Comparison of conventional culture methods and FTA filtration-nested PCR for the detection of Shigella boydii and Shigella sonnei on tomato surfaces

• Published in: Journal of food protection Vol. 68; no. 8; pp. 1606 - 1612
• Main Authors: Warren, B.R, Parish, M.E, Schneider, K.R
• Format: Journal Article
• Language: English
• Published: Des Moines, IA International Association of Milk, Food and Environmental Sanitarians 01.08.2005
• Subjects: bacterial contamination; bacteriology; Biological and medical sciences; CMMEF; Colony Count, Microbial - methods; culture media; Culture Media - chemistry; Enterobacteriaceae; Filtration; Food and Drug Administration Food Code; food contamination; Food Contamination - analysis; Food engineering; Food industries; Food Microbiology; food pathogens; food surfaces; Fundamental and applied biological sciences. Psychology; General aspects; laboratory techniques; Lycopersicon esculentum; Methods of analysis, processing and quality control, regulation, standards; microbial detection; polymerase chain reaction; Polymerase Chain Reaction - methods; public health; sanitation standard operating procedures; Shigella boydii; Shigella boydii - isolation & purification; Shigella sonnei; Shigella sonnei - isolation & purification; Solanum lycopersicum - microbiology; tomatoes; U.S. Food and Drug Administration's Bacteriological Analytical Manual (BAM); Shigella sonnei; Vegetables; Filtration; Tomato; Surface; Polymerase chain reaction; Analysis method; Dicotyledones; Angiospermae; Lycopersicon esculentum; Bacteria; Spermatophyta; Control method; Solanaceae; Shigella boydii; Molecular biology; Detection; Enterobacteriaceae
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X-68.8.1606

Detection of Shigella boydii UI02 and Shigella sonnei UI05 artificially inoculated onto tomatoes was evaluated using enrichment protocols of the U.S. Food and Drug Administration's Bacteriological Analytical Manual (BAM) and the American Public Health Association's Compendium of Methods for the Microbiological Examination of Food (CMMEF), enrichment in Enterobacteriaceae enrichment (EE) broth supplemented with 1.0 microgram/ml novobiocin and incubated at 42 degrees C, and FTA filtration-nested PCR. To assess the effect of natural tomato microflora on recovery, conventional culture enrichments were repeated using rifampin-adapted inocula and enrichment medium supplemented with 50 microgram/ml rifampin. The lowest detection levels for S. boydii UI02 were >5.3 x 10(5) (BAM, CMMEF, and EE broth) and 6.2 CFU per tomato (FTA filtration-nested PCR). For S. sonnei UI05, the lowest detection levels were 1.9 x 10(1) (BAM), 1.5 x 10(3) (CMMEF), 1.1 x 10(1) (EE broth), and 7.4 CFU per tomato (FTA filtration-nested PCR). Natural tomato microflora had a large impact on recovery of S. sonnei UI05 and completely inhibited recovery of S. boydii UI02. EE broth was inhibitory to S. boydii UI02. FTA filtration-nested PCR provided superior detection (P < 0.05) compared with the conventional culture enrichment protocols.