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Clinical Micro > Lecture 4 LRTI > Flashcards

Lecture 4 LRTI Flashcards

1
Q

How may deaths on a global scale are caused by LRTI

A

Approx 4 million

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2
Q

What is the difference between acute and chronic LRTI considering symptom appearance after infection

A

Acute is sudden onset within days

Chronic can be a few weeks or months before symptoms

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3
Q

What percentage of population carry s pneumoniae transiently in URT -

A

Approx 10%

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4
Q

Name some acute LRTI

A 
Pneumonia 
Bronchitis 
Bronchiolitis 
Legionnaires disease
Whooping cough
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5
Q

Name some chronic LRTI

A

Tuberculosis
Aspergillosis
Cystic fibrosis

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6
Q

Which microorganism causes bronchitis (inflammation of trachea-bronchial tree)?

A

Almost always viral such as adenovirus

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7
Q

What age group does bronchiolitis occur in and what is the microorganism which predominantly causes the disease

A

Under 2 yrs as lungs underdeveloped

RSV

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8
Q

How can legionnaires be controlled

A

Decent chlorination of water - associated with water and ventilation systems.

Flush taps once weekly for 2 mins to flush out in dead legs.

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9
Q

What microorganism primarily causes legionnaires disease

A

L. Pneumophila (over 90% of cases)

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10
Q

L pneumophila is a GPR true or false

A

False. It is a GNR

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11
Q

Which type of patient will become infected with aspergillosis

A

Immunocompromised breathe in spores and get aspergilloma.

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12
Q

Which microorganisms primarily cause infections in cystic fibrosis patients

A

S aureus and P aeruginosa

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13
Q

Pneumonia can be caused by fungi, bacteria, viruses AND parasites. True or false

A

True!!

Parasites - ascaris lumbracoides

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14
Q

What are the two types of acquired pneumonia

A

Community acquired pneumonia (CAP)

Hospital acquired pneumonia (HAP)

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15
Q

How many people die in pneumonia in the uk per year (approx)

A

30,000

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16
Q

The symptoms of pneumonia often depend on what

A

What agent has caused the disease, e.g bacterial can have different symptoms to viral

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17
Q

Name some risk factors for CAP

A

Smoking, pet birds such as parrots, elderly/young, alcoholics/homeless, underlying illness e.g. CF

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18
Q

What is aspiration pneumonia

A

Aspiration = sedated patents e.g alcoholics, patient breathe in gastric juices and take mouth flora and this juice into lungs and cause pneumonia

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19
Q

What is recurrent pneumonia

A

Recurrent = 2 episodes of pneumonia a year for an adult with a clear x ray of chest between each case (children is 3 cases),

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20
Q

What is the definiton of CAP

A

Develop in patient that has had no hospital contact

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21
Q

What is the definiton of HAP

A

Pneumonia present in a patient 48-72hrs AFTER being admitted to hospital.

Prior to 48hrs suggest community acquired.

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22
Q

Every year what % of uk adults will have CAP

A

0.5%-1%

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23
Q

How many patients presenting to their GP with LRTI symptoms are diagnosed with CAP

A

5-12%

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24
Q

How many of the 5-12% of patients diagnosed by a GP with CAP are admitted to hospital

A

22-42% a

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25
Q

What are the signs (NOT SYMPTOMS) of typical pneumonia

A

Cough, cyanosis (blue fingertips), tachypnoea (rapid breathing), tachycardia

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26
Q

What are the symptoms (NOT SIGNS) of typical pneumonia

A

Fever, muscle aches, shakes/rigors, dyspnoea (shortness of breath), sputum production (consolidation material in lungs) which is RUST COLOURED

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27
Q

Why is sputum from typical pneumonia rust coloured

A

Due to blood - fresh blood and old lysed blood cells.

