Food Micro: Foodborne Disease
The CDC estimates that ___________ cases of Staphylococcus gastroenteritis occur each year in the US.
1 - 2 million cases.
How long until a person starts to experience symptoms of ingesting the live bacteria of Shigella?
1 day to 1 week. Symptoms range from mild diarrhea to severe dysentery characterized by the passage of frequent bloody mucoid small-volume stools, fever, vomiting & dehydration.
When would a person start to experience symptoms of Listeria food poisoning?
1-5 weeks after ingestion of live bacteria.
10% of what molecule promotes growth in C. jejuni?
10% CO2
How many Listeria cells are killed during milk pasteurization?
10^5 to 10^6 cells
What is the process that is needed to eliminate spores in canned foods? What two reasons give this process such efficiency?
12 D processing kills 10^12 spores/gram. Reasons: 1.) High temperature 150 C or 250 F 2.) 1 atmospheric pressure
How long do symptoms of Salmonella poisoning usually last?
2-3 days & is accompanied by weakness, drowsiness & a moderate fever.
How long will symptoms of shigella last?
4-7 days.
When abortions are included in the mortality rate, the death rate from listeriosis during the 1980s ranged from what to the UK and what in the US?
50% in the United Kingdom to about 28% in the U.S.
How much sucrose caused inhibition of clostridia?
50% sucrose
How many nano grams of toxin A from clostrida is considered lethal?
70 ng.
Studies have found that 94% of eviscerated _______ and 72-80% of ___________ were positive for C. jejuni.
94% of turkeys. 72-80% of chicken carcasses.
What is the range of avirulent to virulent for Shigella?
<34 Celsius = avirulent & cannot invade the mucosa. >34 Celsius = virulent
What is the pH range for High Acid canned foods? What type of foods are considered High Acid?
<4.0 pH Fruits, a few veggies, & fermented products like sauerkraut.
Around what pH level does the botulism toxin not grow at?
<4.5 pH, which is a feature that determines heat processing requirements in canned foods.
Botulism is caused by the ingestion of what?
A heat-labile neurotoxin produced (most frequently) by C. botulinum. This is a pre-endoform toxin. This makes Clostridium a foodborne intoxication!
What is the treatment of adult botulism?
Adults requires administration of specific antisera as quickly as possible since binding to ganglioside is irreversible.
Which types of clostridium are proteolytic strains and non-proteolytic strains?
All known type A strains are proteolytic. All type E strains are nonproteolytic. Types B & F both proteolytic & non-proteolytic.
What is the treatment for a L. monocytogenes infection?
Antibiotic therapy. This treatment is often not as effective as desired because victims are frequently immunocompromised to begin with.
L. monocytogenes is recovered from patients around the U.S relatively frequently. What is the overall rate of bacteremia or meningitis due to L. monocytogenes in the US?
Around 1,850 cases per year.
What is by far the most commonly identified cause of foodborne disease?
Bacteria
Microbial groups able to cause foodborne illness in humans includes which microorganisms?
Bacteria Fungi Virus Algae Eukaryotic parasites
Is food poisoning from Staph a foodborne infection or foodborne intoxication?
Because pathogenesis results from the ingestion of one or more pre-formed enterotoxins, it's a foodborne intoxication.
Why is listeriosis in humans not characterized by a unique set of symptoms?
Because the course of listeriosis depends on the host's fitness. Healthy, nonpregnant people are highly resistant, and evidence suggests that consumption of 10^4 to 10^5 CFU/g may not cause disease.
What is the treatment for staphylococcal food poisoning?
Bed rest Fluid replacement
What are the most common reasons for outbreaks of Shigella?
Contaminated water or food handlers with poor hygiene (fecal/oral route).
How does the bacterium of C. perfringens or it's toxin get into the food of meats?
Directly from slaughtered animals or from contamination by containers, food handlers, or dust.
What are the two groups of bacterial toxins?
Exotoxins Endotoxins
What type of spoilage does Acid canned foods undego?
Flat-sour spoilage. Stays flat May smell Tastes sour due to pH lowering
Other than foodborne illness caused by microorganisms, what causes it?
Food idiosyncrasy. (allergic reactions) Chemical food poisoning. (toxins added or natural) Difficulty in digesting (GI distress)
What is the definition of a foodborne infection?
