ICL 2.4: Legionella & non-TB Mycobacteria

Question 1

what is the basic microbiology of legionella?

Answer 1

aerobic gram (-) bacilli

stains poorly

intracellular bacterium

Question 2

short summary of the epidemiology of legionella

Answer 2

Water-borne infections such as Legionellosis (Legionnaire’s disease; serious) and Pontiac fever (high disease rate but self-limiting)

Question 3

what is the short summary of the pathogenesis, clinical presentation, diagnosis and treatment of legionella infections

Answer 3

80% of cases in people > 40 yrs old

Compromised pulmonary f(x) and low CMI response are risk factors

Nonspecific “flu-like” symptoms: fever, chills, headache, dry cough

diagnosis: urine antigen (LPS) immunoassay
treatment: macrolides (azithromycin) or fluoroquinolones (cipro): must penetrate infected cells

Question 4

in what medium is legionella grown?

Answer 4

requires special culture media

buffered charcoal yeast extract AND cystein and iron

it has a “cut-glass” appearance on BYCE

Question 5

how do we stain legionella?

Answer 5

it stains poorly with gram stain

instead we have to use silver stain

Question 6

what time of the year is legionella most common?

Answer 6

summer and fall

Question 7

what age group is most succeptible to legionella infections?

Answer 7

> 50 years old

Question 8

where is legionella found?

Answer 8

naturally found in lakes and streams, A/C systems, water systems

1. commercial A/C systems like hotels, resorts, health care
2. fountains
3. shower heads/humidifiers
4. produce sprayers at kroger
5. hot tubs
6. hospital devices used for inhalation therapy

Question 9

what is legionella resistant to?

Answer 9

1. high temperature
2. chlorine

it forms biofilms in pipes of all kinds of water systems, yikes

Question 10

is the number of outbreaks associated with drinking water caused by legionella increasing or decreasing?

Answer 10

incidence of legionella outbreaks associated with drinking water is increasing

Question 11

what types of people are most at risk for legionella infections?

Answer 11

1. smokers
2. chronic lung disease patients
3. immunosuppressed individuals (transplants, cancer, AIDS)
4. > 50 years old

Question 12

how is legionella spread?

Answer 12

legionella is found in soil and water – especially iron rich tap water

no person-person spread known to occur!

there’s also no animal reservoir known

Question 13

what is the main legionella species we’re going to talk about?

Answer 13

there’s over 50 legionella species

but L. pneumophilia is what causes 90% of infections

Question 14

what is the shape of legionella?

Answer 14

it’s pleomorphic

so it’s coccobaccilli in tissue but long rods in lab media

Question 15

what’s the pathogenesis of legionella?

Answer 15

macrophages in the lung normally engulf bacteria everyday in an endosome that then fuses with a lysosome and degrades the bacteria

however, with legionella it inhibits fusion with lysosome

Dot/Icm secretion system secretes hundreds of proteins into the inside of the macrophage to disable it so that antigen processing and lysosome fusion is all turned off

this allows the legionella to replicate to super high numbers in the macrophage in legionella-containing vacuole (LCV)

in the meantime, it’s allowing the macrophage to present antigen which recruits new inflammatory cells to the region which cause a strong inflammatory response and is what gives you pneumonia and inflammation in the lungs

ultimately the macrophage is killed

Question 16

what type of organism does l. pneumophilia infect?

Answer 16

L. pneumophilia infects amoebae in the environment then replicates

by infecting amoeba and replicating inside them, it’s protected from chlorine and other inactivating agents

Question 17

what is legionellosis?

Answer 17

aka Legionnaires disease; caused by L. pneumophilia

lots of people are infected but very few show disease

preferentially affects those with underlying pulmonary disease

it’s a pneumonia that causes serious, permanent damage

mortality is 15-20% in healthy people but 7% in immunocompromised people

Question 18

how long is the incubation period of legionellosis?

Answer 18

2-10 days

Question 19

who is more susceptible to legionellosis?

Answer 19

it preferentially affects those with underlying pulmonary disease

Question 20

what are the symptoms of legionellosis?

Answer 20

1. fever
2. chills
3. dry cough
4. headache
5. CXR pneumonia

Question 21

what is Pontiac fever?

Answer 21

cause by L. pneumophilia

affects healthy and high-risk individuals

high disease rate, >90%

it’s self-limiting (2-5 days) and there’s no pneumonia

it’s never fatal!

Question 22

what are the symptoms of Pontiac fever?

Answer 22

1. fever
2. chills
3. myalgia
4. malaise
5. headache
6. dizziness

Question 23

what are the two diseases that can be caused by L. pneumophilia?

Answer 23

1. Legionellosis

2. Pontiac fever

Question 24

what is the pathology of legionella?

