MICROBIOLOGY
Upper respiratory system
Nose, Pharynx, Middle ear and Eustachian tube, Nasolacriminal duct
Lower respiratory system
Larynx, Trachea, Bronchial tubes
Trachea and bronchial tubes contain ciliated mucous and prevents microorganisms from reaching the lungs by moving them up to the throat
Alveoli (1 cell thick sacs where gases are exchanged)
If microorganisms reach the lungs alveolar macrophages phagocytize them
Pleura (a double layered membrane that surrounds the lungs)
Normal microbiota of the lungs
Upper respiratory tract
The pathogenic microbes are prevented from growing too large due to competition from non pathogenic microbes
Lower respiratory microbes:
Cilia sends microbes to the throat
Bacterial Diseases of the Upper Respiratory Tract
Sore throat, Scarlet fever, Diphtheria, Otitis Media
Sore throat
subacute
Streptococcal pharyngitis (strep throat)
Caused by Streptococcal pyogenes which also causes impetigo, erysipelas and acute bacterial endocarditis
S. pyogenes is able to resist phagocytosis
It releases an enzyme called streptokinase which can lyse fibrin clots (this stops blood from clotting)
It also releases streptolysins which are cytotoxic to tissue cells, RBC's, and leukocytes
Not all sore throats are caused by S. pyogenes they can be caused by other bacteria and viruses Symptoms: Local inflammation, fever, pain in the throat May cause tonsillitis, Swollen lymph nodes
Spread by respiratory secretions
Scarlet fever
Occurs when a bacteriophage has injected its genetic material into a S. pyogenes bacterium
This causes the S. pyogenes to release an erythrogenic toxin
Erythrogenic toxins produces redness of the tongue as well has a rash on the skin
The tongue eventually loses its upper membrane and the tongue becomes red and large
The tongue may also look like a spotted strawberry
This is a rare disease and goes away on its own Diptheria:
Caused by Corynebacterium diphtheria
Starts with a sore throat and fever, followed by general malaise and swelling of the neck When you get a DTP shot, the D stands for Diptheria Most people have a harmless strain of this in their throat
Characteristic sign of diphtheria is a grayish membrane that forms in the throat in response to the infection
The grayish membrane is made up of fibrin, dead tissue and bacterial cells and can block the air passages so air cannot get to the lungs
Can also release a toxin that gets into the blood and interfere with protein synthesis
It can cause kidney and heart failure or it may affect the nervous system and cause paralysis
Spread by droplet infection
Usually there are 5 or fewer cases per year
When you get a tetanus shot you usually get this in it also.
Cutaneous diphtheria
Usually occurs in American Indians and lower income people
Diphteria enters a wound or similar skin lesion
Causes slow healing skin lesions that are covered by a gray membrane
The toxin does not enter the blood stream
Otitis Media (Ear ache)
An infection of the middle ear
Pathogens in the ear form pus which puts pressure against the eardrum causing it to become swollen and painful
Occurs mainly in young children due to the Eustachian tube which drains the middle ear being horizontal so pathogens don't drain down into the throat
Otitis media can be caused by many different bacteria and viruses
The most common bacteria is S. pyogenes
Antibiotics have been given for years but it is not known if they are affective
Viral diseases of the upper respiratory tract
The common cold
Most common cause is a rhinovirus
Second most common cause is coronavirus
Cold viruses prefer temperatures that are slightly lower, so they infect areas close to openings such as the nose
One rhinovirus is enough to cause a cold
It is not known how the cold virus is spread
Antibiotics are not useful on colds
There is no evidence that cold weather causes colds
If you don't treat a cold it goes away in 7 days, if you do treat it, it goes away in a week Less common in old people because they build up an immunity to it
Symptoms:
Sneezing, runny nose, congestion, usually no fever Bacterial diseases of the lower respiratory tract
Pertussis, Tuberculosis, Bacterial Pneumonias, Melioidosis
Pertussis
The P in DTP vaccine which works until you are about 12 years old
Bordetella pertussis is also known as "whooping cough"
Initial stage:
Catarrhal stage looks like a common cold
The bacteria attaches to the ciliated cells in the trachea where it prevents the cilia from moving then destroys the cell
Paroxysmal stage: This causes mucous to build up which then causes the infected person to struggle to cough up the mucous
A person then goes through a coughing episode which can last up to one minute.
