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Respiratory: Microbiology > Respiratory Tract Microbiology > Flashcards

Respiratory Tract Microbiology Flashcards

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Biology 101 flashcards
1
Q

What is the difference between colonisation and infection?

A
  • Infection - inflammation as a consequence of the pathogen

* Colonisation - presence of pathogen, may not suffer from disease

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2
Q

What are host defences of the upper respiratory tract?

A

Nasopharynx

  • Nasal hairs
  • Ciliated epithelia
  • IgA

Oropharynx

  • Saliva
  • Sloughing
  • Cough
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3
Q

What is sinusitis?

A

Inflammation of paranasal sinuses

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4
Q

What is rhinitis?

A

Inflammation of nose

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5
Q

What is pharyngitis?

A

Inflammation of pharynx, tonsils, uvula

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6
Q

What is epiglottitis?

A

Inflammation of epiglottis, superior larynx

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7
Q

What is laryngitis?

A

Inflammation of the larynx

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8
Q

What are some gram positive upper respiratory tract colonisers?

A
  • α-haemolytic streptococci (Strep pneumoniae)
  • ß-haemolytic streptococci (Strep pyogenes)
  • Staphylococcus aureus
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9
Q

What are some gram negative upper respiratory tract colonisers?

A
  • Haemophilus influenzae

* Moraxella catarrhalis

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10
Q

What colour will haemophilia influenzae appear on a gram stain?

A

Pink - it is gram negative

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11
Q

What shape of bacterium is H.Influenzae?

A

Coccobacilli

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12
Q

What is moraxella catarrhalis?

A

A gram negative coccus

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13
Q

What are host defences of the conducting airways?

A
  • Mucocilliary escalator
  • Cough
  • Antimicrobial peptides
  • Cellular and humoral immunity
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14
Q

When does infection of the conducting airways occur?

A

Infections occur when there are changes

  • Trauma/intubation of airway
  • Abnormalities of defence e.g. cilliary escalator as occurs in COPD/CF
  • Virulent pathogen/large inoculum
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15
Q

How can intubation lead to infection of the conducting airways?

A

Inhibits the final stage of the cilliary escalator - prevents the expulsion of mucous and foreign material from being swallowed or coughed up

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16
Q

What are the clinical presentations of acute bronchitis?

A
  • Infection & inflammation of the bronchi
  • Productive cough
  • Wheeze
  • Fever
  • Normal chest examination & CXR
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17
Q

What are the microbiological features of acute bronchitis?

A
  • 90% viral
  • Preceded by URT infection

(Acute bronchitis is an infection of the conducting airways)

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18
Q

What I the treatment for acute bronchitis?

A

Antibiotics not usually indicated

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19
Q

What are the clinical presentations of acute exacerbations of chronic obstructive pulmonary disease?

A
  • Productive cough or acute chest illness
  • Breathlessness
  • Wheezing
  • Increased sputum purulence
  • Exacerbations often follow bacterial/viral infection or fall in temp & increase in humidity (i.e. Winter)
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20
Q

What pathogens can cause acute exacerbations of COPD?

A
  • Haemophilus influenzae
  • Moraxella catarrhalis
  • Streptococcus pneumoniae
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21
Q

What percentage of acute COPD exacerbations are caused by viruses?

A
  • 30% - viral
  • 50% - bacterial
  • 20% - unknown
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22
Q

What is purulent sputum?

A

Typically yellow or green - contains pus, composed of white blood cells, cellular debris, dead tissue, serous fluid, and mucus

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23
Q

What is pertussis?

A

Whooping cough - acute trachea-bronchitis

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24
Q

What are the symptoms of pertussis?

A
  • cold like” symptoms for two weeks
  • paroxysmal coughing (2 weeks)
  • repeated violent exhalations with severe inspiratory “whoop”
  • vomiting common
  • residual cough for month or more
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25
Q

What pathogen causes pertussis?

A

Bordetella pertussis

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26
Q

What are the features of bordetella pertussis?

A
  • Gram negative coccobacillus
  • Exclusively human pathogen
  • Vaccine preventable
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27
Q

In what time frame is bordetella pertussis contagious?

A
  • From the period where symptoms start

* To over 2 weeks

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28
Q

How long after exposure to bordetella pertussis do symptoms start?

A
  • 7-10 days is typical range

* But can range from 4-24 days

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29
Q

How is bordetella pertussis diagnosed?

