ZOONOSES
Over FOODBORNE 250 diseases can be caused by contaminated food or drink most are bacterial (Salmonella and Campylobacter) or caused by Norwalk virus most cases are single cases, not associated with a recognized foodborne outbreak majority of food items are raw or undercooked products of animal origin (meat, dairy, poulty, seafood) ~ 500 outbreaks reported each year
FOODBORNE ZOONOSES
Foodborne illness a substantial problem in US
6.5 to 33 milliion cases annually ~9000 deaths
Since 1986, of ~3200 outbreaks reported, only 21 were associated with contaminated produce Reporting of food and waterborne diseases began over 50 years ago as investigations of enteric fevers
FOODBORNE ZOONOSES
FOODBORNE ZOONOSES
Major virulence determinants: toxins destroy, damage, inactivate natural defense mechanism of host enzymes assist bacteria in establishing infection and producing disease
exotoxins endotoxins
FOODBORNE ZOONOSES
Toxins exotoxins
secreted from cell or leak out after cell death soluble protein, thus readily carried through body by lymphatics or blood damage at distant site, usually specific normally destroyed by heating to 100 C., although some are resistant to boiling (S. aureus) nonpyrogenic example: botulinism toxin, Staphylococcus aureus
FOODBORNE ZOONOSES
Toxins endotoxins
produced only by gram negative bacteria part of the outer cell wall (lipopolysaccharide coat)
lipid A component is toxic side chains (O, H antigen) are immunogenic
released in large amounts at cell death heat stable, not destroyed by autoclaving less potent and less specific than exotoxins
FOODBORNE ZOONOSES
Toxins endotoxins
pyrogenic toxic to most animals, producing similar range of biological effects regardless of source
fever increased WBC DIC (disseminate intravascular coagulopathy) hypotension shock death
degraded by oxidizing agents examples: E. coli, Salmonella, Shigella
FOODBORNE ZOONOSES
Enzymes spreading factors
hyaluronidase (gram +) attacks interstitial cement of connective tissue collagenase (Clostridium) break down collagen, facilitating invasion of muscle and gas gangrene formation neuraminidase (Vibrio and Shigella) break down intercellular cement of intestinal epithelial cells kinase (Strep and Staph) digests fibrin, preventing clotting and allowing rapid diffusion
FOODBORNE ZOONOSES
Enzymes cell lysis
coagulase (Staph) causes clotting adenylate cyclase activity bacterial toxins having immediate (shortrange) effects that promote invasion
Ex: anthrax toxin edema factor
hemolysins (Staph, Strep, and Clostridia) lecithinases (C. perfringens) phospholipases (C. perfringens) toxin
FOODBORNE ZOONOSES
New challenges newly identified pathogens (emerging pathogens) newly identified vehicles of transmission changes in food production changes in food distribution decline in food safety awareness
FOODBORNE ZOONOSES
Reasons for emergence or reemergence changes in pathogen centralized and concentrated production globalization of food supply increase in "at risk" populations changes in food animal practices changes in type and volume of foods imported
now import over 30 billion tons of food annually change in dietary preferences and exposure has led to many more types of produce being introduced
FOODBORNE ZOONOSES
Surveillance programs Foodborne Disease Active Surveillance Network (FoodNet) by CDCEIP
collaboration with USDA, FDA to determine incidence of foodborne illness in US established in 7 locations:
California (selected counties) Connecticut (selected counties) Georgia (selected counties) Minnesota (entire state) Oregon (entire state) New York (selected counties) Maryland (selected counties)
FOODBORNE ZOONOSES
Surveillance programs FoodNet (continued)
to document effectiveness of Hazard Analysis and Critical Control Points Rule (HACCP) active surveillance
population survey physician survey casecontrol study of E. coli O157:H7
FOODBORNE ZOONOSES
Surveillance programs Antimicrobial resistance surveillance PulseNet network set up for molecular subtyping
Basic research at NIH
pulsedfield gel electrophoresis method for E. coli O157:H7 now available in 24 state laboratories, along with USDA and FDA rapid comparison of PFGE profiles with database at CDC already been critical in outbreak investigation in Colorado associated with ground beef and multistate investigation traced to alfalfa sprouts
FOODBORNE ZOONOSES
