Chapter24

Chapter 24: Diseases of the respiratory system

Diseases of the upper respiratory tract• Upper respiratory tract = nose, pharynx,

(throat) and associated structures (middle ear, auditory or eustachian tubes)

• Normal microbiota of the URT – streptococcus and staphylococcus are common– Some pathogens such as Streptococcus pyogenes

and Haemophilus influenza are also present as normal microbiota

3. The respiratory tract is a portal of entry to the blood which can spread disease to internal organs

Bacterial Infections of the URT

Streptococcal Pharyngitis (strep throat)• Caused by group A streptococci (GAS) –

Streptococcus pyogenes which also causes impetigo, erysipelas, and acute bacterial endocarditis

a. G+, encapsulated cocci that occurs in chains

• Sx = local inflammation, fever, sometimes tonsillitis, enlarged lymph nodes, otitis media, coughing, fiery red beefy appearance to pharyngeal tissue


Streptococcal Pharyngitis

3. Transmitted by respiratory secretions

4. Tx = penicillin, if untreated a complication is rheumatic fever

a. fever, inflammation of the small blood vessels, may have permanent scarring and distortion of the heart valves = rheumatic heart disease

5. Dx = rapid antigen detection test – no longer do a throat culture


Scarlet Fever = strep throat accompanied by a skin rash

• Rash is caused by a bacterial erythrogenic (reddening) toxin– Toxin causes a pinkish red rash, high fever– Tongue has a strawberry like appearance, loses its

upper membrane, becomes red and enlarged, skin peels off like a sunburn

– Similar to scalded skin syndrome caused by Staphylococcus aureus

2. Used to be leading cause of death in US children but today is mild and rare disease


Diphtheria – Greek for membrane• Pathogen = Corynebacterium diphtheriae– G +, nonendospore forming rod– Morphology – pleomorphic, can be club shaped,

stains unevenly

• Signs and sxs– Sore throat, fever, malaise, swelling of the neck– Tough grayish membrane in throat (biofilm) which

consists of fibrin, dead tissue, bacterial cells and can totally block air to lungs


Diphtheria3. Tx/Prevention = DTaP vaccine

a. D stands for diphtheria toxoid which is an inactivated toxin that causes the body to produce Abs against the diphtheria toxinb. if the toxin enters tissue cells it can effect the heart or kidneys and become fatal. It can also involve nerves and cause paralysisc. Antibiotics kill the bacterial cell but need to be given with an antitoxin


Diphtheria4. Cutaneous diphtheriaCutaneous diphtheria – infects the skin causing

slow growing ulcerations covered by a gray membranea. common in tropical countries and native Americansb. responsible for most cases of diphtheria in people over 30

5. Respiratory cases – spread by droplet infection or contact with cutaneous diphtheria

Viral Infections of the URT

Viral infections – common cold• Caused by several different viruses such

as rhinovirus, adenovirus, coronavirus• Sxs = coughing, sneezing, runny nose• Ear and sinus infections may be a

complication

Bacterial Diseases of the lower respiratory tract

• Lower respiratory tract = larynx, trachea, bronchial tubes, alveoli

• No microbiota – should be sterile

Pertussis = whooping cough1. Pathogen = Bordetella pertussis a small

aerobic G neg coccobacillusa. virulent stains have a capsule and produce several potent toxins

Bacterial Diseases of the LRT

Pertussis2. The Bacteria attach to the ciliated cells in the

trachea impeding their ciliary action and destroying cellsa. this prevents movement of mucus by the ciliary escalator

3. The disease progresses in stagesa. catarrhal stage – initial stage

1) sxs resemble a common cold

Pertussis = whooping cough

b. paroxysmal stage – 2nd stage

1) prolonged series of coughing

2) in an attempt to cough up mucus – get violent coughing spells which can actually break ribs in small children

3) in between coughing spells gasping for air produces whooping sound

4) this stage lasts for 1 – 6 weeks

Pertussis

3. c. convalescence stage – sporadic cough that slowly subsides

1) this stage lasts for months4. Vaccine DTaP – aP = acellular vaccine

that contains an assortment of bacterial virulence factors instead of the killed whole cell vaccine of the 1940sa. the vaccination diminishes after approximately 12 years

Tuberculosis - LRT

• Pathogen = Mycobacterium tuberculosis – Slender rod, obligate aerobe– Acid fast due to large amount of lipids in the

cell wall which makes it resistant to drying and disinfectants

– Tends to exhibit rope like growth due to a waxy component of the cell wall called cord factor

