Ga. Dykes et Jw. Hastings, FITNESS COSTS ASSOCIATED WITH CLASS IIA BACTERIOCIN RESISTANCE IN LISTERIA-MONOCYTOGENES B73, Letters in applied microbiology, 26(1), 1998, pp. 5-8
In order to assess the potential for the spread of class IIa bacterioc
in resistance in natural populations of Listeria monocytogenes, the fi
tness costs associated with resistance to leucocins A, B and E and sak
acin A in L. monocytogenes B73 in the absence of bacteriocin were exam
ined. The resistant phenotype had a lower growth rate (and thus relati
ve fitness) than the sensitive phenotype in monoculture experiments. F
urthermore, resistant phenotypes were unable to invade populations of
the sensitive strain, even at frequencies of 10(-1) or higher, when gr
own in co-culture. These results held true for resistant strains that
had been exposed to bacteriocin for 25 successive growth cycles. It wa
s concluded that the class IIa bacteriocin-resistant phenotype of L. m
onocytogenes B73 is unlikely to become stable in natural populations b
ased on this evidence. Due to the possibility of variations in the fre
quencies of spontaneous mutation and fitness among Listeria strains, h
owever, the extrapolation of these results to the species as a whole s
hould not be made.