RTI Clinical

Question 1

Lobar pneumonia

Answer 1

Lobar: Streptococcus pneumoniae

Physical exam

• Bronchial breath sounds
• Tactile fremitus
• Dullness to percussion
• Consolidation
• Effusion
• Rust-colored sputum
• “hepatization”

Question 2

Interstitial (“atypical”) pneumonia

Answer 2

• Viral
• Legionella
• Mycoplasma
• Chlamydia

Physical exam

• Crackles
• Wheezes
• may not reveal consolidation

Sx

• Young, healthy patients
• Gradual in onset with constitutional symptoms:
• Malaise, fatigue, myalgia, headache
• Non-productive cough
• Fever
• Self-resolving; rarely needs treatment

Dx: X-ray presents a diffuse pattern

Question 3

COMMUNITY-ACQUIRED (CA) PNEUMONIA

Answer 3

CA-pneumonia in Ambulatory Pt:

• M. pneumoniae
• Respiratory virus
• S. pneumoniae

CA-pneumonia in Hospitalized Pt

• S. pneumoniae
• Legionella
• GNB
• MRSA

Question 4

Lung Abscess

Answer 4

• Usually polymicrobial
• Staphylococcus aureus
• Aerobic and anaerobic Streptococci
• Aerobic gram negative rods
• Anaerobic gram negative rods: Bacteroides,Fusobacterium,Peptostreptococcus

Question 5

Legionella

Answer 5

• Gram-ve but better visualised w silver stain
• Oxidase +

Clinical presentation Legionnaire’s disease

• Productive cough
• Purulent sputum
• No organisms on gram stain
• Systemic illness Triad: GI, neuro, resp
• GI-diarrhea
• Neurologic: headache, confusion, delirium
• Pulm: patchy infiltrate w consolidation on 1 lobe
• Hyponatremia
• high fever

Clinical presentation Pontiac fever

• fever & malaise

Risk factors

• Smoking
• COPD
• ↑ age
• ETOH
• Exposure to environmental water sources

Dx:

• Culture – Buffered charcoal yeast extract (BCYE) agar
• Growth requires iron & cysteine
• Urine antigen rapid
• Reportable: Yes
• Human-to-human transmission: No

Rx:

• Macroglide
• Fluoroquinolones

Question 6

BORDETELLA PERTUSSIS

Answer 6

Small gram negative aerobic coccobacillus

• Spread by aerosolized droplets – highly infectious, may cause outbreaks
• Attaches to and grows on ciliated respiratory epithelium
• Virulence factors
  
  • Filamentous hemagglutinin –> attachment
  • Adenylate cyclase toxin –>ribosylates & inhibits Gi -> incr cAMP -> inhibits phagocyte function
  • Lipopolysaccharide
  • Pertussis toxin
  • Tracheal cytotoxin –> interferes with ciliary function

Sx:

• Catarrhal phase: Rhinorrhea – 1-2 weeks
• Paroxysmal cough “whoop” – 2-3 months
• Convalescent – 1-2 weeks

Dx:

• ​Nasopharyngeal swab
  
  • Regan-Lowe or Bordet-Gengou medium
  • PCR
• Lymphocytosis in serum

Rx: Macroglide

Prevention: Acellular vaccine

Question 7

HAEMOPHILUS INFLUENZAE

Answer 7

• Small, encapsulated, gram negative coccobacilli
• Fastidious
• Chocolate agar with factors V (NAD+) and X (hematin)
• Transmission: aerosol
• Produces IgA protease

Sx: HaEMOPhilius Influenzae

• Epiglotitis
  
  • HiB
  • Tripod posture
  • Stridor
  • thumbprint sign: thickening of epiglottis on lateral Xray
• Meningitis: Type B capsule c
• Otitis media
• Pneumonia

Major risk factor:

• Smoking
• EtOH
• Splenectomy
• Sickle cell

Rx:

• Ceftrixone for meningitis or systemic disease
• Rifampin for close contacts

Prevention:

• vaccine for H. flu type B
• vaccine conjugated to Diphtheriae toxin
• given bw 2 to 18 mo