Respiratory Pathogens

Question 1

What is the motility, spore formation, oxygen use, and shape of Mycobacterium?

Answer 1

1. Non-motile
2. Non-spore forming
3. Aerobic
4. Rods

Question 2

What makes Mycobacterium resistant to disinfectants and common stains?

Answer 2

It’s lipid-rich cell wall

Question 3

1. What type of staining is used to identify Mycobacterium?
2. Why is Mycobacterium hard to identify via culture?

Answer 3

1. Acid-fast staining (Not really Gram-positive)
2. It is very slow growing (3-4 weeks)

Question 4

1. What two pathogens of the M. tuberculosis complex infect humans?
2. What other two Mycobacterium cause disease in humans?

Answer 4

1. M. tuberculosis, and M. africanum
2. M. leprae (Leprosy), M. avium complex (MAC)

Question 5

There are two specific MAC bacteria: M. avium and M. intracellulare. Which bug infects which type of patient?

Answer 5

• M. avium* - HIV patients
• M. intracellulare* - Immunocompromised

Question 6

1. What is a defining structural characteristic of M. tuberculosis?
2. How does this contribute to it’s virulence?
3. How is this used in screening?

Answer 6

1. It’s complex lipid cell wall (60% of dry weight).
2. It makes it resistant to antimicrobials, Cord factor participates in production of caseating granulomas
3. It is an important modulator in immune response used in PPD skin test.

Question 7

1. What are the reservoirs for M. tuberculosis?
2. How many people are infected with TB worldwide?
3. What is prominent about TB epidemiology in HIV patients?
4. What is needed for transmission?

Answer 7

1. Humans are the only reservoir
2. ~2 billion - 1 in 3 people
3. It is the leading cause of death in HIV patients
4. Close contact for extended periods of time

Question 8

1. What type of transmission/precaution is necessary for M. tuberculosis?
2. How long is the typical initial bacterial replication phase?
3. What is the risk of active infection after exposure?

Answer 8

1. Inhalation of droplet transmission
2. 3-6 weeks
3. 5% in 1-2 years, 10% lifetime, 10% annually for immunocompromised

Question 9

1. Are people with latent infections contagious?
2. What imaging indicates active disease?
3. What symptoms are present in active TB?

Answer 9

1. No, only active infections are transmitable
2. Dense lesions on x-ray
3. Malaise, weight loss, productive cough, night sweats.

Question 10

1. Describe Granulomas.

Answer 10

1. Areas of activated immune cells that arrest infectious bacteria. Future immune insult can result in “reactivation disease.”

Question 11

1. Suppression of what cytokines and cellular enzymes result in increased risk for reactivation?
2. What is the risk of reactivation in healthy vs. immune compromised patients?

Answer 11

1. TNF-alpha, INF-gamma, iNOS
2. 10% lifetime vs. 10% annually

Question 12

1. What is the result of a PPD test for active disease vs. latent disease?
2. What is the difference in CXR and sputum for active disease vs. latent disease?
3. How contagious are people with active vs. latent disease?

Answer 12

1. Both are positive
2. Abnormal CXR and sputum for active disease. Normal for latent disease.
3. Active disease is highly infectious. Latent disease cannot be spread to others.

Question 13

1. What is the major drawback of the PPD test?
2. What other two tests are quick diagnostic tools for TB?
3. What is the gold standard for confirming TB? Why can this be problematic?

Answer 13

1. PPD skin test doesn’t tell you which species of Mycobacterium you were exposed to.
2. Quantiferon test detects INF-gamma. Sputum sample with microscopy.
3. Culture is gold standard. May take 3-6 weeks.

Question 14

1. What is the PPD a mixture of?
2. What is considered a positive result?
3. How is active or latent infection determined? Can the PPD alone determine this?

Answer 14

1. Tuberculoproteins from the cell wall.
2. Induration of >10 mm using 5 TU of PPD is positive.
3. CXR. No PPD alone is not good enough.

Question 15

1. What are the secreted antigens that are specific to TB that are used by the Quantiferon test?

Answer 15

1. ESAT-6 and CFP-10

Question 16

What type of stain for TB is the following image?

Answer 16

Carbol Fuschin

Question 17

What type of TB stain is shown in the following image?

Answer 17

Ziehl-Neelson

Question 18

What type of stain for TB is shown in the following image?

Answer 18

Auramine-Rhodamine

Question 19

Why isn’t gram-stain effective for TB visualization?

Answer 19

It’s hydrophobic cell envelop (lots of long chain fatty acids = mycolic acids

Question 20

What is the recomended course for acute TB infections?

What is the recommended treatment for latent TB? Why isn’t it entirely effective?

Answer 20

2 months of: Isoniazid, Rifampicin, Ethambutol, and Pyrazinamide

Followed by 4 months of: Isoniazid and Rifampicin

9 months of isoniazid. Doesn’t always sterilize b/c Isoniazid is most effective against replicating bacteria.

