Chymotrypsin both directly modulates bacterial growth and asserts ampicillin degradation-mediated protective effect on bacteria

Recent studies have shown that some serine protease family members may play an important role in antibacterial activity. Chymotrypsin, a major member of the serine protease family, was used in our study to investigate whether it has a similar function. Optical absorbance, broth microdilution and scanning electron microscopy (SEM) assays were carried out to investigate the direct effect of chymotrypsin on bacteria. A disk diffusion test and LC-MS spectrometry were then used to investigate the effect of chymotrypsin on antibacterial activity of ampicillin. Chymotrypsin exhibited potentially antimicrobial properties to two kinds of Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis). However, the existence of chymotrypsin could also hinder the antibacterial activity of ampicillin, in part because chymotrypsin could degrade ampicillin in a dose-dependent manner. These results could be helpful in guiding current commercial usages of chymotrypsin and devising better strategies of clinical applications.