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Upper Respiratory Tract Infections Flashcards

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1
Q

Infectious disease accounts for ___ of DALYs according to the WHO, of which the greatest majority is which type of infection?

A

1/3rd; respiratory tract

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2
Q

Which areas of the respiratory tract contain microbiota?

A

mouth, nasopharnyx, larynx

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3
Q

Which areas of the respiratory tract normally do not have microbiota?

A
  • paranasal sinuses
  • middle ear
  • larynx below the epiglottis
  • trachea
  • bronchi
  • bronchioles
  • alveoli
  • lung tissue
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4
Q

The upper respiratory microbiota contains mainly which type of organisms?

A

anaerobic, mostly strict; generally harmless

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5
Q

Which are the most common upper respiratory microorganisms of healthy people (>50%)?

A
  • viridans streptococci (alpha-haemolytic) in 100%
  • Neisseria species (generally non/low-pathogenic)
  • Corynebacterium (C. diptheriae, C. hominis, non-toxicogenic C. diptheriae)
  • Gram negative anaerobes
  • Haemophilis influenzae (not type B) A, C, D, E, F, non-typable (non-encapsulated)
  • Candida albicans (yeast)
  • Streptococcus pneumonia (15-85%)
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6
Q

viridans streptococci

A
  • commensals (alpha) in 100% of people
  • group of species
  • either alpha or non-haemolytic
  • can cause dental decay by forming plaque of acid-producing bioforms that can erode enamel
  • most important causative organism of infective endocarditis
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7
Q

streptococcus bacteria are

A
  • gram positive cocci (spheres)
  • grow in chains or pairs
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8
Q

staphylococcus bacteria are

A
  • gram postive cocci (spheres)
  • grape-like clusters
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9
Q

neisseria spp

A
  • gram negative diplococci (coffee beans)
  • low-grade/non-pathogenic present in normal URT microbiota
  • high-grade pathogenic forms are N. gonorrhoeae (gonococcus) and N. meningitidis (meningococcus)
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10
Q

Corynebacterium spp

A
  • gram positive rods
  • include:
    • C. diptheriae - non-toxicogenic form is a commensal in URT
    • C. hominis (cardiobacterium?) also in URT
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11
Q

Haemophilis influenzae

A
  • gram negative coccobacillary (intermediate shape, short rods)
  • facultative anaerobes
  • all but type B are common URT commensals in <50% of people
    • A, C, D, E, F, non-typable (either non-encapsulated or non-typable encapsulated); B eradicated w/vaccine in children
    • can cause low grade or serious infections
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12
Q

Candida albicans

A
  • diploid fungus that grows as yeast
  • opportunistic pathogen of URT
    • common commensal in >50% normal people
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13
Q

Streptococcus pneumoniae

A
  • most important respiratory, and human pathogen
  • gram positive cocci
  • alpha-ahemolytic, aerotolerant, aerobic
  • commensal of the nasopharynx of >50% healthy people
    • found in 15-85% of people dependent on population
    • usually higher number serotypes (typically less pathogenic)
  • causes:
    • major cause of pneumonia
      • main cause of community acquired pneumonia (and meningitis) in children and the elderly
    • septicemia in HIV pt
    • bronchitis
    • acute sinusitis
    • otitis media
    • conjunctivitis
    • meningitis
      • most common cause of bacterial meningitis in adults and young adults along with N. meningitidis
    • bactermia
    • sepsis
    • osteomyelitis
    • septic arthritis
    • endocarditis
    • peritonitis
    • pericarditis
    • cellulitis
    • brain abcess
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14
Q

What are the occasional URT microbiota in healthy people (~1-10%)?

