Chapter 22 Diseases of the Respiratory System



Chapter 22  Diseases of the Respiratory System

 

Structure of the Respiratory System

•         Function of the respiratory system

•         Exchange of gases between the atmosphere and the blood

•         Respiratory system divided into two main parts

•         Upper respiratory system

•         Lower respiratory system

 

Upper Respiratory System

•         Function of the upper respiratory system

•         Collects air, filters contaminants from the air, and delivers it to the lower respiratory organs

•         Components of the upper respiratory system

•         Nose-external portion of the respiratory system

•         Nasal cavity-lined with hairs and a ciliated mucous membrane that help filter and trap particles and microbes

•         Pharynx-lined with a ciliated mucous membrane that pushes contaminants into the digestive system

•         Tonsils-aggregations of lymphoid tissue

 

Lower Respiratory System

•         Components of the lower respiratory system

•         Larynx-contains the vocal cords

•         Trachea, bronchi, bronchioles-series of tubes that allow movement of air through to the lungs

•         Alveoli-small air sacs of the lungs where oxygen from air enters the blood while carbon dioxide diffuses from the blood into the alveoli to be exhaled

•         Diaphragm-muscle involved in breathing

•         Protective components of the lower respiratory system include a ciliated mucous membrane, alveolar macrophages, and secretory antibodies

 

Normal Microbiota of the Respiratory System

•         Lower Respiratory System

•         Typically microorganisms are not present

•         Upper Respiratory System

•         The normal microbiota remove nutrients and produce substances that limit growth of pathogenic organisms

•         Some normal microbiota are opportunistic pathogens

•         Examples of normal microbiota

•         Hemophilus influenzae can colonize the nose

•         Staphylococcus aureus is present as normal microbiota in some individuals without causing disease

•         Diphtheroids can colonize the nose and nasal cavity

 

Bacterial Diseases of the Upper Respiratory System

•         Bacteria can infect the upper respiratory system and cause such conditions as sore throat

•         Examples of bacterial upper respiratory infections

•         Streptococcal respiratory diseases

•         Diphtheria

 

Streptococcal Respiratory Diseases

•         Cause: Group A streptococci (S. pyogenes)

•         Virulence factors: M proteins, hyaluronic acid capsule, streptokinases, C5a peptidase, pyrogenic toxins, streptlysins

•         Portal of entry: Upper respiratory tract via respiratory droplets

•         Signs/Symptoms: Sore throat, difficulty swallowing; may progress to scarlet or rheumatic fever

•         Susceptibility: Children typically most susceptible

•         Treatment: Penicillin is the standard treatment

•         Prevention: Infectious individuals are infectious for two days after treatment and should stay at home

 

Diphtheria

•         Cause: Cornybacterium diphtheriae

•         Virulence factor: Diphtheria toxin prevents polypeptide synthesis and causes cell death

•         Portal of entry: Spread person to person via respiratory droplets or skin contact

•         Signs/Symptoms: Sore throat, oozing fluid that hardens into a pseudomembrane that can obstruct airways

•         Susceptibility: Immunocompromised or nonimmune individuals develop symptomatic infections

•         Treatment: Administration of antitoxin and antibiotics

•         Prevention: Immunization

 

Bacterial Diseases of the Sinuses and Ears

•         Bacteria present in the pharynx can infect the sinuses or middle ear and cause disease

•         Examples of infections of the sinuses and ears

•         Sinusitis

•         Otitis media

 

Sinusitis

•         Cause: Various bacteria such as Streptococcus pneuomoniae, Staphylococcus aureus, Haemophilus influenzae, and Moraxella catarrhalis

•         Portal of entry: Bacteria in the pharynx spread to the sinuses via their connection with the throat

•         Signs/Symptoms: Pain and pressure of the affected sinus accompanied by malaise

•         Susceptibility: Adults are most often affected

•         Diagnosis: Symptoms are often diagnostic

•         Prevention: No known ways to prevent sinusitis

 

Otitis Media

•         Cause: Various bacteria such as Streptococcus pneuomoniae, Staphylococcus aureus, Haemophilus influenzae, and Moraxella catarrhalis

•         Portal of entry: Bacteria in the pharynx spread to the middle ear via the auditory tubes

