WEEK 17: CELL WALL DEFICIENT ORGANISMS Flashcards
Respiratory disease
Mycoplasma pneumoniae
Mycoplasma are sometimes known as? (eaton agent)
Pleuropneumonia-like organism (PPLO)
- Do not possess cell walls
- Sometimes referred to as CWD (cell wall deficient)
- Resistant to cell wall active antibiotics
- Penicillins, cephalosporins
- Bonus is that antibiotics can help reduce normal florae
- Slow growing
- Fastidious
- Require cholesterol and fatty acids for growth
- Note these are conditions found in cultures growing eukaryotic cells
- Human sites
Mycoplasma
- Colonies grow with center imbedded below
agar surface - Thus appear as “fried eggs”
Transmission:
* Direct sexual contact, during delivery,
respiratory secretions, or fomites
* Very susceptible to heat and drying conditions
Mycoplasma
- Requires arginine
- Turns pink
- Release of ammonium (NH4) from arginine (phenol red
indicator) - Plate to agar
- A8 agar
- Look for characteristic fried egg colonies of a variety of shapes and sizes
- Diene’s or methylene blue stain
- Light blue “egg white”
- Dark blue “yolk”
M. hominis
Urogenital tract disease
Mycoplasma hominis
- 2 to 3 weeks
- Headache, low-grade fever, malaise, anorexia, sore
throat, dry cough, earaches - Extrapulmonary complications
- Cardiovascular, central nervous system (CNS), dermatologic, and gastrointestinal problems are rare.
M. pneumoniae
- Are the smallest self-replicating organisms in nature
- Very difficult to detect
- Common contaminant of cell culture
- Important in research and in virus labs utilizing cell culture
Mycoplasma
- Likely an opportunistic respiratory pathogen
- Adults with respiratory illness
- Acute immunodeficiency syndrome (AIDS)–related mycoplasma
- Synovial fluid of patients with rheumatoid arthritis
M. fermentans (incognitus)
- Generally not cultured
- Takes too long, and sensitivity is low
- Use serology
- 2 to 4 weeks apart for fourfold rise in titer
M. pneumoniae
inflammation of the fallopian tubes
Salpingitis
- Diseases
- Bronchitis
- Pharyngitis
- Walking pneumonia (primary atypical pneumonia)
- Mostly asymptomatic (over 90%)
- Isolation always considered significant
- 20% pneumonia in general populations
- School-age children and young adults
- 50% in confined settings
- Prisoners, college students, and military personnel
.
M. pneumoniae
- Initially in liquid media, and watch for pH change
- SP4, Shepard’s 10B, or 2SP broth
- Plate enriched culture, and check for characteristic
colonies
M. hominis and U. urealyticum
- Infections of the urogenital tract
- Normal florae of the lower urinary tract of women
- Still can cause upper urinary tract infections
- Significant due to infection of fetus
- Chorioamnionitis (infection of placental membrane)
- Congenital pneumonia
- Chronic lung disease in premature infants
- Meningitis of newborns with negative cultures
- 10% of cases of nongonococcal urethritis (NGU) in
men
Ureaplasma urealyticum
- Has been some association with NGU, cervicitis,
endometriosis, and PID - May lead to tubal sterility
- Very difficult to culture, takes 2 to 3 months
- Interferes with serology for other mycoplasma
M. genitalium
infection of kidney and ducts
Pyelonephritis
- Infections of the lower urogenital tract
- Found in 50% of healthy patients
- Can cause infections of the upper urinary tract in
sexually active people - Opportunistic pathogen
- May cause more severe infections in
immunocompromised
Mycoplasma hominis
infection of placental membrane
Chorioamnionitis
T-strain Mycoplasma (tiny)
U. urealyticum
- Requires urea
- Turns pink
- Release of NH4 from urea
- Plate to A8 agar plate
- Look for irregularly shaped colonies
- If using U9B, color test medium
- Add magnesium chloride (MgCl2)
- Rust brown color at membrane as MgCl2 is converted to magnesium peroxide (MgO2)
- Examine under low power on stereoscopic microscope
- T-strain Mycoplasma (tiny)
U. urealyticum
Resistant to clindamycin or lincomycin; use erythromycin
U. urealyticum
- Erythromycin
- Scattered reports of resistance
- Tetracycline
M. pneumoniae
Resistant to erythromycin; use clindamycin or lincomycin
M. hominis
