Respiratory Infections

what is the most common site for infections?

Respiratory tract

respiratory infections are caused by…?

– Direct contact with the environment
– Constant exposure to infectious agents in the air

Respiratory infections are more common what time of year? why?

winter

1. Proximity to others while confined indoors & poor ventilation
2. Breathing cold air → cough, sneeze, runny nose
3. Cold and dry air → smaller respiratory droplets → stay longer in the air → Increased transmission of pathogens

the upper respiratory system consists of?

the lower respiratory system consists of?

what defense mechanisms does the nose have (respiratory tract)?

• Nose hairs (filters)
• Nasal turbinates (filters)
• Nasal mucus (sticky, enzymes)

what defense mechanisms does the throat/bronchi have (respiratory tract)?

• Mucociliary escalator
• Coughing reflex

what defense mechanisms does the alveoli have (respiratory tract)?

Alveolar macrophages

Risk factors for respiratory diseases

Anything that impairs the defenses of the respiratory tract:
• Smoking
• Weak immunity
• Serious diseases (lungs, heart, kidney)
• Asthma
• Dry air
• Pollutants

what is the mucociliary escalator (ME)? what are the 2 parts?

major barrier against infection

• made of:

  • goblet cells → produce mucus

  • ciliated epithelial cells (create upward flow)

how does the mucociliary escalator work to as a barrier against infection?

• The cilia are continually beating, pushing mucus up and out into the throat

• Microorganisms are caught in the sticky mucus and moved up

how does smoking affect the micociliary escalator?

Smoking paralyzes the cilia

TRUE or FALSE?
A. Alveolar macrophages are a defense mechanism of the nasopharynx.
B. Anything that impairs the function of the mucociliary escalator is a risk factor for respiratory disease.
C. Pathogenic organisms stick to mucus, which helps them penetrate deeper into the respiratory tract.
D. Smoking impairs the expulsion of the mucus from the airways.

F

T

F

T

what are the 2 types of respiratory infections?

1. upper respiratory infections (URIs)

2. lower respiratory infections (LRIs)

pertussis is also known as

whooping cough

what are the early symptoms of pertussis (1-2 weeks)?

Early, cold-like symptoms (1-2 weeks):
Runny nose
Low-grade fever
Mild, occasional cough

what are the late symptoms of pertussis?

Fits of many, rapid coughs followed by a high-pitched "whoop"
Vomiting during or after coughing fits
Exhaustion after coughing fits

cough caused by pertussis may last how long?

>10 weeks (chinese call is 100-day cough)

pertussis is most dangerous in what demographic? why?

infants

• can cause apnea (pause in breathing pattern) + cyanosis

__% of deaths due to B. pertussis infections are in infants under 1 year

~__% of infants under 1 year who get pertussis need hospital care

70%

50%

what type of bacteria is bordetella pertussis?

gram (-)

coccbacillus

bordetella pertussis: encounter

person-to-person (does not survive well in the environment), highly contagious

bordetella pertussis: entry

inhalation

bordetella pertussis: multiplication

obligate aerobe, extracellular, adheres to ciliated bronchial epithelial cells

bordetella pertussis: spread

local infection, no spread

how does bordetella pertussis cause damage?

1. Produces toxins that immobilize the mucociliary escalator

2. mucus builds-up

3. inefficient clearing of bronchial tubes

4. cough receptors become stimulated

5. the WHOOP is due to influx of air back into lungs after coughing episode

what is the pertussis vaccine called?

DTaP (for young children)

Tdap (for adults)

pneumonia is infection of the

lung parenchyma (a portion of the lung involved in gas transfer: the alveoli, alveolar ducts and bronchioles)

what is pneumonia caused by?

many different microbes (bacteria, viruses, fungi) which result in different diseases that share a common anatomical location

what characterizes acute penumonia?

sudden onset, symptoms progress over a few days

what are the community acquired vs nosocomial acute pneumonia syndromes?

• Community acquired

  • Streptococcus pneumoniae, person-to-person

  • Legionella pneumophila, environmental

• Nosocomial (hospital acquired)

  • Pseudomonas aeruginosa

what are the subacute or chronic pneumonia syndromes?

fungal pneumonia (Histoplasma capsulatum)

what type of bacteria is Streptococcus pneumoniae?

gram (+) diplococcus

Streptococcus pneumoniae: encounter

asymptomatically colonizes the nasopharynx
–40-70% of children
–5-10% of adults

what is the most common cause of community-acquired pneumonia?

Streptococcus pneumoniae

what patient demographics are most susceptible to community-acquire pneumonia caused by Streptococcus pneumoniae?

– Young children < 2 years old
– Elderly > 65 years old
– Smokers
– Adults with chronic illness, weak immune system

Streptococcus pneumoniae: spread

person-to-person

fomites

spread of Streptococcus pneumoniae out of the nasopharynx can lead to diseases like?

