Food Borne Illness

1. Food Borne Illness Infections that require large infective dosage

2. Infections that require large infective dosage BacteriaSalmonella spp.Yersinia enterocolitica and Yersinia pseudotuberculosisVibrio parahaemolyticus and other vibrios Escherichia coli - Enterotoxigenic (ETEC) EnterohemorrhagicHUS Campylobacter jejuni Listeria

3. Enterobacteriaceae • Classification – more than15 different genera

4. Enterobacteriaceae • Morphology and General Characteristics • Gram-negative, non-sporing, rod shaped bacteria • Oxidase – • Ferment glucose and may or may not produce gas in the process (aerogenic vs anaerogenic) • Reduce nitrate to nitrite (there are a few exceptions)

5. Enterobacteriaceae • Are facultative anaerobes • If motile, motility is by peritrichous flagella • Many are normal inhabitants of the intestinal tract of man and other animals • Some are enteric pathogens and others are urinary or respiratory tract pathogens • Differentiation is based on biochemical reactions and and differences in antigenic structure

6. Enterobacteriaceae • Most grow well on a variety of lab media including a lot of selective and differential media originally developed for the the selective isolation of enteric pathogens. • Most of this media is selective by incorporation of dyes and bile salts that inhibit G+ organisms and may suppress the growth of nonpathogenic species of Enterobacteriaceae. • Many are differential on the basis of whether or not the organisms ferment lactose and/or produce H2S.

7. Antigenic Structure of Enterobacteriaceae

8. Escherichia coli • Normal inhabitant of the G.I. tract. • Some strains cause various forms of gastroenteritis. • Is a major cause of urinary tract infection and neonatal meningitis and septicemia.

9. E. coli • May be hemolytic on CBA – more common in pathogenic strains • KEY tests for the normal strain: • TSI is A/A + gas • LIA K/K • Urea – • Indole + • Citrate – • Motility + • There is an inactive biotype that is anaerogenic, lactose – , and nonmotile.

10. Escherichia coli • Virulence factors • Toxins • Enterotoxins and Shigella like Toxins • Enterotoxins causes a movement of water and ions from the tissues to the bowel resulting in watery diarrhea. • There are two types of enterotoxin: LT and ST

11. E. Coli Enterotoxins • LT – is heat labile and LT – is heat labile and alters the activity of sodium and chloride transporters producing an ion imbalance that results in fluid transport into the bowel. • ST – is heat stable and binds to specific receptors with the same results as with LT.

12. Shiga-type toxins • Shiga-type toxin – also called the verotoxin -produced by enterohemorrhagic strains of E. coli (EHEC) • – is cytotoxic, enterotoxic, neurotoxic, and may cause diarrhea and ulceration of the G.I. tract.

13. E. coli infections • Gastroenteritis – there are several distinct types of E. coli that are involved in different types of gastroenteritis: • enterotoxigenic E. coli (ETEC), • enteroinvasive E. coli (EIEC), • enteropathogenic E. coli (EPEC) , • enteroaggregative E. coli (EAEC), and • enterohemorrhagic E. coli (EHEC).

14. Shigella • Shigella • Contains four species that differ antigenically and, to a lesser extent, biochemically.

15. Shigella species • S. dysenteriae (Group A) • S. flexneri (Group B) • S. boydii (Group C) • S. sonnei (Group D) • Biochemistry • TSI K/A with NO gas • LIA K/A • Urea – • Motility - • All ferment mannitol except S. dysenteriae • S. sonnei may show delayed lactose fermentation

16. Shigella species • Virulence factors • Shiga toxin – is produced by S. dysenteriae and in smaller amounts by S. flexneri and S. sonnei. • Acts to inhibit protein synthesis This plays a role in the ulceration of the intestinal mucosa.

17. Shigella • Clinical significance • Causes shigellosis or bacillary dysentery. • Transmission is via the fecal-oral route. • The infective dose required to cause infection is very low (10-200 organisms). • There is an incubation of 1-7 days followed by fever, cramping, abdominal pain, and watery diarrhea (due to the toxin)for 1-3 days. • This may be followed by frequent, scant stools with blood, mucous, and pus (due to invasion of intestinal mucosa). • It is rare for the organism to disseminate. • The severity of the disease depends upon the species one is infected with. • S. dysenteria is the most pathogenic followed by S. flexneri, S. sonnei and S. boydii.

18. Salmonella • Salmonella • Classification has been changing in the last few years. • There is now 1 species: S. enteritica, and 7 subspecies: 1, 2 ,3a ,3b ,4 ,5, and 6. • Subgroup 1 causes most human infections • 2000 sub species

19. Salmonella • Clinically Salmonella isolates are often still reported out as serogroups or serotypes based on the Kauffman-White scheme of classification. • Based on O and H (flagella) antigens • The H antigens occur in two phases; 1 and 2 and only 1 phase is expressed at a given time. • Polyvalent antisera is used followed by group specific antisera (A, B, C1, C2, D, and E) • Salmonella typhi also has a Vi antigen which is a capsular antigen.

20. Salmonella • Biochemistry • TSI K/A + gas and H2S: S. typhi produces only a small amount of H2S and no gas , and S. paratyphi A produces no H2S • LIA K/K with H2S with S. paratyphi A giving K/A results • Urea – • Motility + • Citrate +/- • Indole - • Virulence factors • Endotoxin – may play a role in intracellular survival • Capsule (for S. typhi and some strains of S. paratyphi) • Adhesions – both fimbrial and non-fimbrial

21. Salmonella • Clinical Significance – causes two different kinds of disease: enteric fevers and gastroenteritis. • Both types of disease begin in the same way, but with the gastroenteritis the bacteria remains restricted to the intestine and with the enteric fevers, the organism spreads • Transmission is via a fecal-oral route, i.e., via ingestion of contaminated food or water.

