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Occurrence of Listeria monocytogenes in traditionally processed fish in informal markets in Accra, Ghana

Presentation by K. Tano-Debrah, B. Bediako-Amoa, F.K. Saalia and K. Bomfeh at the 27th biennial conference of the Ghana Science Association on "Promoting the development of agro-processing industries to enhance value addition for local and export markets: The role of science and technology", Kumasi, Ghana, 10-15 July 2011.

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Occurrence of Listeria monocytogenes in traditionally processed fish in informal markets in Accra, Ghana

  1. 1. Occurrence of Listeria monocytogenes in traditionally processed fish in informal markets in Accra, Ghana K. Tano-Debrah, B. Bediako-Amoa, F.K. Saalia and K. Bomfeh Presented at the 27th biennial conference of the Ghana Science Association Kumasi, Ghana, 10-15 July 2011
  2. 2. INTRODUCTION
  3. 3. • Listeria monocytogenes is a pathogenic bacterium – Causes a highly fatal disease called listeriosis • The organism is Gram-positive, rod-shaped, and nonspore forming. • It is ubiquitous in nature - found in soil, dust, fresh and salt water, decaying vegetation, silage, slaughter house waste, sewage effluent, and as biofilms on food processing and hospital equipments • About 2 to 10% of healthy individuals are asymptomatic carriers of the organism Department of Nutrition and Food Science, Univ. of Ghana
  4. 4. • L. monocytogenes is considered the leading cause of death among food-borne bacterial pathogens, with a fatality rate of 20-30%, and up to 75% in highly immunocompromised individuals Pathogen Illnesses Deaths % 2000) Table 1: Fatality of L. monocytogenes infection (CDC,Deaths Campylobacter spp. 10,539 99 0.95 Salmonella non-typhoidal 15,608 553 3.54 L. monocytogenes 2,298 499 21.71 Department of Nutrition and Food Science, Univ. of Ghana
  5. 5. Some clinical manifestations of listeriosis Septicaemia Pre-term delivery Department of Nutrition and Food Science, Univ. of Ghana
  6. 6. Foods frequently contaminated • Whole milk, skim milk • Soft cheese • Processed meats, red meat • Vacuum packaged beef and poultry products • Lettuce • Coleslaw, and • Fried rice • Smoked fish • Salted fish Department of Nutrition and Food Science, Univ. of Ghana
  7. 7. RATIONALE • Ghana is a heavy consumer of fish • Over 80% of fish landings are processed traditionally • Smoked and salted fish are known to be vehicles for the transmission of Listeria monocytogenes • No data on the occurrence of the pathogen in traditionally processed fish Department of Nutrition and Food Science, Univ. of Ghana
  8. 8. OBJECTIVE • To determine the presence and concentration of Listeria monocytogenes in – Hot-smoked fish (salmon, tuna, herrings) – Salted fish (koobi, momoni, kako) – Sundried sardines Department of Nutrition and Food Science, Univ. of Ghana
  9. 9. METHODS
  10. 10. Sampling • Twelve (12) samples of each fish product were purchased from four informal markets in Accra (Madina, Kaneshie, Agbogbloshie and Jamestown markets) for analysis. • The United States Department of Agriculture (USDA) protocol for L. monocytogenes detection and enumeration was used. Department of Nutrition and Food Science, Univ. of Ghana
  11. 11. USDA Protocol • Sample enrichment in Listeria Enrichment broth for 24 hours at 35-37oC • Secondary enrichment in Fraser broth for 24 hours at 35-37oC • Plating on selective agar (Oxford) at 35-37oC for up to 48 hours • Confirmation of presumptive L. monocytogenes isolates Department of Nutrition and Food Science, Univ. of Ghana
