Pneumonia

Question 1

Classification of pneumonia

Answer 1

<48h since hospitalisation: CAP
>48h since hospitalisation: HAP/ if ventilated VAP
Special case: pneumonia in immunocompromised hosts

Question 2

Community-acquired pneumonia bacteria

Answer 2

-Most common: streptococcus pneumoniae (G+), haemophilus influenzae (G-)
-Moraxella catarrhalis (G-), Staph aureus (G+), Klebsiella pneumoniae (G-)
-Atypical: mycoplasma pneumoniae

-Less common: legionella pneumophilia (G-), chlamydia pneumoniae (atypical), chlamydia psittaci (atypical), coxiella burnetii (G-)

Question 3

Community-acquired pneumonia viruses

Answer 3

-Highest risk of severe disease in immunocompetent host: SARS-CoV-2, Influenza A and B

-Rhinovirus, adenovirus, respiratory syncytial virus

-Less common: Varicella zoster virus, cytomegalovirus, measles virus

Question 4

Features and diagnosis of C. psittaci

Answer 4

-‘Psittacosis’: zoonotic infection acquired from birds (esp. exotic) e.g. pet shop worker
-Serology

Question 5

Features and diagnosis of M. pneumoniae

Answer 5

-Can occur in epidemics in autumn
-Rare complications: haemolytic anaemia with cold agglutinins; -Stevens-Johnson Syndrome; erythema nodosum; pericarditis;
meningoencephalitis; and Gullaine-Barre syndrome
-CXR can show nodular infiltration rather than consolidation

-PCR (part of viral throat swab)

Question 6

Features and diagnosis of L. pneumophilia

Answer 6

-From contaminated water (showers, inadequately maintained air-conditioning, cooling tanks) - foreign travel/hotels a major risk factor
-Symptoms include headache, confusion, malaise and diarrhoea
-Labs: decreased Na; deranged LFTs; AKI
-Can be severely hypoxic and multi-lobar on CXR

-Specialist sputum testing (PCR)
-Urine antigen

Question 7

Features and diagnosis of L. longbeachae

Answer 7

-Contaminated soil/ compost
-Specialist sputum testing (PCR)

Question 8

Features and diagnosis of C.burnetii

Answer 8

-Q fever: reservoir of bacteria is farm animals
-Serology

Question 9

Features and diagnosis of S. aureus

Answer 9

-Primary pneumonia classically post-influenza virus infection
-May cause lung abscesses. Beware bacteraemia and haematogenous dissemination
-Pneumonia may be secondary bacteraemia/IE, e.g. septic emboli

-Sputum and blood culture

Question 10

Features and diagnosis of Influenza A

Answer 10

-Wide spectrum of illness: uncomplicated illness to life-threatening
pneumonia with ARDS.
-Treat early with oseltamivir in hospitalised patients.

-PCR (viral throat swab), POCT (antigen)

Answer 11

1. 23-valent pneumococcal polysaccharide vaccine
   If increased susceptibility to invasive pneumococcal
   disease:
   =Chronic heart, liver, renal or lung disease
   =Diabetes mellitus
   =Immunosuppression (e.g. splenectomy, AIDS,
   chemotherapy or corticosteroid therapy)
   => 65 years (vaccine given on a one-off basis)
2. Annual influenza vaccine

Question 12

Microbiological investigations in hospitalised patients

Answer 12

-Prior to administration of antimicrobials:
=Sputum culture for conventional bacterial pathogens
=Blood culture, if moderate-severe

-HIV test
-PCR testing for respiratory viruses and M. pneumoniae (red-topped viral throat swab)

Question 13

Microbiological investigations of special circumstances

Answer 13

-Legionella (if severe or risk factors): urine antigen or PCR on LRT specimen e.g. BALF
-If intubated & ventilated: bronchoalveolar lavage (or tracheal aspirate)
-Pleural fluid, if effusion present and suspicion of empyema
-Induced sputum, if investigating for non-conventional pathogens (e.g. TB, Pneumocystis)

Question 14

Late HAP pathogens

Answer 14

GRAM NEGATIVE BACILLI
-E.coli
-P.Aeruginosa
-E.coacae
-K.oxytoca
-S.aureus (MRSA)
-Nosocomial infleunzae virus and SARS-CoV-2 outbreaks