OPTO435 Microbiology II Gamal El-Hiti

1. OPTO435 Microbiology II Gamal El-Hiti

2. Chlamydia trachomatis and Mycobacterium tuberculosis Lecture Six

3. Learning Outcomes OPT435 L06 – W08

4. Chlamydiae  The family Chlamydiaceae consists of small obligate parasitic bacteria that depend on the host cell for energy in the forms of ATP and NAD+.  The family has three important human pathogens. Chlamydia pneumoniae, Chlamydia psittaci and Chlamydia trachomatis. OPT435 L06 – W08

5. Chlamydiae  Chlamydiae are small, round-to-ovoid organisms that vary in size during the different stages of their replicative cycle.  The chlamydial cell envelope consists of two lipid bilayers resembling a Gram-negative envelope.  The Chlamydial DNA genome is small. OPT435 L06 – W08

6. Chlamydiae  Chlamydiae have ribosomes and can synthesize their own proteins.  Therefore, they are sensitive to antibiotics that inhibit protein biosynthesis process.  Physiology of Chlamydiae Chlamydiae are energy parasites that require the living cells for growth.  They are unable to synthesize their own ATP or regenerate NAD+ by oxidation.  Chlamydiae produce CO2 from glucose and carry out bacterial metabolic activities. OPT435 L06 – W08

7. Chlamydiae  Pathogenesis of Chlamydiae Chlamydiae have a unique life cycle, with morphologically distinct infectious and reproductive forms. OPT435 L06 – W08

8. Chlamydiae OPT435 L06 – W08

9. Chlamydiae  Clinical significance of Chlamydiae  Chlamydiae are not stained using the Gram stain protocol.  It can be visualized under light microscopy by stains that preserve the host cell.  Direct immunofluorescence is also a common as a useful procedure.  In C. trachomatis, a matrix of glycogen-like material accumulates in the inclusions, which can be shown by staining with iodine.  Other species do not produce this reaction. OPT435 L06 – W08

10. Chlamydiae  Nongonococcal urethritis (NGU)  Annually, more than 4 million urogenital Chlamydia trachomatis infections occur in the US in youngand sexually active individuals.  In men, the urethra is the initial site of infection.  Women may present with cervicitis and/or urethritis.  Infections are often asymptomatic, although communicable. OPT435 L06 – W08

11. Chlamydiae OPT435 L06 – W08

12. Chlamydiae  Chlamydial nongonococcal urethritis is similar to infections caused by Neisseria gonorrhoeae, although the incubation time is longer (2 to 3 weeks).  Two infections often occur simultaneously. OPT435 L06 – W08

13. Chlamydiae  Neonatal conjunctivitis Over 50% of the infants born to women infected with Chlamydia trachomatis, serotypes D–K will contract symptomatic infection on passage through the birth canal.  The most common presentation is the inclusion conjunctivitis of the newborn.  This acute, purulent conjunctivitis usually heals after the appropriate antimicrobial therapy, without permanent damage to the eye. OPT435 L06 – W08

14. Chlamydiae  If C. trachomatis infections untreated, the infection can lead to permanent scarring of the cornea or conjunctiva. OPT435 L06 – W08

15. Chlamydiae  Treatment and prevention  Chlamydiae are sensitive to a number of broad-spectrum antibacterial drugs.  Resistant strains have not been reported in the clinical setting.  Azithromycin and tetracycline are currently the drugs of choice.  Erythromycin should be used in young children and pregnant women due to the effects of tetracyclines on the teeth and bones. OPT435 L06 – W08

16. Treponema pallidum  Syphilis is primarily a sexually transmitted infection caused byTreponema pallidum (spirochete).  Starts with a small lesion.  Several progressive stages of the disease can span a period of 30 years or more.  Often ends in syphilitic dementia or cardiovascular damage.  The causative organism of syphilis is extremely fastidious and fragile. OPT435 L06 – W08

17. Treponema pallidum OPT435 L06 – W08

18. Treponema pallidum  Pathogenesis of Treponema pallidum  Treponema pallidum is transmitted by sexual contact or transplacental. Treponema pallidum is so sensitive to the environment and cannot survival outside the host cells for more than few minutes. Treponema pallidum enters the body through a break in the skin or by penetrating the mucous membranes.  Syphilis occurs in three stages as primary, secondary and tertiary stages. OPT435 L06 – W08

