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Edache DO, Baruch J, Kreikemeier W, Nagaraja TG, Renter DR, Smolensky D, Cernicchiaro N. Investigation of Feedlot-level Use of a Direct-fed Microbial on Fecal Shedding of E. coli O157:H7. J Food Prot 2024; 87:100370. [PMID: 39374786 DOI: 10.1016/j.jfp.2024.100370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2024] [Revised: 09/28/2024] [Accepted: 10/01/2024] [Indexed: 10/09/2024]
Abstract
Our objectives were to determine whether the feedlot-level use of a direct-fed microbial (DFM; Lactobacillus animalis LA51 and Propionibacterium freudenreichii PF24; Bovamine Defend®, 2 × 109 CFU/g) was associated with fecal prevalence and concentration of E. coli O157:H7, and determine pen- and feedlot-level risk factors associated with fecal E. coli O157:H7 prevalence in cattle pens from commercial feedlot operations. Twenty commercial feedlots in Nebraska, ten that included DFM (DFM) and ten that did not (no-DFM), were sampled during the summer of 2017. In each sampling month, 22 pen-floor fecal samples were collected from three pens in each feedlot. Samples were subjected to cultural and molecular procedures for the detection of E. coli O157:H7 (immunomagnetic separation, plating on selective media, followed by PCR confirmation) and spiral plating for quantification. A total of 1,320 samples from 180 pens of finishing cattle belonging to 20 feedlots, which were sampled three times throughout a 12-week period, were processed and tested. Across all feedlots and sampling months, the mean within-pen prevalence was 13.5% (95% CI = 2.6-47.4%). The association between DFM status and the within-pen prevalence of E. coli O157:H7 depended significantly (p < 0.05) on the sampling month. The second sampling month between late July and mid-August corresponded to the highest within-pen prevalence estimates reported in this study, with no-DFM pens having a higher prevalence than DFM pens. After accounting for the DFM status, and based on multivariable analyses, sampling month, average pen body weight, and weather conditions were significantly associated with the within-pen fecal prevalence of E. coli O157:H7. Collectively, these findings demonstrate that the use of a DFM containing Lactobacillus animalis LA51 and Propionibacterium freudenreichii PF26 in feedlots showed potential in reducing fecal E. coli O157:H7 prevalence in cattle during times when prevalence peaks.
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Affiliation(s)
- David O Edache
- Center for Outcomes Research and Epidemiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA; Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
| | - Joaquin Baruch
- Center for Outcomes Research and Epidemiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA; Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
| | | | - Tiruvoor G Nagaraja
- Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
| | - David R Renter
- Center for Outcomes Research and Epidemiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA; Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
| | - Dmitriy Smolensky
- Grain Quality and Structure Research, Center for Grain and Animal Health Research, United States Department of Agriculture, Agricultural Research Service, 1515 College Ave., Manhattan, KS 66502, USA
| | - Natalia Cernicchiaro
- Center for Outcomes Research and Epidemiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA; Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
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Onyeka LO, Adesiyun AA, Keddy KH, Manqele A, Madoroba E, Thompson PN. Prevalence and patterns of fecal shedding of Shiga toxin–producing
Escherichia coli
by cattle at a commercial feedlot in South Africa. J Food Saf 2021. [DOI: 10.1111/jfs.12961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Libby Obumneke Onyeka
- Department of Production Animal Studies, Faculty of Veterinary Science University of Pretoria Onderstepoort South Africa
- Department of Veterinary Public Health and Preventive Medicine College of Veterinary Medicine, Michael Okpara University of Agriculture Umudike Nigeria
| | - Abiodun A. Adesiyun
- Department of Production Animal Studies, Faculty of Veterinary Science University of Pretoria Onderstepoort South Africa
- Department of Basic Veterinary Sciences School of Veterinary Medicine, Faculty of Medical Sciences, University of the West Indies St. Augustine Trinidad and Tobago
| | - Karen H. Keddy
- School of Public Health, Faculty of Health Sciences University of the Witwatersrand Johannesburg South Africa
| | - Ayanda Manqele
- Department of Production Animal Studies, Faculty of Veterinary Science University of Pretoria Onderstepoort South Africa
- Agricultural Research Council—Onderstepoort Veterinary Research Onderstepoort South Africa
| | - Evelyn Madoroba
- Agricultural Research Council—Onderstepoort Veterinary Research Onderstepoort South Africa
- Department of Biochemistry & Microbiology University of Zululand KwaDlangezwa South Africa
| | - Peter Neil Thompson
- Department of Production Animal Studies, Faculty of Veterinary Science University of Pretoria Onderstepoort South Africa
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Vasco K, Nohomovich B, Singh P, Venegas-Vargas C, Mosci RE, Rust S, Bartlett P, Norby B, Grooms D, Zhang L, Manning SD. Characterizing the Cattle Gut Microbiome in Farms with a High and Low Prevalence of Shiga Toxin Producing Escherichia coli. Microorganisms 2021; 9:microorganisms9081737. [PMID: 34442815 PMCID: PMC8399351 DOI: 10.3390/microorganisms9081737] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 08/06/2021] [Accepted: 08/12/2021] [Indexed: 12/20/2022] Open
Abstract
Cattle are the main reservoirs of Shiga toxin producing Escherichia coli (STEC), a major foodborne pathogen associated with acute enteric disease and hemolytic-uremic syndrome in humans. A total of 397 beef and dairy cattle from 5 farms were included in this study, of which 660 samples were collected for 16S rRNA gene sequencing. The microbiota of farms with a high-STEC prevalence (HSP) had greater richness compared to those of farms with a low-STEC prevalence (LSP). Longitudinal analyses showed STEC-shedders from LSP farms had higher microbiome diversity; meanwhile, changes in the microbiome composition in HSP farms were independent of the STEC shedding status. Most of the bacterial genera associated with STEC shedding in dairy farms were also correlated with differences in the percentage of forage in diet and risk factors of STEC carriage such as days in milk, number of lactations, and warm temperatures. Identifying factors that alter the gut microbiota and enable STEC colonization in livestock could lead to novel strategies to prevent fecal shedding and the subsequent transmission to humans.
