Chlamydia and Mycoplasma

Chlamydophila

  • C. pneumoniae, C. pecorum, C. psittaci, C. abortus, C. felis, C. caviae 
  • intracellular Gram-ve 
  • obligate intracellular parasites - incapable of obtaining ATP by metabolic activities 
  • complex life cyle - distinct infectious forms (EB) and reproductive forms [intermediate forms (IF) and reticular bodies (RB)]
  • EB - outer membrane with LPS, haemaglutinin and major outer membrane protein (MOMP) 
    • rigid cell wall
    • RNA:DNA content 1:1
    • isolated organisms infectious 
    • adapted for extracellular survival 
  • RB - opposites to above, RNA:DNA content 3:1
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Pathogenesis Chlamydophila

  • life cycle takes place in the endosome 
  • many mechanisms for avoiding immune recognition 
    • inhibition phagolysosomal fusion
    • down-regulation of class II antigens 
    • inhibition of apoptosis 
    • proteolytic cleavage of NF-xB
  • DNA, RNA and protein synthesis eventually ceases in the infected cells
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Infections Chlamydophila

  • ocular 
    • acute or chronic
    • catarrhal conjunctivitis, keratitis and superficial corneal ulceration can occur 
  • abortion in ruminants 
    • 20-50% of sheep abortions in UK due to Cp. abortus Economic costs to the farming industry
    • placentitis with cotyledonary necrosis and intercotyledonary oedema 
  • pulmonary/respiratory chlamydiosis 
    • exudative and/or purulent bronchiolitis with tracheitis 
    • pneumonia with areas of consolidation 
  • male genital tract
  • arthritis
  • intestinal infections 
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Chlamydia abortus

  • endemic among ruminants - efficiently colonsie the placenta 
  • around day 90 of gestation, coincident with a phase of rapid fetal growth Chlamydophila produces a progressively diffuse inflammatory response - thrombotic vasculitis and tissue necrosis 
  • abortion, stillbirth, delivery of weak - fullterm neonates, apparently normal lambs may also be affected 
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Chlamydophila felis

  • part of feline upper respiratory tract infection (URI) complex 
    • affects nose and eyes and manifests similar symptoms
    • accounts for 10-15% of all feline URI cases and often occurs with another URI 
  • mainly causes conjunctivitis in young kittens (5-12 weeks)
  • may also lead to flu-like symptoms 
    • anorexia
    • coughing/difficulty breathing
    • fever
    • pneumonia 
    • runny nose
    • sneezing
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Avian chlamydiosis (psittacosis, ornitosis)

  • pneumonia
  • firbrino-necrotising serosis of body cavities and organ surfaces, hepato-splenomegaly with dilation of sinusoids and infiltration of mononuclear cells and lymphocytes can be observed 
  • greenish yellow gelatinous faeces
  • reduced egg production 
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Psittacosis

  • transmission and infection - respiratory and oral 
  • symptoms 
    • variable depending on strain, age and immune status of bird and presence of concurrent infections 
    • usually related to respiratory and digestive system 
  • treatment and measures 
    • depends on species, age, immune status, length of illness, virulence of infecting strain - sooner treatment is sought the better the outlook
    • isolate all sick, incoming new birds (30-45 days) 
    • test symptomatic birds, treat infected birds (doxycycline 45 days)
    • clean and disinfect cages , keep feather dust circulation to a minimum, droppings from infected bird soaked with disinfectant before disposal 
    • contact with humans and infected birds kept to absolute minimum, monitor any flu-like symptoms in human caretakers 
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Laboratory Diagnosis Chlamydophila

  • specimens 
    • abortion - cotyledons, vaginal swabs, aborted fetus, and culture 
    • arthritis - synovial fluid 
    • conjunctivitis - conjunctival swab
    • systemic infections - lung, liver, spleen, pericardium 
  • diagnostic methods
    • staining methods
    • culture - suitable transport medium, keep at 4C, cell culture - 2-3 days in absence of antibiotics that kill Chlamydia, followed by staining or IF - can be decontaminated using gentamicin, vancomycin, and nystatin
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Chlamydia - Treatment and Vaccine

  • tetracycline (doxycycline) is drug of choice 
  • birds - can be incorporated into feed as impregnated seeds eg
  • vaccine can reduce disease but often has limited efficacy in preventing infection 
  • Ruminant vaccines - inactivated whole cell, addition of adjuvants OR live attenuated vaccine C. abortus Enzovax, CEVAC
  • Avian chlamydiosis - "no effective vaccine for avian chlamydiosis"
  • Feline chlamydiosis - inactivated vaccines 
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Mycoplasmatales

  • Most important genera - Mycoplasma, Ureaplasma 
  • common to refer to all Mollicutes as mycoplasmas despite only one genus being Mycoplasma
  • first recognised mycoplasmal disease was a veterinary disease - contagious bovine pleuopneumonia - Germany 1863
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Mollicutes - what are they?