19. Treponema pallidum  Primary syphilis is a chancre.  Secondary syphilis is a rash and may be accompanied by syphilitic hepatitis.  Tertiary syphilis is a gumma of skin. OPT435 L06 – W08

20. Treponema pallidum  Treatment and prevention  One single treatment with penicillin is curative for primary and secondary syphilis.  No antibiotic resistance has been reported.  For patient sensitive to penicillin, tetracyclines may be effective.  There are over 10,000 new cases of syphilis in the US every year.  There is no vaccine against T. pallidum and prevention depends on safe sexual practices. OPT435 L06 – W08

21. Mycobacteria  Mycobacteria are slender rods with lipid-rich cell walls.  Mycobacterial cell wall is ca. 60% lipid.  Size is 3  3 m.  They are resistant to penetration by chemical dyes such as those used in the Gram stain.  Mycobacteria are strictly aerobic. OPT435 L06 – W08

22. Mycobacteria  The unusual cell walls made mycobacteria convey resistance to disinfectants and strong acids or alkalis.  Mycobacteria are also resistant to dry environment.  Can not resist heat or ultraviolet irradiation.  Most species grow slowly with generation times of 8 to 24 hours.  Mycobacterium tuberculosis causes tuberculosis (TB) in Human that can be spread from one person to another through air. OPT435 L06 – W08

23. Mycobacterium tuberculosis OPT435 L06 – W08

24. Mycobacterium tuberculosis OPT435 L06 – W08

25. Mycobacterium tuberculosis OPT435 L06 – W08

26. Mycobacterium tuberculosis  Epidemiology of M. tuberculosis  Patients with active pulmonary tuberculosis shed large numbers of organisms by coughing, creating aerosol droplet nuclei.  The organisms can remain viable as droplet nuclei suspended in room air for at least 30 minutes.  Transmission from one person to another occurs by inhalation of the aerosol.  A single infected person can pass the organism to numerous people. OPT435 L06 – W08

27. Mycobacterium tuberculosis  Pathogenicity of M. tuberculosis  Mycobacteria will multiply after inhalation.  Within 2 to 4 weeks, many bacilli are destroyed by the immune system, but some survive and are spread by the blood.  M. tuberculosis grow within host cells.  When engulfed by macrophages, bacterial sulfolipids inhibit the fusion of phagocytic vesicles with lysosomes.  M. tuberculosis remains viable within the host for decades. OPT435 L06 – W08

28. Mycobacterium tuberculosis OPT435 L06 – W08

29. Mycobacterium tuberculosis  Immunity against M. tuberculosis  M. tuberculosis stimulates both a humoral and a cell mediated immune response.  Clinical significance of M. tuberculosis  Primary tuberculosis occurs in a person who had no previous contact with the organism.  For the majority of cases (ca. 95%), the infection becomes arrested, and most people are unaware of this initial encounter.  The only evidence of tuberculosis may be a positive tuberculin test. OPT435 L06 – W08

30. Mycobacterium tuberculosis  A chest radiograph sometimes shows the initial pulmonary nodule.  Mycobacterium tuberculosis may be accompanied by systemic involvement such granulomatous conjunctivitis.  Tuberculin reaction A test that is a manifestation of delayed hypersensitivity to protein antigens of Mycobacterium tuberculosis. A positive reaction usually develops 4 to 6 weeks after initial contact with the organism. OPT435 L06 – W08

31. Mycobacterium tuberculosis OPT435 L06 – W08

32. Mycobacterium tuberculosis  Treatment and prevention  Several chemotherapeutic agents are effective against M. tuberculosis.  Isoniazid, rifampin, ethambutol, streptomycin and pyrazinamide are the principal or “first-line” drugs.  Public health measures (e.g. tuberculin tests and chest radiographs) needs to be taken to prevent illness.  A vaccine against tuberculosis has been available since early in the 20th century. OPT435 L06 – W08

33. Mycobacterium tuberculosis OPT435 L06 – W08