Infectious Diseases and Pathogens Overview
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Questions and Answers

What is the primary vector for transmitting plague from rodents to humans?

  • Direct contact with rodents
  • Mosquitoes
  • Contaminated water
  • Rat-flea (correct)
  • Which mechanism is crucial in preventing bacterial colonization in the alimentary tract?

  • Mucus secretions (correct)
  • Natural passages of hollow organs
  • Phagocytic leucocytes
  • Effective drainage
  • Which of the following is NOT a typical route of entry for microorganisms into the body?

  • Inhalation
  • Absorption (correct)
  • Inoculation
  • Ingestion
  • What is the most likely outcome if plague is left untreated?

    <p>Disseminated intravascular coagulation (DIC) (B)</p> Signup and view all the answers

    Which characteristic is most descriptive of Yersinia pestis?

    <p>Gram-negative coccobacillus (B)</p> Signup and view all the answers

    Which of the following factors primarily determines a host's susceptibility to infectious diseases?

    <p>Integrity of physical and chemical barriers and immune defense mechanisms (D)</p> Signup and view all the answers

    What is the term for infections transmitted directly from animals humans?

    <p>Zoonotic infections (C)</p> Signup and view all the answers

    Which of the following processes is not directly described as a stage in the 'chain of transmission' for infectious diseases?

    <p>Incubation period (C)</p> Signup and view all the answers

    Which of the following bacteria is most associated with causing bacterial pneumonias?

    <p>Streptococcus pneumoniae (C)</p> Signup and view all the answers

    Under what conditions do Clostridia undergo vegetative division?

    <p>Anaerobic conditions (A)</p> Signup and view all the answers

    Mycetomas caused by actinomyces are characterized as what type of infection?

    <p>Bacterial (C)</p> Signup and view all the answers

    Which of the following is least likely to predispose an individual to candidiasis?

    <p>Balanced host-organism relationship (A)</p> Signup and view all the answers

    Which of these diseases is caused by Clostridium perfringens?

    <p>Gas gangrene (D)</p> Signup and view all the answers

    What characteristic defines viruses, irrespective of their nucleic acid composition?

    <p>Obligate intracellular parasitism (B)</p> Signup and view all the answers

    Which geographical regions is Yellow Fever typically restricted to?

    <p>Africa and South America (D)</p> Signup and view all the answers

    The grains discharged from the sinuses of a mycetoma infection contain what?

    <p>Colonies of fungi or bacteria (B)</p> Signup and view all the answers

    Which of the following clinical features is most indicative of Dengue Hemorrhagic Fever (DHF) rather than uncomplicated Dengue Fever?

    <p>Cutaneous and intestinal hemorrhages due to thrombocytopenia. (D)</p> Signup and view all the answers

    The term 'denga,' from which 'dengue' is derived, originally referred to what characteristic of the illness?

    <p>Fever accompanied by bleeding. (D)</p> Signup and view all the answers

    What is the primary mechanism by which dengue virus leads to thrombocytopenia in DHF?

    <p>Complement activation and consumptive coagulopathy. (D)</p> Signup and view all the answers

    Which of the following is the most critical factor in determining the outcome of a DHF case?

    <p>The promptness and appropriateness of treatment. (A)</p> Signup and view all the answers

    What is the underlying cause of herpes zoster (shingles)?

    <p>Reactivation of latent varicella-zoster virus. (B)</p> Signup and view all the answers

    Which population is at greatest risk for severe complications from HSV-1 infections?

    <p>Immunodeficient patients and neonates. (A)</p> Signup and view all the answers

    What is the primary mode of transmission for Herpes Simplex Virus (HSV)?

    <p>Close contact with an infected individual. (D)</p> Signup and view all the answers

    Which of these patient presentations would lead a physician to suspect DHF over uncomplicated Dengue Fever?

    <p>A patient presenting with fever, abdominal pain, and spontaneous bleeding from the gums. (A)</p> Signup and view all the answers

    Which of the following is the most accurate description of the incubation period for the rabies virus?

    <p>Varies between 10 days to 3 months, influenced by factors like bite location. (A)</p> Signup and view all the answers

    Which of these clinical features is most directly associated with the localization of the rabies virus in the brainstem?

