Class 1 integron-associated gene cassettes in Salmonella enterica subsp. enterica serovar Agona isolated from pig carcasses in Brazil.
OBJECTIVE
Two multiresistant Salmonella enterica subsp. enterica serovar Agona isolates from pig carcasses were investigated for antimicrobial resistance genes and their location with particular reference to the detection of class 1 integrons.


METHODS
The two S. Agona isolates were investigated for their in vitro susceptibility to antimicrobial agents and their plasmid content. The resistance genes and class 1 amplicons were identified by PCR assays. Amplicons of class 1 integrons were cloned and sequenced. Transferability of resistance plasmids was confirmed by conjugation.


RESULTS
Both S. Agona isolates carried conjugative plasmids of approximately 150 kb which harboured all resistance genes detected in the respective isolates. S. Agona 231 was resistant to chloramphenicol by catA1, to tetracycline and minocycline by tet(B), and to sulphonamides by sul1. In addition, it harboured a streptomycin resistance gene strA and a class 1 integron with a new aadA variant designated aadA23, which mediates resistance to streptomycin and spectinomycin. S. Agona 242 also carried the genes catA1, tet(B), and sul1. Moreover, it harboured a second sulphonamide resistance gene, sul2, and a class 1 integron with intact gene cassettes carrying new variants of the trimethoprim resistance gene dfrA15b or the chloramphenicol resistance gene cmlA4. The third gene cassette consisted of a truncated aadA2 gene.


CONCLUSIONS
The results of this study show that large conjugative multiresistance plasmids are present in S. Agona from pigs. Analysis of the class 1 integrons revealed the presence of new variants of resistance genes so far not detected in Salmonella isolates.
Michael
Geovana Brenner
GB
Institut für Tierzucht, Bundesforschungsanstalt für Landwirtschaft (FAL), Höltystr. 10, 31535 Neustadt-Mariensee, Germany.
Cardoso
Marisa
M
Schwarz
Stefan
S
D000003:Abattoirs; D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D001938:Brazil; D003227:Conjugation, Genetic; D024901:Drug Resistance, Multiple, Bacterial; D032023:Integrons / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010957:Plasmids; D012481:Salmonella Infections, Animal / Q000382:microbiology; D019779:Salmonella enterica / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D017422:Sequence Analysis, DNA; D012703:Serotyping; D013552:Swine / Q000382:microbiology*; D013553:Swine Diseases / Q000382:microbiology
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins