@article{3046400,
    title = "MOLECULAR EPIDEMIOLOGY OF AMPICILLIN-RESISTANT CLINICAL ISOLATES OF
SALMONELLA-ENTERITIDIS",
    author = "VATOPOULOS, AC and MAINAS, E and BALIS, E and THRELFALL, EJ and and KANELOPOULOU, M and KALAPOTHAKI, V and MALAMOULADA, H and LEGAKIS, NJ",
    journal = "Journal of Clinical Microbiology",
    year = "1994",
    volume = "32",
    number = "5",
    pages = "1322-1325",
    publisher = "AMER SOC MICROBIOLOGY",
    issn = "0095-1137, 1098-660X",
    doi = "10.1128/JCM.32.5.1322-1325.1994",
    abstract = "During the last 6 years in Greece, there has been a significant increase
in the number of ampicillin-resistant Salmonella clinical isolates
reported. In this study 23 ampicillin-resistant Salmonella strains,
consecutively isolated from patients with epidemiologically unrelated
cases of food poisoning, sere investigated. By serotyping and phage
typing, 21 of these strains were identified as Salmonella enteritidis
phage type 6a, 1 was identified as Salmonella typhimurium, and 1 was
identified as Salmonella saintpaul. By plasmid pattern analysis, the 21
S. enteritidis strains were further differentiated into five groups.
Group I consisted of 5 strains (carrying two plasmids of ca. 38 and 34
MDa), group II consisted of 10 strains (three plasmids of ca. 38, 34,
and 2.5 MDa), group III consisted of 3 strains (four plasmids of ca. 38,
34, 15, and 2.5 MDa), group IV consisted of 1 strain (five plasmids of
ca. 100, 38, 34, 24, and 15 MDa), and group IV consisted of 2 strains
(three plasmids of ca. 100, 38, and 24 MDa). Ampicillin resistance was
easily transferred to Escherichia coli and was associated with the
transfer of the 3 I-R MDa plasmid, classified in the N incompatibility
group for all strains of groups I to IV, and with the transfer of the
100-MDa plasmid for the group V strains. EcoRI restriction endonuclease
digestions showed an extensive homolog among the 34-MDa conjugative R
plasmids. Hybridizations of the EcoRI restriction fragments of the
34-MDa plasmids with a TEM-type probe revealed the locus of the
beta-lactamase gene to be situated on a ca. 6.6-MDa fragment, common in
all plasmids. These results indicate that ampicillin resistance in
Greece is due to the spread of a limited number of clones of S.
enteritidis phage type 6a, carrying related 34-MDa R plasmids. Work is
in progress to obtain a better understanding of ampicillin resistance in
S. enteritidis."
}