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Affiliation(s)
- Karla Vasco
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA; (K.V.); (B.N.); (P.S.); (R.E.M.); (L.Z.)
| | - Brian Nohomovich
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA; (K.V.); (B.N.); (P.S.); (R.E.M.); (L.Z.)
| | - Pallavi Singh
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA; (K.V.); (B.N.); (P.S.); (R.E.M.); (L.Z.)
| | - Cristina Venegas-Vargas
- Department of Large Animal Clinical Sciences, College Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA; (C.V.-V.); (P.B.); (B.N.); (D.G.)
| | - Rebekah E. Mosci
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA; (K.V.); (B.N.); (P.S.); (R.E.M.); (L.Z.)
| | - Steven Rust
- Department of Animal Science, Michigan State University, East Lansing, MI 48824, USA;
| | - Paul Bartlett
- Department of Large Animal Clinical Sciences, College Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA; (C.V.-V.); (P.B.); (B.N.); (D.G.)
| | - Bo Norby
- Department of Large Animal Clinical Sciences, College Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA; (C.V.-V.); (P.B.); (B.N.); (D.G.)
| | - Daniel Grooms
- Department of Large Animal Clinical Sciences, College Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA; (C.V.-V.); (P.B.); (B.N.); (D.G.)
| | - Lixin Zhang
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA; (K.V.); (B.N.); (P.S.); (R.E.M.); (L.Z.)
- Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, MI 48824, USA
| | - Shannon D. Manning
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA; (K.V.); (B.N.); (P.S.); (R.E.M.); (L.Z.)
- Correspondence:
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Dewsbury DMA, Cernicchiaro N, Depenbusch B, Nagaraja TG, Renter DG. Effectiveness of a Direct-Fed Microbial Product Containing Lactobacillus acidophilus and Lactobacillus casei in Reducing Fecal Shedding of Escherichia coli O157:H7 in Commercial Feedlot Cattle. Foodborne Pathog Dis 2020; 18:16-23. [PMID: 32898446 DOI: 10.1089/fpd.2020.2828] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The objective of this study was to evaluate the effectiveness of a direct-fed microbial (DFM) product in reducing fecal shedding of Escherichia coli O157:H7 in finishing commercial feedlot cattle in Kansas (KS) and Nebraska (NE). Utilizing a randomized complete block design within the feedlot (KS, n = 1; NE, n = 1), cattle were randomly allocated to 20 pens, grouped in blocks of two based on allocation date, and then, within the block, randomly assigned to a treatment group (DFM or negative control). The DFM product was included in the diet at a targeted daily dose of 1 × 109 colony-forming units (CFU) of the Lactobacillus acidophilus and Lactobacillus casei combination per animal for at least 60 d before sampling. Feedlots were sampled for four consecutive weeks; weekly sampling consisted of collecting 20 pen floor fecal samples per pen. Fecal samples were subjected to culture-based methods for detection and isolation of E. coli O157, and positive samples were quantified using real-time polymerase chain reaction. Primary outcomes of interest were fecal prevalence of E. coli O157:H7 and E. coli O157 supershedding (≥104 CFU/g of feces) prevalence. Data for each feedlot were analyzed at the pen level using mixed models accounting for the study design features. Model-adjusted mean E. coli O157:H7 fecal prevalence estimates (standard error of the mean [SEM]) for DFM and control groups were 8.2% (SEM = 2.2%) and 9.9% (SEM = 2.5%) in KS and 14.6% (SEM = 2.8%) versus 14.3% (SEM = 2.6%) in NE; prevalence did not differ significantly between treatment groups at either site (KS, p = 0.51; NE, p = 0.92). Mean E. coli O157 supershedding prevalence estimates for DFM and control groups were 2.2% (SEM = 0.7%) versus 1.8% (SEM = 0.7%) in KS (p = 0.66) and 6.7% (SEM = 1.5%) versus 3.2% (SEM = 1.0%) in NE (p = 0.04). In conclusion, administering the DFM product in the finishing diet of feedlot cattle did not significantly reduce E. coli O157:H7 fecal prevalence or supershedding prevalence in study pens at either commercial feedlot.
