Respiratory System Infections

Question 1

Streptococcal pharyngitis

Answer 1

Strept throat. Caused by Streptococcus pyogenes.

Gram positive non spore forming cocci in chains. Group A B-hemolytic. It is catalase negative and sensitive to Bacitracin. Contains M protein in cell wall, which forms pili for attachment, along with capsule, which helps resist phagocytosis.
Sx: pain, reddening of pharyngeal epithelium, swollen lymph nodes, fever and malaise. Some victims experience nausea/ vomiting.
Dg: throat culture on blood agar, A disk sensitivity to bacitracin, and rapid strept test (MCA).
Tx: penicillins and cephalosporins relieve sx, eliminate organisms, and prevent further complications

Upper respiratory infection

Question 2

Scarlet fever

Answer 2

Strept throat & body rash due to erythrogenic toxin from S. Pyogenes carrying a specific prophage.

Sx: sore throat, vomiting, fever, strawberry tongue, and body rash.

One attack build long lasting immunity to toxin, but not organism. Homes used to be quarantined in cases of scarlet fever, and serological tests were performed to confirm disease and check for susceptibility. No longer routinely done.

Upper respiratory infection

Question 3

Rheumatic fever.

Answer 3

A tissue destroying hypersensitivity that develops in 3% of untreated cases of strept/scarlet fever.

Initial exposure induces production of ASO antibodies in response to Streptolysin O antibodies that cross react with tissues such as heart valves and glomerulus in the kidneys and result in further heart valve damage as well as Brights Disease. Disease progresses in three stages with high levels of ASO antibody.

Dg: symptomatic and ASO antibody titers.
Tx: long acting penicillin analogs and anti-inflammatory agents.

Some immunity due to the hypersensitive reaction. But some ppl are in danger of SBE (subacute bacterial endocarditis) where an individual produces more ASO Ab in response to A-hemolytic bacteria that are found in oral cavity. Rheumatic fever victims are given oral antimicrobic prior to dental work, which can lead to bacteremia and provoke an immune response.

Upper respiratory infections.

Question 4

What are the stages of rheumatic fever?

Answer 4

1. Strept throat with normal symptoms.
2. Latent period- no observable Sx for 1-3 weeks
3. Rheumatic fever- characteristic sx include acutely inflamed heart valves that result in residual heart valve damage, painful swollen joints, skin rash, a chorea (muscle tremors)

Question 5

Diptheria

Answer 5

Corynebacterium diptheriae.
Gram positive short rod, exhibiting palisade arrangement and containing metachromatic (volutin) granules. Organism lodges in oropharynx resulting in inflammation, which forms the diptheric membrane and can spread to the epiglottis, trachea, and bronco resulting in respiratory distress. Produces an exotoxin that can cause heart and kidney damage as well as affect PNS.

Transmission: droplet infection with an incubation period of 1-10 days

Sx: sudden fever, sore throat, malaise.

Dg: symptomatic, toxin test, culturing and identifying the bacterium by gram stain and biochemical tests.

Tx: antimicrobic chemotherapy and antitoxin.

Prevention: DPT, part of infant immunization schedule. Administered three times, consists of killed Bordetella pertussis cells, precipitated diptheria toxoid, and tetanus toxoid.

Question 6

Psittacosis

Answer 6

Parrot fever. Caused by Chlamydia Psittaci.

Avian bird infection is transmitted to humans by droplet infection, usually after being in direct contact with infected birds. Incubation period of 7-10 days.

Generally confused with the flu, sx: headaches, chills, fever, loss of appetite and sore throat.

Dg: complement fixation serological test and demonstration of the organism cultured on chick or dick embryos.

Tx: tetracyclines, sulfonamides, erythromycin

No vaccine and little immunity.

Imported birds are quarantined and poultry workers may acquire disease from domesticated birds and fowls.

Question 7

Otitis Media

Answer 7

Middle ear infection.

Generally caused by Streptococcus pneumoniae, Hemophilus influenza, Brahammela catarrhalis, Strept Pyogenes and Staph aureus.

