Antimicrobial Resistance, Class 1 Integrons, and Genomic Island 1 in Salmonella Isolates from Vietnam

Abstract

BackgroundThe objective was to investigate the phenotypic and genotypic resistance and the horizontal transfer of resistance determinants from Salmonella isolates from humans and animals in Vietnam.Methodology/Principal FindingsThe susceptibility of 297 epidemiologically unrelated non-typhoid Salmonella isolates was investigated by disk diffusion assay. The isolates were screened for the presence of class 1 integrons and Salmonella genomic island 1 by PCR. The potential for the transfer of resistance determinants was investigated by conjugation experiments. Resistance to gentamicin, kanamycin, chloramphenicol, streptomycin, trimethoprim, ampicillin, nalidixic acid, sulphonamides, and tetracycline was found in 13 to 50% of the isolates. Nine distinct integron types were detected in 28% of the isolates belonging to 11 Salmonella serovars including S. Tallahassee. Gene cassettes identified were aadA1, aadA2, aadA5, bla PSE-1, bla OXA-30, dfrA1, dfrA12, dfrA17, and sat, as well as open reading frames with unknown functions. Most integrons were located on conjugative plasmids, which can transfer their antimicrobial resistance determinants to Escherichia coli or Salmonella Enteritidis, or with Salmonella Genomic Island 1 or its variants. The resistance gene cluster in serovar Emek identified by PCR mapping and nucleotide sequencing contained SGI1-J3 which is integrated in SGI1 at another position than the majority of SGI1. This is the second report on the insertion of SGI1 at this position. High-level resistance to fluoroquinolones was found in 3 multiresistant S. Typhimurium isolates and was associated with mutations in the gyrA gene leading to the amino acid changes Ser83Phe and Asp87Asn.ConclusionsResistance was common among Vietnamese Salmonella isolates from different sources. Legislation to enforce a more prudent use of antibiotics in both human and veterinary medicine should be implemented by the authorities in Vietnam.

Antibiotic Resistance Pattern and Biofilm Formation Ability of Clinically Isolates of Salmonella enterica Serotype typhimurium

“…All isolates showed a relatively high degree of sensitivity to ciprofloxacin (92%) and ceftriaxone (95%), (commonly used fluoroquinolones and cephalosporins antibiotics), which may reflect restricted use of them in avian. This finding is in accordance with those reported from Vietnam (17,18) and is in contrast to report from Turkey (19).…”

No Protective Effects of High-Dosage Dietary Zinc Oxide on Weaned Pigs Infected with Salmonella enterica Serovar Typhimurium DT104

“…Resistance to NAL is caused by a mutation in the gyr gene (36), which, among other genes coding for resistance to antibiotics in S. Typhimurium DT104, is clustered in class 1 integrons on Salmonella genomic island 1 (SGI1) (37). SGI1 was detected in S. Typhimurium DT104 as circular extrachromosomal DNA (38), which can be transferred in the presence of a helper plasmid providing the mating apparatus (39).…”

Molecular Basis of Sulfonamide and Trimethoprim Resistance in Fish-Pathogenic Aeromonas Isolates

“…The combination of dfrA14 and recombined aadA6 cassettes has previously been detected in E. coli of porcine origin (6). The combination dfrA12-orfF-aadA2 has been seen in Salmonella Typhimurium from imported seafood (7), Salmonella enterica serovar Schwarzengrund from chicken (22), and A. hydrophila (15) or E. coli (6) from swine. The combination dfrB1-aadA1-catB2 was seen as part of larger bla VIM-1 -carrying integron structures in Klebsiella pneumoniae (19) and E. coli (20).…”