Foodborne Diseases Flashcards
S. aureus
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause: Direct contact from food handler
Specific Signs/symptoms:
Epidemiology:
Causes diarrhea in 1/3 of cases
Incubation 1-6 h, duration < 24 h
Characteristics: Stable: withstand acid, proteolysis, and heat at 100°C for 30 min;
Pathogenesis: SEA (most important) in foods (Salty, high fat; eggs; improperly handled foods)
Diagnosis:
Prevention:
Treatment:
Bacillus cereus
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause: Spores found in soil and on grains; Foods, like rice, improperly stored, allow spores to germinate into
bacteria
Specific Signs/symptoms
Epidemiology
Characteristics:
- Emetic toxin forms in food, has short incubation of 1-5 hr and causes nausea and vomiting. Heat- stable.
- Enterotoxin forms in intestine after spores germinate and causes diarrhea. Long incubation period of 6-15 hrs. 1
Pathogenesis
Diagnosis
Prevention
Treatment
Clostridium perfringes
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause: Improperly cooked or stored meat/gravy
Specific Signs/symptoms
Epidemiology: 2nd most common bacterial cause in US
Characteristics: Incubation period 8-16 h, duration < 24-48 h
Pathogenesis:
– Enterotoxin: heat-labile pore-forming cytotoxin
– Damages ileal brush border–> loss of fluid and intracellular proteins into diarrhea fluid
– Also provokes nausea, vomiting in some cases
Diagnosis
Prevention
Treatment
Norovirus
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause: fecal-oral but usually by contact
Specific Signs/symptoms:
• Clinically similar to other infectious gastroenteritides, usually no
blood or mucus in stool
• Incubation period 48 h
• Symptoms:
– Sudden onset vomiting and/or watery diarrhea (usually both) - no blood, no mucus
– Short duration: 1 to 3 days
– Usually no fever
• Self-limiting and milder than rotavirus infection
Epidemiology:
Norovirus: Worldwide distribution; Most common cause of acute infectious diarrhea (20 million/y
in US)
Characteristics: Resists chlorine; Easily transmitted, highly infectious
Pathogenesis
Diagnosis: not usually confirmed – ELISA, PCR/RT-PCR, agglutination
Prevention
Treatment
Vibrio cholerae
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause
Specific Signs/symptoms:
Serogroups that produce cholera toxin (CTXΦ phage)
– O1 (Classical and El Tor biotypes), cause pandemics
– O139, epidemic strain emerged in early 1990s
Epidemiology:
• Where is it found?
– Mostly in developing countries of Haiti, South America (Peru, Ecuador, Colombia), Asia (India), and Africa
• How is it transmitted?
– Reservoir is human colon
– Ingested via fecally-contaminated water, food
– Rare cases in U.S. Gulf Coast region – contaminated undercooked seafood
• High infectious dose required to establish infection
– Lower infectious dose with achlorhydria/hypochlorhydria/PPI use
– Lower infectious dose in food than water
Characteristics:
• Abrupt onset of RICE WATER diarrhea and vomiting, can be profuse – Up to 1 L per hour in most severe cases
• Incubation period 16-72 h
• May progress from first liquid stool to hypovolemic shock in 4-12 h
• ~60% mortality if untreated
Pathogenesis:
• TCP = toxin co-regulated pilus
– Adherence to the mucosal lining the intestine
• Lysogenic bacteriophage (CTXΦ)
– Carries ctxA/ctxB genes encoding cholera toxin subunits
• Cholera toxin
– Heat-labile A:5B enterotoxin
– Ganglioside GM1 receptors on intestinal epithelial cells
– ADP-ribosylates Gαs protein–>activates host adenylate cyclase –> cAMP levels rise –> hypersecretion of electrolytes and water
Diagnosis:
– Direct microscopy for motility
– Culture of fresh stool required for confirmation
• Thiosulfate Citrate Bile salts Sucrose (TCBS) agar
• Alkaline pH, NaCl (selective)
– Yellow-gold colonies (sucrose-fermenter; differential)
– Oxidase positive
Prevention:
– Improve sanitation to prevent water supply contamination
– Several oral vaccines available in some countries
Treatment:
Treatment (supportive and specific)
– Fluid & electrolyte replacement
