Growth and survival of E. coli O157:H7 during the manufacture and ripening of a smear-ripened cheese produced from raw milk.
OBJECTIVE
The behaviour of Escherichia coli O157:H7 was studied during the manufacture and ripening of a smear-ripened cheese produced from raw milk.


RESULTS
Cheese was manufactured on a laboratory scale using milk (20 l) inoculated with E. coli O157:H7, and enumeration was carried out using CT-SMAC. From an initial level of 1.52 +/- 0.03 log cfu ml-1 in the milk (34 +/- 2 cfu ml-1), the numbers increased to 3.4 +/- 0.05 log cfu g-1 in the cheese at day 1. During ripening, the numbers decreased to <1 cfu g-1 and <10 cfu g-1 in the rind and core, respectively, after 21 days, although viable cells were detected by enrichment after 90 days. The presence of E. coli O157:H7 in the cheese was confirmed by latex agglutination and by multiplex PCR.


CONCLUSIONS
The results indicate that the manufacturing procedure encouraged substantial growth of E. coli O157:H7 to levels that permitted survival during ripening and extended storage.


CONCLUSIONS
The presence of low numbers of E. coli O157:H7 in milk, destined for raw milk cheese manufacture, could constitute a threat to the consumer.
Maher
M M
MM
Teagasc, Dairy Products Research Centre, Moorepark, Fermoy, Ireland.
Jordan
K N
KN
Upton
M E
ME
Coffey
A
A
D000818:Animals; D002611:Cheese / Q000382:microbiology*; D015169:Colony Count, Microbial; D003470:Culture Media; D019453:Escherichia coli O157 / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D005285:Fermentation; D008892:Milk / Q000382:microbiology*; D016133:Polymerase Chain Reaction
D003470:Culture Media