AGA KHAN UNIVERSITY HOSPITAL KARACHI PAKISTAN

1. Lower Respiratory tract
Infections
Dr Seema Irfan
Assistant Professor
Department of Pathology and Microbiology

2. Lower Respiratory tract Infections

3. Normal host defense
• Nasopharynx
• Conducting airways
• Lower respiratory tract
 Nasal hair
 Turbinates
 Mucocilliary apparatus
 IgA secretion
 Cough, epiglottis reflex, sharp
angle branching, mucocilliary
apparatus, Immunoglobulin
(IgA)
 Alveolar lining fluid
 Alveolar macrophages
 Polymorph
 Cell mediated immunity
 Cytokines

4. Pneumonia
Definition → Inflammation of the alveoli
and terminal airspaces in response to
invasion by an infectious agent

5. Pathogenesis
• Factor responsible for development of
pneumonia
– Defect in host defense
– Overwhelming inoculum

6. Breech of body barriers
• Cigarette smoking
• Viral infection
• Trauma to chest wall
• Pulmonary edema
• Alteration in the level of consciousness
– Stroke
– Seizures
– Sedation
– Alcohol abuse
– Even normal sleep

7. Mode of transmission
• Air born
• Aspiration of upper respiratory flora
• Metastatic seeding through blood

8. Aetiology
• Viral
• Bacterial
• Mycobacterial
• Fungal
• Protozoal
• Others

9. Community Acquired Pneumonia
Typical
S.pneumoniae
H.Influenzae
M.catarrhalis
K.Pneumoniae
S.aureus
Pseudomonas
aeruginosa
Anaerobes; Bacteroides
Atypical
Mycoplasma pneumoniae
Chlamydia pneumoniae
Coxiella burnettii,
Legionella pneumophila,
RSV, Influenza, VZ,
Adeno, Measles & Hanta
virus, Fungi, Worms,
Pneumocystis

10. Community Acquired
Pneumonia
etiology S.pneumoniae
H.influenzae
M.pneumoniae C.pneumoniae
L.pneumophilia
Anaerobes
Other

11. Pneumonia
 History →
• Fever/Chills, cough, sob, chest pain
• Physical Exam → Varies based on age of child
Newborns
Patients do not cough → more commonly present
with tachypnea, retractions, grunting
Adults
• Auscultation of the lung fields may yield the
following:
– Crackles, wheezing, diminished breath sounds,
tubular breath sounds, or pleural friction rub

12. Hospital Acquired Pneumonia
• Common organisms:
– Enteric gram negative rods
– P.aeruginosa
– Acinetobacter spp.
– Burkholderia cepacia
– Stenotrophomonas maltophila
• Ventilator associated pneumonia
• Aspiration pneumonia

13. Ventilator associated pneumonia
(VAP)
• VAP refers to pneumonia that arises more than
48–72 hours after endotracheal intubation.
• Most concerning aspect of VAP is the high rate
of associated mortality.
• Risk factors :
– patient related (male sex, preexisting pulmonary
disease, or multiple organ system failure)
– treatment related (intubation or enteral feeding)
Modifiable risk factors for HAP are obvious
targets for improved management and
prophylaxis in several studies.

14. Chest x-ray (Acute Lobar pneumonia)

15. Bacterial pneumonia
Acute Chronic
• Streptococus pneumoiae M.tuberculosis
• Haemophilus influenzae Nocardia species
• Moraxella catarrhalis
• Klebsella pneumoniae and
other enterobacteriaceae
• Staphylococcuc aureus
• Pseudomonas aeroginosa
• Legionella pneumophila
• Mycoplsma pneumoniae
• Chlamydia pneumoniae

16. Pneumonia
Diagnosis →
Sputum Culture → usually not helpful → poor
correlation with lower respiratory pathogens
Tracheal aspirate: Quantitative culture
Broncho-alveolar levage→ most useful in
immunocompromised patients believed to have
unusual organisms or patients who are severely ill
Lung Aspirate → underused but can be very helpful
one series reports 52% positive cultures using this
approach
Blood & pleural fluid cultures positive in <20% cases

17. Sputum:
• One of the most common types of specimen
submitted to the laboratory for bacterial
examination.
• Difficult to obtain because of contamination with
saliva.
• Many of the bacteria which are known to cause
lower respiratory tract infections may be present
in the oropharynx as part of the normal flora
• The examination of a direct smear from the
specimen can be very helpful in diagnosing
respiratory infections and in determining the
usefulness of the information provided by the
culture.

20. Unsatisfactory sputum samples

21. Satisfactory sputum samples

22. Reporting
• The average number of each type of cell
per low power field in a representative
area of the smear is recorded.
• Less than 1 and up to 9 cells per field are
reported as “Few”
• 10 to 25 cells are reported as “Moderate”
• Any number in excess of 25 is reported as
“Numerous”

23. Culture media
• Chocolate agar
• CN agar
• MacConkey’s agar

24. Streptococus pneumoiae

25. Cross section of Streptococcus
pneumoniae

26. ARRANGEMENTS OF COCCI

27. Identification of Streptococcus
pneumoniae

28. Sensitivity by disc diffusion method

29. Haemophilus influenzae Menengitis

30. Colony morphology Haemophilus
influenzae

31. Haemophilus influenzae

32. Haemophilus influenzae

33. Haemophilus influenzae

34. sattelitism

35. Moraxella catarrhalis

36. Colony morphology of Moraxella
catarrhalis

37. Moraxella catarrhalis

38. Klebsiella pneumoniae

39. Colony morphology of Klebsiella
pneumoniae

40. Chest X-ray(nosocomial
pneumonia)

41. Sputum gram stain

42. Pseudomonas aeroginosa

43. Atypical bacterial pneumonia
• Mycoplasma, Legionella, Chlamydia
• Unusual presentation
• Extrapulmonary features
• CXR often normal early in infection
• WBC normal
• Diagnosis-serology, urine
• Treatment-macrolides, newer quinolones

44. Tuberculosis
• Aetiology: Mycobacterium tuberculosis
• Subacute infection
– Chronic cough +/- haemoptysis
– Fever
– Weight loss
– Night sweats
• Extrapulmonary and atypical pulmonary
presentations more common in immuno-
compromised host
• Risk 100-fold higher in HIV/AIDS

45. Chest X-ray showing cavitation

46. Air born infection

47. TB diagnosis
• Sputum x 3 for AFB
Smear
• TB culture
– Sputum
– Bronchoscopy
– Other fluid if involved eg
pleural, CSF etc
• Mantoux test

48. Acid fast staining of Mycobacterium
tuberculosis

49. Colony morphology of Mycobacterium
tuberculosis

50. Fungal pneumonia
• Endemic fungi
– Histoplasmosis
– Blastomycosis
– Cryptococcosis
• Aspergillus
• Candida