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