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Flashcards in Mycoplasma/Mollicutes Deck (12)
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1

Mollicutes-Mycoplasmas

"minimal cells"- highly host-dependent, don't survive well outwith host

Small genome: 600,000bp-1.4 million BP- straddle size of obligatue intracellulars

physiologically restricted- highly fastidious in terms of growth characteristic- need rich growth media

Lack cell wall (peptidoglycan): cytoplasmic membrane is exposed to envrionment, pleomorphic

Sterols present in the cell membrane (nb: sterols are a eukaryotic characteristic)

 

2

Diagnosis of mycoplasma infection

pathology- gross and histopath

isolation and ID: not as tricky as obligate intracellular pathogens, but still tough. 

serological response; Ag detection, genomic detection

Difficulties: asymptomatic carriage; similarity between pathogenic and non-pathogenic; strain heterogeneity

3

Pathogenicity of mycoplasma

"parasites" of animals, arthropods, plants, mucosal-associated

occurs in urogenital tracts, oral/nasal mucosa, NOT GIT

asymptomatic, chronic or acute infection

high inter-strain heterogeneity

pathogenic and non-pathogenic strains can be very similar

lack conventional virulence factors 

4

Mollicute genera 

mycoplasma: ~100 species, pathogens and commensals

ureaplasma: pathogens and commensals

spiroplasma: plant pathogens; insect commensal

anaeroplasma: rumen commensal

Acholeplasma: mainly commensal

[eperythrozoon and hemobartonella]: parasitic/pathogenic 

5

Virulence mechanism of mollicutes

Adhesins

Competition for metabolites and degradative enzymes- physiological destruction

Cytotoxic metabolites: means by which they damage host

endotoxicity: lipogalactan (elicit inflammatory response) and lipopeptides (similar endotoxin to what outer membranes do)

antigenic variation/capsule: escape developing IRs

Intracellular survival

Assimilation of host cell antigens

lymphocyte suppression

antigen persistence

Immunomodulation and immunopathology

6

Respiratory mycoplasma infection

e.g. mycoplasma hypopneumonia (porcine enzootic pneumonia)

Inhalation-->adherence to ciliated epithelium-->colonisation of bronchioles/alveoli--> ciliostasis and "ciliotoxicity"

Immunomodulation/immune evasion--> alveolar and peribronchial inflammation--> mononuclear cell infiltration and hyperplasia--> LN enlargement--> catarrhal (inflamm of mucous membranes) exudation--> lung consolidation

frequently chronic infection- persists months/years

secondary consequences. 

7

Secondary consequences to mycoplasma hypopneumoniae

immunocompromise

secondary infections:

pasturella multocida, actinobacillus pleuropneumoniae, hemophilus parasuis, bordetella bronchiseptica, streptococcus suis 

8

Contagious pleuropneumonia: acute/peracute respiratory mycoplasmosis

Contagious bovine pleuropneumonia-CBPP and Contagious caprine pleuropneumonia- CCPP

Notifiable diseases

acute/per-acute usually, occasionally sub-acute/chronic

high mortality, highly contagious, remission and re-activation, get chronic carriers

mononuclear cell infiltration and proliferation

neutrophil infiltration--> necrosis

fluid exudation, vascular inflammation. 

9

Hemotrophic mycoplasmas- hemoplasmas

Feline hemolytic anemia: hemobartonella felis

mycoplasma hemofelis

Porcine eperythrozoonosis: eperythrozoon suis

Mycoplasma (hemo)suis

10

General features of hemotrophic mycoplasmas

erthryocyte associated

unculturable

predisposed by intercurrent infection? i.e. feline infectious anemia predisposed by FeLV? and porcine eperytthrozoonosis predisposed by procine reproductive and respiratory syndrome virus?

Transmission: in utero? iatrogenic? arthropod? cuts, scratches, bites?

Detected in an increasing range of mammalian hosts

Emerging genus of RBC parasitic/pathogenic mycoplasma

11

Infection scheme of hemotrophic mycoplasma

mycoplasma haemx--> entry into circulation--> adhere to erthyrocytes

adherence to RBCs causes 1) indentations/rupture due to degradative enzymes or 2) autoimmunity

both 1 and 2 causes erthyrocyte lysis and consequent anemia. 

cross-species tranmission suggests zoonotic potential. 

12

Control of mycoplasmoses

test and slaughter

disease free herds/flocks

selective breeding

ABX chemotherapy: obviously don't target cell wall synthesis (i.e. beta lactones or cyclosporins). use ABX that inhibit protein synthesis (i.e. tetracycline, chloramphenicol, macrolides, aminoglycosides) or that inhibit DNA replication (fluoroquinolones).