A

Bacterial culture

  • Pernasal swab (<21 days)
  • Culture (charcoal-blood agar)

PCR
* Pernasal swab (<21 days)

Serology (paired sera)

Clinical signs and symptoms (low numbers of organisms by onset of paroxysmal cough)

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30
Q

What is the treatment for bordetella pertussis?

A

Treatment with Antibiotics if <21 days cough

after 21 days, post-infective cough - not caused by pathogen

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31
Q

What are the 3 main routes of disease transmission?

A
  • Contact (touch)
  • Airborne
  • Droplet
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32
Q

What are the airborne precautions to reduce transmission of infectious diseases?

A
  • Wash hands before entering and leaving room
  • PPE (filtering face piece 3 - FFP3)
  • Keep in door closed
  • Dispose of/decontaminate all equipment used before leaving
  • Dispose of FFP3 after leaving
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33
Q

Why do airborne diseases have a large spread?

A
  • Small particles (<5 microns) can travel long distances and remain airborne
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34
Q

What diseases are airborne?

A
  • Multi-drug resistant TB
  • some viruses
  • RTI undergoing aerosol generating procedures
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35
Q

What are droplet precautions?

A
  • Wash hands before entering and leaving room
  • PPE
  • Keep door closed
  • Dispose of/decontaminate all equipment used before leaving
36
Q

Why do droplets have less spread than airborne diseases?

A

Larger particles > 5 microns, fall to the floor within 2m

37
Q

How are droplet diseases spread?

A
  • Direct contact of droplets with mucous membranes

* Droplet > surface > contact spread

38
Q

What is cystic fibrosis?

A

Inherited disease leads to abnormally viscous mucous – blockages of many tubular structures including conducting airways & lungs

39
Q

What are the clinical features of cystic fibrosis?

A

Repeated chest infections & chronic colonisation

40
Q

What are the microbiological features of cystic fibrosis?

A
  • Inefficient clearance and build-up of mucus
  • Staph aureus
  • Haemophilus influenzae
  • Strep pneumoniae
  • Pseudomonas aeruginosa
  • Burkholderia cepacia
41
Q

Is cystic fibrosis caused by pathogens?

A

No, it is a host defence problem - cannot clear phlegm

42
Q

What are host defences of the lower respiratory tract?

A
  • No ciliary escalator
  • Alveolar lining fluid - surfactant, Ig, complement protein, free fatty acids, antimicrobial peptides
  • Alveolar macrophages
43
Q

What are the clinical features of community acquired pneumonia?

A
  • Cough
  • Increased sputum
  • Chest pain
  • Dyspnoea
  • Fever
  • CXR with infiltrates
44
Q

Explain the pathology of community acquired pneumonia?

A
  • Organism reaches lungs
  • Immune activation & infiltration (systemic response)
  • fluid & cellular build up in alveoli leads impaired gas exchange
45
Q

What are the causative organisms of community acquired pneumonia?

A
  • Streptococcus pneumoniae - 70%
  • Atypicals/viruses - 20%
  • Haemophilus influenzae - 5%
    Staphylococcus aureus - 4%
  • Other bacteria - 1%
46
Q

What are the risk factors of community acquired pneumonia?

A
  • Increasing age
  • Immunocompromised/suppressed patients
  • Smoking
47
Q

How is community acquired pneumonia diagnosed?

A
  • Sputum culture
  • Purulence
  • Viral PCR
48
Q

What does a sputum culture show in community acquired pneumonia?

A 
* Gram stain sputum -
 pus cells, 
Gram pos/neg cocci/bacilli
* Culture on blood agar - alpha haemolysis 
(partial haemolysis, where
the organism grows blood agar
becomes green-brown colour)
49
Q

What is used to treat pneumonia caused by streptococcus pneumoniae?

A

Sensitive to amoxicillin, doxycycline and co-trimoxazole (if allergic to penicillin, doxycycline used)

50
Q

What types of infections can be caused by streptococcus pneumoniae in children?

A
  • Ear infection
  • Sinus infection
  • Upper respiratory tract infection
51
Q

What types of infections can be caused by streptococcus pneumoniae in the immunosuppressed?

A

Can spread to blood stream and cause pneumococcal disease

52
Q

What is pneumococcal disease that spreads to the blood stream referred to as?

A

Invasive pneumococcal disease

53
Q

Why is the PCB vaccine so important?

A

Pneumococcal vaccine reduces cases by 76%

54
Q

Why is pneumonia such a significant disease?

A

It is the world’s biggest killer of children

55
Q

What are the different types of pneumonia?