Occurs predominately in small children, caused by blockage of Eustachian tube. As the skull enlarges, Eustachian tube becomes less crimped and infections generally stop. Tubes can be placed for drainage in persistent infections.

Sx: sharp pain, reddened bulging TM
Tx: amoxicillin
Prevention: HIB vaccine may help

Little to no immunity.

Question 8

Talk about respiratory infections

Answer 8

Usually considered airborne infections affecting lungs, nasopharynx, and other respiratory systems. Most common portal of entry is nasal or oral cavity.
Transmission is usually by droplet infection: sputum, saliva, respiratory secretions; aerosols such as jet sprays of coughing or sneezing; infected dust and fomites.

Generally upper or lower infection.

Question 9

Acute rhinitis

Answer 9

Common cold. Commonly cause by Rhinoviruses (RNA) mostly. Also by corona viruses, Adeno viruses, respiratory syncytial virus (RSV), and parainfluenza.

Inflammation of nasal mucosa resulting in profuse watery nasal secretions, sneezing, coughing, and watery eyes. Self limitations disease, but may lower resistance to bacterial invasions of sinuses and ears.

Transmission: mainly hand to hand contact and droplet infection. Incubation period of 72 hours.
Sx: above mentioned, plus headache, slight fever, sore throat, cough

Watery secretions bring interferons and IGAs, and probably help bring infection under control by washing away virus.

Dg & tx: symptomatic- antihistamines, decongestants, aspirin is ok, Tylenol/Motrin.
Immunity: immunity to cold up to 2 months, immunity to specific rhinovirus serotype for up to 2 years. Most prevalent infectious disease of humans worldwide.
Prevention: hand washing and avoiding contact with infected persons

Question 10

Mumps

Answer 10

Contagious parotitis. Caused by mumps virus, a paramyxovirus- no cell wall.

Transmission: airborne with incubation of 10 days

Sx: swollen and sore throat due to infection of parotid glands.
Dg & tx: symptomatic
Prevention: accomplished by MMR at 15 mos.
prior to immunization, secondary bacterial infections and Danger of sterilization in young adults was common.

Question 11

Thrush

Answer 11

Oral candidiasis. Opportunist infection caused by Candida albicans.
Infection is limited to epithelium by can occur on tongue, oral mucosa, and oropharynx. Occurs when CMI is not fully functioning, usually in newborns, diabetics, alcoholics and immunosuppressed. Oral antibiotics might kill off natural flora (streptococci and lactobacillus) that keep yeasts in check.
Tx: oral antifungal, such as Griseofuvulin. Systemic infections treated with amphotericin B

Question 12

What is the LRT

Answer 12

Larynx, trachea, bronchus and bronchioles, and alveoli. Contains no normal inhabitants. No competing microbes for defense, so only defended by immune system, alveolar macrophages, and secretory IgA. Invasion of LRT includes inhalation of fungal spores & bacterial spores infecting the URT and descending into LRT and invasion via circulatory system.

Question 13

Whooping cough

Answer 13

Bordetella pertussis and Bordetella parapertussis gram negative rod bacteria.

Disease is characterized by crowing sound or whoop upon inspiration.
Incubation period of 5-21 days.
3 stage disease.

Dg: cultivation of cough on plate of Bordet- Gengou agar which positive samples will produce silvery colonies on.

Tx: erythromycin, O2 support, and good nutrition.

Prevention: DPT vaccine which contains killed pertussis cells or crude extracts from them. Children can suffer from endotoxin components of these extracts , resulting in high fever and possible neurological damage. There is a vaccine compensation act that provides for DPT liability.

Question 14

What are the three stages of whooping cough?

Answer 14

1. Catarrhal period- 2 weeks with mild sx resembling a cold.
2. Paroxysmal stage- rapid violent uncontrollable spells of coughing. Lasts about 2 weeks. Caused by B. Pertussis attaching to surface of bronchi and producing secretions that cause coughing. Severeness of cough can cause hemorrhage of eyes and ears and brain, and can lead to deafness blindness and brain damage.
3. Convalescence- takes weeks or months for body to recovery from malnourishment. Complications occur with secondary infections.

