Infections of the respiratory system Overview

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

Lower respiratory tract

Typically microorganisms are not present in the lower respiratory system (axenic environment) Ciliary escalator Alveolar macrophages IgA

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

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

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

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

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

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

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

Tuberculosis (TB)

Chest X rays can reveal the presence of tubercles in the lungs

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

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

Tuberculosis (TB)

About one-third of the world’s population is infected, deaths of 1-3 million people per year

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

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

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

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

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

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

The geographic distributions of three systemic fungal diseases endemic to North America

Dimorphic fungi Blastomycosis associated with Blastomyces dermatitidis Histoplasmosis caused by Histoplasma capsulatum