3. Chapter 21, Respiratory Diseases
Group a Strep - Streptpcoccus pyogenes, Gram + , usually in
short chains, beta hemolytic on blood agar,
optichin resistant, usually spread by respiratory droplets
1. Pharyngitis, laryngitis, tonsilitis
2. Skin infections – impetigo, erysipelas
3. Scarlet fever – erythrogenic toxin (bacteriophage
dependent)
Reddening of tissue in throat, pinkish skin rash, high
fever
4. Systemic bacteremia (blood poisoning)
5. Toxic shock syndrome –(with Staph.) Toxins in
blood, drop in blood pressure can be fatal
6. Virulence factors
4. Chapter 21, Respiratory Diseases
6. Virulence factors
a. Toxins – hemolysins, erythrogenic toxin (scarlet
fever skin rash)
b. M proteins – prevent phagocytosis, the most virulent
forms of Strep a
c. Hyaluronidase
d. Streptokinase – enzyme that digest blood clots
e. Dnases, proteases
7. Can cause a type of gangrene – flesh eating strep,
necrotizing fascitis
8. Post infection streptococcal complications – immune
system disorders – glomerulonephrtitis, rheumatic fever
9. Treatment – penicillin drug family – synthetics are
best, cephalosporin is used most often now
10. No good vaccine
9. Chapter 21, Respiratory Diseases
Streptococcus pneumoniae – leading cause of bacterial
pneumonia – pulmonary infection, pnuemococcal
pneumonia
1. Gram +, diplococci
2. Virulent if capsulated, resist phagocytosis, serological
variety is based on capsule antigenic differences
3. Infect bronchi, and alveoli, also major cause of ear
infections especially in children (other
leading cause of ear infections in children is
Haemophilus influenza – now have a vaccine for it)
4. Transmission – respiratory droplet
5. Alpha hemolytic, and sensitive to optichin
6. Serious disease and now vaccine is available
7. Treatment is penicillin, however drug resistance is a
problem
12. Chapter 21, Respiratory Diseases
Other bacterial respiratory diseases
1. Bordatella pertusis, Gram - , small, fastidious, rod shaped bacteria,
causes whooping cough
a. Serious to life threatening in children
b. Good vaccine available (newer vaccine has few side effects)
c. Bacteria produces toxins, one attacks the ciliated cells of mucus
membranes, mucus accumulates, severe cough, SEE pg 661
2. Legionella species – environmental Gram – , fastidious rod, causes
pneumonia (naturally drug resistant) can be serious disease with
high fever and pneumonia, airborne transmission, from
stagnant water of air conditioning cooling towers, even whirlpool
spas
14. Chapter 21, Respiratory Diseases
3. Haemophilus influenza - Gram – rod, was leading cause of ear
infections and one of the leading causes of meningitis in children
a. Now have good vaccine, HIB – H. influenza type b
4. Corynebacterium diphtheria – used to be the leading cause of death in
children in us, Gram+, non spore forming rod shaped bacteria, can
be pleomorphic (varying shapes – clubs, Y’s)
a. Vaccine now is against the powerful toxin – exotoxin virulence
factor
b. Toxin affects the epithelium ling of the larynx and pharynx –
sloughed of dead tissue cells and bacteria are called a
psuedomembrane – can obstruct air way and cause
suffocation and death
c. Treated toxin is the antigen used for vaccine
d. Exotoxin production is dependent on lysogenic -bacteriophage –
gene for toxin iscarried on the virus genome
17. Chapter 21, Respiratory Diseases
d. Exotoxin production is dependent on lysogenic -
bacteriophage – gene for toxin is
carried on the virus genome
e. Powerful toxin .01mg can kill a 200# person
antibiotics penicillin and erythromycin kill it, but
need antitoxin to destroy toxin
f. Respiratory droplet spreads i
19. Chapter 21, Respiratory Diseases
Tb, tuberculosis - Mycobacterium tuberculosis causes this infectious
disease
A. Obligate aerobe, acid fast bacteria (waxy outer coating), grows
very slowly and hard to culture, can appear fungal like with
filamentous growth
B. Lipids in outer coating allow the organism to survive in dried
