This document discusses various infections of the respiratory system caused by bacteria and fungi. It begins by describing the normal microbiota of the upper respiratory tract and how the lower tract is typically sterile. It then covers specific respiratory infections like strep throat, diphtheria, bacterial pneumonia, tuberculosis, whooping cough, anthrax, and fungal diseases like coccidioidomycosis that can spread systemically from the lungs. For each disease, it provides details on the causative agent, symptoms, transmission, diagnosis, and available treatments.

1. Infections of the respiratory system
Overview

2. Haemophilus species
Staphylococcus species S. aureus
non-hemolytic streptococci
a-hemolytic streptococci S. pneumoniae
Diphtheroids
Gram positive bacteria
Microbiota of the upper respiratory system
The upper respiratory system is colonized by many
different microorganisms including

3. Lower respiratory tract
 Typically microorganisms are not present in the lower
respiratory system (axenic environment)
 Ciliary escalator
 Alveolar macrophages
 IgA

4.  Inflammation of the pharynx
 Caused by group A
streptococci (Streptococcus
pyogenes)
 Seasonal incidence (winter
and spring), spreads via
respiratory droplets, treatable
with antibacterial drugs
Streptococcal pharyngitis – strep throat
 Can be associated with scarlet fever (scarlatina), rash that spreads across
the body, the tongue becomes strawberry red
 Untreated streptococcal pharyngitis can involve rheumatic fever
(inflammation of heart valves and muscle) and acute glomerulonephritis

5.  Corynebacterium diphtheriae
 Diphteria toxin is an inhibitor
of protein synthesis
 Vaccination against diphtheria is
part of the DTaP protocol
 Localized infection presents as
severe pharyngitis with plaque-like
pseudomembrane in the throat
 C. diphtheriae can also cause
systemic infection due to toxemia,
affecting nerves, kidney, or heart
Diphtheria

6. Bacterial pneumonia
 One of the most serious lower respiratory tract infections
 Inflammation of the lungs in which bronchioles/alveoli become
filled with fluid. The lung’s gas exchange is impaired
 Signs/symptoms include fever, chest pain, cough with or
without production of sputum
 Nosocomial pneumonia acquired in a health care setting
 Staphylococcus aureus
 Gram negative pneumonia
Klebsiella pneumoniae
 Can cause tissue damage with
production of thick, bloody
sputum

7. Bacterial pneumonia
 Community-acquired pneumonia
Streptococcus pneumoniae
Staphylococcus aureus
Haemophilus influenzae
Mycoplasma pneumoniae
Legionella pneumophila
Chlamydia psittaci-ornithosis
Chlamydia pneumoniae
Mycoplasma pneumoniae
 Walking pneumonia (not severe enough to cause
hospitalization) – nonproductive cough

8. Bacterial pneumonia
Pneumococcal pneumonia
 Rusty colored sputum is
coughed-up, containing
neutrophils
 Fall/winter
 Children, elderly,
immunocompromised patients
 Treatment with antibiotics
 Vaccine that target several
strains of S. pneumoniae for
children and elderly

9. Bacterial pneumonia
Legionella pneumophila causes
legionellosis
 Dry nonproductive cough
 Decreases pulmonary
function - potentially fatal
pneumonia
 Transmitted through air
conditioning systems, water
pipes, …..
 Resistant to heat and
chlorination
 Person-to-person spread is
not known
Pleomorphic, Gram negative

10. Tuberculosis (TB)
 Caused by Mycobacterium tuberculosis, a problem for the immune
system because it resists phagocytosis
 Primary tuberculosis involves
the formation of nodules in the
lungs called tubercles
 Secondary or reactivated TB,
Mycobacterium spreads through
the lungs from tubercles (after
decades from primary TB)
 In disseminated TB, the pathogen spreads throughout the body,
affecting different organs

11. Tuberculosis (TB)
 Chest X rays can reveal the presence of tubercles in the lungs

12. Tuberculosis (TB)
 Acid-fast cells/cords in sputum
indicate active case of
tuberculosis
 Patient must be monitored to assure compliance with drug therapy
 Directly Observed Treatment Shortcourse (DOTS) used to
prevent spread of tuberculosis and MDR/XDR strains
 Immunization with M. bovis vaccine can induce immunity in
patients

13. Tuberculosis (TB)
 Tuberculin skin test
 Positive test
 Appearance of red
swelling at the test
site (24-72h)
 A positive test cannot distinguish between
 chronic carriers and patients with active disease, or
 people that have been exposed to Mycobacterium or
immunized but currently uninfected

14. Tuberculosis (TB)
About one-third of the world’s population is infected, deaths of 1-3
million people per year

15. Pertussis – whooping cough (DTaP)
 Bordetella pertussis (Gram
negative)
 Pertussis is highly contagious,
spread through respiratory
droplets
 Severe form in children
younger than five years old
Bordetella stops the ciliary escalator
 Characteristic signs of whooping cough occur during the paroxysmal
phase: persistent, severe coughing spells, leading to vomiting,
cyanosis, exhaustion
 DTaP vaccine (aP, acellular component) - immunity is not lifelong

16. Inhalation anthrax (zoonosis)
 Inhalation anthrax is a respiratory disease caused by inhalation
of spores of Bacillus anthracis
 B. anthracis resists phagocytosis
by alveolar macrophages
 Vegetative cells produce the
anthrax toxin, causing rapid
 Damage to the lungs
 Toxemia
 Bacillus can be seen in the sputum of patients
 Serological, DNA, biochemical tests confirm
the presence of B. anthracis

17.  Early treatment increases the survival rate of patients
 Antimicrobial drugs
 Drainage of fluid from around the lungs
 Anthrax vaccine available to
 Military personnel
 people who work with animals
 researchers
 health care professionals with anthrax patients
Inhalation anthrax (zoonosis)
 Potential weapon of bioterrorism

18. Systemic mycoses: diseases caused by fungi that spread
throughout the body
 Inhalation of
arthroconidia from soil
germinate in the alveoli
 Coccidioidomycosis is caused by Coccidioides immitis
 C. immitis is a dimorphic fungus

19.  Patients can experience mild
respiratory symptoms or
 More severe infections
involving coughing up blood
and pneumonia
 When it spreads from the lungs to the CNS can lead to meningitis
but it is fatal if untreated
Systemic mycoses: diseases caused by fungi that spread
throughout the body
Arthroconidia germinate in
the alveoli

20.  Diagnosis
 Identification of
spherules in clinical
specimens
 C. immitis spreads to
subcutaneous tissues
causing lesions
Painless lesions
 Treatment requires antifungal drugs which
may cause toxicity problems
Systemic mycoses: diseases caused by fungi that spread
throughout the body

21. The geographic distributions of three systemic fungal diseases
endemic to North America
 Dimorphic fungi
 Blastomycosis associated with Blastomyces dermatitidis
 Histoplasmosis caused by Histoplasma capsulatum