Foodborne Illnesses / E. coli /


  1. Buchan, B. W., Faron, M. L., Humphries, R. M., et al.Escherichia, Shigella, and Salmonella” in Manual of Clinical Microbiology, 12th edition, pp. 688-723 (2019). ASM Press, Washington D.C.
  2. Kimberlin, D. W. “Escherichia coli Diarrhea” in Red Book: 2018 Report of the Committee on Infectious Diseases, 31st edition, pp. 338-44 (2018). American Academy of Pediatrics, Itasca, IL.
  3. Scallan E, et al. (2011). Foodborne Illness Acquired in the United States—Major Pathogens. Emerg Infect Dis. 17(1):7-15.
  4. Naimi TS, et al. (2003). Concurrent outbreaks of Shigella sonnei and enterotoxigenic Escherichia coli infections associated with parsley: implications for surveillance and control of foodborne illness. J Food Prot. 66(4):535-41.
  5. Mody, R. K., O’Reilly, C., Griffin, P. M., and Heymann, D. L. “E. coli Diarrheal Diseases” in Control of Communicable Diseases Manual, 20th ed, pp. 158-72 (2015). APHA Press, Washington D.C.
  6. Batz MB, Hoffman S, and Morris Jr. JG. (2012). Ranking the disease burden of 14 pathogens in food sources in the United States using attribution data from outbreak investigations and expert elicitation. J Food Prot. 75(7):1278-91.
  7. Riley LW, et al. (1983). Hemorrhagic colitis associated with a rare Escherichia coli serotype. N Engl J Med. 308(12):681-5.
  8. Griffin PM, Tauxe RV. (1991). The epidemiology of infections caused by Escherichia coli O157:H7, other enterohemorrhagic E. coli, and the associated hemolytic uremic syndrome. Epidemiol Rev. 13:60-98.
  9. Kaper JB, Karmali MA. (2008). The continuing evolution of a bacterial pathogen. PNAS. 105(12):4535-6.
  10. Wick LM, Qi W, Lacher DW, Whittam TS. (2005). Evolution of Genomic Content in the Stepwise Emergence of Escherichia coli O157:H7. J Bacteriol. 187(5):1783-91.
  11. Rangel JM, Sparling PH, Crowe C, Griffin PM, Swerdlow DL. (2005). Epidemiology of Escherichia coli O157:H7 outbreaks, United States, 1982-2002. Emerg Infect Dis. 11(4):603-9.
  12. Bell BP, et al. (1994). A Multistate Outbreak of Escherichia coli O157:H7—Associated Bloody Diarrhea and Hemolytic Uremic Syndrome From Hamburgers: The Washington Experience. JAMA. 272(17):1349-53.
  13. Heiman KE, Mody RK, Johnson SD, Griffin PM, Gould LH. (2015). Escherichia coli O157 Outbreaks in the United States, 2003-2012. Emerg Infect Dis. 21(8):1293-1301.
  14. Sharapov UM, et al. (2016). Multistate Outbreak of Escherichia coli O157:H7 Infections Associated with Consumption of Fresh Spinach: United States, 2006. J Food Prot. 79(12):2024-30.
  15. Bottichio L, et al. (2019). Shiga Toxin-Producing E. coli Infections Associated with Romaine Lettuce – United States, 2018. Clin Infect Dis. doi:10.1093/cid/ciz1182. Online ahead of print.
  16. “Foodborne illness source attribution estimates for 2017 for Salmonella, Escherichia coli O157, Listeria monocytogenes, and Campylobacter using multi-year outbreak surveillance data, United States.” Interagency Food Safety Analytics Collaboration, Sept. 2019. Available at:
  17. Gieraltowski L, et al. (2017). Notes from the Field: Multistate Outbreak of Escherichia coli O157:H7 Infections Linked to Dough Mix — United States, 2016. MMWR. 66(3):88-9.
  18. Daly RF, House J, Stanek D, Stobierski MG. (2017). Compendium of Measures to Prevent Disease Associated with Animals in Public Settings, 2017. JAVMA. 251(11):1268-92.
  19. Snedeker KG, Shaw DJ, Locking ME, Prescott RJ. (2009). Primary and secondary cases in Escherichia coli O157 outbreaks: a statistical analysis. BMC Infect Dis. 9:144.
