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Development of a robust method for isolation of shiga toxin-positive Escherichia coli (STEC) from fecal, plant, soil and water samples from a leafy greens production region in California.

Cooley MB, Jay-Russell M, Atwill ER, Carychao D, Nguyen K, Quiñones B, Patel R, Walker S, Swimley M, Pierre-Jerome E, Gordus AG, Mandrell RE - PLoS ONE (2013)

Bottom Line: Non-O157 STEC were at approximately 5-fold higher incidence compared to O157 STEC: cattle (37.9%), feral swine (21.4%), birds (2.4%), small mammals (3.5%), deer or elk (8.3%), water (14.0%), sediment (12.3%), produce (0.3%) and soil adjacent to produce (0.6%). stx1, stx2 and stx1/stx2 genes were detected in 63%, 74% and 35% of STEC isolates, respectively.The initial method was modified twice during the study revealing evidence of culture bias based on differences in virulence and O-antigen profiles.These results emphasize the importance of multiple approaches for isolation of non-O157 STEC, that livestock and wildlife are common sources of potentially virulent STEC, and evidence of STEC persistence and movement in a leafy greens production environment.

View Article: PubMed Central - PubMed

Affiliation: Produce Safety and Microbiology Research Unit, United States Department of Agriculture-Agricultural Research Service, Albany, California, United States of America. michael.cooley@ars.usda.gov

ABSTRACT
During a 2.5-year survey of 33 farms and ranches in a major leafy greens production region in California, 13,650 produce, soil, livestock, wildlife, and water samples were tested for Shiga toxin (stx)-producing Escherichia coli (STEC). Overall, 357 and 1,912 samples were positive for E. coli O157:H7 (2.6%) or non-O157 STEC (14.0%), respectively. Isolates differentiated by O-typing ELISA and multilocus variable number tandem repeat analysis (MLVA) resulted in 697 O157:H7 and 3,256 non-O157 STEC isolates saved for further analysis. Cattle (7.1%), feral swine (4.7%), sediment (4.4%), and water (3.3%) samples were positive for E. coli O157:H7; 7/32 birds, 2/145 coyotes, 3/88 samples from elk also were positive. Non-O157 STEC were at approximately 5-fold higher incidence compared to O157 STEC: cattle (37.9%), feral swine (21.4%), birds (2.4%), small mammals (3.5%), deer or elk (8.3%), water (14.0%), sediment (12.3%), produce (0.3%) and soil adjacent to produce (0.6%). stx1, stx2 and stx1/stx2 genes were detected in 63%, 74% and 35% of STEC isolates, respectively. Subtilase, intimin and hemolysin genes were present in 28%, 25% and 79% of non-O157 STEC, respectively; 23% were of the "Top 6″ O-types. The initial method was modified twice during the study revealing evidence of culture bias based on differences in virulence and O-antigen profiles. MLVA typing revealed a diverse collection of O157 and non-O157 STEC strains isolated from multiple locations and sources and O157 STEC strains matching outbreak strains. These results emphasize the importance of multiple approaches for isolation of non-O157 STEC, that livestock and wildlife are common sources of potentially virulent STEC, and evidence of STEC persistence and movement in a leafy greens production environment.

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Related in: MedlinePlus

Phylogeny of O157 STEC by 11-loci MLVA.A minimal spanning tree was constructed of 278 MLVA types representing the O157 STEC strains isolated by M3. Node size indicates the relative number of isolates of that type; i.e. the smallest size node represents a single strain of that type. The nodes are color-coded by farm/ranch site code (Panel A) and by sample source (Panel B). Human clinical isolates EDL933 and Sakai are included for comparison only.
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pone-0065716-g008: Phylogeny of O157 STEC by 11-loci MLVA.A minimal spanning tree was constructed of 278 MLVA types representing the O157 STEC strains isolated by M3. Node size indicates the relative number of isolates of that type; i.e. the smallest size node represents a single strain of that type. The nodes are color-coded by farm/ranch site code (Panel A) and by sample source (Panel B). Human clinical isolates EDL933 and Sakai are included for comparison only.

Mentions: One of the goals of this study was to measure point sources of STEC and potential transport processes relevant to produce contamination. Figure 8 illustrates the diversity of O157 STEC strains and the locations and sources associated with the strain MLVA types. The trees in the two panels are identical, but the colored nodes and sectors represent the different farm/ranch codes (Figure 8, Panel A) or sources (Panel B) of the samples yielding O157 STEC. O157 STEC genome strains EDL933 and Sakai have been included as a comparison of MLVA type to the study strains.


