infections caused byS. Enteritidis PT4 decreased from 10,056 in 1998 to
2693 in 2003. Hidden by the overall figures however there was an almost
doubling of infections caused byS. Enteritidis non PT4 from 3548 in
2000 to 7065 in 2003. This was attributed to imported raw shell eggs used
largely in catering.
Salmonella Typhimurium definitive phage type (DT) 104 emerged
initially in cattle in the UK but has since been reported in poultry,
sheep, pigs and horses. It is now the second most prevalent salmonella in
humans in England and Wales with reported isolations increasing more
than 16 fold to 4006 in 1996. Ninety six percent of isolates in 1996 were
multiresistant, displaying resistance to four or more antimicrobials.
Twenty one percent were R-type ACSSuSpT which have chromo-
somal resistance genes to Ampicillin, Chloramphenicol, Streptomycin,
Sulphonamide,Spectinomycin andTetracyclines. Since 1994 there has
been an increasing number of isolates with additional resistances to
trimethoprim, nalidixic acid and to quinolone antibiotics such as cipro-
floxacin. Quinolones are used in the treatment of salmonellosis and
typhoid fever in humans and the emergence of resistance may be linked
to their veterinary use since 1993 to combat salmonellosis in cattle, pigs
and poultry. Increased isolation rates of multiresistant DT104 have also
been reported from other European countries, such as Germany where
DT104 accounted for more than 10% of 10 000 human isolates, and the
United States. The organism also appears to be unusually virulent since
hospitalization and fatality rates respectively twice and ten times those of
other foodborne salmonella infections have been reported.
Though the primary source appears to be foods of animal origin such
as poultry and unpasteurized milk, cross-contamination has led to a
bewildering variety of foods being implicated in DT104 outbreaks. These
include chicken drumsticks, tuna and salmon sandwiches, ham, cod roe,
scotch eggs, unpasteurized milk, roast beef, apple crumble and coleslaw.
Raw milk will inevitably containSalmonellaand any slight nutritional
advantage it may have over pasteurized milk is far outweighed by the very
real risk of salmonellosis (and campylobacteriosis). Outbreaks in a number
of countries have been associated with pasteurized milk that has been
inadequately processed or subject to post-process contamination.Salmo-
nellais unable to grow in dried milk but is able to survive and resume
growth when the milk is reconstituted.S. Ealing was responsible for an
outbreak in the UK in 1985 where the vehicle was a dried baby-milk. The
organism had contaminated the insulation surrounding a spray drier and
penetrated the drying chamber itself through a small defect in the chamber
wall. Rigorous cleaning and disinfection were unable to eliminate the
contamination from the spray drier which was eventually decommissioned.
Fish and fish products are only occasionally associated with salmon-
ellosis, although fish meal for animal feed often containsSalmonellaas a
248 Bacterial Agents of Foodborne Illness