FIGURE 5.

Effect of GSH, GSSG and H₂O₂ at neutral pH on MRAB biofilm viability. (A) 30 mM GSH (buffered to pH 7) resulted in a small biofilm viability decrease (76–94% viable), while combination with amikacin enhanced the decrease significantly (47–55% viable) when compared to both control and 30 mM GSH (pH 7) alone. (B) 30 mM GSSG alone and in combination with 4 μg/ml amikacin significantly decreased MRAB biofilm viability to 11–14% and 5–6%, respectively, when compared to control. (C,D) Standard H₂O₂ data used to determine H₂O₂ production by 10 and 30 mM GSH in 1 × PBS at intrinsic pH, and at buffered neutral pH 7. At intrinsic pH, GSH produced significantly more H₂O₂ (higher fluorescent intensity) than at its corresponding neutral pH concentration. (E) H₂O₂ treatment showed variation in MRAB biofilm viability among isolates. When compared to control only, MRAB-1 and MRAB-3 isolates showed statistically significant decreases in biofilm viability at all H₂O₂ concentrations. However, for MRAB-2 and MRAB-4, biofilm viability was similar to control at all H₂O₂ concentrations. ^∗P < 0.05 compared to control ^∙P < 0.05 when compared to 30 mM GSH (A) and 30 mM GSSG (B) and #P < 0.05 when compared to all other conditions (D). Data represent the mean ± SD of n = 4 experiments performed in biological replicate.