Foodborne infections occur when a LIVE organism is consumed & no symptoms usually appear until the organism can localize & target an organ or organ system & grow. This is the incubation period.
What is the definition of a foodborne intoxications?
Foodborne intoxication occur when food that's consumed contains PRE-FORMED TOXINS produced by microorganisms during growth in the food. Symptoms usually occur relatively QUICKLY after eating the toxin.
Do foodborne infections or intoxications present symptoms more quickly to the individual who consumed the contaminated food?
Foodborne intoxications symptoms usually occur relatively quickly after eating the toxin. Foodborne infections take a longer than intoxications because the live organism has to localize and target a specific organ or organ system before symptoms are presented.
What are the general intoxication symptoms of food poisoning from Staphylococcus? What part of the immune response is responsible for the majority of these symptoms?
General symptoms include nausea, vomiting, severe abdominal cramps, diarrhea, sweating, headache & sometimes a fall in body temperature. The overproduction of cytokines is believed to produce most of these intoxication symptoms.
What number of bacterial Salmonella cells does one need to ingest to feel symptoms?
Generally 10^5 - 10^9 CFU/gram, but can be as few as 15-20 cells. Much depends on the age & health of host, & strain differences among the members of the genus.
What is the morphology, class, and type of the microorganism Listeria?
Gram positive, aerobic or facultatively aerobic, non-spore forming rods.
What is the most common vehicle for Staphylococcus? Why?
HAM is the most common vehicle food for staph. This association is due to the high salt content (3.5%), which favors growth of S. aureus (which enter from food handlers or cutting surfaces) over other MO.
What are endotoxins?
Heat stable lipopolysaccharide components of the outer membrane on Gram negative bacteria (Lipid A). Released when the microbe dies. Very specific, very potent.
What is the very best way to control the growth of Salmonella?
Heat treatment of pasteurization temperatures, which is 161 F or 72 C for 15 seconds or by heating foods to an internal temperature of 165F 74 C. Salmonella are very heat sensitive bacteria, NOT HARDY.
Can host-adapted serovars of Salmonella effect humans? What are the serovars of host-adapted Salmonella?
Host-adapted strains are associated with a particular type of host but many can cause foodborne disease in humans. S. gallinarum (poultry) S. Dublin (cattle) S. abortus-equi (horses) S. abortus-ovis (sheep) S. choleraesuis (swine).
Is there any sign of immunity found in human from staph foodborne intoxication?
Humans do not demonstrate any immunity to repeated exposure.
What environment is type A, C. perfringens found?
In soils 10^3-10^4/g in virtually all samples examined. Water Dust Intestinal tract of humans & other animals.
What season does Campylobacter outbreaks more commonly happen?
Incidence of foodborne infection is seasonal, with higher numbers of outbreaks in the SUMMER and FALL. Most outbreaks are seen in people 10-29 years of age.
What are the symptoms of C. perfringens?
Incubation time is 6-24 h (esp. 8-12 h) after ingestion of 10^6 or more live cells. Acute abdominal pain & diarrhea. Nausea, fever & vomiting are rare &, unless the victim is immunocompromised. Symptoms last <24 h. Mortality is low & has only been fatal to older or otherwise debilitated patients. No immunity seems to develop.
What positive effects to endotoxins produce in their hosts?
Interestingly, when endotoxins are administered in sublethal levels, they can confer enhanced resistance to bacterial infections.
What is the habitat of Salmonella species?
Intestinal tract of birds, mammals, and reptiles.
Which organs in the body are colonized by Listeria?
Intestinal tract then moves to the bloodstream where it invades other susceptible tissues including the spleen, liver and the *placenta.
Is it easy or difficult to isolate C. jejuni from suspected contaminated food?
Isolation of C. jejuni from suspect food is rare because the bacteria are usually present in very low numbers, but the organism is isolated more frequently from fecal/oral samples of humans with diarrhea (3-14%) than Salmonella and Shigella.
What does it mean that Campylobacter is microaerophilic?
It's relatively hard to grow.
What common route of infection do all Salmonella species go thru?
Live Salmonella cells which have been consumed penetrate the intestinal epithelium of bird, mammal or reptile. The cells multiply within membrane bound vacuoles & then lyse these vacuoles & disseminate to other parts of the body.
Do Campylobacter infections commonly need antibiotics? Or is it easily treated?
