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Title: DETECTION OF MULTIDRUG-RESISTANT SALMONELLA ENTERICA SEROTYPE TYPHIMURIUM DT104 BASED ON A GENE WHICH CONFERS CROSS-RESISTANCE TO FLORFENICOL AND CHLORAMPHENICOL

Author
item BOLTON, LANCE - USDA
item KELLEY, LYNDA - USDA
item LEE, MARGIE - UGA
item CRAY, PAULA - USDA
item MAURER, JOHN - UGA

Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/1999
Publication Date: N/A
Citation: Bolton, L.F., Kelley, L., Lee, M., Cray, P., Maurer, J.J. 1999. Detection of multidrug-resistant salmonella enterica serotype typhimurium dt104 based on a gene which confers cross-resistance to florfenicol and chloramphenicol. Journal of Clinical Microbiology. Vol. 37. No. 5. P. 1348-1351.

Interpretive Summary: Salmonella typhimurium DT104 first emerged in the UK in the 1980's and is associated with an increase in morbidity and mortality in both humans and animals. It has also been isolated in the US and is now recognized globally. It is characterized by resistance to 5 antimicrobials and has a tendency to acquire additional resistance attributes, especially to the newer drugs which are available to treat both humans and animals. A rapid test to identify DT104 has not been available. We determined that a particular gene (floST), which confers resistance to both Chloramphenicol and Florfenicol, is unique to DT104. Using either resistance to the two antimicrobials or the floST it is possible to identify DT104 nearly 100% of the time the tests are run. Therefore, rapid tests can be developed which will aid in identification of DT104 and minimize the possibility of treatment failure.

Technical Abstract: Salmonella enterica serotype typhimurium (S. Typhimurium) DT104 (DT104) first emerged as a major pathogen in Europe it has been recovered in the US, and is characterized by its pentadrug- resistant pattern. The organism typically carries resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline. The mechanism of chloramphenicol resistance in DT104 was determined by producing antibiotic-resistant Escherichia coli host strain clones from DT104 DNA. DNA from chloramphenicol-resistant clones was sequenced, and probes specific for the genes flo S. typhimurium (flo(ST) int, invA, and spvC were produced for colony blot hybridizations. One hundred nin Salmonella isolates, including 44 multidrug- resistant DT104 isolates, were tested to evaluate the specificities of the probes. The gene flo(SI) reported in this study, confers chloramphenicol and florfenicol resistance on S. typhimurium DT104. Florfenicol resistance is unique to S. typhimurium DT104 and multidrug-resistant S. typhimurium isolates with the same drug resistance profile among all isolates evaluated. Of 44 DT104 isolates tested, 98% were detected based on phenotypic florfenicol resistance and 100% had the flo(ST)-positive genotype. Resistance to florfenicol and chloramphenicol are conferred by the gene flo(St() described in this paper. Presumptive identification of S. typhimurium DT104 can be made rapidly based on the presence of the flo(St) gene or its resulting phenotype.