•         Signs/Symptoms: Severe pain in the ears

•         Susceptibility: Children are most often affected

•         Diagnosis: Symptoms are often diagnostic

•         Treatment: Antimicrobial drugs

•         Prevention: Various measures may be taken to prevent otitis media such as tonsil removal and placement of plastic tubes in the ear to allow drainage

 

Viral Diseases of the Upper Respiratory System

•         Viral respiratory diseases are some of the most common human diseases

•         The common cold is the primary viral disease of the upper respiratory system

 

Common Cold

•         Cause: Rhinoviruses are the most common although numerous viruses cause colds

•         Portal of entry: Transmitted via coughing/sneezing, fomites, or person-to-person contact

•         Signs/Symptoms: Sneezing, runny nose, congestion, sore throat, malaise, and cough

•         Susceptibility: Children acquire colds most often

•         Diagnosis: Symptoms are usually diagnostic

•         Treatment: Supportive care for symptoms

•         Prevention: Antisepsis and disinfection of fomites

 

Bacterial Diseases of the Lower Respiratory System

•         Lower respiratory organs are usually axenic

•         When bacterial infection of the lower respiratory system occurs life-threatening illness can result

•         Examples of bacterial infections of the lower respiratory system

•         Bacterial pneumonia

•         Legionnaire’s disease

•         Pertussis (whooping cough)

•         Tuberculosis

 

Bacterial Pneumonias

•         Pneumonia is inflammation of the lungs accompanied by fluid filled alveoli and bronchioles

•         Pneumonia can be categorized by the affected region or the organism causing the disease

•         Lobar pneumonia-involves entire lobes of the lungs

•         Mycoplasmal pneumonia-caused by the bacterium Mycobacterium

•         Nosocomial pneumonia-pneumonia acquired in a health care setting

•         Bacterial pneumonias are the most serious of the pneumonias and the most frequent in adults

 

Pneumococcal Pneumonia

•         Cause: Streptococcus pneumoniae

•         Virulence factors: Adhesins, capsule, pneumolysin

•         Portal of entry: Inhalation

•         Signs/Symptoms: Fever, chills, congestion, cough, chest pain, and short, rapid breathing

•         Incubation period: One to three days

•         Susceptibility: Immunocompromised individuals

•         Treatment: Penicillin is the drug of choice

•         Prevention: Vaccination

 

Primary Atypical (Mycoplasmal) Pneumonia

•         Cause: Mycoplasma pneumoniae

•         Virulence factors: Adhesion protein

•         Portal of entry: Nasal secretions among individuals in close contact

•         Signs/Symptoms: Atypical symptoms including fever, malaise, sore throat, excessive sweating

•         Incubation period: One to four weeks

•         Susceptibility: High school and college students

•         Treatment: Tetracycline and erythromycin

•         Prevention: Difficult to prevent because individuals can be infective despite lack of symptoms

 

Klebsiella pneumonia

•         Cause: Klebsiella pneumoniae

•         Virulence factors: Capsule

•         Portal of entry: Inhalation

•         Signs/Symptoms: Typical pneumonia symptoms combined with a thick, bloody sputum and recurrent chills

•         Incubation period: One to three days

•         Susceptibility: Hospitalized individuals

•         Treatment: Cephalosporins and supportive care

•         Prevention: Aseptic technique by health care workers

 

Other Bacterial Pneumonia

•         Cause: Hemophilus influenzae, Staphylococcus aureus, Yersinia pestis, and Chlamydia species

•         Portal of entry: Inhalation, also via blood with Y. pestis

•         Signs/Symptoms: Typical pneumonia symptoms along with frothy, bloody sputum in the case of Y. pestis

•         Incubation period: Variable depending on cause although Y. pestis can produce symptoms in hours

•         Susceptibility: Typically young children

•         Treatment: Antibiotic treatment

•         Prevention: Good hygiene; vaccine available for H. influenzae

 

Legionellosis (Legionnaire’s Disease)

•         Cause: Legionella pneumophila

•         Portal of entry: Inhalation of Legionella-filled vesicles

•         Signs/Symptoms: Typical pneumonia symptoms and possible complications of the gastrointestinal tract, CNS, liver, and kidneys

•         Susceptibility: Includes the elderly, smokers, immunocompromised individuals