  20. Seto EYW, Soller JA, and Colford JM. (2007). Strategies to Reduce Person-to-Person Transmission during Widespread Escherichia coli O157:H7 Outbreak. Emerg Infect Dis. 13(6):860-6.
  21. Karpman D, Loos S, Tati R, Arvidsson I. (2017). Haemolytic uraemic syndrome. J Intern Med. 281(2):123-48.
  22. Mody RK, et al. (2015). Postdiarrheal hemolytic uremic syndrome in United States children: clinical spectrum and predictors of in-hospital death. J Pediatr. 166(4):1022-9.
  23. Gould LH, et al. (2011). Postdiarrheal hemolytic uremic syndrome in persons aged 65 and older in FoodNet sites, 2000-2006. J Am Geriatr Soc. 59(2):366-8.
  24. Tarr GAM, et al. (2019). Contribution and Interaction of Shiga Toxin Genes to Escherichia coli O157:H7 Virulence. Toxins (Basel). 11(10):607.
  25. Tarr PI, Gordon CA, Chandler WL. (2005). Shiga-toxin-producing Escherichia coli and haemolytic uraemic syndrome. Lancet. 365(9464):1073-86.
  26. Ko H, Maymani H, Rojas-Hernandez C. (2016). Hemolytic uremic syndrome associated with Escherichia coli O157:H7 infection in older adults: a case report and review of the literature. J Med Case Rep. 10:175.
  27. Jokiranta TS. (2017). HUS and atypical HUS. Blood. 129(21):2847-56.
  28. Manning SD, et al. (2008). Variation in virulence among clades of Escherichia coli O157:H7 associated with disease outbreaks. PNAS. 105(12):4868-73.
  29. Orth D, et al. (2007). The Shiga toxin genotype rather than the amount of Shiga toxin or the cytotoxicity of Shiga toxin in vitro correlates with the appearance of the hemolytic uremic syndrome. Diagn Microbiol Infect Dis. 59(3):235-42.
  30. Huang JY, et al. (2016). Infection with Pathogens Transmitted Commonly Through Food and the Effect of Increasing Use of Culture-Independent Diagnostic Tests on Surveillance — Foodborne Diseases Active Surveillance Network, 10 U.S. sites, 2012–2015. MMWR. 65(14):368-71.
  31. Gould LH, et al. (2009). Hemolytic uremic syndrome and death in persons with Escherichia coli O157:H7 infection, foodborne diseases active surveillance network sites, 2000-2006. Clin Infect Dis. 49(10):1480-5.
  32. Kravitz GR, Smith K, Wagstrom L. (2002). Colonic necrosis and perforation secondary to Escherichia coli O157:H7 gastroenteritis in an adult patient without hemolytic uremic syndrome. Clin Infect Dis. 35(9):e103-5.
  33. Barton Behravesh C, et al. (2011). Deaths associated with bacterial pathogens transmitted commonly through food: foodborne diseases active surveillance network (FoodNet), 1996-2005. J Infect Dis. 204(2):263-7.
  34. Gould LH, et al. (2011). Postdiarrheal hemolytic uremic syndrome in persons aged 65 and older in FoodNet sites, 2000-2006. J Am Geriatr Soc. 59(2):366-8.
  35. Mody RK, et al. (2012). Infections in pediatric postdiarrheal hemolytic uremic syndrome: factors associated with identifying shiga toxin-producing Escherichia coli. Arch Pediatr Adolesc Med. 166(10):902-9.
  36. Garg AX, et al. (2003). Long-term renal prognosis of diarrhea-associated hemolytic uremic syndrome: a systematic review, meta-analysis, and meta-regression. JAMA. 290(10):1360-70.
  37. Batz MB, Henke E, Kowalcyk B. (2013). Long-term consequences of foodborne infections. Infect Dis Clin North Am. 27(3):599-616.
  38. Karmali MA, Steele BT, Petric M, Lim C. (1983). Sporadic cases of haemolytic-uraemic syndrome associated with faecal cytotoxin and cytotoxin-producing Escherichia coli in stools. Lancet. 1(8325):619-20.
  39. Medus C, et al. (2016). Long-Term Sentinel Surveillance for Enterotoxigenic Escherichia coli and Non-O157 Shiga Toxin-Producing E. coli in Minnesota. Open Forum Infect Dis. 3(1):ofw003.