    <p>Hydrophobia and difficulty swallowing due to throat spasms. (B)</p> Signup and view all the answers

    What is the primary mechanism by which Entamoeba histolytica causes disease in humans?

    <p>Direct lysis and destruction of host tissues by the trophozoite form. (C)</p> Signup and view all the answers

    Which statement accurately differentiates the roles of trophozoites and cysts in the life cycle of Entamoeba histolytica?

    <p>Trophozoites are the active, invasive form found in tissues, while cysts are the dormant, transmissive form. (A)</p> Signup and view all the answers

    Which of the following Plasmodium species is typically associated with the most severe and potentially fatal form of malaria?

    <p>Plasmodium falciparum (C)</p> Signup and view all the answers

    What is the primary vector responsible for the transmission of malaria parasites to humans?

    <p>The female Anopheles mosquito (A)</p> Signup and view all the answers

    In severe falciparum malaria, which complication directly results from the parasite's sequestration in cerebral blood vessels?

    <p>Cerebral malaria (coma) (A)</p> Signup and view all the answers

    Which of the following is NOT typically associated with severe malaria caused by Plasmodium falciparum?

    <p>Hyperglycemia (A)</p> Signup and view all the answers

    Which form of anthrax is also known as 'wool sorters’ disease' and carries the highest fatality rate?

    <p>Pulmonary (D)</p> Signup and view all the answers

    What specific characteristic of Bordetella pertussis allows it to stimulate abundant mucus production in the bronchial epithelium?

    <p>Colonization of the brush border and subsequent proliferation (D)</p> Signup and view all the answers

    Which of the following distinguishes streptococci from staphylococci, besides their arrangement?

    <p>Association with non-suppurative autoimmune complications (B)</p> Signup and view all the answers

    Which bacterial species is most frequently implicated in hospital-acquired surgical wound infections due to its antibiotic resistance?

    <p>Staphylococcus aureus (C)</p> Signup and view all the answers

    Which of the following diseases is NOT typically associated with Staphylococcus aureus infections?

    <p>Whooping cough (D)</p> Signup and view all the answers

    Which streptococcal group is most commonly associated with causing infections in newborns?

    <p>Group B (D)</p> Signup and view all the answers

    What is a key characteristic symptom that definitively indicates a paroxysm of coughing associated with pertussis?

    <p>A characteristic 'whoop' sound (A)</p> Signup and view all the answers

    Which of the following infections is most likely to be caused by Group D streptococci (enterococci)?

    <p>Urinary tract infection (C)</p> Signup and view all the answers

    Flashcards

    Microorganisms

    Bacteria, viruses, fungi, and parasites present everywhere.

    Chain of Transmission

    Process includes reservoir, route, mode, and host.

    Modes of Entry

    Ways pathogens enter the body (ingestion, inhalation, etc.).

    Physical Barrier

    Skin and mucous membranes prevent pathogens from entering.

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    Chemical Barrier

    Mucus and stomach acid prevent bacterial colonization.

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    Plague

    Infectious disease caused by Yersinia pestis, spread by rodents.

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    Anthrax

    Bacterial disease from animals (Bacillus anthracis), rare in humans.

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    Immune Defense Mechanisms

    Body's defenses including phagocytic cells and immune responses.

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    Anthrax types

    Three forms of human anthrax based on entry point: cutaneous, pulmonary, gastrointestinal.

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    Cutaneous anthrax

    Skin infection caused by direct contact with contaminated materials; most common form of anthrax.

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    Pulmonary anthrax

    Severe lung infection from inhaling spores; known as “wool sorters’ disease”; most fatal.

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    Gastrointestinal anthrax

    Rare infection resulting from ingesting contaminated food; least common form of anthrax.

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    Whooping cough

    Highly communicable respiratory disease in children caused by Bordetella pertussis.

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    Staphylococci

    Gram-positive cocci prevalent in various body areas; causes numerous hospital infections.

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    Staphylococcus aureus

    Most pathogenic species of staphylococci; causes various suppurative diseases.

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    Streptococci

    Gram-positive cocci known for autoimmune complications; categorized into groups based on infection type.

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    Streptococcus viridans

    Untypable α-haemolytic streptococci found in the mouth flora, can cause endocarditis.

