Medical Bacteriology - Chlamydia PDF

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PunctualJasper9346

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University of Bologna

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Medical Bacteriology Chlamydia Microbiology Infectious Diseases

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A detailed study guide covering Medical Bacteriology and the specifics of Chlamydia. The document features detailed information on structure, life cycle, pathogenesis, and diagnostic methods. It also provides an overview of treatment protocols and the relevant medical aspects related to Chlamydia.

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Medical Bacteriology Chlamydia CHLAMYDIA Chlamydia are Gram negative nonmotile bacteria. They are coccoid in morphology and are very small, usually about 350nm in diameter. They posses fundamental peculiarities in terms of: o STRUCTURE: they have a pepti...

Medical Bacteriology Chlamydia CHLAMYDIA Chlamydia are Gram negative nonmotile bacteria. They are coccoid in morphology and are very small, usually about 350nm in diameter. They posses fundamental peculiarities in terms of: o STRUCTURE: they have a peptidoglycan-free cell wall (Gram neg) o ENERGY REQUIREMENTS: they have no cytochromes and flavoproteins → obligate intracellular parasites o UNIQUE DEVELOPMENTAL CYCLE: they present as metabolically inactive infectious form (elementary body) and metabolically active noninfectious form (reticular body) Structure o Absence of peptidoglycan in the cell wall (lack of sensitivity to some antimicrobials, including β-lactams) o Peptidoglycan is replaced by a layer of cysteine-rich proteins (CRP) o Outer membrane contains LPS and MOMP proteins (major outer membrane proteins), which are species and type-specific antigens (anti-MOMP antibodies are neutralizing) o Based on the antigenic differences of the MOMP protein (or of the omp1 gene sequence), Chlamydia are distinguished in different serotypes/genotypes/serovars with different pathogenicity spectrum LPS Outer membrane CRP Protein layer Plasma membrane Structure and mechanisms of pathogenesis Dimorphic life cycle, with alternation of two biological forms: elementary body (EB) and reticulate body (RB) Chlamydia trachomatis C. trachomatis infection is restricted to humans. The species responsible for human disease are subdivided into biovars (trachoma and lymphogranuloma venereum) and serovars based on MOMP proteins. Specific serovars are associated with specific diseases. Trachoma → chronic keratoconjunctivitis o the conjunctivae become scarred as the disease progresses, causing the patient's eyelids to turn inward o the turned-in eyelashes abrade the cornea, eventually resulting in corneal ulceration, scarring, pannus formation (invasion of vessels into the cornea), and loss of vision Chlamydia trachomatis Urogenital tract infection o urethritis in men (urethral discharge and dysuria) o cervicitis, endometritis, urethritis, salpingitis in women o as a severe complication: chronic pelvic inflammatory disease (PID) in women that can lead to infertility. If the infected woman is pregnant, the newborn can be infected by passing through the birth canal and develop neonatal conjunctivitis (ophtalmia neonatorum) or infant pneumonia Lymphogranuloma venereum (LGV) o primary lesion appears at the site of infection (penis glans, scrotum, cervix, vulva) o second stage of infection is characterized by an inflammation and swelling of the lymph nodes draining the site of initial infection o the inguinal nodes are most commonly involved, becoming painful, fluctuant that gradually enlarge and can rupture Laboratory diagnosis of C. trachomatis infection CULTURE Cells that are sensitive and permissive to bacterial infection (HeLa) are inoculated with conjunctival, urethral, ​vaginal swabs. Then, detection of chlamydial antigen is performed with immunological methods NUCLEIC ACID–BASED TESTS Detection of chlamydia genome by PCR on urine or urogenital/extra-genital swabs SEROLOGY Detection of IgM, IgG and IgA in serum samples with ELISA Therapy of C. trachomatis infection o Chlamydia is not sensitive to drugs that act on peptidoglycan synthesis such as β-lactams o First line drugs are antibiotics acting on protein synthesis such as macrolides and tetracyclines o No vaccine available

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