Journal of Consumer Protection and Food Safety

, Volume 13, Issue 3, pp 279–287 | Cite as

Prevalence of Enterobacteriaceae on fresh produce and food safety practices in small-acreage farms in Tennessee, USA

  • Agnes Kilonzo-NthengeEmail author
  • Siqin Liu
  • Fawzy Hashem
  • Patricia Millner
  • Susan Githua
Research Article


In spite of the health benefits acquired from produce, microbial safety continues to be a major concern. This study evaluated microbial quality of produce and food safety practices in small-scale farms. Microbial quality of produce from farms was determined by standard and biochemical techniques. Antimicrobial-susceptibility of bacteria was determined by Kirby-Bauer’s disc diffusion method. In addition, questionnaires were developed and distributed to in Middle Tennessee, US growers to capture growers’ practices on the farm. Aerobic plate counts in leafy produce and herbs (5.2–6.1 log CFU/g) were significantly higher (p < 0.05) than that of fruits (3.2–4.0 log CFU/g). Total coliforms in carrots (3.6 CFU/g) were also significantly higher (p < 0.05) than in lettuce (2.9/CFU/g), strawberries (2.5 CFU/g), and apples (2.1 CFU/g). Our results demonstrated that produce harbored diverse bacterial communities which were dominated by Escherichia coli (29.7%), followed by Serratia liquefacians (13%), Klebsiella pneumoniae (11.4%), Proteus mirabilis (10.8%), Pantoea spp. (8.1%), Salmonella (2.7%), Shigella (0.5%), among others. No Escherichia coli O157:H7 was recovered in produce. Bacterial resistance to antibiotics was highest for erythromycin (22.3%), followed by ampicillin (19.6%), streptomycin (12.8%), and amoxicillin (10.3%). About 9% of the farms had food safety plans in place, 31% tested irrigation water annually, and 93% of growers indicated the need for food safety education. Our results indicate that fresh produce from small farms harbor antibiotic resistant bacteria. Food safety education for growers is needed to cause positive changes in food safety awareness and increased adoption of good agricultural practices by small-scale produce growers.


Small farms Fresh produce Enterobacteriaceae Antibiotic resistance Food safety 



The authors wish to express sincere gratitude the faculty, staff, and students at Tennessee State University and University of Maryland Eastern Shore for their technical and personal assistance during the course of this project.


This research project was financially supported by USDA/NIFA Grant Nos. 2015-38821-24343 and 2014-38821-22427.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


