Detection and characterization of class 1 integrons in Aeromonas spp. isolated from human diarrheic stool in Mexico.
We determined the presence of class 1 integrons related to the acquisition of resistance to antimicrobials in Aeromonas spp. isolated from individuals with diarrhea. Species were identified as A. caviae, A. hydrophila, A. veronii and A. media using PCR-RFLP of the 16S rDNA. Selected isolates were further characterized by ERIC-PCR. Resistance to chloramphenicol, aztreonam, tetracycline, trimethoprim/sulfamethoxazole, nalidixic acid and streptomycin, among others, was determined using the Kirby-Bauer method. Integrons were detected by PCR amplification of the 5' conserved, variable, and 3' conserved regions. Sequencing of the variable regions revealed class 1 integrons with cassettes encoding resistance to trimethoprim (dfrA12, dfrA15, dfrB4), streptomycin/spectinomycin (aadA2, aadA1), oxacillin (oxa2) and chloramphenicol (catB3, cmlA4). Others had an open reading frame (orfD) or no insert at all. To our knowledge, this is the first description of the occurrence of genes cmlA4 and dfrA15 in Aeromonas class 1 integrons. Not all the integron-linked cassettes conferred their associated resistances, which suggests the inactivity of some cassettes. Most integrons were chromosomally located. The presence of class 1 integrons similar to those found in a wide variety of bacterial genera from different origins, including environmental and fish-borne Aeromonas, confirms the stability and horizontal transfer of these genetic elements.
Pérez-Valdespino
Abigail
A
Department of Biochemistry, Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala S/N, Col. Santo Tomás, CP 11340. Mexico City, Mexico.
Fernández-Rendón
Elizabeth
E
Curiel-Quesada
Everardo
E
D000333:Aeromonas / Q000145:classification / Q000187:drug effects / Q000235:genetics*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015373:Bacterial Typing Techniques; D004269:DNA, Bacterial / Q000235:genetics; D003967:Diarrhea / Q000382:microbiology*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D005243:Feces / Q000382:microbiology*; D005798:Genes, Bacterial; D006801:Humans; D032023:Integrons / Q000235:genetics*; D008800:Mexico; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S