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Affiliation(s)
- Diana M A Dewsbury
- Center for Outcomes Research and Epidemiology, Kansas State University, Manhattan, Kansas, USA.,Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA
| | - Natalia Cernicchiaro
- Center for Outcomes Research and Epidemiology, Kansas State University, Manhattan, Kansas, USA.,Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA
| | | | - T G Nagaraja
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA
| | - David G Renter
- Center for Outcomes Research and Epidemiology, Kansas State University, Manhattan, Kansas, USA.,Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA
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Dixon A, Cernicchiaro N, Amachawadi RG, Shi X, Cull CA, Renter DG. Longitudinal Characterization of Prevalence and Concentration of Shiga Toxin-Producing Escherichia coli Serogroups in Feces of Individual Feedlot Cattle. Foodborne Pathog Dis 2020; 17:631-639. [PMID: 32191498 DOI: 10.1089/fpd.2019.2777] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The objective of this study was to quantify the frequency, distribution, and variability of fecal shedding and super-shedding of Shiga toxin-producing Escherichia coli (STEC) serogroups O26, O45, O103, O111, O121, O145, and O157 in feedlot cattle over time. A total of 750 fecal grab samples were collected over a 5-week period (June-July 2017) from 150 cattle housed in 10 pens at a commercial feedlot operation. Samples were subjected to culture-based methods and real-time quantitative polymerase chain reaction for STEC detection and quantification. Cumulative animal-level prevalence estimates were 9.5%, 5.2%, and 15.8% for STEC O157, non-O157 STEC serogroups only (STEC-6), and for all STEC serogroups tested (STEC-7), respectively, with the prevalence of STEC O157 and STEC-7 significantly differing between weeks (p < 0.01). Most of the variability in fecal shedding for STEC O157, STEC-6, and STEC-7 was between pens, rather than between cattle. Over the 5-week period, 10 animals (6.7%) persistently shed STEC non-O157 over 3 or more consecutive weeks, whereas 2 animals (1.3%) intermittently shed STEC non-O157 on nonconsecutive weeks. Fifteen animals (10.0%) shed multiple STEC serogroups within the same fecal sample and five animals (3.3%) shed multiple serogroups at super-shedding levels, higher than 104 CFU (colony-forming units)/g, in the same sample. The presence of a super-shedder in a pen was significantly associated with a greater within pen-level prevalence of STEC-6 (p = 0.01). This study gives further insights into intermittent and persistent shedding and super-shedding patterns of STEC serogroups in individual feedlot cattle, which can enable the development and effective application of preharvest and periharvest interventions, as well as surveillance strategies, for these pathogens.
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Affiliation(s)
- Andrea Dixon
- Center for Outcomes Research and Epidemiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA.,Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA
| | - Natalia Cernicchiaro
- Center for Outcomes Research and Epidemiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA.,Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA
| | - Raghavendra G Amachawadi
- Center for Outcomes Research and Epidemiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA.,Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA
| | - Xiaorong Shi
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA
| | - Charley A Cull
- Midwest Veterinary Services, Inc., Oakland, Nebraska, USA
| | - David G Renter
- Center for Outcomes Research and Epidemiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA.,Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, USA
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8
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Persad AK, Williams ML, LeJeune JT. Rapid loss of a green fluorescent plasmid in Escherichia coli O157:H7. AIMS Microbiol 2017; 3:872-884. [PMID: 31294194 PMCID: PMC6604956 DOI: 10.3934/microbiol.2017.4.872] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Accepted: 10/11/2017] [Indexed: 11/26/2022] Open
Abstract
Plasmids encoding green fluorescent protein (GFP) are frequently used to label bacteria, allowing the identification and differentiation from background flora during experimental studies. Because of its common use in survival studies of the foodborne pathogen Escherichia coli O157:H7, it is important to know the extent to which the plasmid is retained in this host system. Herein, the stability of a pGFPuv (Clontech Laboratories Inc) plasmid in six Escherichia coli O157:H7 isolates was assessed in an oligotrophic environment (phosphate buffered saline, PBS) without antibiotic selective pressure. The six test isolates were recovered from a variety of animal and human sources (cattle, sheep, starlings, water buffalo, and human feces). GFP labeling of the bacteria was accomplished via transfer electroporation. The stability of the GFP plasmid in the different E. coli O157:H7 isolates was variable: in one strain, GFP plasmid loss was rapid, as early as one day and complete plasmid loss was exhibited by four of the six strains within 19 days. In one of the two isolates retaining the GFP plasmid beyond 19 days, counts of GFP-labeled E. coli O157:H7 were significantly lower than the total cell population (P < 0.001). In contrast, in the other isolate after 19 days, total E. coli O157:H7 counts and GFP-labeled E. coli counts were equivalent. These results demonstrate strain-to-strain variability in plasmid stability. Consequently the use of GFP-labeled E.coli O157:H7 in prolonged survival studies may result in the underestimation of survival time due to plasmid loss.
