Please enable JavaScript.
Coggle requires JavaScript to display documents.
Lecture 1: Foodborne bacteria (Foodborne pathogens (2. Shigella (Examples,…
Lecture 1: Foodborne bacteria
Food poisoning
Definition
A
disturbance
of the gastrointestinal tract following the consumption of
contaminated food or water
.
Similar terms: foodborne disease / foodborne infections and intoxication.
5 sources of bacteria causing foodborne diseases
Infection or natural carriage of toxigenic microorganisms on
body surfaces of food handlers
.
Seawater and marine
materials.
Nasal and throat discharges
of sick individuals or asymptomatic carriers.
Infected
soil, mud, surface waters and dust
.
Fecal matter
and/or
urine
of infected animals or humans.
Symptoms
Common: nausea, vomiting and diarrhea; with or without fever.
Serious cases: septicemia or involvement of the nervous system.
Prevention based on:
Knowing the sources of the etiologic agents.
Route transmission.
Foodborne pathogens
1.
Campylobacter
Characteristics
Gram-negative, microaerophilic, oxidase-positive, thin, curved rod
Motile by means of a single polar flagellum
Cause gastroenteritis
Facultative anaerobic and fermentative
Examples (17 species and 6 subspecies)
Frequently:
C. jejuni, C. coli
Rare:
C. lari, C. upsaliensis
Sources and transmission
Sources: warm-blooded animals
Transmission: undercooked meat and meat products, raw or contaminated milk, contaminated water or ice
Treatment
Electrolyte replacement and rehydration
Antimicrobial treatment - erythromycin, tetracycline, quinolones
2.
Shigella
Characteristics
Shigellosis
- also known as bacillary dysentery
Facultative anaerobic gram-negative rods
Toxin responsible -
Shiga toxin
Sources and transmission
Transmission: human intestine, person-to-person contact, contaminated food
Sources: residents of the intestinal tract of humans, apes and monkeys
Examples
S. flexneri
S. sonnei
S. dysenteriae
S. boydii
Symptoms
Stool - contain blood, pus or mucus
Diarrhea, fever, vomiting, nausea, stomach cramps
Treatment
Severe dysentery - ampicillin, TMP-SMX, fluoroquinolones (ciprofloxacin); rehydration
3.
Staphylococcus aureus
Characteristics
Facultative anaerobe that ferment mannitol
Colonies - smooth and buttery and a golden yellow color, but can range in color from white to yellow-orange
Mainly in irregular, grapelike clusters
Secretes an enzyme (coagulase) - causes fibrin in blood plasma to clot
Gram-positive coccus
Sources and transmission
Transmission: Open skin lesion (boil), nasal passages
Source: Protein containing food (ham/chicken salad), custard filling for dessert
Food poisoning (three exotoxins which are heat-stable proteins) -
S. aureus
enterotoxins*
1st & 2nd enterotoxins -
inhibits water absorption
from the intestine,
induce diarrhea
and
causes vomiting
3rd enterotoxin -
damages the intestinal epithelium
and
causes colitis
, or
inflammation of the large intestinal lining
Symptoms
Nausea, vomiting, abdominal cramps, frequent watery diarrhea, absence of fever, body temperature is lower than normal
Treatment
Penicillin; common - penicillinase-resistant B-lactam antibiotic (oxacilin or flucloxacillin)
Combination therapy with gentamicin to treat serious infections (endocarditis) - controversial due to high risk of damage to the kidneys
4.
Clostridium botulinum
Characteristics
Gram-positive endospore forming rod; anaerobic bacteria
Forms oval, sub-terminal endospores that tend to swell the cell
Widely distributed - soil, pond, lake sediment
Produces an enzyme (lipase) - degrades lipids when it is grown on egg yolk
Botulism
Caused by exotoxins; very sensitive to heat, readily destroyed or inactivated by ordinary cooking and boiling (100 C, 212 F); neurotoxins - affecting the central nervous system
Symptoms
Neurological symptoms: blurred or double vision, slurred speech, labored breathing, difficulty in swallowing accompanied by dry mouth
Effects: general flaccid (limp) paralysis, reflect loss of the ability to transmit nerve impulse
Death may occur from respiratory failure within 12-24 hours
Source
Home or commercially canned "low acid" veges and fruits
5. Other endospore-forming bacteria
(typical illness: diarrhea, abdominal cramps, nausea and vomiting)
Bacillus cereus
Facultative anaerobic
Soil
Produce heat-stable exotoxin that is not easily destroyed
Clostridium perfringens
Anaerobe
found in soil, intestines of humans and other animals, sewage
6. Other gram-positive bacteria (
Listeria monocytogenes
)
Regular, non-endospore forming, gram-positive rod
Sources
Dairy products, packaged meat products, fruits and vegetables
Main reservoirs: forage, silage, infected animals and humans
Effects
Meningitis (inflammation by an infection of the meninges - three membranes that cover the brain and spinal cord)
Sudden fever, intense headache, nausea, vomiting, neurological indications of meningitis (nervous irritation)
7. Gram-negative facultatively anaerobic bacteria (
Salmonella
bacteria & gastroenteritis)
Examples:
S. enterica, S. enteriditis, S. thyphimurium, S. enterica
serovar
typhi
(causes typhoid fever)
Common sources: meat and eggs
Symptoms: Nausea, vomiting, fever, diarrhea, abdominal cramps
Treatment: oral or injected antibiotics
Transmission: Bacteria travel to
small intestine
, adhere to lining and begin life cycle. Severe case - bacteria break through intestinal wall to bloodstream, can be deadly if not properly treated
WHO Fact Sheet (Foodborne pathogens)
Bovine Spongiform Encephalopathy (BSE)
Shigella
species
Campylobacter
Salmonella
Escherichia coli
infections