Mycoplasma

• Mycoplasma has many different shapes because the microbe is absent of cell wall.

Morphology and Staining

Shapes of Mycoplasma by scanning electron microscopy

Blue color by Giemsa stain

• Mycoplasma is the smallest (0.2-0.3 µm) microbe that can grow on artificial cell-free-media and form very small colony on plate.

• Mycoplasma grow slowly in blood or serum contained media and produce "fried egg" colonies on agar plates.

• Due to the slow growth, the colonies need 3 weeks to develop. The colonies are extremely small.

Culture

Human pathogens

• There are many species in Mycoplasma in nature. Two genera are recognized as human pathogens: – Mycoplasma – Ureaplasma

• Mycoplasma pneumoniae • Ureaplasma urealyticum

Mycoplasma pneumoniae

• cause primarily atypical pneumonia in human

Virulent factors

• P1 protein– an adhering membrane protein

• Glycolipid antigen– Induce immunopathological injury

• Capsule– resists phagocytosis and display cytotoxicity

Ureaplasma urealyticum

• Causes non-gonococcal urethritis (NGU). NGU is a common STD with or without clinical symptoms.

Virulent factors

• Phospholipase

• Urease

• IgA protease

◇ Laboratory diagnosis: Sample: Sputum or throat washings. Microscopy: Direct observation. Serological examination: Cold agglutinin test (IgM auto-antibody in sera of patients) and ELISA (P1 protein as the antigen).

◇ Treatment: Since Mycoplasma lacks cell wall, the penicillins and cephalosporins are ineffective. The common used antibiotics are tetracycline and erythromycin.◇ Prevention: No vaccines are currently available