“Melnykowycz and Johansson (…) have shown that chlortetracycline suppresses amino acid decarboxylation by intestinal microorganisms in the rat, formation of lysine decarboxylase in Escherichia coli, and decarboxylation of tyrosine in Streptococcus faecalis R. These workers postulate that antibiotics reduce enterotoxemia and improve growth by inhibiting amine formation in the intestine.”