| Salmonella enterica | - 2500 serotypes
- g- rods, facultative anaerobe
- growth at 5-46 C, optimum 35-37 C
- sensitive to low pH (<4.5)
- no growth at aw <= 0.94
- habitat: gastrointestinal tract of domestic and wild animals, birds, reptiles, insects; humans can be carriers |
| Salmonellosis: basics | - Salmonella invade and multiply in epithelial cells
- produce enterotoxin, inflammation and fluid accumulation
- infective dose = 10^5-10^6 cells (depending on serotype)
- incubation period 8-24h, generally 12-72h
- carrier state in humans |
| Salmonellosis: symptoms | abdominal cramps, diarrhea, nausea, vomiting, chills, fever prostration |
| Salmonellosis: food vehicles | foods contaminated with fecal matter and eaten raw, improperly cooked, contaminated after proper heat treatment
- beef
- chicken
- turkey
- pork
- eggs
- milk
- contaminated fresh produce |
| Salmonellosis: control measures | - Salmonella surveillance program in food processing plants
- Salmonella control program on poultry farms
- consumer education on Salmonella control
- proper sanitation of food contact surfaces
- good personal hygiene practices |
| Campylobacter jejuni | - causes Campylobacteriosis
- gram -, microaerophilic (5% O2, 10% CO2, 85% N2)
- spirally curved rods
- temp range: 32-45 C, optimum 42 C
- sensitive to atmospheric O2, NaCl > 2.5%, low pH (<5), heat, drying
- live in intestinal tract of animals and birds, >10^6 cells/g poultry feces |
| Campylobacteriosis | - enterotoxin cross reacts with cholera toxin, produces invasive factor
- toxin production trait is plasmid linked
- infective dose as low as 500 cells
- incubation period is 2-5 days
- carrier state in humans
- raw animal products contaminated with fecal material from animals or infected humans
- typical cause is consumption of raw milk and undercooked poultry meats |
| Campylobacteriosis: symptoms | abdominal cramps, profuse diarrhea, nausea, vomiting, fever, headache, chills |
| Campylobacteriosis: control protocol | - proper sanitation of food contact surfaces
- adequate heat treatment of foods
- prevention of post-heat contamination
- good personal hygiene
- no ill food handlers |
| Listeria monocytogenes | - causes Listeriosis
- g+, facultative, small motile rod, hemolytic
- an grow 1-44 C, optimum 35-37 C
- resistant to freezing, drying, high NaCl, pH 5>
- can invade monocytes
- present in soil, water, sewage, dead vegetation, silage
- can persist for years in food processing & storage environment |
| Listeriosis | - invades body tissues, multiply and release toxins
- incubation period 1-7 days
- mild flu-like symptoms, slight fever, abdominal cramps, diarrhea
- pathogen can cross placental barrier and infect fetus
- outbreaks linked to coleslaw, raw milk, pasteurized milk, soft cheeses, turkey franks, cold-cut meats, undercooked chicken |
| Four groups of pathogenic E. coli | PITH
Enteropathogenic E. coli (EPEC)
Enteroinvasive E. coli (EIEC)
Enterotoxigenic E. coli (ETEC)
Enterohemmorhagic E. coli (EHEC) |
| Enteropathogenic E. coli (EPEC) | - infant diarrhea world wide
- infective dose 10^6 to 10^9 cells
- disrupt intestinal villi --> fluid accumulation |
| Enterotoxigenic E. coli (ETEC) | - traveler's diarrhea and infant diarrhea
- poor sanitation in many developing countries
- infective dose: 10^8 - 10^9 cells |
| Enteroinvasive E. coli (EIEC) | - dysentery-like shigellosis, mucus and blood in feces of infected person
- infective dose: 10^6 cells
- invasive factor; E. coli O124:B17
- invades the intestinal epithelium |
| Enterohemmorhagic E. coli (EHEC) | - bloody diarrhea
- hemolytic uremic syndrome
- principal serotype: E. coli O157:H7, g- rod, fac. anaerobe, sorbitol negative
- low infectious dose (<50 cells)
- highly virulent
- rapid growth 30-42 C, none <10
- acid tolerant
- found in intestinal tract of animals, particularly dairy cattle
- produces verotxin
- colonization of intestines and toxin production |
| Enterohemmorhagic E. coli (EHEC) food-borne infection | diseases: hemorrhagic colitis, hemolytic uremic syndrome, thrombotic thrombocytopenic pupura
- 3-9 day incubation period
- colitis symptoms: abdominal cramps, bloody diarrhea, vomiting, fever in some instances, bleeding from intestinal damage
- food vehicles: foods of animal origin, especially ground beef, poultry, lamb, raw milk |
| Enterohemmorhagic E. coli (EHEC) control | - eliminate corn from diet of cattle a few weeks prior to slaughter to reduce shedding
- proper hygiene to prevent fecal-oral transmission
- proper sanitation of food contact surfaces
- cooking/heating foods at appropriate temperatures
- proper refrigeration
- prevention of cross contamination |
| Vibrio parahaemolyticus | - causes Gastroenteritis
- g-, motile, curved rods
- grows 5-42 C, optimum 30-37 C
- growth in 3-5% NaCl, sensitive to 10% NaCl
- growth inhibited at pH <5
- 10-24h incubation period
- sensitive to drying, heating, refrigeration, freezing
- halophilic organsim; found in estuarine waters
- pathogenic strains (Kanagawa +) produce heat-stable hemolysin |
| Gastroenteritisis | - infective dose of Vibrio parahaemolyticus: 10^5-10^7 cells
- symptoms: nausea, vomiting, abdominal cramps, diarrhea fever, chills
- from various improperly cooked/post-heat contaminated seafood from estuarine waters |
| Gastroenteritits control | - avoid eating raw seafood
- proper heat treatment of seafood
- proper sanitation to avoid cross-contamination of cooked seafood
- proper refrigeration of raw and heated products
- avoid temperature abuse of seafood |
| Shigellosis causing species | Shigella dysenteriae, S. flexneri, S. bodyii, S. sonnei
- all 4 species are pathogenic
- S. dysenteriae is the main pathogen that causes bacillary dysentery |
| Shigella dysenteriae | - highly virulent: infection in susceptible persons caused by as few as 10 cfu
- found in gastrointestinal tract of humans/other primates
- growth temp: 10-48 C
- pH: 6-8 |