Question 15

Pneumococcal pneumonia

Answer 15

Caused by Strept. Pneumoniae and accounts for 95% of pneumonia. Gram positive coccus that appears in pairs or short chains. Produces capsule that is infectious. 75 different serotypes (strains) based on polysaccharides comprising the capsule.

Question 16

Acute lobar pneumonia

Answer 16

Severe illness with sudden onset and tendency in non fatal cases toward recovery (rapid, 24 hours) caused by strept. Pneumoniae. Mortality rates are high in adults over 65.

Air sacs in lungs fill with fluid as pneumococci multiply. Secrete pneumolysin O which damages host cell membranes. Alveoli are close to bloodstream, which can cause infection in bloodstream resulting in thick, rust colored sputum due to lung consolidation of fluids. Pleurisy and rattling are observed upon osculation. Victim may become cyanotic.

Transmission: airborne with droplet infection from infected carriers.

Sx: mild fever, severe shaking chill, chest pain, and fever.

Tx: penicillin or penicillin analogs.

Dg: symptomatic, chest x ray, isolation of organism from sputum, bile solubility (tx an isolated colony on a Petri disk or broth culture of isolate with 5-10% bile or desoxycholate reagent. Colonies will dissolve in 30 minutes because organism is the only A-hemolytic bacterium affected by bile) and P disks (disk of ethyl-hydrocuperine is placed on plate. A large zone of inhibition will be present for this organism because it is the only A-hemolytic organism affected by this reagent).

There used to be a serological test- the Quellung reaction or Newfield test- used to determine which serotype was causing the disease.

Prevention- polyvalent pneumococcal vaccine given mainly to elderly. Pasteurization and advent of microbes has diminished number of cases of pneumonia.

Question 17

What are other bacterial that can cause pneumonia?

Answer 17

Hemophilus influenzae- gram negative short rod. Primarily in children. Sx similar to pneumococcal pneumonia without chills and pain. Children can also contract meningitis from this organism.

Klebsiella pneumoniae- gram neg short rod that causes infection in HIV, alcoholics and diabetics, and immunosuppressed/cardiopulmonary disease. Sx: prolonged chills scarring and tissue damage to the lungs with a high mortality rate.

Pseudomonas aeruginosa- gram neg short rod. Opportunist. Causes the disease in compromised host such as cystic fibrosis.

Question 18

Mycoplasma like pneumonia

Answer 18

Walking pneumonia caused by mycoplasma pneumoniae.

Characterized by cough, malaise, slight sputum, and little consolidation of lung fluid and no tissue damage. Patient remains ambulatory.

She: requires cultivation of sputum sample on tissue culture for 10-30 days.

Tx: tetracycline.

Mycoplasmas, lack peptidoglycan in cell walls.

No vaccine and preventative measures. Some immunity follows recovery. Milder form is Pontiac fever.

Question 19

Legionellosis

Answer 19

Legionaires disease. Legionella pneumophilia.
Transmission is airborne. Occurs frequently in spring and summer months near construction sites.organism is also found in air conditioning cooling towers , illustrating need for chlorination of water supplies and humidification systems in buildings.

Question 20

Tuberculosis

Answer 20

Consumption, TB
Caused by mycobacterium tuberculosis, an acid fast rod due to waxy lipid mycolic acid in the cell wall.
slowly progressive disease that has been in decline in US, but is still a leading cause of death in under developed countries. Has been significant rise in US since 1989, called reactivation TB. New antimicrobic strains of TB are also emerging.
Transmission: airborne.
Sx: early to moderately advance cases have none. Later sx include pleurisy, vague chest pains, cough, weight loss, fatigue, hoarseness, night sweats, and hemoptysis (coughing of blood)
Dg: mantoux skin test, appearance of acid fast rods in sputum, and chest X-ray.
Tx: prolonged therapy Rifamino and INH, ethambutol, and strrptomysin.
Prevention:BCG (attenuated bovine strain developed by calmette and guerin) used in other parts of world, generally 60-80% effective by inducing a CMI response.

