MYCOPLASMAS

BY ASLAM MATANIAGROUP-3FACULTY OF MEDICINETSMU

INTRODUCTION

• Mycoplasmas are the smallest free-living organism in nature

• There are more than 200 known species in the class of Mollicutes

• At least 16 of these species are thought to be of human origin; others have been isolated from animals and plants

In humans, four species are of primary importance-

• Mycoplasma pneumoniae - respiratory• Mycoplasma hominis – urogenital;pelvic

inflammatory disease, postpartum fever• Mycoplasma urealyticum – urogenital

nongonococcal urethritis in men and is associated with lung disease in premature infants• Mycoplasma genitalium is closely related to

M pneumoniae and has been associated with urethral and other infection

CHARACTERSTICS• Prokaryotic microbes• Size of 125-250 nm• Lack of cell wall i.e

resistance to penicilin• Sterol-containing cell

membrane• Fastidious growth• Fried- egg or mulberry

colonies on agar

CULTURING• Mycoplasma can be

cultured on solid or liquid medium

• Growth optimally at 35 to 37 degree celcius

• Medium of growth should be enriched with 20% horse and human serum

• The colonies appears as fried egg appearance

GROWTH CHARACTERSTICS

• Mycoplasmas are unique in microbiology because of (1) their extremely small size and (2) their growth on complex but cellfree media

• Mycoplasmas pass through fi lters with 450-nm pore size and thus are comparable to chlamydiae or large viruses

• Many mycoplasmas use glucose as a source of energy; ureaplasmas require urea.

• Some human mycoplasmas produce peroxides and hemolyze red blood cells

ANTIGENIC STRUCTURE• The surface antigen

are glycolipids and proteins

• Glycolipids are identified by complement fixation

• Protein antigen are detected by ELISA method

MYCOPLASMA FOUND ON SURFACE OF MUCOUS MEMBRANE

• MOST OFTEN MYCOPLASMA FOUND ON MUCOUS MEMBRANE

• THEY CAN CAUSE CHRONIC INFLAMATORRY DISEASIS OF RESPIRTORY SYSTEM;UROGENITAL TRACT;AND JOINTS

• THE MOST COMMON HUMAN ILLNESS CAUSED BY MYCOPLASMA PNEUMONIAE WHICH IS RESPONSIBLE FOR 10-20% OF ALL PNEUMONIES in 5 to 20 years of age

M. hominis & Ureaplasma species• Most often associated with urogenital

tract infections• May be isolated from asymptomatic

individuals• Can be transmitted to the fetus at

delivery• Opportunistic pathogens

Pathogenesis• Many pathogenic mycoplasmas through droplets which

have flasklike or filamentous shapes and have specialized polar tip structures that mediate adherence to host cells

• These structures are a complex group of interactive proteins, adhesins and adherence-accessory proteins

• which influences the protein folding and binding and is important in the adherence to cells

• The mycoplasmas attach to the surfaces of ciliated and nonciliated cells, probably through the mucosal cell sialoglycoconjugates and sulfated glycolipids

• Finally these cause direct cytotoxicity through generation of hydrogen peroxide and superoxide radicals, cytolysis mediated by antigen–antibody reactions or by chemotaxis

CLINICAL FINDINGS OF PNEUMONIAE

• Generalized ache and pains• Fevers(102 degree)• Cough usually• Sore throat• Chills but not rigor• Nasal congestion• variety of possible skin lesion• infection ranges from asymptomatic infection to serious

pneumonitis, with occasional neurologic and hematologic (ie, hemolytic anemia) involvement

• The incubation period varies from 1 to 3 weeks• The onset is usually insidious• Other diseases possibly related to M pneumoniae

include erythema multiforme; central nervous system involvement, including meningitis, meningoencephalitis, and mono- and polyneuritis; myocarditis; pericarditis; arthritis; and pancreatitis

L Forms• Some bacteria readily give rise spontaneously to

variants that can replicate in the form of small filterable protoplasmic elements with defective or absent cell walls.

• These organisms, called L-forms, can also be formed by many species when cell wall synthesis is impaired by antibiotic treatment or high salt concentration.

L Forms vs Mycoplasma• contain a rigid cell wall, at least at

one stage of their life cycle • no sterols in their cytoplasmic

membrane.

GIT

支原体

血清抗体

• Specimens: throat swab, sputum, genital secretion, etc.

• Microscopy - This is not particularly useful because of the absence of a cell wall but it can be helpful in eliminating other possible pathogens.

• Culture - Sputum (usually scant) or throat washings must be sent to the laboratory in special transport medium. It may take 2 -3 weeks to get a positive identification. Culture is essential for a definitive diagnosis.

• Complement fixation test • Cold agglutinins - Approximately 34% - 68% of patients with

M. pneumoniae infection develop cold agglutinins. • ELISA - There is a new ELISA for IgM that has been used for

diagnosis of acute infection. • PCR

Diagnostic Laboratory Tests

• C. Serology-Antibodies develop in humans infected with mycoplasmas and can be demonstrated by several methodS

• D. Nucleic Acid Amplification Test-IN THIS primers and probes ARE USED

• Nucleic acid amplification tests (NAATs) are particularly useful for those organisms that are difficult to cultivate such as M pneumoniae and M genitalium and less useful for the more rapidly growing organisms

Treatment

•Tetracyclines and erythromycins are effective