PneumoniaDefinition → Inflammation of the alveoliand terminal airspaces in response toinvasion by an infectious agent
Pathogenesis• Factor responsible for development ofpneumonia– Defect in host defense– Overwhelming inoculum
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
Mode of transmission• Air born• Aspiration of upper respiratory flora• Metastatic seeding through blood
Community AcquiredPneumoniaetiology S.pneumoniaeH.influenzaeM.pneumoniae C.pneumoniaeL.pneumophiliaAnaerobesOther
Pneumonia History →• Fever/Chills, cough, sob, chest pain• Physical Exam → Varies based on age of childNewbornsPatients do not cough → more commonly presentwith tachypnea, retractions, gruntingAdults• Auscultation of the lung fields may yield thefollowing:– Crackles, wheezing, diminished breath sounds,tubular breath sounds, or pleural friction rub
Ventilator associated pneumonia(VAP)• VAP refers to pneumonia that arises more than48–72 hours after endotracheal intubation.• Most concerning aspect of VAP is the high rateof associated mortality.• Risk factors :– patient related (male sex, preexisting pulmonarydisease, or multiple organ system failure)– treatment related (intubation or enteral feeding)Modifiable risk factors for HAP are obvioustargets for improved management andprophylaxis in several studies.
PneumoniaDiagnosis →Sputum Culture → usually not helpful → poorcorrelation with lower respiratory pathogensTracheal aspirate: Quantitative cultureBroncho-alveolar levage→ most useful inimmunocompromised patients believed to haveunusual organisms or patients who are severely illLung Aspirate → underused but can be very helpfulone series reports 52% positive cultures using thisapproachBlood & pleural fluid cultures positive in <20% cases
Sputum:• One of the most common types of specimensubmitted to the laboratory for bacterialexamination.• Difficult to obtain because of contamination withsaliva.• Many of the bacteria which are known to causelower respiratory tract infections may be presentin the oropharynx as part of the normal flora• The examination of a direct smear from thespecimen can be very helpful in diagnosingrespiratory infections and in determining theusefulness of the information provided by theculture.
Reporting• The average number of each type of cellper low power field in a representativearea of the smear is recorded.• Less than 1 and up to 9 cells per field arereported as “Few”• 10 to 25 cells are reported as “Moderate”• Any number in excess of 25 is reported as“Numerous”
Culture media• Chocolate agar• CN agar• MacConkey’s agar
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
Tuberculosis• Aetiology: Mycobacterium tuberculosis• Subacute infection– Chronic cough +/- haemoptysis– Fever– Weight loss– Night sweats• Extrapulmonary and atypical pulmonarypresentations more common in immuno-compromised host• Risk 100-fold higher in HIV/AIDS