Download Infections of the Respiratory System

Microbiology: A Systems
Approach, 2nd ed.
Chapter 21: Infectious Diseases
Affecting the Respiratory System
21.1 The Respiratory Tract and Its
Defenses
• Most common place for infectious agents to gain
access to the body
• Upper respiratory tract: mouth, nose, nasal cavity,
sinuses, pharynx, epiglottis, larynx
• Lower respiratory tract: trachea, bronchi, bronchioles,
lungs, alveoli
• Defneses
–
–
–
–
Nasal hair
Cilia
Mucus
Involuntary responses such as coughing, sneezing, and
swallowing
– Macrophages
– Secretory IgA against specific pathogens
Figure 21.1
21.2 Normal Biota of the Respiratory
Tract
• Generally limited to the upper respiratory tract
• Gram-positive bacteria (streptococci and
staphylococci) very common
• Disease-causing bact4eria are present as normal
biota; can cause disease if their host becomes
immunocompromised or if they are transferred
to other hosts (Streptococcus pyogenes,
Haemophilus influenza, Streptococcus
pneumonia, Neisseria meningitides,
Staphylococcus aureus)
• Normal biota perform microbial antagonism
21.3 Upper Respiratory Tract Diseases
Caused by Microorganisms
• Rhinitis, or the Common Cold
– Symptoms: sneezing, scratchy throat, runny nose
(rhinorrhea)
– Symptoms begin 2-3 days after infection
– Generally not accompanied by fever
Sinusitis
– Commonly called a sinus infection
– Most commonly caused by allergy
– Can also be caused by infections or structural
problems
– Generally follows a bout with the common cold
– Symptoms: nasal congestion, pressure above the
nose or in the forehead, feeling of headache or
toothache
– Facial swelling and tenderness common
– Discharge appears opaque with a green or yellow
color in case of bacterial infection
– Discharge caused by allergy is clear and may be
accompanied by itchy, watery eyes
Acute Otitis Media (Ear Infection)
• Also a common sequel of rhinitis
• Viral infections of the upper respiratory tract lead to
inflammation of the Eustachian tubes and buildup of fluid
in the middle ear- can lead to bacterial multiplication in the
fluids
• Bacteria can migrate along the eustachian tube from the
upper respiratory tract, multiply rapidly, leads to pu
production and continued fluid secretion (effusion)
• Chronic otitis media: when fluid remains in the middle ear
for indefinite periods of time (may be caused by biofilm
bacteria)
• Symptoms: sensation of fullness or pain in the ear, loss of
hearing
• Untreated or severe infections can lead to eardrum rupture
Figure 21.2
Pharyngitis
• Inflammation of the throat
• Pain and swelling, reddened mucosa, swollen
tonsils, sometime white packets of
inflammatory products
• Mucous membranes may swell, affecting
speech and swallowing
• Often results in foul-smelling breath
• Incubation period: 2-5 days
Figure 21.3
Figure 21.4
Figure 21.5
Figure 21.7
Diphtheria
• Symptoms initially experienced in the upper
respiratory tract
• Sore throat, lack of appetite, low-grade fever
• Pseudomembrane forms on the tonsils or
pharynx
Figure 21.8
Figure 21.9
Figure 21.10
21.4 Diseases Caused by
Microorganisms Affecting the Upper
and Lower Respiratory Tract
• A number of infectious agents affect both the
upper and lower respiratory tract regions
• Most well-known: whopping cough,
respiratory syncytial virus (RSV), and influenza
Whooping Cough
• Also known as pertussis
• Two distinct symptom phases
– Catarrhal stage
• After incubation from 3 to 21 days
• Bacteria in the respiratory tract cause what appear to be
cold symptoms (runny nose)
• Lasts 1 to 2 weeks
– Paroxysmal stage
• Severe and uncontrollable coughing
• Violent coughing spasms can result in burst blood vessels in
the eyes or even vomiting
• Followed by a long recovery (convalescent) phase
– Complete recovery requires weeks or even months
– Other microorganisms can more easily cause
secondary infection
Respiratory Syncytial Virus Infection
• Produces giant multinucleated cells (synctia)
in the respiratory tract
• Most prevalent cause of respiratory infection
in the newborn age group
• First symptoms: fever that lasts approximately
3 days, rhinitis, pharyngitis, and otitis
• More serious infections give rise to symptoms
of croup: coughing, wheezing, dyspnea, rales
Influenza
• Begins in the upper respiratory tract; serious
cases may also affect the lower respiratory
tract
• 1- to 4-day incubation period
• Symptoms begin very quickly: headache,
chills, dry cough, body aches, fever, stuffy
nose, and sore throat
• Extreme fatigue can last a few days or a few
weeks
Figure 21.12
Figure 21.13
21.5 Lower Respiratory Tract Diseases
Caused by Microorganisms
• Diseases that affect the bronchi, bronchioles,
and lungs
• Tuberculosis and pneumonia
Tuberculosis
• Humans are easily infected with
Mycobacterium tuberculosis but are resistant
to the disease
• Only about 5% of infected people actually
develop a clinical case of TB
• Untreated TB progresses slowly
• Clinical TB is divided into primary tuberculosis,
secondary tuberculosis, and disseminated
tuberculosis
Primary Tuberculosis
• Period of hidden infection- asymptomatic or
accompanied by mild fever
• After 3 to 4 weeks, immune system mounts a
cell-mediated assault- large influx of
mononuclear cells into lungs
• Tubercles form
• Frequently the centers of tubercles break down
into necrotic caseous lesions that gradually heal
by calcification
• Tuberculin reaction
Figure 21.14
Figure 21.15
Secondary (Reactivation) Tuberculosis
• Live bacteria can remain dormant and become
reactivated weeks, months, or years later
• Chronic tuberculosis: tubercles filled with
bacteria expand and drain into bronchial
tubes and upper respiratory tract; severe
symptoms such as violent coughing, greenish
or bloody sputum, low-grade fever, anorexia,
weight loss, extreme fatigue, night sweats,
chest pain
Extrapulmonary Tuberculosis
• Outside of the lungs
• More common in immunosuppressed patients
and young children
• Regional lymph nodes, kidneys, long bones,
genital tract, brain, and meninges
• Complications are usually grave
Figure 21.17
Figure 21.18
Figure 21.19
Pneumonia
• Anatomical diagnosis
• Inflammatory condition of the lung in which fluid fills the
alveoli
• Can be caused by a wide variety of different
microorganisms
• Viral pneumonias are usually milder than bacterial
• Community-acquired vs. nosocomial pneumonias
• Begin with upper respiratory tract symptoms, including
runny nose and congestion
• Headache common
• Fever is often present
• Onset of lung symptoms follows: chest pain, fever, cough,
discolored sputum
Figure 21.20
Figure 21.21
Figure 21.22
Figure 21.23
Figure 21.24
Figure 21.26