Most infections are self-limiting & are NOT treated with antibiotics. One death per 1,000 cases occur. Fatalities are rare in healthy individuals & usually occur in cancer patients or in the otherwise debilitated (very young & old, AIDS, etc.).
What is the MOST IMPORTANT sources of staph to food?
NASAL CARRIERS & PERSONS WITH BOILS OR CARBUNCLES that are allowed to handle foods. Is also found in domesticated animals nasal cavities too.
What are the symptoms of botulism?
Nausea, vomiting, fatigue, dizziness, headache, dry skin, mouth, & throat, lack of fever, constipation, paralysis of muscles, double vision. Finally, respiratory failure & death.
Is Staphylococcus very well represented? Does it get reported often?
No & no. Staph isn't well represented because it's almost NEVER fatal & people usually recover from it so quickly.
Is botulism a good competitor to other microorganisms in the body?
No, Clostridia need complex nutritional requirements that generally competes very poor with other microorganisms.
Do all S. aureus produce enterotoxin?
No, not all S. aureus produce enterotoxin. 10-60% of S. do.
Does staph comete well with the normal flora of many foods? What about lactic acid bacteria?
No. Staph DOES NOT compete well with them, especially lactic acid bacteria.
What 3 organisms are usually responsible for spoilage of High Acid canned foods?
Nonsporeforming mesophiles like... Yeast Molds Lactic Acid Bacteria
Is C. jejuni found in healthy people in the US? Is it found in healthy animals in the US?
Not carried by healthy people in U.S. or Europe, but prevalence in feces from healthy animals is 30-100%.
Once the shigella species are ingested by a person, what does the microorganism do?
Once ingested, Shigella spp. invade the colonic mucosa, multiply & then destroy the epithelial layer of the colon as they lyse infected cells and spread.
What is the optimal growth for Salmonella?
Optimal growth at 37oC, growth of some serovars has been noted <6o up to 45oC
What is the optimal pH level of growth for Listeria?
Optimal pH range is 6-8, but can grow 4.1 - 9.6
What is the optimal temperature levels for Listeria growth?
Optimal temperature is 20-30 C But is able to still grow between 1 and 45 C.
Outbreaks of dysentery occur when what two things are combined?
Poor hygiene & overcrowding. i.e prisons, refugee camps, etc.
What route is the most common factor in foodborne shigellosis?
Poor personal hygiene through the fecal-oral route of transmission.
What is the most prominent vehicle foods in outbreaks of campylobacteriosis?
Poultry & raw milk.
How much oxygen does C. jejuni need for growth?
Requires 3-6% O2 but inhibited at 21% (atm. conc.)
What temperature optimal temperature S. aureus grows at? What is the optimal enterotoxin pH?
S. aureus can grow between 7 - 47.8 C with enterotoxin production between 10 - 46 C. Optimal toxin production between 40-45 C.
What is the most lethal strain of Salmonella? What is the mortality rate? Who is the most vulnerable, the young or old?
S. choleraesuis is most lethal strain with a mortality rate of 21% in people over 50.
S. flexneris, S. boydii, and S. sonnei cause foodborne shigellosis, what does the fourth shigella species cause?
S. dysentariae causes dysentery.
Which serovar of Salmonella is associated with eggs?
S. enteritidis. *Responsible for 70% of all Salmonella cases, and this organism is believed to cause more deaths than any other foodborne pathogen.
What are the sources of S. aureus & other species of staph?
Skin & intestinal tract of humans & animals. All food with animal origin. Nasal cavities of humans & other animals. Persons with boils or carbuncles.
A substantial percentage of sporadic cases of Listeria have been linked to the consumption of what foods?
Soft cheese Food purchased from store delicatessen counters. Undercooked chicken. Hot dogs which were not reheated.
L. monocytogenes can be recovered with what percent of soft cheeses, processed meats, raw meat including poultry, and veggies?
Soft cheese 20% Processed meats 20% Raw Meats w/ poultry 50% Vegetables 30%
Where is C. botulinum cells & spores are found where?
Soil, spores are in veggie products due to soil contamination. Dust Water
Which bacterial species is responsible for the number one cause of food poisoning?
Staphylococcus. Genus of G+ facultative anaerobic bacteria that includes several species.
How long until symptoms of botulism present themselves?
Symptoms appear between 12-72 hour after the ingestion of toxin-containing foods.
How long do staphylococcal food poisoning symptoms usually last?
