RESUMEN
We have identified an IncX1 plasmid named pQJDSal1 from Salmonella enterica subsp. enterica serovar Pullorum (S. Pullorum). The plasmid is 67,685â¯bp in size and has 72 putative genes. pQJDSal1 harbors a conserved IncX1-type backbone with predicted regions for conjugation, replication and partitioning, as well as a toxin/antitoxin plasmid addiction system. Two regions (A and B) that have not been previously reported in IncX1 plasmids are inserted into the backbone. Region A (10.7â¯kb), inserted between parA and taxD, consists of a new Tn6168-like transposon containing an arsenic resistant operon arsB2CHR and sulfonamide resistance gene sul2. Region B contains another arsenic resistant operon arsADHR, resistance gene blaTEM-1B and three transposable elements. Conjugation experiments showed that pQJDSal1 could transfer from S. Pullorum to Escherichia coli (E. coli) J53. Statistical analysis of 70 sequenced IncX1 plasmids revealed that IncX1 plasmids harbored various antibiotic resistance genes. The results highlight the importance of IncX1 plasmids in disseminating antibiotic resistance genes.
Asunto(s)
Arsénico/toxicidad , Farmacorresistencia Bacteriana/genética , Genoma Bacteriano , Plásmidos/química , Salmonella enterica/genética , Mapeo Cromosómico , Conjugación Genética , Replicación del ADN , Elementos Transponibles de ADN , Escherichia coli/genética , Escherichia coli/metabolismo , Operón , Plásmidos/metabolismo , Salmonella enterica/efectos de los fármacos , Salmonella enterica/metabolismo , Sulfonamidas/toxicidadRESUMEN
Salmonella enterica serovar Indiana (S. Indiana) was the most frequently reported foodborne pathogen, which has a broad host range including poultry, swine, and humans. Traditional methods used for the detection of S. Indiana from contaminated food products are time-consuming and labor-intensive. Therefore, rapid detection methods with high sensitivity and specificity are vitally important to prevent the spread of S. Indiana. In this study, we developed a nearly instrument-free, simple molecular method which incorporates cross-priming amplification (CPA) combined with a nucleic acid detection strip (NADS) for sensitive detection of S. Indiana. A set of CPA primers was designed based on S. Indiana specific nucleotide sequences and the specificity of CPA-NADS was tested against 42 bacterial strains. The results showed that this method was highly specific for detection of S. Indiana. The sensitivity of CPA-NADS was evaluated and compared with that of the serovar-specific PCR method and the real-time PCR method. The limit of detection of the CPA method was 8.997â¯fg/µL for genomic DNA and 6.2â¯×â¯101â¯CFU/mL for bacteria in pure culture. An application of the CPA assay was conducted with 90 inoculated specimens by S. Indiana. The accuracy of CPA-NADS was consistent with the results of the traditional culture-based methods in inoculated specimens. This method showed a higher sensitivity than the serovar-specific PCR method did and was more convenient to perform. In conclusion, we demonstrated that the CPA-NADS system offers high specificity, sensitivity, rapidity, and a simple detection tool for screening S. Indiana.
Asunto(s)
ADN Bacteriano/aislamiento & purificación , Análisis de los Alimentos/métodos , Técnicas de Amplificación de Ácido Nucleico/métodos , Salmonella enterica/aislamiento & purificación , Serogrupo , Cartilla de ADN/genética , Contaminación de Alimentos/análisis , Microbiología de Alimentos , Límite de Detección , Tiras Reactivas , Reacción en Cadena en Tiempo Real de la Polimerasa , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
A novel 61,578-bp genomic island named Proteus genomic island 2 (PGI2) was characterized in Proteus mirabilis of swine origin in China. The 23.85-kb backbone of PGI2 is related to those of Salmonella genomic island 1 and Acinetobacter genomic island 1. The multidrug resistance (MDR) region of PGI2 is a complex class 1 integron containing 14 different resistance genes. PGI2 was conjugally mobilized in trans to Escherichia coli in the presence of a conjugative IncC helper plasmid.
Asunto(s)
Islas Genómicas/genética , Proteus mirabilis/efectos de los fármacos , Proteus mirabilis/genética , Animales , ADN Bacteriano/genética , Farmacorresistencia Bacteriana Múltiple/genética , Escherichia coli/efectos de los fármacos , Escherichia coli/genética , Integrones/genética , Salmonella/efectos de los fármacos , Salmonella/genética , PorcinosRESUMEN
A novel 65.8-kb multidrug resistance transposon, designated Tn6450, was characterized in a Proteus mirabilis isolate from chicken in China. Tn6450 contains 18 different antimicrobial resistance genes, including cephalosporinase gene blaDHA-1 and fluoroquinolone resistance genes qnrA1 and aac(6')-Ib-cr It carries a class 1/2 hybrid integron composed of intI2 and a 3' conserved segment of the class 1 integron. Tn6450 is derived from Tn7 via acquisition of new mobile elements and resistance genes.