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Affiliation(s)
- Anil K Persad
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio, USA
| | - Michele L Williams
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio, USA
| | - Jeffrey T LeJeune
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio, USA
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Murphy BP, McCabe E, Murphy M, Buckley JF, Crowley D, Fanning S, Duffy G. Longitudinal Study of Two Irish Dairy Herds: Low Numbers of Shiga Toxin-Producing Escherichia coli O157 and O26 Super-Shedders Identified. Front Microbiol 2016; 7:1850. [PMID: 27917164 PMCID: PMC5114295 DOI: 10.3389/fmicb.2016.01850] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 11/03/2016] [Indexed: 01/24/2023] Open
Abstract
A 12-month longitudinal study was undertaken on two dairy herds to ascertain the Shiga-toxin producing Escherichia coli (STEC) O157 and O26 shedding status of the animals and its impact (if any) on raw milk. Cattle are a recognized reservoir for these organisms with associated public health and environmental implications. Animals shedding E. coli O157 at >10,000 CFU/g of feces have been deemed super-shedders. There is a gap in the knowledge regarding super-shedding of other STEC serogroups. A cohort of 40 lactating cows from herds previously identified as positive for STEC in a national surveillance project were sampled every second month between August, 2013 and July, 2014. Metadata on any potential super-shedders was documented including, e.g., age of the animal, number of lactations and days in lactation, nutritional condition, somatic cell count and content of protein in milk to assess if any were associated with risk factors for super-shedding. Recto-anal mucosal swabs (RAMS), raw milk, milk filters, and water samples were procured for each herd. The swabs were examined for E. coli O157 and O26 using a quantitative real time PCR method. Counts (CFU swab-1) were obtained from a standard calibration curve that related real-time PCR cycle threshold (Ct) values against the initial concentration of O157 or O26 in the samples. Results from Farm A: 305 animals were analyzed; 15 E. coli O157 (5%) were recovered, 13 were denoted STEC encoding either stx1 and/or stx2 virulence genes and 5 (2%) STEC O26 were recovered. One super-shedder was identified shedding STEC O26 (stx1&2). Farm B: 224 animals were analyzed; eight E. coli O157 (3.5%) were recovered (seven were STEC) and 9 (4%) STEC O26 were recovered. Three super-shedders were identified, one was shedding STEC O157 (stx2) and two STEC O26 (stx2). Three encoded the adhering and effacement gene (eae) and one isolate additionally encoded the haemolysin gene (hlyA). All four super-shedders were only super-shedding once during the 1-year sampling period. The results of this study show, low numbers of super-shedders in the herds examined, with high numbers of low and medium shedding. Although four super-shedding animals were identified, no STEC O157 or O26 were recovered from any of the raw milk, milk filter, or water samples. The authors conclude that this study highlights the need for further surveillance to assess the potential for environmental contamination and food chain security.
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Affiliation(s)
- Brenda P. Murphy
- Veterinary Department, Veterinary Food Safety Laboratory, Cork County Council, County CorkIreland
| | | | - Mary Murphy
- Veterinary Department, Veterinary Food Safety Laboratory, Cork County Council, County CorkIreland
| | - James F. Buckley
- Veterinary Department, Veterinary Food Safety Laboratory, Cork County Council, County CorkIreland
| | - Dan Crowley
- Veterinary Department, Veterinary Food Safety Laboratory, Cork County Council, County CorkIreland
| | - Séamus Fanning
- UCD Centre for Food Safety, School of Public Health, Physiotherapy and Sports Science, University College DublinDublin, Ireland
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Spencer SEF, Besser TE, Cobbold RN, French NP. 'Super' or just 'above average'? Supershedders and the transmission of Escherichia coli O157:H7 among feedlot cattle. J R Soc Interface 2016; 12:0446. [PMID: 26269231 DOI: 10.1098/rsif.2015.0446] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Supershedders have been suggested to be major drivers of transmission of Escherichia coli O157:H7 (E. coli O157:H7) among cattle in feedlot environments, despite our relatively limited knowledge of the processes that govern periods of high shedding within an individual animal. In this study, we attempt a data-driven approach, estimating the key characteristics of high shedding behaviour, including effects on transmission to other animals, directly from a study of natural E. coli O157:H7 infection of cattle in a research feedlot, in order to develop an evidence-based definition of supershedding. In contrast to the hypothesized role of supershedders, we found that high shedding individuals only modestly increased the risk of transmission: individuals shedding over 10(3) cfu g(-1) faeces were estimated to pose a risk of transmission only 2.45 times greater than those shedding below that level. The data suggested that shedding above 10(3) cfu g(-1) faeces was the most appropriate definition of supershedding behaviour and under this definition supershedding was surprisingly common, with an estimated prevalence of 31.3% in colonized individuals. We found no evidence that environmental contamination by faeces of shedding cattle contributed to transmission over timescales longer than 3 days and preliminary evidence that higher stocking density increased the risk of transmission.