  40. Gould LH, et al. (2013). Increased recognition of non-O157 Shiga toxin-producing Escherichia coli infections in the United States during 2000-2010: epidemiologic features and comparisons with E. coli O157 infections. Foodborne Pathog Dis. 10(5):453-60.
  41. Luna-Gierke RE, et al. (2014). Outbreaks of non-O157 Shiga toxin-producing Escherichia coli infection: USA. Epidemiol Infect. 142(11):2270-80.
  42. Buchholz U, et al. (2011). German Outbreak of Escherichia coli O104:H4 Associated with Sprouts. N Engl J Med. 365:1763-70.
  43. Karmali MA. Emerging Public Health Challenges of Shiga Toxin-Producing Escherichia coli Related to Changes in the Pathogen, the Population, and the Environment. Clin Infect Dis. 64(3):371-6.
  44. Smith JL, Fratamico PM, Gunther 4th NW. (2014). Shiga toxin-producing Escherichia coli. Adv Appl Microbiol. 86:145-97.
  45. Hussein HS. (2007). Prevalence and pathogenicity of Shiga toxin-producing Escherichia coli in beef cattle and their products. J Anim Sci. 85(13 Suppl):E63-72.
  46. Ferens WA, Hovde CJ. (2011). Escherichia coli O157:H7: Animal Reservoir and Sources of Human Infection. Foodborne Pathog Dis. 8(4):465-87.
  47. Cernicchiaro N, et al. (2013). Prevalence of Shiga Toxin-Producing Escherichia coli and Associated Virulence Genes in Feces of Commercial Feedlot Cattle. Foodborne Pathog Dis. 10(10):835-41.
  48. Cull CA, et al. (2017). Feedlot- and Pen-Level Prevalence of Enterohemorrhagic Escherichia coli in Feces of Commercial Feedlot Cattle in Two Major U.S. Cattle Feeding Areas. Foodborne Pathog Dis. 14(6):309-17.
  49. Dewsbury DM, et al. (2015). Summer and Winter Prevalence of Shiga Toxin-Producing Escherichia coli (STEC) O26, O45, O103, O111, O121, O145, and O157 in Feces of Feedlot Cattle. Foodborne Pathog Dis. 12(8):726-32.
  50. Renter DG, et al. (2005). Prevalence, risk factors, O serogroups, and virulence profiles of Shiga toxin-producing bacteria from cattle production environments. J Food Prot. 68(8):1556-5.
  51. Keen JE, Wittum TE, Dunn JR, Bono JL, Durso LM. (2006). Shiga-toxigenic Escherichia coli O157 in Agricultural Fair Livestock, United States. Emerg Infect Dis. 12(5):780-6.
  52. Olsen SJ, et al. (2002). A Waterborne Outbreak of Escherichia coli O157:H7 Infections and Hemolytic Uremic Syndrome: Implications for Rural Water Systems. Emerg Infect Dis. 8(4):370-5.
  53. “Public Health Dispatch: Outbreak of Escherichia coli O157:H7 and Campylobacter Among Attendees of the Washington County Fair -- New York, 1999.” Centers for Disease Control and Prevention, 17 Sept. 1999. Available at:
  54. Craun GF, et al. (2010). Causes of outbreaks associated with drinking water in the United States from 1971 to 2006. Clin Microbiol Rev. 23(3):507-28.
  55. Friedman MS, et al. (1999). Escherichia coli O157:H7 outbreak associated with an improperly chlorinated swimming pool. Clin Infect Dis. 29(2):298-303.
  56. Hlavsa MC, et al. (2018). Outbreaks Associated with Treated Recreational Water — United States, 2000-2014. MMWR. 67(19):547–51.
  57. Voetsch AC, et al. (2007). Risk factors for sporadic Shiga toxin-producing Escherichia coli O157 infections in FoodNet sites, 1999-2000. Epidemiol Infect. 135(6):993–1000.
  58. Kassenborg HD, et al. (2004). Farm visits and undercooked hamburgers as major risk factors for sporadic Escherichia coli O157:H7 infection: Data from a case-control study in 5 FoodNet sites. Clin Infect Dis. 38(Suppl 3):S271-8.
  59. Hale CR, et al. (2012). Estimates of enteric illness attributable to contact with animals and their environments in the United States. Clin Infect Dis. 54(Suppl 5):S472-9.
