1. NEISSERIA, RICKETTSIA, CHLAMYDIA
S & FACULTATIVE ANAEROBIC GRAM
NEGATIVE RODS.
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2. 1).NEISSERIA
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3. What is Neisseria?
Neisseria is a large genus of commensal
bacteria.
They colonize the mucosal surfaces of
many animals.
Of the 11 species that colonize
humans, only two are pathogens.
• N. meningitidis
• N. gonorrhoeae
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4. Shape and Arrangement:All are diplococcal
bacteria
N. elongata and N.
weaveri,both occur
as rods
Present in pairs or
short chains.
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5. Characteristics:Gram-negative
aerobic
non-motile
non-spore-forming
bacteria
All species are oxidase
positive except N.
elongata which are
catalase positive.
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6. Culturing:Most species grow optimally
at temperatures ranging
between 35 to 37 C
Growth is usually stimulated
by carbon dioxide and
humidity.
They grow on chocolate agar
and Thayer-Martin agar.
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7. Importance:Pathogenic bacteria causes diseases,some which
are followings:N. gonorrhoeae causes gonorrhea disease.
N. meningitidis one of the most common
causes of bacterial meningitis.
N. meningitidis is causative agent of
septicaemia.
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8. 2).RICKETTSIA
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9. What is Rickettsia?
Rickettsia is a genus of gram-negative,
coccoid-shaped or rod shaped bacteria.
Classification:Classification
Rickettsia is divided into three catagories:Spotted fever group
Typhus group
Scrub typhus group
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10. History:Rickettsias are named after their discoverer, the American
pathologist Harold Taylor Ricketts, who died of typhus in
Mexico after confirming the infectious agent of that
rickettsial disease.
Shape and or rod-shaped bacteria
coccoid-shaped size:cocci (0.1 μm in diameter)
thread like rods (1–4 μm long)
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11. Characteristics:non-motile
non-spore forming
gram-negative bacteria
highly pleomorphic
they can produce ATP &
LPS
being obligate intracellular
parasites, they require a
living host cell to survive
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13. Culturing:Rickettsia cannot live in artificial nutrient environments
and is grown either in tissue or embryo cultures
(typically, chicken embryos are used).
Transmission:Transmitted by arthropod vectors
(lice, fleas, ticks, mites); thus, humans are accidental
hosts
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14. Mechanism of attack:invades the endothelial cells that line the
blood vessels
pathogen causes changes in the host cell
cytoskeleton that induces phagocytosis
they are able to avoid lysosomal fusion
oxidative burst by escaping from the
phagosome into the cytoplasm where they
multiply and spread
Causes many diseases
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16. Significance:R.prowazekii causes louse-borne
typhus, carried by lice.
Flea, or murine typhus is caused by R.
mooseri, is transmitted from rodents to
people by fleas.
African tick typhus, are transmitted by
ticks from animal hosts to people.
Mite-borne rickettsial infections include
rickettsialpox, caused by Rickettsia akari
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17. 3).CHLAMYDIAS
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18. What is Chlamydias?
Chlamydia is a genus of
bacteria that are obligate
intracellular parasites.
Chlamydia infections are the
most common bacterial
sexually transmitted diseases
in humans and are the leading
cause of infectious blindness
worldwide.
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19. Chlamydia species:The four Chlamydia species includes:1. Chlamydia trachomatis (a human pathogen)
2. Chlamydia suis (affects only swine)
3. Chlamydia pecorum (infects ruminants,koalas and
pigs)
4. Chlamydia muridarum (affects only mice and
hamsters).
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20. Characteristics:characteristics intermediate between bacteria
and viruses
obligate intracellular parasites of people and
animals
they are capable of independent reproduction
they do not synthesize ATP
life cycle lasts from 24 to 48 hours
aerobic
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21. Shape & size:coccoid or rod shape
size is about 0.3μm
Transmission:Chlamydia infection is a common sexually transmitted
infection (STI) in humans caused by the bacterium
Chlamydia trachomatis.
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22. Significance:Chlamydia trachomatis, and Chlamydophila, which
includes Chlamydophila pneumoniae and
Chlamydophila psittaci are susceptible to antibiotic
therapy.
Chlamydia is a common infectious cause of genital and
eye diseases in humans.
Study of chlamydia could open the way to new
treatments and the development of a vaccine for this
sexually transmitted disease.
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23. 4).FACULTATIVE ANAEROBIC
GRAM NEGATIVE RODS.
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24. What are Facultative anaerobes?
A facultative anaerobe is an organism that makes ATP
by aerobic respiration if oxygen is present, but is
capable of switching to fermentation or anaerobic
respiration if oxygen is absent.
Example:Enterobacteria.
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25. Characters of Enterobacteriaceae: All Enterobacteriaceae






Gram-negative rods
Ferment glucose with acid production
Reduce nitrates into nitrites
Oxidase negative
All enterobacteria have peritrichous flagella.
Facultative anaerobes
 Motile except Shigella and Klebsiella
 Non-capsulated except Klebsiella
 Non-fastidious
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27. Classification based on lactose fermentation:1.
•
•
Lactose fermenters:Escherichia coli
Klebsiella sp.
2.
•
•
Late lactose fermenters:Shigella sonnei
Para colons etc
3.
•
•
Non lactose fermenters:Salmonella
Shigella etc.
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28. Culturing:There are several selective and differential
media used to
isolate and distinguish between LF & LNF
The most important media are:
MacConkey agar
Eosin Methylene Blue (EMB) agar
Salmonella Shigella (SS) agar
Triple Sugar Iron (TSI) agar
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29. Growth of E.coli on nutrient agar,blood
agar,macConkey agar
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30. VIRULENCE FACTORS:-
Surface antigens: O and K
O antigen – somatic lipopolysaccharide surface O
antigen has endotoxic activity, protects the bacteria
from phagocytosis and bactericidal effects of
complement.
K antigen – affords protection against phagocytosis
and antibacterial factors in normal serum.
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31. Importance:Salmonella species that cause intestinal disease known
as salmonellosis
Klebsiella species, the causes of pneumonia,intestinal
disease, and other infections
Yersinia pestis, the cause of plague
Escherichia coli is also a member of this group,which
used for experimental work.
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32. Created by:Maria Mushtaq
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