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Mechanisms of Microbial Disease > Chapter 12 > Flashcards

Chapter 12 Flashcards

1
Q

What are the parts of the upper respiratory tract?

A

Epiglottis, larynx, nasal cavity and pharynx

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2
Q

What is the preferred area of infection for coronaviruses and rhinoviruses?

A

Nasopharynx

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3
Q

What types of respiratory infections are restricted to the surface?

A

Common cold, influenza, streptococci in throat, chlamydia, diphtheria, pertussis and thrush

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4
Q

What is the common cold (rhinitis) caused by?

A

Many different types of viruses, mostly rhinovirus and coronaviruses

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5
Q

What are characteristics of pathogens that are good at infecting the respiratory tract?

A

less than 5 microns (very small, aerosoluble), Gram + so it doesn’t clump together
Adhesion to normal mucosa, interfere with cilia, resist destruction by macrophages, damage local tissues

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6
Q

What does it mean to be a secondary invader?

A

Infect when host defences are impaired

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7
Q

What types of respiratory infections spread throughout the body?

A

Measles, mumps, rubella, EBV, CMV

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8
Q

How is the common cold transmitted?

A

Aerosol or virus contaminated hands

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9
Q

What is a symptom of the common cold?

A

A flow of virus rich fluid (rhinorrhea) from the nasopharynx (if green, bacterial infection), sneezing

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10
Q

How can we treat the common cold?

A

Self-limiting, symptomatic treatment. No vaccine due to antigenic diversity of viruses

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11
Q

What makes a professional invader?

A

The ability to infect a healthy respiratory tract. Opens up the tract to secondary infection

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12
Q

What are pharyngitis and tonsillitis caused by?

A

70% by viruses like adenovirus, Epstein-Barr virus and cytomegalovirus
Bacterial by S. pyogenes (white pustules in pharynx)

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13
Q

What is cytomegalovirus (CMV) infection characterized by?

A

Multinucleated cell formation and/or intranuclear inclusion in humans

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14
Q

How does EBV infection progress?

A

Immunologically mediated
Virus replicated in epithelial cells and B lymphocytes (CD21), spreads to B cells in local lymphoid tissues (lymph nodes and spleen) and the T cells respond to the infected B cells

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15
Q

What is the clinical presentation of EBV infection?

A

Infant/young child show no clinical disease
Young adults get infectious mono/glandular fever 4-7 weeks after initial infection, fever, sore throat, petechiae (red spots) on hard palate enlarged lymph nodes, hepatitis
Spontaneous recovery but saliva will be infectious for months and remain latent

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16
Q

Where does CMV localize?

A

In the epithelial cells of salivary glands (saliva), kidney (urine), cervix (secretions) and testes (semen) and will shed for months

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17
Q

How does CMV become a successful pathogen?

A

Poor target for cytotoxic T cells as they interfere with transport of MHC-1 molecules to cell surface and induce expression of Fc receptors on cell surface

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18
Q

What are the symptoms of CMV infection?

A

Infant/child will show no symptoms
Adolescents will have a glandular fever-type illness (fever, lethargy, abnormal lymphocytes, mono)
Adults will have mild illness
Primary infection during pregnancy will spread to fetus and reactivate causing mental retardation in the baby.

19
Q

What causes mononucleosis?

A

Epstein-Barr Virus (EBV) from exchange of saliva

20
Q

Which age groups are most susceptible to EBV?

A

1-6 years and 14-20 years

21
Q

What are the symptoms of bacterial pharyngitis?

A

Sore, red throat, difficulty swallowing, sudden fever, scarlet fever (sandpapery rash, strawberry tongue, systemic)

22
Q

What are some complications of s. pyogenes?

A

Rheumatic heart disease, acute glomerulonephritis (circulating immune complex deposits in glomeruli, activating complement and coagulation systems, infalmmation, blood in urine) and rheumatic fever (fever, joint pain, swelling)

23
Q

What are the symptoms of EBV infection?

A

Cytokine release, the infected B cells become polyclonally activated and produce autoantibodies (IgM, erythrocytes)

24
Q

How does infection with the mumps virus progress?

A

Virus goes into lymph nodes, spreads via circulatory system to salivary glands, ovaries
Long incubation time
Recovery in one week with lifelong immunity

25
Q

What are the cancers associated with EBV? What are their co-carcinogens?

A

Burkitt’s lymphoma in Africa and Papua New Guinea. Co-carcinogen with malaria (weakens T-cell control of EBV infection)
Nasopharyngeal carcinoma in China and SE Asia. Co-carcinogen is ingested nitrosamines (preserved fish)

26
Q

What causes bacterial pharyngitis?

A

Streptococcus pyogenes

27
Q

How is bacterial pharyngitis treated?

A

Penicillin unless resistance is presence. Vaccine available

28
Q

What causes parotitis (inflammation of parotid glands-largest salivary glands)?

A

Mumps virus spread by airborne droplets and close contact

29
Q

How do infection with the mumps virus progress?

A

Recovery in one week with lifelong immunity

30
Q

What are some complications of the mumps virus?

A

Meningitis, encephalitis, pancreatitis and hearing loss

31
Q

What is the vaccine for mumps virus?

A

MMR

Autism controversy

32
Q

What is otitis media (middle ear infection) caused by?

A

50% viral
S. pneumoniae, H. influenzae, S. pyogenes, M. catarrhalis, S. aureus
The outcome of a respiratory tract infection

33
Q

Who is otitis media most commonly found in?

A

Preschool age patients due to wider Eustachian tube

34
Q

What are the clinical manifestations of otitis media?

A

Early in children with have fever and irritability

Late infection has ear pain, changes in hearing and purulent discharge (accumulation of fluid and inflammation)

35
Q

What are some complications of otitis media?

A

Tympanic membrane damage leading to hearing loss

36
Q

How is otitis media treated?

A

Using empirical therapy. Wait for 1 week before giving antibiotics in case it may be viral

37
Q

How is a pathogen successful in causing otitis media?

A

Avoids cleansing by the epithelial cilia

38
Q

What is otitis externa caused by?

A

Different pathogens from otitis media, similar flora to skin

Staphylococcus aureus, Candida albicans, Pseudomonas aeruginosa

39
Q

What is otitis externa treated by?

A

Antibiotic ear drops

40
Q

What is acute sinusitis caused by?

A

Similar pathogens to otitis media

Prolonged RTI

41
Q

What are the symptoms of acute sinusitis?

A

Facial pain, purulent nasal discharge, fever

Headache and upper teeth pain in maxillary sinusitis

42
Q

What are the complications of acute sinusitis?

A

Orbital cellulitis, osteomyelitis, meningitis, brain abscess

43
Q

What causes epiglottitis?

A

H. influenzae

44
Q

What are the clinical manifestations of epiglottitis?

A

Edema and inflammation of the epglottis causing airway blockage
Medical emergency

Mechanisms of Microbial Disease (17 decks)

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