Answer 24

it replicates inside alveolar macrophages

lung damage is actually due to cytokine/chemokine responses, not the bacteria itself!

cell-mediated immunity is important for protection though

Question 25

what would a lung tissue sample from a legionella infection show?

Answer 25

there's no white space...it just looks like "moth-eaten" lungs with fluid-filled patches the tissue is all filled with neutrophils and macrophages from the huge immune response that is being mounted on the legionella so it's the cytokine storm thats causing damage and ultimately causing the disease!

Question 26

what are the 2 tests that you can do to diagnose legionella?

Answer 26

1. urine antigen immunoassay | 2. culturing of sputum

Question 27

how does a urine antigen immunoassay work?

Answer 27

used to diagnose legionella infection quickly, only takes 15 minutes! ELISA detects Legionella LPS in patient’s urine but it only detects serogroup 1

Question 28

how does culturing sputum for legionella diagnosis work?

Answer 28

you get sputum and put it on BYCE getting the sputum might be hard though.... it'll be 3-5 days before the colonies are visible ("cut glass" appearance) you need to confirm with direct fluorescent anitbodies

Question 29

what are the clues for diagnosing legionnaire's disease?

Answer 29

1. pneumonia; rales with signs of consolidation 2. CXR abnormalities by the third day of illness; patchy *unilobar* infiltrate that progresses to consolidation 3. fever (> 39∘C) is almost always present 4. hyponatremia = low serum sodium levels <130 mg/L; due to lung damage 5. GI symptoms, especialyl diarrhea 6. neurological findings; especialyl confusion 7. gram stain of respiratory secretions shows many neutrophils but few, if any, microorganisms

Question 30

which drugs do legionella infections not respond to?

Answer 30

legionella doesn't respond to beta-lactam and/or aminoglycoside antibiotics that's because legionella hides out in the macrophages which B-lactam and aminoglycosides can't penetrate

Question 31

how do you treat legionella?

Answer 31

1. macrolides 2. fluoroqinolones legionella are naturally β-lactam resistant because β- lactams don't penetrate macrophages antiobiotics will need to reach the interior of macropahges!!

Question 32

which drugs are macrolides?

Answer 32

1. azithromycin | 2. clarithromycin

Question 33

which drugs are fluoroquinolones?

Answer 33

1. ciprofloxacin | 2. levofloxacin

Question 34

how can we prevent legionella?

Answer 34

reduce Legionella numbers in water supplies! we can do this by: 1. high heat 2. higher chlorine concentration 3. copper-silver ionization 4. surveillance of A/C and water systems

Question 35

FLASHCARD: microbiology, pathology, epidemiology, clinical symptoms, diagnosis and treatment of legionella

Answer 35

MICROBIOLOGY: Aerobic, Gram − rods; BCYE plates PATHOLOGY: Invade and grow in both human alveolar macrophages and free-living amoebae; Prevent lysosome fusion and replicate in special vacuole; Secretes proteins into host cell and triggers strong inflammatory response EPIDEMIOLOGY: Affects only a minority of those exposed (risk factors such as > 50 yrs old and smokers); Causes waterborne infections such as Legionellosis (Legionnaires’ disease) and Pontiac fever (self-limiting) CLINICAL: Early nonspecific“flu-like” symptoms; CXR; Cleared by cell-mediated immune response DIAGNOSIS: Urine LPS immunoassay + culture (fluor Ab) TREATMENT: Antibiotics that penetrate infected cells (eryth, azith, cipro)

Question 36

what is the basic microbiology of non-TB mycobacteria?

Answer 36

obligate aerobes gram (+) rod, bacilli intracellular bacterium thick PG layer with no outer membrane high G-C genome content

Question 37

what are the 4 species of mycobacterium?

Answer 37

1. M. avium complex (MAC) 2. M. intracellulare 3. M. leprae 4. M. tuberculosis complex 5. M. marinum 6. ulcerans

Question 38

what are the subspecies of M. avium complex (MAC)?

Answer 38

1. M. avium subsp. hominissuis** 2. M. avium subcsp. avium 3. M. acium subsp. silvaticum 4. M. avium subsp. paratuberculosis

Question 39

are mycobacterium motile?

Answer 39

non-motile no flagella

Question 40

what stain do you use for mycobacterium?

Answer 40

yes they're gram (+) but you can't use the gram stain to stain them because they have a really waxy coat instead you use an acid-fast test

Question 41

what disease does M. leprae cause?

Answer 41

leprosy aka Hansen's disease

Question 42

where are M. leprae infections most common?

Answer 42

most cases (90%) in Angola, Brazil, D.R. Congo, India, Madagascar, Mozambique, Tanzania, Nepal

Question 43

how is M. leprae transmitted?