– Antibiotic therapy can halve diarrheal fluid output and duration of illness
Enterobacteriaceae
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Clostridium difficile
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause
Specific Signs/symptoms
Epidemiology:
– Antibiotic exposure ~5-10 d before
– Hospitalization
Characteristics:
Anaerobic, Gram-pos bacillus, spore-forming
– Contact: Spores survive for months on surfaces
– Endogenous: Some individuals are carriers (~20-50%, healthcare associated)
Pathogenesis:
• Some strains non-toxigenic – don’t cause disease
• Toxin A (TcdA) and Toxin B (TcdB)
– Both endocytosed, glucosylate Rho proteins, which regulate cytoskeleton structure –> cell rounding, ulceration, apoptosis, disrupt tight junctions
– Both are chemotactic for neutrophils
– Toxin A directly activates neutrophils
– Toxin B much more potent than toxin A
• Hypervirulent strain
– Mutation in toxin regulatory mechanism – produce more toxin
Diagnosis: • Toxin EIA, for toxins A&B or A – Rapid, inexpensive, highly spec – Sen 75% ([toxin] too low) • PCR for toxin gene(s) – sens and spec, fast
Prevention:
– Hand hygiene with soap and water, not hand sanitizers (why?)
– Contact isolation: glove/gowns, dedicated equipment
Treatment:
– Discontinue broad-spectrum antibiotic if possible
– Initiate specific antibiotic therapy
• Oral probiotics with antibiotic therapy of uncertain benefit
– Fecal transplant if antibiotics fail, multiple relapses
Yersinia enterocolitica
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause: Reservoir in pigs, sheep, and other farm animals
Specific Signs/symptoms
Epidemiology:
Causes fever, diarrhea, abdominal pain
• Causes mesenteric adenitis, presents like appendicitis
• Patients sometimes undergo unnecessary appendectomy
Characteristics:
Gram-negative rod
• Lactose negative: beige colonies on MacConkey agar
• Urease-positive
Pathogenesis
Diagnosis
Prevention
Treatment
Campylobacter
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause:
Anyone can be infected, PPIs increase susceptibility
• Transmitted by ingestion of raw or undercooked poultry/poultry products
(C. jejuni), pork (C. coli), unpasteurized milk, untreated water, pet dogs (C. upsaliensis)
Specific Signs/symptoms
Epidemiology
Characteristics
Pathogenesis:
• Fecal-oral transmission from animals, human patients or carriers
• Incubation period usually 2-4 d
• Invasive, inflammatory
• Important cause of Guillain-Barré syndrome (temporary autoimmune
disease; antibodies to O antigen recognize some human gangliosides); reactive arthritis
Diagnosis
Definitive diagnosis based on culture, cell morphology, biochemical tests
– Culture on selective medium (Campy-BAP, Skirrow medium)
• Antibiotics for inhibition of normal flora
• 2-3days
Prevention
Treatment: Abx only for severe disease
Shigella spp
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause:
- Fecal-oral transmission, low infectious dose (10-100 cells), resistant to acid
– Highly communicable: direct contact (hands), contaminated water/food
Specific Signs/symptoms
Epidemiology
Characteristics: • Most do not produce gas from glucose (unusual for enteric fermenter) • Lactose - • H2S– • Motility – • Urease -
3 important species
– Shigella sonnei – most common in developed countries
• day care centers, nurseries, custodial institutions; often children/parents
• Incubation 1-3 d, duration wide range (7 d common)
– Shigella flexneri – more often in developing countries
– Shigella dysenteriae type 1 - most severe form, mostly developing countries
Pathogenesis:
• Attach to M cells in Peyer patches
• Enter M cells
– Lyse phagocytic vacuole, replicate in cytoplasm
• Spread to adjacent cells via actin “tails” → more inflammation
• S. dysenteriae produce Shiga toxin (Stx)
Diagnosis
Prevention
Treatment
Salmonella enterica
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause
Specific Signs/symptoms:
• Watery diarrhea, cramps, fever; maybe nausea/vomiting, headache, myalgias
• Rarely bloody: some pediatric, geriatric, immunocompromised