•         Diagnosis: Presence of Legionella or antibodies against the bacterium

•         Treatment: Erythromycin is the drug of choice

•         Prevention: Reduce bacterial presence in water

 

Tuberculosis

•         Signs and Symptoms

•         Initial symptoms include minor cough and mild fever

•         Later symptoms include difficulty breathing, chest pain, wheezing, and coughing up blood

•         Pathogen and Virulence Factors

•         Mycobacterium tuberculosis is the causative agent

•         Presence of virulence factors aid in pathogenesis

•         Mycolic acid present in the cell wall has various effects

•         Cord factor is required for mycobacteria to cause disease

•         Pathogenesis

•         M. tuberculosis can remain viable for long periods in aerosol drops due to protection of the mycolic acid in the cell wall

•         Three types of tuberculosis

•         Primary tuberculosis-initial case of tuberculosis disease

•         Secondary tuberculosis-reestablished tuberculosis

•         Disseminated tuberculosis-tuberculosis involving multiple systems

•         Epidemiology

•         Immunocompromised individuals are most at risk

•         Tuberculosis is the leading killer of HIV+ individuals

•         Diagnosis, Treatment, and Prevention

•         Tuberculin skin test identifies previous exposure to M. tuberculosis

•         Doesn’t distinguish between active disease, chronic carriers, or those who have been vaccinated

•         Treatment requires multi-drug regimen

•         Prevention includes vaccination in some countries and surveillance of patients to limit spread of disease

 

Pertussis (Whooping Cough)

•         Cause: Bordetella pertussis

•         Virulence factors: Pertussis toxin, adenylate cyclase toxin, dermonecrotic toxin, and tracheal cytotoxin

•         Portal of entry: Inhalation of bacteria in airborne droplets

•         Signs/Symptoms: Catarrhal stage: symptoms resemble a cold; Paroxysmal stage: characteristic severe cough; Convalescent stage: cough slowly subsides

•         Susceptibility: Unimmunized children

•         Treatment: Combination antibiotic therapy

•         Prevention: DTaP vaccine

 

Inhalation Anthrax

•         Cause: Bacillus anthracis

•         Virulence factors: Capsule, anthrax toxin

•         Portal of entry: Inhalation of endospores

•         Signs/Symptoms: Initial symptoms resemble a cold or flu but progress to severe coughing, shortness of breath, shock, and death

•         Diagnosis: Identification of bacteria in sputum

•         Treatment: Various antimicrobials

•         Prevention: Anthrax vaccine available to military personnel, researchers, health care workers dealing with anthrax patients

 

Influenza

•         Signs and Symptoms

•         Sudden fever, pharyngitis, congestion, cough, myalgia

•         Pathogens and Virulence Factors

•         Influenza virus types A and B are the causative agents

•         Strains named as follows: Type/Location /Month (as number)/Year (HA and NA antigen types)

•         Hemagglutinin and neuraminidase mutations produce the ever changing array of strains

•         Mutations occur via two main processes

•         Antigenic drift

•         Antigenic shift

•         Signs and Symptoms

•         Sudden fever, pharyngitis, congestion, cough, myalgia

•         Pathogens and Virulence Factors

•         Influenza virus types A and B are the causative agents

•         Strains named as follows: Type/Location /Month (as number)/Year (HA and NA antigen types)

•         Hemagglutinin and neuraminidase mutations produce the ever changing array of strains

•         Mutations occur via two main processes

•         Antigenic drift

•         Antigenic shift

•         Pathogenesis

•         Symptoms of influenza are produced by the immune response to the virus

•         Flu patients are susceptible to secondary bacterial infections due to virally produced damage to the lung epithelium

•         Epidemiology

•         Influenza is transmitted via inhalation of airborne viruses or by self-inoculation

•         Complications occur most often in the elderly, children, and those with chronic diseases

•         Diagnosis

•         Signs and symptoms during a community-wide outbreak are often diagnostic

•         Treatment

•         Four drugs are approved to treat influenza

•         Amantadine, rimantadine, oseltamivir, zanamivir

•         Treatment also involves supportive care to relieve symptoms

•         Prevention

•         Immunization with a multivalent vaccine

 

Severe Acute Respiratory Syndrome (SARS)

•         Cause: SARS-associated coronovirus

•         Portal of entry: Respiratory droplets enter through mucous membranes via close person-to-person contact

