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Questions and Answers
Which staining method allows for the better visualization of bacteria associated with the discussed microorganisms?
What process do Elementary Bodies (EB) undergo to enter the host cells?
What characterizes the Reticulate Bodies (RB) compared to Elementary Bodies (EB)?
What is the significance of host cell rupture in the lifecycle of Reticulate Bodies?
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What distinguishes Elementary Bodies (EB) from Reticulate Bodies (RB)?
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What type of morphology do the discussed microorganisms exhibit?
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Which of the following species is NOT classified under the chlamydiae?
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How do chlamydiae reproduce?
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Which characteristic is NOT associated with chlamydiae?
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What is the main risk factor associated with chlamydial infections?
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What is the primary zoonotic disease associated with psittacine birds?
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What is the drug of choice for treating psittacosis?
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Which type of antibodies are commonly tested in serology for Chlamydia pneumoniae infection?
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What is a key characteristic of Chlamydia pneumoniae infections?
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Which method is utilized for diagnosing psittacosis in the laboratory?
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Which serotypes of Chlamydia trachomatis are responsible for causing Trachoma?
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What is the primary mode of transmission for Trachoma?
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Which type of infections is associated with Chlamydia trachomatis serotypes D-K?
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Which condition can result from scarring and inversion of the eyelids due to Trachoma?
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What is a common symptom of Trachoma in its early stages?
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How long is the typical incubation period for Inclusion conjunctivitis?
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Which organism is resistant to sulfonamide treatment?
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What is a serious consequence of untreated Trachoma?
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What percentage of infected women are asymptomatic in genital C.trachomatis infections?
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Which of the following is NOT a complication associated with chlamydial infections?
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What is the most common method for laboratory diagnosis of genital C.trachomatis infections?
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What is the primary stage of Lymphogranuloma Venereum (LGV) characterized by?
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Which of the following treatments is commonly used for genital chlamydial infections?
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What is the incubation period for Lymphogranuloma Venereum (LGV) after exposure?
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Which of these is a mode of transmission for genital C.trachomatis infection?
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Which technique is utilized to culture C.trachomatis in a laboratory setting?
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Study Notes
Chlamydiae Classification
- Chlamydia are obligate intracellular pathogens
- They are classified as:
- Phylum: Chlamydiae
- Class: Chlamydiae
- Order: Chlamydiales
- Family: Chlamydiaceae
- Genus: Chlamydia
- Species: C. trachomatis, C. psittaci, C. pneumoniae
Chlamydia Overview
- Chlamydia are small, round to oval bacteria
- They were initially thought to be large viruses
- They possess a cell wall lacking peptidoglycan, similar to Gram-negative bacteria.
- They contain both RNA and DNA.
- They are susceptible to some antibacterial agents such as tetracyclines and erythromycin.
- Chlamydia lack the necessary energy machinery for independent existence.
- They cannot synthesize ATP or oxidize NADH.
- They reproduce through a replicative cycle, followed by binary fission.
- They are highly infectious and many species produce heat-labile toxins.
Chlamydia Morphology and Life Cycle
- Chlamydia exist in two forms:
- Elementary bodies (EB): Extracellular, infectious, invasive stage, metabolically inert. They enter the body through endocytosis, a process similar to phagocytosis.
- Reticulate bodies (RB) or initial bodies (IB): Intracellular, non-infectious, metabolically active. When EB undergo a transformation, they reorganize into RB which are less dense. They obtain energy (ATP) from the host cell and this transformation takes approximately 24-72 hours. RB undergo binary fission within the host cell's intracytoplasmic vacuole/phagosome. Host cell rupture releases daughter EB, allowing the infection to spread.
Chlamydia Species
- The three main species of Chlamydia can be distinguished by several parameters:
- C. psittaci: Contains glycogen in intracytoplasmic inclusion body, sensitive to sulfonamide. Causes psittacosis in birds and humans.
- C. trachomatis: Lack glycogen in intracytoplasmic inclusion body, resistant to sulfonamide. Causes trachoma, inclusion conjunctivitis, and various genital infections.