The gasping for air between coughs causes a "Whooping sound"
The coughing can be severe enough to cause broken ribs in young children
Tracheal cytotoxin: damages ciliated cells
Pertussis toxin: Enters the bloodstream and causes systemic problems
Tuberculosis
Convalescence stage: Lasts for months and ends with the person getting better
Caused by Mycobacterium tuberculosis
Usually caught by being inhaled
If it makes it all the way down to the alveoli it is usually phagocytized by a macrophage in the alveoli If some of the of the tuberculosis survives inside the macrophage it starts to reproduce
This causes the macrophage to release chemicals that signal other macrophages to come to the area The extra macrophages form a layer around the tuberculosis bacteria (an early tubercle) and release chemicals (enzymes and cytokines) that cause a lung-damaging inflammation
A few weeks later the macrophages die and symptoms appear.
The tubercle bacilli are released forming a caseous center in tubercle.
Caseous means the dead macrophages appear as a soft, white dead cell mass The tuberculin bacterium remains latent at this stage The dead mass of macrophages eventually becomes calcified
The caseous center enlarges and starts to turn to liquid in a process called liquefaction
Eventually the tubercle breaks open and the TB enters the blood stream where it can go and affect other organs
Pneumonia
Pneumonia is an inflammation of the lung
There are several types of pneumonia
Most pneumonia are caused by bacteria
The most common bacterial pneumonia is Streptococcus pneumonia and is therefore aka typical pneumonia
Atypical pneumonia has slower onset, less fever and chest pain
Other pneumonias can be caused by viruses, fungi, protozoans are called "atypical pneumonia"
Pneumonias can also be named after the area of the lung they infect
Lobar pneumonia only affects a single lobe of the lung, usually caused by S. pneumonia
Bronchopneumonia: the alveoli next to a bronchi is affected
Pleurisy is caused by different pneumonias and the pleural membranes are infected
Pneumococcal Pneumonia
Caused by S. pneumoniae which also causes otitis media, meningitis and sepsis Affected the bronchi and alveoli
The cells pair together and form a capsule around it so it can resist phagocytosis
Symptoms are high fever, difficulty breathing and chest pain
The lungs appear red due to dilation of blood vessels
The alveoli fill with red blood cells, neutrophils and fluid from surrounding tissues
A rust colored sputum (fluid from the lungs that can be spat out) is coughed up from the lungs
There may also not be any symptoms present and many healthy people may carry it
How bad someone is affected by pneumococcal pneumonia depends on how well they are able to fight off infections
Haemophilus influenzae Pneumonia
Caused by Haemophilus influenzae
Similar to Pneumococcal pneumonia
Usually affects people who are alcoholics, poor nutrition, cancer or diabetes
Mycoplasmal pneumonia (walking pneumonia)
Caused by mycoplasmal pneumonia
It is a bacterial pneumonia that acts like an atypical pneumonia
Symptoms are a low grade fever cough and headache
Legionellosis (Legionaires' Disease)
Caused by Legionella pneumonia which can replicate in macrophages
Symptoms: High fever, cough,
Usually affects: Men over 50, especially heavy smokers and drinkers It cannot be transferred from person to person
The microbe can grow in the water air conditioning cooling systems
Recent outbreaks have been traced to whirlpool spas, humidifiers, showers, and potting soil it has also been found in the water lines of many hospitals due to the low temperatures of hot water in the hospital. Hospitals have put in copper-silver ionization systems to resist this It is also able to resist low levels of chlorine in water It exists primarily in biofilms that are highly protective Pontiac Fever
Also caused by Legionnaire's disease
Symptoms are usually fever, muscle aches, and a cough Self limiting
Psittacosis (Ornithosis)
Caused by Chlamydophila psittaci
First found in psittacine bird such as parakeets and other parrots
It is now known that it can be found from other birds such as pigeons, chickens, ducks and turkeys They form "elementary bodies" which are resistant to environmental stress so the Psittacosis can be transferred through the air.
It is not transferred from human to human,
Usually humans get it by breathing in the dust from droppings of fowl
The birds usually have diarrhea, ruffled feathers, respiratory illnesses, and a droopy appearance Many birds carry the pathogen in their spleen and don't have symptoms unless stressed Pet store employees and people involved in raising turkeys are at the greatest risk of disease Symptoms:
Fever, headache, chills are symptoms.
