Mycoplasmas and Actinomycetes

1. Mycoplasmas and Actinomycetes Presented by د. آصف احمد محمد جي مان فطاني بكاالوريوس الطب والجراحة (جامعة الملك عبدالعزيز) ماجستير الكائنات الدقيقة الطبية والجزيئية (جامعة مانشستر) دكتوراه الكائنات الدقيقة الطبية (جامعة مانشستر – بريطانيا) Dr Asif Jiman-Fatani, MB ChB, MSc, PhD (UK) Assistant Professor in Medical Microbiology, Faculty of Medicine, King Abdulaziz University Consultant Microbiologist Head, Clinical Microbiology Laboratories King Abdulaziz University Hospital

2. MYCOPLASMASCharacteristics • Lacking cell wall • Resistant to antibacterials that inhibit cell wall synthesis • Gram’s stain : Not useful • Pleomorphic • Cannot be classified as either cocci or bacilli • Enclosed in a plasma membrane • Lipid bilayer membrane containing sterols • Smallest free-living organisms • Pass through bacteriologic filters • Can be cultured in vitro.

3. MYCOPLASMAS Mycoplasma pneumoniae→Atypical Pneumonia Mycoplasma hominis→ STI: Non-gonococcal Urethritis, Cervicitis, PID Ureaplasma urealyticum→ STI: Non-gonococcal Urethritis, Cervicitis, PID

4. Mycoplasma pneumoniae (Eaton’s reagent)Habitat and Transmission • Habitat is the human respiratory tract. • Transmission : Respiratory droplets.

5. Mycoplasma pneumoniaePathogenesis • P1 adhesion protein • M. pneumoniae binds to respiratory ciliated epithelium • Adherence results in ciliostasis & cell destruction → reduced ciliated clearance • Bacteria then gain access to the lower respiratory tract • Produces hydrogen peroxide : may damage the respiratory tract. • No exotoxins produced. • No endotoxin because there is no cell wall.

6. Mycoplasma pneumoniaeDiseases • Atypicalpneumonia : • Clinical Features: Fever – Dry cough “or scantily productive cough” • Walking pneumonia • Complications: Mild hemolytic anaemia • Upper Respiratory Diseases : • Otitis Media • Pharyngitis • Tracheobronchitis

7. Mycoplasma pneumoniaeLaboratory Diagnosis • Specimens: but scanty sputum • Gram stain : not useful. • Culture: on special bacteriologic media. Takes at least 10 days to grow (too long to be clinically useful). • Colonie: Fried egg appearance Serology • A cold-agglutinin titer of 1:128 or higher is indicative of recent infection • Cold agglutinin: IgM autoantibodies against red blood cells that agglutinate these cells at 4 °C but not at 37 °C • Complement fixation test for antibodies to Mycoplasma pneumoniae is more specific. PCR Note : Diagnosis relies on clinical findings

8. Mycoplasma pneumoniaeTreatment • Erythromycin or … • Tetracycline. Prevention • No vaccine or drug is available

10. Genital Mycoplasmas • Mycoplasma hominis→ STD: Non-gonococcal Urethritis, Cervicitis, PID • Ureaplasma urealyticum→ STD: Non-gonococcal Urethritis, Cervicitis, PID

12. Actinomycetes

13. Actinomycetes • Gram positive bacteria • Filamentous branching bacilli • Superficially resemble fungi on morphologic grounds • They are prokaryotes • Has bacterial size

14. Actinomycetes • Few are pathogenic to human, the most important are : • Actinomyces israelii • Nocardia astroides

15. ACTINOMYCETESActinomyces israelii Gram-positive filamentous branching bacilli Anaerobic Grows slowly

16. Actinomyces israeliiHabitat and Transmission • Habitat : Found as scanty normal commensal in the: • Mouth, especially anaerobic crevices around the teeth • Colon • Vagina • Disease begins when these normal flora enter adjacent sterile tissue e.g, by trauma, surgery • Transmission into tissues occurs during : • Dental extraction - Poor dental hygiene • Trauma (mouth – uterus) • Organism also aspirated into lungs, causing thoracic actinomycosis.

17. Actinomyces israeliiPathogenesis • Infections occur in both : • Normal hosts • Immunocompromised patients • No toxins or virulence factors known. • Organism forms sinus tracts that open onto skin and contain yellow “sulfur granules” • Sulfur granules : are made up of large masses of organisms microcolonies of filamentous bacteria

18. Actinomyces israeliiDisease • Actinomycosis (abscesses with draining sinus tracts) • Chronic suppurative abscess • The lesion (Mycetoma) : • Begins as a hard red swelling • Ddevelops slowly, becomes filled with pus • Draining with sinus formation • Sites: • Oral-facial abscesses (> 50% of cases) • Often associated with trauma or dental extraction • Abdominal infections: • Abscess. Many after appendicitis • Uterine infection : • Associated with intrauterine contraceptive devices • Chest infection • Invasive infections in immunocompromised patients

19. Actinomyces israeliiLaboratory Diagnosis • Specimen: Pus • Filaments may aggregate to form visible granules “Sulphur granules” in pus: Yellowish particles • No sulphur • Microscopy: • Sulfur Granules : Gram-positive filamentous, branching rods • Culture: • Anaerobic culture on blood agar plate (10 days) • Molar teeth colonies • No serologic tests.

20. Actinomyces israeliiTreatment • Penicillin • For up to 3-12 months • Tetracyclin or Clindamycin • For penicillin-allergic patients • Surgical drainage • Prevention • Good oral hygiene • Prophylactic antibiotics in association with GIT or oral trauma or surgery • No vaccine is available.

21. ACTINOMYCETES Nocardia asteroides

22. Nocardia asteroidesDisease • Nocardiosis (especially lung and brain abscesses).

23. Nocardia asteroidesCharacteristics • Gram positive filamentous, branching rods. • Aerobic • Acid-fast (weakly)

24. Nocardia asteroidesHabitat and Transmission • Habitat is the soil. • Transmission : • Airborne particles, which are inhaled into the lungs • Implantation : by contamination of skin wounds

25. Nocardia asteroidesPathogenesis • Predisposing Factors: • Immunosuppression • HIV • Cancer • No toxins or virulence factors known.

26. Nocardia asteroidesDiseases • Diseases: Abscesses in: • Lung • Brain • Kidney

27. Nocardia asteroidesLaboratory Diagnosis • Specimen : Pus • Microscopy : • Gram-stained smear : Gram positive filamentous, branching rods • Ziehl-Neelsen stain (modified) : weakly AFB (branching) • Culture : • Aerobic culture on blood agar plate. • No serologic tests.

28. Nocardia asteroidesTreatment • Sulfonamides • Long duration • Nocardia is resistant to penicillin Prevention • No vaccine is available.

29. Differences between Actinomyces israelii & Nocardia astroides