Epidemiology:
• Anybody is susceptible
• Reservoir: virtually all animals (poultry, livestock) – a zoonosis, usually asymptomatic
– Food: common sources are eggs, poultry, dairy products,
Characteristics
2 groups:
– Non-typhoidal Salmonella serovars (e.g. Enteritidis, Typhimurium, etc.) –> salmonellosis!! (gastroenteritis)
• Watery diarrhea, cramping, fever, may have nausea/vomiting, myalgias,
headache
• Usually no RBC, WBC+
• Incubation 6-48 h, duration 2-7 d, carried for several weeks after
• Can lead to bacteremia in immunocompromised, but rare
– Salmonella Typhi, Paratyphi –> typhoid fever (enteric fever)
Pathogenesis:
• Invade M cells in Peyer patches and enterocytes via trigger mechanism and membrane ruffling (Sip proteins via T3SS)
• Replicate in endocytic vacuoles
• Various proteins induce neutrophil chemotaxis and inflammation, damage causes fluid secretion
Diagnosis
Prevention:
– Inspection and monitoring of livestock production
– Proper preparation of poultry and egg dishes
– Avoid cross contamination of other foods
– Identify and treat carriers (4-5 weeks after infection,
chronic)
Treatment:
– Antibiotics do not reduce duration, can increase carriage
• Only use if immunocompromised or if blood cultures (+)
Listeria monocytogenes
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause:
Carried by food (milk, cheese, meats[beef], raw vegetables) entering through the intestine
Specific Signs/symptoms:
fever, nausea, diarrhea, sepsis, meningitis
Epidemiology:
• Adults predisposed by pregnancy, malignancies, diabetes, alcoholism, immunosuppression
• Neonates can acquire during vaginal delivery and develop meningitis or sepsis
• More mononuclear cells in CSF than for other bacteria
Characteristics:
Gram positive bacillus; Non-sporulating; Facultative intracellular organism; Grows (slowly) in refrigerator
Pathogenesis
Diagnosis
Prevention: inspection of dairies, ice cream plants for cultures, danger of breaks in pasteurizing during packaging
Treatment
Rotovirus
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause
Specific Signs/symptoms
Epidemiology:
• Reoviridae family
• Worldwide distribution
• Childhood diarrhea epidemics, rarely as outbreaks (institutional populations and
hospitals)
– Long duration of viral shedding
• High risk groups:
– Children under 2 years of age
– Malnourished people
– The elderly and institutionalized populations
– Personnel attending to sick or asymptomatic carriers
• 20 to 25% of total deaths due to diarrhea, 5% of all deaths in children under 5
• 1,200 childhood deaths/day, mostly in the developing world (in US, 20-60/y)
Characteristics:
• Approximately 50% of infections are asymptomatic
• Most severe in < 2 years and the elderly
Pathogenesis:
– Incubation period < 48 h
– Sudden onset of vomiting - 1 or 2 d
– Followed by watery diarrhea (no blood) - Approximately 5 d
• Abdominal cramps, low-grade fever, dehydration
Diagnosis
Prevention
Treatment:
Self-limiting if patient survives
Live attenuated vaccines: Rotarix, RotaTeq
E. coli
Cause Specific Signs/symptoms Epidemiology Characteristics Pathogenesis Diagnosis Prevention Treatment
Cause
Specific Signs/symptoms
Epidemiology
Characteristics: most common and important species of the family Enterobacteriaceae to cause human disease
• Can cause intestinal and extraintestinal disease:
– Intestinal disease → exogenous source via feces-contaminated food or water (diarrheal disease)
Pathogenesis
Diagnosis
Prevention
Treatment
ETEC
Pathogenesis
Diagnosis
Treatment
Pathogenesis: • Stable toxin (STa)heat stable
– Small peptide
– Binds guanylin receptor –> converts GTP to cGMP –> hypersecretion of electrolytes and water
• Labile toxin (LT); heat-labile
– A:5B toxin, mechanism very similar to that of cholera toxin
Diagnosis: not usually confirmed
Prevention
– Counseling regarding “safe” foods/drinks during foreign travel
– Prophylaxis with bismuth subsalicylate
Treatment
– Antibiotics can shorten duration, but some can cause more severe adverse events
– Antimotility agents can reduce symptoms •
