title: Escherichia coli O-Antigen Gene Clusters of Serogroups O62, O68, O131, O140, O142, and O163: DNA Sequences and Similarity between O62 and O68, and PCR-Based Serogrouping.
abstract: The DNA sequence of the O-antigen gene clusters of Escherichia coli serogroups O62, O68, O131, O140, O142, and O163 was determined, and primers based on the wzx (O-antigen flippase) and/or wzy (O-antigen polymerase) genes within the O-antigen gene clusters were designed and used in PCR assays to identify each serogroup. Specificity was tested with E. coli reference strains, field isolates belonging to the target serogroups, and non-E. coli bacteria. The PCR assays were highly specific for the respective serogroups; however, the PCR assay targeting the O62 wzx gene reacted positively with strains belonging to E. coli O68, which was determined by serotyping. Analysis of the O-antigen gene cluster sequences of serogroups O62 and O68 reference strains showed that they were 94% identical at the nucleotide level, although O62 contained an insertion sequence (IS) element located between the rmlA and rmlC genes within the O-antigen gene cluster. A PCR assay targeting the rmlA and rmlC genes flanking the IS element was used to differentiate O62 and O68 serogroups. The PCR assays developed in this study can be used for the detection and identification of E. coli O62/O68, O131, O140, O142, and O163 strains isolated from different sources.
authors: Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, PA 19038, USA. yanhong.liu@ars.usda.gov.
authors: Yanhong
authors: Y
authors: Liu
authors: Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, PA 19038, USA. xianghe.yan@ars.usda.gov.
authors: Xianghe
authors: X
authors: Yan
authors: Reference Center, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA. rcd3@psu.edu.
authors: Chitrita
authors: C
authors: DebRoy
authors: Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, PA 19038, USA. pina.fratamico@ars.usda.gov.
authors: Pina M
authors: PM
authors: Fratamico
authors: Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, PA 19038, USA. david.needleman@ars.usda.gov.
authors: David S
authors: DS
authors: Needleman
authors: Animal Genomics and Improvement Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705, USA. robert.li@ars.usda.gov.
authors: Robert W
authors: RW
authors: Li
authors: Craig Venter Institute, Rockville, MD 20850, USA. wwang@jcvi.org.
authors: Wei
authors: W
authors: Wang
authors: Craig Venter Institute, Rockville, MD 20850, USA. llosada@jcvi.org.
authors: Liliana
authors: L
authors: Losada
authors: Craig Venter Institute, Rockville, MD 20850, USA. lbrinkac@jcvi.org.
authors: Lauren
authors: L
authors: Brinkac
authors: Craig Venter Institute, Rockville, MD 20850, USA. diana.radune@gmail.com.
authors: Diana
authors: D
authors: Radune
authors: Department of Nutrition & Food Science, University of Maryland, College Park, MD 20742, USA. magaly.toro.i@gmail.com.
authors: Magaly
authors: M
authors: Toro
authors: Reference Center, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802, USA. nvh1@psu.edu.
authors: Narasimha
authors: N
authors: Hegde
authors: Department of Nutrition & Food Science, University of Maryland, College Park, MD 20742, USA. Jmeng@umd.edu.
authors: Jianghong
authors: J
authors: Meng