Symptoms last 24-48 h and mortality is very low.
What is the pathogenesis of C. perfringens toxin?
The toxin binds irreversibly to the brush border of intestinal epithelial cells, where it moves into and damages the membrane. Water and salt uptake by infected cells is reversed and cell death results.
What is the most common vehicle foods involving infant botulism?
Those foods which do not undergo heat processing to destroy endospores such as honey & corn syrup are the most frequented sources. Diagnosis requires identification of botox in infant stools.
When do you usually start to feel the Salmonella poisoning symptoms?
Usually 12-14 hours after ingesting sufficient numbers of bacteria.
What is the mortality rate of botulism?
Varies between 30-65%.
About how many children deaths does Shigella cause each year?
Worldwide it causes about 500,000 children's deaths each year.
What is the average number of cases of C. perfringens outbreaks in the US?
~100 per year.
What 3 different types of spoilage can occur in Low Acid canned goods?
1. Flat-sour spoilage 2. Sulfide Spoilage 3. Gaseous spoilage.
What are the 3 classifications of canned goods?
1. Low Acid 2. Acid 3. High Acid
What are the five factors which are most commonly associated with Staphylococcal food poisoning outbreaks?
1. Poor personal hygiene. 2. Inadequate cooking or heating of food. 3. Preparing foods too far in advance. 4. Holding food in warmers set at bacterial growth temperatures. 5. Inadequate refrigeration.
Spoilage from the canned products can occur for 3 reasons, what are these reasons?
1. Pre-processing spoilage 2. Inadequate processing 3. Post-pocessing contamination
What are the 3 reasons foodborne illnesses are caused by bacteria?
1. Widespread distribution, they're everywhere. 2. Able to grow rapidly in favorable conditions. 3. Can easily be detected in food and feces.
About 50% of Campylobacter infections are associated with what two things?
1.) Inadequately cooked or recontaminated chicken meat. 2. Handling chickens.
How much NaCl is needed to inhibit clostridia?
10% NaClo
What percentage of NaCl can Staph grow in?
10-20% of NaCl. This includes all enterotoxin-producing species.
What is the optimal growth temperature of Shigella?
10-45 degrees Celsius
What concentration is needed to produce an immune response of staph's food poisoning?
200 nano grams of enterotoxin. 10^5 CFU/gram in food can produce more than enough toxin to make one ill.
Heat inactivation of 99% pure SEB in buffer required what temperature of heat, with what duration of time?
250 F at 16.5 minutes. Vegetative cells are destroyed long before toxin.
How many live Campylobacter bacteria are needed to be ingested for symptoms to present themselves? How long does it take for symptoms to appear?
400-500 live bacteria. Usually 2-4 days (up to 10 d) after ingestion.
What is the overall mortality rate of those infected with L. monocytogenes?
425 death per year or around 23%.
C. perfringens has how many different variants based on the type of exotoxin produced? Which variant causes the food poisoning?
5 variants, A thru E. Food poisoning cases are due to heat resistant type A, other types are associated with gas gangrene infection in wounds.
Botulism toxins are the most lethal substances known to mankind! A single milligram of type A toxin will kill how many mice?
A single milligram of type A toxin will kill 15 million mice.
What factors may predispose someone to listeriosis, & which are significant in the mortality rate?
AIDS Alcoholism Diabetes (exp. type 1) Cardiovascular disease Tumors Renal transplant patients People on steroid therapy Pregnancy
What is the biggest difference of pathogenisis of adult botulism & infant botulism?
Adult botulism occurs when a pre-formed neurtoxin is ingested. Infant botulism occurs when a LIVE ENDOSPORE TOXIN is ingested.
What percentage of adults & children harbor S. aureus in their noses?
Adults: 50% Children 55-60%
What is food idiosyncrasy?
Allergic reactions to food are involved which can be as mild as a skin rash or severe enough to cause death.
The known Salmonella serovars can be separated into 3 epidemiological groups. What are those 3 groups?
Although there are over 2500 salmonella serovars, the 3 distinct groups are... 1. Those that only infect humans. 2. Host-adapted serovars. 3. Unadapted serovars.
Are bacterial toxins involved with foodborne intoxications or infections?
Both! Bacterial toxins are involved in foodborne infections and intoxications.
What four Clostridium species cause food poisoning in humans?