sputum and can be dangerous source of transmission
C. Transmission is by respiratory droplet, and can be a problem in
crowded settings with poor hygiene and health care
(tenements, prisons, institutions)
i. Organism is very resistant to drying – can survive days in
dried sputum
ii. Also very resistant to chemical antimicrobials and
disinfectants (waxy lipids in cell wall)
24. Chapter 21, Respiratory Diseases
D. Disease is normally acquired by inhaling the bacillus
1. Normal healthy individuals easily defeat the
invader
2. Macrophages deep in the lung alveoli bacilli
are ingested and killed
3. If the individual is weak or malnourished, or if
the infective dose is high, then organisms survive in the
macrophages and disease may progress
4. The types of infections vary on the tissues that are
affected
5. Primary TB
a. Organisms grow in lung tissue (677-text),
reproducing in the macrophages, a tubercle
forms – walled off area of infection
26. Chapter 21, Respiratory Diseases
b. Progressive primary TB –
i. The walling off is not effective , the tubercle ruptures,
the bacteria spread and the disease rapidly
progresses
ii. Organisms reach the lymphatic tissue and blood the
organism infects other body tissues and causes
a variety of symptoms
iii. Wasting away of body – consumption
27. Chapter 21, Respiratory Diseases
6. Secondary TB
Sometimes the walling off is effective, but then later the
tubercle lesions are source of infective bacilli that then
spread - reason for tb tests that are positive and the
need for chest xray
Tuberculin skin test – purified protein extract of tb bacilli
injected under skin, if person has been exposed to tb, the site
of injection is red and swollen, indicative of delayed
hypersesitivity reaction (t cell mediated hypersensistivity)
29. Chapter 21, Respiratory Diseases
7. BCG TB vaccine – a vaccine used throughout the world is
somewhat effective at preventing tb, not used in US,
because it invalidates the tb skin test
8. Treatment of TB - combined antibiotic therapy, isoniazid,
rifampin and pyrazinamide for 3 to 24 months
See pg 671
MDRTB
30. Chapter 21, Respiratory Diseases
Viral diseases of the respiratory tract
1. Viruses are difficult to identify – obligate intracellular
parasites
2. Many viruses cause respiratory diseases and often
these viruses are never identified. There
diagnosis is based on symptomolgy.
3. If a patient has pneumonia symptoms – and no
bacterial cause is identified – it is called viral
pneumonia (therapy is supportive, no antibiotics
are effective – though newer antivirals hold some
promise – ribavirin)
4. Virus respiratory infection would best be prevented by
vaccination
31. Chapter 21, Respiratory Diseases
Influenza virus – flu
1. World wide problem, pandemics of the flu are notorious,
2. 1918-1919, the flu pandemic killed 20 million people,
viral pneumonia followed by secondary bacterial
infections (no antibiotics then)
3. The reservoir of the virus strain may have been the swine of
the US ( p. 665) In the news – Bird flu
4. The influenza virus
a. RNA virus, with segmented genome, 8 segments of
varying lengths
b. Big complex virus – genome surrounded by protein
coat and then enshrouded by a lipid bi-layer
(p. 663) also note the projections from surface
(spikes)
35. Chapter 21, Respiratory Diseases
i. The membrane is derived from the host cells
ii. The spikes are added to the membrane
iii. The h and n proteins allow attachment to host cell
iv. H antigen reacts with h antibody – which is a
hemagglutination reaction often used in serological test
for id of influenza (agglutination of rbc)
v. N antigen is neuraminidase, enzyme, may assist the virus
from seperating from host cell at release stage of
replication
36. Chapter 21, Respiratory Diseases
vi. Viral strains are identified by variations in h and n
antigens. Antigenic shift –
genetic mutation, resulting in different protein
configuration of h and n antigen.