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    Pneumococcus

    Streptococcus pneumoniae, a bacteria causing pneumonia, meningitis, and septicemia.

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    Clostridia

    Gram-positive anaerobic spore-forming bacteria found in the GI tract of animals and humans.

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    Gas gangrene

    A life-threatening infection caused by Clostridium perfringens, leading to tissue death.

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    Mycetoma

    Chronic infection with draining sinuses, formed by colonies of fungi or bacteria.

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    Candidiasis

    Opportunistic fungal infection normally caused by Candida albicans.

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    Yellow fever

    An old viral hemorrhagic fever primarily in Africa and South America.

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    Fungal infections types

    Includes oral thrush, vaginitis, candidiasis, and systemic infection.

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    Dengue Fever Symptoms

    Sudden onset of high fever, chills, myalgia, headache, and bleeding disorders.

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    Dengue Transmission

    Dengue is caused by a virus transmitted by Aedes aegypti mosquitoes, especially during rainy seasons.

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    Dengue Hemorrhagic Fever (DHF)

    A severe form of dengue with cutaneous and intestinal hemorrhages, thrombocytopenia, and shock.

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    Dengue vs. DHF

    Dengue fever is self-limited; DHF can be fatal if not treated.

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    Varicella Zoster Virus

    A herpes virus causing chickenpox in non-immune individuals and shingles from reactivation.

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    Chickenpox Symptoms

    Acute vesicular rash occurring mainly in children, beginning as nasopharyngeal infection.

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    Herpes Simplex Virus (HSV)

    HSV-1 causes facial blisters; HSV-2 causes genital sores, both spread through contact.

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    Reactivation of VZV

    Herpes zoster (shingles) occurs from reactivation of dormant varicella zoster virus.

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    Rabies virus

    A virus causing fatal encephalitis transmitted by animal bites.

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    Hydrophobia

    A symptom of rabies characterized by painful throat spasms and difficulty swallowing.

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    Amoebiasis

    An infection caused by Entamoeba histolytica that leads to tissue damage.

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    Trophozoite

    The active, feeding stage of Entamoeba histolytica found in tissues.

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    Cystic form

    The dormant, resistant stage of Entamoeba histolytica found in feces.

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    Malaria

    A protozoal disease caused by Plasmodium species, transmitted by Anopheles mosquitoes.

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    Plasmodium falciparum

    The most severe malaria-causing protozoa, leading to malignant malaria.

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    Cerebral malaria

    A severe complication of malaria characterized by coma and brain involvement.

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    Study Notes

    Infectious and Parasitic Diseases

    • Microorganisms (bacteria, viruses, fungi, and parasites) are ubiquitous in soil, water, air, and on surfaces and cause many infectious diseases in humans.

    Chain in Transmission of Infectious Diseases

    • Reservoir of pathogen
    • Route of infection
    • Mode of transmission
    • Susceptible host

    Mode of Entry

    • Microorganisms enter the body through ingestion, inoculation (parenteral), inhalation, perinatally, direct contact, or from contaminated sources (water, food, soil, or animals).

    Factors Relating to Host

    • Physical barriers: intact skin and mucosa prevent entry.
    • Chemical barriers: mucus and stomach acid.
    • Effective drainage: respiratory and gastrointestinal tracts.
    • Immune defenses: phagocytic leukocytes and the immune system.

    Diseases Caused by Bacteria, Spirochaetes, and Mycobacteria

    • Plague is caused by Yersinia (Pasteurella) pestis.
      • It's a zoonotic disease, primarily spread by rats via rat fleas or inhalation.
      • Characterized by rapid progression, chills, fever, myalgia, nausea, vomiting, marked prostration, disseminated intravascular coagulation (DIC), widespread petechiae and ecchymoses, and potential gangrene (black death).
    • Anthrax is caused by Bacillus anthracis.
      • It's a zoonotic disease that is common in animals (cattle and sheep) but rare in humans.
      • Usually an exogenous infection, contracted through contact with soil or animal products contaminated with spores.
      • Three forms: cutaneous, pulmonary, and gastrointestinal. Pulmonary anthrax is most dangerous.
    • Whooping cough (Pertussis) is caused by Bordetella pertussis.
      • Highly communicable disease.
      • Causes low-grade fever, rhinorrhoea, conjunctivitis, excess tear production.
      • Characterized by paroxysms of coughing with a whooping sound; may be fatal in infants due to asphyxia.