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Affiliation(s)
| | - Thomas E Besser
- Department Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164, USA
| | - Rowland N Cobbold
- School of Veterinary Science, University of Queensland, Gatton, Queensland, Australia 4343
| | - Nigel P French
- mEpiLab, Infectious Disease Research Centre, Institute of Veterinary Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand
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Luedtke BE, Bosilevac JM, Harhay DM, Arthur TM. Effect of Direct-Fed Microbial Dosage on the Fecal Concentrations of EnterohemorrhagicEscherichia coliin Feedlot Cattle. Foodborne Pathog Dis 2016; 13:190-5. [DOI: 10.1089/fpd.2015.2063] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Affiliation(s)
- Brandon E. Luedtke
- U.S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska
- Department of Biology, University of Nebraska at Kearney, Kearney, Nebraska
| | - Joseph M. Bosilevac
- U.S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska
| | - Dayna M. Harhay
- U.S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska
| | - Terrance M. Arthur
- U.S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska
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12
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Pearl DL. Making the most of clustered data in laboratory animal research using multi-level models. ILAR J 2015; 55:486-92. [PMID: 25541550 DOI: 10.1093/ilar/ilu034] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In the following review article, I address the fitting of multi-level models for the analysis of hierarchical data in laboratory animal medicine. Using an example of paternal dietary effects on the weight of offspring in a mouse model, this review outlines the reasons and benefits of using a multi-level modeling approach. To start, the concept of clustered/autocorrelated data is introduced, and the implications of ignoring the effects of clustered data on measures of association/model coefficients and their statistical significance are discussed. The limitations of other methods compared with multi-level modeling for analyzing clustered data are addressed in terms of statistical power, control of potential confounding effects associated with group membership, proper estimation of associations and their statistical significance, and adjusting for multiple levels of clustering. In addition, the benefits of being able to estimate variance partition coefficients and intra-class correlation coefficients from multi-level models is described, and the concepts of more complex correlation structures and various methods for fitting multi-level models are introduced. The current state of learning materials including textbooks, websites, and software for the nonstatistician is outlined to describe the accessibility of multi-level modeling approaches for laboratory animal researchers.
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Munns KD, Selinger LB, Stanford K, Guan L, Callaway TR, McAllister TA. Perspectives on super-shedding of Escherichia coli O157:H7 by cattle. Foodborne Pathog Dis 2014; 12:89-103. [PMID: 25514549 DOI: 10.1089/fpd.2014.1829] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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 ≥ 10⁴ 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.
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Affiliation(s)
- Krysty D Munns
- 1 Agriculture and Agri-Food Canada, Lethbridge Research Centre , Lethbridge, Alberta, Canada
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Williams K, Ward M, Dhungyel O, Hall E, Van Breda L. A longitudinal study of the prevalence and super-shedding of Escherichia coli O157 in dairy heifers. Vet Microbiol 2014; 173:101-9. [DOI: 10.1016/j.vetmic.2014.07.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 06/28/2014] [Accepted: 07/04/2014] [Indexed: 12/13/2022]
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15
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Risk factors for Escherichia coli O157 shedding and super-shedding by dairy heifers at pasture. Epidemiol Infect 2014; 143:1004-15. [PMID: 24977432 DOI: 10.1017/s0950268814001630] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We undertook a longitudinal study within a cohort of 52 dairy heifers maintained under constant management systems and sampled weekly to investigate a comprehensive range of risk factors which may influence shedding or super-shedding of E. coli O157 (detected by direct faecal culture and immunomagnetic separation). E. coli O157 was detected from 416/933 (44.6%) samples (faeces and recto-anal mucosal swabs) and 32 (3.4%) samples enumerated at >10000 c.f.u./g. Weekly point prevalence ranged from 9.4% to 94.3%. Higher temperature (P < 0.001), rainfall (P = 0.02), relative humidity (P < 0.001), pasture growth (P = 0.013) and body score (P = 0.029) were positively associated with increased shedding. Higher rainfall (P < 0.001), hide contamination (P = 0.002) and increased faecal consistency (P = 0.023) were positively associated with super-shedding. Increased solar exposure had a negative effect on both shedding and super-shedding within bivariate analyses but in the final multivariate model for shedding demonstrated a positive effect (P = 0.017). Results suggest that environmental factors are important in E. coli O157 shedding in cattle.
