Micro W12: Infections of the GI syst.

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Questions and Answers

What is a significant route for infections of the GI system?

Vector-borne transmission

Airborne transmission

Fecal-oral route (correct)

Transplacental transmission

Which bacteria is primarily responsible for gastric and peptic ulcers?

Streptococcus pyogenes

Helicobacter pylori (correct)

Escherichia coli

Lactobacillus

Which statement is true about the resident flora in the stomach?

Bacterial population is high due to the high acidity.

The stomach contains a wide variety of bacteria.

Helicobacter pylori is adapted to survive in the acidic environment of the stomach. (correct)

The stomach is dominated by gram-positive bacteria.

What is the primary characteristic of the resident flora in the large intestine?

Bacteria have ample time to colonize and reproduce. Signup and view all the answers

Which of the following best describes the effect of antibiotics on the resident flora?

They can cause an imbalance in resident flora. Signup and view all the answers

What is the main characteristic of botulinum that allows it to thrive in certain conditions?

It is an anaerobe that flourishes in sealed containers. Signup and view all the answers

What type of symptoms are most commonly associated with Staphylococcal intoxication?

Nausea, vomiting, and abdominal pain. Signup and view all the answers

Which of the following is true regarding Bacillus cereus emetic type intoxication?

Symptoms occur 30 minutes to 6 hours after ingestion. Signup and view all the answers

What is the principal mode of transmission for Hepatitis A and E viruses?

Fecal-oral route. Signup and view all the answers

Which organism is primarily responsible for most cases of infectious diarrhea in children?

Rotavirus. Signup and view all the answers

What is a key characteristic of Aspergillus-related illnesses?

It produces aflatoxin which is carcinogenic. Signup and view all the answers

Which of the following describes Trichinosis?

Acquired by eating undercooked pork. Signup and view all the answers

What is the most common type of helminth infection in humans?

Ascaris lumbricoides (Ascariasis). Signup and view all the answers

Which of the following symptoms is associated with Ergotism?

Burning pain in limbs and hallucinations. Signup and view all the answers

What role does the GI tract play in microbial infections?

It serves as a common entry point for various microbes and their toxins. Signup and view all the answers

What is the main cause of gastroenteritis?

Ingestion of contaminated food or water Signup and view all the answers

Which of the following is a symptom of typhoid fever?

Severe headaches Signup and view all the answers

What is a common contributing factor to periodontal disease?

Tobacco use Signup and view all the answers

How is shigellosis primarily transmitted?

Fecal-oral route Signup and view all the answers

Which organism is commonly associated with causing peptic ulcers?

Helicobacter pylori Signup and view all the answers

What is a characteristic symptom of salmonellosis?

Diarrhea Signup and view all the answers

What significant issue is related to the treatment of typhoid fever?

Antibiotic resistance Signup and view all the answers

Which food safety practice can help prevent salmonellosis?

Cooking eggs thoroughly Signup and view all the answers

Which of the following is a type of bacterial intoxication?

Botulism Signup and view all the answers

Which statement best describes the mortality rate of listeriosis?

High mortality rate of 20-30% Signup and view all the answers

What is a common symptom of gastroenteritis?

Mild to severe diarrhea Signup and view all the answers

What commonly contributes to the development of dental caries?

Dental plaque accumulation Signup and view all the answers

Which of the following strains of bacteria is primarily responsible for campylobacteriosis?

Campylobacter jejuni Signup and view all the answers

Which factor does NOT contribute to the risk of developing periodontal disease?

Regular exercise Signup and view all the answers

Study Notes

GI Tract Infections

Microbes and toxins enter the GI tract easily, making it a significant portal of entry.
Foodborne illnesses are a global concern.
Fecal-oral transmission is a key factor in GI infections.

Resident GI Flora

The GI tract has a complex and diverse microbial ecosystem.
Microbial type and amount vary along the tract (increasing from mouth to large intestine).
Antibiotics can disrupt the flora balance.
Probiotics can replenish the flora.
Diet significantly influences the resident flora.

Oral Cavity Flora

The oral cavity has a complex and diverse microbial ecosystem, mostly bacteria.
The oral cavity is colonized quickly after birth, initially dominated by Streptococcus salivarius.

Stomach Flora

The stomach's high acidity limits bacterial populations.
Surviving bacteria are often transferred to the small intestine.
Helicobacter pylori is an exception, thriving in the stomach.
It causes most stomach and peptic ulcers.
It is highly motile and burrows into the stomach lining to neutral pH zones.

