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Volume 6, Number 4—August 2000

Dispatch

Antimicrobial Resistance in Salmonella Enteritidis, Southern Italy, 1990-1998

Antonino Nastasi*, Caterina Mammina†Comments to Author , and Lucia Cannova†

Author affiliations: *University of Florence, Florence, Italy; and †University of Palermo, Palermo, Italy

Article in Chinese

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Table

Resistance patterns of Salmonella Enteriditis strains, southern Italy, 1990–1998

Year Source Region Phage types Resistance patterna Plasmid pattern (mol. wt.,MDa) Resistance pattern of recipient Escherichia coli Integrons (size of inserted regions, kb)
1990 human Sicily RDNC Ap 36, 25
1991 cakeb Sicily 4 Su, Tp, Tc 80,c 36 Tp, Tc 2.5
1992 seafood Apulia 4 Ap 30 Ap
1992 seafood Apulia 4 Ap 36, 30 Ap
1992 human Sicily 4 Ap, Kf, Atm, Caz, Cro, Ctx, Su 30
1992 dog Sicily RDNC Ap, Kf, Sm, Su, Tc 30 Ap, Sm, Su, Tc
1992 human Calabria 4 Gm, Sm, Su 80, 70 0.8
1992 human Sicily RDNC Sm, Su, Tp 80, 36 Sm, Su, Tp
1992 human Calabria 1 Su, Tp, Tc 80, 36 Tp, Tc 1.5
1993 human Calabria 7 Gm, Sm, Tc 80 Tc
1993 human Sicily 4 Sm, Tc 80, 36 Tc
1993 human Sicily 4 Sm, Su, Tp, Tc 80, 36 Sm, Su, Tp, Tc
1993 human Sicily 7 Sm, Su, Tp, Tc 80, 36 Sm, Su, Tp, Tc
1994 human Sicily 4 Ap, Kf, Atm, Caz, Cro, Ctx, Su 80, 36 Ap, Kf, Atm, Caz, Cro, Ctx 2.0
1994 human Sicily RDNC Tc 36, 30 Tc
1994 human Sicily 4 Tc 36, 30 Tc
1995 human Calabria 4 Tc 36, 30 Tc
1995 human Apulia 4 Tc 80, 36 Tc
1995 human Apulia 7 Tc 36, 30 Tc
1996 human Sicily 4 Ap, Kf, Atm, Caz, Cro, Ctx, Su 80, 36 Ap, Kf, Atm, Caz, Cro, Ctx 2.0
1996 humanb Sicily RDNC Tc 36, 30 Tc
1996 human Apulia RDNC Tc 30 Tc
1997 human Sicily 4 Ap 36, 30
1997 human Sicily 4 Ap 36
1997 human Sicily 1 Ap 36, 30
1997 human Calabria 4 Ap, Kf, Atm, Caz, Cro, Ctx, Cm, Su 70, 36 Ap, Kf, Atm, Caz, Cro, Ctx, Cm
1997 human Calabria 4 Ap, Kf, Atm, Caz, Cro, Ctx, Cm, Su 38, 36 Ap, Kf, Atm, Caz, Cro, Ctx, Cm
1997 human Calabria RDNC Ap, Kf, Atm, Caz, Cro, Ctx, Cm, Su 80, 36 Ap, Kf, Atm, Caz, Cro, Ctx 2.0
1997 human Apulia 1 Ap, Sm, Tc 36, 30 Ap, Sm, Tc
1997 human Calabria 1 Ap, Sm, Tc 36, 32 Ap, Sm, Tc
1997 human Sicily 4 Cm, Su, Tp 36, 32 Cm, Su, Tp
1997 human Sicily 4 Su, Tp 36
1997 poultry Sicily 14b Tc 80, 36 Tc
1997 human Sicily 14b Tc 80 Tc
1997 human Sicily NT Tc 80 Tc
1997 human Sicily 13 Tc 80, 36 Tc
1997 human Sicily RDNC Tc, Nal 80, 36 Tc
1998 human Sicily 4 Ap 70, 36 Ap
1998 sewage Sicily RDNC Ap, Kf 36
1998 human Sicily RDNC Tc 36, 30 Tc
1998 human Sicily 7 Tc 30 Tc
1998 human Sicily 6a Tc 80, 36 Tc
1998 human Sicily RDNC Tc 36, 30 Tc
1998 poultry Sicily RDNC Tc 30 Tc

Ap, ampicillin; Kf, cephalotin; Atm, aztreonam; Caz, ceftazidime; Cro, ceftriaxone; Ctx, cefotaxime; Cm, chloramphenicol; Gm, gentamicin; Sm, streptomycin; Su, sulfonamides; Tp, trimethoprim; Tc, tetracycline; Nal, nalidixic acid; RDNC, reaction did not conform; NT, not typable.
aThe strains were screened for resistance to ampicillin (10 µg), cephalotin (30 µg), cefotaxime (30 µg), chloramphenicol (30 µg), ciprofloxacin (5 µg), gentamicin (10 µg), nalidixic acid (30 µg), streptomycin (10 µg), sulfonamides (300 µg), tetracycline (30 µg), and trimethoprim (5 µg). Strains resistant to cefotaxime were subsequently tested for susceptibility to aztreonam (30 µg), ceftazidime (30 µg), and ceftriaxone (30 µg). Resistance was determined by disk diffusion (4). The double-disk synergy test was performed (4) on strains presumed to produce extended-spectrum ß-lactamase (ESBL). Plasmid DNA was extracted by an alkaline lysis method (5). Electrophoresis on 0.7% agarose gels was performed on samples of plasmid DNA. The approximate molecular weight of plasmids was estimated by comparison with plasmids of known molecular size extracted from Escherichia coli. Conjugation experiments were carried out in Luria-Bertani broth. Transconjugant colonies of E. coli were selected after growth on MacConkey agar containing rifampin (300 µg/ml) and ampicillin (50 µg/ml), streptomycin (30 µg/ml), chloramphenicol (30 µg/ml), or tetracycline (30 µg/ml). All resistant isolates were screened for class I integrons by a strict protocol with oligonucleotide primers specific for the sequence of the 5'-CS and 3'-CS regions adjacent to the site-specific recombinational insertion sequence (6). Primer sequences were 5'-CS, GGCATCCAAGCAGCAAG and 3'-CS,A AGCAGACTTGACCTGA (5).
bSource in outbreak.
cNumbers in bold indicate the approximate molecular size of resistance plasmids.

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