Chapter 38: Mycoplasma Flashcards
Describe mycoplasma
Smallest free-living prokaryotic microorganism
Membranes of mycoplasma
Possess triple-layered limiting membranes but lack cell walls
Gram method staining
It does not stain in Gram method staining
Shape
Highly pleomorphic, filterable, plastic forms
Environment susceptibility
-susceptible to dessication and disinfectants
Microcolonies
-fried egg appearance
Host
Most are host-specific
Replication
Do not replicate in the environment
Environment
-most are facultative anaerobes
Contain species of vet importance
-Mycoplasma
-Ureaplasma
Cause a wide range of diseases in animals, including contagious bovine pleuropneumonia
-Mycoplasma species
Microorganisms in the class
Mollicutes
Smallest prokaryotic cells capable of self replication
Mycoplasma
Shape
Pleomorphic ranging from sperical to filamentous
Size:
-spherical
-filamentous
-0.3 to 0.9 um in diameter
-up to 1.0 um long
Cannot synthesize
Peptidoglycan or it’s precursor
Cannot synthesize peptidoglycan or its precursor thus
-they do not possess rigid cell walls but have flexible, triple-layered outer membranes
-their flexibility allows them to pass through bacterial membrane of pore
their flexibility allows them to pass through bacterial membrane of pore sizes from
0.22 um to 0.45 um
Are susceptible to:
-dessication
-heat
-detergents
-disinfectants
Resistant to antibiotics:
-penicillin
Interfere with the synthesis of bacterial cell walls
Penicillin
Phylogenetically mycoplasmas are linked to Gram-positive such as _____ based on 5S RNA sequences analyses
Clostridium
Have a low guanine cytosine content in their DNA
Requirement
Enriched media for growth
Colonies when illuminated obliquely
Umbonate microcolonies
Microcolonies appearance in transmitted light
‘Fried egg’
Due to extension of microcolony into agar
Dense central zone
-First mycoplasma identified in 1890
-Cause contagious bovine pleuropneumonia
-Mycoplasma mycoides subsp. mycoides
Similar types of mycoplasmas subsequently identified were called
-Pleuropneumonia-like organisms (PPLO)
Grow optimally in an atmosphere og
5 to 20% CO2
Non-pathogenic anaerobic mycoplasmas found in
Rumens of sheep and cattle
Associated with reproductive disorders
-Mycoplasma and Ureaplasma
Known as ______ or ______ (trivial name) as they parasitize rbc
-Haemotropic mycoplasmas
-haemoplasmas
Found in:
-conjunctiva
-nasal cavity
-oropharynx
-intestinal and genital tracts of humans and animals
-found in rbc
-host specific (some)
-cross the species barrier more often
-signifucant in immunocompromised or stressed animals
-Haemotropic mycoplasma
Survival in environment
Short periods
Differentiated by their
-host specificity
-colonial morphology
-requirement for cholesterol
-biochemical reactivity
Mycoplasma spp. and Ureaplasma spp.
Requirement for enriched media:
-animal protein
-sterol component
-source of DNA or adenine dinucleotide
Commercially available mycoplasma agar or broth media (often heart infusions):
-supplemented with 20% horse serum
-yeast extract providing amino acids and vitamins
Used to inhibit Gram-positive bacteria
Penicillin
Incorporated to inhibit Gram-negative bacteria and fungi
-Thallous acetate
Media buffered at:
-Mycoplasma- pH 7.3 to 7.8
-Ureaplasma -pH 6.0 to 6.5
Culturing of ureoplasmas
Urea is added to the medium and thallous acetate, which is toxic for these organisms, is omitted (?)
Occasionally grow as contaminants on mycoplasma media
Acholeplasma spp
Size of unstained microcolonies of Mycoplasma species are
-0.1 to 0.6 mm in diameter
-have a fried egg appearance
-some 1.5 mm and can be seen w/o magnification
Ureaplasma
-size
-lacks
-referred
-stain
-0.02 to 0.06 mm
-lack peripheral zone
-T-mycoplasma (bc tiny colonies)
-Dienies stain
-central zone- dark blue
- peripheral zone- lighter blue
Mycoplasma requires differentiation from colonies of…
Bacterial L-forms
Bacterial L-forms
-lack rigid cell walls
-assume shapes resembling mycoplasmas
-can revert to their normal bacterial shape…
-Require sterols for growth
-reflected in their sensitivity to inhibition by digitonin
Mycoplasma and Ureaplasma
-Sterol-independent
-resistant to inhibition by digitonin
-Acholeplasma species
Digitonin sensitivity test
Exceeding 5 mm means it is sensitive to digitonin
Do not metabolize urea
Mycoplasma
Produces urease
-Ureaplasma
Growth inhibition tests
-8 mm zone of growth inhibition develops, containing homologous antiserum
T1 vaccine strains for contagious bovine pleuropneumonia
Do not produce specific toxins or invasins
Important in its ability to produce disease
-Intrinsic metabolic functions
Essential attribute for pathogenicity but mycoplasma do not invade the cells
Ability to adhere to host cells
Evade immune response
European strains (subsp. mycoides) less H202 than
African strains of this spp
Induce toxic damage to host cell to which the organism are adhering
Production of H202
Promote attachment to mammalian cells
Possess structures composed of unique adhesion proteins
Can adhere to ___ and ___ and can also impair ___
-neutrophils and macrophages
-phagocytic functions
-Important virulence attributes
- allows the organism to rapidly adapt to the host environment and to evade the developing immune response
Variation in surface proteins
Alterations in surface proteins demonstrated In many important animal pathogens including:
-Mycoplasma mycoides subsp. mycoides
-M. bovis
-M. gallisepticum and M. synovial (avian pathogens)
Leads to release of pro inflammatory cytokines including tumor necrosis factor and interleukins
Activation of macrophages and monocytes
Pathogenic mycoplasmas including those involved in pulmonary diseases
Are mitogenic for B and T lymphocytes
Effect of digitonin:
-growth inhibition
-growth inhibition
-no growth inhibition
-Mycoplasma species
-Ureaplasma species
-Acholeplasma species
Requirement for cholesterol:
-Mycoplasma species
-Ureaplasma species
-Acholeplasma species
- (+)
- (+)
- (-)
Urease production:
-Mycoplasma species
-Ureaplasma species
-Acholeplasma species
- (-)
- (+)
- (-)
Colony size:
-Mycoplasma species
-Ureaplasma species
-Acholeplasma species
- 0.1-0.6 mm
- 0.02-0.06 mm
- up to 1.5 mm
Positive for glucose fermentation
-M. capricolum subsp. capricolum
-M. mycoides subsp. capri
Positive for arginine hydrolysis
-M. capricolum subsp. capricolum
Positive for phosphatase activity
-M. capricolum subsp. capricolum
-Mycoplasma agalactiae
Positive for casein digestion
-M. capricolum subsp. capricolum
-M. mycoides subsp. capri
Table 38.1 and table 38.2