A
  • Acute and chronic
  • Typical (step pneumoniae) and atypical (Mycoplasma pneumoniae , Legionella pneumonia, Chlamydophila pneumonia, Chlamydia psitacci, etc)
  • Hospital acquired and community acquired
  • Aspiration pneumonia (when food, saliva, liquids, or vomit is breathed into the lungs)
  • Pneumonia in the immunosuppressed/special populations
56
Q

How is severity of pneumonia graded?

A

CURB65

57
Q

What is legionella pneumonia?

A

Atypical pneumonia

58
Q

How is legionella pneumonia diagnosed?

A
  • Legionella urinary antigen (detects serogroup 1 only)
  • Culture - slow on selective media
  • Paired serology
  • PCR available direct from Sputum
59
Q

What is the treatment for legionella pneumonia AKA Legionnaires’ disease?

A
  • Clarythromycin
  • Erythromycin
  • Quinolones (e.g. levofloxacin)
60
Q

Why are quinolones not used for treatment of Legionnaires’ disease unless very serious?

A

One of the 4C’s - can cause C.difficile infection

61
Q

What are characteristics of Legionella pneumophila?

A
  • Common environmental Gram-negative bacteria (unusual cell wall structure)
  • Obligate intracellular organism
  • Resides with water amoeba – provide nutrients & protection
62
Q

Describe the pathogenesis of legionella pneumophila?

A

Invades alveolar macrophages & replicates

63
Q

What are the clinical features of legionella pneumonia?

A
  • Flu-like illness which may progress to severe pneumonia
  • Mental confusion
  • Acute renal failure
  • GI symptoms
64
Q

What is the mortality of Legionnaire’s disease?

A

5-30%

65
Q

What is the epidemiology of Legionella Pneumophila?

A
  • No person-to-person spread

* Transmitted by inhalation of contaminated water droplets

66
Q

What are the risk factors for Legionella pneumonia?

A
  • Exposure to contaminated aerosolised water

* Impaired immunity - >55YO, diabetes, smoking, malignancy, altered immunity

67
Q

What is the treatment of Legionnaires’ disease?

A
  • Antibiotics
  • No vaccine available
  • Water supply systems should be cooled below 20oC or heated above 60oC
68
Q

What is walking pneumonia?

A

Atypical pneumonia - caused by mycoplasma pneumoniae

69
Q

What is the treatment for mycoplasma pneumonia/walking pneumonia?

A

Organism has no cell wall so amoxicillin is not the treatment of choice

70
Q

What are the clinical features of walking pneumonia?

A

Target lesion (erythema multiformae) - walking pneumonia is most common cause of this rash

71
Q

What are risk factors for staphylococcus pneumonia?

A
  • Influenza infection

* Haematogeneous spread (normally related to drug use)

72
Q

Why is staph pneumonia particularly necrotic?

A

PVL (Panton–Valentine leukocidin) toxin produced by staph aureus

73
Q

What are the characteristics of a CXR of someone with staphylococcus pneumonia?

A

Septic emboli caused by staph aureus

74
Q

What is relative bradycardia?

A

Increase in heart rate of 10 beats per degree rise in temperature

75
Q

What diseases in relative bradycardia shown in?

A
  • Mycoplasma pneumoniae
  • Legionella pneumonia
  • Chlamydia psitacci
76
Q

What is treatment for mild/mod CAP?

A

Amoxicillin (5 days)

77
Q

What is treatment for mild/mod CAP if penicillin allergic?

A

Doxycycline

78
Q

What is treatment for severe CAP?

A

Co-amoxiclav + doxycycline

79
Q

What is treatment for severe CAP if penicillin allergic?

A

IV levoflaxin (quinolone)

80
Q

What is treatment for mild/mod HAP?

A

Amoxicillin + metronidazole (5 days)

81
Q

What is treatment for mild/mod HAP if penicillin allergic?

A

Co-trimoxazole + metronidazole

82
Q

What is treatment for severe HAP?

A

Iv amoxicillin + metronidazole + Gentamicin

83
Q

What is treatment for severe HAP if penicillin allergic?

A

IV co-trimoxazole + Metronidozole + Gentamicin

84
Q

What is the microbiology of hospital acquired pneumonia?

A
  • 60% gram negative
85
Q

What are other causes of pneumonia?

A
  • Parasites (Ascaris, Schisto, Dirofilaria etc)
  • Brucella
  • Endemic mycoses
  • Psittacosis
  • tuberculosis

Respiratory: Microbiology (1 decks)

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