Food Borne Illness

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Food Borne Illness

• Infections that require large infective dosage

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Infections that require large infective dosage

• Bacteria  Salmonella spp.  Yersinia
  enterocolitica and Yersinia pseudotuberculosis
   Vibrio parahaemolyticus and other vibrios
   Escherichia coli -             Enterotoxigenic
  (ETEC)             Enterohemorrhagic
              HUS
• Campylobacter jejuni
• Listeria

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Enterobacteriaceae
Lactoes Ferm ve Escherichia Enterobacter Citrobacter Klebsiella Pectinobacterium Lactoes Ferm ve Shigella Edwardsiella Salmonella Hafnia Serratia Proteus Providencia Morganella Yersinia Erwinia

• Classification more than15 different genera

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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)

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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

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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.

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Antigenic Structure of Enterobacteriaceae
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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.

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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.

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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

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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.

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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.

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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).

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Shigella

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

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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

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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.

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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.

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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

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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.

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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

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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.

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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 -

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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

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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 (4080) 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.

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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.

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Campylobacter

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

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Campylobacter

• 
  Exponential
• Slender, curved shaped growth
• morphology
  

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Campylobacter

• Characteristics
• - thermophile, survives gt 1 hour on
• hands moist surfaces
• - survives refrigeration
• - can revert to VBNC

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Campylobacter

• The illness
• - incubation 2 to 5 days
• - febrile prodrome
• - watery/bloody diarrhoea,
• abdominal pain nausea

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Campylobacter

• The illness, continued
• - infective dose 1 000 to 10 000 cells
• - any age group infants lt 1 year
  young
• adults males up to 45 years
• - Rx fluids, ? erythromycin
• (resistance)

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Campylobacter

• Sources
• - human faecal-oral person-to-person
• - animal ruminants, cats, dogs, flies,
• birds

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Campylobacter jejuni
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Campylobacter

• Sources
• - food raw poultry, raw milk, offal,
  red
• meat
• - environment faeces from infected
• animals
  contaminate soil
• water

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Yersinia enterocolitica

• Yersiniosis
• The organism small G-ve rods of family
  Enterobacteriaceae
• Geographical variation in pathogenic serotypes
• Serotype O3 in NZ

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Yersinia enterocolitica

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

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Yersinia enterocolitica

• The illness
• - incubation 7 days
• - abdominal pain (confused with
  appendicitis)
• - headache, fever, diarrhoea, nausea
• vomiting (children watery, mucoid
  diarrhoea)

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Yersinia enterocolitica

• The illness, continued
• - infective dose unknown
• - children lt 4 years adults 20-34 years
• - Rx antibiotics when serious

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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
  

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Yersinia enterocolitica
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Listeria monocytogenes

• Listeriosis
• (invasive disease non-invasive enteritis)
• The organism Gve ovoid to rod-shaped bacterium
• Widespread in environment

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Listeria monocytogenes

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

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Listeria monocytogenes

• The illness invasive form
• - incubation 30 days
• - flu-like symptoms, diarrhoea,
• vomiting, meningitis, septicaemia,
• spontaneous abortion

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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
  

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Listeria monocytogenes

• The illness non-invasive
• - incubation 18 hours
• - diarrhoea, fever, muscle pain,
• headache, abdominal cramps
• vomiting

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Listeria monocytogenes

• The illness non-invasive
• - infective dose gt 100 thou. cells/gm
• - all individuals susceptible
• - Rx - penicillin, ampicillin /-
• gentamicin

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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)

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Listeria monocytogenes
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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

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Morphology Physiology of Vibrio

• Comma-shaped (vibrioid) bacilli
• V. cholerae, V. parahaemolyticus, V. vulnificus
  are 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
• MacConkeys agar
• TCBS (Thiosulfate Citrate Bile salts Sucrose)
  agar
• V. cholerae grow without salt
• Most other vibrios are halophilic

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Vibrio spp. (Family Vibrionaceae) Associated with
Human Disease
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Epidemiology of Vibrio spp.

• Vibrio spp. (including V. cholerae) grow in
  estuarine and marine environments worldwide
• All Vibrio spp. can survive and replicate in
  contaminated waters with increased salinity and
  at temperatures of 10-30oC
• Pathogenic Vibrio spp. appear to form symbiotic
  (?) associations with chitinous shellfish which
  serve as an important and only recently
  recognized reservoir
• Asymptomatically infected humans also serve as an
  important reservoir in regions where cholera is
  endemic

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Taxonomy of Vibrio cholerae

• gt200 serogroups based on somatic O-antigen
• O1 and O139 serogroups are responsible for
  classic epidemic cholera
• O1 serogroup subdivided into
• Two biotypes El Tor and classical (or cholerae)
• Three serotypes ogawa, inaba, hikojima
• Some O1 strains do not produce cholera
  enterotoxin (atypical or nontoxigenic O1 V.
  cholerae)
• Other strains are identical to O1 strains but do
  not agglutinate in O1 antiserum (non-cholera
  (NCV) or non-agglutinating(NAG) vibrios) (non-O1
  V.cholerae)
• Several phage types

