Colicinogeny in Salmonella typhimurium.

Colicin types, Ia, Ib, E1, E2, B with M, K, S4 and a new salmonellin-like colicin were found in 531 (11.8%) of 4481 wild-type cultures of Salmonella typhimurium. Colicin typing added little useful information to phage typing and biotyping in strain differentiation, mainly because the most common types, Ia and Ib, are controlled by conjugative plasmids. Evidence from the mixed-Col-/Col+ pattern of colicinogeny in circumscribed outbreaks caused by strains of known phage type and biotype suggested that some Col factors are readily acquired by S. typhimurium from other enteric species. When a Col factor of the nonconjugative type, e.g. ColE2, becomes established in strains of successful phage type/biotype line, it may be a useful additional marker character.