Lecture Notes on Food Poisoning Microorganisms

Foodborne Illness

Occurs when a pathogen is ingested with food, establishes itself, and multiplies inside the human host. Alternatively, a toxigenic pathogen can establish itself in a food product and produce a toxin, which is then ingested.

Food Toxicoinfection

A combination of infection and intoxication, recognizing that both can occur simultaneously.

Neurotoxin

A toxin present inside a bacterial cell, released upon cell disintegration.

Common in meats due to pH and in canned goods due to anaerobic conditions.

Botulism: Botulinum Toxin

One of nature’s most poisonous biological substances. It is a neurotoxin that binds to nerve terminals attached to muscles, disrupting nerve signals and causing muscle weakness and paralysis.

Also used in Botox, a cosmetic procedure, as a muscle relaxant for certain neuromuscular diseases, but in minute amounts.

Onset time is the incubation period in the body.

Prevention involves considering the pH of the food, as $C. bot$ thrives at pH > 4.6.

Enterotoxin

A toxin produced in or affecting the intestines.

Bacillus cereus

Causes two types of gastrointestinal illnesses.

Emetic syndrome

Its usual symptom is vomiting; commonly associated with rice and cereal-based foods.

Spore Forming Microorganisms

$Bacillus cereus$, $Clostridium botulinum$, and $Clostridium perfringens$ are spore formers, while $Staphylococcus aureus$ is non-spore forming.

Staphylococcus aureus

Approximately 25% of people and animals carry $S. aureus$ on their skin and in their noses as a commensal organism. It doesn’t cause illness in healthy individuals, but when it produces toxin under optimal conditions, it can cause food poisoning.

Proper handwashing is crucial.

One concern with Staphylococcal poisoning is foods that are not cooked after handling, such as sliced meats, pudding, pastries, and sandwiches.

$S. aureus$ can thrive at low water activity, making foods with low water activity risky.

Listeria monocytogenes

Outbreaks are infrequent but often fatal, with a high mortality rate even with few infections.

The microorganism is difficult to study because not everyone tracks their food intake. Listeriosis has a long onset time, making it hard to trace the source.

Endotoxin

Refers to the lipopolysaccharide complex associated with the outer membrane of gram-negative pathogens like $E. coli$.

Top Three Microorganisms for Food Microbiology and Hygiene

$Salmonella$, $E. coli$, and $Listeria$.

Salmonellosis

Infection caused by $Salmonella$. It can be further divided into typhoidal or non-typhoidal, depending on the subspecies.

Salmonella bongori

Predominantly associated with cold-blooded animals and less studied in relation to foodborne diseases.

Serotypes

Refer to a group of organisms within a species that have the same type and number of surface antigens.

Commonly found in eggs.

High numbers of $10,000$ cells are typically required to cause illness, but lower numbers can cause illness if the organisms are protected in high-fat foods.

Salmonella Dublin

A serovar of $S. enterica$.

Salmonella Typhimurium

Another serotype of $Salmonella$.

Typhoid Fever

Illness caused by $Salmonella Typhi$.

Paratyphoid Fever

Illness caused by $Salmonella Paratyphi A$.

Infected individuals can spread the bacteria to others, typically through poor handwashing after using the bathroom.

A rash and fever may indicate dengue or typhoid fever.

E. coli

Can survive at pH < 4.6; $C. botulinum$ is for high acid foods, $S. aureus$ is for low water activity.

Around $5-10$ of those diagnosed with STEC infection develop Hemolytic Uremic Syndrome (HUS), a potentially life-threatening complication.

Clues for HUS include decreased frequency of urination, constant fatigue, and loss of pink color in the cheeks.

Most people with HUS recover within a few weeks.

Thrombotic Thrombocytopenic Purpura (TTP)

Blood clots form in small blood vessels, limiting or blocking oxygen-rich blood flow to organs, potentially leading to kidney failure or heart problems.

According to an Australian government study, $8$ in a million people develop blood clots from side effects.

The vaccine's protection outweighs the risk of blood clots.

The illnesses due to $E. coli$ O157:H7 caused high-profile outbreaks in 1993 in the USA. The FSIS declared O157:H7 as an adulterant in ground beef.

In mid-2012, the USDA FSIS began instituting a zero-tolerance policy for 6 additional strains.

Those with O## are the antigens because the zero groups can cause severe illness, particularly in young children and the elderly.

O26 is an O antigen characteristic of the outermost covering portion of gram-negative bacteria.

Flagella

Flagella is a virulence factor of C. jejuni.

Self-limiting Diseases

Do not require medication; the immune system can fight the disease. Oral rehydration therapy is recommended for mild to moderate dehydration.

Vibrio

They get nutrients from marine animals but can also cause diseases.

Vibrio parahaemolyticus

Cook seafoods at temperatures greater than 45 C to ensure inactivation.

Viruses

Do not grow or make their own energy and can only replicate using a living host cell; they are obligate intracellular parasites.

