Mycoplasmas Exam 2

Mycoplasmas

General Characteristics

• No Cell Wall:

  • Significance: Many antibiotics target the bacterial cell wall (e.g., penicillins, beta-lactam antibiotics), making them ineffective against mycoplasmas.

  • Membrane Structure: Strong membrane containing sterols helps maintain integrity in absence of a cell wall.

• Size: Among the smallest free-living organisms (around 0.2 microns), often appearing as specks of dust under a microscope.

• Cultural Characteristics:

  • Often exhibit a "fried egg" appearance on agar media (dense center with a thin peripheral layer).

Clinically Important Species

• Mycoplasma pneumoniae:

  • Causes respiratory infections; significant virulence due to cytotoxin production leading to cell death.

  • Adheres to respiratory epithelial cells, inhibits ciliary movement, leading to cough and respiratory distress.

  • Symptoms of Walking Pneumonia: Slow onset, less acute than typical bacterial pneumonia, often resulting in community-acquired infections.

• Mycoplasma genitalium:

  • Associated with urethritis (not gonococcal). So, NGU, and pelvic inflammatory disease.

• Mycoplasma hominis

  • Respiratory and genitourinary, ststemic infection in compromised patients and pyelonephritis.

• Ureaplasma urealyticum:

  • Involved in various urogenital infections including pelvic inflammatory disease. Can be respiratory and genitourinary. NGU, premature birth or spontaneous abortion.

Mycoplasma pneumoniae Specifics (walking pneuomnia)

• Cytotoxin:

  • Causes significant cell death and contributes to the pathophysiology of the disease.

• Virulence Factors:

  • Attachment to epithelial cells due to special terminal protein attachment factor that disrupts normal respiratory function and ciliary action or the beating of the cilia.

• Symptoms:

  • Gradual onset of headache, sore throat, chest pain; can culminate in full-blown pneumonia.

  • Often causes primary atypical pneumonia or walking pneumonia. Atypical means the onset is insidious, not abrupt as with bacterial pneumonias like S. pneumoniae.

  • Not treatable with penicillin, no cell wall.

• Incidence and Diagnosis:

  • High incidence, especially in young children; diagnosis includes antibody detection and PCR tests.

  • Pneumoniae caused by this bug is about 20% community acquired. Can be skin lesions called erythema multiforme. Can cause eye infections and lead to stevens johnson syndrome that causes immune system to overreact.

• Treatment:

  • Not treatable with beta-lactams; require antibiotics targeting protein synthesis (e.g., macrolides, tetracyclines). Tetracycline in adults and erythromycin.

  • Diagnosis :PCR

Mycoplasma Hominis and Genitalium

• Diseases:

  • Mycoplasma hominis linked with pelvic inflammatory disease, vaginitis; can lead to severe complications including spontaneous abortion.

  • Mycoplasma genitalium associated with non-gonococcal urethritis (NGU) and reproductive complications, prostatitis.

  • PID is an ascending infection in women 15-25 usually.

  • Chronis Fatigue Syndrome

• Diagnosis for Urogenital Infections:

  • Similar to pneumonia, PCR is a preferred diagnostic method.

L form Bacteria

• Definition: Cell wall-deficient bacteria observed in clinical settings or laboratory. L-form bacteria are cell wall deficient.

• Two Types:

  • Spheroplasts: retain some cell wall, unstable, may revert. These are unstable and can revert to their original morphology.

  • Protoplasts: lose all cell wall, stable, fragile, no sterols. They are unable to revet to their original morphology.

  • L form indications are wall-deficient bacterial variants, can produce “part” of the cell wall only, so may be osmotically fragile. No sterols in the cell membrane, so reproduction is stopped by penicillin.

• Association with Diseases: Potential involvement in chronic fatigue syndrome and sarcoidosis, highlighting their clinical significance. L-forms may be involved in sarcoidosis, a chronic disease of unknown cause marked by the formation of nodules in the lungs and liver and lymph/salivary glands.

Rickettsia and Chlamydia

General Characteristics of Rickettsia

• Type:

  • Gram-negative, obligate intracellular organisms; small size (0.1 micron), arthropod vector, coccobacillus.

• Major Types and Characteristics:

  • Rocky Mountain Spotted Fever (Rickettsia rickettsii).

  • Transmission: Via ticks and mites and fleas (dog tick, brown dog tick); causes endothelial cell infection, increased vascular permeability.

  • Infect endothelial cells.

  • Symptoms: Fever, rash (starts on wrists and ankles, spreads), possibly progressing to more severe complications. Infection can become more severe, skin necrosis, edema, respiratory issues.

  • Diagnosis: PCR, tissue, serology.

