A survey was made in 1995–1996 for Listeria spp. in 63 soft cheeses, made from raw ewe’s milk using traditional methods, in the
Province of Beira Baixa (Portugal). Listeria spp. were isolated from 47 (75%) of the cheeses, L.monocytogenes was isolated from 29
(46%), and L.innocua but not L.monocytogenes from 18 (29%). Of 24 isolates of L.monocytogenes that were serotyped, 20 were
serotype 4b, three were serotype 1/2b and one was serotype 1/2a. Phage typing of isolates of L.monocytogenes and L.innocua showed
that in some cases a particular phage type was associated with cheese from a particular source. Twenty four strains of
L.monocytogenes tested were able to grow at 30 Cin culture medium adjusted with HCl to a pH in the range from 4.4 to 6.0 within 3
days; in the pH range 4.4–6.8 a representative strain grew most rapidly at pH 6.8. The pH range in the cheeses during maturation
was between about 5.2–6.4. Whether L.monocytogenes could multiply in the cheeses would depend on factors such as concentration
of organic acids and of salt, and storage temperature. info:eu-repo/semantics/publishedVersion
