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Basic characteristics
Classification
Grouping of species
Pathogenesis
Lab diagnosis
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Kingdom – Bacteria
Phylum - Firmicutes
Class – Bacili
Order – Lactobacillales
Family – Streptococcaceae
Genus - Streptococcus
Species – 22 sp.
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Gram-positive
Lactic acid bacteria group
Spherical
Grow in chain (twisted) or pairs
Mostly are facultative anaerobes
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Available in food such as
Emmentaler (Swiss) cheese
Normal flora of the mouth,
skin, intestine and upper
respiratory tract of
humans
Beta
hemolysis
Alpha
hemolysis
• Lancerfield serotyping
• Based on carbohydrates
in the bacterial cell wall
• Group A – V (exp, I and J)
• Viridans groups
• S.pneumoniae separated
group
β hemolysis
Colonies
surrounded with
a zone complete
of haemolysis
(decolorize of
hemoglobin)
More marked
when incubate
anaerobically
Surrounded
by an area of partial
haemolysis
Green-brown colour (reduced
haemoglobin)
Consist of pneumococci and viridans
group( alpha hemolytic and no
Lancerfield antigens
S.pyogenes (Group A)
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Acute sore throat
Scarlet fever
Ear infections
Peurperal sepsis
Septicemia and occasionally endocarditis
Skin infection such as celulitis and impetigo
From the implication of pathogenesis, it will
leads to a serious stage of diseases:
 Acute glomerulonephritis
 Rheumatic fever
By S. pyogenes
 Streptolysin O
 Streptolysin S
 Streptokinase (cause fibrinolysis)
 Hyarulonidase
 DNAses
 DPNAse
 Erythrogenic toxin
S.Agalactiae (Group B)
 Neonatal septicaemia, pneumoniae, meningitis
 Septic abortion and peurperal sepsis
Enterococci (Group D)
 Urinary tract infection
 Infections of ulcer and wounds
 Endocarditis and meningitis
Viridans
 Endocarditis
 Dental caries
 Brain abscess
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Gram positive (purple)
Non-motile
Long chains
Sometimes in pair
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Aerobically and anaerobically
Temperature between (22 – 42o C)
And enterococci are between (15 – 45o C)
On BA, colony usually less than 1 mm in
diameter
Grey – white or colourless
Dry / shiny, irregular outline
Most of the pathogenic streptococcus
producing hemolysins
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Produce beta hemolysis
Sensitive to bacitracin (can’t rely 100% to it,
coz not only group A sensitive to it) but for
viridans it is resistance towards bacitracin
A selective BA containing crystal violet was
suggested
Does not grow in MacConkey agar
 Optochin resistant
but S.pneumoniae is
sensitive
 Beta hemolysis in BA
 In serum starch agar, it produces orange
pigment
Species
Catalase Bacitracin
Optochin
Litmus
Milk
CAMP
S.pyogenes
-
+
-
-
-
S. agalactiae
-
-
-
-
+
Enterococci
-
-
-
+
-
Viridans streptococci
-
-
-
-
-
Pneumococci
-
-
+
-
-
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Scientific classification
Introduction
Basic characteristics
Pathogenesis
Laboratory diagnosis
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Kingdom: Bacteria
Phylum: Proteobacteria
Class: Beta Proteobacteria
Order: Neisseriales
Family: Neisseriaceae
Genus: Neisseria
Species: N. gonorrhoeae
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also known as gonococci (plural), or
gonococcus (singular),
Gram negative
Sexually transmitted diseases
These cocci are facultatively intracellular and
typically appear in pairs (diplococci), in the
shape of coffee beans.
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non-motile and possess a type IV pilus to
adhere to surfaces.
The type IV pilus operates mechanistically
similar to a grappling hook.
The pilus extends from the pole of the cell
and attaches to a substrate which signals the
pilus to retract, dragging the cell forward.
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Infection of the genitals can result in a
purulent (or pus-like) discharge from the
genitals which may be foul smelling.
Symptoms may include inflammation,
redness, swelling, dysuria and a burning
sensation during urination.
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Infection of the genitals in females with N.
gonorrhoeae can result in pelvic
inflammatory disease if left untreated, which
can result in infertility.
Pelvic inflammatory disease results if N.
gonorrhoeae travels into the pelvic
peritoneum (cause conjunctivitis, pharyngitis,
proctitis or urethritis, prostatitis and orchitis.
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Temp 35 -37 degree celcius
The selective media is Modified New York
City (MNYC)
usually isolated on Thayer-Martin agar—an
agar plate containing antibiotics
(Vancomycin, Colistin, Nystatin, and SXT)
nutrients that facilitate the growth of
Neisseria species while inhibiting the growth
of contaminating bacteria and fungi.
Bacteria should be protected from sunlight
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Further testing to differentiate the species
includes testing for oxidase (all clinically
relevant Neisseria show a positive reaction)
and the carbohydrates maltose, sucrose, and
glucose test in which N. gonorrhoeae will
only oxidize (that is, utilize) the glucose.
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Scientific classification
Basic characteristics
Food production
Laboratory diagnosis
Phylum: Firmicutes
Class: Bacilli
Order: Lactobacillales
Family: Lactobacillaceae
Genus: Lactobacillus
Species: 40++
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genus of Gram-positive
Bacilus in shape
facultative anaerobic or microaerophilic
bacteria.
a major part of the lactic acid bacteria group,
named as such because most of its members
convert lactose and other sugars to lactic
acid.
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They are common and usually benign. In
humans they are present in the vagina[2] and the
gastrointestinal tract, where they are symbiotic
and make up a small portion of the gut flora.
Many species are prominent in decaying plant
material. The production of lactic acid makes its
environment acidic, which inhibits the growth
of some harmful bacteria. Several members of
the genus have had their genome sequenced
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Some Lactobacillus species are used
industrially for the production of yogurt,
cheese, sauerkraut, pickles, beer, wine, cider,
kimchi, chocolate, and other fermented foods,
as well as animal feeds, such as silage.
Sourdough bread is made using a "starter
culture," which is a symbiotic culture of yeast
and lactic acid bacteria growing in a water
and flour medium.
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Lactobacilli, especially L. casei and L. brevis,
are some of the most common beer spoilage
organisms. The species operate by lowering
the pH of the fermenting substance by
creating the lactic acid, neutralising it to the
desired extent.
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Catalase negative
Not often isolated
Non motile bacteria
Non-sporing
Facultative anaerobes
Grow best in acid environment
Explain what happens in the following biochemical
tests:
i) Indole test
ii) Methyl red test
(8 marks)
b) Write the scientific name of a bacterium that gave
positive results for both tests.
(2 marks)
State all group of gram positive and gram negative bacteria.