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Streptococcus sp. Lecture content. Basic characteristics Classification Grouping of species Pathogenesis Lab diagnosis. Scientific classification. Kingdom – Bacteria Phylum - Firmicutes Class – Bacili Order – Lactobacillales Family – Streptococcaceae Genus - Streptococcus

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Streptococcus sp.

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Streptococcus sp l.jpg

Streptococcus sp.

Lecture content l.jpg

Lecture content

  • Basic characteristics

  • Classification

  • Grouping of species

  • Pathogenesis

  • Lab diagnosis

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Scientific classification

  • Kingdom – Bacteria

  • Phylum - Firmicutes

  • Class – Bacili

  • Order – Lactobacillales

  • Family – Streptococcaceae

  • Genus - Streptococcus

  • Species – 22 sp.

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Basic characteristics

  • 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

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β hemolysis

Colonies surrounded with a zone complete of haemolysis (decolorize of hemoglobin)

More marked when incubate anaerobically

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Alpha hemolysis

  • Surrounded by an area of partial haemolysis

  • Green-brown colour (reduced haemoglobin)

  • Consist of pneumococci and viridans group( alpha hemolytic and no Lancerfield antigens

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S.pyogenes (Group A)

  • Acute sore throat

  • Scarlet fever

  • Ear infections

  • Peurperal sepsis

  • Septicemia and occasionally endocarditis

  • Skin infection such as celulitis and impetigo

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Post-streptococcal disease

From the implication of pathogenesis, it will leads to a serious stage of diseases:

  • Acute glomerulonephritis

  • Rheumatic fever

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Enzymes & toxin production

By S. pyogenes

  • Streptolysin O

  • Streptolysin S

  • Streptokinase (cause fibrinolysis)

  • Hyarulonidase

  • DNAses

  • DPNAse

  • Erythrogenic toxin

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Other species

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


  • Endocarditis

  • Dental caries

  • Brain abscess

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Laboratory diagnosis

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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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S. pyogenes

  • 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

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  • Optochin resistant but S.pneumoniaeis sensitive

  • Beta hemolysis in BA

  • In serum starch agar, it produces orange pigment

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Biochemical test

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Take a break…10 minutes

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  • Scientific classification

  • Introduction

  • Basic characteristics

  • Pathogenesis

  • Laboratory diagnosis

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Scientific classification

  • Kingdom: BacteriaPhylum: ProteobacteriaClass: Beta ProteobacteriaOrder: NeisserialesFamily: NeisseriaceaeGenus: NeisseriaSpecies: 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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Basic characteristics

  • 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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Laboratory diagnosis

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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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Biochemical test

  • Further testing to differentiate the species includes testing for oxidase (all clinically relevant Neisseria show a positive reaction) and the carbohydratesmaltose, 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

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Scientific classification

Phylum: FirmicutesClass: BacilliOrder: LactobacillalesFamily: LactobacillaceaeGenus: Lactobacillus

Species: 40++

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Basic characteristics

  • genus of Gram-positive

  • Bacilus in shape

  • facultative anaerobic or microaerophilicbacteria.

  • 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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Benefits for food production

  • 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 flourmedium.

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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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Laboratory test

  • Catalase negative

  • Not often isolated

  • Non motile bacteria

  • Non-sporing

  • Facultative anaerobes

  • Grow best in acid environment

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The end

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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)

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State all group of gram positive and gram negative bacteria.

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