•         Signs/Symptoms: High fever, head and body aches, malaise, dry cough, pneumonia develops

•         Incubation period: Typically two to seven days

•         Susceptibility: Some individuals may be genetically susceptible

•         Treatment: Primarily supportive care

•         Prevention: Quarantine infected persons, good hygiene

 

Respiratory Syncytial Virus Infection

•         Most common childhood respiratory disease

•         Signs and Symptoms

•         Fever, runny nose, coughing, in babies or immunocompromised individuals

•         Mild coldlike symptoms occur in older children and adults

•         Pathogen

•         Respiratory syncytial virus (RSV)

•         Pathogenesis

•         Formation of syncytia can help viruses evade the immune system and also infect new cells

•         Epidemiology

•         Transmission occurs via close contact with infected persons

•         Diagnosis, Treatment, and Prevention

•         Diagnosis of RSV infection made by immunoassay combined with signs of respiratory distress

•         Supportive treatment for young children

•         Prevention includes aseptic technique of health care workers and day care employees

 

Hantavirus Pulmonary Syndrome (HPS)

•         Cause: Hantavirus strains

•         Portal of entry: Inhalation of infected rodent excrement or saliva

•         Signs/Symptoms: High fever, head and body aches, malaise, dry cough, pneumonia develops

•         Incubation period: Fourteen to thirty days

•         Susceptibility: Individuals exposed to rodents in endemic areas

•         Treatment: Supportive care

•         Prevention: Avoidance of rodent droppings

 

Other Viral Respiratory Diseases

•         Other viruses cause respiratory disease in children, the elderly, or immunocompromised individuals

•         Cytomegalovirus

•         Metapneumovirus

•         Estimated to be the second most common cause of viral respiratory disease behind rhinoviruses

•         Parainfluenzaviruses

•         Three strains cause croup and viral pneumonia

•         Occurs primarily in young children

 

Fungal Infections of the Lower Respiratory System

•         Certain systemic mycoses can involve the respiratory system

•         Coccidioidomycosis

•         Blastomycosis

•         Histoplasmosis

•         Pneumocystis pneumonia is a common fungal pneumonia of AIDS patients

 

Coccidioidomycosis

•         Commonly called valley fever

•         Cause: Coccidioides immitis

•         Portal of entry: Inhalation of arthroconidia in the soil

•         Signs/Symptoms: Symptoms can resemble pneumonia or tuberculosis; infection can become systemic in immunocompromised persons with various symptoms

•         Epidemiology: Endemic to southwestern U.S. and Mexico

•         Diagnosis: Presence of spherules in clinical specimens

•         Treatment: Amphotericin B

•         Prevention: Protective masks can prevent exposure to arthroconidia for those in occupations with high risk

 

Blastomycosis

•         Cause: Coccidioides immitis

•         Portal of entry: Inhalation of fungal spores in dust

•         Signs/Symptoms: Flulike symptoms: systemic infections can produce painless lesions on the face and upper body or purulent lesions on various organs

•         Epidemiology: Endemic to southeastern U.S. and Canada

•         Diagnosis: B. dermatitidis in clinical samples

•         Treatment: Amphotericin B

 

Histoplasmosis

•         Most common fungal systemic disease of humans

•         Cause: Histoplasmosis capsulatum

•         Portal of entry: Inhalation

•         Signs/Symptoms: Dry cough with blood tinged sputum and skin lesions

•         Epidemiology: Endemic to eastern U.S. but also found in parts of Africa and Central and South America

•         Susceptibility: Children and those exposed to soil

•         Diagnosis: Presence of budding yeast in macrophages

•         Treatment: Amphotericin B

•         Prevention: Minimize exposure to soil

 

Pneumocystis Pneumonia (PCP)

•         Cause: Pneuocystis jiroveci (Previously P. carinii)

•         Portal of entry: Inhalation of droplets containing the fungus

•         Signs/Symptoms: Difficulty breathing, mild anemia, hypoxia, and fever

•         Susceptibility: Immunocompromised patients particularly those with AIDS

•         Treatment: Trimethoprim and sulfamethoxazole (TMP-SMX)

•         Prevention: Cannot avoid the fungus but maintenance of a healthy immune system limits disease

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