mycoplasma and legionella

Question 1

1. Describe the clinical syndrome of atypical pneumonia.

Answer 1

Acute infectious pulmonary disease caused by Mycoplasma pneumoniae, Rickettsia and Chlamydia, and viruses, including adenoviruses and parainfluenza virus; pulmonary infiltration, fever, malaise, myalgia, sore throat, and a cough which at first is nonproductive but becomes productive and paroxysmal. sputum gram stain/ culture often shows only mouth flora

Question 2

atypical pneumonia pathology

Answer 2

bronchopneumonia. Involved area is the respiratory mucosa lining the airways. Inflammatory response is predominantly lymphocytic

Question 3

Atypical pneumonia CXR

Answer 3

Pulmonary involvement often greater than expected from mild physical findings. Often see patchy or peribronchial infiltrates, either unilaterally or bilaterally, often with predominantly lower-lobe involvement. Lobar consolidation and pleural effusions are uncommon.

Question 4

Etiologies of atypical pneumonia

Answer 4

Mycoplasma pneumoniae, coxiella burnetii, chlamydia psittaci, chlamydia pneumoniae, adenovirus, parainfluenza virus, EBV, RSV

Question 5

Mycoplasma structure

Answer 5

DNA. Smallest free living organism. Pleomorphic (lack cell wall rigidity). Lack cell walls and do not make peptidoglycan (resistant to beta lactams). Do not trigger immune response against techoic acid, LPS or peptidoglycan. Stain poorly with gram stain. Plasma membrane contains sterols which must be obtained from growth medium. They can not synthesize aa, lipids or cholesterol.

Question 6

Mycoplasma histology/ culture

Answer 6

small, slow-growing colonies. Most species form colonies with “fried-egg” morphology. Mycoplasma pneumoniae is the exception and forms small granular colonies without “fried-egg” appearance after incubation for one week or more.

Question 7

Syndromes associated with M. pneumoniae

Answer 7

atypical pneumonia, tracheobronchitis, wheezing in infants, pharyngitis and rhinitis

Question 8

M. pneumoniae incubation period and sx

Answer 8

2-4 week incubation. Symptoms: fever, malaise, headache, cough. Pneumonia is generally mild; hospitalization is not usually required; clinical course usually leads to recovery.

Question 9

Syndromes associated with Ureaplasma

Answer 9

U. urealyticum and U. paryum. Can cause urethritis/epidididymitis, vaginosis/ PID.

Question 10

M. pneumonia transmission

Answer 10

respiratory droplets- Organism attaches to ciliated epithelial cells in the trachea and bronchi of the lower respiratory tract

Question 11

Mycoplasma mechanism of attachment to target cells

Answer 11

Becomes elongated and develops specialized tip containing Attachment factor protein P1. Cell membrane receptors on host cell (sialoglycoconjugates and sulfated glycolipids) aid in attachment.

Question 12

Additional functions of mycoplasma specialized tip structure

Answer 12

binary fission and gliding on surfaces

Question 13

Mycoplasma mechanism of host injury

Answer 13

1. CARDS toxin (community acquired respiratory distress syndrome toxin. 2. immobilization of respiratory epithelial cell cilia. 3. Production of peroxide and ROS causing tissue damage. 4. Elicits production of cytokines that both clear bacteria and contribute to dz

Question 14

describe the mycoplasma toxin

Answer 14

CARDS toxin (community acquired respiratory distress syndrome toxin): ADP ribosylating activity induces CPE and vacuolization in respiratory epithelium. Causes slowing and disorganized ciliary movement.

Question 15

Mycoplasma immune protection

Answer 15

Cell mediated immunity involved in pulm response. Immunity is incomplete. Serum antibodies appear to be related to recovery from disease but do not necessarily eliminate the organisms from the host. Therefore, post-treatment cultures are not useful to test for cure of M. pneumoniae infections.

Question 16

Who gets mycoplasma pneumoniae

Answer 16

worldwide; no seasonality; all age groups; spread by close contact; epidemic-like spread may occur in institutions or the military

Question 17

M. pneumonia diagnosis

Answer 17

1. culture of sputum- slow (2-6 weeks) so not done usually. 2. Cold hemagglutinin- Abs that react with I antigen of RBCs. Poor sensitivity and specificity. 3. Serology: complement fixation is sensitive but cumbersome. ELISA is easier and sensitive(measure IgM and IgG). 4. PCR

Question 18

M. pneumonia treatment

Answer 18

azithromycin, clarithromycin, erythromycin, doxycycline, levofloxacin, moxifloxacin (NOT cipro)

Question 19

legionella pneumophila structure

Answer 19

Motile, pleomorphic gram-negative rod (stains poorly with gram stain); non-spore forming. The bacteria are easily stained by fluorescent antibody methods or silver stains, but staining is less sensitive than culture for detecting them.

Question 20

legionella growth

Answer 20

occurs over a wide temperature range, requires cysteine and iron, and is fastidious. Optimal growth in the laboratory occurs on buffered charcoal-yeast extract (BCYE) medium at 35C, and growth is slow (2-6 days to form colonies).

Question 21

legionella enzymes

Answer 21

oxidase and catalase positive. Produces B-lactamase so resistant to penicillins. Produces hemolysin and cytotoxin

Question 22

Legionella pneumophila clinical features

Answer 22

1. Pontiac Fever – acute, self-limited febrile illness (no pneumonia). 2. Legionnaires’ disease – mild
   to severe. The incubation period is long. pneumonia with fever, malaise, chills, cough (90% of cases), chest pain, headache, diarrhea (30-50% of cases). Extra-pulmonary symptoms are more common that for many other bacterial pneumonias.

Question 23

legionella transmission

Answer 23

inhalation, aspiration of water from aquatic ecosystems or water systems contaminated. Not transmitted person to person

Question 24

Legionella pneumophila pathogenesis

Answer 24

Evades host defenses by living within macrophages (a facultative intracellular pathogen). Inhibits endosome-lysosome fusion. Endosomes become associated with endoplasmic reticulum to form “ribosome-studded” phagosomes

Question 25

Legionella risk factors

Answer 25

immunosuppression, chronic cardiopulmonary disease, chronic lung disease, smoking, advanced age.

Question 26

Legionella diagnosis

Answer 26

1. culture- specific growth requirements. 2. Silver staining- visualize intracellular legionella. Nonspecific. 3. immunofluorescence: less sensitive than culture, but more specific than silver staining. 4. serology: indirect fluorescent antibody titer. 5. Molecular: urine immunoassays. PCR

Question 27

Legionella treatment

Answer 27

macrolides (azithromycin, clarithromycin), quinolones (levofloxacin, ciprofloxacin, moxifloxacin), ketolide, tetracyclines, TMP-SMX, rifampin