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31 Cards in this Set
- Front
- Back
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Chlamydia Taxonomy
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Order = Chlamydiales
Family = Chlamydiaceae Genus = Chlamydia Species -pecorum -pneumoniae -psittaci -trachomatis |
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New Classification of Chlamydia
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Proposed based on recent analysis of 16s and 23s rRNA gene sequences
Two genera -Chlamydia C. trachomatis -Chlamydophila C. trachomatis C. psittaci C. pecorum |
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Chlamydia of clinical significance
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C. psittaci
C. trachomatis C. pneumoniae |
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General characteristics of Chlamydia
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Obligate intracellular pathogens
Metabolically deficient -Can not synthesize ATP Possess DNA and RNA Multiply via binary fission Susceptible to several antibiotics Small, variable shape (generally rounded) Unusual replicative cycle |
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Replicative cycle: Elementary body
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small, extraceullular
infectious stage Enters via endocytosis Resides within phagosome Metabolically active Reorganize within one hour of infection into reticulate body |
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Replicative cycle: Reticulate body
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Larger, intracellular, non-infectious
Can not survive outside of cell Uses host ATP to divide After 24 – 72 hours, becomes elementary body Replicates within cytoplasm of host cells Intracellular inclusions can be seen by light microscope Between 48-72 hours, cell ruptures and infective elementary bodies are released |
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Virulence Factors of Chlamydia
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Not completely known
Produce heat-labile toxins Compete with host cell for nutrients Causes tissue damage and cell death |
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Chlamydia trachomatis
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Divided into 3 biovars
-Trachoma -Lymphogranuloma venereum -Mouse pneumonitis Biovars are subdivided into serovars Cause eye Infections (two forms): -Trachoma -Inclusion conjunctivitis |
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Trachoma
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Caused by serotypes A, B, Ba and C
Chronic keratoconjunctivitis More common in developing countries Usually infected in infancy or early childhood Transmission through droplet, hands, fomites, and flies |
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Trachoma Symptoms
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Acute conjuncitivitis followed by severe
corneal scarring Blindness often occurs in 15 – 20 years if untreated Persistence and reinfections occur Major pathology caused by inflammatory response of host The leading cause of preventable blindness in developing countries |
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Inclusion conjunctivitis
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Acute inflammation of conjunctiva seen in adults
and infants Common in populations with high numbers of Chlamydia genital infections Neonatal form results from direct contact with infected cervical secretions Occurs 2 – 3 days after birth -Presents as acute, copious, mucopurulent eye discharge -Symptoms can resolve without treatment Adult form associated with genital disease |
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Genital infection
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Most frequent cause of STD in U.S.
4 million cases/year Similar to N. gonorrhoeae -Males – urethritis and epididymitis -Females – cervicitis, salpingitis, and urethral syndromes Causes 40% of nongonococcal urethritis in men One-half of infants born to mothers excreting C. trachomatis during labor develop chlamydial diseases within first year |
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Lymphogranuloma venereum (LGV)
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Distinct venereal disease from C. trachomatis
One of 5 common STD’s -Gonorrhoeae, syphilis, herpes, chancroid Uncommon infection in U.S. Two stages Stage one = genital lesion -Small, painless genital ulcer Stage two = lymph adenitis -Marked swelling of inguinal lymph nodes -Fever, headache, and myalgia Systemic manifestations -Hepatitis -Pneumonitis -meningoencephalitis Diagnosis -Characteristic appearance |
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Chlamydophila (Chlamydia)
pneumoniae |
Worldwide distribution
Infections seen between 7 – 30 years of age Infections usually are mild to moderate Infections may be severe in elderly Associated with pneumonia, bronchitis, pharyngitis, sinusitis, and flu-like illness |
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Chlamydophila (Chlamydia)
psittaci |
Cause of psittacosis among psittacine birds
-Parrot fever Diagnosis -based on history of exposure to psittacines Serology -Fewer than 50 cases annually in U.S. |
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Treatment
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Antimicrobials
Tetracylcine Erythromycin Sulfonomides rifampin |
