Pathogenesis of Mycoplasmosis

1. Presented By:
Sangram P. Ramane
PhD Scholar
Roll no. 1447
DIVISION OF BACTERIOLOGY AND MYCOLOGY, IVRI
Assignment
On
Mechanism of Bacterial Infections

2. CONTENTS
I. Introduction
II. Sources of the Mycoplasma
III. Adherence to Host Tissues
IV. Invasion/Fusion Host Cells
V. Possible Mechanisms of Damage to Host Cells
VI. Modulating the Immune System
VII. Evasion of the Immune System
VIII. Mycoplasmal Disease
IX. Conclusions

3. INTRODUCTION
 Mycoplasmas - unique, cell-wall-less prokaryotes.
 Smallest free-living organisms (down to 300 nm diameter) and have
smallest genomes (down to 580 kb).
 Pleomorphic, difficult to identify even under electron microscope.
 Hard to culture in laboratory hence often missed as pathogenic
causes of diseases for this reason.
 Widely distributed as parasites of mammals, birds, reptiles, fish,
arthropods, and plants and may be found in clinical specimens.

4.  In 1898 , at the Pasteur Institute first strain isolated from cattle
with arthritis and pleuropneumonia.
 First human strain was isolated in 1932 from an abscessed wound.
 Primarily residing in the respiratory tract and lungs.
 Remains an important cause of pneumonia and other airway
disorders, such as tracheobronchitis, pharyngitis and asthma.
 Can ride to other parts of the body, with non-pulmonary
manifestations, such as blood, skin, joint, central nervous system,
liver, pancreas, and cardiovascular syndromes and disorders.
Introduction contd…

5. SOURCES OF THE MYCOPLASMA
 Relatively host specific.
 Infection may occur in more than one host, they tend to persist in a
primary host, to which disease is often confined.
 Infected animals are the principal sources.
 A prolonged carrier state with the organism persisting on a mucosal
surface.
 Transmitted in respiratory aerosols, in milk, and in reproductive tract
secretions of infected animals and may be egg transmitted in birds.
 Lateral transmission favoured by close animal contact.

6. ADHERENCE TO HOST TISSUES
Major virulence factor, and adherence deficient mutants are avirulent.
 Adhesins:
Tip organelle: In M. pneumoniae and M. gallisepticum: A polar,
tapered cell extension at one of the poles containing an electron-dense
core in the cytoplasm.
As an attachment organelle, HA, hemadsorption and as the leading
end in gliding-type motility.
169-kDa surfface protein (P1) and 30-kDa protein (P30) in M.
pneumoniae.
GapA and Mgc2 in M. gallipesticum
P1 is adhesin and P30 is a protein associated with the adherence
process.

7.  Accessory Proteins:
Two groups: 40-kD & 90-kDa proteins (P40 and P90)
HMW1-HMW3.
Not adhesins, but the loss of one of them is associated with the
inability to cytadhere.
Responsible not only for the lateral movement and proper orientation
of P1.
 VlhA Hemagglutinin
M. gallisepticum 70 kDa lipoprotein
M. synoviae, the vlhA gene product is post-translationally cleaved into
two proteins approximately equivalent in size, an amino terminal
lipoprotein and a carboxyl terminal hemagglutinin
Adherence to host tissues contd…

8. M. gallisepticum and
M. pneumoniae
attached by the
terminal tip organelle
Adherence to host tissues contd…

9.  Ciliary Adhesin of M. hyopneumoniae
97 kDa peripheral membrane protein binds specifically to three
distinct sulphated glycolipids on the host-cell membrane of porcine
tracheal cilia.
 Lipoprotein adhesin of M. conjunctivae
LppS, sequence similarity to ciliary adhesin of M. hyopneumoniae.
 Cytadhesin of M. agalactiae
P40 cytadhesin of M. agalactiae is a lipoprotein mediates adherence to
lamb synovial cells.
 Other Putative Adhesins
Vsp lipoproteins of M. bovis
PvpA of M. gallisepticum
Proteins of 64 and 41 kDa in M. hyopneumoniae
Adherence to host tissues contd…

10. INVASION INTO HOST CELLS
Current theory - Mycoplasmas remain attached to surface of epithelium,
although some mycoplasmas enter non phagocytic host cells.
 Invasins
Fibronectin binding protein - A 65-kDa protein, bind fibronectin or
sulfated polysaccharides.
Form a molecular bridge between the bacteria and host cell surface
proteins that enables invasion.
Urokinase - Activation of plasminogen to plasmin, a protease, may
alter cell surface proteins and thereby promotes its internalization.

