The effect of biofilm inhibitor N-acetylcysteine on the minimum inhibitory concentration of antibiotics used in Gram-negative bacteria in the biofilm developed on catheters

The study determined the effect of N-acetylcysteine (NAC) on the susceptibility of various antibiotics used to treat Gram-negative catheter-related infection in isolates obtained from pediatric patients admitted to the hematology and oncology department of Medical Park Bahçelievler hospital in Istanbul, Turkey. Biofilms were created in vitro utilizing clinical isolates of Escherichia coli, Pseudomonas aeruginosa, Pseudomonas putida, and Proteus mirabilis. 24 h old biofilms were developed on 96-well plate with strains and the minimum biofilm inhibitory concentration (MBIC) of six antibiotics were measured before and after the addition of 75 mg/ml N-acetylcysteine with microplate reader at 450 nm after crystal violet assay. The addition of NAC reduce the MBIC of cefepime, ceftazidime, colistin, meropenem from (16, 16, 8, 4 μg/ml) to (8, 4, 4, 2 μg/ml) respectively in E. coli (isolate 1). In P. aeruginosa (isolate 4), the MBIC of amikacin, ceftazidime, meropenem (64, 32, and 32 μg/ml) reduced to (8, 1, and 0.5 μg/ml) respectively. MBIC of cefepime, colistin, meropenem (32, 16,and 16 μg/ml) reduced to (2, 2,and 0.5 μg/ml) respectively in P. putida (isolate 5). In P. mirabilis (isolate 6), MBIC of amikacin, cefepime, ceftazidime, colisitin and meropenem (64, 128, 32, 4, and 32 μg/ml) reduced to (8, 8, 1, 1, 4 μg/ml). NAC in combination therapy can practically reduce the MBIC of antibiotics used to treat Gram negative bacteria that develop biofilm in medical catheters. As a result, these combinations can be considered as an essential alternative for increasing the antibiotic susceptibility of pathogenic microorganisms and thus increasing treatment success rates.