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28
Q

Which microorganism are associated with typical CAP

A

Most common: streptococcus pneumoniae
Less common: Haemophilus influenzae (live in URT)
S aureus (CF)
P aeruginosa (CF)

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29
Q

Which microorganism is one of the main. Causes of respiratory tract infections worldwide

A

S pneumoniae

Kill over 1 mil individuals every year

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30
Q

What are the signs (NOT SYMPTOMS) of ATYPICAL pneumonia

A 
Rash 
Cyanosis 
Tachypnoea 
Tachycardia
Dry cough
31
Q

What are the SYMPTOMS (NOT SIGNS) of Atypical pneumonia

A 
Headache 
Confusion 
Diarrhoea 
Incontinence 
NO SPUTUM - NON RESPIRATORY
32
Q

Which microorganisms are most commonly associated with ATYPICAL CAP

A

Most common; mycoplasma pnuemoniae
Less common bacteria; legionella pneumophila
Chlamydophila psittaci (psittacosis)
Chlamydophila pneumoniae

Virus causing: Influenza A/B, Rhinovirus, RSV

33
Q

How does the consolidation in lungs differ between typical and atypical pneumonia

A

Typical - widespread consolidation - lots of pathogens and inflammatory cells.

ATYPICAL - patchy consolidation - not much inflammatory material in lungs so dont produce sputum

34
Q

Describe s pneumoniae morphology

A

Diplococcus (not normal chains) and lancet shape

35
Q

Describe the morphology of mycoplasma pneumoniae

A

No cell wall so pleomorphic - can use beta lactams

36
Q

Which risk groups for CAP will typically display ATYPICAL pneumonia ONLY. Name the microorganisms involved which each group.

A

Smokers/travel abroad - L. Pneumophila (legionnaires)

Contact with birds (Cl. Psittaci)

37
Q

Which risk groups for CAP will typically display TYPICAL pneumonia ONLY. Name the microorganisms involved which each group.

A

Alcoholics/homeless - S. Pneumoniae

Underlying illness e.g. CF - P aeruginosa , S aureus

38
Q

Which risk groups for CAP will typically display ATYPICAL pneumonia AND typical pneumonia. Name the microorganisms involved which each group.

A

Elderly/young - S. Pneumoniae for typical, M pneumoniae for ATYPICAL

39
Q

Pneumonia is the 3rd most common HAI at 23%, T or F.

A

True

40
Q

Typical/ Atypical symptoms are only present in CAP. T or F

A

False. It is for both HAP and CAP.

41
Q

Name some risk factors for HAP

A

1- ventilatory support - patients may get endotracheal tube put in URT if have breathing difficulties. Can get contamination from poor hygiene e.g. Klebsiella pneumoniae and Pseudomonas aeruginosa.
2-immunosuppression : organ transplantation, aspergillus fumigatus
3- immobility and vomiting - aspiration pneumonia, oral bacteria e;.g anaerobic bacteria

42
Q

Define VAP

A

Ventilation associated pneumonia (VAP) 48 hour after ventilation

43
Q

What is the treatment regimen for uncomplicated CAP

A

Amoxicillin or erythromycin. Due to resistance now moxifloxacin (4th gen quinolone act on DNA gyrase). 1 tablet a day.

44
Q

What is the treatment regimen for severe CAP of unknown aetiology (cause)

A

Cefuroxime (beta lactam) + erythromycin for mycoplasma

45
Q

What is the treatment regimen for atypical pneumonia (CAP/HAP)

A

Erythromycin

46
Q

What is the treatment regimen for HAP

A

Cefotaxime +/- Gentamicin

Cefotaxime is high gen cephalosporin, gentamicin toxic to humans so need to dose appropriately to kill microbe but not to damage kidneys and ears

47
Q

Why is S pneumoniae capsule a major virulence factor

A

Anti-phaocytic - prevent c3b adhesion to cell wall

92 different capsular types (differnt serotypes) but 90% of pneumonias are caused by about 23 serotypes (PPSV23 vaccine)

48
Q

Describe the cell wall of S pneumoniae

A

Gram positive cell wall, 6 layers of peptidoglycan with covalently bound teichoic acid and cell membrane anchored lipoteichoic acid (forssman antigen)

49
Q

Why does s pneumoniae spread in crowded settings such as hospitals, prisons or day care centres

A

Respiratory droplets via person to person horizontal spread

50
Q

What is the serotyping that can be performed using a homologous antibody for capsule of S pneumoniae

A

Quellung reaction

51
Q

State a major adhesion mechanism of s pneumoniae

A

CbpA adhesin - functions as cell- surface adhesin interacting with carbohydrates on pulmonary epithelial surface in nasopharynx.

52
Q

State the importance of CbpA as a virulence factor

A

functions as cell- surface adhesin interacting with carbohydrates on pulmonary epithelial surface in nasopharynx.

Also shown to be bound to secretory component of IgA and complement component C3.

53
Q

What mechanisms does s pneumoniae use to evade the immune system

A

PspA (protective antigen) inhibits complement mediated opsonisation of pneumococci just like capsule.

