Molecular Characterization of an Antibiotic Resistance Gene Cluster of Salmonella typhimurium DT104

Abstract

Salmonella typhimurium phage type DT104 has become an important emerging pathogen. Isolates of this phage type often possess resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT resistance). The mechanism by which DT104 has accumulated resistance genes is of interest, since these genes interfere with treatment of DT104 infections and might be horizontally transferred to other bacteria, even to unrelated organisms. Previously, several laboratories have shown that the antibiotic resistance genes of DT104 are chromosomally encoded and involve integrons. The antibiotic resistance genes conferring the ACSSuT-resistant phenotype have been cloned and sequenced. These genes are grouped within two district integrons and intervening plasmid-derived sequences. This sequence is potentially useful for detection of multiresistant DT104.

Prevalence, genetic characterization and antimicrobial resistance of Salmonella isolated from fresh pork sausages in Porto Alegre, Brazil

“…On the other hand, chloramphenicol was banned from animal production in Brazil more than a decade ago. The occurrence of resistance against this antimicrobial could possibly be due to the emergence and spread of multi-drug resistant Salmonella isolates that harbour physically linked resistance to this drug, as previously reported (Briggs & Fratamico, 1999). Contrary to the increasing incidence of ciprofloxacin-resistant S. typhimurium reported in other countries (Angulo, Johnson, Tauxe, & Cohen, 2000;Threlfall, Ward, & Rowe, 1997), we did not find resistance to ciprofloxacin.…”

Prevalence and antibiotic resistance of Salmonella serovars in ducks, duck rearing and processing environments in Penang, Malaysia

“…They also found that a 1.0 Kb and 1.2 Kb integrons in S. Agona contained the aadA1 gene which confers resistance to streptomycin. The 13.078 bp of S. Typhimurium isolate contained four genes aadA2, sul1 tetA and bla CARB-2 which encode resistant to streptomycin, sulphonamides, tetraclycline and ampicillin, respectively (Briggs & Fratamico, 1999). Kwon et al (2002) in their work reported that the 1.0, 1.6, and 2.0 Kbp amplicons in S. Gallinarum contained one (addA1a), two (aadB-aadA1b) and three cassettes (dhfrXII-orf-aadA2) respectively, providing resistances against aminoglycosidase (aadA1a, aadA1b, aadB, and aadA2) and trimethoprim (dhfrXII).…”

Antimicrobial resistance of Salmonella isolated from food animals: A review

“…It is currently unknown how or from which organism S. Typhimurium DT104 first acquired the SGI1. However, the floR gene (providing chloramphenicol/florfenicol resistance) is related (53% nucleotide identity) to the chloramphenicol resistance gene (cmlA) known to be located on a conjugative plasmid from Pseudomonas aeruginosa (Briggs & Fratamico, 1999). In addition, the tetracycline resistance region is highly related to genes found in a resistance plasmid from Vibrio anguillarum (Zhao & Aoki, 1992).…”

“…This class of antimicrobial agent has not been used in swine production for more than a decade (Gebreyes et al, 2004). The common occurrence of chloramphenicol resistance can largely be explained by the emergence and spread of MDR S. Typhimurium that harbor physically linked ACSSuT-resistance alleles, the most notable being members of S. Typhimurium DT104 (Briggs & Fratamico, 1999;Gebreyes & Altier, 2002;Threlfall, Ward, & Rowe, 1997).…”

“…SGI1 is a 43-kilobase (kb) genomic island which has 44 open reading frames (ORFs), many with homologies to known genes and some with unknown functions. The antibiotic resistance genes have been localized to a 13-kb segment of the SGI1 termed the MDR region (Boyd et al, 2001;Boyd, Peters, Ng, & Mulvey, 2000;Briggs & Fratamico, 1999). It is currently unknown how or from which organism S. Typhimurium DT104 first acquired the SGI1.…”