Clinical Microbiology Chapter 5 Quiz
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Questions and Answers

What role does lactic acid play in the development of dental caries?

Lactic acid produced by dental plaque can break down the enamel of the teeth.

What happens if dental caries penetrate beyond the enamel?

If untreated, bacteria can penetrate into the dentin and eventually reach the pulp of the tooth.

Which microorganisms dominate the bacterial population in the later stages of tooth decay?

The dominant microorganisms are gram-positive rods and filamentous bacteria.

How is sucrose related to the incidence of dental caries in the Western world?

<p>The introduction of sucrose into the diet correlates with an increase in dental caries prevalence.</p> Signup and view all the answers

What are some effective strategies to prevent dental caries?

<p>Effective strategies include minimizing sucrose intake, regular brushing and flossing, and using fluoride.</p> Signup and view all the answers

What is dental abscess, and how can it form?

<p>A dental abscess is an infection that occurs when decay progresses to the soft tissues, often caused by mixed bacterial populations.</p> Signup and view all the answers

What is hepatitis, and which viruses are known to cause it?

<p>Hepatitis is an inflammation of the liver, caused by at least five different viruses, including HBV, EBV, and CMV.</p> Signup and view all the answers

Describe the structure of the Hepatitis B virus (HBV).

<p>HBV is a large virus containing partially double stranded DNA and is covered by an envelope.</p> Signup and view all the answers

What are the primary vehicles for transmitting microbial diseases of the digestive system?

<p>Food or water contaminated with pathogenic microorganisms or their toxins.</p> Signup and view all the answers

What is the role of dextran in the formation of dental plaque?

<p>Dextran serves as a gummy polysaccharide that helps bacteria adhere to the tooth surface, contributing to plaque formation.</p> Signup and view all the answers

Explain how dental caries initiation begins with S. mutans.

<p>The initiation of caries begins when S. mutans attaches to a tooth's pellicle, facilitated by the formation of dextran.</p> Signup and view all the answers

What components are broken down by S. mutans during the caries process, and what are the products?

<p>S. mutans hydrolyzes sucrose into fructose and glucose, fermenting fructose into lactic acid.</p> Signup and view all the answers

Describe the structure of the human digestive system as outlined in the context.

<p>The digestive system is a tubelike structure including the mouth, pharynx, esophagus, stomach, small and large intestines, along with accessory organs.</p> Signup and view all the answers

What is the significance of effective sanitation practices in food handling concerning microbial diseases?

<p>Effective sanitation practices interrupt the fecal–oral cycle, which is essential for preventing the transmission of digestive system diseases.</p> Signup and view all the answers

What characteristics of Streptococcus mutans contribute to its cariogenic potential?

<p>Streptococcus mutans metabolizes a variety of carbohydrates, tolerates high acidity, and synthesizes dextran.</p> Signup and view all the answers

How does a freshly brushed tooth become susceptible to dental caries?

<p>A freshly brushed tooth quickly becomes coated with a pellicle that allows cariogenic bacteria to establish and produce dextran.</p> Signup and view all the answers

What typically happens to the immune response in individuals infected with HBV?

<p>The immune system often fails to recognize the virus as foreign, leading to high immunologic tolerance and chronic infection.</p> Signup and view all the answers

In which populations is acute HBV infection most prevalent in low-prevalence countries?

<p>Acute HBV infections are most common among young adults engaging in risky behaviors such as injection drug use or sexual promiscuity.</p> Signup and view all the answers

What is the first step in the pathogenesis of HBV after infection?

<p>The partially double-stranded viral DNA is converted to fully double-stranded DNA.</p> Signup and view all the answers

What role do the HBV encoded proteins play in the infected cells?

<p>They stimulate the innate immune response, cause mitochondrial damage, and stress the endoplasmic reticulum.</p> Signup and view all the answers

How is HBV diagnosed in patients?

