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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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Seasonal isolation of O157 and non-O157 STEC from cattle, pig and water samples.The fractions of cattle, feral pig or water samples positive for at least one O157 (A) strain are shown for different months of the year. Each point represents the average fraction of positive enrichments, processed by the IMS method, for each month over a 30-month period from April 2008 until October 2010. Numbers adjacent to each point are the number of samples represented. Monthly rainfall averages are the average of 4 weather sites during the 30 month period (see Methods). Similarly, fractions of cattle, feral pig and water samples positive for a least one non-O157 STEC (B) and monthly rainfall totals are shown for a 10 month period (Jan 2010– Oct 2010) from the same 4 weather sites used in panel A. Letters to the left of the plots indicate significant (P<0.05) correlation between those plots with the same letter designation.
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pone-0065716-g007: Seasonal isolation of O157 and non-O157 STEC from cattle, pig and water samples.The fractions of cattle, feral pig or water samples positive for at least one O157 (A) strain are shown for different months of the year. Each point represents the average fraction of positive enrichments, processed by the IMS method, for each month over a 30-month period from April 2008 until October 2010. Numbers adjacent to each point are the number of samples represented. Monthly rainfall averages are the average of 4 weather sites during the 30 month period (see Methods). Similarly, fractions of cattle, feral pig and water samples positive for a least one non-O157 STEC (B) and monthly rainfall totals are shown for a 10 month period (Jan 2010– Oct 2010) from the same 4 weather sites used in panel A. Letters to the left of the plots indicate significant (P<0.05) correlation between those plots with the same letter designation.

Mentions: During the 2.5 year sampling period, the incidence of O157 in cattle was significantly higher in the summer months of July through October (P = 0.008, Figure 7A). Although O157 in feral pigs was not seasonal significantly, the monthly incidence of O157 in feral pigs correlated with that of O157 in cattle (r = 0.62, P = 0.032), due primarily to the increased incidence in feral pigs during July, August and October. In contrast, non-O157 STEC incidence in cattle and feral pigs failed to show any significant seasonality (Figure 7B). However, non-O157 STEC from feral pigs correlated with the monthly non-O157 STEC from water (r = 0.70, P = 0.033). Additionally, O157 correlated with non-O157 STEC values in water (r = 0.87, P = 0.001) and both were significantly higher during the months of January, February and March (P = 0.028) with higher monthly rainfall totals (r = 0.61, P = 0.033 and r = 0.80, P = 0.005, respectively). O157 and non-O157 STEC in cattle (r = −0.32, P = 0.36) and in feral pigs did not correlate (r = −0.17, P = 0.66). O157 and non-O157 STEC in other wild animal feces was too low, or sampled too intermittently, to yield significant results of seasonal variation (data not shown). Non-O157 STEC incidence in soil and produce samples was too low also (<0.5%) to yield significant seasonal data.


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)

Seasonal isolation of O157 and non-O157 STEC from cattle, pig and water samples.The fractions of cattle, feral pig or water samples positive for at least one O157 (A) strain are shown for different months of the year. Each point represents the average fraction of positive enrichments, processed by the IMS method, for each month over a 30-month period from April 2008 until October 2010. Numbers adjacent to each point are the number of samples represented. Monthly rainfall averages are the average of 4 weather sites during the 30 month period (see Methods). Similarly, fractions of cattle, feral pig and water samples positive for a least one non-O157 STEC (B) and monthly rainfall totals are shown for a 10 month period (Jan 2010– Oct 2010) from the same 4 weather sites used in panel A. Letters to the left of the plots indicate significant (P<0.05) correlation between those plots with the same letter designation.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0065716-g007: Seasonal isolation of O157 and non-O157 STEC from cattle, pig and water samples.The fractions of cattle, feral pig or water samples positive for at least one O157 (A) strain are shown for different months of the year. Each point represents the average fraction of positive enrichments, processed by the IMS method, for each month over a 30-month period from April 2008 until October 2010. Numbers adjacent to each point are the number of samples represented. Monthly rainfall averages are the average of 4 weather sites during the 30 month period (see Methods). Similarly, fractions of cattle, feral pig and water samples positive for a least one non-O157 STEC (B) and monthly rainfall totals are shown for a 10 month period (Jan 2010– Oct 2010) from the same 4 weather sites used in panel A. Letters to the left of the plots indicate significant (P<0.05) correlation between those plots with the same letter designation.
Mentions: During the 2.5 year sampling period, the incidence of O157 in cattle was significantly higher in the summer months of July through October (P = 0.008, Figure 7A). Although O157 in feral pigs was not seasonal significantly, the monthly incidence of O157 in feral pigs correlated with that of O157 in cattle (r = 0.62, P = 0.032), due primarily to the increased incidence in feral pigs during July, August and October. In contrast, non-O157 STEC incidence in cattle and feral pigs failed to show any significant seasonality (Figure 7B). However, non-O157 STEC from feral pigs correlated with the monthly non-O157 STEC from water (r = 0.70, P = 0.033). Additionally, O157 correlated with non-O157 STEC values in water (r = 0.87, P = 0.001) and both were significantly higher during the months of January, February and March (P = 0.028) with higher monthly rainfall totals (r = 0.61, P = 0.033 and r = 0.80, P = 0.005, respectively). O157 and non-O157 STEC in cattle (r = −0.32, P = 0.36) and in feral pigs did not correlate (r = −0.17, P = 0.66). O157 and non-O157 STEC in other wild animal feces was too low, or sampled too intermittently, to yield significant results of seasonal variation (data not shown). Non-O157 STEC incidence in soil and produce samples was too low also (<0.5%) to yield significant seasonal data.

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