Small Intestine Flora

The small intestine is generally a less favorable environment than the stomach for bacteria due to peristalsis and digestive fluids (bile and pancreatic juice).
Bacteria are relatively low in the small intestine until closer to the end.
Gram-positive bacteria (e.g., lactobacilli and E. faecalis) are some typical inhabitants.

Large Intestine Flora

The large intestine has a slow flow rate, enabling significant colonization and reproduction of bacteria.
It contains ~1000 species.
Colon bacteria aid in digesting polysaccharides like cellulose and synthesizing vitamins K and B.
Bacteria comprise ~20% of healthy stool.

Dental Caries and Periodontal Disease

Dental plaque (biofilm) on teeth creates a microbial environment conducive to caries.
Caries arise from unchecked dental plaque buildup
Gingivitis (gum inflammation) is a precursor to periodontitis.
Periodontitis leads to tooth decay, loss, and systemic infections.
Periodontal disease includes gingivitis and periodontitis, with contributing factors like smoking, genetics, pregnancy, puberty, stress, medications, and systemic diseases.
Necrotizing ulcerative gingivitis is also a relevant consideration.

Gastroenteritis

Gastroenteritis is stomach and intestine inflammation, often caused by microorganisms or ingested toxins.
It is a leading cause of death in developing nations, especially among children.
Common in congregate settings.
Symptoms range from mild discomfort to severe diarrhea, nausea, vomiting, cramps, and loss of appetite.
Causes include contaminated food/water, infected individuals, unwashed hands, unclean utensils, and contaminated workspaces.

Bacterial Infections

Bacteria are common causes of foodborne illness.
Bacteria adhere and multiply within the GI tract.
Bacterial intoxication is caused by pre-formed bacterial toxins consumed.

Specific Bacterial Infections

Helicobacter peptic ulcer: Caused by H. pylori, treated with antibiotics, acid reducers, and stomach protectors.
Salmonellosis: Caused by Salmonella spp., particularly from contaminated animal products like raw/undercooked eggs, poultry, and meat. Concerns exist regarding antibiotic resistance in food animals.
Typhoid fever: Caused by Salmonella enterica serotype Typhi. Transmitted through contaminated food or water, characterized by a high fever, severe headache, and digestive symptoms.
Paratyphoid fever: Caused by Salmonella enterica, similar to typhoid but milder.
Shigellosis (bacillary dysentery): Caused by Shigella spp., characterized by diarrhea (often bloody), fever, and stomach cramps.
Campylobacteriosis: Main cause of bacterial diarrhea in the US, linked to raw poultry and contaminated water/food.
Escherichia spp. gastroenteritis: Some E. coli strains are pathogenic, causing the production of enterotoxins.
Yersiniosis: Caused by Yersinia enterocolitica, often associated with contaminated food and water.
Listeriosis: Caused by Listeria monocytogenes, posing a high mortality risk (20-30%) and linked to contaminated foods (e.g., undercooked/processed meats).

Bacterial Intoxications

Botulism: Caused by Clostridium botulinum toxin, a neurotoxin; highly lethal, especially through inhalation.
Staphylococcal intoxication: Caused by Staphylococcus aureus toxins, characterized by nausea, vomiting, abdominal pain, frequently from contaminated foods (hand to food is significant).
Bacillus intoxication: Caused by Bacillus cereus toxin; two types exist – diarrheal and emetic type.

Viral Infections

Rotavirus: Most common infectious diarrheal agent in infants and children
Hepatitis: Liver inflammation, caused by hepatitis A to E viruses. Fecal-oral route transmission is common for A and E.
Astroviruses and caliciviruses: Symptoms include diarrhea, headache, malaise, and nausea.
Noroviruses: Highly contagious, cause diarrhea, nausea, muscle aches and fever, symptoms last 1-2 days but infectivity can persist for weeks.
Adenoviruses: Can cause respiratory illness and gastroenteritis, especially in children.

Fungal Infections

Candidiasis: Overgrowth of Candida yeast; more common in immunocompromised individuals (thrush).
Aspergillosis: Illness caused by Aspergillus species, potentially toxic.
Ergotism: Poisoning from Claviceps purpurea (toxic alkaloids produced from contaminated rye/wheat).

Parasitic Infections

Helminths (e.g., Trichinosis, Taeniasis, Pinworms, Ascariasis, Necatoriasis): Caused by various worms.
Transmission often involves eating contaminated food or water related to animal products.

Summary

The GI tract is a common portal of entry. Many GI infections are linked to contaminated food or water and a variety of microbes cause such infections. Microorganisms, viruses, fungi, parasites, and even helminths can infect the GI tract.

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