  1. Abadias M, Usall J, Anguera M, Solsona C, Viñas I (2008) Microbiological quality of fresh, minimally-processed fruit and vegetables, and sprouts from retail establishments. Int J Food Microbiol 123:121–129CrossRefPubMedGoogle Scholar
  2. Asai Y, Kaneko M, Ohtsuka K, Morita Y, Kaneko S et al (2008) Salmonella prevalence in seafood imported into Japan. J Food Prot 71:1460–1464CrossRefPubMedGoogle Scholar
  3. Baylis C, Uyttendaele M, Joosten H, Davies A (2011) The Enterobacteriaceae and their significance to the food industry. ILSI Eur Rep Ser 2011:1–48Google Scholar
  4. Beecher C (2013) Fresh produce at farmers markets exempt from new food safety regs. Accessed 22 Dec 2017
  5. Boehme S, Werner G, Klare I, Reissbrodt R, Witte W (2004) Occurrence of antibiotic resistant Enterobacteria in agricultural foodstuffs. Mol Nutr Food Res 48:522–531CrossRefPubMedGoogle Scholar
  6. Callejon RM, Rodriguez-Naranjo MI, Ubeda C, Hornedo-Ortega R, Garcia-Parrilla MC et al (2015) Reported foodborne outbreaks due to fresh produce in the 331 United States and European union: trends and causes. Foodborne Pathog Dis 12:32–38CrossRefPubMedGoogle Scholar
  7. Caponigro V, Ventura M, Chiancone I, Amato Parente L, Piro EF (2010) Variation of microbial load and visual quality of ready-to-eat salads by vegetable type, season, processor and retailer. J Food Microbiol 27:1071–1077CrossRefGoogle Scholar
  8. Centers for Disease Control and Prevention (CDC) (2008) Multi-state outbreak of Salmonella Saintpaul infections linked to raw produce (final update). Accessed 22 Apr 2016
  9. Centers for Disease Control and Prevention (CDC) (2013) Antibiotic resistance threats in the United States. Accessed 22 Dec 2015
  10. Clinical and Laboratory Standards Institute (CLSI) (2014) Performance standards for antimicrobial susceptibility testing; twenty-fourth informational supplement. CLSI document M100-S24. CLSI, Wayne, 34(1)Google Scholar
  11. Erickson MC, Webb CC, Diaz-Perez JC, Phatak SC, Silvoy JJ et al (2010) Infrequent internalization of E. coli O157: H7 into field-grown leafy greens. J Food Prot 73:500–506CrossRefPubMedGoogle Scholar
  12. Esiobu N, Armenta L, Ike J (2002) Antibiotic resistance in soil and water environments. Int J Environ Health Res 12:133–144CrossRefPubMedGoogle Scholar
  13. Falomir MP, Gozalbo D, Rico H (2010) Coliform bacteria in fresh vegetables: from cultivated lands to consumers. Accessed 26 June 2018
  14. Foley SL, Lynne AM (2008) Food animal-associated Salmonella challenges: pathogenicity and antimicrobial resistance. J Anim Sci 86:E173–E187CrossRefPubMedGoogle Scholar
  15. Food Safety Modernization Act (FSMA) (2011) Public law 111-353, 4 Jan 2011. Accessed 12 Dec 2017
  16. Gerba CP, Smith JE (2005) Sources of pathogenic microorganisms and their fate during land application of wastes. J Environ Qual 34:42–48PubMedGoogle Scholar
  17. Golberg D, Kroupitski Y, Belausov E, Pinto R, Sela S (2011) Salmonella typhimurium internalization is variable in leafy vegetables and fresh herbs. Int J Food Microbiol 145:250–257CrossRefPubMedGoogle Scholar
  18. Goodburn C, Wallace CA (2013) The microbiological efficacy of decontamination methodologies for fresh produce: a review. Food Control 32:418–427CrossRefGoogle Scholar
  19. Green LR (2008) Behavioral science and food safety. J Environ Health 71:47–49PubMedGoogle Scholar
  20. Hamilton AJ, Stagnitti F, Premier R, Boland AM, Hale G (2006) Quantitative microbial risk assessment models for consumption of raw vegetables irrigated with reclaimed water. Appl Environ Microbiol 72:3284–3290CrossRefPubMedPubMedCentralGoogle Scholar
  21. Hamilton-Miller JMT, Shah S (2001) Identity and antibiotic susceptibility of enterobacterial flora of salad vegetables. Int J Antimicrob Agents 18:81–83CrossRefPubMedGoogle Scholar
  22. Heaton JC, Jones K (2008) Microbial contamination of fruit and vegetables and the behaviour of enteropathogens in the phyllosphere: a review. J Appl Microbiol 104:613–626CrossRefPubMedGoogle Scholar
  23. Holvoet K, Sampers I, Callens B, Dewul J, Uyttendaele M (2013) Moderate prevalence of antimicrobial resistance in Escherichia coli isolates from lettuce, irrigation water, and soil. Appl Environ Microbiol 79:6677–6683CrossRefPubMedPubMedCentralGoogle Scholar
  24. Hui YH (2014) Plant sanitation for food processing and food service, 2nd edn. Taylor & Francis CRC Press, Boca RatonCrossRefGoogle Scholar
  25. Johnston LM, Jaykus LA, Moll D, Anciso J, Mora B et al (2006) A field study of the microbiological quality of fresh produce of domestic and Mexican origin. Int J Food Microbiol 112:83–95CrossRefPubMedGoogle Scholar
  26. Jonas D, Spitzmüller B, Daschner FD, Verhoef J, Brisse S (2004) Discrimination of Klebsiella pneumoniae and Klebsiella oxytoca phylogenetic groups and other Klebsiella species by use of amplified fragment length polymorphism. Res Microbiol 155:17–23CrossRefPubMedGoogle Scholar
  27. Karlowsky JA, Jones ME, Thornsberry C, Friedland IR, Sahm DF (2003) Trends in antimicrobial susceptibilities among Enterobacteriaceae isolated from hospitalized patients in the United States from 1998 to 2001. Antimicrob Agents Chemother 47:1672–1680CrossRefPubMedPubMedCentralGoogle Scholar
