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• Chlamydias, rickettsiae, and mycoplasmas

  • They are smaller than most other bacteria
  • The structure of their cell walls is different
  • Chlamydias and many rickettsiae are obligately intracellular parasites

  
• Cell Wall-Deficient Bacteria

  Mycoplasma and Ureaplasma

  
• Characteristics of Mycoplasmataceae

  • Smallest known free-living forms (approximately 0.3-1.0 μm in diameter)
  • Do not have a cell wall
  • Highly fastidious
  • Slow growing
  • Facultative anaerobes
  • Require nucleic acid precursor molecules, fatty acids, and sterols such as cholesterol for growth
  • Believed to be highly reduced genetically - fewer opportunities to adapt to environmental changes (Have lower guanine/cytosine (G/C) ratio than most bacteria)
  • Found mainly in the oropharynx, upper respiratory tract, and genitourinary tract of human microbiota

  
• Modes of transmission for Mycoplasma

  1. Direct sexual contact

  2. Transplanted tissue from donor to recipient

  3. From mother to fetus during childbirth or in utero
• M. genitalium accounts for approximately 15% to 20% of nongonococcal urethritis (NGU); cervicitis and pelvic inflammatory disease (PID)
• M. fermentans has been isolated from specimens such as bronchoalveolar lavage, bone marrow, peripheral blood, and the throats of children with pneumonia

  
• M. amphoriforme has been detected in the lower respiratory tract in patients with chronic respiratory disease and antibody deficiencies
• Mycoplasma and Ureaplasma with well-established roles in human infections

  • M. pneumoniae - isolated from respiratory tract
  • Ureaplasma urealyticum - genitourinary tract
  • Mycoplasma hominis - genitourinary tract

  
• Mycoplasma


  • Pleomorphic
  • Spherical or pear shaped to filamentous with branching
  • Resistant to beta-lactams (Penicillin-resistant)
  • Lack of a reaction to Gram stain (Gram-negative)
  • Replicate by binary fission
  • Require sterols (cholesterol) for membrane function and growth
  • Contains both DNA and RNA
  • Can replicate on their own and grow on artificial media
  • Ability to ferment glucose, utilize arginine and hydrolyze urea

  
• Mycoplasma can be isolated from the internal organs of stillborn, premature, and spontaneously aborted fetuses

  
• Mycoplasma pneumoniae


  Also known as Eaton agent<|>Colonizes the mucosa of the respiratory tract
• Diseases caused by Mycoplasma pneumoniae

  • Primary Atypical Pneumonia (PAP) / Walking Pneumonia
  • Community-acquired pneumonia & tracheobronchitis in children & young adults
  • Hemolytic anemia
  • Arthritis, acute glomerulonephritis
• Mycoplasma pneumoniae


  • Most frequently affects persons aged 5–20 years
  • Causes notable non-purulent sputum and dry cough
  • Strongly attaches to the mucosal cells and may reside intracellularly within host cells, resulting in a chronic persistent infection that may last for months to years
• Determinants of Mycoplasma pneumoniae pathogenicity

  • Gliding motility: penetrate through respiratory secretions
  • P1 protein: for attachment to host cells
  • Hydrogen peroxide and Superoxide: injure mucosal cells, causing ciliostasis and sloughing of superficial cells
  • Filamentous, flexible form: facilitate localization in crypts and folds and between microvilli and cilia, where it is protected from phagocytosis

  
• Initiation of Mycoplasma pneumoniae disease

  1. Attachment to respiratory mucosal cells

  2. Evasion from phagocytosis

  3. Modulation of the immune system

  
• Acceptable specimens for Mycoplasma pneumoniae

  • Body fluids
  • Tissues
  • Wound aspirates and swabs
  • Throat swab
  • Blood
  • Other respiratory specimens such as BAL, sputum and lung tissue

  
• Serologic tests for Mycoplasma pneumoniae

  • Cold Agglutination Reaction
  • Complement Fixation
  • ELISA

  
• No direct method or Gram staining can be used for identification of Mycoplasma pneumoniae

