Mycoplasma/Mollicutes Flashcards
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)
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
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
Mollicute genera
mycoplasma: ~100 species, pathogens and commensals
ureaplasma: pathogens and commensals
spiroplasma: plant pathogens; insect commensal
anaeroplasma: rumen commensal
Acholeplasma: mainly commensal
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
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.
Secondary consequences to mycoplasma hypopneumoniae
immunocompromise
secondary infections:
pasturella multocida, actinobacillus pleuropneumoniae, hemophilus parasuis, bordetella bronchiseptica, streptococcus suis
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.
Hemotrophic mycoplasmas- hemoplasmas
Feline hemolytic anemia: hemobartonella felis
mycoplasma hemofelis
Porcine eperythrozoonosis: eperythrozoon suis
Mycoplasma (hemo)suis
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
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.
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).