Question 21

Explain how TB affects the body

Answer 21

The bacterium is inhaled in droplets, penetrated to alveoli and is phagocytize by alveolar macrophages. That macrophage cannot destroy the microbe, so it grows within the phagocytic cell. Tubercules form when mycobacteria are surrounded by layers of macrophages and an outer layer of lymphocytes. The bacilli usually become dormant in the tubercule and remain that way unless the antimicrobic kills them and the tubercule calcifies. If the CMI is not strong enough to stop the multiplication of cells, the initial tubercule becomes larger and more tubercule a develop. The macrophages and lung tissue cells inside enlarged tubercules begin to die because of toxic lipids from the organism or lack of oxygen. They fuse together and form a cheese like mass of dead tissue. Eventually several tubercules coalesce to form a mass of dead tissue large enough to show up on an XRay called the Ghon Complex. As the area of dead tissue expands, it may erode the way of the bronchus resulting the release of the acid fast cells in sputum.

Question 22

Hemophilus influenza B

Answer 22

The causative agent of epiglottitis, pneumonia, meningitis, and joint disorders in children. It can also be a secondary invader in other childhood infections. Produces polysaccharide capsule which aids in Invasiveness.

Prevention: HIB vaccine has been produced through biotechnology and contain capsular antigen. Recommended for children between ages 2-6

Question 23

Influenza

Answer 23

Caused by influenza viruses A,B,C. Usually appears in epidemic proportions. A strains- usually every 2-3 years and B strains- 4-6 year cycles. Have a core of single stranded RNA and is surrounded by an envelope with peplomer a of neurominidase and hemogluttinin. These help classify subtypes (H1N1) varying combinations of these peplomer a are called antigenic drift. Incubation period is usually 2-3 days followed by sx of fever, headache, cough, sore throat, muscular aches, malaise, and marked weakness. Secondary complications may kill elderly patients.

Tx: uncomplicated is symptomatic with supportive measures such as rest and nutrition.
Amatidine can shorten duration up to 50% in elderly patients, but has side effects.
Prevention: annual flu vaccine.
Dg: symptomatic

Question 24

Describe the four influenza outbreaks mentioned

Answer 24

1919-1920 influenza Victoria A strain (H1N1) caused 20million deaths worldwide

1957 worldwide human Asian flu was A strain H2N2.

Later in 1968 the Hong Kong flu was the H3N2 A strain.

And again in 1999-1991 the flu outbreak of H3N2 again with three antigenic ally distinct variation were isolated.

Question 25

Reye’s syndrome

Answer 25

Complication of viral infections with use of Aspirin, especially in children.

Sx: loss of consciousness, central nervous system disorders, liver and kidney failure, convulsions, coma, and death.

Question 26

Systemic mycoses

Answer 26

Deep seated final infection of the LRT

All transmitted via airborne means and usually obtained via inhalation of spores. All dg is by skin test because etiological agents provoke hypersensitivity to infection like TB.

Question 27

Blastomycosis

Answer 27

Caused by bladtomyces dermatidis. Dimorphic/ diphasic fungus (mold at 25C and yeast at 37C) primary infection is in lungs, but can spread to rest of body via bloodstream. Disseminated infections are often fatal.
Occurs in US and rural Canada in males between 30-50.

Dg: blastomycin skin test
Tx: amphotericin B (fungi zone)

Question 28

Coccidiomycosis

Answer 28

Cocciodies immitis (San Joaquin fever, desert rheumatism) dimorphism, diphasic fungus prevalent in southwestern US, California, and Central and South America.

Usually produces a mild infection in lungs, but rarely involved meninges, bone, and skin and is fatal. Moder form may produce subclinical effects or may be in apparent or may resemble the sx of mild RI which lasts for a short time and is self limiting.
Dg: skin test
Tx: amphotericin B

Question 29

Paracoccidiomycosis

Answer 29

Paracoccciodies brasiliensis. Dimorphisc/diphasic found most often in South America.

Clinically is similar to blastomycosis, lesions are commonly found in lungs but also in mouth, intestinal tract and lymph nodes of neck.

Dg and tx are same