Question 21

Why is adherence to TB regimen so critical?

Answer 21

Non-compliance can result in emergency of MDR or XDR strains.

Question 22

1. What does MDR resistance mean? What impact does this have on treatment?
2. What does XDR mean? What impact does this have on treatment?

Answer 22

1. Resistance to both Isoniazid and rifampicin. Requires multiple antibiotics for up to 2 years
2. Resistance to most known antibiotics for TB. Prognosis is grim.

Question 23

1. What type of vaccine is the BCG vaccine? What does the BCG TB vaccine protect against? What does it not protect against?

Answer 23

1. It is a live vaccine. It protects against over disease but not infection and has a varied protection rate.

Question 24

1. Where is *M. leprae *seen in the US? Why?
2. How is Leprosy spread?
3. M. leprae has had a substantial reduction in its genome with 50% no longer coding for proteins. What does this mean clinically?

Answer 24

1. The south. It is endemic in armadillos.
2. By person to person contact. Transmission by inhalation or direct contact with respiratory secretions
3. It has limited metabolic capability and cannot be cultured on laboratory medium. Usually cultured in armadillos or nude mice.

Question 25

1. What are the two main types of leprosy?

Answer 25

1. Tuberculoidal leprosy, Lepromatous leprosy

Question 26

What differentiates Tuberculoidal vs. Lepromatous leprosy immunologically?

Answer 26

Tuberculoidal has a **strong cell-mediated** immune response but _weak humoral response_. (Few bacilli present in tissues) Lepromatous manifests following a **strong humoral response**, but _weak cell mediated response_. (Abundance of bacilli in macrophages)

Question 27

What are the hallmarks physical symptoms of Tuberculoidal leprosy? (3 points)

Answer 27

Extensive peripheral nerve damage and sensory loss Enlargement of nerves They are not infectious due to limited number of bacilli.

Question 28

What are the hallmark symptoms of Lepromatous leprosy? (3 points)

Answer 28

Many erythematous plaques resulting in extensive tissue destruction. Little sensory loss is present. Highly infections due to number of acid-fast bacilli in lesions.

Question 29

Which type of leprosy is depicted here?

Answer 29

Lepromatous

Question 30

What is the following an image of?

Answer 30

Tuberculoid leprosy

Question 31

1. Where is Mycobacterium avium (MAC) commonly found? 2. Who does it commonly infect? 3. How is it commonly contracted?

Answer 31

1. Environmental isolate of soil and water 2. Individuals with HIV creating disseminated disease. 3. Ingestion

Question 32

1. What are the reservoirs for *Micobacterium bovis?* 2. How is it typically contracted? 3. What happens if organisms are inhaled?

Answer 32

1. Cattle and Humans 2. Unpasteurized milk or dairy products. 3. Disease indistinguishable from *M. tuberculosis*

Question 33

1. Who does *Mycobacterium marinum* infect and what is it frequently associated with? 2. How is it commonly acquired? 3. Where is this disease primarily seen?

Answer 33

1. It is an opportunistic pathogen and is associated with skin lesions. 2. Swimming pools and hot tubs. 3. In fish and frogs.

Question 34

1. What is the basic physical structure of *Legionella**?* 2. What is *Legionella's* relationship with oxygen? How does this affect where the infect? 3. What type of people are susceptible to *Legionella*? 4. How does *Legionella* appear on gram-stain? How is this overcome?

Answer 34

1. **Gram-negative, **unencapsulated rod with single polar flagella 2. Obligate aerobes that infect the lungs. 3. Immunosuppressed. It is an **opportunistic pathogen.** 4. They stain poorly and require fuschin rather than safarin.

Question 35

1. What are the unique growth requirements of *Legionella?* 2. How does *Legionella* derive most of it's energy?

Answer 35

1. They are complex and require **L-cysteine **and **ferric iron.** 2. From breaking down amino acids rather than carbohydrates.

Question 36

1. Legionella are the cause of what two common name diseases? 2. What are the rates of new infection in the US? 3. What percentage of people die after Legionella infection?

Answer 36

1. Legionaire's disease and Pontiac Fever 2. 8-18,000/year 3. 5-30%

Question 37

1. What Legionella type is responsible for most human disease? 2. How are individual species differentiated?

Answer 37

1. *L. pneumophila* serogroup 1 2. Outer membrane proteins and polysaccharide

Question 38

1. What is the major non-human reservoir for Legionella? 2. What accounts for Legionella's incredible staying power?

Answer 38

1. Water dwelling ameoba 2. Legionella's ability to form biofilms

Question 39

1. Is Legionella also part of normal flora or is it only acquired? 2. How do we contract Legionella from water? 3. Can Legionella be transmitted person to person? 4. Who is most affected by Legionella?

