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Mycoplasma, Chlamydia, Rickettsia


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General characteristics of Mycoplasma
Pleomorphic, NO CELL WALL
resistant to cell wall antibiotics (penicillins, cephalosporins)
unable to Gram Stain
slow grow, fastidious, aerobes or facultative anaerobes
What are L-forms?
Cell wall deficient bacteria that arise from environmental stress. They are NOT mycoplasma
Morphology of Mycoplasma
many forms: spherical, pear-shaped, filamentous
0.2 to 0.8 um in diameter
Dienes stain for observing colonies
Gliding motility on liquid covered surfaces
Cultivating Mycoplasma
Very sensitive to desiccation
culture media: beef extract, horse serum, yeast extract w/ nucleic acids.
Horse serum for cholesterol needed for sterols in membrane
1-6 hr generation time
fried egg appearance, very small
Characteristics of Mycoplasma pneumoniae
Primary atypical pneumonia
upper/lower respiratory pathogen, NOT commensal
walking pneumonia: close contact areas (college, barracks)
Dx formerly from cold agglutinins, now PCR & Serology
Characteristics of Mycoplasma hominis
Colonizes genital tract of 1/2 healthy adults
Causes upper genitourinary tract infection in females: salpingitis, pyelonephritis, PID, postpartum fever
Characteristics of Ureaplasma urealyticum
Colonize male/female gential tracts
Hard to know disease role - high carrier state in sexually active
Non-gonococcal urethritis in men and upper genitourinary tract infection in women
Assoc w/ reprod disorders, low birthweight w/ respiratory disease
found in spinal fluid in infants
Characteristics of Chlamydiaceae
resemble gnr
obligate intracellular parasites (can't make ATP)
prefer columnar epithelia lining mucous membranes
cultivated in susceptible tissue
unique replication cycle
Characteristics of Chlamydia psittaci
Psittacosis, parrot fever, ornithosis
found in wild birds
treat w/ erythromycin, tetracycline
Characteristics of Chlamydia trachomatis
3 Disease states:
1- conjunctivitis
2- Lymphogranuloma venereum
3- urethritis, PID, infertility, premature birth, cervical infection
ID'd by Serology, DFA, PCR
Characteristics of Chlamydia pneumoniae
aka TWAR / a cause of pneumonia
common among students
pharyngitis followed by flu-like lower respiratory symptoms
possible involvement in Coronary artery disease, asthma
ID: serology, HL, PCR
Characteristics of Rickettsiae
Gram NEGATIVe, obligate intracellular parasites
most can't be cultivated on ordinary media: need hen eggs, lab animals or cell culture
Arthropod vectors, xcept in Q fever
RMSF 90% of rickettsial disease in US
Characteristics of Coxiella burnetti
Q fever, recovered from urine, feces, milk of animals & ticks.
can form endospore
single organism is pathogenic
Usually manifested as pneumonia
ID: complement fixation
treated by tetracycline
Characteristics of Rickettsia
systemic disease, fever, rash, chills
ID by serology
RMSP = R. rickettsii
Murine Typhus = R. typhi

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