Escherichia coli O157:H7 Strains That Persist in Feedlot Cattle Are Genetically Related and Demonstrate an Enhanced Ability To Adhere to Intestinal Epithelial Cells

Center for Meat Safety & Quality, Department of Animal Sciences, Colorado State University, 7C Animal Sciences, Ft. Collins, CO 80523-1171, USA.
Applied and Environmental Microbiology (Impact Factor: 3.67). 08/2009; 75(18):5927-37. DOI: 10.1128/AEM.00972-09
Source: PubMed


A longitudinal study was conducted to investigate the nature of Escherichia coli O157:H7 colonization of feedlot cattle over the final 100 to 110 days of finishing. Rectal fecal grab samples were collected
from an initial sample population of 788 steers every 20 to 22 days and microbiologically analyzed to detect E. coli O157:H7. The identities of presumptive colonies were confirmed using a multiplex PCR assay that screened for gene fragments
unique to E. coli O157:H7 (rfbE and fliCh7) and other key virulence genes (eae, stx1, and stx2). Animals were classified as having persistent shedding (PS), transient shedding (TS), or nonshedding (NS) status if they
consecutively shed the same E. coli O157:H7 genotype (based on the multiplex PCR profile), exhibited variable E. coli O157 shedding, or never shed morphologically typical E. coli O157, respectively. Overall, 1.0% and 1.4% of steers were classified as PS and NS animals, respectively. Characterization
of 132 E. coli O157:H7 isolates from PS and TS animals by pulsed-field gel electrophoresis (PFGE) typing yielded 32 unique PFGE types. One
predominant PFGE type accounted for 53% of all isolates characterized and persisted in cattle throughout the study. Isolates
belonging to this predominant and persistent PFGE type demonstrated an enhanced (P < 0.0001) ability to adhere to Caco-2 human intestinal epithelial cells compared to isolates belonging to less common PFGE
types but exhibited equal virulence expression. Interestingly, the attachment efficacy decreased as the genetic divergence
from the predominant and persistent subtype increased. Our data support the hypothesis that certain E. coli O157:H7 strains persist in feedlot cattle, which may be partially explained by an enhanced ability to colonize the intestinal