  • smallest free-living cells known
  • morphology and size are variable 
    • spherical forms 300-800nm in diameter
    • filamentus forms 100-300 nm x 3-150 um 
  • genome is 1/3 of size of bacterial
  • membrane lacks peptidoglycan and is very flexible 
  • Gram -ve 
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Mycoplasmas - reproduction and metabolism

  • divide by binary fission 
  • genome replication  > multinucleated filaments > chains of coccoid cells > fragmentation into individual cells 
  • mycoplasmas divide slowly - 1-6 hours 
  • optimal growth temp 37C
  • glucose used as main source of energy 
  • facultative anaerobes
  • arginine can be used as alternative source of energy 
  • require lipids and sterols for membrane synthesis 
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Mycoplasmas - pathogenesis

  • Attachment - mainly by anionic surface layer, some species have specialised surface structures, host cell receptors are glycoproteins, some inhibit ciliary movement or destroy cilia - helps attachment and predisposes to bacterial super-infections 
  • Toxins - haemolysin, proteases, nucleases, neurotoxin (M. neurolyticum)
  • Complement activation -  can be detrimental to bystander cells and causes inflammation via release of chemotactic fragments 
  • Cytokine activation - TNF, IL-6, IL-1, M.arthriditis has T-cell super antigen induced cytokine production and inflammation 
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Mycoplasma - evasion of the immune response

  • Decrease phagocytosis - in neutrophils and macrophages 
  • Decrease respiratory burst - persistance in phagocytes 
  • polyclonal activation of B-cells
  • Antigentic variability 
  • Molecular mimicry

Latent infections are common - as consequence of numerous mechanisms for evading immune responses 

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Pathology of mycoplasma

  • Acute 
    • inflammation
    • neutrophil infiltration 
    • fibrin accumulation 
    • generalised fibrinopurulent exudate on serosal membranes and synovial membranes 
    • septicaemic forms with coagulopathy, vascular thrombosis, shock mediated by cytokines 
  • Persistent Localised 
    • tissue destruction
    • pockets of encapsulated pus (mastitis) usually evolving to fibrosis
    • proliferative synovitis and erosive arthritis 
    • pleural thickening 

Main forms of disease are: respiratory, articular and mastitis 

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Farm Animals - mycoplasmas

  • respiratory disease, mastitis, arthritis, genital disease, eye lesions 
  • most important - contagious bovine pleuropneumonia (CBPP), contagious agalactia (CA) and contagious caprine pleuropneumonia (CCPP) - none present in Britain 
  • Infections caused by M. gallisepticum in chickens, M. hyopneumoniae  in pigs, and Mycoplasma bovis in cattle can result in considerable economic loss 
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Birds - mycoplasma diseases

  • M. gallisepticum - chronic respiratory disease in chickens, turkeys, pheasants
    • coughing, nasal discharge, tracheal rales 
    • airsacculitis 
    • synusitis in turkeys, synusitis with exudate, swollen face 
  • M. synoviae 
    • synovitis, lameness, swelling of the joints and tendon sheaths
  • M. meleagridis and M. iowae 
    • leg and spine deformities 
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Pigs - mycoplasma diseases

  • M. hypopneumoniae (enzoonotic pneumonia)
    • high morbidity but low mortality, retarded growth 
    • chronic non productive cough 
  • M. hyorhinis 
    • systemic infection in pigs between 3 and 10 weeks old. Fever, reduced appetite, followed by swelling of the joints and lameness. polyserositis involving pleura, peritoneum, pericardium and synovial membranes 
  • M. hyosynoviae 
    • synovitis, arthritis, lameness 
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Cattle - mycoplasma disease

  • M. mycoides - cause of contagious bovine pleuroplenumonia 
    • subclinical, chronic and acute/fatal infections 
    • respiratory distress, coughing, nasal discharge, arthritis can occur in young animals 
  • M. bovis - also M. californicum, M. canadense, M. bovigenitalium 
    • drop in milk production, thickening of the milk with watery secretion sometimes progressing to purulent 
    • tissue destruction with swelling and fibrosis of the mammary gland is observed 
  • M. bovis and M. dispar
    • pneumonia with brinchiolitis 
  • M. bovigenitalium and Ureaplasma diversum
    • seminal vesiculitis in bulls, vulvitis, endometritis and abortion in cattle 
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Mycoplasma - diagnosis

  • clinical symptoms - pneumonia, arthritis, mastitis etc
  • laboratory diagnosis 
  • main tests 
    • PCR tests 
    • cultivation 
    • serology - western blot/ELISA 
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Mycoplasma - control

  • antibiotic treatment
    • tetracyclines, tylosin, erythromycin, lincomycin, spectinomycin
    • resistance can develop - infections are difficult to eliminate and a post-treatment carrier state often develops 
  • CBPP and CCPP - ususally controlled by culling infected herds
  • poultry - isolation or culling infected animals followed by strict containment measures and seological monitoring is an effective measure for control
  • similar measures control M. hypopneumoniae  in pig herds
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