"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
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
Virulence mechanism of mollicutes
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
Assimilation of host cell antigens
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 to mycoplasma hypopneumoniae
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
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
Porcine eperythrozoonosis: eperythrozoon suis
General features of hemotrophic mycoplasmas
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
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).