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16
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Xu Y, Dugat-Bony E, Zaheer R, Selinger L, Barbieri R, Munns K, McAllister TA, Selinger LB. Escherichia coli O157:H7 super-shedder and non-shedder feedlot steers harbour distinct fecal bacterial communities. PLoS One 2014; 9:e98115. [PMID: 24858731 PMCID: PMC4032279 DOI: 10.1371/journal.pone.0098115] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 04/28/2014] [Indexed: 02/01/2023] Open
Abstract
Escherichia coli O157:H7 is a major foodborne human pathogen causing disease worldwide. Cattle are a major reservoir for this pathogen and those that shed E. coli O157:H7 at >104 CFU/g feces have been termed "super-shedders". A rich microbial community inhabits the mammalian intestinal tract, but it is not known if the structure of this community differs between super-shedder cattle and their non-shedding pen mates. We hypothesized that the super-shedder state is a result of an intestinal dysbiosis of the microbial community and that a "normal" microbiota prevents E. coli O157:H7 from reaching super-shedding levels. To address this question, we applied 454 pyrosequencing of bacterial 16S rRNA genes to characterize fecal bacterial communities from 11 super-shedders and 11 contemporary pen mates negative for E. coli O157:H7. The dataset was analyzed by using five independent clustering methods to minimize potential biases and to increase confidence in the results. Our analyses collectively indicated significant variations in microbiome composition between super-shedding and non-shedding cattle. Super-shedders exhibited higher bacterial richness and diversity than non-shedders. Furthermore, seventy-two operational taxonomic units, mostly belonging to Firmicutes and Bacteroidetes phyla, were identified showing differential abundance between these two groups of cattle. The operational taxonomic unit affiliation provides new insight into bacterial populations that are present in feces arising from super-shedders of E. coli O157:H7.
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Affiliation(s)
- Yong Xu
- Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, Canada
| | - Eric Dugat-Bony
- AgroParisTech National Institute for Agricultural Research, Thiverval, Grignon France
| | - Rahat Zaheer
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada
| | - Lorna Selinger
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada
| | - Ruth Barbieri
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada
| | - Krysty Munns
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada
| | - Tim A. McAllister
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada
| | - L. Brent Selinger
- Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, Canada
- * E-mail:
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18
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Wisener LV, Sargeant JM, O'Connor AM, Faires MC, Glass-Kaastra SK. The Use of Direct-Fed Microbials to Reduce Shedding ofEscherichia coliO157 in Beef Cattle: A Systematic Review and Meta-analysis. Zoonoses Public Health 2014; 62:75-89. [DOI: 10.1111/zph.12112] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Indexed: 01/05/2023]
Affiliation(s)
- L. V. Wisener
- Population Medicine; University of Guelph; Guelph ON Canada
| | - J. M. Sargeant
- Population Medicine; University of Guelph; Guelph ON Canada
- Centre for Public Health and Zoonoses; University of Guelph; Guelph ON Canada
| | - A. M. O'Connor
- Department of Veterinary Diagnostic and Production Animal Medicine; College of Veterinary Medicine; Iowa State University; Ames IA USA
| | - M. C. Faires
- Centre for Public Health and Zoonoses; University of Guelph; Guelph ON Canada
| | - S. K. Glass-Kaastra
- Centre for Public Health and Zoonoses; University of Guelph; Guelph ON Canada
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19
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Wisener LV, Sargeant JM, O'Connor AM, Faires MC, Glass-Kaastra SK. The Evidentiary Value of Challenge Trials for Three Pre-harvest Food Safety Topics: A Systematic Assessment. Zoonoses Public Health 2013; 61:449-76. [DOI: 10.1111/zph.12083] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Indexed: 01/07/2023]
Affiliation(s)
- L. V. Wisener
- Centre for Public Health and Zoonoses; University of Guelph; Guelph ON Canada
| | - J. M. Sargeant
- Centre for Public Health and Zoonoses; University of Guelph; Guelph ON Canada
- Population Medicine; University of Guelph; Guelph ON Canada
| | - A. M. O'Connor
- Department of Veterinary Diagnostic and Production Animal Medicine; College of Veterinary Medicine; Iowa State University; Ames IA Canada
| | - M. C. Faires
- Population Medicine; University of Guelph; Guelph ON Canada
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20
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Thomas DE, Elliott EJ. Interventions for preventing diarrhea-associated hemolytic uremic syndrome: systematic review. BMC Public Health 2013; 13:799. [PMID: 24007265 PMCID: PMC3844431 DOI: 10.1186/1471-2458-13-799] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 08/26/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Hemolytic Uremic Syndrome (HUS) may follow infection with Shiga-toxin-producing organisms, principally E. coli O157: H7 (STEC), causing high morbidity and mortality. Our aim was to identify interventions to prevent diarrhea-associated HUS. METHODS Systematic search of the literature for relevant systematic reviews (SRs), randomised controlled trials (RCTs) and public health guidelines. RESULTS Of 1097 animal and 762 human studies, 18 animal studies (2 SRs, 2 reviews, plus 14 RCTs) and 6 human studies (3 SRs, plus 3 RCTs) met inclusion criteria. E. coli O157: H7 Type III secreted protein vaccination decreased fecal E. coli O157 shedding in cattle (P = 0.002). E. coli O157: H7 siderophore receptor and porin proteins (SRP) vaccines reduced fecal shedding in cows (OR 0.42 (95% CI 0.25 to 0.73) and increased anti-E. coli 0157: H7 SRP antibodies in their calves (P < 0.001). Bacterin vaccines had no effect. Probiotic or sodium chlorate additives in feeds reduced fecal E. coli O157 load as did improved farm hygiene (P < 0.05). Solarization of soil reduced E. coli O157: H7 contamination in the soil (P < 0.05). In an RCT examining the role of antibiotic treatment of E. coli O157: H7 diarrhea, HUS rates were similar in children treated with Trimethoprim-sulfamethoxazole and controls (RR 0.57; 95% CI 0.11 to 2.81). In another RCT, HUS rates were similar in children receiving Synsorb-Pk and placebo (RR 0.93; 95% CI 0.39 to 2.22). In one SR, hand washing reduced diarrhea by 39% in institutions (IRR 0.61; 95% CI 0.40 to 0.92) and 32% in community settings (IRR 0.68; 95% CI 0.52 to 0.90) compared to controls. Guidelines contained recommendations to prevent STEC transmission from animals and environments to humans, including appropriate food preparation, personal hygiene, community education, and control of environmental contamination, food and water quality. CONCLUSIONS Animal carriage of STEC is decreased by vaccination and improved farm practices. Treatment of STEC diarrhea with antibiotics and toxin-binders did not prevent HUS. Public health interventions are the key to preventing STEC-associated diarrhea and HUS.