C. botulinum (food processing) C. baratti (utah biomar) C. butyricum ( siledge in cow feed) C. perfringens (2nd most common cause of food poisoning.)
Studies have found that 94% of eviscerated turkeys and 72-80% of chicken carcasses were positive for what?
C. jejuni
Where is C. jejuni most commonly found?
C. jejuni are found in the intestinal & reproductive tracts of humans & other animals.
What temperature can C. jejuni not grow below?
C. jejuni cannot grow below 25oC or in the presence of 3.5% NaCl. It can remain viable, however, in vac. pkgd turkey for up to 28 d at 4oC.
In developed nations, Campylobacter causes about how many cases per year?
Campylobacter may cause as much enteric disease as Salmonella & Shigella combined with about 2-4 million cases per year in U.S.
The human body can absorb the neurtoxin of botulism through what parts of anatomy?
Can be absorbed into the bloodstream through the respiratory mucus membranes or thru the lining of the stomach.
What is chemical food poisoning?
Chemical food poisoning is caused by toxic substances, natural or added, in the food. Examples include; poisonous mushrooms or pesticide residues.
When cooking meat, how high must the temperature be, and for how long, to kill L. monocytogenes?
Cooking meat to an internal temp of 70oC (158oF) for 2 min kills L. monocytogenes.
What is by far the most common microbial agent for foodborne infections?
D. jejuni subsp. jejuni of Campylobacter. >99% of human cases.
What is characteristic of Sulfide-spoilage?
Done by anaerobic thermophilic sporeformers that produce H2S like Clostridium nigrificans & C. bifermentans. Blackening of foods May swell, may not. Very potent off odors.
What is characteristic of Gaseous spoilage?
Done by putrefactive anaerobes like C. butyricum. The can swells & the food may have a fermented. Cheesy or putrid odor.
What is characteristic of Flat-sour spoilage?
Done by thermophilic sporeformers such as Bacillus stearothermophilus (strick aerobe!) and B. coagulans (fac. anaerobe). The can does not bulge but stays flat pH falls & food tastes sour w/ off odors.
What are dystonias? And how is the botulinum toxin a useful therapeutic agent for dystonias?
Dystonias are disorders caused by involuntary sustained muscle contractions that result in twitching, repetitive & sometimes painful movements or abnormal postures. Botox is used to partially paralyze those muscles & relieve dystonia.
What are the most common vehicles of salmonellosis in humans?
Eggs (70% of all salmonella infections). Poultry (especially the outer layered skin). Meat & Meat Products (carcass contamination w/ fecal matter during slaughter).
Are eggs generally considered sterile?
Eggs are generally sterile and are contaminated by fecal material after they are laid, but chickens with infected oviducts may lay eggs that already have Salmonella enteritidis INSIDE THEM.
Are enterotoxins heat resistant or heat sensitive?
Enterotoxins are heat RESISTANT. This is an exception, because enterotoxins are a type of exotoxin, which is generally heat-sensative, but the staphylococcus enterotoxin is just super cool like that and resists the HEAT! :)
What are the 3 subgroups of the exotoxins?
Enterotoxins: stimulate gastrointestinal cells in an abnormal way. (e.g. cholera toxin) Cytotoxins: Kill host cells by enzymatic attack. (e.g. diphtheria toxin) Neurotoxins: Interfere with normal transmission of nerve impulses.. (e.g. botulinum toxin)
Does Listeria cause a foodborne infection or foodborne intoxication?
Foodborne INFECTION because a person consumes a LIVE bacteria of Listeria. No spores.
Is Shigella a foodborne infection or foodborne intoxication?
Foodborne infection Fecal/oral route at places like day care centers, elderly facilities, etc. Shigella are intracellular parasites of humans & higher primates
Is Campylobacter a foodborne infection or foodborne intoxication?
Foodborne infection because of the ingestion of live bacteria. EXCEPTION:Some, but not all, pathogenic strains have been shown to produce a heat-labile enterotoxin and a cytotoxin.
The types of foodborne illness that are caused by MO are separated into two classes; what are these two classes?
Foodborne infections Foodborne intoxications
How do most outbreaks of staphylococcal gastroenteritis occur?
From foods which were prepared by hand & then not refrigerated properly for several hours PRIOR to consumption.
In infant botulism, where do the viable ingested spores germinate in the infant's body?
Germinate in their intestinal tract and produce toxin inside the child. The disease can range from mild to severe, depending on how rapidly diagnosis is made.