– 1st isolated by Robert Koch in 1882

Tuberculosis - LRT

2. Transmission is by respiratory aerosolsa. bacteria are inhaled and then phagocytized and destroyed by macrophages in healthy individualsb. if an infection progresses the host isolates the bacteria in a walled lesion called a tubercle (or granuloma)c. if the disease stops at this point the lesions slowly heal and become calcified and appear on X ray as Ghon complexes

Tuberculosis - LRT

3. If defenses fail at this stage:

a. the tubercle breaks down and bacteria are released into the lungs

b. from the lungs they go the cardiovascular and lymphatic systems

4. Disseminated infection = miliary tuberculosis which overwhelms the body’s defenses

a. sx = weight loss, coughing up blood, malaise

Tuberculosis - LRT

5. At one time TB was called consumption

6. Tx = about 10 drugs available, 2 of the most powerful are isoniazid and rifampin which must be taken for 6 to 9 months

7. Vaccine = BGC (bacille Calmette Guerin) an attenuated vaccine of M. bovis - cows

Tuberculosis - LRT

Tuberculin Skin Test• Purified proteins from the bacteria are injected

cutaneously• This reaction appears as a hardening and redness

around the injection site• A positive test does not necessarily mean you have an

active disease• In young children a positive rx may be a probable

active case• In older individuals a positive rx may indicate previous

infection or vaccination and not necessarily an active case

Pneumonia - LRT

Pneumonia is a microbial disease of the bronchial tubes and lungs

• Many different organisms cause pneumonia – bacteria, virus, fungi

• Common sxs begin with URT sx – runny nose, congestion

• HA common• Fever and the onset of lung sx follows• Lung sx = chest pain, fever, cough, production of

discolored sputum, rapid and labored breathing• Severity and speed of onset of sx varies w/ pathogen

Pneumococcal Pneumonia

• Usually develops in people who are already ill• Pathogen = Streptococcus pneumoniae

formerly known as Diplococcus pneumoniaea. Gram positive coccus

b. Also causes otitis media, meningitis, sepsis

c. Has a capsule which makes it resistant to phagocytosis and can be differentiated into 90 different serotypes


3. Involves the bronchi and alveolia. the alveoli fill with RBCs, neutrophils, and fluid from the surrounding tissues, fluid interferes with O2 uptakeb. sputum – rust colored from blood coughed up from the lungsc. Pneumococci can invade the bloodstream, pleural cavity and meningesd. if the entire lobe of the lung is involved = lobar pneumoniae. if both lungs are involved = double pneumonia


4. Sx = high fever, chest pain, persistent cough, rust colored sputum, increased pulse, and difficulty breathing

5. For the elderly there is a 20% mortality rate

6. The initial diagnosis is made by X-ray

7. Laboratory dx is by isolation and id based on alpha hemolytic streptococci inhibited by optochin, bile solubility, and serological tests


8. Tx = penicillin, antibiotic resistance is increasing

9. A purified capsular vaccine consisting of capsular material from 23 serotypes is available

Primary atypical (walking) pneumonia

• Pathogen = Mycoplasma pneumoniae

a. no cell wall therefore no gram stain, no sensitivity to penicillin, irregularly shaped small bacteria

2. The infection is common in children and teenagers and is rarely fatal

3. Sxs = low grade fever, cough, HA

a. sxs may last for 3 weeks or longer

Primary atypical (walking) pneumonia

4. Dx = isolates from throat swabs and sputum grown on media containing horse serum and yeast extract produce fried egg colonies that are so small you need magnification to see them, PCR, and serological tests

5. Tx = tetracycline or erythromycin

Legionellosis or Legionnaire’s Disease

• Legionella pneumophilia – aerobic, gram negative rod

• First discovered in1976 when a series of deaths occurred among members of the American Legion who were at a convention in Philadelphia

a. High risk groups are men over 50 who are heavy smokers and abuse alcohol and are chronically ill


3. The organism grows in natural waters, air conditioning cooling towers, whirlpools, humidifiers, showers, fountains, hospital water lines and is resistant to chlorinea. forms protective biofilmsb. can replicate in macrophages and amoebas

4. Sxs = high fever (40.5 C), dry cough, general sxs of pneumonia


5. Transmission is airborne, no human to human transmission

6. Dx = culture on selective charcoal yeast medium, examination of respiratory secretions

7. Tx = erythromycin and other antibiotics

Fungal diseases of the LRT

• Many of the serious fungal diseases of the LRT represent systemic mycosis

• Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioides immitis primarily infect the lungs