  60. Klumb CA, Scheftel JM, Smith KE. (2020). Animal agriculture exposures among Minnesota residents with zoonotic enteric infections, 2012-2016. Epidemiol Infect. 148:e55.
  61. Swaminathan B, Barrett TJ, Hunter SB, Tauxe RV. (2001). PulseNet: the molecular subtyping network for foodborne bacterial disease surveillance, United States. Emerg Infect Dis. 7(3):382–9.
  62. Tauxe RV. (2006). Molecular subtyping and the transformation of public health. Foodborne Pathog Dis. 3(1):4-8.
  63. Nguyen VD, et al. (2015). Increase in Multistate Foodborne Disease Outbreaks—United States, 1973-2010. Foodborne Pathog Dis. 12(11):867-72.
  64. Crowe SJ, Mahon BE, Vieira AR, Gould LH. (2015). Vital Signs: Multistate Foodborne Outbreaks—United States, 2010-2014. MMWR. 64(43):1221-5.
  65. Scharff RL, et al. (2016). An Economic Evaluation of PulseNet: A Network for Foodborne Disease Surveillance. Am J Prev Med. 50(5 Suppl 1):S66-S73.
  66. Besser JM, et al. (2019). Interpretation of Whole-Genome Sequencing for Enteric Disease Surveillance and Outbreak Investigation. Foodborne Pathog Dis. 16(7):504-12.
  67. Ribot EM, Freeman M, Hise KB, Gerner-Smidt P. (2019). PulseNet: Entering the Age of Next-Generation Sequencing. Foodborne Pathog Dis. 16(7):451-6.
  68. Gould LH, Mungai E, Barton Behravesh C. (2014). Outbreaks attributed to cheese: differences between outbreaks caused by unpasteurized and pasteurized dairy products, United States, 1998-2011. Foodborne Pathog Dis. 11(7):545-51.
  69. Koohmaraie M, et al. (2007). Interventions to reduce/eliminate Escherichia coli O157:H7 in ground beef. Meat Sci. 77(1):90-6.
  70. Oliver SP, Boor KJ, Murphy SC, Murinda SE. (2009). Food safety hazards associated with consumption of raw milk. Foodborne Pathog Dis. 6(7):793-806.
  71. Dechet AM, et al. (2014). Outbreaks caused by sprouts, United States, 1998-2010: lessons learned and solutions needed. Foodborne Pathog Dis. 11(8):635-44.
  72. Laidler MR, et al. (2013). Escherichia coli O157:H7 infections associated with consumption of locally grown strawberries contaminated by deer. Clin Infect Dis. 57(8):1129-34.
  73. Neil KP, et al. (2012). A novel vehicle for transmission of Escherichia coli O157:H7 to humans: multistate outbreak of E. coli O157:H7 infections associated with consumption of ready-to-bake commercial prepackaged cookie dough--United States, 2009. Clin Infect Dis. 54(4):511-8.
  74. Cody SH, et al. (1999). An Outbreak of Escherichia coli O157:H7 Infection from Unpasteurized Commercial Apple Juice. Ann Intern Med. 130(3):203-9.
  75. Hilborn ED, et al. (2000). An outbreak of Escherichia coli O157:H7 infections and haemolytic uremic syndrome associated with consumption of unpasteurized apple cider. Epidemiol Infect. 124(1):31-6.
  76. Miller BD, et al. (2012). Use of traceback methods to confirm the source of a multistate Escherichia coli O157:H7 outbreak due to in-shell hazelnuts. J Food Prot. 75(2):320-7.
  77. Stromberg ZR, Redweik GAJ, Mellata M. (2018). Detection, Prevalence, and Pathogenicity of Non-O157 Shiga Toxin-Producing Escherichia coli from Cattle Hides and Carcasses. Foodborne Pathog Dis. 15(3):119-31.
  78. Noll LW, et al. (2018). Detection and Quantification of Seven Major Serogroups of Shiga Toxin-Producing Escherichia coli on Hides of Cull Dairy, Cull Beef, and Fed Beef Cattle at Slaughter. J Food Prot. 81(8):1236-44.
  79. Barkocy-Gallagher GA, et al. (2003). Seasonal prevalence of Shiga toxin-producing Escherichia coli, including O157:H7 and non-O157 serotypes, and Salmonella in commercial beef processing plants. J Food Prot. 66(11):1978-86.
