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• Human infections caused by chlamydias, rickettsiae, and mycoplasmas are discussed separately because the responsible pathogens differ from most other bacteria in several ways

  
• Differences of chlamydias, rickettsiae, and mycoplasmas from most bacteria

  • Smaller
  • Different cell wall structure
  • Obligately intracellular parasites

  
• Cell Wall-Deficient Bacteria

  • Mycoplasma
  • Ureaplasma

  
• Mycoplasmataceae

  • Smallest known free-living forms
  • Do not have a cell wall
  • Highly fastidious
  • Slow growing
  • Facultative anaerobes
  • Require nucleic acid precursors, fatty acids, and sterols for growth
  • Believed to be highly reduced genetically
  • Human microbiota found in oropharynx, upper respiratory tract, and genitourinary tract

  
• MOT (Modes of Transmission)


  • Direct sexual contact
  • Transplanted tissue from donor to recipient
  • 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
• Well-established roles in human infections

  • M. pneumoniae
  • Ureaplasma urealyticum
  • Mycoplasma hominis

  
• Unique characteristics of Mycoplasma

  • Pleomorphic
  • Spherical or pear-shaped to filamentous with branching
  • Resistant to beta-lactams
  • Lack of reaction to Gram stain
  • Replicate by binary fission
  • Require sterols for membrane function and growth
  • Contains both DNA and RNA
  • Can replicate on their own and grow on artificial media

  
• Mycoplasma pneumoniae is also known as Eaton agent
• Primary Atypical Pneumonia (PAP)


  Caused by Mycoplasma pneumoniae
• Walking pneumonia is an informal term for pneumonia that isn't severe enough to require bed rest or hospitalization
• Symptoms of Walking Pneumonia

  • Notable non-purulent sputum
  • Dry cough
• M. pneumoniae strongly attaches to the mucosal cells and may reside intracellularly

  
• Determinants of Pathogenicity

  • Gliding motility
  • P1 protein
  • Hydrogen peroxide and Superoxide
  • Filamentous, flexible form
• Initiation of disease

  1. Attachment to respiratory mucosal cells

  2. Evasion from phagocytosis

  3. Modulation of the immune system
• Acceptable specimens


  • Body fluids
  • Tissues
  • Wound aspirates
  • Swabs of wounds
  • Throat
  • Nasopharynx
  • Urethra
  • Cervix
  • Vagina
• Serologic tests are more rapid and most useful for diagnosis
• Detection of specific IgM in a single serum sample is diagnostic of acute infection (M. pneumoniae)
• Culture media

  • SP-4 Mycoplasma medium
  • Shepard’s
  • A7B
  • Edward-Hayflick agar

  
• Culture is a difficult and lengthy process, which is why serological identification methods have been the primary method for identification
• Swabs for sample collection should be calcium alginate and Dacron swabs without disinfectants, analgesics, or lubricant
• Liquid specimens such as body fluids do not require transport media if inoculated to appropriate media within 1 hour of collection
• Cultivation media

  • Stuart’s medium
  • Trypticase soy broth supplemented with 0.5% bovine serum albumin
  • A3B broth
• Definitive identification involves overlaying suspicious colonies with 0.5% guinea pig RBC on PO4-buffered saline
• Genital Mycoplasma

  • Ureaplasma urealyticum
  • Ureaplasma parvum
  • Mycoplasma hominis
  • Mycoplasma genitalia
• Ureaplasma urealyticum is known as T (Tiny) strain Mycoplasma
• Ureaplasma urealyticum is found colonizing the vagina and cervix in 40%–80% of adult women
• Ureaplasma urealyticum can cause urinary calculi and non-gonococcal urethritis (NGU)
• Presence of mycoplasma in the placental membranes or amniotic fluid is associated with chorioamnionitis, preterm birth, spontaneously aborted fetuses, stillborns, and several neonatal disorders
• Mycoplasma spp.

  • Mycoplasma hominis
  • Mycoplasma genitalia

  
• Mycoplasma hominis is associated with postpartum fever and post-abortal fever
• Mycoplasma genitalia is linked to NGU in males only
• Manganese Chloride Urea Test is a rapid identification test for U. urealyticum
• The reaction for the Manganese Chloride Urea Test is observed under a dissecting microscope
• Chlamydia is the leading cause of STD
• More cases of STD are caused by Chlamydia trachomatis than by any other bacterial pathogen
• Chlamydia trachomatis infections are an enormous public health problem throughout the world
• Chlamydia is transmitted through anal, vaginal, or oral sex