Surveillance programs EnterNet (formerly SalmNet)
European Commission funded Established for surveillance for Salmonella and E. coli infections Includes 15 European countries has already let to public health interventions and product recalls in Europe
FOODBORNE ZOONOSES
Escherichia coli O157:H7 Campylobacter spp. (jejuni; fetus ssp. fetus) Listeria monocytogenes Salmonella spp. (Enteriditis; Typhimurium) Yersinia enterocolitica; Y pseudotuberculosis
Escherichia coli
gramnegative rodshaped bacteria hundreds of strains most strains are harmless, normal intestinal flora of healthy humans and animals occurrence: ubiquitous, worldwide distribution
Categories of Escherichia coli causing diarrhea
enterohemorrhagic (EHEC hemorrhagic colitis; O157:H7) enterotoxigenic (ETEC traveler's diarrhea) enteroinvasive (EIEC dysenterylike) enteropathogenic (EPEC infant diarrhea) enteroaggregative (infant d. in underdeveloped countries) diffuseadherence (pediatric diarrhea)
Escherichia coli O157:H7
first recognized in 1982 outbreak of hemorrhagic diarrhea traced to hamburgers (fast food chain) estimated 10,000 to 20,000 cases/yr in the US outbreaks have been associated with other foods such as leaf lettuce, cider, contaminated water more commonly isolated than Shigella
Escherichia coli O157:H7
"O" and "H" designation refer to cell surface antigen markers that are used to distinguish serotypes Other serotypes of enterohemorrhagic strains may also be implicated (O26:H11; O111:H8; O104:H21)
Escherichia coli O157:H7
syndrome caused by potent cytotoxins: verotoxins 1 and 2 (Shigalike toxins I and II because resemble toxins of Shigella dysenteriae) may also produce hemolyticuremic syndrome although recognized and intensively studied for 15 years, still do not know best method of treatment nor how animals become infected
Escherichia coli O157:H7
Microbiological features and identification
most enterohemorrhagic (EHEC) strains of E. coli do not ferment sorbitol (MacConkeysorbitol media used for screening O157:H7) presence of Shigalike toxins serotyping (phage typing)
Escherichia coli O157:H7
Microbiological features and identification
identification of toxin genes by DNA probes presence of virulence plasmid (plasmid allows expression of a fimbria, attachment to the intestinal mucosa) does not grow well or at all at 4445C
Escherichia coli O157:H7
Epidemiological features Reservoir:
cattle especially young dairy cattle wild ruminants deer (?) humans
Escherichia coli O157:H7
Epidemiological features Transmission:
ingestion of contaminated foods
usually inadequately cooked beef (especially ground beef) raw milk other foods by crosscontaminationlettuce, apple cider, apple juice
personperson (families, child care facilities, institutions) waterborne (swimming in crowded areas, drinking water)
Escherichia coli O157:H7
Epidemiological features Incubation period:
relatively long, ranging from 38 days
Period of communicability:
<1 week in adults may be up to three weeks in children prolonged carriers uncommon
Escherichia coli O157:H7
Epidemiological features Susceptibility and resistance
very low infectious dose oldage appears to be a risk factor children < 5 years of age are at greatest risk of developing hemolyticuremic syndrome
Escherichia coli O157:H7
Epidemiological features Occurrence
important cause of foodborne disease in US, UK, Europe, Japan, South Africa, southern regions of South America, Australia importance in underdeveloped regions and rest of world not established
Escherichia coli O157:H7
Clinical features diarrhea ranging from mild, nonbloody to virtually straight bloody stool, abdominal cramping fever is infrequent
Escherichia coli O157:H7
Clinical features Hemolyticuremia syndrome
more common in children may occur in up to 10% of cases characterized by:
hemolytic anemia thrombocytopenia renal failure (common cause of renal failure in children)
Escherichia coli O157:H7
Clinical features Thrombotic thrombocytopenic purpura (TTP) in elderly Case fatality rate: 35% (up to 50% in elderly with TTP)
Escherichia coli O157:H7
Control methods Preventive measures to reduce incidence
slaughterhouse management to minimize contamination of meat by intestinal contents pasteurization of milk and dairy products irradiate beef, especially ground beef
Escherichia coli O157:H7
Control methods preventive measures to reduce incidence
adequately cook meat to a temp of 155F (68C)