A
  • streptococcus pyogenes
    • Group A beta-haemolytic strep
  • N. meningitides (meningococci)
    • ~1% of people
    • may be unencapsulated or less virulent serotypes that do not cause meningitis
    • in outbreak, get high carraige rates (>90%) in close communities, but cases in only ~5% (not known why some are immune)
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15
Q

Streptococcus pyogenes

A
  • gram positive cocci
  • causative agent of Group A strep infections
  • beta haemolytic
  • infrequent, commonly pathogenic commensal of skin and URT (~1-10%)
  • causes:
    • pharyngitis (strep throat)
    • impetigo
    • TSS
    • rheumatic fever auto-immune infection of valves, joints
    • postinfectious glomerulonephritis
  • sensitive to:
    • penicillin
  • resistant to:
    • certain strains: macrolides, tetracylcines, clindamycin
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16
Q

Neisseria meningitidis/meningococcus

A
  • gram negative diplococcus
  • causes meningitis
    • except unencapsulated forms
  • unencapsulated and less virulent serotypres are found in ~1% of normal healthy URT microbiota
  • can have high carraige rates in outbreak (close community) but few incident cases
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17
Q

What are the uncommon URT microbiota in healthy people (<1%)?

A
  • enterobacteria e.g. E. coli
  • Pseudomonas
  • C. diptheriae
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18
Q

Escherichia coli

A
  • gram negative rods
  • facultative anaerobes
  • common in lower intestine commensals
  • uncommon in URT of healthy persons (<1%)
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19
Q

Pseudomonas

A
  • gram negative aerobic bacteria
  • uncommonly found in URT of healthy people (<1%)
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20
Q

Enterobacteria

A
  • gram negative bacteria
  • includes:
    • Salmonella
    • E. coli
    • Yerisinia pestis
    • Klebsiella
    • Shigella
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21
Q

What microorganisms are common in the lungs of healthy persons even though the lungs are considered sterile?

A
  • present in latent state
  • cause bad infections in immunocompromised people
    • Pneumocystis jirovecii (carinii)
    • Mycobacterium tuberculosis
      • mediastinal lymph nodes
    • CMV, HSV, EBV can remain post-infection in lymph nodes and sensory nerves
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22
Q

Pneumocystis jirovecii

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A
  • yeast-like fungus
  • formerly classified as a protozoan (carinii)
  • caustive organism of Pneumocystis pneumonia
    • AIDS-defining illness
  • treated with co-trimoxazole (usually used for bacteria or protozoa, not fungi)
23
Q

Mycobacterium tuberculosis

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A
  • acid-fast bacteria (ZN staining)
  • causitive agent in TB
  • highly aerobic
  • primary pathogen of respiratory system
24
Q

What are the URT infectious syndromes?