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Affiliation(s)
- Diana E Thomas
- Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, Sydney, Australia
- Centre for Evidence Based Paediatrics Gastroenterology and Nutrition (CEBPGAN), The Sydney Children's Hospitals Network (Westmead), Westmead NSW 2145, Australia
- Kids Research Institute, The Sydney Children's Hospitals Network (Westmead), Westmead NSW 2145, Australia
| | - Elizabeth J Elliott
- Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, Sydney, Australia
- Centre for Evidence Based Paediatrics Gastroenterology and Nutrition (CEBPGAN), The Sydney Children's Hospitals Network (Westmead), Westmead NSW 2145, Australia
- Kids Research Institute, The Sydney Children's Hospitals Network (Westmead), Westmead NSW 2145, Australia
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21
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Williams ML, Pearl DL, Bishop KE, Lejeune JT. Use of multiple-locus variable-number tandem repeat analysis to evaluate Escherichia coli O157 subtype distribution and transmission dynamics following natural exposure on a closed beef feedlot facility. Foodborne Pathog Dis 2013; 10:827-34. [PMID: 23859259 DOI: 10.1089/fpd.2013.1484] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
To better understand the epizootiology of Escherichia coli O157:H7 among cattle, all E. coli O157 isolates recovered on a research feedlot during a single feeding period were characterized by multiple-locus variable-number tandem repeat analysis (MLVA). Three distinct MLVA subtypes (A, B, C), accounting for 24%, 15%, and 64% of total isolates, respectively, were identified. Subtypes A and B were isolated at the initiation of sampling, but their prevalence waned and subtype C, first isolated on the third sampling date, became the predominant subtype on the feedlot. Supershedding events, however, occurred with equal frequency for all three MLVA-types. Using a multilevel logistic regression model, we investigated whether the odds of shedding subtype C relative to subtypes A or B were associated with time, diet, or the presence of a penmate shedding high numbers of subtype C. Only time and exposure to an animal shedding MLVA-type C at 10³ colony-forming units or greater in the pen at the time of sampling were significantly associated with increased shedding of subtype C. High-level shedding of those E. coli O157 subtypes better suited for survival in the environment and/or in the host appear to play a significant role in the development of predominant E. coli O157 subtypes. Supershedding events alone are neither required nor sufficient to drive the epidemiology of specific E. coli O157 subtypes. Additional factors are necessary to direct successful on-farm transmission of E. coli O157.
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Affiliation(s)
- Michele L Williams
- 1 Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Ohio State University , Wooster, Ohio
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22
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Doyle MP, Erickson MC. Opportunities for mitigating pathogen contamination during on-farm food production. Int J Food Microbiol 2012; 152:54-74. [DOI: 10.1016/j.ijfoodmicro.2011.02.037] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 02/03/2011] [Accepted: 02/28/2011] [Indexed: 10/18/2022]
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Abley MJ, Wittum TE, Zerby HN, Funk JA. Quantification of Campylobacter and Salmonella in cattle before, during, and after the slaughter process. Foodborne Pathog Dis 2011; 9:113-9. [PMID: 22044244 DOI: 10.1089/fpd.2011.0931] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Salmonella and Campylobacter cause a significant number of human illnesses globally, most of which are food related. Cattle can be asymptomatic carriers of both of these pathogens. The objective of this study was to determine the association between the concentration of Salmonella and Campylobacter pre- and postharvest in cattle. Samples were collected from each of 98 individually identified cattle during the periharvest and postharvest period. For each animal, four different phases were sampled: on farm (fecal sample), poststunning and exsanguination (hide sponge and rectal content sample [lairage]), prechilling (carcass sponge), and final product (ground meat). Salmonella and Campylobacter were cultured and quantified at each stage by using the direct dilution and most probable number (MPN) method. Salmonella was not isolated from any sample. The proportion (%) of samples that were Campylobacter positive was 77, 82, 97, 55, and 12 for farm, rectal content, hide, carcass, and meat samples respectively. The mean Campylobacter concentration for each sample was as follows: fecal sample from farm, 3.7×10(4) cfu/g; rectal content sample from lairage, 1.6×10(5) cfu/g; hide sponge, 0.9 cfu/cm(2); carcass sponge, 8.7 cfu/half carcass; and meat, 1.1 cfu/g. There were no associations between Campylobacter concentrations for any two sample types. This lack of association could indicate that there is an environmental reservoir that can contaminate the final meat product, or since the majority of animals were positive entering the slaughter process, that the process itself reduces the load of Campylobacter regardless of the initial concentration. In addition, contamination of beef may be more strongly associated with periharvest practices than animal carriage rates.