Answer 39

1. They are not part of normal flora. They are typically acquired by **inhalation**. 2. Drinking water alone is not enough, one must **aspirate** contaminated water. 3. **No person to person transmission reported** 4. **Legionella are opportunistic pathogens.** They primarily affect **immunocompromised** individuals.

Question 40

1. Where does Legionella survive within humans? 2. What does Legionella produce to aid in it's survival? 3. What type of secretion system do Legionella use? 4. What does this system do?

Answer 40

1. Within Macrophages 2. Cytotoxins, hemolysins, proteases, endotoxins, and lipases 3. Type IV secretion system 4. Delivers virulence effectors directly into macrophages

Question 41

How does Legionella resist being killed by macrophage reactive oxygen intermediates?

Answer 41

It prevents phagosome-lysosome fusion

Question 42

1. What are the clinical features of Legionaire's disease? 2. Is Legionaire's visible by radiograph? 3. What is the incubation period for Legionaire's disease? 4. What is the prognosis for Legionaire's?

Answer 42

1. Pneumonia, cough, fever, chest pain 2. Yes 3. 2-14 days 4. Fatality common - 5%-40%

Question 43

1. What are the clinical features of Pontiac Fever? 2. Is Pontiac fever visible on radiograph? 3. What is the incubation period for Pontiac Fever? 4. What is the prognosis for Pontiac Fever?

Answer 43

1. Flu-like Illness 2. NO 3. 24-48 hrs after exposure 4. Hospitalization un-common. Fatality rate 0%

Question 44

1. How can Legionella be identified by Microscopy? 2. What culture medium is needed for Legionella? 3. How long might it take to diagnose Legionella by serology?

Answer 44

1. Using a **differential fluorescent antibody** 2. **Specialized media - **Buffered charcoal yeast extract 3. **Up to 3 weeks** for titers to be high enough

Question 45

What organism is pictured below? By what technique? On what medium?

Answer 45

Legionella, by DFA microscopy, on glass slide

Question 46

What organism is pictured below? By what technique? On what medium? Given what "hallmark appearance"?

Answer 46

Legionella, by culture, on Buffered charcoal yeast extract, giving a "cut glass" appearance

Question 47

How can infected water sources be cleared of Legionella?

Answer 47

Chlorine treatment or by superheating

Question 48

1. What are the general physical characteristics of Pseudomonas? 2. What type of pathogen are pseudomonas? Where can they be found? 3. How are they commonly found to exist?

Answer 48

1. **Gram-negative** rods with a polar flagella 2. They are **opportunists** that are ubiquitous to water and soil. 3. As **biofilms** and **microcolonies** on inanimate objects (plastic tubes)

Question 49

What does Pseudomonas use as an energy source?

Answer 49

They oxidize carbohydrates (oxidase-positive)

Question 50

Why is pseudomonas difficult to clear from surfaces?

Answer 50

It is highly resistant to chemical disinfection

Question 51

What is a Gram-negative rod with polar flagella, oxidase-positive, strongly hemolytic, and greenish in color and capable of growing in elevated temperatures?

Answer 51

Pseudomonas aeruginosa

Question 52

Where is P. aeruginosa commonly isolated in hospitals?

Answer 52

Sinks & toilets Dialysis equipment Catheters & Respiratory equipment

Question 53

1. What two types of injuries are commonly infected because of P. aeruginosa's ubiquity in nature? 2. What type of chronic illness patient commonly dies from P. Aeruginosa?

Answer 53

1. Burn patients and puncture wounds 2. Cystic Fibrosis patients with a **mucoid** phenotype

Question 54

1. What are common early life colonization bugs? 2. What is a common late life colonization bug?

Answer 54

1. S. aureus and H. influenzae 2. P. aeruginosa

Question 55

What virulence factors are produced by P. aeruginosa and to what effect for each?

Answer 55

adhesins -- promote binding polysaccharide capsule alginate -- mucoid phenotype Endotoxin -- septic shock Pyocyanin and pyochelin pigments -- release of ROS Exotoxins -- Extensive tissue damage Proteases -- host tissue damage

Question 56

Where does psuedomonas create it's effect relative to host cells?

Answer 56

It remains outside the cell compared to Legionella which is an intracellular pathogen.

Question 57

What is the following image depicting? How is it obtained?

Answer 57

Pseudomonas corneal ulcer obtained by extended wear contacts.

Question 58

1. What is the most effective way to positively ID P. aeruginosa?

Answer 58

1. Culture

Question 59

What is another pseudomonad that causes respiratory infections in CF or CGD patients and what is it sensitive to?

Answer 59

Burkholderia cepacia which is sensitive to trimethoprim-sulfamethoxazole

Question 60

What is another pseudomonad that is a saphrophyte of soil and water and mainly responsible for opportunistic infections?

Answer 60

Burkholderia pseudomallei