A person may not even know they have it but then become stressed and makes symptoms appear
If disorientation and delirium occurs it means the nervous system has been affected
Chlamydial Pneumonia
A pneumonia that was first found in college students
Similar to the walking pneumonia
May be responsible for atherosclerosis which is the deposition of fatty deposits that block arteries Transmitted person to person by the respiratory route
Half the U.S. population has antibodies to it meaning it is a common infection
Q Fever
Caused by Coxiella burnetii
Has a wide range of symptoms but 60% of cases have no symptoms at all
In acute cases it can cause high fever, headaches, muscle aches and coughing as well as chronic fatigue for months
Affects the heart 2% of the time
in chronic Q-fever it may cause endocarditis, sometimes up to 5 years after the initial infection. If there were no symptoms in the acute stage then the association with Q fever may be missed It is transmitted from animals such goats, sheep and cattle as well as domesticated animals by ticks is found on the placenta of calves
Humans get it by drinking unpasteurized milk and by breathing it in while a cow is given birth because it Inhaling a single pathogen is enough to cause infection
Melioidosis
Found mainly in moist soil in southeast Asia and northern Australia Affects immunocompromised people, especially diabetics
May appear as an abscess on body tissues that resembles necrotizing fasciitis
Death occurs due to septic shock
Transmission is by inhalation or through puncture wounds and ingestion
Viral Diseases of the Lower Respiratory System
Viral pneumonia
Respiratory Syncytial Virus (RSV)
Influenza (Flu)
Viral pneumonia
Can occur as a complication of influenza, measles or the chickenpox Respiratory Syncytial Virus (RSV)
The most common cause of viral respiratory disease in infants between 2-6 months old
About 4500 infant's die/year due to RSV
It can also be life threatening in older adults and is commonly misdiagnosed as influenza
Usually occurs in the winter or early spring
The virus causes cells to fuse together and form a syncytium which is a large multinucleated cell
Symptoms are coughing and wheezing that last for more than a week
Spread by droplet infection
Most of the time it goes away on its own
Influenza (Flu)
Symptoms are fever, chills, headache, a muscle aches Recovery occurs in a few days
Kills up to 50,000 Americans per year
Influenza Virus
Made up of 8 separate RNA strands of different lengths enclosed by a layer outer protein coat (capsid) which is surrounded by a lipid bilayer called an envelope
In the bilayer there are spikes; one spike is called a hemagglutinin (HA) spikes are sharp and neuraminidase (NA) spikes which look like a golf ball on a tee
There are about 500 HA spikes which allow the virus to recognize and attach to body cells before infecting them
Antibodies are directed at the HA spikes
The hemagglutinin spikes cause blood to clump together when the virus is mixed with blood
There are about 100 NA spikes on a virus
They are responsible for helping the virus break loose after it has infected a cell
Fungal Infection of the Lower Respiratory System
Fungi produce spores that are spread through the air
Some of these can get into the lower respiratory tract
Due to an increase in the number of immunosuppressed people, the amount of people with LRT fungal infections is growing
The fungal infections of the lower respiratory system are
Histoplasmosis, Coccidioidomycosis, Pneumocystis Pneumonia, Blastomycosis
Histoplasmosis
Caused by Histoplasma capsulatum
Found mainly in states along the Ohio and Mississippi rivers where 75% of the population has antibodies to it
In places like main it is extremely uncommon
Starts off in the lungs and may spread to the blood and lymph and cause lesions in almost all the organs of the body
On X-rays it looks similar to tuberculosis
Most of the time there are only mild symptoms
The Histoplamsa does not live in birds but feeds off of their poop It can be found in bats due to their lower body temperature
Humans get it from by breathing it in Coccidioidomycosis
Caused by Coccidioides immitis
Found in Alkaline soils in the Southwest
In California it is known as Valley Fever or San Joaquin Fever
A person can get this by just driving through an area
Most infections are asymptomatic and most people recover within a week
About 50 people die a year from this
Pneumocystis Pneumonia
Caused by Pneumocystis jirovecii
Affects the alveoli
Scientists are not sure if it is a fungus or a protozoan
People who are immunocomprised have symptoms but healthy people usually don't
Immunocomprised people who have Pneumocystis may be the reservoir because it is not found in the environment, animals, or healthy adults
Blastomycosis
Caused by the fungus Blastomyces dermatitidis
Found in the soil in the Mississippi and Ohio River valleys
Kills about 50 people per year
Usually asymptomatic
Begins in the lungs where it resembles pneumonia
Cutaneous ulcers can appear
There may be abscesses and tissue destruction that can lead to significant complications if left untreated. If the infection spreads, it can result in systemic symptoms such as fever, chills, and weight loss, indicating a more severe progression of the disease.