Microbial Diseases of the Respiratory System

Respiratory System

Division of the Respiratory System

• Upper respiratory system

• Nose and throat

Lower respiratory system

• Lower respiratory system

• Contains the larynx, trachea, bronchial tubes, and lungs

Diseases of the Upper Respiratory System

• Pharyngitis – sore throat

• Laryngitis – infection of the larynx

• Tonsillitis – infection of the tonsils

• Epiglottitis – infection of the epiglottis

Streptococcal pharyngitis

• Streptococcus pyogenes

• Beta hemolysis on blood agar from throat swab

• Sore throat, fever, swelling of tonsils and neck

• Penicillin

Streptococcal throat inection

Hemolytic reactions

Diphtheria

• Corynebacterium diphtheriae

• Fever, sore throat, malaise, swelling of the neck

• Tough grayish membrane forms in the throat from the infection

• DTaP vaccine • Few cases in the US• Erythromycin or penicillin

Diphtheria prevalence

Otitis Media• Middle ear infection• Common in young children• Bacteria enter the middle ear

from the oropharynx via the short internal auditory tube

• Painful swelling of ear drum• Various bacteria cause the

condition, mainly Streptococcus and Staphylococcus

• Children generally outgrow the condition

• Amoxicillin is used but this treatment is currently being phased out to limit resistance

Common cold

• Viral disease of the upper respiratory system• Caused by a variety of viruses; rhinoviruses and

coronaviruses are the most common• Symptoms are sneezing, runny nose, and

congestion• Exact route of transmission is still not clear• Viruses prefer a slightly cooler temperature

hence the upper respiratory system• Self-limiting, 7days or so?

Pertussis (Whooping Cough)

• Bordetella pertussis• Lower respiratory system

disease• Bacterial toxin causes

paralysis of tracheal cilia• Severe coughing to clear

airway• Three stages of the

disease: catarrhal, paroxysmal, and convalescence

• DPT vaccine

Whooping Cough Prevalence in the U.S.

Mycobacterium tuberculosis

Tuberculosis

• Lung infection caused by the acid-fast bacteria Mycobacterium tuberculosis

• Acquired by inhalation

• Strong immune system often will prevent the bacteria from causing infection

• Weak immune system or poor general health can lead to infection and possibly death

Pathogenesis of TB

• Bacteria are ingested by lung macrophages but are not killed

• Bacteria multiply inside the macrophages• Infected macrophages are isolated in the lungs

in lesions called tubercles• The tubercles can rupture and release bacteria

into the body to cause systemic disease and infection to others

• Symptoms include weight loss, coughing blood, loss of vigor, wasting and death

• CONSUMPTION

Treatment

• Long term antibiotic therapy with antibiotic such as isoniazid, rifampin, and pyrazinamide

• Vaccination with the BCG vaccine

• Vaccine effectiveness is questionable; used in much of the world except the US

TB Testing

• Tuberculin skin test is used to screen for the disease

• Test results:+ if you have had TB+ if you have been exposed but never had

active TB+ if you have been vaccinated- never had or been exposed to the

disease

Incidence of TB

• 20,000 new cases in the US each year

• Incidence decreasing in the US

• Estimated 1/3 of the world population is infected

• 10-12 million deaths per year from TB

• Antibiotic resistant strains are emerging

Bacterial pneumonia

• Streptococcus pneumoniae is the most common cause

• Capsule around the bacteria causes virulence

• Symptoms are high fever, chest pain, difficulty breathing

• High mortality rate in elderly patients

• Vaccine is available• Antibiotic treatment with

penicillin

Mycoplasma pneumonia

• Atypical pneumonia caused by the bacteria Mycoplasma pneumoniae

• Bacteria has no cell wall

• More common in young adults (under 40) and children

• Symptoms are low grade fever, cough, headache that may last for several weeks

• Treated with erythromycin and tetracycline

Legionellosis(Legionnaries’ disease)

• Legionella pneumophila • High fever, cough• Air conditioning systems,

and other water features• Spread through air

(aerosol), not person to person

• Philadelphia outbreak 1976 - 221 affected 34 deaths

Spread of Legionnaires’ Disease

Influenza

What is influenza?

• RNA virus that has three classes• Influenza A

– Disease in humans, can cause pandemics

• Influenza B– Inflects humans, less severe than type A

• Influenza C– Infects pigs and humans, generally mild

disease

Structure of the flu virus

• RNA virus

• Outer lipid coat

• Projections on the outer layer– Hemagglutin spikes (H) 16 types– Neuraminidase spikes (N) 9 types

Spikes

• Hemagglutinin spikes• 500 per virus• Allows virus to

recognize and attach to body cells

• Antibodies made to these spikes

• Neuraminidase spikes• 100 per virus• Help virus separate

from infected host cell

Why do I need to get a new flu shot every year?

• Antigenic drift – changes in the structure of the spikes that allow the virus to evade the immune system

• Occurs on an annual basis

• Antigenic shift – major change in the protein of the spikes that creates a virus that is “new” to the human population; little herd immunity; major epidemics

Flu shots/Flu season

Coccidiodomycosis

• Fungal disease of the lungs• Coccidiodes immitis • Endemic to the desert southwest• Causes either no symptoms or mild symptoms,

including chest pain, fever, coughing, and weight loss

• Immune suppressed individuals may develop a TB like disease that can become systemic

• Amphotericin B is used to treat the condition

Coccidioidomycosis