Mycoplasma
Mycoplasma
Mycoplasma: habitat, morphology, culture and biochemical characteristics
- Mycoplasma are pleuromorphic smallest living organism, also known as Pleuropneumonia like organism (PPLO).
- Belongs to family Mycoplasmataceae
Habitat:
- Mycoplasma resides in mucosa of upper respiratory tract (URT) and urogenital tract of human. They are also found in oral cavity.
- Medically important species are: Mycoplasma pneumoniae, M. hominis, M. genitalium
Morphology:
- Smallest pleuromorphic bacteria
- They lack cell wall so they are pleuromorphic and do not stain with conventional bacteriological stains.
- Cholesterol containing cell membrane
- Electron microscopy revels M. pneumoniae and other some pathogenic mycoplasma contains terminal structure which helps in attachment.
- Mycoplasma is bridge between bacteria and virus.
- They differ from virus is that they contains both DNA and RNA and can reproduce in cell free media.
Mycoplasma pneumoniae (Eaton agent)-Mycoplasmal pneumonia
- Also called Primary Atypical Pneumonia/ Walking pneumonia
- Seen in all ages
Incubation period:
- 1-3 wks
Transmission
- Airborne droplets of nasopharyngeal secretions, close contacts (families, military recruits).
C/Fs
- Gradual onset with fever, malaise, chills, headache & sore throat.
- Severe cough with blood tinged sputum (worsens at night)
- Complications: bullous myringitis & otitis, meningitis, encephalitis, hemolytic anemia
Diagnosis
- Specimens – throat swabs, respiratory secretions.
Microscopy
- Highly pleomorphic, varying from small spherical shapes to longer branching filaments.
- Gram negative, but better stained with Giemsa.
Isolation of Mycoplasma (Culture) –
- Semi solid enriched medium containing 20% horse or human serum, yeast extract & DNA. Penicillium & Thallium acetate are selective agents. (serum – source of cholesterol & other lipids)
- Incubate aerobically for 7 -12 days with 5–10% CO2 at 35-37°C. (temp range 22- 41°C, parasites 35- 37°C, saprophytes – lower temp)
- Typical “fried egg” appearance of colonies – Central opaque granular area of growth extending into the depth of the medium, surrounded by a flat, translucent peripheral zone.
- Colonies best seen with a hand lens after staining with Diene’s method.
- Produce beta hemolytic colonies, can agglutinate guinea pig erythrocytes.
Identification of isolate
- Growth Inhibition Test – inhibition of growth around discs impregnated with specific antisera.
- Immunofluorescence on colonies transferred to glass slides.
- Serum cold antibody
Serological diagnosis
- PCR
Other test
Raised ESR
Ureaplasma urealyticum
- Strains of mycoplasma isolated from the urogenital tract of human beings & animals.
- Form very tiny colonies – hence called T strain or T form of mycoplasmas.
- Hydrolyzes urea
Genital infection
- Caused by M. hominis & U. urealyticum
- Transmitted by sexual contact
- Cause of nongonococcal urethritis (NGU)
- Men – Nonspecific urethritis, proctitis, balanoposthitis & Reiter’s syndrome
- Women –PID, cervicitis, vaginitis
- Also associated with infertility, abortion, postpartum fever, chorioamnionitis & low birth weight infants
Treatment
- Tetracycline, Erythromycin & Clarithromycin – drug of choice
- Resistant to antibiotics which interfere with bacterial cell wall synthesis.
- Newer macrolides & quinolones being used now.
Exam Important
Mycoplasma: habitat, morphology, culture and biochemical characteristics
- Mycoplasma are pleuromorphic smallest living organism, also known as Pleuropneumonia like organism (PPLO).
- Medically important species are: Mycoplasma pneumoniae, M. hominis, M. genitalium
Morphology:
- Smallest pleuromorphic bacteria
- They lack cell wall so they are pleuromorphic and do not stain with conventional bacteriological stains.
- Cholesterol containing cell membrane
Mycoplasma pneumoniae (Eaton agent)-Mycoplasmal pneumonia
- Also called Primary Atypical Pneumonia/ Walking pneumonia
Diagnosis
- Specimens – throat swabs, respiratory secretions and sputum.
Microscopy
- Stained with Giemsa.
Isolation of Mycoplasma (Culture) –
- Need cholesterol for growth
- Typical “fried egg” appearance of colonies .
- Colonies best seen with a hand lens after staining with Diene’s method.
- Serum cold antibody
Serological diagnosis
- PCR
Other test
- Raised ESR
Ureaplasma urealyticum
- Hydrolyzes urea
Genital infection
- Caused by M. hominis & U. urealyticum
- Transmitted by sexual contact
- Cause of nongonococcal urethritis (NGU)
- Men – Nonspecific urethritis, proctitis, balanoposthitis & Reiter’s syndrome
- Women –PID, cervicitis, vaginitis
- Also associated with infertility, abortion, postpartum fever, chorioamnionitis & low birth weight infants
Treatment
- Tetracycline, Erythromycin & Clarithromycin – drug of choice
- Resistant to antibiotics which interfere with bacterial cell wall synthesis.
Don’t Forget to Solve all the previous Year Question asked on Mycoplasma