Answer 43

person-to-person transmission it's by droplets/secretions from nose and mouth natural reservoir is not known (probably humans)

Question 44

what are most causes of M. leprae caused by?

Answer 44

armadillos! in the US most cases in California, Texas, Hawaii, Louisiana

Question 45

what is the pathology of m. leprae?

Answer 45

*granulomatous disease* of skin and peripheral nerves when the macrophage can't contain the infection you get macrophages in the middle surrounded by T cells that secrete cytokines into the middle and you get a necrotic center; granulomatous disease is what causes the legions bacteria infects dermal macrophages and Schwann cells lesions are often *hypopigmented *sensory loss is common because of thickened nerves

Question 46

how do you diagnose M. leprae?

Answer 46

they cannot be grown in lab mediums!! instead they can be grown in armadillos or mouse foot pads because M. leprae like cold temperatures like found in the extremities you can also identify M. leprae by acid-fast bacilli in skin lesion biopsy or skin smear

Question 47

how can M. leprae be classified?

Answer 47

1. paucibacillary = negative smear from lesion because low bacterial numbers; strong CMI response 1-5 hypopigmented patches 2. multibacillary = positive smear from lesion because abundance of bacteria; strong humoral response; highly infectious more than 5 hypopigmented patches

Question 48

how do you treat M. leprae infections?

Answer 48

1. Paucibacillary (PB; tuberculoid) or early stages of infection: 6 months: rifampicin and dapsone 2. Multibacillary (MB; lepromatous) or severe forms of disease: 12 months: clofazimine, rifampicin, and dapsone

Question 49

where is MAC usually found?

Answer 49

M. avium complex is usually found in soil, water, plants, animals it's also uncommon to find low numbers of MAC in lungs of people without apparent disease

Question 50

how is MAC transmitted?

Answer 50

infection by ingestion (mainly water) or inhalation

Question 51

what diseases can MAC cause in immunocompetent persons?

Answer 51

1. 45-60 yr old, white men, heavy smokers, often alcoholics TB-like nodules in lungs; present with persistent cough, fatigue, weight loss 2. Lady Windermere Syndrome 3. solitary pulmonary nodule cough, fever, shortness of breath

Question 52

what is Lady windermere Syndrome?

Answer 52

a disease caused by MAC it happens in elderly women, otherwise healthy, non-smokers present with persistent dry cough, low-grade fever CXR right middle zone infiltrates due to years of cough suppression which allows bacteria to build up in the lungs and cause granulomas

Question 53

what do MAC infections in HIV/AIDS patients cause?

Answer 53

with HIV epidemic, MAC has become most common non-tuberculosis mycobacterial human disease in U.S. usually disseminated infection with bacteremia may disseminated infection with bacteremia all this usually happens when the CD4 count is below 50 can diagnose by acid-fast stain or PCR

Question 54

how do you treat MAC infection in HIV/AIDS patients?

Answer 54

clarithromycin or azithromycin sometimes add ethambutol + rifampicin

Question 55

what are the two rare mycobacerial diseases?

Answer 55

1. M. ulcerans | 2. M. marinum

Question 56

what is M. ulcerans

Answer 56

Africa “Buruli ulcer” Australia “Bairnsdale ulcer” Tropical wetlands, mud beneath stagnant water *trauma to skin followed by exposure to mud painless lump --> shallow ulcer -- > limb deformities

Question 57

what is M. marinum?

Answer 57

swimmer’s ulcer or Fishtank granuloma **trauma to skin followed by exposure to contaminated water (salt or fresh water) common in southern coastal U.S. papulonodular lesion on elbow, knee, foot, hand

Question 58

FLASHCARD: microbiology, epidemiology, clinical symptoms, diagnosis and treatment of mycobacterium leprae

Answer 58

MICROBIOLOGY: technically gram + but use acid-fast stain; cannot grow in lab EPIDEMIOLOGY: < 250,000 cases worldwide; Africa, India, Brazil; Armadillos in southern U.S.; person-to-person transmission by nasal and oral secretions CLINICAL: Skin and peripheral nerves; Hypopigmented macules --> papules --> nodules Paucibacillary (PB; tuberculoid; few bacteria; few macules) and multibacillary (MB; lepromatous; many bacteria; > 5 macules) DIAGNOSIS: Acid-fast stain of biopsy TREATMENT: PB: rifampicin and dapsone; MB: clofazimine, rifampicin and dapsone;

Question 59

FLASHCARD: MAC

Answer 59

M. avium subsp. hominissuis and M. intracellular Age, smoking, Lady Windermere Syndrome Persistent cough Diagnosed by acid fast or PCR of BAL Treat with clarithromycin or azithromycin (may add ethambutol + rifampicin)

Question 60

how do you treat M. ulcerans or M. marinum?

Answer 60

you can treat both ulcers with rifampicin and ethambutol!