- C. pneumoniae: Lack glycogen in intracytoplasmic inclusion body, resistant to sulfonamide. Causes atypical pneumonia, bronchitis, and sinusitis.
Chlamydia trachomatis Infections
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Ocular Infections:
- Trachoma: Caused by serotypes A, B, and C. It is a chronic keratoconjunctivitis that is a leading cause of preventable blindness globally. Transmission occurs through direct contact, indirect contact via fomites, and during childbirth.
- Inclusion Conjunctivitis: Caused by serotypes D-K. It is an acute suppurative disease of the conjunctiva. Occurs in infants and adults and has an incubation period of 2-5 days. Transmission is by direct or indirect contact.
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Genital Infections: Caused by serotypes D-K. It is a common cause of sexually transmitted infections (STIs) worldwide.
- Non-gonococcal urethritis (NGU) is common, particularly among young adults.
- Other genital infections include cervicitis, epididymitis, salpingitis, endometritis, pelvic inflammatory disease (PID), proctitis, pharyngitis, and Reiter's syndrome.
- Chlamydial infections can lead to infertility and sterility.
Chlamydia psittaci Infections
- Pathogen: Primarily infects birds, particularly psittacine birds (e.g., parrots), and other avian species.
- Transmission: Humans get infected by inhaling bacteria from infected bird droppings.
- Disease: It causes psittacosis (ornithosis) in humans, a zoonotic disease of the lower respiratory tract. Symptoms range from mild to severe pneumonia and meningo-pneumonitis.
Chlamydia pneumoniae Infections
- Prevalence: Highly common worldwide, with 30-50% of the population having antibodies to C. pneumoniae.
- Transmission: Spread through airborne transmission. No known animal reservoir.
- Disease: Most infections are asymptomatic. It can cause upper and lower respiratory tract infections (URTI and LRTI), including atypical pneumonia, bronchitis, sinusitis, and pharyngitis. It can also exacerbate asthma.
Chlamydia Diagnosis
- Clinical diagnosis: Based on patient history and clinical symptoms.
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Laboratory diagnosis:
- Specimens: Post-voidal urine, urethral swab, endometrial scraping, culdocentesis, conjunctival scraping, posterior nasopharyngeal swab, tracheal/bronchial aspirates.
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Methods:
- Urine tests: Detect C. trachomatis genes, results in 24 hours.
- Culture: In McCoy cells,takes 3 days or more. Requires expertise and experience.
- DFA test: Direct fluorescent antibody test.
- Enzyme immunoassay:
Chlamydia Treatment and Prevention
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Treatment: Early detection and treatment are crucial.
- Antibiotics: Tetracycline, doxycycline, minocycline, erythromycin, and azithromycin.
- Complications: HIV/AIDS, PID, subfertility, infertility.
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Prevention and Control:
- Prophylactic treatment: Use of prophylactic ophthalmic eye drops for newborns, oral tetracycline or sulfonamides.
- Hygiene: Personal and family hygiene.
- Trachoma clinics: Establishment of dedicated clinics in endemic areas.
Lymphogranuloma Venereum (LGV)
- Caused by: Unique serovars of Chlamydia trachomatis (L1, L2, L3). These serovars differ from those causing urethritis, cervicitis, and proctitis (D-K).
- Presentation: Varies depending on the site of infection.
- Incubation period: 3 days to 1 month after exposure.
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Progression: It is an invasive, systemic infection that progresses in three stages:
- Primary (Ulcer) stage: Painless vesiculo-papular ulceration at the site of inoculation, resembling a herpes lesion. Ulcer heals on its own in a few days.
- Secondary stage: Developing weeks to months later, symptoms include inguinal lymphadenopathy, buboes, and fever. Buboes can become fluctuant and drain.
- Tertiary stage: May occur months to years later, characterized by inflammatory strictures in the rectum, urethra, or vagina.
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Description
Dive into the fascinating world of Chlamydia with this quiz. Learn about their classification, morphological characteristics, and unique life cycle. Understand their role as obligate intracellular pathogens and their significance in infectious diseases.