protect, purify, chlorinate public water supplies for drinking chlorination of swimming pools adequate hygiene in daycare facilities
`pink all gone' does not mean necessarily safe cooking with meat thermometer is recommended
Escherichia coli O157:H7
Control methods control of patient and immediate environment
report to health department (mandatory in many states) isolation: because of extremely small infective dose, patients should not be allowed to handle food or provide child/patient care until 2 negative samples are obtained disinfection contacts with diarrhea should be handled as if infected (no food handling, no patient care or child contact) until two negative fecal samples are obtained
Escherichia coli O157:H7
treatment Control methods
fluid/electrolyte replacement antibiotic treatment uncertain; TMPSMX may lead to hemolyticuremia syndrome
Campylobacter enteritis
Background Significant cause of enteritis worldwide and of traveler's diarrhea in U.S. Leading cause of bacterial diarrhea in U.S. Campylobacter 45% Salmonella 30% Shigella 17% E.coli O157:H7 5% Most common isolate: C. jejuni (C. fetus ssp. jejuni)
Campylobacter enteritis
Microbiology Campylobacter jejuni; C. colio, C. fetus ssp. fetus, C. spp. many biotypes and serotypes occur; useful in epidemiology gramnegative, microaerophillic, motile rods distinct shape of organism, flagella useful in identification require special environmental conditions for optimal growth 5% O2 relatively fragile, sensitive to stresses such as oxygen, drying, heat, acidic conditions prefers relatively high concentration of CO2
Campylobacter enteritis
Microbiology
Gram stain from culture media
(Note slender, curved rods)
Campylobacter enteritis
Clinical features
watery diarrhea, sometimes with blood (occult) normally selflimiting, not requiring treatment most common in children (<5 yrs) and young adults (1529 yrs of age) low fatality rateusually in immunocompromised infective dose small (~500 organisms in some cases) toxin production may cause diarrhea
Campylobacter enteritis
Epidemiology
Occurrence: estimated 2 4,000,000 cases/yr in US, probably more
Reservoir: poultry and cattle primarily; also pets, swine, and other species common contaminant of raw poultry (20100% at retail) can exist in intestinal tract of people and animals without causing symptoms present in high numbers in stools of infected symptomatic individuals
Campylobacter enteritis
Epidemiology
Mode of transmission: vehicles: undercooked meat contaminated food and water raw milk direct contact: pets, farm animals, infected infants personperson uncommon
Campylobacter enteritis
Prevention and control
On the farm: good sanitary practices (USDA guidelines) In the plant: HACCP1 to minimize opportunity for spread At retail: recall policy on readytoeat meat and poultry products found to be contaminated enforced by USDA (similar for E. coli O157:H7) Consumer: proper food handling procedures in kitchen
1
HACCP = Hazard Analysis and Critical Control Point
Campylobacter enteritis
Prevention and control
CDC report: 80% of US outbreaks due to Campylobacter could be prevented with universal pasteurization of milk and proper treatment of drinking water improved handling of chicken important bacteria destroyed when meat/poultry reach internal temperature of 160 F freezing not reliable method for destroying organism but thorough cooking will render product safe
Campylobacter enteritis
Outbreaks
Usually outbreaks are small (< 50 individuals) Vermont: 2,000 people ill from temporary use of non chlorinated water supply 1986 outbreak in school children traced back to milk which was being pasteurized for 135 F for 25 minutes rather than the required 145 F for 30 minutes (LTLT) Note: 161 F for 15 seconds (HTST) 280 F for 2 seconds (ultrapasteurized)
SALMONELLOSIS
Causative organisms: primarily S. enteriditis, typhimurium in U.S. numerous serotypes, many are pathogenic to both animals and man of the ~2,000 serotypes known, only ~200 recognized in the U.S. discovered in 1880, genus named for American scientist Salmon in honor of his extensive work
SALMONELLOSIS
Microbiological features and identification
gramnegative rodshaped bacteria motile (nonmotile forms are S. gallinarium, pullorum) heat labile growth prevented at <7 C for most serotypes nonspore forming, but can survive for long periods in foods and other substrates can survive for long periods in foods with low aw (water activity) such as chocolate, peanut butter, black pepper)