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A
  • common cold (rhinovirus)
  • pharyngitis/tonsilitis
  • sinusitis
  • otitis media
  • epiglottitis
  • Croup (laryngeal tracheal bronchitosis (LTB)
    • LRTI but starts in URT
25
Rhinovirus typically causes
* URT infections * e.g. rhinitis, sinusitis, cold, pharyngitis
26
Parainfluenza viruses, H. influenzae, and influenza virus typically cause
* both URT and LRT infections
27
Pertussis typically causes
* LRTI
28
RSV typically causes
* URT, predominantly LRT * causes very few infections in between
29
What are the frequent aetiological agents that cause the common cold?
* rhinovirus * parainfluenza virus * RSV * enterovirus or corona virus - more common in adults, summer
30
What are the frequent aetiological agents that cause pharyngitis/tonsilitis?
* with nasal involvement, exclusively caused by viruses: * adenovirus * enterovirus * parainfluenza virus * influenza virus * \*\***does not rule out Group A strep as a secondary infective agent** * without nasal involvement: * viral (as above) + reovirus * 1/5 cases in children are bacterial: * Group A strep, Group C and Group G * strep pyogenes * can spread, causing cellulitis (face), septicaemia, post-infective complications in rheumatic fever or glomerular nephritis
31
What are the frequent aetiological agents that cause sinusitis?
* primary: viral (part of common cold syndrome) * secondary: H. influenzae, Strept. pneumoniae (less virulent types) * opportunistic URT commensals, take advantage of viral infection
32
What are the frequent aetiological agents that cause otitis media?
* pneumocicci * H. influenzae * M. catarrhalis (URT commensal)
33
What are the frequent aetiological agents that cause epiglottitis?
* H. influenzae type B * more or less eradicated by vaccine
34
What are the frequent aetiological agents that cause Croup (LTB)?
* viral * parainfluenza, influenza A, RSV
35
What is the pathogenesis of the common cold?
\*also applies to many viraul URTI\* * virus is absorbed into the nasal epithelium (sits on BM and lamina propria) * replicates and damages the cells - clear fluid produced from LP (runny nose, sore throat) * inflammatory response follows (highly infective) * phagocytes enter to deal with damaged tisse * commensals take advantage of damaged epithelium * replicate even in presence of phagocytes * more phagocytes enter, fluid becomes purulent (yellow/green) with inflammatory cells * IFN and Ab production clear infection and epithelial damage resolves
36
What is the pathology of otitis media?
* eustachian tubes connect middle ear to pharynx * open on swallowing * especially in babies where the tube is wider and shorter (and they drink on their backs), organisms can then travel from the pharynx to the middle ear * normally, respiratory epithelium pushes organisms back down * if there is a viral infection it is disturbed and cannot trap the organisms
37
How is URTI diagnosed?
mostly clinical
38
When is laboratory diagnosis used in URTI?
* pharyngitis/tonsilitis if possible * epiglottitis whenever possible * uneccessary in common cold * seldom necessary in sinusitus, otitis media, and Croup (LTB)
39
What is the laboratory diagnosis of pharyngitis/tonsilitis?
* requires throat swab (back of throat) * test kits that identify group A strep (antigens) * do them if available
40
What is the laboratory diagnosis of epiglottitis?
* blood culture **not** epiglottis specimen * can exacerbate swelling of epiglottis and obstruct the airway * X-ray (lateral) * do not visualize unless ENT - can cause spasm requiring tracheotomy
41
* Follicular tonsilitis * could be strep (pus), need to assess fever, rash, neck lymph nodes * can take a throat swab * clinical evidence gives little guidance to causative agent
42
* Infectious mononucleosis * present with low grade fever, generally unwell, tired, lethargic * can diagnose on FBC (specific serology for EBV - this is the most common infection of EBV)
43
* diptheria * rare in areas with vaccine * inflammation in throat, palate
44
* herpangina * caused by coxsackie A (enterovirus) * enteroviruses are ssRNA, unenveloped, and live in RT and GIT where they replicate
45
* hand foot and mouth disease * mainly caused by coxsackie virus, or enterovirus 71
46
What is the general treatment of URTI?
* mostly supportive: * fever suppressors * panadol in children * aspirin in adults
47
What is the specific treatment for the common cold?
none
48
What is the specific treatment for pharyngitis/tonsilitis?
* if bacterial (streptococci) can treat with antibiotics
49
What is the specific treatment for sinusitis?
* if bacterial and severe, tx with antibiotics
50
What is the specific treatment for otitis media?
* if less than 2 years old, or prolonged and severe, tx with antibiotics * **children older than 2 tend to have complications with antibiotics and do worse than if they had not been treated** * under 2, immune system is not developed and there is a risk of more serious conditions such as septicemia and meningitis
51
What is the specific treatment for epiglottitis?
* severe bacteria blood infection tf requires treatment (antibiotics)
52
What is the specific treatment for Croup (LTB)?
* usually none; inhaled steroids can be used if severe
53
What are examples of viral respiratory tract infections?
* common cold (rhinovirus) * sore throat (pharyngitis) * sinusitis * laryngitis * Croup * acute bronchitis * bronchiolitis * influenza * SARS * MERS
54
Most RTIs are caused by
viruses and tf do **not** respond to or require antibiotics

Respiratory Microbiology (3 decks)

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