8 - Infectious Diseases

Question 1

How are most skin infections initiated?

Answer 1

Mechanical injury of the epidermis

Question 2

How are most gastrointestinal pathogens transmitted?

Answer 2

Fecal-oral route via contaminated food or drink

Question 3

What is the body’s principal method of defending against fecal-orally transmitted infections?

Answer 3

Acidic gastric secretions, pancreatic enzymes, and bile detergents

Question 4

What do both the skin and gut epithelial cells produce to protect against infectious disease?

Answer 4

IgA antibodies

Question 5

How are most infections transmitted from person to person (3)?

Answer 5

Respiratory, fecal-oral, or sexual routes

Question 6

How can infectious diseases escape from antibody-mediated host defenses?

Answer 6

Antigenic variation

Question 7

What is the ultimate means by which infectious diseases can avoid the immune system?

Answer 7

Latent infection in which few if any viral genes are expressed

Question 8

What is it called when viral agents have a predilection for certain types of cell to infect?

Answer 8

Tropism

Question 9

What bacterial surface proteins bind bacteria to host cells or ECM?

Answer 9

Adhesins

Question 10

How does tuberculosis utilize the immune system in its replication?

Answer 10

M. tuberculosis activates the alternative complement pathway, resulting in opsonization with C3b. Once coated with C3b, M. tuberculosis binds to the CR3 complement receptor on macrophages, enters the macrophages, and replicates within phagosomes

Question 11

Describe bacterial endotoxin.

Answer 11

A lipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria that both stimulates host immune responses and injures the host

Question 12

Describe bacterial exotoxins.

Answer 12

Secreted bacterial proteins that cause cellular injury and disease.

Question 13

What are some examples of bacterial exotoxins?

Answer 13

Enzymes, toxins altering intracellular signaling, neurotoxins, superantigens

Question 14

What are some types of inflammatory response to infectious disease?

Answer 14

Suppurative, granulomatous, cytopathic-cytoproliferative reactions, tissue necrosis, scarring

Question 15

How are most infectious diseases diagnosed?

Answer 15

Cultures, biochemical or serologic identification, and molecular diagnosis

Question 16

What stain can identify most bacteria?

Answer 16

Gram stain

Question 17

What stain can identify mycobacteria and nocardiae?

Answer 17

Acid-fast stain

Question 18

What stain can identify fungi, legionella, and pneumocystis?

Answer 18

Silver stain

Question 19

What stain can identify fungi and amebae?

Answer 19

Periodic acid-Shiff stain

Question 20

What three techniques can identify all classes of infectious agents?

Answer 20

Antibody stains, culture, DNA probes

Question 21

What are four examples of respiratory viruses with acute (transient) presentation?

Answer 21

Adenovirus, rhinovirus, influenza, and respiratory syncytial virus

Question 22

What are four examples of digestive viruses with acute (transient) presentation?

Answer 22

Mumps, Rotavirus, Norovirus, and Hepatitis A-E

Question 23

What are four examples of systemic viruses with acute (transient) presentation and skin eruptions?

Answer 23

Measles, Rubella, Varicella-zoster, HHSV 1-2

Question 24

What are three examples of systemic viruses with acute (transient) presentation and hematopoietic disorders?

Answer 24

CMV, EBV, and HIV-1-2

Question 25

What are two examples of arboviral- and hemorrhagic fever-related viruses with acute (transient) presentation?

Answer 25

Dengue and Yellow fever

Question 26

What is an example of a viruse with acute (transient) presentation of the skin /genital warts?

Answer 26

HPV

Question 27

What are two examples of CNS viruses with acute (transient) presentation?

Answer 27

Poliovirus and JC virus

Question 28

What is a rare, late complication of measles?

Answer 28

Encephalitis

Question 29

Describe mumps (type and presentation).

Answer 29

Acute systemic viral infection; pain and swelling of the salivary glands

Question 30

Is there more than one type of mumps?

Answer 30

Yes: mumps parotitis, orchitis, and encephalitis

Question 31

Describe poliovirus (transmission, type, presentation).

Answer 31

Fecal-oral; a spherical, unencapsulated RNA virus; anterior horn destruction and paralysis of limb and diaphragm

Question 32

What is latency as it refers to viral genomes?

Answer 32

The persistence of viral genomes in cells that do not produce infectious virus

Question 33

What effects can the superantigens in Staphylococcus aureus and Streptococcus pyogenes cause?

Answer 33

Toxic shock syndrome and food poisoning

Question 34

What disease does Streptococcus pyogenes cause (respiratory)?

Answer 34

Pharyngitis

Question 35

What disease does Corynebacterium diphtheria cause (respiratory)?

Answer 35

Diphtheria

Question 36

What disease does Bordetella pertussis cause (respiratory)?

Answer 36

Pertussis

Question 37

What disease does Streptococcus pneumonia cause (respiratory)?