SALMONELLOSIS
Epidemiology reservoir
ubiquitous found in a wide range of animals, particularly poultry, swine, cattle, pets (iguanas, turtles, terrapins, tortoises, chicks, dogs, cats), humans chronic carriers common in animals and birds, less so in humans S. enteriditis infects ovaries of healthy appearing hens, thereby contaminating eggs in oviduct before shell is formed
SALMONELLOSIS
Epidemiology reservoir
S. typhi, paratyphi man only S. typhimurium particularly animals, food animals S. enteriditis animals, particularly food animals S. dublin cattle S. choleraesuis swine S. gallinarum, pullorum poultry S. arizonae animals, reptiles
SALMONELLOSIS
Epidemiology mode of transmission ingestion of raw, undercooked, or contaminated food
meat, milk, eggs, produce
fecaloral transmission
contact with pets (especially infants) foods contaminated by infected food handler
outbreaks usually traced to food items
SALMONELLOSIS
Epidemiology disease frequency incidence highest in infants and young children estimated 5 million cases annually (US)
up to 80% are sporadic cases large outbreaks in hospitals, restaurants, institutions are common
largest outbreak in US (25,000 cases) resulted from a nonchlorinated municipal water supply
SALMONELLOSIS
Epidemiology disease frequency proportion of reported cases due to S. enteriditis has increased from 5% in 1976 to 26% in 1994 report in J of Infectious Diseases (1994) 82% of outbreaks due to S. enteriditis between 19851991 were traced to contaminated shell eggs
SALMONELLOSIS
Epidemiology disease frequency case fatality rate
<1% for most forms of salmonellosis 15% with S. dublin reported in elderly up to 4% with S. enteriditis (nursing homes, hospital associated outbreaks with most being elderly)
SALMONELLOSIS
Selected outbreaks in US 1985 16,000 cases in 6 states
low fat and whole milk from a Chicago dairy pasteurization process changed, resulting in contamination of pasteurized milk with raw milk persons on antibiotic therapy more likely to be affected
1984 ~2700 passengers affected on 29 flights
caused by S. enteriditis strongly associated with food in First Class section only
SALMONELLOSIS
Clinical features
generally, salmonellosis is a milder disease than typhoid/paratyphoid acute disease nausea, vomiting, cramping, diarrhea, fever, headache more severe, even lifethreatening disease can occur in infants, elderly, immunocompromised
SALMONELLOSIS
Clinical features
chronic disease
small percentage of cases develop Reiter's syndrome arthritic pain, irritation of eyes, painful urination can last for months to years, leading to chronic arthritis refractive to treatment antibiotic therapy does not seem to prevent development of this serious sequela to acute salmonella infection
SALMONELLOSIS
Clinical features
incubation period: variable 12 to 72 hours illness generally lasts 47 days disease is caused by penetration and passage of organisms from gut lumen into epithelium; enterotoxin production (?) infective dose:
as few as 1520 cells depending on strain (4 serotypes ingested in vehicles that buffer gastric acids) normally >1023
SALMONELLOSIS
Diagnosis
serological identification of culture isolated from stool
Food analysis
developed for many foods conventional methods 5 days for presumptive results rapid methods require only 2 days
SALMONELLOSIS
Prevention and control FDA: `farmtotable' actions to reduce food safety risks associated with shell eggs
farm slaughter processing retail consumer
1 in 20,000 eggs produced annually contain S. enteriditis
SALMONELLOSIS
Prevention and control
FDA/FSIS pending proposals
38 states require refrigeration at retail level voluntary quality assurance programs for egg producers cleaning/disinfecting hen houses rodent control proper egg washing refrigeration between transport and storage biosecurity measures monitoring chick mortality use of SE free chicks and pullets
SALMONELLOSIS
Control
processing control of factors such as pH, moisture, presence of preservatives should me assessed at all stages using systematic approach (HACCP)through transit, storage, foodservice, and retail levels storage at low temperatures most serotypes fail to grow below 7C retail