  28. Kim HS, Chon JW, Kim YJ, Kim DH, Kim MS et al (2015) Prevalence and characterization of extended-spectrum-β-lactamase-producing E. coli and Klebsiella pneumoniae in ready-to-eat vegetables. Int J Food Microbiol 207:83–86CrossRefPubMedGoogle Scholar
  29. Kovacs T, Sue Davis S (2014) Bridging the gaps farm guide good agricultural practices and on-farm food safety for small, mid-sized, and diversified fruit and vegetable farms. AGR PUB 307-412 (N/9/14):10. Accessed 26 June 2018
  30. Liu S, Kilonzo-Nthenge A (2017) Prevalence of multidrug-resistant bacteria from US-grown and imported fresh produce retailed in chain supermarkets and ethnic stores of Davidson county, Tennessee. J Food Prot 80:506–514CrossRefPubMedGoogle Scholar
  31. Mcquiston Haslund J, Rosborg Dinesen M, Sternhagen Nielsen AB, LIor C, Bjerrum L (2013) Different recommendations for empiric first-choice antibiotic treatment of uncomplicated urinary tract infections in Europe. Scand J Prim Health Care 31:235–240CrossRefPubMedPubMedCentralGoogle Scholar
  32. Meng J, Doyle MP (2002) Introduction. Microbiological food safety. Microb Infect 4:395–397CrossRefGoogle Scholar
  33. Painter JA, Hoekstra RM, Ayers T, Tauxe RV, Braden CR et al (2013) Attribution of foodborne illnesses, hospitalizations, and deaths to food commodities by using outbreak data, United States, 1998–2008. Emerg Infect Dis 19:407–415CrossRefPubMedPubMedCentralGoogle Scholar
  34. Reddy SP, Wang H, Adams JK, Feng PC (2016) Prevalence and characteristics of Salmonella serotypes isolated from fresh produce marketed in the United States. J Food Prot 79:6–16CrossRefPubMedGoogle Scholar
  35. Ruimy R, Brisabois A, Bernede C, Skurnik D, Barnat S et al (2010) Organic and conventional fruits and vegetables contain equivalent counts of Gram-negative bacteria expressing resistance to antibacterial agents. Environ Microbiol 12:608–615CrossRefPubMedGoogle Scholar
  36. Rusul G, Adzitey F, Huda N (2012) Prevalence and antibiotics resistance of Salmonella serovars in ducks, duck rearing and processing environments in Penang, Malaysia. Food Res Int 45:947–952CrossRefGoogle Scholar
  37. Rutsaert P, Regan Á, Pieniak Z, McConnon Á, Moss A et al (2013) The use of social media in food risk and benefit communication. Trends Food Sci Technol 30:84–91CrossRefGoogle Scholar
  38. Salvadori M, Coleman BL, Louie M, McEwen S, McGeer A (2004) Consumption of antimicrobial-resistant E. coli-contaminated well water: human health impact. PSI Clin Res. 2004:6–25Google Scholar
  39. Schwaiger K, Helmke K, Hölzel CS, Bauer J (2011) Antibiotic resistance in bacteria isolated from vegetables with regards to the marketing stage (farm vs. supermarket). Int J Food Microbiol 148:191–196PubMedGoogle Scholar
  40. Thelfall EJ (2002) Antimicrobial drug resistance in Salmonella: problems and perspectives in food- and water-borne infections. FEMS Microbiol Rev 26:141–148CrossRefGoogle Scholar
  41. Tobin D, Thomson J, Laborde LF, Bagdonis J (2011) Developing GAP training for growers: perspectives from Pennsylvania supermarkets. J Ext 49:5IRB7Google Scholar
  42. Tope AM, Hitter AC, Patel SV (2016) Evaluation of antimicrobial resistance in Enterobacteriaceae and coliforms isolated on farm, packaged and loose vegetables in Kentucky. J Food Microbiol Saf Hyg 1:113CrossRefGoogle Scholar
  43. Walsh C, Fanning S (2008) Antimicrobial resistance in foodborne pathogens: a cause of concern? Curr Drug Targets 9:808–815CrossRefPubMedGoogle Scholar
  44. Wang H, Feng H, Liang W, Luo Y, Malyarchuke V (2009) Effect of surface roughness on retention and removal of E. coli O157:H7 on surfaces of selected fruits. J Food Sci 74:8–15CrossRefGoogle Scholar
  45. Wang H, McEntire JC, Zhang L, Li X, Doyle M (2012) The transfer of antibiotic resistance from food to humans: facts, implications and future directions. Rev Sci Tech 31:249–260CrossRefPubMedGoogle Scholar
  46. Warriner K, Huber A, Namvar A, Fan W, Dunfield K (2009) Recent advances in the microbial safety of fresh fruits and vegetables. Adv Food Nutr Res 57:155–208CrossRefPubMedGoogle Scholar
  47. World Health Organization (WHO), Food and Agriculture Organization of the United Nations (2008) Microbiological hazards in fresh leafy vegetables and herbs: meeting report. World Health Organization, Geneva. Accessed 26 June 2018
  48. Zhang G, Ma L, Phelan VH, Doyle MP (2009) Efficacy of antimicrobial agents in lettuce leaf processing water for control of E. coli O157:H7. J Food Prot 72:1392–1397CrossRefPubMedGoogle Scholar
  49. Zhang M, Oh JK, Cisneros-Zevallos L, Akbulut M (2013) Bactericidal effects of nonthermal low-pressure oxygen plasma on Salmonella Typhimurium LT2 attached to fresh produce surfaces. J Food Eng 119:425–432CrossRefGoogle Scholar
  50. Zheng L, Bae YM, Jung KS, Heu S, Lee SY (2013) Antimicrobial activity of natural antimicrobial substances against spoilage bacteria isolated from fresh produce. Food Control 32:665–672CrossRefGoogle Scholar

Copyright information

© Bundesamt für Verbraucherschutz und Lebensmittelsicherheit (BVL) 2018

Authors and Affiliations

  • Agnes Kilonzo-Nthenge
    • 1
    Email author
  • Siqin Liu
    • 1
  • Fawzy Hashem
    • 2
  • Patricia Millner
    • 3
  • Susan Githua
    • 1
  1. 1.College of AgricultureTennessee State UniversityNashvilleUSA
  2. 2.University of Maryland Eastern ShorePrincess AnneUSA
  3. 3.US Department of Agriculture–ARSBeltsvilleUSA

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