Development of a robust method for isolation of shiga toxin-positive Escherichia coli (STEC) from fecal, plant, soil and water samples from a leafy greens production region in California.

Cooley MB, Jay-Russell M, Atwill ER, Carychao D, Nguyen K, Quiñones B, Patel R, Walker S, Swimley M, Pierre-Jerome E, Gordus AG, Mandrell RE - PLoS ONE (2013)

Phylogeny of O157 STEC by 11-loci MLVA.A minimal spanning tree was constructed of 278 MLVA types representing the O157 STEC strains isolated by M3. Node size indicates the relative number of isolates of that type; i.e. the smallest size node represents a single strain of that type. The nodes are color-coded by farm/ranch site code (Panel A) and by sample source (Panel B). Human clinical isolates EDL933 and Sakai are included for comparison only.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3675059&req=5

pone-0065716-g008: Phylogeny of O157 STEC by 11-loci MLVA.A minimal spanning tree was constructed of 278 MLVA types representing the O157 STEC strains isolated by M3. Node size indicates the relative number of isolates of that type; i.e. the smallest size node represents a single strain of that type. The nodes are color-coded by farm/ranch site code (Panel A) and by sample source (Panel B). Human clinical isolates EDL933 and Sakai are included for comparison only.
Mentions: One of the goals of this study was to measure point sources of STEC and potential transport processes relevant to produce contamination. Figure 8 illustrates the diversity of O157 STEC strains and the locations and sources associated with the strain MLVA types. The trees in the two panels are identical, but the colored nodes and sectors represent the different farm/ranch codes (Figure 8, Panel A) or sources (Panel B) of the samples yielding O157 STEC. O157 STEC genome strains EDL933 and Sakai have been included as a comparison of MLVA type to the study strains.

Bottom Line: Non-O157 STEC were at approximately 5-fold higher incidence compared to O157 STEC: cattle (37.9%), feral swine (21.4%), birds (2.4%), small mammals (3.5%), deer or elk (8.3%), water (14.0%), sediment (12.3%), produce (0.3%) and soil adjacent to produce (0.6%). stx1, stx2 and stx1/stx2 genes were detected in 63%, 74% and 35% of STEC isolates, respectively.The initial method was modified twice during the study revealing evidence of culture bias based on differences in virulence and O-antigen profiles.These results emphasize the importance of multiple approaches for isolation of non-O157 STEC, that livestock and wildlife are common sources of potentially virulent STEC, and evidence of STEC persistence and movement in a leafy greens production environment.

View Article: PubMed Central - PubMed

Affiliation: Produce Safety and Microbiology Research Unit, United States Department of Agriculture-Agricultural Research Service, Albany, California, United States of America. michael.cooley@ars.usda.gov

ABSTRACT
During a 2.5-year survey of 33 farms and ranches in a major leafy greens production region in California, 13,650 produce, soil, livestock, wildlife, and water samples were tested for Shiga toxin (stx)-producing Escherichia coli (STEC). Overall, 357 and 1,912 samples were positive for E. coli O157:H7 (2.6%) or non-O157 STEC (14.0%), respectively. Isolates differentiated by O-typing ELISA and multilocus variable number tandem repeat analysis (MLVA) resulted in 697 O157:H7 and 3,256 non-O157 STEC isolates saved for further analysis. Cattle (7.1%), feral swine (4.7%), sediment (4.4%), and water (3.3%) samples were positive for E. coli O157:H7; 7/32 birds, 2/145 coyotes, 3/88 samples from elk also were positive. Non-O157 STEC were at approximately 5-fold higher incidence compared to O157 STEC: cattle (37.9%), feral swine (21.4%), birds (2.4%), small mammals (3.5%), deer or elk (8.3%), water (14.0%), sediment (12.3%), produce (0.3%) and soil adjacent to produce (0.6%). stx1, stx2 and stx1/stx2 genes were detected in 63%, 74% and 35% of STEC isolates, respectively. Subtilase, intimin and hemolysin genes were present in 28%, 25% and 79% of non-O157 STEC, respectively; 23% were of the "Top 6″ O-types. The initial method was modified twice during the study revealing evidence of culture bias based on differences in virulence and O-antigen profiles. MLVA typing revealed a diverse collection of O157 and non-O157 STEC strains isolated from multiple locations and sources and O157 STEC strains matching outbreak strains. These results emphasize the importance of multiple approaches for isolation of non-O157 STEC, that livestock and wildlife are common sources of potentially virulent STEC, and evidence of STEC persistence and movement in a leafy greens production environment.

Show MeSH
Related in: MedlinePlus