RESUMEN
PCR-based assays for detecting enterohemorrhagic Escherichia coli serogroups O26 and O113 were developed by targeting the wzx (O-antigen flippase) and the wzy (O-antigen polymerase) genes found in the O-antigen gene cluster of each organism. The PCR assays were specific for the respective serogroups, as there was no amplification of DNA from non-O26 and non-O113 E. coli serogroups or from other bacterial genera tested. Using the PCR assays, we were able to detect the organisms in seeded apple juice inoculated at concentration levels as low as < or =10 CFU/ml. The O26- and O113-specific PCR assays can potentially be used for typing E. coli O26 and O113 serogroups; these assays will offer an advantage to food and environmental microbiology laboratories in terms of identifying these non-O157 serogroups by replacing antigen-based serotyping.
Asunto(s)
Proteínas Bacterianas , Proteínas Portadoras/genética , Escherichia coli/clasificación , Escherichia coli/genética , Genes Bacterianos , Hexosiltransferasas/genética , Animales , Secuencia de Bases , ADN Bacteriano/genética , Escherichia coli/aislamiento & purificación , Escherichia coli/patogenicidad , Humanos , Proteínas de la Membrana , Familia de Multigenes , Reacción en Cadena de la Polimerasa , SerotipificaciónRESUMEN
The DNA sequence of the 15,155-bp O-antigen gene cluster of Escherichia coli O121 was determined, and 14 open reading frames were identified (all had the same transcriptional direction). Analyses of results indicated that the wzx (O-antigen flippase) and wzy (O-antigen polymerase) genes were E. coli O121 specific, so regions in these two genes were chosen for development of PCR assays. The PCR assays using DNA from 99 E. coli O121 strains, strains representative of non-O121 E. coli serogroups, and strains of other bacterial genera and PCR assays using DNA from seven enrichments of swine fecal samples naturally contaminated with E. coli O121 showed specificity for E. coli O121. Thus, the PCR assay can be employed to reliably identify E. coli O121 and to potentially detect the organism in food, fecal, and environmental samples.
Asunto(s)
Proteínas Bacterianas , Proteínas Portadoras/genética , Escherichia coli/clasificación , Hexosiltransferasas/genética , Familia de Multigenes , Antígenos O/genética , Reacción en Cadena de la Polimerasa/métodos , Animales , Técnicas de Tipificación Bacteriana , Cartilla de ADN , Escherichia coli/genética , Escherichia coli/aislamiento & purificación , Infecciones por Escherichia coli/microbiología , Infecciones por Escherichia coli/veterinaria , Heces/microbiología , Humanos , Proteínas de la Membrana , Análisis de Secuencia de ADN , Serotipificación , Especificidad de la Especie , Porcinos , Enfermedades de los Porcinos/microbiologíaRESUMEN
Autoinducer molecules are utilized by gram-negative and gram-positive bacteria to regulate density-dependent gene expression by a mechanism known as quorum sensing. PCR and DNA sequencing results showed that Campylobacter jejuni and Campylobacter coli possessed luxS, which is responsible for autoinducer-2 (AI-2) production. Using a Vibrio harveyi luminescence assay, the production of AI-2 was observed in milk, chicken broth, and brucella broth by C. coli, C. jejuni, Salmonella enterica serovar Typhimurium, and Escherichia coli O157:H7 under different conditions.