Download 1:Gram-positive bacteria

Chlamydiae, Rickettsiae and Mycoplasmas
a miscellaneous group with
Properties common to bacteria & viruses they
differ from each other .
visible with light microscopy
free growth (only mycoplasma)
both DNA ,RNA present
Rigid cell wall (except mycoplasma)
suscptible to tetracyclin
reproduce by binary fission
Chlamydia spp.
 Related to Gram –ve bacteria
 BUT unlike bacteria ,obligate intracellular




growth
Larger than viruses (visible by light
microscopy)
Both DNA &RNA are present.
Complex growth cycle
Sensitive : tetrac., erythrom., sulphanomides
3 species
 Ch. Trachomatis (many diseases)
 Ch. Pneumoniae (acute respiratory tract
infection)
 Ch.psittaci (psittacosis in birds ,also known
as psittacosis in human)
chlamydia
Chlamydia trachomatis cause
1-Ocular infection:
 Neonatal conjuctivitis,keratoconjuctivitis
,blindness(trachoma)in the developing word.
2-Genital infection-non specific urethritis(the
most common sexually transmitted disease in
the UK.
3-Pneumonia-in neonates
Culture and diagnosis
 Tissue culture ……Why???
 Serology (complement fixation test) .
 Fluorescent Ab staining of smears from the
Lesion.
Antibiotic sensitivity:
Tetracyclin is effective for all Chlamydia l
infection.
Rickettsia
 1-Pleomorphic m.o.
 2-Coccobacilli
 3-Smaller than bacteria, but resembling them
structurally & metabolically including cell wall
formation ,visible by L.M.(by Giemsa stain)
 4-They like Chlamydia & viru ses (Obligate
intracellular parasites ,which replicate by
binary fission.
 5-Have cell wall(resemble gram –ve)
 6-Like viruses :obligate intra cellular parasite
 7-The best –known human rickettsial disease is
 8-Sensitive to tetracycline and
chloramphenicol
 9-Infect birds & mammals
 10-Transmitted to man via bites of
arthropods
There are 2 genera within the Rickettsieae:
1-Rckettsia
2-Coxiella
Rickettsial diseases include:
1-Typhus :Acute febrile illness ,transmitted
by rat flea
2-Spotted fevers-Rocky Mountain spotted
fever
Coxiella

Coxiella burnetii An organism closely
resembling Rickettsiae ,causes Q fever
(atyphus like illness)
Q fever usually present as the non bacterial
pneumonia ,the lesions may be seen in the
brain ,heart with resultant endocarditis.
Culture & identification
 Guinea inoculation
 Serology reaction
General Characteristics
of Mycoplasma
$ Are the smallest prokaryotes capable of binary
fission.
$Pleomorphic morphologic forms (as they lack p.G.
cell wall)
$Wall less bacteria ,no P.G.cell wall but bound by
plasma memb.consisting of lipids and sterols,hence
they are highly pleomorphic
Bacteria with No cell wall
Outer membrane
No lipopolysaccharide layer (endotoxin)
Weak gram negative stain
Normal flora of upper respiratory tract
Pleomorphism of mycoplasma
Mycoplasma species
Mycoplasma pneumoniae causes:
• Atypical pneumonia
•Mucocutaneous eruptions ,including the oral
mucosa
•Haemolytic anaemia
Mucocutaneous eruptions:
M.Pneumonia may cause skin rashes
&ulcerations of both the oral & vaginal mucosa
Oral Mycoplasma
M.buccale
M.oral
M.salivarium
Have been isolated from saliva,oral mucosa &
dental plaque .
But their significance in either health or disease is
unclear.
Culture and identification:
Can be cultured in special media (slow ,about 10
days)
The colony have a characteristics (fried –
egg)appearance.
Serology is useful as the culture result s are
delayed.
Immunofluorescence of colonies transferred to
glass slides(as they do not take gram stain well)
Complement fixation test for M.pneumoniae
Antibodies.
FRIED EGG APPEARANCE
slow growth colonies