This document is a medical microbiology textbook chapter on lower respiratory tract infections, written for undergraduate students. It defines and classifies conditions such as tracheitis, bronchitis, bronchiolitis, pneumonitis, pneumonia and pleurisy. The chapter explains the difference between typical and atypical pneumonia, noting that classification by sputum type is not reliable for…
This document is a medical microbiology textbook chapter on lower respiratory tract infections, written for undergraduate students. It defines and classifies conditions such as tracheitis, bronchitis, bronchiolitis, pneumonitis, pneumonia and pleurisy.
The chapter explains the difference between typical and atypical pneumonia, noting that classification by sputum type is not reliable for diagnosis. It instead recommends classifying pneumonia as community-acquired or healthcare-associated for better patient management.
Community-acquired pneumonia causes are listed by organism type: bacterial (including Streptococcus pneumoniae, H. influenzae, Mycoplasma pneumoniae), viral (influenza A, respiratory syncytial virus) and fungal (Pneumocystis jeroveci, dimorphic fungi, moulds).
Healthcare-associated pneumonia is divided into early onset (first 4 days of hospitalization, caused by Moraxella catarrhalis, H. influenzae, S. pneumoniae, viruses) and late onset (caused by Enterobacteriaceae at 40%, S. aureus at 25%, P. aeruginosa at 15%, plus fungi).
The final section covers laboratory diagnosis: collecting sputum and blood specimens, Gram staining to verify true sputum, checking for purulence, and applying diagnostic methods to determine the aetiology. Blood cultures are helpful as 30% of bacterial pneumonia cases have bacteraemia.