“…A basic requirement for this type of DNA transfer to occur in vivo is the co-colonization of the nasopharynx with different neisserial strains, serogroups and commensals. Although it has not been a standard clinical procedure to culture additional neisserial species and strains when isolating N. meningitidis, when it is attempted, genetically distinct Neisseria can be isolated from an individual (Schoenbach and Phair, 1948;Knapp, 1988;Knapp and Hook, 1988;. Thus, there is evidence of cocolonization of the human nasopharynx by more than one neisserial species or strain (Schoenbach et al, 1948;Knapp, 1988;Knapp and Hook, 1988;, in vivo horizontal exchange among Neisseria (Seifert et al, 1988;Spratt et al, 1992;Bowler et al, 1994;Swartley et al, 1997;Zhou et al, 1997;Linz et al, 2000;Qvarnstrom and Swedberg, 2002), and increased phase variation frequencies in the presence of heterologous neisserial DNA (this study).…”