Does glucose inhibit or enhance Listeria growth?
Glucose enhances growth of all Listeria species!
What is the best method of prevention of a shigella foodborne infection?
Good hygiene & proper preparation & handling of food in homes & food service establishments.
What is the best prevention methods for Campylobacter?
Good hygiene practices Proper preparation & handling of food by cooking thoroughly. Avoiding unprocessed foods associated with Campylobacter such as raw milk.
Even when food is contaminated, the food must be handled in a manner that gives the bacterium an opportunity to... what?
Grow and produce the enterotoxin.
Is growth in food necessary for Shigella's foodborne infection?
Growth in foods is NOT always necessary for infection, however, because as few as 10-100 CFU can initiate infection in susceptible people.
Like a few other pathogenic bacteria (Bordetella pertussis, Yersinia) virulence in Shigella is related to what?
Growth temperature.
What are the sources for Listeria?
Important sources of Listeria in foods are not clear. Sources may include healthy cattle that shed listeria into milk, or food handlers that are asymptomatic carriers.
In 1989, the industry-wide incidence of Salmonella in _________ was almost 50%.
In 1989, the industry-wide incidence of Salmonella in ANIMAL FEEDS was almost 50%. Animal feeds can be an important source of Salmonella
What measure is used in the US, but not in many developing countries, to prevent S. enteritidis infections?
In 1991, the U.S. Congress required that eggs for interstate shipment be refrigerated, and U.S. grocers typically store eggs in refrigerated bins. The latter practice is not followed in many other developed nations.
Is adult botulism or infant botulism slightly more common?
Infant botulism is a little more common.
What is the major Listeria pathogen that is most dangerous to humans?
L. monocytogenes is the pathogen of major concern to humans where 98% of recorded human outbreaks have involved this species. 3 known cases involved L. ivanovii, and 1 case involved L. seeligeri.
When susceptible people contract the disease, what types of infections are the MOST COMMON symptoms? Which disease may these symptoms resemble?
Meningitis and sepsis or blood infection are the most common symptoms to susceptible people. The disease may resemble the infectious mononucleosis.
Who is most at risk from dying or being seriously ill to Salmonella poisoning?
Mortality for serovars other than those causing typhoid and paratyphoid fevers varies with the serovar involved is greatest in people over 50 (15%) and in children under 1 (5.8%) with a 2% rate for ages in between.
What is the mortality rate of people infected with S. typhi & S. paratyphi A & C?
Mortality from typhoid and paratyphoid fever is about 10%. People can recover on their own with bed rest & fluid replacement, but more severe cases may require antibiotic therapy & monitoring of body fluid balance.
What are the symptoms of Salmonella poisoning?
Nausea, vomiting, moderate abdominal pain, headache, chills & diarrhea usually 12-14 h after ingesting sufficient numbers of bacteria which is 10^5-10^9 CFU/g, but can be as few as 15-20 cells; depending on the age & health of host, & strain differences among the members of the genus
Is adult botulism common in the U.S?
No! Total cases of adult botulism in the U.S. rarely exceed 50/yr, but the high mortality rate makes the disease an ongoing concern.
Is Campylobacter hardy?
No! It's not hardy :) Gram negative, microaerophilic to anaerobic spirally curved rods.
Outbreaks are often meat dishes or non-meat dishes contaminated by gravy, but what usually causes C. perfringens to contaminate the meat?
Outbreaks are often meat dishes (or non-meat dishes contaminated by gravy) that were prepared one day & eaten the next because the heat prep is usually inadequate to destroy spores. During the time between prep & consumption, spores germinate and cells grow.
What is the pathogenesis of botulinum?
Pathogenesis is due to the ingestion of C. botulinum neurotoxin, which makes it a foodborne intoxication because of the ingestion of a PRE-ENDOFORM TOXIN.
*What is the pathophysiology of L. monocytogenes? What does it produce and how does it negatively cause disease in a human?
Pathogenic strains of L. monocytogenes all produce listeriolysin O, a substance that produces β-hemolysis on erythrocytes & kills phagocytes that engulf the bacterium. Listeriolysin O is produced during exponential growth (max levels after 8-10 h of growth)
What are the unadapted-serovars of Salmonella?
Pathogenic to humans and animals, include most foodborne serovars. These serovars are named after the city/state/country they were first discovered in.
