n Pyogenic Cocci: The Gram’s positive Cocci: 1-Staphylococci : 2-Streptococcus : Staphylococci : is a Gram positive Cocci, one micrometer in diameter, arranged in clusters, non spore formers, and non-motile . Staphylococcus aureus species are capsulated.
n. Pyogenic Cocci : The Gram’s positive Cocci : 1- Staphylococci : 2- Streptococcus : Staphylococci : is a Gram positive Cocci , one micrometer in diameter, arranged in clusters, non spore formers, and non-motile. Staphylococcus aureus species are capsulated. n. - PowerPoint PPT Presentation
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Pyogenic Cocci: The Gram’s positive Cocci:1-Staphylococci :2-Streptococcus :
Staphylococci : is a Gram positive Cocci, one micrometer in diameter, arranged in clusters, non spore formers, and non-motile.
Staphylococcus aureus species are capsulated.
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Staphylococcus species are facultative anaerobic bacteria .All species grow best on nutrient agar and blood agar.Mannitol salt agar is a selective media for Staphylococcus species.It can grow at a temperature range of 15-45 C, and NaCl concentration as high as 15%.
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Clinical significance of Staphylococcus aureus :1-Localized skin infections.
2-Acute endocarditis.
3-Pneumonia.
4-Septicemia. Staphylococcus impetigo
5-Food poisoning:(Food born intoxication).
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Streptococcus: Gram positive cocci ,occur in pairs and in short chains.None-motile, none- spore formers, some strains are capsulated. Strict anaerobes and facultative anaerobes.
Gram positive Streptococci: in chains.
Classification of Streptococcus species:Streptococcus species are classified according to hemolytic
activity .
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Beta-Hemolytic: Alpha Hemolytic
Streptococcus pyogenes Streptococcus pneumoniae
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Clinical significance of Streptococcus pyogenes :1-Acute pharyngitis and tonsilitis.
2-Impetigo and deep skin infection .
3 -Acute Rheumatic fever. Due to the bacteria M protein .
Streptococcus tonsilitis
4-Acute nephritis. Due to antibodies interaction with glomerulus .
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The Gram negative Diplococci:Neissereiae meningitidisNeissereiae gonorrhoeae
Gram negative cocci , Kidney-shaped, occur in pairs, in clinical specimens: present inside the polymorphonuclear cells.
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They grow best on Thayer-Martin Medium; Chocolate agar
supplemented by vancomycin and nystatin .
Both factor X and V (hemoglobin, NAD) are required for
Bacillus cereus :Enterotoxins cause food poisoning.
The Gram positive spore-forming anaerobic bacilli:
The genus Clostridium:Gram-positive spore-forming, anaerobic large bacilli .
Clostridium tetani species forms terminal spores, while sub-
terminal or central oval spores are produced by Clostridium
perfringens.
Microscopic Drum-stick Appearance of
Clostridium tetani
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All Clostridium species are obligatory anaerobic.On blood agar, Clostridium perfringens species produce zone of complete hemolysis surrounded by wider zone of incomplete hemolysis.Clostridium tetani colonies show beta hemolytic activity.
Clinical significance: Clostridium perfringens :
1-Myonecrosis (gas gangrene) : Caused by alpha toxin which damages host and blood cells.
2-Food poisoning: caused by Enterotoxin.
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Clostridium botulinum : -Botulism :
Food poisoning, lead to progressive striated muscle paralysis.
Clostridium difficile :-Diarrhea, and pseudomembranous colitis due to long-term
antibiotic therapy .
The Non-spore former acid-fast Bacilli:
The genus Mycobacterium:The Mycobacteria are acid-fast, non-motile, non-spore forming rods. The microbe can not be stained well by Gram’s stain due to the presence of waxy capsule.
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Mycobacterium is best demonstrated by Ziehl -Neelsen staining technique; the microbes appear as thin pink rods arranged singly or in groups. Once stained, they resist decolorization with 2% H2SO4 and 95% alcohol (Acid-fast, Alcohol fast).
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Mycobacterium is strict aerobic, grows very slowly (2-4 weeks) on
Lowenstein-Jensen medium; produce dry creamy colored colonies.
Culture characteristics of Tubercle bacilli on Lowenstein Jensen medium .
The Non-spore Non-acid fast bacilli: The genus Corynebacterium:
Gram positive pleomorphic long rods with swollen one end (club-shaped).They lie in small groups joined at angles to each other giving characteristic Chinese-letter arrangement
Corynebacterium bacilli arranged as Chinese-letter.Note the metachromatic Granules.
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Aerobe or facultative anaerobe; grows rapidly on Loeffler’s
serum at 37 C giving opaque white colonies within 4-12 hours.
On blood tellurite; the organism reduces
tellurite and produce grey-black colonies
a Clinical significance of Corynebacterium:1-Upper respiratory tract: Diphtheria.