Answer 37

Lobar pneumonia

Question 38

What disease does Mycobacterium tuberculosis cause (respiratory)?

Answer 38

Tuberculosis

Question 39

What disease does Legionella pneumophila cause (respiratory)?

Answer 39

Legionnaire disease

Question 40

What disease does Helicobacter pylori cause (gastrointestinal)?

Answer 40

Peptic ulcers

Question 41

What disease do Vibrio cholerae and enterotoxigenic E. coli cause (gastrointestinal)?

Answer 41

Noninflammatory gastroenteritis

Question 42

What disease do Shigella species, Salmonella species, Campylobacter jejuni, and enterohemorrhagic E. coli cause (gastrointestinal)?

Answer 42

Inflammatory gastroenteritis

Question 43

What disease does Salmonella typhi cause (gastrointestinal)?

Answer 43

Enteric (typhoid) fever

Question 44

What disease does Clostridium difficile cause (gastrointestinal)?

Answer 44

Psuedomembranous colitis

Question 45

What disease do Neisseria meningitidis, Streptococcus pneumonia, Haemophilus influenza, and Listeria monocytogenes cause (nervous)?

Answer 45

Acute meningitis

Question 46

What disease do Clostridium tetani and Clostridium botulinum cause (nervous)?

Answer 46

Paralytic intoxications, tetanus, and botulism

Question 47

What disease do Escherichia coli, Pseudomonas aeruginosa, S. saprophyticus, and Enterococcus species cause (urogenital)?

Answer 47

UTIs

Question 48

What disease does Neisseria gonorrhoeae cause (urogenital)?

Answer 48

Gonorrhea

Question 49

What disease does Chlamydia trachomatis cause (urogenital)?

Answer 49

Chlamydia

Question 50

What disease does Treponema pallidum cause (urogenital)?

Answer 50

Syphilis

Question 51

What disease does Staphylococcus aureus cause (skin and adjacent soft tissue)?

Answer 51

Abcess, cellulitis

Question 52

What disease does Streptococcus pyogenes cause (skin and adjacent soft tissue)?

Answer 52

Impetigo, erysipelas, necrotizing fasciitis

Question 53

What disease does Clostridium perfringens cause (skin and adjacent soft tissue)?

Answer 53

Gas gangrene

Question 54

What disease does Bacillus anthracis cause (skin and adjacent soft tissue)?

Answer 54

Cutaneous anthrax

Question 55

What disease does Pseudomonas aeruginosa cause (skin and adjacent soft tissue)?

Answer 55

Burn infections

Question 56

What disease does Mycobacterium leprae cause (skin and adjacent soft tissue)?

Answer 56

Leprosy

Question 57

What disease does Yersinia pestis cause (disseminated infections)?

Answer 57

Plague

Question 58

What disease does Borrelia burgdorferi cause (disseminated infections)?

Answer 58

Lyme disease

Question 59

What disease does Brucella species cause (disseminated infections)?

Answer 59

Brucellosis (undulant fever)

Question 60

What disease do Streptococcus agalactiae and Listeria monocytogenes cause (disseminated neonatal infections)?

Answer 60

Neonatal bacteremia, meningitis

Question 61

What disease do Treponema pallidum cause (disseminated neonatal infections)?

Answer 61

Congenital syphilis

Question 62

Describe Staphylococcus aureus.

Answer 62

Pyogenic, gram-positive cocci; A myriad of skin lesions (boils, carbuncles, impetigo, and scalded-skin syndrome) as well as abscesses, sepsis, osteomyelitis, pneumonia, endocarditis, food poisoning, and toxic shock syndrome

Question 63

What factors are important to know about Staphylococcus aureus?

Answer 63

Clumping factors; alpha-, beta-, and delta-toxin; exfoliative toxins A and B; superantigens

Question 64

What is a growing problem in Staphylococcus aureus infections?

Answer 64

Antibiotic resistance (e.g. MRSA)

Question 65

What do streptococci cause?

Answer 65

Suppurative infections of the skin, oropharynx, lungs, and heart valves

Question 66

What is distinctive about the pyogenic infection caused by Staphylococcus aureus?

Answer 66

Its local destruction of host tissue

Question 67

What is a furuncle (boil)?

Answer 67

A focal suppurative inflammation of the skin and subcutaneous tissue

Question 68

What is a carbuncle?

Answer 68

A deeper suppurative infection that spreads laterally beneath the deep subcutaneous fascia and then burrows superficially to erupt in multiple adjacent skin sinuses

Question 69

What is the effect of Staphylococcus aureus that can result from the desquamation of the epidermis (most frequently in children)?

Answer 69

Scalded-skin syndrome (Ritter disease)

Question 70

What is a very important cause of community-acquired lobar pneumonia?

Answer 70

Streptococcus pneumoniae

Question 71

What is a characteristic finding of diptheria-induced pharyngitis?

