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Microbiology of Respiratory Infection Flashcards

1
Q

URT defences?

A

Nasopharynx:
Nasal hairs
Ciliated epithelia
IgA

Oropharynx:
Saliva
Sloughing
Cough

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2
Q

Bacteria that colonise the URT?

A

Gram +ve:
α-haemolytic inc. Strep. pneumoniae
β-haemolytic inc. Strep. pyogenes
Coagulase +ve inc. Staphylococcus aureus

Gram -ve:
Haemophilus influenzae
Moraxella catharalis

Many others

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3
Q

Infections in the URT, resulting inflammation and causes?

A 
Sinusitis - paranasal sinuses
Rhinitis - nose
Pharyngitis - pharynx, tonsils, uvula
Epiglottitis - epiglottis, superior larynx
Laryngitis - larynx

May be viral/bacterial and are not always confined to a single structure

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4
Q

Describe acute epiglottitis, what it is and characteristics

A

Inflammation of the epiglottis caused by Haemophilus influenzae type B (HiB)

Children (2-7 yrs) - acute onset (within hours), sore throat, drooling (unable to swallow properly), severe croup/stridor, high temp

Adults - onset is gradual, over days

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5
Q

Risk factors for epiglottitis?

A

Immunocompromised/immunosuppressed

Transmission of capsulated strain to UNVACCINATED HOST

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6
Q

Testing for epigottitis and cautions?

A

Blood culture

NOT A THROAT SWAB - can irritate epiglottis causing spasm and asphyxiation

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7
Q

Treatment of epiglottitis?

A

Tend to be admitted to ITU immediately to get endotracheal intubation
Antibiotics given are CEFTRIAXONE

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8
Q

Describe Haemophilus influenzae and the culture

A

Gram negative coccobacilli and the culture appears very distinctive:
Morphology is pure for Haemophilus species (blood-loving)

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9
Q

What are the conducting airways and describe them in relation to infection?

A 
Trachea and bronchi - not normally colonised and resist infection due to:
Mucociliary escalator
Cough
AMPs
Cellular and humoral immunity
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10
Q

When does infection occur?

A

Changes to airway - trauma/intubation
Abnormalities, e.g: COPD, CF
Inhalation/contact with causative organism

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11
Q

Acute COPD exacerbation symptoms?

A

Adults - productive cough/acute chest illness, breathlessness, wheezing, increased sputum purulence
Often follow a viral infection/fall in temp and increase in humidity (winter)

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12
Q

Acute COPD exacerbation common bacteria and importance when sending to lab?

A

Haemophilus influenzae
Moraxella catarrhalis
Streptococcus pneumoniae

GRAM NEGATIVES and others

Must specify that person has COPD, so lab can look for gram -ve organisms (not normally associated with chest infection)

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13
Q

Describe Moraxella catarrhalis

A

Gram negative diplococci

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14
Q

Testing for cause of infection in COPD?

A

Sputum culture can be combined with clinical evidence:
Sputum purulence
Chest X-ray

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15
Q

Treatment of COPD exacerbation?

A

Only treat if increase in sputum purulence/new chest X-ray changes/pneumonia

1st line - Amoxicillin (aim to cover H. influenzae, M. catarrhalis, S. pneumoniae
2nd line - Doxycycline

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16
Q

What is cystic fibrosis?

A

Inherited disease leading to abnormally viscous mucous, causing blockages of many tubular structures in. conducting airways and lungs

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17
Q

Characteristics of CF?

A

Repeated chest infections and chronic colonisation

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18
Q

Bacteria in CF?

A 
Inefficient clearing of mucous and build-up facilitates bacterial colonisation:
Staph aureus
H. influenzae
Strep pneumoniae
Pseudomonas aeruginosa 
Burkholderia cepacia
Many others
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19
Q

Characteristics of whooping cough?

A 
Acute tracheobronchitis
Cold-like symptoms for 2 weeks
Paroxysmal coughing (2 weeks) 
Repeated, violent exhalations with severe, inspiratory "whoop" (vomiting common) 
Residual cough for 1 month +
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20
Q

Bacteria causing whooping cough?

A

Bordetella pertussis (gram -ve coccobacillus)

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21
Q

Diagnosis of Bordetella pertussis?

A

Not routinely tested for (pernasal swab is unpleasant), so must include clinical signs & symptoms
Bacterial culture - pernasal swab (charcoal), culture (charcoal-blood agar)

PCR - pernasal swab (

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22
Q

Treatment of Bordetella pertussis?

A

Antibiotics:
If less than 1 month - clarythromycin
If older than 1 month - clarithromycin/azithromycin

Pregnancy - erythromycin

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23
Q

Describe the lung defenses

A

Normally “sterile” (URT and conducting airways keep lungs clean)
No ciliary escalator
Alveolar lining fluid - surfactant, Ig, omplement, FFA, AMP
Alveolar macrophages & neutrophils - phagocytosis > inflammatory response

24
Q

Examples of different lung infections?