Viruses are inert, incapable of reproducing or carrying out metabolic processes, and must induce living cells to replicate.

Scientific community considers viruses to lie at or beyond the edge of what is considered to be a living organism.

SARS-COV-2

RNA virus.

Virus Contamination

Can only enter food by external contamination.

Primary contamination results from contaminated raw materials. Secondary contamination occurs during processing, preparation, or serving, often from poor hygiene.

Viruses may shed in extremely high numbers, up to $10^7$ or $10^{10}$. Foodborne viruses have low infectivity of 100 cells or less which combined with the high numbers of shedding can lead to large outbreaks.

Any food can be a potential gateway for a foodborne disease outbreak from viruses.

Potentially Hazardous Foods (PHF)

Must be kept at a particular temperature to minimize bacterial growth or to stop virus formation.

The minimum infectious dose required for HIV infection in humans is unknown but presumably 10 to 100 virus particles with incubation period of 2 to 10 months.

Hepatitis A (HAV)

Causes jaundice (yellowing of skin and eyes).

Primary transmission route is person-to-person, but can also occur via fecal, oral, and vomit oral routes and indirectly through foods.

Rotavirus

Resistance increases with age.

The vulnerable population is the very young.

Amoebiasis

Symptoms are not immediate.

Thoroughly wash fruits and vegetables.

When travelling, consider the sanitation of the country.

Food Safety Practices

• Clean: Wash hands often and sanitize surfaces.

• Separate: Avoid cross-contamination by using separate cutting boards for raw meat/seafood and vegetables. Store ice properly to prevent contamination from raw meat drippings.

• Cook: Cook food to the right temperature to kill germs. Use food-grade thermometers in commercial spaces.

• Chill: Refrigerate food at the proper temperature.

Gut Microbiome Functions

Provides energy for epithelial cells, enhances epithelial barrier integrity, provides immunomodulation and protection against pathogens.

Most bacteria in the gut microbiome are commensal.

Major Gut Microbiome Bacteria

(1) Firmicutes: Includes $Bacilli$, $Clostridia$, $Lactobacillus$; gram-positive cell wall structure.

(2) Bacteroidetes: Gram-negative, non-spore forming, anaerobic or aerobic, rod-shaped bacteria; $Flavobacterium$.

(3) Actinobacteria: Gram-positive bacteria with a high proportion of guanine and cytosine in their chromosomal DNA; $Micrococcus$, $Streptomyces$.

(4) Proteobacteria: Major phylum of gram-negative bacteria; $Escherichia$, $Salmonella$, $Vibrio$, $Helicobacter$.

The bacteria colonize the human body, including organs in the oral cavity, placenta, vagina, skin, and gastrointestinal tract.

The majority of the bacteria reside in the gastrointestinal tract with the major of the predominantly anaerobic bacteria in the colon.

The human body expresses 20,000 eukaryotic genes compared to the gut microbiome which itself expresses 3.3 million prokaryotic genes.

Bacterial Concentration in the GI Tract

• Stomach: $10^1-10^2$ cfu/ml (acidic conditions)

• Small and large intestine: $10^4$ to $10^8$ cfu/ml

• Colon: $10^{10}$ to $10^{12}$ cfu/ml

The development and alteration of the gut microbiome are affected by a variety of factors, including infant feeding methods and lifecycle changes.

Dr. Robin Warren and Professor Barry Marshall

They described the H. pylori infection.

Dr. Warren observed small curve bacteria in his patients’ stomach biopsies and inflammation on the gastric mucosa.

They studied $100$ patients and found that a previously unknown bacteria was present nearly in all patients with gastric inflammation, including the patients with intestinal and stomach ulcers.

The findings led them to conclude that H. pylori was the cause of these intestinal problems and that antibiotic treatments could be effective.

This was initially rejected because most scientists did not believe that bacteria could live in the human stomach due to its acidity (pH 2).

Researchers thought lifestyle factors were to blame for ulcers and cancers rather than bacterial infection.

Dr. Marshall ingested a culture of H. pylori, developed symptoms, had a biopsy, and cultured the bacteria, proving that it caused the symptoms.

Ulcers are now treated with antibiotics and acid-reducing medicines.

H. pylori Risk factors.

Low socioeconomic status, bad level of education, and poor hygiene sanitations are the main major related risk factors associated with H. pylori infection.

Anti-Microbial Resistance (AMR)

Very prevalent today, affecting therapeutic options for H. pylori infection treatment choices.

Probiotics

Some probiotics can improve H. pylori eradication, providing beneficial effects such as producing antimicrobial substances (bacteriocins), surviving acidic environments, reducing gastric inflammation, and adhering to gastric and duodenal cells to compete against pathogens.

Bacterial Virulence Factors

• Capsules: Prevent immune system detection.

• Flagella: Facilitate movement and attachment.

• Exotoxins: Disrupt and regulate important cellular processes, aiding tissue invasion.