Objective   To determine resistance to antibiotics and plasmid DNA fingerprint of a total of 186 Salmonella strains isolated from staffs of service trades of food and bever age.

  Methods   Antibiotic resistance testing was performed by the Kirby-Bauer disk diffusion method.Plasmid profiles of the strains were examined using the mehod described by Kado and Liu with some modification.

  Results   1) Of the bacterial isolates tested, 97.3% (181/186)showed drug-resistance.Single-drug resistance to erythomycin(EM)(94.9%)was the most frequent.The rates of single-drug resistance to tetracycline (TC), streptomycin(SM), carbenicillin(CP)and furazolidone(FUZ)accounted for 45.7%, 29.0%, 2615% and 12.9% respectively.The rates of sensitivity to aminopenicillin(AMP), chloramphenicol(CMP), kanamycin(KM), complex sulfamethox azole-trimethoprim(COS), gent amicin(GN), neomycin(NM), tobramycin(TOB), amikacin(AKN)and norflox acin (NOR)were high, between 84.4% and 95.5%.Regarding the durg-resistance patterns, 30.6% of the isolates were resistant to a single durg, while 69.4% were multi drug-resistant.Two-drug resistance to EM/TC and thrid-drug resistance to EM/TC/SM or EM/TC/CP were the second-most frequent and the three-most frequent.2)79 out of 186 Salmonella strains were found to contain at least one plasmid, with the size of the plasmids ranged between 0.21 and 26.72 Mda.1-3 of plasmid were frequently seen.No relationship was found between patterns of drug-resistance and plasmid profiles.

  Conclusion   The drug-resistance of salmonella from carriers are common in Guangzhou.The detection rate of plasmid of the strains is low and no direct co rrelation presents between antibiotic resistance patterns and plasmid profiles.