  12. 12. Primary Enrichment LEB, 37oC, 24h Secondary Enrichment Fraser, 37oC, 24h Plating on Oxford or Chromagar, 37oC, 24-28h Department of Nutrition and Food Science, Univ. of Ghana
  13. 13. • Prevalence was determined as the percentage of samples in which the organism was isolated • Concentration was expressed as the colony forming units of L. monocytogenes per gram of fish • Plates containing up to 150 colonies were considered useful for enumeration (HPA, 2009) Department of Nutrition and Food Science, Univ. of Ghana
  14. 14. RESULTS & DISCUSSION
  15. 15. Overview • L. monocytogenes was isolated in at least one sample of each product • Counts were generally low • Load: Smoked fish > salted fish > dried fish Department of Nutrition and Food Science, Univ. of Ghana
  16. 16. Table 1: Prevalence* of Listeria monocytogenes in traditionally processed fish purchased from some informal markets in Accra KA KO MO TU SA HR DR Madina 100 66.7 66.7 100 100 100 100 Kaneshie 33.3 66.7 66.7 100 100 66.7 66.7 Jamestown 33.3 33.3 66.7 100 100 66.7 33.3 Agbogbloshie 66.7 33.3 33.3 66.7 100 66.7 33.3 KA-kako KO-koobi MO-momoni TU-tuna SA-salmon HR-herrings DR-dried fish * % Department of Nutrition and Food Science, Univ. of Ghana
  17. 17. Prevalence (%) 100 100 91.68 75.03 80 58.35 60 58.35 58.33 MO DR 50 40 20 0 TU SA HR KA KO Type of traditionally processed fish Fig. 1: Prevalence of Listeria monocytogenes in traditionally processed fish purchased from some informal markets in Accra KA-kako SA-salmon KO-koobi HR-herrings MO-momoni DR-dried fish Department of Nutrition and Food Science, Univ. of Ghana TU-tuna
  18. 18. 16.00 16.00 14.00 14.00 x102 CFU/g 12.00 10.00 8.00 5.00 6.00 4.00 4.00 4.00 2.00 1.00 2.00 0.00 KA KO MO TU SA HR Type of fish Fig. 2: Average counts of L. monocytogenes in fish samples KA-kako KO-koobi SA-salmon MO-momoni HR-herrings TU-tuna DR-dried fish` Department of Nutrition and Food Science, Univ. of Ghana DR
  19. 19. Table 2: Average counts* of Listeria monocytogenes in traditionally processed fish purchased from some informal markets in Accra KA KO MO TU SA HR DR Madina 7 6 3 21 29 8 3 Kaneshie 6 9 5 17 15 0 0 Jamestown 1 2 1 12 9 9 2 Agbogloshie 1 0 0 8 10 1 0 Average 4 4 2 14 * x102 CFU/g Department of Nutrition and Food Science, Univ. of Ghana 16 5 1
  20. 20. Table 2: Average counts* of Listeria monocytogenes in traditionally processed fish purchased from some informal markets in Accra KA KO MO TU SA HR DR Madina 7 6 3 21 29 8 3 Kaneshie 6 9 5 17 15 0 0 Jamestown 1 2 1 12 9 9 2 Agbogloshie 1 0 0 8 10 1 0 Average 4 4 2 14 16 5 1 * x102 CFU/g Department of Nutrition and Food Science, Univ. of Ghana
  21. 21. Table 2: Average counts* of Listeria monocytogenes in traditionally processed fish purchased from some informal markets in Accra KA KO MO TU SA HR DR Madina 7 6 3 21 29 8 3 Kaneshie 6 9 5 17 15 0 0 Jamestown 1 2 1 12 9 9 2 Agbogloshie 1 0 0 8 10 1 0 Average 4 4 2 14 * x102 CFU/g Department of Nutrition and Food Science, Univ. of Ghana 16 5 1
  22. 22. CONCLUSIONS • Listeria monocytogenes is found in traditionally processed fish on informal markets in Accra, albeit in low concentrations • Traditionally processed fish on informal markets could be potential vehicles for the transmission of Listeria monocytogenes to consumers
  23. 23. THANK YOU

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