From May to June 2003, a total of 14 human cases of multidrug-resistant
Salmonella enterica subsp.
enterica serotype Newport
were reported in a localised geographical area in the north of France (figures
1 and 2). The serotype was resistant to beta-lactams (ampicillin, ticarcillin,
piperacillin, 1st, 2nd and 3rd generation cephalosporins except cefepime and
imipenem), streptomycin, sulfonamide, tetracycline, and chloramphenicol. Both
sexes (sex-ratio = 1) and all age groups (9 children, 5 adults) were affected
(mean age =24 years). All patients presented with diarrhoea, which was bloody
in seven patients (50%). Eleven patients were hospitalised (79%). No death
has been recorded.
Figure 1. Cases by day of onset. S. Newport outbreak,
France, May-June 2003.
Figure 2. Cases by place of residence. S. Newport
outbreak, France, May-June 2003.
All cases reported having eaten horsemeat consumed as ground meat (11 cases,
and consumed raw by at least 6 cases) or steak (3 cases). Cases had purchased
their horsemeat from butchers (7 cases) and markets (7 cases) in different
towns. Among the different suppliers of the retail outlets, one wholesaler,
located in the north of France, was shown to have supplied all fourteen
outlets. The wholesaler purchases its horsemeat from 6 different countries
outside France, predominantly in South and North America, but also in Europe
and Oceania.
So far, no single vehicle of infection (common carcass or common supplier
abroad) has been identified. Since the origin of the horsemeat is not recorded
after purchase by the wholesaler, it may prove impossible to determine the
exact origin of the contaminated meat.
Fourteen isolates were tested for the presence of blaCMY
gene by PCR. All the isolates were positive in a CMY-specific PCR assay.
Sequencing of PCR products showed a beta-lactamase gene identical to cmy-2.
Data from routine Salmonella surveillance on humans and domestic
animals (primarily poultry, pigs and cattle) and foods showed that S.
Newport isolates with the current outbreak resistance profile are very
unusual in France. Four isolates have been identified in humans 2000 (n=3)
and 2002 (n=1) and none in animals aand foods.
The CMY-2 gene is a AmpC-like beta lactamase plasmid mediated gene, inducing
resistance to cephamycin and extended- spectrum cephlosporins. The CMY-2
plasmid can undergo transfer between different bacterial species (E.
coli, Klebsiella sp, Salmonella sp, etc) and be transmitted between
food, animals and humans (1-3). In the United States, the incidence of S.
Newport human illness increased markedly in the late 1990s (4). The increase
in S. Newport illness in human has been driven by an increase in the highly
resistant strain S. Newport MDR-AmpC (4). Illness due to S.
Newport MDR-AmpC is also emerging in cattle. Risk factors for human
illness include contact with cattle and consumption of bovine products.