Changes in Antimicrobial Resistance in Salmonella enterica Serovar Typhimurium.To the Editor: The conclusion by Davis and colleagues (1) that use of antimicrobial agents in agriculture is unlikely to have contributed to the emergence of multidrug-resistant Salmonella serotype serotype /se·ro·type/ (ser´o-tip) the type of a microorganism determined by its constituent antigens; a taxonomic subdivision based thereon. se·ro·type n. See serovar. v. Typhimurium DT104 (MR-DT104) is contrary to available evidence. Use of antimicrobial agents in aquaculture aquaculture, the raising and harvesting of fresh- and saltwater plants and animals. The most economically important form of aquaculture is fish farming, an industry that accounts for an ever increasing share of world fisheries production. in Asia may have contributed to the emergence of DT104. The resistant determinants of MR-DT104 reside on the chromosome, apparently within a transferrable element (2-4). Chloramphenicol chloramphenicol (klōr'ămfĕn`əkŏl'), antibiotic effective against a wide range of gram-negative and gram-positive bacteria (see Gram's stain). It was originally isolated from a species of Streptomyces bacteria. resistance in MR-DT104 is due to floR, a florfenicol resistance gene (5); florfenicol is a veterinary antimicrobial agent that, although not approved in the United States until 1996, has been used in aquaculture in Asia since the early 1980s. FloR was first identified in Photobacterium damsela, a bacterium found in fish (5). Furthermore, tetracycline tetracycline (tĕ'trəsī`klēn), any of a group of antibiotics produced by bacteria of the genus Streptomyces. They are effective against a wide range of Gram positive and Gram negative bacteria, interfering with protein resistance in MR-DT104 is due to et class G resistance gene first identified in Vibrio vibrio Any of a group of aquatic, comma-shaped bacteria in the family Vibrionaceae. Some species cause serious diseases in humans and other animals. They are gram-negative (see anguillarum, a pathogen of fish (4,6). The molecular sequence where the class G and floR determinants reside on the DT104 chromosome is closely related (94% identity) to a plasmid in Pasteurella piscicida, another pathogen of fish (7). These data suggest that the resistance determinants of MR-DT104 may have emerged among bacteria in aquaculture and been horizontally transferred to S. Typhimurium DT104. Spread of MR-DT104 between regions during international travel, as Davis and colleagues suggest, is unlikely because in industrialized in·dus·tri·al·ize v. in·dus·tri·al·ized, in·dus·tri·al·iz·ing, in·dus·tri·al·iz·es v.tr. 1. To develop industry in (a country or society, for example). 2. countries Salmonella is seldom transmitted from person to person (8). Once MR-DT104 emerged, it spread rapidly to many regions through unknown means. The rapid emergence of MR-DT104 suggests a means of spread more efficient than person-to-person transmission. Possibilities include movement of infected breeding or "multiplier" stock or shipment of contaminated feed ingredients; such movements may not be as limited as Davis et al. suggest. For example, the international spread of Salmonella serotype Agona was traced to the global distribution of contaminated fish meal from Peru (9). Once MR-DT104 is introduced into food animals in a region, use of antimicrobial agents in animals would contribute to further dissemination of MR-DT104 (8). If MR-DT104 is present on a farm, the use on the farm of any antimicrobial agent to which MR-DT104 is resistant would contribute to its persistence. An example of such use in cattle in the United States is the tetracycline-containing milk "replacement" commonly fed to dairy calves. This product could kill susceptible gastrointestinal flora while allowing tetracycline-resistant flora such as MR-DT104 to survive and proliferate. Once MR-DT104 proliferates on a farm, dissemination to other farms in the region is facilitated, particularly if the other farms are using an antimicrobial agent to which MR-DT104 is resistant. Increasing antimicrobial resistance in Salmonella contributes to its spread and threatens the use of clinically important antimicrobial agents. To slow the emergence and dissemination of resistant Salmonella, measures should be implemented to ensure that antimicrobial agents are used prudently in food-producing animals food-producing animals see food animals. (10). References (1.) Davis MA, Hancock DD, Besser TE, Rice DH, Gay JM, Gay C, et. al. Changes in antimicrobial resistance among Salmonella enterica serovar Typhimurium isolates from humans and cattle in the Northwestern United States Noun 1. northwestern United States - the northwestern region of the United States Northwest western United States, West - the region of the United States lying to the west of the Mississippi River , 1982-1997. Emerg Infect Dis 1999;5:802-6. (2.) Sandvang D, Aarestrup FM, Jensen LB. Characterisation of integrons and antibiotic resistance genes in Danish multiresistant Salmonella enterica Typhimurium DT104. FEMS Microbiol Let 1998;160:37-41. (3.) Ridley A, Threlfall EJ. Molecular epidemiology of antibiotic resistance genes in multiresistant epidemic Salmonella typhimurium DT104. Microb Drug Resist 1998;4:113-8. (4.) Briggs CE, Fratamico PM. Molecular characterization of an antibiotic resistance gene cluster of Salmonella typhimurium DT104. Antimicrob Agents Chemother 1999;43:846-9. (5.) Bolton LF, Kelly LC, Lee MD, Fedorka-Cray PI, Maurer H. Detection of multidrug-resistant Salmonella enterica serotype typhimurium DT104 based on a gene which confers cross-resistance to florfenicol and chloramphenicol. J Clin Microbiol 1999;37:1348-51. (6.) Zhao J, Aoki T. Nucleotide sequence analysis of the class G tetracycline resistance determinant from Vibrio anguillarum. Microbiol Immunol 1992;36:1051-60. (7.) Kim EH, Aoki T. Drug resistance and broad geographical distribution of identical R plasmids of Pasteurella piscicida isolated from cultured yellowtail in Japan. Microbiol Immunol 1993;37:103-9. (8.) Cohen cohen or kohen (Hebrew: “priest”) Jewish priest descended from Zadok (a descendant of Aaron), priest at the First Temple of Jerusalem. The biblical priesthood was hereditary and male. ML, Tauxe RV. Drug-resistant Salmonella in the United States: an epidemiologic perspective. Science 1986;234:964-9. (9.) Clark GM, Kaufmann AF, Gangrosa EJ. Epidemiology of an international outbreak of Salmonella agona. Lancet 1973;490-3. (10.) Centers for Veterinary Medicine, U.S. Food & Drug Administration. Proposed framework for evaluating and assuring the human safety of the microbial microbial pertaining to or emanating from a microbe. microbial digestion the breakdown of organic material, especially feedstuffs, by microbial organisms. effects of antimicrobial new animal drugs intended for use in food-producing animals. Washington: FDA FDA abbr. Food and Drug Administration FDA, n.pr See Food and Drug Administration. FDA, n.pr the abbreviation for the Food and Drug Administration. ; 1999 Jan 6. Available from: URL URL in full Uniform Resource Locator Address of a resource on the Internet. The resource can be any type of file stored on a server, such as a Web page, a text file, a graphics file, or an application program. :http//www.fda.gov/ cvm/fda/infores/vmac/antim18.htm Frederick J. Angulo and Patricia M. Griffin Centers for Disease Control and Prevention Centers for Disease Control and Prevention (CDC), agency of the U.S. Public Health Service since 1973, with headquarters in Atlanta; it was established in 1946 as the Communicable Disease Center. , Atlanta, Georgia, USA |
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