MICROBIOLOGY PPT LECTURE NOTES | Karya Tulis Ilmiah

Mycoplasm
as

Mycoplasmas
A group of the smallest organisms that can be freeliving in nature,
Pass bacterial filter and also grow on laboratory
media. More than 80 species, belong to
Mycoplasmatales of Mollicute. 3 families can be
divided:
Mycoplasmataceae (require external cholesterol
during growth, contain Mycoplasma and Ureplasma
two genera);
Acholeplasmataceae (need not external cholesterol
during growth);
Spiroplasmataceae (can form spiral structure)

Morphology

Morphology

The smallest among prokaryotic microganisms with

circular dsDNA, usually 0.2-0.3um in size; lack of cell
wall;
Pleomorphic, spherical, short rod, filament; Gram
negative, but stained hardly, usually use Giemsa
stain.

They canassumemultipleshapes includinground,
pear shapedandevenfilamentous.

"fried egg" c olonial
morphology

BIOLOGICAL FEATURES
 Motility: Motile by possible release and



reattachment of terminal cell organelle; no
flagella present; possess a protein
attachment factor termed P1 that interacts

with a specific cellular receptor and allows
adherence to respiratory epithelium.
Respiration-Fermentation: Aerobesanaerobes.

Culture
Most aerobic; require 10%-20% human
or animal serum added to basic nutrient
media except Acholeplasma; typical
colony show fried egg apperance.
Many species are part of the normal flora
These organisms are a frequent cell culture contaminant

 The organisms have limited biosynthetic abilities;

they require cholesterol for their cell membrane and
can generate energy via the breakdown of arginine
 Ureaplasma requires urea to produce an
electrochemical gradient; urea is converted to
ammonia to produce ATP.

GENETICS
These bacteria have the smallest
genome of any prokaryote ( about 20%
that of E. coli) and the lowest G C
content (about 24%).

Resistance
Sensitive to osmotic presssure
resistant to thallium acetate 醋醋醋
醋 in a concentration of 1:10000
which can inhibit bacteria

Transmission
M. pneumoniae is spread  by close
contact via aerosolized droplets
and thus is most easily spread in
confined populations (e.g.,
families, schools, army barracks).

PATHOGENESIS

 Adherence factors - The P1 Adhesin localizes at
tips of the bacterial cells and binds to sialic
acid residues on host epithelial cells.The nature
of the adhesins in the other species has not
been established. Colonization of the
respiratory tract by M. pneumoniae results in
the cessation of ciliary movement.
 Toxic Metabolic Products
 Immunopathogenesis : most children are
infected from 2 - 5 years of age but disease is
most common in children 5-15 years of age.

M.pneumoniae
 primary atypical



pneumonia.
Incubation: 1-3 weeks
This disease can range

from subclinical to
bronchopneumonia, often
with a gradual onset and
mild to moderate severity. A
long convalescence (4-6
weeks) and several
possible complications
(CNS, cardiac) follow acute
disease.

Clinical Findings
 U. urealyticum, M.hominis, M.genitalium

are responsible for one form of
nongonococcal urethritis.
 M. hominis is associated with
pyelonephritis, pelvic inflammatory
disease and post-partum fevers.

HOST DEFENSES

 Host defenses are not well

characterized but probably involve both
humoral and cell mediated responses.

EPIDEMIOLOGY
 Mycoplasma affect a specific age distribution



(5-9 year olds) and represent 8-15% of all
pneumonias in school age children.
Disease occurs worldwide, is endemic in
some areas and is spread by close personal
contact (schools, families).
U. urealyticum is sexually acquired.

Antibody titers in
different age
groups. Antimycoplasma

pneumoniae
antibodies indicate
pneumonia caused
by this organism is
highest in the 5-15
year age group 

Acquired Pneumonia Caused by
Mycoplasma pneumoniae

Microbiological
diagnosis

GI T

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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

GI T

MI T

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Theantibodies of cold agglutinins arise before the
complement fixing antibodies and they decline faster

Transmissionelectronphotomicrographof ahamster trachearinginfectedwithM.
pneumoniae. Notetheorientationof themycoplasmasthroughtheir specializedtiplikeorganelle, whichpermits closeassociationwiththerespiratoryepithelium. M,
mycoplasma; m, microvillus; C, cilia.

CONTROL
Sanitary: Avoidance of contacts, if
possible.
Immunological: No single vaccine is

available. Natural resistance follows
infection.
Chemotherapeutic: Tetracycline,
erythromycin or chloramphenicol are
effective.

Mycoplasma and L Form Bacteria
MYCOPLASMA

L-FORM BACTERIA

No genetic relationship with
bacteria

Relate to their parent
bacteria ,sometimes can
revert

Cholesterol for their cell
membrane

No cholesterol for their cell
membrane

Stable in ordinary medium

Need hyperosmotic solution

Grow slowly, colony small
(diameter 0.1-0.3mm)

Colony larger(diameter 0.51.0mm)

Low turbidity in liquid
medium

High turbidity in liquid
medium ,may adhere to the
wall or bottom of the tube