Ampicillin Resistance in Escherichia coli by Phage Infection

Abstract

BACTERIAL genes may become incorporated in the genome of phages and, as a consequence, are transmitted from one bacterium to another during lysogenization. Antibiotic resistance genes can be incorporated^2,3, and a naturally-occurring example—the phage concerned possessing genes for resistance to ampicillin—is described here. The phage lyso-genized a non-pathogenic strain of Escherichia coli (strain H) obtained from the faeces of a healthy human being who had never been treated with ampicillin. The minimum inhibitory concentration of ampicillin for this strain is 250 µg/ml.; it produced β-lactamase⁴.