11.  Changes in the Host Cell Cytoskeleton
Mycoplasma contact with host cell surface trigger cytoskeletal
rearrangements that facilitate internalization E.g. M. penetrans, M.
gallisepticum.
 Signal Transduction
Tyrosine phosphorylation of a 145-kDa host cell protein which
activates PLC to generate second messengers (PIP and DAG) leading to
changes in host cell lipid turnover which result in invasion.
 Survival and Multiplication Within Host Cells
Most ultrastructural studies performed with engulfed mycoplasmas
revealed mycoplasmas within membrane bound vesicles. E.g. M.
penetrans, M. gallisepticum.
Invasion of host cells contd…

12. FUSION WITH HOST CELLS
 Factors Mediating Fusion
Fusogenicity depend on unesterified cholesterol content of the cell.
Fusion found only in Mycoplasma sp.
Acholeplasma sp. which do not require cholesterol, are nonfusogenic.
Stimulated by Calcium and depends on the proton gradient.
 Molecules Implicated in Fusion
Polar lipid fraction capable of enhancing the fusion.
Choline-containing phosphoglycolipids: MfGL-II and MfGL-I.
Very little is known about the role of membrane proteins in the fusion
process.

13. POSSIBLE MECHANISMS OF DAMAGE
 Competition for Precursors
Limited biosynthetic capabilities of these microorganisms.
Depend on host to supply precursors required for biosynthesis of
macromolecules.
Competition for these biosynthetic precursors disrupt host cell integrity and
alter host cell function.
e.g. Non fermenting Mycoplasma - Arginine dihydrolase pathway - ATP -
deplete the host's arginine reserves affecting protein synthesis, host cell
division, and growth.
Some utilises choline - Directly affects neurotransmission, transmembrane
signalling and lipid metabolism.

14.  Damage Induced by Adherence
Interference with membrane receptors alter transport mechanisms.
Disruption of K+ channel of ciliated bronchial epithelial cells lead to
ciliostasis.
Hydrolysis of host cell phospholipids catalyzed by the potent membrane-
bound phospholipases present in many mycoplasma species.
 Damage Induced by Fusion
Mycoplasma components are delivered into the host cell and affect the
normal functions of the cell.
e.g. Mycoplasmal nucleases that may degrade host cell DNA.
Phosphoprotein phosphatase may interfere with the normal signal
transduction cascade of the host cell.
Possible mechanisms of damage contd…

15.  Polysaccharide Capsules
Galactan: M. mycoides ss mycoides LC/SC
Glucan: M. mycoides ss capri
Lipoglycan: Ureaplasma sp., M. hominis
Lipoglucan : M. neurolyticum
Does not appear to influence phagocytosis.
Found to have toxic effects when injected intravenously.
 Hydrogen Peroxide and superoxide derivatives
Only products of mycoplasmas established to cause direct cell damage.
Generated as a product of flavin-terminated ETC.
Responsible for hemolytic activity and ciliostatic effect.
Possible mechanisms of damage contd…

16. MODULATION OF IMMUNE SYSTEM
• Lipoproteins
Extremely abundant, capable of stimulating the release of IL-1β, IL-6, and
TNF-α.
A macrophage-activating lipopeptide with a molecular mass of 2 kDa
(MALP-2) identified in M. fermentans,
Two lipopeptides, derived from the variable lipoproteins VlpA and VlpC
characterized in M. hyorhinis.
• Membrane Lipids
Choline-containing phosphoglycolipid (MfGL-II) found to be associated
with the secretion of inflammatory mediators.
MfGL-II causes activation of protein kinase C, secretion of nitric oxide and
prostagalandine E2.

17.  Mitogenic Activity
Mitogens appear to include glycolipid and major membrane lipoprotein.
May be indirect due to cytokine release by macrophages and monocytes.
 Superantigens
M. arthritidis (MAM), released by senescent cells.
No other mycoplasmas have superantigens.
 Oncogenic Activity
Prolonged interactions with mycoplasma induce chromosomal instability.
May be over-expression of H-ras and c-myc oncogenes.
Mycoplasma-mediated transformation of cells has a long latency.
Modulation of immune system contd…

18. EVASION OF IMMUNE SYSTEM
 Antigenic Variation
Phase and size variation of cell-surface proteins
VlhA in M. gallisepticum, VlhA in M. synoviae,
Vlp in M. hyorhinis, Vsp in M. bovis, Vsa in M. pulmonis
 Mycoplasmal Shield
Long Vsa protein, blocks access of the outer membrane of mycoplasmal
cells to complement while short Vsa protein lead to ready access.
• Mycoplasmas Form Encapsulating Biofilms
An extracellular matrix containing protein, lipid, and polysaccharide.
Protect mycoplasmas against various agents, help to evade host immunity.

