Atypical Pneumonia - Chlamydia, Legionella, and Mycoplasma Flashcards
What is unique about Chlamydia’s life cycle?
It’s biphasic w/ two functionally and morphologically distinct forms
What is chlamydia’s life cycle?
Elementary body (EB) enters cells - inhibits phagolysosomal fusion and becomes a reticulate body (RB). –> RB forms daughter EBs and they are released from the cells
T or F. Chlamydia is an obligate intracellular parasite.
true - depends on host cell to provide numerous compounds
Why is chlamydia not classified as a gram negative bacteria?
b/w the EB doesn’t have a peptidoglycan and muramic acid but peptidogylcan is involved in the cell cycle at some point
What type of organism is Legionella?
gram negative rods, aerobic, nonencapsulated, facultative IC pathogens
Describe mycoplasma!
the smallest free-living organism and lacks a cell wall. nutritional requirement for a sterol is unique among prokaryotes
What is the major component of M. pneumonaie infection?
immunopathology. mycoplasma doesn’t enter nor penetrate the host cells. Instead it uses its lipoproteins to interact w/ TLRs on macrophages to produce cytokines
What are the virulence factors for chlamydia?
Proteins involved in the Type 3 secretion system: Tarp, Pkn5, CopN, inclusion membrane proteins, lipoproteins (CdsJ)
Where does Leiongella pneuophila replicate?
in alveolar macrophages after inhalation
What is an important virulence determinant of L. pneumophila?
avoidance of phagosome-lysosome fusion in phagocytic cells
How does legionella support bacterial replication?
bacterial proteins alter the vesicle traffic and a specialized vacuole forms that resembles the ER of the host.
What do the virulence factors for Mycoplasma do?
production of bacterial, polarized, adhesin complex
What diseases does Chlamydia cause?
- Psittacosis (parrot fever)
- Pneumonia
- Ocular, respiratory, and genital tract infections
Tell me about psittacosis!
caused by C. psittaci; birds = reservoir; spread by inhaling organisms in dried bird feces
What percentage does Chlamydia pneumonaie account for CAP?
6-10%
What other disease has C. pneumonaie infection been associated w/?
coronary heart disease
What does Chlamydia Trachomatis cause?
ocular, respiratory, and genital tract infections
What is the reservoir for chlamydia trachomatis?.
humans
What cells do chlamydia trachomatis infect?
squamocolumnar cells of mucous membranes
What is trachoma caused by and what it is?
immunotypes A-C and it’s an infection of the conjunctiva and the world’s leading preventable cause of blindness
What immunotypes of C. trachomatis cause genital tract infections?
D-K, some of these serotypes are associated w/ cervical squamous cell carcinoma
What is the most common sexually transmitted pathogen in industralized countries?
chlamydia trachomatis
How can neonatal pneumonia and neonatal inclusion conjuctivits be prevented?
erythromycin eye drops at birth
What is an unique problem of C. trachomatis infections?
50-70% in women are clinically silent
Who are at risk for Legionnaires’ disease?
elderly, ICP, heavy smokers, alcoholics, and other w/ compromised lungs. Males are over twice as susceptible as females
What is Pontiac fever?
milder illness caused by L. pneumophila. Attacks 95% of those exposed indiscriminately and causes flu-like symptoms
What diseases does Mycoplasma cause?
- primary atypical pneumonia - mild respiratory infections characterized by sore throat and pharyngitis
- nonspecific urethritis caused by ureaplasma urealyticum
- postpartum fever and pelvic inflammatory disease caused by M. hominis
What are the symptoms of C. pneumoniae?
most have relatively mild respiratory illness, symptoms of bronchitis or pneumonia. Scant sputum, prominent cough, history of hoarseness, headache, fever in early days, sinus percussion tenderness, rales and rhonchi
What are the symptoms of Legionnaires disease?
high fever, chills, cough, muscle aches and headaches. Symptoms usually begin 2-14 days after being exposed to bacteria
What are the symptoms of Pontiac Fever?
fever, headache, muscle aches, but no pneumonia. symptoms go away on their own
Tell me about mycoplasmal pneumonia?!
gradual and insidious onset of several days to weeks. Presents w/ fever, malaise, persistent dry cough, headache, chills, scratchy sore throat, sore chest, tracheal tenderness, pleuritic chest pain
How is chlamydiae transmitted?
attach to outer membrane of susceptible host cells and produce cytoplasmic inclusions which then release the matured inclusions to infect adjacent cells.
How are the various chlamydia strains transmitted?
Pneumoniae - human to human
Psittaci - birds to humans via respiratory route through direct contact or aerosolization
Trachomatis - transmitted to infant when it passes through infected birth canal
How do people get Legionnaire’s disease?
when they breathe in mist or vapor that has been contaminated w/ the bacteria. it is NOT transmitted from person to person
What age group is mycoplasmal pneumonia most common in?
the first 2 decades of your life, highest rate of individuals aged 5-20 years, rare in kids less than 5
What time of the year does M. pneumoniae cause as many as 50% of the pneumonias?
summer
What is the incubation period of mycoplasmal pneumonia?
3 weeks in contrast to that of influenza and other viral pneumonias which generally average a few days
Where are epidemics of mycoplasmal pneumonia seen?
every 4-8 years in the general population and tend to be more frequent w/in close populations such as military and prison populations
How is chlamydia Dxed?
IgM titer exceeding 1:16 or a 4-fold increase in IgG by MIF, PCR
How is Legionnaire’s Disease Dxed?
CXR for pneumonia, urinary antigen test, culture,
How is mycoplasma Dxed?
lab test are of limited benefit b/c they tend to be nonspecific or within the normal range.
When does one administer treatment for chlamydia?
when mixed infections with other organisms are present – in 60% of cases, treat empirically
What is the drug of choice for chlamydia?
doxy but not in kids less than 9 and pregos. Treat for 10-14 days
What other drugs can be given for chlamydia?
erthyromycin, macrolides (arithromycin and clarithroymycin)
What are the treatments for Legionella?
- respiratory tract quinolones (floxacins)
- macrolides
ones used most frequently = levofloxacin and azithromycin
When should mycoplasmal pneumonia be considered a possible etiology?
pt who presents with 3 weeks of more of a steadily progressive cough
What drugs can be used for prophylaxis in households in which pts have underlying conditions predisposed to sever mycoplasmal infection. eg SCD or antibody deficiencies
macrolide o doxycycline