Download full-text


Available from: Keith E Belk,
  • Source
    • "A previous report has noted that the number of E. coli O157:H7 shed varies with shedding duration (Davis , 2006), whereby heifers that were culture positive for 23 days or longer had higher fecal counts of E. coli O157:H7 than heifers that were positive for a shorter duration. Previous studies have defined cattle as super-shedders, or alternatively as persistent-shedders, if they shed E. coli O157:H7 for more than 3 consecutive months (Lim et al., 2007; Carlson et al., 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Escherichia coli O157:H7 is a foodborne pathogen that causes illness in humans worldwide. Cattle are the primary reservoir of this bacterium, with the concentration and frequency of E. coli O157:H7 shedding varying greatly among individuals. The term "super-shedder" has been applied to cattle that shed concentrations of E. coli O157:H7≥10(4) colony-forming units/g feces. Super-shedders have been reported to have a substantial impact on the prevalence and transmission of E. coli O157:H7 in the environment. The specific factors responsible for super-shedding are unknown, but are presumably mediated by characteristics of the bacterium, animal host, and environment. Super-shedding is sporadic and inconsistent, suggesting that biofilms of E. coli O157:H7 colonizing the intestinal epithelium in cattle are intermittently released into feces. Phenotypic and genotypic differences have been noted in E. coli O157:H7 recovered from super-shedders as compared to low-shedding cattle, including differences in phage type (PT21/28), carbon utilization, degree of clonal relatedness, tir polymorphisms, and differences in the presence of stx2a and stx2c, as well as antiterminator Q gene alleles. There is also some evidence to support that the native fecal microbiome is distinct between super-shedders and low-shedders and that low-shedders have higher levels of lytic phage within feces. Consequently, conditions within the host may determine whether E. coli O157:H7 can proliferate sufficiently for the host to obtain super-shedding status. Targeting super-shedders for mitigation of E. coli O157:H7 has been proposed as a means of reducing the incidence and spread of this pathogen to the environment. If super-shedders could be easily identified, strategies such as bacteriophage therapy, probiotics, vaccination, or dietary inclusion of plant secondary compounds could be specifically targeted at this subpopulation. Evidence that super-shedder isolates share a commonality with isolates linked to human illness makes it imperative that the etiology of this phenomenon be characterized.
    Foodborne Pathogens and Disease 12/2014; 12(2). DOI:10.1089/fpd.2014.1829 · 1.91 Impact Factor
  • Source
    • "Persistence of E. coli O157 PFGE profiles has been reported in the literature but the majority of this research was conducted as longitudinal studies [13,15,17,18,23] or repeated cross sectional surveys [10] of the same cohorts. Within this research E. coli O157 strains were observed to persist across the two surveys (n = 12, Figure 2) as well as on the same farm (n = 3) after 3-4 years and turnover of cattle. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Escherichia coli (E. coli) O157 is a virulent zoonotic strain of enterohaemorrhagic E. coli. In Scotland (1998-2008) the annual reported rate of human infection is 4.4 per 100,000 population which is consistently higher than other regions of the UK and abroad. Cattle are the primary reservoir. Thus understanding infection dynamics in cattle is paramount to reducing human infections.A large database was created for farms sampled in two repeated cross-sectional surveys carried out in Scotland from 1998 to 2004. A statistical model was generated to identify risk factors for the presence of E. coli O157 on farms. Specific hypotheses were tested regarding the presence of E. coli O157 on local farms and the previous status of farms. Pulsed-field gel electrophoresis (PFGE) profiles were further examined to ascertain whether local spread or persistence of strains could be inferred. The presence of an E. coli O157 positive local farm (average distance: 5.96km) in the Highlands, North East and South West of Scotland, the size of farm and the number of cattle moved onto the farm 8 weeks prior to sampling were significant risk factors for the presence of E. coli O157 on farms. Previous status of a farm was not a significant predictor of current status (p = 0.398). Farms within the same sampling cluster were significantly more likely to be the same PFGE type (p < 0.001), implicating spread of strains between local farms. Isolates with identical PFGE types were also observed to persist across the two surveys, including 3 that were identified on the same farm, suggesting an environmental reservoir. PFGE types that were persistent were more likely to have been observed in human clinical infections in Scotland (p < 0.001) from the same time frame. The results of this study demonstrate the spread of E. coli O157 between local farms and highlight the potential link between persistent cattle strains and human clinical infections in Scotland. This novel insight into the epidemiology of Scottish E. coli O157 paves the way for future research into the exact mechanisms of transmission which should ultimately help with the design of control measures to reduce E. coli O157 from livestock-related sources.
    BMC Veterinary Research 04/2014; 10(1):95. DOI:10.1186/1746-6148-10-95 · 1.78 Impact Factor
  • Source
    • "Table 3), the abundance of isolates from this REPC is likely indicative of the fitness of this E. coli O157:H7 in the gastrointestinal tract or feedlot environment. Accordingly, Carlson et al. [2] determined that persistence and dominance of E. coli O157:H7 strains isolated from feedlot cattle was influenced by genotype and possibly related to the degree of adherence to intestinal epithelial cells "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background Cattle shedding at least 104 CFU Escherichia coli O157:H7/g feces are described as super-shedders and have been shown to increase transmission of E. coli O157:H7 to other cattle in feedlots. This study investigated relationships among fecal isolates from super-shedders (n = 162), perineal hide swab isolates (PS) from super-shedders (n = 137) and fecal isolates from low-shedder (< 104 CFU/g feces) pen-mates (n = 496) using pulsed-field gel electrophoresis (PFGE). A subsample of these fecal isolates (n = 474) was tested for antimicrobial resistance. Isolates of E. coli O157:H7 were obtained from cattle in pens (avg. 181 head) at 2 commercial feedlots in southern Alberta with each steer sampled at entry to the feedlot and prior to slaughter. Results Only 1 steer maintained super-shedder status at both samplings, although approximately 30% of super-shedders in sampling 1 had low-shedder status at sampling 2. A total of 85 restriction endonuclease digestion clusters (REPC; 90% or greater similarity) and 86 unique isolates (< 90% similarity) were detected, with the predominant REPC (30% of isolates) being isolated from cattle in all feedlot pens, although it was not associated with shedding status (super- or low-shedder; P = 0.94). Only 2/21 super-shedders had fecal isolates in the same REPC at both samplings. Fecal and PS isolates from individual super-shedders generally belonged to different REPCs, although fecal isolates of E. coli O157:H7 from super- and low-shedders showed greater similarity (P < 0.001) than those from PS. For 77% of super-shedders, PFGE profiles of super-shedder fecal and PS isolates were distinct from all low-shedder fecal isolates collected in the same pen. A low level of antimicrobial resistance (3.7%) was detected and prevalence of antimicrobial resistance did not differ among super- and low-shedder isolates (P = 0.69), although all super-shedder isolates with antimicrobial resistance (n = 3) were resistant to multiple antimicrobials. Conclusions Super-shedders did not have increased antimicrobial resistance compared to low-shedder pen mates. Our data demonstrated that PFGE profiles of individual super-shedders varied over time and that only 1/162 steers remained a super-shedder at 2 samplings. In these two commercial feedlots, PFGE subtypes of E. coli O157:H7 from fecal isolates of super- and low-shedders were frequently different as were subtypes of fecal and perineal hide isolates from super-shedders.
    BMC Veterinary Research 09/2012; 8(1):178. DOI:10.1186/1746-6148-8-178 · 1.78 Impact Factor
Show more