19. Mycoplasmal Shield
Evasion of immune system contd…

20. MYCOPLASMAL DISEASE

21. Mycoplasma Diseases of Animals Characterized by Invasive Blood borne
Infection
Primary Disease Host Species Other Manifestations
Septicemia Goats, Sheep
M. mycoides subsp. capri
Polyarthritis,
Pneumonia, Mastitis,
conjunctivitis
M. capricolum subsp.
Capricolum
Arthritis, Mastitis,
Pneumonia
Polyserositis /
Arthritis
Swine M. hyorhinis Pneumonia
Alligator M. alligatoris Pneumonia

22. Mycoplasma Diseases of Animals Characterized by Invasive Blood borne
Infection
Primary Disease Host Species Other Manifestations
Tenosynovitis /
Arthritis
Chickens, Turkeys M. synoviae Air Sacculitis
Arthritis /
Polyarthritis
Cattle M. bovis, M. alkalescens Mastitis, Pneumonia
Sheep, Goats M. agalactiae
Mastitis,
Conjunctivitis,
Pneumonia
Swine M. hyosynoviae Pneumonia
Rats M. arthritidis Pneumonia
Crocodiles M. crocodyli Pneumonia

23. Mycoplasma Diseases of Animals Characterized by Localized Extension of
Infection
Primary Disease Host Species Other
Pneumonia
Cattle M. dispar
Mastitis,
Arthritis
M. bovis -
Sheep M. ovipneumoniae -
Swine M. hyopneumoniae -
Dogs M. cynos -
Mice, Rats M. pulmonis -
Pleuropneumonia
Cattle M. mycoides subsp. mycoides SC
Arthritis In
Calves
Goats
M. capricolum subsp.
capripneumoniae
-

24. Mycoplasma Diseases of Animals Characterized by Localized Extension of
Infection
Primary Disease Host Species Other
Air Sacculitis
Chicken / Turkey M. gallisepticum
Tracheitis, Sinusitis,
Conjunctivitis
M. synoviae Sinusitis (Turkey)
Turkey M. Meleagridis Osteodystrophy
Conjunctivitis
Cattle M. Bovoculi -
Sheep, Goats M. Conjunctivae -
Cats M. felis -
Songbirds M. gallisepticum -
Mice M. neurolyticum Rolling Disease
Tortoises M. agassizii Rhinitis

25. Primary Disease Host Species Other Manifestations
Mastitis
Cattle
M. bovis
Pneumonia, Arthritis,
Vulvovaginitis
M. bovigenitalium Vulvovaginitis
M. californicum -
M. canadense -
M. alkalescens Arthritis
Sheep, Goats
M. agalactiae
Arthritis, Septicemia,
Keratoconjunctivitis,
Vulvovaginitis
M. capricolum subsp.
capricolum
-
M. mycoides subsp. capri -
Goats M. putrefaciens -
Mycoplasma Diseases of Animals Characterized by Localized Extension of
Infection

26. Primary Disease Host Species Other Manifestations
Vulvovaginitis Cattle Ureaplasma diversum
Infertility, Abortion,
Pneumonia
Seminal Vesiculitis Cattle M. bovigenitalium Decreased Sperm Motility
Pleuritis Horses M. felis -
Erythrodermatitis Freshwater Fish M. mobile Necrotizing Gill Lesions
Mycoplasma Diseases of Animals Characterized by Localized Extension of
Infection

27. CONCLUSION
 These microorganisms have evolved molecular mechanisms needed to deal
with the host immune response and the transfer and colonization in a new
host.
 These mechanisms include mimicry of host antigens, survival within cells, and
generation of phenotypic plasticity.
 The major question is whether mycoplasmas cause damage to the host cells
and to what extent the damage is clinically apparent.
 Mycoplasmas have long resisted detailed analyses because of complex
nutritional requirements, poor growth yields, and a paucity of useful genetic
tools.
 Although questions still far outnumber answers, significant progress has been
made in identifying the mechanisms by which mycoplasmas interact and
damage eukaryotic host cells.

28. Thank You…