22. Enterobacteriaceae • Proteus, Providencia, and Morganella • Are all part of the NF of the GI tract (except Providencia). • All motile, with Proteus swarming • PA + • Lysine deamination + (LIA R/A) • Urea + for most, strongly + for Proteus • TSI variable (know the reactions for each in the lab!) • Indole – only P. mirabilis is -

23. Proteus, Providencia, and Morganella • Virulence factors • Urease – the ammonia produced may damage the epithelial cells of the UT • Clinical Significance • UT infections, as well as pneumonia, septicemia, and wound infections

24. Enterobacter sakazakii • Enterobacter sakazakii • a Gram-negative rod-shaped pathogenic bacterium. • It is a rare cause of invasive infection with historically high case fatality rates (40–80%) in infants. • From contaminated infant formulas • E. sakazakii as a now classified into a new genus, Cronobacter, comprising five species • For survivors, severe lasting complications can result including neurological disorders.

25. Three ways infant formula get contaminated with Cronobacter sp. ? • a) Through the raw material used for producing the formula; • b) through contamination of the formula or other dry ingredients after pasteurization; and • c) through contamination of the formula as it is being reconstituted by the caregiver just prior to feeding. Can other foods also be contaminated? • Cronobacter sp. has been detected in other types of food, but only powdered infant formula has been linked to outbreaks of disease.

26. Campylobacter Campylobacteriosis Most frequent notified enteric disease • The organism – G-ve, motile, spiral rod • C. jejuni & C. coli • Thermophile (25 to 43 deg. C)

27. Campylobacter Exponential Slender, curved shaped growth morphology

28. Campylobacter • Characteristics - thermophile, survives > 1 hour on hands & moist surfaces - survives refrigeration - can revert to VBNC

29. Campylobacter • The illness - incubation – 2 to 5 days - febrile prodrome - watery/bloody diarrhoea, abdominal pain & nausea

30. Campylobacter • The illness, continued - infective dose – 1 000 to 10 000 cells - any age group; infants < 1 year & young adults; males up to 45 years - Rx – fluids, ? erythromycin (resistance)

31. Campylobacter • Sources - human –faecal-oral person-to-person - animal –ruminants, cats, dogs, flies, birds

32. Campylobacter jejuni

33. Campylobacter • Sources - food –raw poultry, raw milk, offal, red meat - environment –faeces from infected animals contaminate soil & water

34. Yersinia enterocolitica Yersiniosis • The organism – small G-ve rods of family Enterobacteriaceae • Geographical variation in pathogenic serotypes • Serotype O:3 in NZ

35. Yersinia enterocolitica • Characteristics - grows at wide range of temperatures (0 to 44 0 C), aerobically & anaerobically - withstands freezing & survives in damp soil

36. Yersinia enterocolitica • The illness - incubation – 7 days - abdominal pain (confused with appendicitis) - headache, fever, diarrhoea, nausea & vomiting (children – watery, mucoid diarrhoea)

37. Yersinia enterocolitica • The illness, continued - infective dose – unknown - children < 4 years & adults 20-34 years - Rx – antibiotics when serious

38. Yersinia enterocolitica • Sources - human –person-to-person, hospitals - animal –primary source is pigs (tongue & tonsils), companion animals, rats & insects - food –pork & pork products - environment –drinking & surface water, sewage sludge

39. Yersinia enterocolitica

40. Listeria monocytogenes Listeriosis (invasive disease & non-invasive enteritis) • The organism –G+ve ovoid to rod-shaped bacterium • Widespread in environment

41. Listeria monocytogenes • Characteristics - grows in wide range of temperatures (1 to 45o C) - survives freezing - aerobic & anaerobic conditions

42. Listeria monocytogenes • The illness –invasive form - incubation – 30 days - flu’-like symptoms, diarrhoea, vomiting, meningitis, septicaemia, spontaneous abortion

43. Listeria monocytogenes • The illness –invasive form, continued - infective dose – 100 to 1 000 cells - pregnant women, newborn babies, the elderly & AIDS patients - Rx – penicillin, ampicillin +/- gentamicin

44. Listeria monocytogenes • The illness –non-invasive - incubation – 18 hours - diarrhoea, fever, muscle pain, headache, abdominal cramps & vomiting

45. Listeria monocytogenes • The illness –non-invasive - infective dose – > 100 thou. cells/gm - all individuals susceptible - Rx - penicillin, ampicillin +/- gentamicin

46. Listeria monocytogenes • Sources - human –person-to-person rare - animal –diseased animals shed in faeces, contamination of red meat; silage - food –ready-to-eat cooked food with long shelf-life -raw foods - environment –widespread in soil, water & sewage (Hospitals & occupational exposure)

47. Listeria monocytogenes

48. Vibrio, Aeromonas & Plesiomonas

49. General Characteristics of Vibrio, Aeromonas and Plesiomonas • Similarities to Enterobacteriaceae • Gram-negative • Facultative anaerobes • Fermentative bacilli • Differences from Enterobacteriaceae • Polar flagella • Oxidase positive • Formerly classified together as Vibrionaceae • Primarily found in water sources • Cause gastrointestinal disease • Shown not closely related by molecular methods

50. Morphology & Physiology of Vibrio • Comma-shaped (vibrioid) bacilli • V. cholerae, V. parahaemolyticus, V. vulnificusare most significant human pathogens • Broad temperature & pH range for growth on media • 18-37C • pH 7.0 - 9.0 (useful for enrichment) • Grow on variety of simple media including: • MacConkey’s agar • TCBS (Thiosulfate Citrate Bile salts Sucrose) agar • V. cholerae grow without salt • Most other vibrios are halophilic