  
• Culture of Mycoplasma pneumoniae is clinically non-contributory as isolation may require several weeks

  
• Culture media for Mycoplasma

  • SP-4 Mycoplasma medium
  • Shepard's
  • A7B
  • Edward-Hayflick agar (E-agar)

  
• Definitive identification of Mycoplasma is by overlaying suspicious colonies with 0.5% guinea pig RBC on PO4-buffered saline (Adherence of RBCs to colonies)

  
• Genital Mycoplasma

  • Ureaplasma spp. (Ureaplasma urealyticum, Ureaplasma parvum)
  • Mycoplasma spp. (Mycoplasma hominis, Mycoplasma genitalia)

  
• Ureaplasma urealyticum


  Also known as T (Tiny) strain Mycoplasma<|>Found colonizing the vagina and cervix in 40%–80% of adult women<|>Cause urinary calculi and non-gonococcal urethritis (NGU)<|>Intrarenal abscess formations in the transplanted kidney
• Vaginal colonization with the genital mycoplasmas in pregnant women is not associated with disease
• Presence of mycoplasma in the placental membranes or amniotic fluid is associated with chorioamnionitis, preterm birth, spontaneously aborted fetuses, stillborns and several neonatal disorders (perinatal pneumonia and sepsis in preterm infants)
• Mycoplasma hominis


  Associated with postpartum fever & post-abortal fever<|>Related to both pelvic inflammatory disease (PID) and pyelonephritis
• Mycoplasma genitalia


  Linked to NGU in males only
• Manganese Chloride Urea Test


  A rapid identification test for U. urealyticum<|>Positive result is a dark brown precipitate of manganese oxide around colonies
• No commercial serologic assays are available for the genital mycoplasmas, use of serology is confined to research
• Pelvic inflammatory disease (PID)


  Infection of one or more of the upper reproductive organs, including the uterus, fallopian tubes and ovaries
• Tests for Genital Mycoplasma


  • GM (Genital Mycoplasma) agar
  • 0.5nM MnSo4
  • 1nM MnSo4
  • Urease Spot Test
  • BAP, strains of M. hominis, but not of U. urealyticum, produce nonhemolytic, pinpoint colonies that do not Gram stain. These colonies can be stained with the Dienes or acridine orange stains

  
• Mycoplasma ferments glucose to lactic acid, the pH change is detected by a color change in a dye indicator
• Mycoplasma hominis is an opportunistic urogenital pathogen in vertebrates, it is a non-glycolytic species that produces energy via arginine degradation

  
• There is no vaccine for prevention of Mycoplasma infections, thus barrier protection for STDs is the only prevention method
• Colonies of Mycoplasma pneumoniae visualized under 100x magnification

  
• Colonial growth characteristics of Mycoplasma in agar medium

  
• Antibiotics effective against Mycoplasma

  • Macrolides
  • Tetracycline
  • Ketolides
  • Fluoroquinolones
• Obligate Intracellular and Nonculturable Bacterial Agents

  • Chlamydia, Rickettsia, Orientia, Anaplasma, and Ehrlichia are prokaryotes that differ from most other bacteria with respect to their very small size and obligate intracellular parasitism
  • Coxiella, Calymmatobacterium granulomatis and Tropheryma whipplei are also difficult to cultivate or are noncultivable
• Chlamydiaceae

  Obligate intracellular bacteria<|>Similar to gram-negative bacilli in that they have lipopolysaccharide (LPS) as a component of the cell wall<|>Have a Major Outer Membrane Protein (MOMP) that is very diverse<|>Have a unique developmental life cycle with an intracellular, replicative form (reticulate body) and an extracellular, metabolically inert, infective form (elementary body)

  
• Chlamydia developmental cycle

  1. After infection of a host cell, the elementary body differentiates into a reticulate body

  2. The reticulate body divides by binary fission within vacuoles

  3. As the numbers of reticulate bodies increase, the vacuole expands, forming an intracytoplasmic inclusion

  4. The reticulate bodies then revert to elementary bodies

  5. 48 to 72 hours postinfection, the elementary bodies are released from the host cell