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Control
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Treat known cases
Prevent exposure |
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Isolation
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Most sensitive and specific method of diagnosis
Chlamydia grow well in yolk sac of embryonated hen eggs Most strains of C. psittaci grow well in tissue culture Inoculation of clinical samples directly into tissue culture cells (McCoy cells) Inclusions present in cells after several days -Iodine staining -immunofluorescent stain |
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Other diagnostics of chlamydia
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Direct staining
-Stain scrapings with Giemsa, iodine or immunofluorescence ELISA -Used to detect organisms in clinical samples Serology -Used to diagnose acute infections -Must show 4-fold titer increase -High IgM suggestive of recent infection |
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Mycoplasmataceae
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Urogenital infections
-Mycoplasma hominis -Ureaplasma urealyticum -Ureaplasma parvum Respiratory infections -M. pneumoniae |
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General characteristics of Mycoplasmataceae
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Smallest free living organisms
Pleomorphic -Coccoid, filamentous and large multinucleoid forms Lack cell walls -Bounded by a cell membrane -Do not gram stain -Stained with Giemsa Cell membrane contain sterols -Acquired from media or tissue |
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Growth requirements of Mycoplasmataceae
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Highly fastidious
Require enriched media -Peptones, yeast extract, and cholesterol Slow growth -Produce tiny colonies after several days Center of colony grows into agar -Inverted fried egg appearance Most are facultative -M. pneumoniae is an aerobe |
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Virulence Factors of Mycoplamsa pneumoniae
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Surface adhesin
-Protein P1 Affinity for neuraminic acid groups on RBCs Allows attachment of bacteria to respiratory epithelial cells |
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Clinical Manifestations of Mycoplasma pneumoniae
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Associated with several syndromes:
-Pharyngitis, tracheobronchitis, otitis media, pneumonitis and arthritis Accounts for 20% of pneumonias -Less severe than common bacterial pneumonia -Called primary atypical pneumonia -walking pneumonia -Insidious onset -Fever, headache, malaise, non-productive cough -Bacteria interfere with ciliary action -Leads to desquamation of mucosa, inflammation and exudate -Organisms shed in upper respiratory tract for 2 – 8 days before symptoms begin -Continue for 14 weeks after infection |
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Epidemiology of Mycoplasma pneumoniae
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Habitat
-Human respiratory tract -More common in summer -More prominent in temperate climates -Common between 5 – 15 years -Uncommon in small children (less than 6 months) Transmission -droplet Prevention -None at the moment Treatment -Erythromycin and tetracycline |
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Mycoplasma hominis Clinical Manifestations
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Postabortal or postpartum fever
-Isolated from blood Self-limiting -Antimicrobial therapy may decrease duration of fever Pelvic inflammatory disease associated with infection of Fallopian tubes |
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Epidemiology of M. hominis
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Habitat
-Genital tract of sexually active men and women -Rarely found in children Transmission -Endogenous -Sexual contact Prevention -None known Treatment -tetracycline |
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Ureaplasma urealyticum
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nongonococcal, nonchlamydial urethritis in men
Chorioamnionitis and postpartum fever in women |
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Staining and culture
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Morphology and staining
-Direct staining of clinical material not useful (do not stain well) Culture characteristics -Performed in reference labs -Isolation on special media -Mycoplasma agar -Some strains grow on BAP -Non-hemolytic, pinpoint colonies |
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Mycoplasma Culture
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Grows slowly
More than one week required Colonies usually very small Center of colony grows into the agar Must be differentiated from Ureaplasma -M. hominis demonstrates arginine breakdown -Ureaplasma urealyticum has urease activity |
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Serology
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Active disease
-4-fold rise in serum complement fixing antibody during disease Recent or concurrent infection -Single titer greater than 1:128 Demonstration of nonspecific anti-I antibody -Cold hemagglutinins -IgM Abs that react with RBC I antigen and cause agglutination at temperatures of 0 – 4 degrees Non-specific -Seen in adenovirus infection, mononucleosis, and other illnesses |
