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Diagnosis of Bacterial Infections
Diagnosis of Bacterial Infections
PRESENTER
Shakira Ghazanfar
PhD Scholar24-1-2013
ISLAMABAD
الرحمن اللة الرحمن بسم اللة بسمالرحيمالرحيم
Diagnosis of Diagnosis of Bacterial Bacterial
Infections Infections
TYPES OF SAMPLES TYPES OF SAMPLES EXAMINEDEXAMINED
•Animal Tissues – Blood samples
•Foods of animal origin
•Meat and meat products
•Milk and milk products
•Fish and fish products
•Water
•Animal feeds
Steps in diagnostic isolation Steps in diagnostic isolation and identification of bacteriaand identification of bacteria
Step 1. Samples of body fluids . blood, Step 1. Samples of body fluids . blood, urine, cerebrospinal fluid, Abscess)urine, cerebrospinal fluid, Abscess)
streaked on culture plates streaked on culture plates isolated colonies of bacteria appear isolated colonies of bacteria appear
after incubation for one to several after incubation for one to several days.days.
Observation of colonies (size, texture, Observation of colonies (size, texture, color, & hemolysis)color, & hemolysis)
differentiating characteristic- e.g differentiating characteristic- e.g oxygen requirement oxygen requirement
IdentificationIdentification
Colony CharacterColony Character Stainining ReactionStainining Reaction MorophologyMorophology Biochemical tests and serological Biochemical tests and serological
tests tests
-Commercial kits commonly used, e.g. -Commercial kits commonly used, e.g. API20API20
THE GRAM STAINTHE GRAM STAIN
A colony is dried on a slide A colony is dried on a slide Step 1. Staining with crystal violet.Step 1. Staining with crystal violet. Step 2. Fixation with iodine stabilizes Step 2. Fixation with iodine stabilizes
crystal violet staining. All bacteria crystal violet staining. All bacteria remain purple or blue.remain purple or blue.
Step 3. Extraction with alcohol or other Step 3. Extraction with alcohol or other solvent. Decolorizes some bacteria solvent. Decolorizes some bacteria (Gram negative) and not others (Gram (Gram negative) and not others (Gram positive).positive).
Step 4. Counterstaining with safraninStep 4. Counterstaining with safranin
Crystal violet
Gram's iodine
Decolorise with acetone
Counterstain withe.g. methyl red
Gram-positives appear purple
Gram-negatives appear pink
The Gram Stain
Gram-positive rods
Gram-negative rods
Gram-positive cocci
Gram-negative cocci
Gram-positive cocci
AnaerobicGram-positive rods
AnaerobicGram-negative rods
AnaerobicGram-positive cocci
AnaerobicGram-negative cocci
Gram-negative Gram-negative
Pink on Macconkey Agar
Pale on Macconkey Agar
Biochemical TestsBiochemical Tests
VocabularyVocabularyAerobicAerobic – required oxygen. – required oxygen.Anaerobic Anaerobic – growing only in the absence of – growing only in the absence of
oxygen.oxygen.Antibiotic susceptibility testingAntibiotic susceptibility testing – determining – determining
the susceptibility of microorganisms to the susceptibility of microorganisms to specific antibiotics.specific antibiotics.
BacillusBacillus – rod-shaped bacterium – rod-shaped bacteriumCoccusCoccus – spherical bacterium – spherical bacteriumColonyColony - defined mass of bacteria assumed to - defined mass of bacteria assumed to
assumed to have grown form a single assumed to have grown form a single organismorganism
CommunicableCommunicable – able to be transmitted directly – able to be transmitted directly of indirectly from one individual to another.of indirectly from one individual to another.
CultureCulture – growth of microorganisms in a – growth of microorganisms in a special medium; the process of growing special medium; the process of growing microorganisms in the laboratory.microorganisms in the laboratory.
DNADNA – nucleic acid found primarily in the – nucleic acid found primarily in the nucleus of all living cells that carries genetic nucleus of all living cells that carries genetic information; deoxyribonucleic acid.information; deoxyribonucleic acid.
Fastidious organismFastidious organism – organism that requires – organism that requires special nutritional factors to survive.special nutritional factors to survive.
FissionFission – asexual reproduction of a – asexual reproduction of a microorganism.microorganism.
FormalinFormalin – solution of formaldehyde used as a – solution of formaldehyde used as a fixative of preservative.fixative of preservative.
Gram-negativeGram-negative – designation for bacteria that – designation for bacteria that lose the crystal violet (purple stain) and lose the crystal violet (purple stain) and retain the safranin (red stain) in the Gram retain the safranin (red stain) in the Gram stain procedure. stain procedure.
Gram-positiveGram-positive – designation for bacteria that – designation for bacteria that retain the crystal violet( purple stain) in the retain the crystal violet( purple stain) in the Gram stain procedure.Gram stain procedure.
Gram stainGram stain – differential stain used to classify – differential stain used to classify bacteria.bacteria.
HostHost – organism from which a parasite obtains – organism from which a parasite obtains nutrients and in which some or part of the nutrients and in which some or part of the parasites' life cycle is carried.parasites' life cycle is carried.
HyphaeHyphae – filaments of mold that makes up the – filaments of mold that makes up the mycelium.mycelium.
Media and CultureMedia and Culture•Media: Nutrients (agar, pH indicators, proteins and carbohydrates) used to grow organisms outside of their natural habitats
•Culture: The propagation of microorganisms using various media