Detection of Multidrug-Resistant Salmonella enterica Serotype typhimurium DT104 Based on a Gene Which Confers Cross-Resistance to Florfenicol and Chloramphenicol

Abstract

Salmonella enterica serotype typhimurium(S. typhimurium) DT104 (DT104) first emerged as a major pathogen in Europe and is characterized by its pentadrug-resistant pattern. It has also been associated with outbreaks in the United States. 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 floS. typhimurium (floSt ),int, invA, and spvC were produced for colony blot hybridizations. One hundred nine Salmonellaisolates, including 44 multidrug-resistant DT104 isolates, were tested to evaluate the specificities of the probes. The genefloSt , 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 floSt -positive genotype. Resistances to florfenicol and chloramphenicol are conferred by the genefloSt , described in this paper. Presumptive identification of S. typhimurium DT104 can be made rapidly based on the presence of the floSt gene or its resulting phenotype.

Detection of multidrug-resistant Salmonella typhimurium DT104 by multiplex polymerase chain reaction

“…The multiplex PCR of this strain ampli¢ed only the invA and int genes, indicating that the £o st gene was an important target gene for the detection of ACSSuT-type DT104 strains. A complete nucleotide sequence of the £orfenicol resistance gene was determined by Bolton et al [15] as 1202 bp. They also proposed phenotypic and genotypic methods for the iden-ti¢cation of multidrug-resistant S. typhimurium DT104 by the use of a probe to determine chloramphenicol and £orfenicol resistance.…”

“…They also proposed phenotypic and genotypic methods for the iden-ti¢cation of multidrug-resistant S. typhimurium DT104 by the use of a probe to determine chloramphenicol and £orfenicol resistance. When 44 multidrug-resistant DT104 strains were tested, all of them were found resistant to £orfenicol and chloramphenicol [15].…”

“…interacts with the host immune system and is responsible for an increased growth rate in host cells [18]. Bolton et al [15] found that 98% of all the S. typhimurium tested were positive for invA and 88% percent were positive for spvC gene. Our PCR results also indicated that the spvC gene was present in 97% (31 of 32) of S. typhimurium strains.…”

Antimicrobial use in aquaculture re‐examined: its relevance to antimicrobial resistance and to animal and human health

“…A number of antimicrobial resistance genes appear to have been first detected in aquatic bacteria before being detected and disseminating among human and animal pathogens. These include some of the emerging plasmidmediated quinolone resistance (PMQR) genes found in aquatic Vibrio, Shewanella and Aeromonas (Table 2) (Poirel et al, 2005;Cattoir et al, 2007;Xia et al, 2010); new b-lactamase genes from Photobacterium damselae (Table 2) (Morii, 2004) and Oceanobacillus iheyensis (Toth et al, 2010); a novel fosfomycin resistance determinant isolated from the aquatic environment (Xu et al, 2011b); the widely disseminated emerging floR gene of human pathogens (Kim and Aoki, 1996a;Angulo, 1999;Arcangioli et al, 1999;Bolton et al, 1999;Cloeckaert et al, 2000;Miranda and Rojas, 2007;Gordon et al, 2008;Smith, 2008a,b;Cabello, 2009;Welch et al, 2009;Fernández-Alarcón et al, 2010;Hall, 2010); and the chloramphenicol resistance genes catII, catB9 and catB2 from aquatic Photobacterium, Vibrio and Shewanella respectively (Roberts and Schwarz, 2009;Roberts et al, 2012). Moreover, antimicrobial resistance gene variants including those for b-lactams, aminoglycosides, tetracyclines, macrolides and heavy metals have been detected in the genome of the salmon pathogen Renibacteriun salmoninarum and the aquatic opportunistic human pathogen Stenotrophomonas maltophilia suggesting that these aquatic bacteria may be repositories for antimicrobial resistance genes (Crossman et al, 2008;Wiens et al, 2008).…”

Three molecular methods to identify Salmonella enterica serotype Typhimurium DT104: PCR fingerprinting, multiplex PCR and rapid PFGE

“…1B) while non-DT104 isolates had only one amplicon of 521 bp (invA). Recently, other groups have reported similar methods that di¡erentiate the DT104 subtype [4,7,8]. It is of note, however, that the entire antibiotic resistance cluster thought to be indigenous to DT104, including the £o st R, has been detected in Salmonella Agona and possibly Salmonella Typhimurium DT120 [9].…”