Abstract
Escherichia coli O157:H7 is known to cause serious diseases including hemorrhagic colitis and hemolytic uremic syndrome. A gold nanoparticle lateral flow immunoassay (Au-LFIA) was used to detect Escherichia coli O157:H7 in ground pork samples. False-positive results were detected using Au-LFIA; a Citrobacter freundii strain was isolated from the ground pork samples and identified by using CHROmagarTM plates, API 20E, and 16S RNA sequencing. Since C. freundii showed cross-reactivity with E. coli O157:H7 when Au-LFIA test strips were used, a novel method combining modified enrichment with a lateral flow immunoassay for accurate and convenient detection of E. coli O157:H7 in ground pork was developed in this study to minimize these false positives. MacConkey broth was optimized for E. coli O157:H7 enrichment and C. freundii inhibition by the addition of 5 mg/L potassium tellurite and 0.10 mg/L cefixime. Using the proposed modified enrichment procedure, the false-positive rate of ground pork samples spiked with 100 CFU/g C. freundii decreased to 5%.
Highlights
Escherichia coli O157:H7 is a dangerous foodborne pathogen because of its low infectious dose and high pathogenicity [1]
The results showed that the five strains of E. coli O157:H7 were detected successfully, and no cross-reaction with the other 40 strains was observed (Table 1)
Ground pork samples spiked with 2 CFU/g E. coli O157:H7 showed 100% positive results and only a 5% false-positive result from C. freundii
Summary
Escherichia coli O157:H7 is a dangerous foodborne pathogen because of its low infectious dose (minimum 10 cells) and high pathogenicity (diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome) [1]. The “gold standard” for detecting E. coli O157:H7 in food samples is a traditional separation-identification method which is time-consuming (at least five days) and laborious (involves pre-enrichment, selective enrichment, culture isolation, and identification). Detection of E. coli O157:H7 in uninoculated ground pork samples using Au-LFIA test strips prepared in our laboratory in combination with the enrichment in modified. The reasons behind the false-positive results obtained when Au-LFIA test strips are used to detect E. coli O157:H7 in ground pork were determined. 2 of 8in modified E.Coli (EC) broth yielded positive results. The reasons behind the false-positive results obtained when Au-LFIA test strips are used to detect E. coli O157:H7 in ground pork were. Of E. coli O157:H7 in ground pork was developed to minimize false positives (Figure 1).
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