• spread to blood → bacteremia, sepsis

• spread to other organs

t/f: pneumonia is often fatal before antibiotics but disease responses quickly to antibiotics

true (recovery depends on antibody production)

Streptococcus pneumoniae: multiplication

• facultative anaerobe, grows extracellularly

• capsule allows it to resist phagocytosis by macrophages

Streptococcus pneumoniae: damage (direct)

pneumolysin (pore-forming toxin, virulence factor)

Streptococcus pneumoniae: damage (indirect)

influx of neutrophils (PMNs) -> acute inflammation, tissue damage, fluids in the lung

how does S. pneumoniae cause lung damage?

1. Bacteria get into alveoli -> immune system is activated
2. Neutrophils come in to battle bacteria
3. Cytokines are released (fever, chills, fatigue)
4. Neutrophils, bacteria, exudate, fluid fill the alveoli (poor gas exchange, hard to breathe)

what type of bacteria is Legionella pneumophila?

gram (-) bacillus

Legionella pneumophila: encounter

environment
• Lakes, streams, ponds
• Plumbing systems: air conditioning units, hot tubs, hot
water tanks and heaters, dental-unit water systems

Legionella pneumophila: entry

mist inhalation, water aspiration

Legionella replicates inside what?

amoebas (natural reservoir)

what disease does Legionella pneumophila cause?

pneumonia (Legionnaire’s disease, Pontiac fever)

Legionella pneumophila: spread

no human-human transmission (humans are dead-end hosts

Legionella pneumophila: multiplication

• aerobe, grows intracellularly

• No capsule to prevent phagocytosis, so:

  • The organism is taken up by macrophages but not killed

  • Legionella grows inside macrophages

Legionella pneumophila: damage is due to?

host inflammatory response

Legionella pneumophila can be found in all of the following EXCEPT one. Which is the EXCEPTION?
A. Air conditioning systems
B. Dental unit water lines
C. Hot tubs
D. Lakes and ponds
E. Healthy human microbiota

E. Healthy human microbiota

what type of bacteria is Pseudomonas aeruginosa?

gram (-) bacillus

Pseudomonas aeruginosa: encounter

• Environment: aquatic reservoirs, cockroaches
• Hospitals, homes
• Person-to-person

Pseudomonas aeruginosa: multiplication

• Facultative anaerobe
• Needs iron
• Biofilms

Pseudomonas aeruginosa: damage is caused by?

• Many extracellular toxins
• Cell lysis (to acquire iron)

Pseudomonas aeruginosa: outcome

• Antibiotic resistance is a problem
• Combination antibiotics are used in treatment

how does Pseudomonas aeruginosa affect healthy, immunocomptenet people?

no or mild disease

– Ears, eyes: contaminated water, contact lens solutions
– Skin: “hot tub rash

how does Pseudomonas aeruginosa affect immunocompromised people?

serious disease

– Cystic fibrosis patients (CF = poor lung function due to thick mucus)
– Patients on ventilators, with catheters, wounds from surgery or burns (nosocomial infections)

what is an opportunistic pathogen?

a microorganism that is normally harmless but can cause disease in people with weakened immune systems

eg. Pseudomonas aeruginosa

TRUE or FALSE?
A. Legionella pneumophila is a frequent cause of pneumonia acquired in nosocomial (hospital) settings.
B. Lung damage during pneumonia is caused both directly by the infectious organism and by the host response to infection.
C. Pseudomonas aeruginosa infections are acquired only from the environment and cannot be transmitted person-to-person.
D. Streptococcus pneumoniae can be transmitted on fomites

F

T

F

T

All of the following are risk factors that increase susceptibility to the disease pneumonia EXCEPT one. Which is the EXCEPTION?
A. Smoking
B. Undergoing chemotherapy
C. Having the disease cystic fibrosis
D. Working at a hospital

D. Working at a hospital

Streptococcus pneumoniae, Legionella pneumophila, Pseudomonas aeruginosa are all examples of…?

acute pneumonia

what type of bacteria is Pulmonary Actinomycosis?

gram (+) bacilli) of actinomyces species

Pulmonary Actinomycosis: enounter

• Oral and gut microbiota
• Associated with periodontitis and caries

Pulmonary Actinomycosis: entry

• Aspiration from oropharynx

Pulmonary Actinomycosis: disease

A rare infection of the lung

Pulmonary Actinomycosis: risk factors

• Poor dental hygiene

• dental abscess

• weak immune system

• alcohol abuse

• emphysema

All of the following are risk factors for the development of pulmonary actinomycosis EXCEPT one. Which is the EXCEPTION?
A. Alcohol abuse
B. Dental abscess
C. Use of broad-spectrum antibiotics
D. Poor dental hygiene

C. Use of broad-spectrum antibiotics

Airborne microorganisms can cause

respiratory diseases

t/f: Although topologically open, the respiratory system is well protected

true

Bacteria have mechanisms to counteract host defenses such as

– capsule, growth within macrophages, attachment factors
– toxins

what makes something a risk factor for respiratory diseae?

Anything that impairs the defenses of the respiratory tract