IgA1 protease: cleaves IgA1 at the hinge region the principal immunoglobulin isotope for the respiratory tract. It also cleaves a neuraminidase that cleaves sialic acid from glycoconjugates which uncovers epitopes for pneumococcal adherence.

54
Q

What toxin release mechanisms does s pneumoniae have

A

Autolysins LytA, LytB, LytC & Pneumolysin

55
Q

What is the role of pneumolysin

A

Pneumolysin - toxin released during autolysis (cell lysis) by LytA (extra reading); inhibit neutrophil chemotaxis, phagocytosis, lymphocyte proliferation and immunoglobulin synthesis

Toxin is important in causing meningitis as it damages ependymal cilia that line the ventricles of the brain and induces brain cells to undergo apoptosis

56
Q

What do the autolysins do

A

Autolysins LytA, LytB, LytC - break peptide cross linkingin cell wall peptidoglycan which releases cell wall components; massive inflammation and pneumolysin release

They have been suggested to have a role in bacterial uptake of DNA and daughter cell separation (extra reading)

57
Q

H202 produced by pneumococcus is a potent __?

Fill in the blank

A

Haemolysin

58
Q

When are LytA, LytB and LytC released by s pneumoniae

A

During the stationary phase of growth - peptidoglycan and capsular material released into blood stream and get inflammation.

Bacterial growth has logarithmic, stationary and decline phase of growth

59
Q

What is the role of teichoic acid (extra)

A

Adhesin (binds fibronectin), immunomodulatory

60
Q

Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.

What is the likely diagnosis and microorganism to blame

A

Community associated pneumonia with typical presentation

Streptococcus pneumonia or possibly haemophilus influenzae

61
Q

Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
What samples should be taken, when and why?

A

Sputum early morning before breakfast to prevent food contamination and to get build up of bacteria and inflammatory material overnight

Urine sample

62
Q

Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
What tests would be performed on sputum sample

A

Gram stain and culture

63
Q

Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.

What test would be performed on Urine sample

A

Antigen detection (rapid pneumococcal antigen test) to detect the capsular antigen.

64
Q

Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.

What agar would be used to culture the sputum sample and what must be done to the sputum before plating

A

Sputum must be combined with sputolysin (N-acetylcysteine) which breaks down the sputum to a more watery form and release microorganisms stuck in mucus.

Blood agar + optochin disc
Chocolate agar

65
Q

Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
Why is a optichin disc added to the agar plate for culture?

A

S pneumoniae is sensitive to it so get a clear zone if present

66
Q

Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
What are the safety considerations to be made when culturing and handling the sample

A

S pneumoniae is cat 2 pathogen

Sputum sample is cat 3 laboratory with class I safety cabinet

67
Q

What is important about Class I safety cabinet

A

Negative pressure, air flow away from worker.
0.74m^3/sec air flow rate

Hepa filter

68
Q

Describe the basic and full identification process used for s pnuemoniae

A

Basic : colony appearance (alpha haemolytic) so get green colonies, 1mm in diameter. Capsular producing strains may look mucoidal on agarose especially if grownunder anaerobic conditions

Full ID: Optochin sensitivity - large zone approx 16mm of inhibition around disk, distinguish it from other oral streptococci

69
Q

Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
What non culture techniques will be performed on the urine sample

A

Immunochromatographic assay/lateral flow assay
Rabbit anti strep pnuemoniae bound to nitrocellulose membrane, urine added to test well and read result in 15 mins (similar to pregnancy test, line in control and test = positive, line in control but not test is negative).

70
Q

What does the poor sensitivity (86%) of the lateral flow assay mean when given a negative result

A

Doesn’t necessarily mean there is an infection as poor sensitivity.

71
Q

What antibiotic treatment is recommended for s pnuemoniae infection

A

Moxifloxacin (flouroquinolones are active against bacteria)

72
Q

What % of S pnuemoniae is resistant to penicillin?

A

50%

73
Q

What % of s pnuemoniae is multidrug resistant (to macrolides, tetracycline, etc)

A

25%

74
Q

What are the two vaccinations against z pnuemoniae

A

PPSV23 - for at risk patients, 23 valent pnuemococcal polysaccharide vaccine (not hugely effective)

PCV13 - for children under 2 yrs. Prevent other infections that s pnuemoniae may cause

Clinical Micro (9 decks)

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