OBJECTIVES: To detect prfA and hly toxin genes of Listeria monocytogenes using polymerase chain reaction (PCR) and colloidal gold technology. METHODS: L. monocytogenes DNA was extracted by boiling method. With prfA and hly of L. monocytogenes as the target genes, the 5' ends of upstream and downstream primers of prfA gene were labeled with 6-FAM and biotin, and the 5' ends of upstream and downstream primers of hly gene were labeled with digoxin and biotin, respectively, to establish the toxin gene detection method. Using cloning transformation, sequencing analysis, cloning of positive control products, the detection kid was developed and its specificity, sensitivity, reproducibility and stability were tested, followed by verification with sample testing. RESULTS: The concentration of L. monocytogenes DNA extracted by boiling method was 148.81±0.97 ng/μL, and the A₂₆₀/A₂₈₀ ratio ranged from 1.8 to 2.0. The PCR products showed a 100% homology with the gene sequences in GenBank database after cloning, transformation and sequencing. The colloidal gold strip yielded positive results only for L. monocytogenes samples without cross-reactions with Staphylococcus aureus, Escherichia coli or Bacillus cereus, and its minimum detection limit was 10^-2 ng/μL, demonstrating a 10-fold greater sensitivity of the test than agarose gel electrophoresis. The test also showed good reproducibility of the results when performed by different operators with good stability of the test strips after storage for 6 to 12 months. The test results showed that this kit could accurately and quickly detect L.monocytogenes in the test samples. CONCLUSIONS The detection kit developed in this study can simultaneously detect prfA and hly toxin genes of L. monocytogenes with good specificity, sensitivity, reproducibility and stability for use in food safety inspection.
Listeria monocytogenes/isolation & purification* ; Gold Colloid ; Bacterial Toxins/genetics* ; Polymerase Chain Reaction/methods* ; Hemolysin Proteins/genetics* ; Bacterial Proteins/genetics* ; DNA, Bacterial/genetics* ; Food Microbiology ; Heat-Shock Proteins

Objective:To establish a method for rapid detection of OXA and par C resistance genes of Acinetobacter baumannii(Ab)by double nucleic acid colloidal gold strip and to develop kit.Methods:DNA of Ab was extracted by heating and boiling method.OXA and par C genes sequences of Ab were selected as target gene fragments based on NCBI.Primers were designed and labeled with 6-FAM,digoxin and biotin,respectively.Drug resistance gene detection reagents were developed,and nucleic acid gold test strips were used for rapid and visual detection.Molecular cloning and sequencing techniques were used to clone positive control samples and evaluate specificity,sensitivity and stability of kit.Results:DNA concentration and purity of Ab extracted by boiling method were good.Homology between cloned and sequenced plasmid DNA and gene sequence in GenBank database was 100%,respectively.Speci-ficity of kit was good,with only Ab showing positive results and other bacterial genera showing negative results;DNA concentration of Ab in double nucleic acid colloidal gold test strip decreased to 10-3 ng/μl,a red line still appeared,whose sensitivity was 10 times higher consistent with minimum detection limit of electrophoresis 10-2 ng/μl;test kits were tested at 3rd,6th and 9th months,and showed good stability.Conclusion:Double resistance detection kit established in this study can simultaneously detect OXA and par C resis-tance of Ab,who has advantages of high sensitivity,strong specificity,rapid and simple,and provides a new method for detection of carbapenem and quinolone antibiotic resistance of Ab.