  • Treatment: doxycycline, chloramphenicol, macrolides.

Major Rickettsial Infections

• Rocky Mountain Spotted Fever:

  • Seasonal prevalence, especially in southern states; diagnosis via PCR, treated with appropriate antibiotics.

• Typhus (Rickettsia prowazekii):

  • Transmitted by lice in unsanitary conditions; sudden onset of fever and rash.

  • Rickettsia prowazekii causes typhus.

  • Epidemic typhus outbreaks occur in areas with poor sanitation, rare.

  • Murine typhus, from R. typhi comes from fleas, in tropics and subtropics.

  • Scrub typhus, from Orientia tsutsugamushi is from mites, chiggers, in SE asia, japan, australia.

  • Diagnosis: PCR

  • Treatment: doxycyline

• Rickettsial Pox (Rickettsia akari):

  • Mild symptoms; transmitted by mites.

  • Diagnose with serology.

  • Treat with doxy.

Coxiella burnetii (Q Fever)

• Characteristics: Gram-negative, intracellular, zoonotic infection; resistant to environmental stress; primarily sheep and goats are reservoirs. Shares virulence genes with legionella pneumophila. Highly resistant in environments, Q is “query” fever, contact with animals the aerosols they produce and inhaling. Fever, chills, headache, self-limiting. Can progress to pneumonia, incubates 2-3 weeks, and can develop months to a year after initial infection. Can recover without antibiotics.

• Symptoms: Undulating fever, can potentially lead to severe respiratory issues.

• Diagnosis and Treatment: PCR tests; generally, the infection is self-limiting.

General Characteristics of Chlamydia

• Type: Obligate intracellular parasites, difficult for immune response to target. Gram negative, coccobacillus.

• Key Species:

  • Chlamydia trachomatis: leads to ocular infections and genitourinary diseases, major cause of preventable blindness.

  • Chlamydia pneumoniae: aerosol transmission, community-acquired pneumonia.

  • Chlamydia psittaci: associated with birds, leading to respiratory symptoms.

Chlamydia trachomatis

• Symptoms and Associations:

  • Leading cause of blindness and sexually transmitted infections; presents as urethritis, pelvic inflammatory disease.

  • Higher incidence in women, especially those using oral contraceptives.

  • Infects epithelial cells of cervix, urethrae, rectum, and conjunctiva. Major cause of blindness worldwide. UTI is most common. STI, higher rate versus gonorrhea.

  • Risk of transmission per sex is less than gonorrhea, and risk increases with frewuency of sex. Co-infection with gonorrhea is common and increases the risk of transmission.

  • Urethritis is common in men and has a 7-14 day incubation period with potential burning and discharge along with potential prostate infection.

  • In women, high rated associated in contraceptive use, most cases asymptomatic, PID in 20%, infertility, ectopic pregnancy, and discharge, bleeding, burning urination and abdominal pain.

  • Arthritis (reiters syndrome) can occur after infection, infant conjunctivitis, lymph node ulcerative diease, and eye infection (blindness)

  • TRACHOMA

    • disease progression conjuctiva= hyperemia and folliculitis

    • most common cause of preventable blindness

    • Surgery, antibiotics, facial cleanliness, environment

    • Neonatal vertical transmission, just like with neisseria.

      • treat with erythromycin or silver nitrate

      • pneumonia: gentamicin

• LGV (lymphogranuloma Venereum)

  • sexual

  • serovars 1.2.3

  • Ulceration at site of infection, buboes, painful regional lymphadenopathy, proctitis and anorectal pain.

• Diagnosis:

  • Nucleic acid tests (PCR) and serology for infection detection. Culture, NAAT

• Treatment:

  • Doxycycline, erythromycin, azithromycin, ofloxacin

Chlamydophila pneumoniae

• Transmission: Aerosol; classified under community-acquired pneumonia.

• Treat with doxy, beta lactams dont work. Can use macrolides, fluoroquinolones, and sulfa drugs too.

• Clinical Considerations: PCR for diagnosis; treat promptly to prevent complications.

Chlamydia psittaci

• Reservoir: Birds, pet birds particularly.

• Symptoms: Fever, chills, headache, nonproductive cough; potential for systemic infections.

• Diagnosis and Management: Laboratory tests; importance of controlling aviary sources.

Closing Remarks

• Final thoughts on the importance of understanding these pathogens for effective diagnosis, treatment, and prevention.

• Reminder for students to prepare questions for the follow-up session on Friday at 09:00.

Which of the following micororganisms is not sensitive to penicillin? Mycoplasma Pneumonia is not. However, staph aureas, strep pneum, and L-forms of bacteria are.