上海交通大学：《医学微生物》课程教学资源（PPT课件讲稿）英文版 Mycoplasmas

Mycoplasmas

Mycoplasmas

Mycoplasmas e A group of the smallest organisms that can be free living in nature Pass bacterial filter and also grow on laboratory media. More than 80 species, belong to Mycoplasmatales of mollicute. 3 families can be divided: Mycoplasmataceae(require external cholesterol during growth, contain Mycoplasma and ureplasma two genera); Acholeplasmataceae(need not external cholesterol during growth); Spiroplasmataceae (can form spiral structure)

Mycoplasmas A group of the smallest organisms that can be free￾living in nature, Pass bacterial filter and also grow on laboratory media. More than 80 species, belong to Mycoplasmatales of Mollicute. 3 families can be divided: Mycoplasmataceae (require external cholesterol during growth, contain Mycoplasma and Ureplasma two genera); Acholeplasmataceae (need not external cholesterol during growth); Spiroplasmataceae (can form spiral structure)

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Morphology Morphology e The smallest among prokaryotic microganisms with circular dsDNA, usually 0.2-0.3um in size lack of cell wall e Pleomorphic, spherical, short rod, filament; Gram /negative, but stained hardly, usually use Giemsa stain They can assume multiple shapes including round, fried eggcolonial pear shaped and even filamentous morphology

BOLOGALFEATURES Motility: Motile by possible release and reattachment of terminal cell organelle, no flagella present; possess a protein attachment factor termed p 1 that interacts with a specific cellular receptor and allows adherence to respiratory epithelium Respiration-Fermentation Aerobes anaerobes

BIOLOGICAL FEATURES ▪ Motility: Motile by possible release and reattachment of terminal cell organelle; no flagella present; possess a protein attachment factor termed P1 that interacts with a specific cellular receptor and allows adherence to respiratory epithelium. ▪ Respiration-Fermentation: Aerobes￾anaerobes

Culture e Most aerobic, require 10%-20% human or animal serum added to basic nutrient media except Acholeplasma; typical colony show fried egg apperance. e Many species are part of the normal flora e these organisms are a frequent cell culture contaminant The organisms have limited biosynthetic abilities they require cholesterol for their cell membrane and can generate energy via the breakdown of arginine a Ureaplasma requires urea to produce an electrochemical gradient; urea is converted to ammonia to produce AtP

Culture Most aerobic; require 10%-20% human or animal serum added to basic nutrient media except Acholeplasma; typical colony show fried egg apperance. Many species are part of the normal flora These organisms are a frequent cell culture contaminant ▪ The organisms have limited biosynthetic abilities; they require cholesterol for their cell membrane and can generate energy via the breakdown of arginine ▪ Ureaplasma requires urea to produce an electrochemical gradient; urea is converted to ammonia to produce ATP

GENETICS e These bacteria have the smallest genome of any prokaryote( about 20% that of E coi) and the lowest C content (about 24%)

GENETICS These bacteria have the smallest genome of any prokaryote ( about 20% that of E. coli) and the lowest G C content (about 24%)

Resistance e sensitive to osmotic presssure e resistant to thallium acetate醋酸亚铊 in a concentration of 1 1 0000 which can inhibit bacteria

Resistance Sensitive to osmotic presssure resistant to thallium acetate醋酸亚铊 in a concentration of 1:10000 which can inhibit bacteria

fransmission .M. pneumoniae is spread by close contact via aerosolized droplets and thus is most easily spread in confined populations (e.g, families, schools, army barracks)

Transmission M. pneumoniae is spread by close contact via aerosolized droplets and thus is most easily spread in confined populations (e.g., families, schools, army barracks)

PATHOGENESS Adherence factors- The P1 adhesin localizes at tips of the bacterial cells and binds to sialic acid residues on host epithelial cells. The nature of the adhesins in the other species has not been established. Colonization of the respiratory tract by M. pneumoniae results in the cessation of ciliary movement a Toxic Metabolic Products Immunopathogenesis most children are infected from 2 5 years of age but disease is most common in children 5-15 years of age

PATHOGENESIS ▪ Adherence factors - The P1 Adhesin localizes at tips of the bacterial cells and binds to sialic acid residues on host epithelial cells.The nature of the adhesins in the other species has not been established. Colonization of the respiratory tract by M. pneumoniae results in the cessation of ciliary movement. ▪ Toxic Metabolic Products ▪ Immunopathogenesis : most children are infected from 2 - 5 years of age but disease is most common in children 5-15 years of age