  80. Ekong PS, Sanderson MW, Cernicchiaro N. (2015). Prevalence and concentration of Escherichia coli O157 in different seasons and cattle types processed in North America: A systematic review and meta-analysis of published research. Prev Vet Med. 121(1-2)74-85.
  81. “Sampling results for E. coli O157:H7, non-O157 STEC, and Salmonella in beef products in beef processing plants, 2018-2020.” United States Department of Agriculture Food Safety and Inspection Service. Available at:
  82. Laine ES, et al. (2005). Outbreak of Escherichia coli O157:H7 infections associated with nonintact blade-tenderized frozen steaks sold by door-to-door vendors. J Food Prot. 68(6):1198-202.
  83. Varma JK, et al. (2003). An outbreak of Escherichia coli O157 infection following exposure to a contaminated building. JAMA. 290(20):2709-12.
  84. Lanier WA, et al. (2011). Outbreak of Shiga-toxigenic Escherichia coli O157:H7 infections associated with rodeo attendance, Utah and Idaho, 2009. Foodborne Pathog Dis. 8(10):1131-3.
  85. Mukherjee A, et al. (2006). Soil survival of Escherichia coli O157:H7 acquired by a child from garden soil recently fertilized with cattle manure. J Appl Microbiol. 101(2):429-36.
  86. Freedman SB, et al. (2016). Shiga Toxin-Producing Escherichia coli Infection, Antibiotics, and Risk of Developing Hemolytic Uremic Syndrome: A Meta-analysis. Clin Infect Dis. 62(10):1251-8.
  87. Tarr GAM, et al. (2019). Performance of commercial tests for molecular detection of Shiga toxin-producing Escherichia coli (STEC): a systematic review and meta-analysis protocol. BMJ Open. 9(2):e025950.
  88. Cybulski Jr. RJ, et al. (2018). Clinical Impact of a Multiplex Gastrointestinal Polymerase Chain Reaction Panel in Patients With Acute Gastroenteritis. Clin Infect Dis. 67(11):1688-96.
  89. Gould LH, et al. (2009). Recommendations for Diagnosis of Shiga Toxin--Producing Escherichia coli Infections by Clinical Laboratories. MMWR. 58(RR-12):1-14.
  90. Shane AL, et al. (2017). 2017 Infectious Diseases Society of America Clinical Practice Guidelines for the Diagnosis and Management of Infectious Diarrhea. Clin Infect Dis. 65(12):e45-e80.
  91. Keene WE, et al. (1994). A Swimming-Associated Outbreak of Hemorrhagic Colitis Caused by Escherichia coli O157:H7 and Shigella Sonnei. N Engl J Med. 331:579-84.
  92. Johannes L, Römer W. (2009). Shiga toxins--from cell biology to biomedical applications. Nat Rev Microbiol. 8(2):105-16.
  93. Boyce TG, Swerdlow DL, Griffin PM. (1995). Escherichia coli O157:H7 and the hemolytic-uremic syndrome. N Engl J Med. 333(6):364-8.
  94. Breuer T, et al. (2001). A multistate outbreak of Escherichia coli O157:H7 infections linked to alfalfa sprouts grown from contaminated seeds. Emerg Infect Dis. 7(6):977-82.
  95. McCarthy TA, et al. (2001). Hemolytic-Uremic Syndrome and Escherichia coli O121 at a Lake in Connecticut, 1999. Pediatrics. 108(4):E59.
  96. Brooks JT, et al. (2005). Non-O157 Shiga toxin-producing Escherichia coli infections in the United States, 1983-2002. J Infect Dis. 192(8):1422-9.
  97. Johnson KE, Thorpe CM, Sears CL. (2006). The emerging clinical importance of non-O157 Shiga toxin-producing Escherichia coli. Clin Infect Dis. 43(12):1587-95.
  98. Hussein HS, Sakuma T. (2005). Prevalence of shiga toxin-producing Escherichia coli in dairy cattle and their products. J Dairy Sci. 88(2):450-65.
  99. Lynch MF, Tauxe RV, Hedberg CW. (2009). The growing burden of foodborne outbreaks due to contaminated fresh produce: risks and opportunities. Epidemiol Infect. 137(3):307-15.
