Abstract
Since 1990 multiresistant (MR)
Salmonella enterica
serotype Typhimurium definitive phage-type (DT) 104 (MR DT104) and closely related phage types have emerged as a worldwide health problem in humans
and food animals. In this study the presence of the
bla
CARB-2
(ampicillin),
cmlA
(chloramphenicol),
aadA2
(streptomycin/spectinomycin),
sul1
(sulphonamide), and
tet
G
(tetracycline) resistance genes in isolates of one such phage type, U302, have been determined. In addition
bla
TEM
primers have been used for the detection of TEM-type beta-lactamases.
Isolates have also been characterized by plasmid profile and pulsed field gel electrophoresis (PFGE). Thirty-three of 39 isolates were positive for
bla
CARB-2
,
cmlA
,
aadA2
,
sul1
and
tet
G, four for
bla
TEM
,
aadA2
and
sul1
, one for
aadA2
and
sul1
, and one for
bla
TEM
only.
bla
TEM
-mediated
ampicillin resistance was transferred to
Escherichia coli
K12 from three isolates along with other resistance markers, including resistance to chloramphenicol, streptomycin, spectinomycin, sulphonamides,
and tetracyclines. Strains carried up to 6 plasmids and 34 plasmid profiles were identified. Although the majority of strains (33/39) produced a PFGE profile identical to that predominant in MR DT104, six
different patterns were generated demonstrating the presence of various clones within MR U302. The results show that the majority of the MR U302 strains studied possessed the same antibiotic resistance
genes as MR DT104. However, isolates with distinctive PFGE patterns can have different mechanisms of resistance to ampicillin, chloramphenicol, streptomycin, sulphonamides, and tetracyclines. Such resistance
genes may be borne on transmissible plasmids.