A

Community Acquired Pneumonia (CAP) - S. pneumoniae, H. influenzae, M. catarrhalis

Atypical pneumonia - Mycoplasma pneumoniae Legionella pneumphilia
Chlamydophila pneumoniae
Chlamydophila psittaci

Others - due to defects in host defense, e.g: hospital acquired pneumonia, immune defects & anatomical abnormalities, like PCP (Pneumocystis pneumonia), fungal and recurrence

TB

25
Characteristics of CAP?
``` ACQUIRED IN THE COMMUNITY (no recent hospital/healthcare exposure): Cough Increased sputum Chest pain Dyspnoea Fever Chest X-ray with infiltrates ```
26
Pathology of CAP?
Organism reaches lungs Immune activation and infiltration (systemic response) Fluid and cellular build up in alveoli - leads to impaired gas exchange
27
Risk factors for CAP?
Increasing age Immunocompormised/immunosuppressed patients Smoker
28
Diagnosis of CAP?
Sputum culture | Viral PCR
29
Treatment of pneumonia?
Streptococcus pneumoniae - sensitive to Amoxicillin, Doxycycline, Co-trimoxazole
30
Describe Legionella pneumoniae
Causes atypical pneumonia and is a common environmental gram -ve bacteria that is also an obligate intracellualr organism (resides with water amoeba that provide nutrients and protection) No person-to-person spread; transmitted by inhalation of contaminated water droplets so can get it from unused shower heads, air conditioning
31
Pathogenesis of Legionella pneumonia?
Invades alveolar macrophages (mistakes them for amoeba) and replicates, causing a flue-like illness that can progress to severe pneumonia
32
Symptoms of Legionella pneumonia?
Mental confusion Acute renal failure GI symptoms Mortality - 5-30%
33
Risk factors for Legionella pneumonia?
Exposure to contaminated aerosolised water Impaired immunity - >55 yrs, diabetic, smoker, malignancy, altered immunity (HIV) CURB65 -
34
Diagnosis of Legionella pneumonia
``` Legionella pneumophila: Legionella urinary antigen - detects serogroup 1 only Culture - slow on selective media Paired serology - rise in titres PCR available from direct sputum ```
35
Treatment of Legionella pneumonia?
Clarythromycin Erythromycin Quinolones, e.g: Levofloxacin
36
Describe Hospital Acquired Pneumonia
Alterations in the normal URT function ``` Caused by: Gram -ve organisms, inc. E. coli, Klebsiella spp. , Pseudomonas spp. CAP organisms S. aureus Anaerobes ``` Broad spectrum of antibiotics given, as more likely that there are gram -ve organisms
37
Describe Pneumocystis pneumonia
AKA PCP Caused by Pneumocystis jirovecii One of the most frequent & severe opportunistic infections in people with weakened immune systems (AIDS, immunosuppression)
38
Pathogenesis of Pneumocystis pneumonia
Inhalation of fungus Normal immune system = asymptomatic carriage/eradication Infections occur in immunocompromised/immunosuppressed
39
Symptoms of Pneumocystis pneumonia?
Fever Dry cough SOB Fatigue HIV- sub-acute, low grade fever > severe pneumonia Non-HIV - more acute, higher fever
40
Diagnosis of Pneumocystic pneumonia?
Microscopy with immunofluorescence PCR BAL (bronchoalveolar) fluid in sputum - can gargle with oral washes
41
Treatment of Pneumocystic pneumonia?
Co-trimoxazole Pentamidine Can be given prophalactically
42
What is aspergillus, what is it caused by and in who?
Fungal chest infection usually caused by Aspergillus fumigatus (common environmental fungus) and inhalation of fungal spores In immunocompromised/suppressed patients - severe pneumonia and invasive disease In immunocompetent patients - localiased pulmonary infection with Aspergilloma (fungus ball) in pre-existing chest cavities (may have previously TB)
43
Diagnosis of Aspergillus?
BAL ideally with fungal culture or PCR | Histopathology of tissue
44
Treatment of Aspergillus?
Amphotericin B Voriconazole Surgery
45
Cause of tuberculosis?
Mycobacterium tuberculosis | Acid/Alcohol Fast Bacilli (thick, waxy coat)
46
Pathogenesis of TB?
Engulfed by alveolar macrophages in alveoli | Resist killing and multiply
47
Characteristics of TB?
90% asymptomatic and develop "LATENT" TB Then, alterations in immune function REACTIVATE TB (active TB) 10% develop immediate active TB
48
Symptoms of TB?
``` Long-term cough Chest pain Sputum +/- haemoptysis Weakness or fatigue Weight loss Fever & chills Night sweats ```
49
Diagnosis of TB?
Microscopy of sputum/tissue Culture on selective media PCR - more expensive but faster than culture (Immune reaction)
50
Describe microscopy for TB
Mycobacterium tuberculosis: Acid Alcohol Fast Bacilli Thick waxy coat Ziehl-Neelsen (ZN) stain: Red-dye (charcoal-fuschin) added to smear and is heated to allow dye to penetrate waxy coat Acid/alcohol added - waxy coat of Mycobacteria retain dye even after exposure to acid/alcohol (non-waxy bacteria, others, do not); usually, means TB Counter stain is added and the mycobacteria appear red
51
Advantages and disadvantages of ZN stain?
Cheap and rapid | No indication of species or sensitivity
52
Describe mycobacterial PCR, dis/advantages?
Directly from sample Results available in 1-2 hours Advantages: Potential for "field testing" (Point of Care testing) Disadvantages: Provides limited species info Provides limited sensitivty results Expensive
53
Describe Mycobacterial culture
Comparatively slow-growing organisms that require specialised media Lowenstein-Jensen (LJ) medium >3 months: Growth characteristics are used to identify the organism (colour, speed, texture, biochemical characteristics) Liquid media >2 months: Faster Further ID by molecular methods
54
Dis/advantages of Mycobacterial culture?
Advantages: High sensitivity and specificity Info on sensitivity Disadvantages - slow
55
Three main routes of transmission?
Contact (touch) - direct (person-to-person: secretion-hand to hand-mucous membrance)/indirect (secretion-hand-object-hand-mucous membrane) thus hand hygiene is important and single rooms are ideal Airborne - small particles (5 microns) fall to floor within 2m and so spread by direct contact with mucous membrane/RT or by indirect contact; single room is ideal

Microbiology (13 decks)

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