  100. Bennett SD, et al. (2018). Produce-associated foodborne disease outbreaks, USA, 1998-2013. Epidemiol Infect. 146(11):1397-406.
  101. Carstens CK, Salazar JK, Darkoh C. (2019). Multistate Outbreaks of Foodborne Illness in the United States Associated With Fresh Produce From 2010 to 2017. Front Microbiol. 10:2667.
  102. Kallianpur AR, et al. (2018). Genetic Susceptibility to Postdiarrheal Hemolytic-Uremic Syndrome After Shiga Toxin-Producing Escherichia coli Infection: A Centers for Disease Control and Prevention FoodNet Study. J Infect Dis. 217:1000-10.
  103. Tack DM, et al. (2020). Preliminary Incidence and Trends of Infections with Pathogens Transmitted Commonly Through Food — Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 2016–2019. MMWR. 69(17):509-14.
  104. Robinson TJ, Scheftel JM, Smith KE. (2014). Raw Milk Consumption among Patients with Non-Outbreak-related Enteric Infections, Minnesota, USA, 2001-2010. Emerg Infect Dis. 20(1):38-44.
  105. Dewey-Mattia D, Manikonda K, Hall AJ, Wise ME, Crowe SJ. (2018). Surveillance for Foodborne Disease Outbreaks—United States, 2009-2015. MMWR. 67(10):1-11.
  106. Crump JA, et al. (2002). An outbreak of Escherichia coli O157:H7 infections among visitors to a dairy farm. N Engl J Med. 347(8):555-60.
  107. .Goode B, et al. (2009). Outbreak of escherichia coli O157:H7 infections after Petting Zoo visits, North Carolina State Fair, October-November 2004. Arch Pediatr Adoles Med. 163(1):42-8.
  108. Smith KE, et al. (2004). Outbreaks of enteric infections caused by multiple pathogens associated with calves at a farm day camp. Pediatr Infect Dis J. 23(12):1098-104.
  109. Crump JA, et al. (2003). Outbreaks of Escherichia coli O157 infections at multiple county agricultural fairs: a hazard of mixing cattle, concession stands and children. Epidemiol Infect. 131(3):1055-62.
  110. Ferguson DD, et al. (2005). Temporally distinct Escherichia coli O157 outbreaks associated with alfalfa sprouts linked to a common seed source - Colorado and Minnesota, 2003. Epidemiol Infect. 133(3):439-47.
  111. Beczkiewicz A, et al. (2019). High Relative Frequency of Enteroaggregative Escherichia coli Among Patients With Reportable Enteric Pathogens, Minnesota, 2016-2017. Clin Infect Dis. 69(3):473-79.
  112. Bradley KK, et al. (2012). Epidemiology of a large restaurant-associated outbreak of Shiga toxin-producing Escherichia coli O111:NM. Epidemiol Infect. 140(9):1644-54.
  113. “Etymologia: Escherichia coli.” National Center for Biotechnology Information, Aug. 2015. Available at:
  114. Andrade A, Girón JA, Amhaz JM, Trabulsi LR, Martinez MB. (2002). Expression and characterization of flagella in nonmotile enteroinvasive Escherichia coli isolated from diarrhea cases. Infect Immun. 70(10):5882-6.
  115. Gomes TAT, et al. (2016). Diarrheagenic Escherichia coli. Braz J Microbiol. 47(Suppl 1):3-30.
  116. “Chapter 4: Travel-Related Infectious Diseases – Escherichia coli, Diarrheagenic.” Centers for Disease Control and Prevention, 1 Jul. 2019. Available at:
  117. Joseph A, Cointe A, Mariani Kurkdjian P, Rafat C, Hertig A. (2020). Shiga Toxin-Associated Hemolytic Uremic Syndrome: A Narrative Review. Toxins (Basel). 12(2):67.
  118. “Enterohemorrhagic Escherichia Coli (EHEC).” National Center for Biotechnology Information, 29 Jun. 2020. Available at:
  119. “etymologia: Shigella [shĭ-gel′ə].” National Center for Biotechnology Information, Mar. 2009. Available at:
  120. Rahman M, Nabi A, Asadulghani M, Faruque SM, Islam MA. (2018). Toxigenic properties and stx phage characterization of Escherichia coli O157 isolated from animal sources in a developing country setting. BMC Microbiol. 18:98.