<p>Diagnosis is typically based on symptoms along with liver function tests and serologic tests for HBV antigens and antibodies.</p> Signup and view all the answers

What are some preventive measures against HBV transmission?

<p>Preventive measures include using disposable needles, barrier contraception, and screening transfused blood.</p> Signup and view all the answers

What is the outcome for immunocompetent individuals infected with HBV?

<p>About 99% of immunocompetent individuals develop a strong immune response and clear the virus, avoiding chronic disease.</p> Signup and view all the answers

What indicates that a person has developed immunity to HBV after infection?

<p>The appearance of antibodies following the clearance of the virus indicates that the person is considered immune.</p> Signup and view all the answers

What are the three distinct particles found in the serum of patients with hepatitis B?

<p>The three distinct particles are the complete virion (Dane particle), smaller spherical particles, and filamentous particles.</p> Signup and view all the answers

How does chronic liver disease (CLD) progress in patients with hepatitis B?

<p>CLD progresses from hepatitis to fibrosis, then cirrhosis, and can eventually lead to hepatocellular carcinoma (HCC) over 30–50 years.</p> Signup and view all the answers

What percentage of infants who become infected with hepatitis B are likely to become chronic carriers?

<p>About 90% of infants infected with hepatitis B are likely to become chronic carriers.</p> Signup and view all the answers

What are common symptoms observed in acute hepatitis B infection?

<p>Common symptoms include fatigue, low-grade fever, nausea, abdominal pain, jaundice, and dark urine.</p> Signup and view all the answers

Which population groups are at higher risk for hepatitis B infection?

<p>Health care workers, intravenous drug users, and children born to HBV-positive mothers are at higher risk.</p> Signup and view all the answers

What condition is considered when hepatitis lasts for more than 6 months?

<p>If hepatitis lasts for more than 6 months, it is considered to have become chronic.</p> Signup and view all the answers

What is the significance of fulminant hepatitis in the context of acute hepatitis B infection?

<p>Fulminant hepatitis is a rare but severe complication that causes sudden, massive liver damage, often requiring a liver transplant for survival.</p> Signup and view all the answers

How does the transmission of hepatitis B differ in high-prevalence countries compared to others?

<p>In high-prevalence countries, HBV infection is often acquired perinatally from infected mothers around the time of birth.</p> Signup and view all the answers

Study Notes

Clinical Microbiology 0511 MBO 212

  • Course offered by Ahnaf Tahmid Saqif

Brief Introduction to Microbiology of Major Infectious Diseases (Chapter 5)

  • This chapter likely covers a broad overview of various infectious diseases from a microbiological perspective.

Microbial Diseases of the Digestive System (Lecture 9)

  • This lecture focuses on diseases affecting the digestive system caused by microbes.

Introduction

  • Microbial diseases of the digestive system stem from ingesting contaminated food or water containing pathogenic microorganisms or their toxins.
  • Pathogens often contaminate food or water after being shed in feces from infected people or animals.
  • These diseases typically spread via a fecal-oral cycle.
  • Effective food production and handling sanitation procedures break this cycle.

Structure of the Digestive System

  • The digestive system is a tube-like structure encompassing the mouth, pharynx (throat), esophagus, stomach, small and large intestines.
  • Accessory structures include teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Dental Caries

  • Teeth allow microbial masses (dental plaque) to accumulate, a biofilm type.
  • Streptococcus mutans is the primary cariogenic bacterium.
  • They metabolize carbohydrates, tolerate acidity, and produce dextran – a gummy polysaccharide.

Dental Caries Pathogenesis

  • Caries initiation relies on mutans attachment to the tooth.
  • A pellicle (thin film of proteins) coats the tooth surface within minutes.
  • Cariogenic bacteria colonize the pellicle and produce dextran within hours.
  • Dextran production involves sucrose hydrolysis into fructose and glucose, with glucosyltransferase assembling glucose molecules into dextran, and fructose fermenting into lactic acid.
  • Dental plaque consists of bacteria and dextran.
  • Lactic acid erodes tooth enamel.
  • Untreated enamel erosion allows bacteria to penetrate further into the tooth.
  • The bacterial composition changes as decay spreads from enamel to dentin.
  • Mutans are present in minimal amounts compared to other bacteria.
  • Progression of decay reaches the pulp (containing blood supply and nerve cells).
  • Without treatment, infection spreads to soft tissues potentially resulting in abscesses.

