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MYCOPLASMAS & CELL-WA
DEFECTIVE BACTERIA
MICROBIOLOGY LECTURE SERIES
LUZ GREGORIA LAZO-VELASCO, MD
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Mycoplasmas
MOLLICUTES cell wall-free bacteria; 200 known species (16 of human
Mycoplasma pneumoniae pneumonia, joint & other infections
Mycoplasma hominis postpartum fever
Ureaplasma urealyticum nongonococcal urethritis in men; lung diseaspremature infants of low birth weight
Mycoplasma genitalium urethral and other infections; smallest genom
Other members are pathogens of the respiratory and urogenital tracts ahumans and animals
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Mycoplasmas
Smallest organisms that can be free-living in nature and self-replicating omedia
Characteristics:
1. small mycoplasmas are 125-250 nm in size
2. highly pleomorphic (lack rigid cell wall; bounded by a triple-laye
membrane that contains a sterol (mycoplasmas require thof serum or cholesterol to the medium to produce sterols fo
3. completely resistant to penicillin (lack cell wall structures at whiacts; inhibited by tetracycline or erythromycin
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Mycoplasmas
Smallest organisms that can be free-living in nature and self-replicating omedia
Characteristics:
4. can reproduce in cell-free media; on agar, the center of the whocharacteristically embedded beneath the surface
5. growth inhibited by specific antibody
6. have an affinity to mammalian membranes
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Mycoplasmas
MORPHOLOGY & IDENTIFICATION
A. Typical Organisms
growth in fluid media gives rise to many different forms
growth on solid media consists principally of protoplasmic indefinite shape that are easily distorted
50-300 nm in diameter
B. Culture
media with serum, a metabolic substrate (glucose or urea), (yeast extract)
incubation at 37oC for 48-96 hours
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Mycoplasmas
MORPHOLOGY & IDENTIFICATION
B. Culture
Giemsa stains of centrifuged sediment show characteristic structures
subculture on appropriate solid media yields minute coloniafter 2-6 days on biphasic (broth over agar) and agar mediu
in a Petri dish, colonies are round, with a granular sudark center typically buried in the agar
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Mycoplasmas
MORPHOLOGY & IDENTIFICATION
C. Growth Characteristics
grow on cell-free media that contain lipoprotein & sterol
use glucose & urea (ureaplasmas) as source of energy
some produce peroxidases and hemolyze RBCs
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Mycoplasmas
ANTIGENIC STRUCTURE
species are classified by biochemical and serologic features
complement fixation (CF) antigens of mycoplasmas are glycolipids
antigens for ELISA tests are proteins
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Mycoplasmas
PATHOGENESIS
flasklike or filamentous shapes, specialized polar tip structures that madherence to host cells
interactive proteins - adhesins (P1 adhesin of M pneumoniae , MgPa agenitalium)
adherence-accessory proteins
attach to the surfaces of ciliated and nonciliated cells, probably througcell sialoglycoconjugates and sulphated glycolipids
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Mycoplasmas
DIAGNOSTIC LABORATORY TESTS
A. Specimens: throat swabs, sputum, inflammatory exudates, respiraor genital secretions
B. Microscopic Examination: direct examination useless
C. Cultures: broth & special solid media
agar media incubated at 37oC with 5-10% CO2
M hominis- fried-egg appearance on agar
Ureaplasma sp- growth signalled by color change indicatingurea
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Mycoplasmas
DIAGNOSTIC LABORATORY TESTS
D. Serology CF tests, HI tests, indirect fluorescence, EIAs
E. Nucleic acid Amplification Tests
TREATMENT TETRACYCLINES, ERYTHROMYCINS
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Mycoplasma pneumoniaeATYPICAL PNEUMONIAS
PATHOGENESIS
Transmitted from person to person by infected RESPIRATORY SECRETIO
Infection initiated by attachment of the organisms tip to a receptor onof respiratory epithelial cells; mediated by a specific adhesion protedifferentiated terminal structure of the organism
CLINICAL FINDINGS
generally mild
asymptomatic infection to serious pneumonitis, with occasional neurohematologic (hemolytic anemia) involvement & a variety of possib
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Mycoplasma pneumoniaeATYPICAL PNEUMONIAS
CLINICAL FINDINGS
incubation period: 1-3 weeks
insidious onset
malaise, fever, headache, sore throat, cough (initially non-productive,
paroxysmal, later with blood-streaked sputum and chest pain)early: patient appears moderately ill, physical signs of pulmonary consoften negligible compared with the striking consolidation seen on radi
later: infiltration at its peak, illness may be severe
resolution of pulmonary infiltration and clinical improvement occur slo
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Mycoplasma pneumoniaeATYPICAL PNEUMONIAS
CLINICAL FINDINGS
most common pathologic findings: interstitial with peribronchial pneunecrotizing bronchiolitis
Common causes of community-acquired bacterial pneumonia in addMycoplasma pneumoniae:
Streptococcus pneumoniae Haemophilus influenzae
Legionella pneumophila Chlamydia pneumoniae
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Mycoplasma pneumoniaeATYPICAL PNEUMONIAS
LABORATORY TESTS
diagnosis of M pneumoniae pneumonia is largely made by the clinicalthe syndrome
WBC count slightly elevated
sputum Gram stain does not suggest some other bacterial pathogenCulture highly specialized test; almost never done to diagnose M pn
infection
Cold hemagglutinins for group O human erythrocytes appear in 50% opatients, in rising titer, maximum reached in the 3rd or 4th week aft(>1:64)
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Mycoplasma pneumoniaeATYPICAL PNEUMONIAS
LABORATORY TESTS
rise in specific antibodies to M pneumoniae demonstrable by CF tests convalescent phase sera necessary to demonstrate a 4-fold rise in tantibodies
EIA detect IgM and IgG can be highly sensitive and specific; more se
tests
PCR assays of specimens from throat swabs or other clinical material cdiagnostic
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Mycoplasma pneumoniaeATYPICAL PNEUMONIAS
TREATMENT
Tetracyclines, macrolides, fluoroquinolones can produce clinical improdo not eradicate M pneumoniae
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Mycoplasma hominis
Strongly associated with infections of the uterine tubes (salpingitis) and abscesses
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Ureaplasma urealyticum
Requires 10% urea for growth
Causes nongonococcal, nonchlamydial urethritis in men (biovar 2)
Common in female genital tract
Associated with lung disease in premature LBW infants who acquired theduring birth