🔝بعض المواد الحافظة المستخدمة في حفظ عينة البراز
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🎙فقرة توعية
صورة مكبره تحت المجهر #لأبرة مستعملة بعد سحبها من الوريد توضح اثار #الدم عليها وهذا سبب عدم استخدامها مرة اخرى مهما كانت الاسباب
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🎙فقرة توعية
صورة مكبره تحت المجهر #لأبرة مستعملة بعد سحبها من الوريد توضح اثار #الدم عليها وهذا سبب عدم استخدامها مرة اخرى مهما كانت الاسباب
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📶Continued the previous article⏸

Specimens and infection control:
 
1⃣Label the specimens in case it carries risk to health care workers.
2⃣Don't send specimens to the laboratory without proper packing.
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Microscope

Different types of microscopes have developed in order to study different types of microorganisms and their ultra-structures.
 
🔬Light microscope: This is a compound microscope which has two systems of lenses for greater magnification:
1⃣Ocular eyepiece lens to look through.
2⃣Objective lens, close to the object.
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🔩Parts of light microscope:🔩
🔬Eyepiece Lens: the lens at the top that you look through, usually 10 x or 15x power.
 🔬Tube: Connects the eyepiece to the objective lenses.
 
🔬Arm: Supports the tube and connects it to the base.
 
🔬Base: Supports the microscope.
 
🔬Stage: Flat platform where slides are put.
 
🔬Revolving Nosepiece: Holds objective lenses and can be rotated.
 
🔬Objective Lenses: Consist of 4x, 10x, 40x and 100x powers.
When coupled with a 10x eyepiece lens, total magnification is 40x, 100x ,400x and 1000x.
When using oil immersion lens, oil is needed as it has the same refractive length of condenser lens to prevent scattering of light .
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🔬Condenser Lens: Focus the light onto the specimen.
It can be moved up and down.
It is set very close to the slide using oil immersion lens at 100x and moved further away at the lower powers.
🔬Diaphragm or Iris: It is used to vary the intensity of light that is projected upward into the slide.
 🔬Source of light: It could be lamp or day light.
🔬Mirror: Plane mirror is used on examination by oil immersion lens, concave mirror is used with high or low powers.
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🔬Light microscope is used to study the morphology of bacteria in stained smear using oil immersion lens and in unstained smear to detect motility of bacteria by hanging drop method using low and high powers.
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Definition
🔝Resolution is the power to distinguish between two close dots. A light microscope can only resolve two objects that are bigger than 250 nanometers.
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🎙Tomorrow we will complete
🔝IDENTIFICATION OF BACTERIA🔝
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📶IDENTIFICATION OF BACTERIA
 
🦠Morphology of bacterial cells is one of three forms:
⏺rod (bacillus)
⏺sphere (coccus) or spiral →spirilla and spirochetes
🈁Rods that are curved are called Vibrios
1-Bacilli may occur singly or form chains of cells.
2-Cocci may form chains (Streptococci) or grape-like clusters (Staphylococci).
3-Spiral shaped cells.                                                        
4-Branched bacteria e.g Actinomycetes
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Arrangement of bacteria is formed according to plane of cleavage it could be diplo or chain when  cleavage of bacterial cell occur in one plane, or grape like clusters when the cleavage of cells occur in all planes

Size of bacteria: A typical bacterial cell is about 0.2-1.2um, in diameter and its  length vary from 0.4-14um.
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🔬Microscopic examination in identification  is done by either
 
A- Unstained preparations
 

“Wet prep” or hanging drop method:is done to  detect motility of bacteria: The drop of  bacteria suspension is placed on a cover-slip and then this cover slip is carefully suspended on a slide having a concave cavity in its middle (cavity slide ).

Dark-ground illumination:is used for detection of fine organisms such as Treponema.
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B-Stained preparations: Morphology, arrangement, presence of capsules and staining characteristics provide preliminary diagnosis of causative agent of an infection. There are different types of stains:
1⃣Simple stain
2⃣Differential stain
2⃣Fluorescent stain
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▶️Simple stain: all cells, bacteria and tissue cells, take the same colour. Only one stain is used e.g Crystal violet, and basic  fuchsin. Methylene blue stain is especially useful for observing volutin granules in Corynebacteria
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📶Differential stain: Distinguish between different types of bacteria. Any differential stain is consisted of the main stain, a decolorizing agent and a counter stain .Two important differential stains are used in microbiology:
1⃣Gram-stain.  
2⃣Ziehl-Neelsen →Acid-fast stain
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1⃣Gram stain: It is the single most common and cheap staining technique used in identifying bacteria. It provides information about :
1⃣Morphology, that is their size, shape and arrangement.
2⃣Ability to retain crystal violet which classify them as Gram positive organisms or their failure to retain crystal violet and to be counterstained with dilute carbol fuchsin a pink stain which classify them as Gram negative organisms.
The differential staining of the two types of organisms is a reflection of differences in the basic composition of their cell wall or cell envelope.
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🎙اجباري التحــــــــــــــميل 👇
📘Microbiology Department Book P1.pdf
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