Microbiology Chapter 21

inflammation of mucus membranes of throat

larynx inflamed and infected

inflamed tonsils

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

. 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, cephaloporin is used most often now

10. No good vaccine

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

. 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

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.

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

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)

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

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 – consumpt

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

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

a vaccine used throughout the world is somewhat effective at preventing tb, not used in US, because it invalidates the tb skin test

combined antibiotic therapy, isoniazid, rifampin and pyrazinamide for 3 to 24 months
See pg 671
MDRTB

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

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)

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

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)

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

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

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!

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 ketoconzole is also used

h. If disease is disseminated in other tissues it is very Sserious

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

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 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