• Most infections are asymptomatic and resolve without antimicrobial therapy

a. Sometimes these fungi spread to secondary sites causing more serious disease

Fungal diseases of the LRT

4. Each type of mycosis is restricted to a specific geographical region

5. These 3 fungi are dimorphic and go through a saprobic and parasitic phase

6. The saprobic phase of all 3 fungi grow in the soil where they fragment or form conidia

7. Airborne transmission of these conidia into the respiratory tract triggers the parasitic phasea. the parasitic phase can lead to the development of spherules or formation of yeast like forms

Coccidioidomycosis aka valley fever or San Joaquin valley fever in

Calif.• Coccidioides immitis • Arthroconidia in the soil can grow into hyphal

filaments or be transmitted by the wind to cause infection esp. during dust stormsa. arthroconidia are inhaled into the bronchioles and alveoli and develop into thick walled spherules, endospores develop within the spherules (Pg. 735) b. when the endospores are released they spread in the tissue and form new spherules

Coccidioidomycosis

3. Sxs = chest pain, fever, chills, dry cough, sore throat, in less than 1% the disease resembles TB going throughout the body

a. can produce abscesses throughout the body that can be life threatening

a. need to isolate the pathogen to distinguish the disease from TB

Coccidioidomycosis

4. Dx = made from identifying spherules in tissue or fluids

5. Tx = progressive disease cases may require hospitalization and lobectomy

a. the antifungal drug amphotericin B or fluconazole suppresses infection

Blastomycosis

• Blastomyces dermatitidis – found in the Mississippi valley

• Sxs = resembles an upper respiratory viral infection; persistent form: cough, chest pain, fever, chills, night sweats, malaise

• Inhalation of spores can lead to infection of the lungs and produce bronchopneumonia– Can spread fast and go to other parts of the body

including the skin where cutaneous ulcers can appear

1) Extensive abscess formation and tissue destruction

Blastomycosis

4. Dx = isolation of fungus from pus and biopsy specimens

5. Tx = Amphotericin B

Histoplasmosis –resembles TB

• Histoplasma capsulatum a. Yeast like in body tissue

b. Filamentous mycelium in soil or media

c. Found in macrophages where it lives and multiplies

• Found in US states next to Mississippi and Ohio rivers

• Transmitted by aerosolized bird or bat feces containing fungal spores that are inhaled

Histoplasmosis

4. Sxs:a. the acute form may be asymptomatic or symptomatic

1) if symptomatic – fever, coughb. without recovery it can become chronic and lead to progressive pulmonary disease

1) progressive form – fatigue, malaise, and enlargement of the spleen and liver

Histoplasmosis

5. Dx = isolation of the pathogen in tissue specimens, clinical signs and history, serological tests

6. Tx = Amphotericin B or Itraconaxole

Pneumocystis pneumonia

• Pneumocystis jiroveci (formerly P. carinii)– Resembles both a protozoan and a fungus but RNA

analysis links it yeasts (pg. 737)– Can be found in healthy lungs and show no sxs– Exists as thick walled cysts in the lungs– Opportunistic fungi that leads to microbe and

exudate filled alveoli leading to a loss of gas exchange

– Immunosuppressed px more at risk1) Primary indicator of AIDS – 90% AIDS pxs infected

Pneumocystis pneumonia

2. Sxs = shortness of breath, fever, dry cough, fatigue and weight loss

3. Dx = detection of cysts in sputum samples

4. Tx = trimethoprim - sulfamethoxazole which has very toxic side effects

Viral Diseases of the LRT

Respiratory Syncytial disease• Respiratory syncytial virus (RSV) – most common

cause of bronchitis, bronchiolitis, and viral pneumonia among infants and young children, life threatening pneumonia among the elderly

• Transmission is by respiratory secretions• Sxs:

– Young children – fever (if bacterial complications), pharyngitis– Infants – cough, wheezing, malaise

• Tx = for severe cases ribavirin is available

Viral Diseases of the LRT

Influenza • Influenza viruses are members of the

Orthomyxoviridae• Transmission is by direct or indirect contact• The virus infects the bronchi and bronchioles• Illness is often severe with sxs lasting 3-5 days• Sxs = chills, fever, muscle aches, HA,

pharyngitis, dry coughing, sneezing, chest pains

Influenza

6. Influenza virus has an envelop with 2 types of projections – H – spikes (hemmaglutinin) and N – spikes (neuraminidase)

a. antibodies against influenza virus are directed at these spikes

b. viral strains are id by the variation in the H and N antigens

1) the different forms of Ags are assigned #s ex. H1N1 virus

Influenza

6. c. each number change represents a major alteration in the protein makeup of the spike and are called antigenic shifts d. minor variations are called antigenic drifts

7. Tx = serious cases of influenza can be treated with rimantadine early in the infection otherwise drugs to relieve sxs are the only recourse

Chapter24

Documents

Transcript of Chapter24