vii. Antigenic shift of these proteins, probably due to the
segmented genome and resulting genetic
recombination possibilities, results in antigenic
drift –
viii. The strains of flu vary and the immunization or
natural immunity may offer no help against a
new strain that has arisen by antigenic shift (old
ab of previous flu
old immunization is not specific enough against the new virus
and its changedantigenic nature)
37. Chapter 21, Respiratory Diseases
ix. Strains of flu are designated a, b, and c, type a are the
worst and most virulent and cause pandemics
x. Flu vaccines are multivalent – vaccine has ag for several of
the current circulating strains
xi. Vaccines are derived from embryonated egg cultures and
are 70-90% effective
5. Respiratory droplets spread the flu and it is highly
contagious
6. Mortality is not usually high – at risk population is the very
young and the elderly – recommended for regular
immunization
38. Chapter 21, Respiratory Diseases
7. Mortality in large outbreak is due mainly to secondary
bacterial infections – staph and strep
8. Drugs for treatment of flu
a. Amantadine, and rimantadine given early – reduce
symptoms
b. Neuraminadase inhibitor (tamiflu), taken early reduce
symptoms
9. Vaccines are the best prevention
39. Chapter 21, Respiratory Diseases
Other viral infections of respiratory system
1. Common cold – rhino virus (rhino means nose), corona
virus (virus with a ring of spikes around them), other
unidentified viruses
a. Young people get a lot of colds and develop
immunities
b. Older people get fewer colds as they develop
immunity to them over time
2. Chest cold – adeno virus, croup like symptoms
3. Common cold causes most work absenteeisms (2nd is
back injury)
4. SARS, Hanta, Mycoplasmas, Oh so many more!
40. Chapter 21, Respiratory Diseases
Fungal infections of the respiratory system
1. Coccidiomycosis – causative agent ,Coccidioides immitis a
dimorphic fungus (p. 580) (fig. 19.9 and 19.10)
a. Arthrospores are found in dry alkaline soils of desert
southwest – San Joaquin valley fever
b. Transmitted – inhalation of spores – watch out for
dust storms in the New Mexico and Arizona desert
(endemic areas)
c. Chronic respiratory symptoms similar to tb
d. Disease is usually mild and self recovery in few
weeks
e. Tb like and must culture organism to get positive id
f. Amphotericin b for serious cases – but quite toxic
g. Less toxic ketoconazole is also used
h. If disease is disseminated in other tissues it is very
Sserious
41. Chapter 21, Respiratory Diseases
Fungal infections of the respiratory system
2. Histoplasmosis – causative agent is Histoplasma capsulatum, a
dimorphic fungus
a. Arthrospores are found in bird and bat droppings – particular problem in
farm workers and spelunkers – mold grows in the droppings
b. Transmission – inhalation of arthrospores
c. Chronic respiratory infection, somewhat tb like, produces a much more
cloudy chest xray than tb
d. Rare disseminated form is highly fatal
e. Treatment for systemic histo is ketaconazole , amphotericin b has lots of
side affects
3. Blastomycosis – causative agent is Blastomyces dermatitidis, a
dimorphic fungus
a. A soil fungus found in central us , grows in the soil and leaf
mulch of forest floor
43. Chapter 21, Respiratory Diseases
b. Lung infection, that can spread rapidly
c. Most people are asymptomatic but a few die if it becomes
systemic
d. Can have skin lesions
e. Isolation is essential to diagnosis
f. Treat same as histo
Pneumocystis pneumonia - Pneumocystis carinii , a very
strange microbe, protozoan or fungus?
Maybe a closely related organism to the yeasts
1. Causes pneumonia in immunocompormised hosts (aids,
people with transplants or cancer)
2. Treat with trimethoprim