Answer 71

A pseudomembrane

Question 72

Describe Listeria monocytogenes.

Answer 72

A gram-positive bacillus that causes severe food-borne infections in vulnerable hosts (pregnant women, neonates, older adults, and immunosuppressed persons)

Question 73

Describe bacillus anthracis.

Answer 73

Anthrax is characterized by necrotizing inflammatory lesions in the skin or gastrointestinal tract or systemically

Question 74

What are the three types of anthrax?

Answer 74

Cutaneous (95% of cases), inhalational, and gastrointestinal

Question 75

What are the two subunits of anthrax toxin?

Answer 75

Edema factor and lethal factor

Question 76

Name some gram-negative bacterial infections.

Answer 76

Niesseria (meningitidis, gonorrhoeae), pertussis, pseudomonas, plague, chancroid

Question 77

In who does Pseudomonas cause deadly infection?

Answer 77

People with cystic fibrosis, severe burns, or neutropenia

Question 78

What kind of effects do Pseudomonas have?

Answer 78

Necrotizing pneumonia, bacterial vasculitis, ethycema gangrenosum

Question 79

What gram-negative bacteria causes the plague?

Answer 79

Yersinia pestis

Question 80

Are mycobacteria aeorbic or anaerobic? (*Hint: think of TB)*

Answer 80

Aerobic

Question 81

What is different about the unique, waxy cell wall of mycobacteria?

Answer 81

They are acid-fast; they contain mycolic acid

Question 82

Are mycobacteria gram-negative or gram-positive?

Answer 82

Weakly gram-positive

Question 83

Who is most affected by TB, in the world and U.S.?

Answer 83

Tuberculosis flourishes wherever there is poverty, crowding, and chronic debilitating illness. In the United States, tuberculosis is mainly a disease of older adults, immigrants from high-burden countries, racial and ethnic minorities, and people with AIDS

Question 84

What is generally the only evidence of asymptomatic TB infection?

Answer 84

A small, fibrocalcific pulmonary nodule

Question 85

What type of hypersensitivity is indicated in a positive PPD test?

Answer 85

Type IV

Question 86

What are the steps of TB infection?

Answer 86

Entry into macrophages; Replication in macrophages; Toll-like receptors detect the PAMPs associated with TB; T_H1 cells (T-Helper 1 lymphocytes) activate bacteriocidal side of macrophages through gamma-interferon; The TH1 response orchestrates the formation of granulomas and caseous necrosis

Question 87

How long does it take in a TB infection before T_H1 lymphocytes are recruited?

Answer 87

About 3 weeks

Question 88

What is primary TB?

Answer 88

Primary tuberculosis is the form of disease that develops in a previously unexposed and therefore unsensitized, person (first exposure of any kind)

Question 89

What is secondary TB? (2 causes)

Answer 89

Secondary tuberculosis is the pattern of disease that arises in a previously sensitized host - Reactivation of a latent infection - Exogenous reinfection

Question 90

Which stages of HIV infection are associated with increased risk of TB?

Answer 90

All of the stages

Question 91

Drainage of TB organisms through the lymphatics to the venous supply will lead to miliary TB in what organ(s)?

Answer 91

The lungs

Question 92

Dissemination of TB organisms through the arterial supply will lead to miliary TB in what organ(s)?

Answer 92

Most prominently the liver, bone marrow, spleen, adrenals, meninges, kidneys, fallopian tubes, and epididymis, but could involve any organ

Question 93

What type of TB infection is more common in countries where bovine TB is present and milk is not pasteurized?

Answer 93

GI TB

Question 94

What type of necrosis is seen in TB patient granulomas? What is the cause?

Answer 94

Causeous; macrophage reaction to the TB

Question 95

What is the name of the 1- to 1.5-cm area of gray-white inflammation as consolidation emerges in a newly infected TB patient?

Answer 95

A Ghon focus

Question 96

What is a Ghon complex?

Answer 96

A combination of the parenchymal lung lesion and nodal involvement (Ghon foci + lymph nodes)

Question 97

What might be an acid-fast cause of disseminated infection in the lungs and/or GI tract that is NOT caused by Mycobacterium tuberculosis? (Mostly in immunosuppressed patients)

Answer 97

Mycobacterium avium complex (MAC)

Question 98

Is leprosy acid-fast?

Answer 98

Yes, it is a mycobacterial infection.

Question 99

Do Mycobacterium tuberculosis or Mycobacterium leprae secrete any exotoxins?

Answer 99

No, their virulence is based on properties of their cell walls.

Question 100

How can M. tuberculosis and M. leprae be diagnosed in similar ways?

Answer 100

PPD (tuberculin) tests in TB; lepromin tests in leprosy

Question 101

What are the two types of M. leprae presentation? What causes the difference?

Answer 101

Tuberculoid (T_H1) and lepromatous (T_H​2); the helper T-lymphocyte response