What is unique about Campylobacter's incubation time?
People infected may continue to shed the organism for more than 2 months after symptoms subside. Shedding usually occurs during the symptoms, but campylobacter also sheds during comulesent phase too.
Do Listeria infected woman show symptoms?
Pregnant women that contract listeriosis often show no symptoms or they may be feel they have a mild case of flu. Unfortunately, abortion, premature birth or stillbirth often occur. Newborns infected at birth show symptoms of meningitis 1-4 weeks after birth.
Which demographic is most susceptible to dying from a L. monocytogenes infection?
Pregnant women. The rate in pregnant women is much higher, 12 per 100,000 which is cause for real concern.
What negative effects to endotoxins produce in their unlucky host?
Produce fever, shock, diarrhea and sometimes internal hemorrhage or abortion in hosts.
What are the symptoms of a Campylobacter foodborne infection?
Profuse diarrhea (sometimes with blood), abdominal pain, malaise, headache & fever. Will last from 1-4 days, but relapses are not uncommon (about 25% of cases).
Are proteolytic strains of clostridia or non-proteolytic strains of clostridia more heat resistant?
Proteolytic strains are much MORE heat resistant than non-proteolytic strains Type A is the most heat resistant!
Do proteolytic strains or non-proteolytic strains of clostridia grow in refrigeration temperatures?
Proteolytic strains cannot grow at refrigeration temperatures range 10 - 50 C. Non-proteolytic strains can grow in frig temperatures 3.3 - 45 C.
Other than heat treatment, what other less-conventional method is used to inhibit Salmonella's bacterial growth?
Radiation. Salmonella are quite sensitive to radiation, which is a useful tool for removing the bacteria from animal feeds & from raw poultry. This method is recently gaining greater acceptance in the U.S.
The Salmonella serovars that only infect humans are what? Which distinct species is the most pathogenic?
S. typhi (most virulent to humans) S. paratyphi A & C These strains cause typhoid & paratyphoid fevers, which are the most severe diseases caused by salmonella.
What percentage of NaCl can Salmonella not tolerate to grow in?
Salmonella cannot tolerate 9% NaCl.
Is Salmonella food poisoning common in the US?
Salmonella food poisoning is one of the most common bacterial foodborne illnesses in the U.S with CDC estimating between 800,000 & 4 million cases each year. According to the last CDC 5-year survey, Salmonella was responsible for 69% of all cases of foodborne illness caused by bacteria.
What chemical compound & environment inhibits Salmonella bacteria?
Salmonella growth is inhibited by nitrite (N2) and if Aw <0.94.
What diseases are caused by Salmonella?
Salmonella, the gram negative facultative anaerobic bacteria can cause... Typhoid fever Septicemia Gastroenteritis
What are 3 examples of foodborne infections?
Salmonellosis Dysentery Cholera
What is a serovar?
Serotype or serovar is a distinct variation within a species of a microorganism.
What are prominent vehicle foods for Shigella?
Shellfish Fruits Vegetables Chicken Salads.
Which two microorganism species are closely related to Salmonella & E. coli?
Shigella
Different strains of Salmonella are classified by what structural characteristics?
Somatic O & flagellar H antigens O antigen = O polysaccharide chain H antigen = flagellum
Although large-scale outbreaks have attracted the greatest notoriety, what type of diseases continue to account for most cases & deaths from listeriosis in the US?
Sporadic disease.
What type of toxin is Staphylococcus able to produce that causes food poisoning?
Staph synthesizes heat-resistant enterotoxins that produce food poisoning.
What is the mechanism of the enterotoxin of staph that induces a immune response. Specifically, what does enterotoxin bind to? What particular molecule does the immune response produce to combat the toxins?
Staphylococcal enterotoxins bind to helper T-lymphocytes in a manner that stimulates production of several cytokines, especially interleukin-2.
What are 3 examples of foodborne intoxications?
Staphylococcal food poisoning Paparalytic shellfish poisoning Botulism
What can one do to prevent enterotoxins from staph being produced in food?
Store foods at 4 Celsius (40 F). Or store above 60 Celsius (140 F). This practice will help to keep many disease-causing MO out of your food.
What is the first symptom of infant botulism? What are the cascading symptoms after the first?
Symptoms start with CONSTIPATION, followed by poor feeding, lethargy, and weak or altered cry. Loss of head control is dramatic.