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Epidemiology of Vibrio cholerae

• Cholera recognized for more than two millennia
  with sporadic disease and epidemics
• Endemic in regions of Southern and Southeastern
  Asia origin of pandemic cholera outbreaks
• Generally in communities with poor sanitation
• Seven pandemics (possible beginning of 8th) since
  1817 attributable to increased world travel
• Cholera spread by contaminated water and food
• Human carriers and environmental reservoirs

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Recent Cholera Pandemics

• 7th pandemic
• V. cholerae O1 biotype El Tor
• Began in Asia in 1961
• Spread to other continents in 1970s and 1980s
• Spread to Peru in 1991 and then to most of South
  Central America and to U.S. Canada
• By 1995 in the Americas, gt106 cases 104 dead
• 8th pandemic (??)
• V. cholerae O139 Bengal is first non-O1 strain
  capable of causing epidemic cholera
• Began in India in 1992 and spread to Asia, Europe
  and U.S.
• Disease in humans previously infected with O1
  strain, thus no cross-protective immunity

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Pathogenesis of V.cholerae

• Incubation period 2-3 days
• High infectious dose gt108 CFU
• 103 -105 CFU with achlorhydria or hypochlorhydria
  (lack of or reduced stomach acid)
• Abrupt onset of vomiting and life-threatening
  watery diarrhea (15-20 liters/day)
• As more fluid is lost, feces-streaked stool
  changes to rice-water stools
• Colorless
• Odorless
• No protein
• Speckled with mucus

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Pathogenesis of V.cholerae (cont.)

• Cholera toxin leads to profuse loss of fluids and
  electrolytes (sodium, potassium, bicarbonate)
• Hypokalemia (low levels of K in blood)
• Cardiac arrhythmia and renal failure
• Cholera toxin blocks uptake of sodium chloride
  from lumen of small intestine
• Death attributable to
• Hypovolemic shock (due to abnormally low volume
  of circulating fluid (plasma) in the body)
• Metabolic acidosis (pH shifts toward acid side
  due to loss of bicarbonate buffering capacity)

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Treatment Prevention of V. cholerae

• Untreated 60 fatality
• Treated lt1 fatality
• Rehydration supportive therapy
• Oral
• Sodium chloride (3.5 g/L)
• Potassium chloride (1.5 g/L)
• Rice flour (30-80g/L)
• Trisodium citrate (2.9 g/L)
• Intravenous (IV)
• Doxycycline or tetracycline (Tet resistance may
  be developing) of secondary value
• Water purification, sanitation sewage treatment
• Vaccines

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Laboratory Identification of Vibrios

• Transport medium - Cary-Blair semi-solid agar
• Enrichment medium - alkaline peptone broth
• Vibrios survive and replicate at high pH
• Other organisms are killed or do not multiply
• Selective/differential culture medium - TCBS agar
• V. cholerae grow as yellow colonies
• Biochemical and serological tests

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Characteristics and Epidemiology of Aeromonas
(Family Aeromonadaceae)

• Gram-negative facultatively anaerobic bacillus
  resembling members of the Enterobacteriaceae
• Motile species have single polar flagellum
  (nonmotile species apparently not associated with
  human disease)
• 16 phenospecies Most significant human
  pathogens A. hydrophila, A. caviae, A. veronii
  biovar sobria
• Ubiquitous in fresh and brackish water
• Acquired by ingestion of or exposure to
  contaminated water or food

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Clinical Syndromes of Aeromonas

• Associated with gastrointestinal disease
• Chronic diarrhea in adults
• Self-limited acute, severe disease in children
  resembling shigellosis with blood and leukocytes
  in the stool
• 3 carriage rate
• Wound infections
• Opportunistic systemic disease in
  immunocompromised
• Putative virulence factors include endotoxin
  hemolysins eneterotoxin proteases
  siderophores adhesins

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Afimbriated Aeromonas hydrophila
Nonadherent Afimbriated Bacterial Cells and
Buccal Cells
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Fimbriated Aeromonas hydrophila
Adherent Fimbriated Bacterial Cells and Buccal
Cells
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Characteristics of Plesiomonas

• Formerly Plesiomonadaceae
• Closely related to Proteus now classified as
  Enterobacteriaceae despite differences
• Oxidase positive
• Multiple polar flagella (lophotrichous)
• Single species Plesiomonas shigelloides
• Isolated from aquatic environment (fresh or
  estuarine)
• Acquired by ingestion of or exposure to
  contaminated water or seafood or by exposure to
  amphibians or reptiles
• Self-limited gastroenteritis secretory, colitis
  or chronic forms
• Variety of uncommon extra-intestinal infections

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Characteristics of Aeromonas and Plesiomonas
Gastroenteritis
Epidemiological Features Aeromonas Plesiomonas
Natural Habitat Source of Infection Fresh or brackish water Contaminated water or food Fresh or brackish water Contaminated water or food
Clinical Features
Diarrhea Vomiting Abdominal Cramps Fever Blood/WBCs in Stool Present Present Present Absent Absent Present Present Present Absent Present

Pathogenesis Enterotoxin (??) Invasiveness