TABLE 3.

Mitomycin C-induced production of CTXΦ and RS1Φ in culture supernatants of RS1-positive toxigenic V. cholerae strains as assayed by the presence of different phage-specific DNAs in total nucleic acids extracted from phage preparations

V. cholerae strains	Yr of isolation	Source	No. of strains analyzed (n = 83)	No. of strains producing extracellular phage particles
				CTXΦ (n = 52)	RS1Φa (n = 32)
O1, El Tor	1969–2000	Patient	37	21	11
O1, El Tor	1998–2000	Sea water	6	2	2
O139	1993–1999	Patient	32	27	19
Non-O1 non-O139	1998–2001	Sea water	8	42	40

^aAll strains producing RS1Φ also produced CTXΦ.