazone. Indifference was found with gentamicin, levofloxacin, cefoperazone, ceftazidime, chloramphenicol, cefepime and meropenem. On the other hand ascorbic acid showed weak synergistic activity. Ascorbic acid could only potentiate chloramphenicol, meropenem, cefepime and cefoperazone. Indifference was found with levofloxacin, cefepime, ceftazidime, gentamicin, tetracycline, chloramphenicol and meropenem. These results suggest the use of combinations of NAC, ambroxol and ascorbic acid with antibiotics to combat the antibiotic resistance of Pseudomonas aeruginosa.