    Staphylococcal Infections

    • Staphylococci are gram-positive cocci found in skin, umbilicus, nasal passages, and stool.
    • Staph. aureus is the most common pathogen in staphylococcal infections.
    • Staphylococcal infections include skin infections, burn infections, respiratory tract infections, bone infections (osteomyelitis), bacterial endocarditis, bacterial meningitis, sepsis, and toxic shock syndrome.

    Streptococcal Infections

    • Streptococci are gram-positive cocci that are more frequently associated with non-suppurative complications and autoimmune reactions..
    • Group A streptococci (Streptococcus pyogenes), responsible for upper respiratory tract infections and skin infections.
    • Group B streptococci (Streptococcus agalactiae), a major cause of neonatal infections.
    • Group C and G, responsible for respiratory infections.
    • Group D streptococci (Streptococcus faecalis, also called enterococci), can cause urinary tract infections, bacterial endocarditis, and sepsis.
    • Less common streptococci, such as Streptococcus viridans and Streptococcus pneumoniae, can lead to bacterial endocarditis and pneumonia respectively.

    Clostridial Diseases

    • Clostridia are gram-positive, spore-forming, anaerobic microorganisms.
    • Common diseases: gas gangrene (caused by C. perfringens), tetanus (caused by C. tetani), botulism (caused by C. botulinum), clostridial food poisoning (caused by C. perfringens), and necrotizing enterocolitis (caused by C. perfringens).

    Diseases Caused by Fungi

    • Mycetoma is a chronic, suppurative infection characterized by draining sinuses with grains (fungal or bacterial colonies).
      • Two types: actinomycotic (higher bacteria) and eumycetomas (true fungi).
    • Candidiasis is an opportunistic fungal infection caused most commonly by Candida albicans.
      • Present as normal flora in the skin, mucous membranes, intestines, and vagina.
      • Pathogenic when the host-organism balance is disturbed.

    Diseases Caused by Viruses

    • Viral diseases are a common cause of human illness.
    • Viruses are intracellular parasites with single- or double-stranded RNA or DNA genomes.

    Yellow Fever

    • The oldest known viral hemorrhagic fever, restricted to Africa and South America.
    • Characterized by: high fever, chills, myalgia, headache, jaundice, hepatic failure, renal failure, bleeding disorders, and hypotension.

    Dengue Hemorrhagic Fever (DHF)

    • Caused by virus transmitted by the mosquito Aedes aegypti.
    • Two forms:
      • Dengue fever ("break-bone fever")—a self-limited febrile illness affecting muscles/joints with severe back pain.
      • Dengue hemorrhagic fever (DHF)—more severe and life-threatening. Characterized by vascular permeability, thrombocytopenia, plasma leakage, and potentially fatal shock.

    Varicella-Zoster Virus

    • Causes chickenpox (varicella) and shingles (herpes zoster).
    • Chickenpox is an acute vesicular exanthem (skin rash).
    • Shingles is a reactivation of dormant varicella zoster virus.

    Herpes Simplex Virus

    • Two types: HSV-1 (oral herpes) and HSV-2 (genital herpes).
    • Characterized by vesicular lesions on skin, mouth, and genitals.

    Rabies

    • Fatal encephalitis caused by rabies virus.
    • Transmitted through the bite of infected mammals.
    • Characterized by a long incubation period, followed by progressive neurological symptoms (difficulty swallowing, painful spasms (hydrophobia), and delirium) that lead to death within weeks of infection.

    Amoebiasis

    • Caused by Entamoeba histolytica.
    • Exists in two forms: trophozoite (active form in tissues and stool) and cyst (resistant form that survives outside the body)

    Malaria

    • Caused by Plasmodium species (e.g., P. falciparum, P. vivax).
    • Transmitted through the bite of infected female Anopheles mosquitoes.
    • Can cause severe complications including cerebral malaria, a major cause of death.

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    Test your knowledge on key concepts related to infectious diseases, including transmission mechanisms, host susceptibility, and specific pathogens. This quiz covers various aspects of microbiology and the factors influencing disease processes in humans.

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