Sucrose and Dental Caries

  • Dental caries were relatively rare in the Western world until the 17th century.
  • Sucrose introduction correlates with a rise in caries.
  • High-starch diets show lower caries rates unless sucrose is included.

Prevention

  • Sugar alcohols (e.g., mannitol, sorbitol, xylitol) are not cariogenic, thus used in sugar-free foods.
  • Effective prevention involves minimizing sucrose intake, regular brushing and flossing, professional cleanings, and fluoride application.

Hepatitis

  • Hepatitis is liver inflammation.

  • Multiple viruses cause hepatitis with more potentially undiscovered or unidentified.

  • Infections by other viruses (e.g., Epstein-Barr Virus (EBV), cytomegalovirus (CMV)) might also cause hepatitis sporadically.

  • Detailed table on various types of hepatitis (pathogen, symptoms, incubation periods, transmission, diagnostic tests, treatments, and vaccines)

HBV (Hepatitis B Virus)

  • HBV is a large, partially double-stranded DNA virus with an envelope.
  • Patient serum contains three different HBV particles: complete virion (Dane particle), smaller spherical particles, and filamentous particles.

HBV Infection

  • HBV infection is associated with chronic liver diseases (CLD) ranging from hepatitis to fibrosis, cirrhosis, and finally hepatocellular carcinoma (HCC) over decades.
  • CLD pathogenesis is marked by the persistence of immune responses against virus-infected hepatocytes.
  • HCC is a significant cause of cancer-related mortality.

Acute HBV Infection

  • Many HBV infections are subclinical, meaning people don't exhibit symptoms, but in others, symptoms include fever, nausea, abdominal pain, jaundice, and dark urine.
  • In a small number of cases, fulminant hepatitis (massive liver damage) may occur.

Chronic HBV Infection

  • Hepatitis lasting more than six months is classified as chronic.
  • High chronic carrier rates seen in people infected during childhood.
  • Likelihood of chronic infection diminishes as age increases.

Risk Population

  • Health care workers and IV drug users have higher exposure and infection risks due to their frequent exposure to blood.
  • Children born to HBV-positive mothers also face elevated risk.

Transmission

  • High-prevalence regions (Asia): HBV acquisition is often perinatal. The immune system demonstrates tolerance for the virus resulting in chronic infection.
  • Low-prevalence regions (West): Transmission usually comes from exposure to infected blood or bodily fluids. Commonly associated with risky behaviours in young adults like intravenous drug use and promiscuous sex. In these scenarios, it often resolves without progression to chronic disease.

HBV Pathogenesis

  • HBV's partially double-stranded DNA becomes fully double stranded upon infection.
  • The viral genome acts as a template for sub-genomic RNA and pre-genomic RNA transcription within infected cells.
  • Viral proteins trigger innate immune responses, damage mitochondria, and stress endoplasmic reticulum, leading to inflammation and liver damage.
  • A weak immune response allows the virus to persist for years.

Diagnosis

  • Diagnosis relies on symptoms and liver functionality tests.
  • Serologic tests detect HBV antigens (HBsAg).
  • Presence of HBsAg confirms active infection.

Prevention

  • Precautions, such as disposable needles, barrier-type contraception, and blood screening reduce risk.
  • HBV vaccines are widespread in childhood immunization schedules.

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Description

Test your knowledge on the microbiology of major infectious diseases, particularly focusing on microbial diseases of the digestive system. This quiz covers various pathogens, their transmission, and effective sanitation practices. Dive into the complexities of how these diseases affect the digestive system and their impact on public health.

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