handwashing avoid food preparation by workers with diarrhea thoroughly cook all poulty, pork, meat, egg dishes strict sanitation practices in kitchen, including rodent and insect control
SALMONELLOSIS
Control
consumer control
FDA Recommendations
recognize risk in pets (chicks, ducklings, and reptiles)not recommended for small children
avoid consumption of raw eggs avoid crosscontamination clean utensils, disinfect surfaces, proper hygiene, separate cutting surfaces for raw and cooked meats and vegetables thoroughly cooking meat, poultry, eggs (71C) do not freeze eggs in shell store cooked eggs in refrigerator, discard after 1 week
LISTERIOSIS
Causative organism: Listeria monocytogenes common inhabitant of intestine, soil, silage, other environmental sources most are pathogenic to some degree not recognized as a foodborne pathogen until the 1980's
Listeria monocytogenes
Microbiological features and identification grampositive rodshaped motile, flagellated non sporeforming will grow at pH 4.4 9.6 will grow in high salt concentrations (>10%)
Listeria monocytogenes
Microbiological features and identification resistant to heat, freezing, drying able to grow at temperatures as high as 50C and as low as 3C (psychotrophic able to grow at refrigerator temperatures) freezing has little detrimental effect on the organism
Listeria monocytogenes
Microbiological features and identification aerobic, microaerophillic growth on simple media (blood, trypticase soy agar) or selective media (McBride's agar) coldenrichment techniques too time consuming once recognized as a food pathogen now have faster methods FDA (dairy products); USDA (meat products)
Listeria monocytogenes
Epidemiological features Reservoir ubiquitous primary reservoir is soil, silage, environment also present in intestinal tract of animals and humans; asymptomatic carriers common (up to 10%) seasonal use of silage followed by increase in number of listeriosis cases in livestock
Listeria monocytogenes
Epidemiological features Susceptibility and resistance fetuses, newborns are highly susceptible older aged, immunocompromised individuals acquired immunity unlikely
Listeria monocytogenes
Epidemiological features Mode of transmission foodborne outbreaks associated with ingestion of raw or contaminated food milk (raw and supposedly pasteurized), cheeses (particularly softripened), ice cream, raw vegetables, fermented raw meat sausage, raw and cooked poultry, raw meat, raw and smoked fish
Listeria monocytogenes
Epidemiological features Mode of transmission direct contact neonatal transmitted in utero during passage through infected birth canal contaminated equipment in nurseries
Listeria monocytogenes
Epidemiological features Frequency of disease in US ~1,850 cases annually case fatality rate: 425 deaths annually 30% in newborn infants up to 50% when onset within first 4 days nonpregnant recent epidemic 35% (63% in >60 yrs of age)
Listeria monocytogenes
Epidemiological features Risk factors pregnancy (20 times more likely to get listeriosis); 33% of cases occur during pregnancy newborns more likely to suffer serious effects immunocompromised (AIDS, CA, diabetes, renal disease, elderly)
Listeria monocytogenes
Epidemiological features
source of infection in selected outbreaks Maritime Provinces (Canada) coleslaw made from cabbage fertilized with sheep manure; 28% CFR California (1985) Mexicanstyle cheese, numerous stillbirths; 142 cases, 33% CFR; FDA now monitors all domestic and imported cheeses many cases are sporadic, now thought to be foodborne, associated with soft cheese (Brie, Camembert, etc.) jellied pork tongue cause of 279 cases, 63 deaths, 22 abortions in France in 1992
Listeria monocytogenes
Clinical features
Target population pregnant women/fetus Cancer patients immunocompromised (AIDS, steroid therapy, graft suppression therapy) elderly healthy individuals low risk antacids and H2 blockers may predispose to infection outbreak among healthy individuals in Switzerland involving heavily contaminated cheese
Listeria monocytogenes
Clinical features
incubation period: variable 3 to 70 days signs and symptoms:
onset time varies: few days to 3 weeks in serious disease, > 12 hours in more mild forms
flulike symptoms septicemia meningitis or meningoencephalitis encephalitis intrauterine or cervical infections spontaneous abortion (2nd or 3rd trimester) gastrointestinal symptoms (nausea, vomiting, diarrhea)
Listeria monocytogenes
Clinical feat...