How long after the ingestion of the contaminated food does the intoxication symptoms of staph present to the host?
Symptoms usually appear within 4 hours, the average range is 1 - 6 hours.
How is Salmonella transmitted from it's origin source of replication to infecting a human?
The Salmonella bacteria are excreted in FECES & may be transmitted through polluted water or by insects & other creatures, including humans.
What is the GREATEST hazard of receiving C. botulinum?
The greatest hazard is home-prepared-canned-foods that are handled improperly or given inadequate heat treatment. Many of these foods are consumed without preheating.
How long will the illness from botulism last?
The illness may linger over 1-10 days.
Is the mortality low or high for shigella infections?
The mortality rate is low in the US, except for the severely immunocompromised, which has a 10-15% mortality rate, which is still relatively low.
Is the neurotoxin of clostridia heat sensitive or heat resistant?
The neurotoxin is very heat sensitive (labile).
What is Salmonella's optimal pH growth range?
The pH optimum is near neutral (6.6-8.2 ideal), but growth can occur from 4.05 to 9.0. Viability at pH values as low as 3.3 has been demonstrated in acid ADAPTED cells.
How are these toxins released in the body?
These toxins are formed inside the bacterium and are released by AUTOLYSIS.
Ultimate control of salmonella can only be achieved by eliminating the bacteria from animals and humans. Why is this difficult to do?
This objective is difficult because up to 5% of infected persons recover to become carriers of the disease, where the bacterium becomes established in the gall bladder and is shed every time the person goes to the bathroom and carriers do not show any symptoms of infection. Example: Typhoid Mary
Which clostridia toxins cause disease in fowls, cattle, mink & other animals?
Toxin C
Which clostrida toxins is associated with forage poisoning of cattle?
Toxin D
What are 7 types of toxins in Clostridium that give the basis of serological specificity?
Toxins A through G.
Which clostridia toxins cause disease in humans?
Toxins A, B, E, F, & G.
What are exotoxins?
Toxins that are secreted outside the cell. Water soluble, usually heat-labile (heat sensitive) proteins found in the cytoplasm or in the growth medium (as a result of autolysis).
What is the treatment for a Shigella food infection?
Treatment depends upon the severity of the disease. Severe cases or dysentery require antibiotic therapy, rest and fluid replacement.
What is the treatment of infant botulism?
Treatment primarily involves supportive care. Antimicrobial therapy is not recommended.
What are the best preventative steps for getting infected with botulism?
Use current USDA guidelines for home canning & to boil potentially suspect foods for several minutes, or heat to 80 C (176 F) for 10 min, either of which will destroy the neurotoxin.
Where is the Listeria spp. found?
Vegetation Soils Feces Silage Water.
Is C. jejuni heat sensitive or heat resistant?
Very heat sensitive, internal (core) heating to 70 C for 10 min will destroy 10^7 cells in hamburger. Also sensitive to freezing, numbers die at about 1 log/day at -20oC, thus low counts in frozen meat product.
How fast is the internalization of invading Salmonella cells into the host cell?
Very quick! Only around 20 minutes!
Foodborne illnesses are caused by bacteria because of what 3 things?
Widespread distribution Ability to grow rapidly whenever conditions are favorable Relative ease with which they can be detected in food or feces
Are Staphylococci hardy bacteria?
YES!!!
Can clostridia grow in vacuum packaged products like bacon?
Yes & without putting off odor!
Does Listeria grow in the presence of NaCl?
Yes! 10% of NaCl
Can enterotoxins be produced & withstand low water activity?
Yes! Enterotoxin production has been demonstrated at water activity values as low as 0.84.
Is Shigella pretty hardy?
Yes, it's pretty resistant.
Is Listeria a hardy microorganism?
Yes, somewhat, but It's fairly sensitive to heat
What is the pH range of Acid canned foods? What types of canned foods are considered Acid canned foods?
pH 4.0 - 4.6 Tomatoes, pears, etc.
Low Acid canned foods have a pH range of what? What types of canned foods are classified under low acid?
pH > 4/6 Canned foods include meat, milk, many veggies, etc.
What is the optimal growth pH of Shigella?
pH opt is 6-8 Exception: Growth has been noted at 5.0
What is the optimum pH level for staph?
pH optimum is 6 - 7 but can grow over 4.0-9.8 with toxin production at pH >4.7