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Affiliation(s)
- Melanie J Abley
- Department of Veterinary Preventive Medicine, The Ohio State University, Columbus, Ohio, USA
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Dodd CC, Sanderson MW, Jacob ME, Renter DG. Modeling preharvest and harvest interventions for Escherichia coli O157 contamination of beef cattle carcasses. J Food Prot 2011; 74:1422-33. [PMID: 21902910 DOI: 10.4315/0362-028x.jfp-10-516] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Field studies evaluating the effects of multiple concurrent preharvest interventions for Escherichia coli O157 are logistically and economically challenging; however, modeling techniques may provide useful information on these effects while also identifying crucial information gaps that can guide future research. We constructed a risk assessment model with data obtained from a systematic search of scientific literature. Parameter distributions were incorporated into a stochastic Monte Carlo modeling framework to examine the impacts of different combinations of preharvest and harvest interventions for E. coli O157 on the risk of beef carcass contamination. We estimated the risk of E. coli O157 carcass contamination conditional on preharvest fecal prevalence estimates, inclusion of feed additive(s) in the diet, vaccination for E. coli O157, transport and lairage effects, hide intervention(s), and carcass intervention(s). Prevalence parameters for E. coli O157 were assumed to encompass potential effects of concentration; therefore, concentration effects were not specifically evaluated in this study. Sensitivity analyses revealed that fecal prevalence, fecal-to-hide transfer, hide-to-carcass transfer, and carcass intervention efficacy significantly affected the risk of carcass contamination (correlation coefficients of 0.37, 0.56, 0.58, and -0.29, respectively). The results indicated that combinations of preharvest interventions may be particularly important for supplementing harvest interventions during periods of higher variability in fecal shedding prevalence (i.e., summer). Further assessments of the relationships among fecal prevalence and concentration, hide contamination, and subsequent carcass contamination are needed to further define risks and intervention impacts for E. coli O157 contamination of beef.
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Affiliation(s)
- Charles C Dodd
- Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas 66506-5006, USA
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Cernicchiaro N, Pearl DL, McEwen SA, LeJeune JT. Assessment of diagnostic tools for identifying cattle shedding and super-shedding Escherichia coli O157:H7 in a longitudinal study of naturally infected feedlot steers in Ohio. Foodborne Pathog Dis 2010; 8:239-48. [PMID: 21034264 DOI: 10.1089/fpd.2010.0666] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The objectives of this study were to compare the performance of different diagnostic protocols (rectoanal mucosal swabs and immunomagnetic separation [RAMS-IMS], fecal samples and IMS [fecal-IMS], and direct plating) to determine the prevalence of Escherichia coli O157:H7 and to evaluate the pattern of E. coli O157:H7 shedding and super-shedding (defined as having a direct plating count equal to or >10(4) colony forming units of E. coli O157:H7 per gram of feces) in a longitudinal study of naturally infected feedlot steers. RAMS and fecal grab samples were obtained at 14-day intervals from 168 Angus-cross beef steers over a period of 22 weeks. Fecal samples were assessed by direct plating and IMS, whereas RAMS were tested only by enrichment followed by IMS to recover E. coli O157:H7. The period prevalence for shedding was high (62%) among feedlot steers and super-shedding was higher (23%) than anticipated. Although direct plating was the least sensitive method to detect E. coli O157:H7-positive samples, over 20% of high bacterial load samples were not detected by RAMS-IMS and/or fecal-IMS. The sensitivity of RAMS-IMS, fecal-IMS, and direct plating protocols was estimated using simple and multilevel mixed-effects logistic regression models, in which the dependent variable was the dichotomous results of each test and gold standard (i.e., parallel interpretation of the three protocols)-positive individuals were included as an independent variable along with other factors such as dietary supplements, time of sampling, and being exposed to a super-shedding pen-mate. The associations between these factors and the sensitivity of the diagnostic protocols were not statistically significant. In conclusion, differences in the reported impact of diet and probiotics on the shedding of E. coli O157:H7 in previous studies using RAMS-IMS or fecal-IMS were unlikely due to their impact on test performance.
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Affiliation(s)
- Natalia Cernicchiaro
- Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, Canada.
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