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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