1. Diagnosis of Bacterial InfectionsDiagnosis of Bacterial Infections
PRESENTER
Shakira
Ghazanfar
PhDScholar
24-1-2013
ISLAMABAD
‫الرحيم‬ ‫الرحمن‬ ‫اللة‬ ‫بسم‬‫الرحيم‬ ‫الرحمن‬ ‫اللة‬ ‫بسم‬

2. Diagnosis of BacterialDiagnosis of Bacterial
InfectionsInfections

3. TYPES OF SAMPLESTYPES 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

4. Steps in diagnostic isolation andSteps in diagnostic isolation and
identification of bacteriaidentification of bacteria
 Step 1. Samples of body fluids . blood, urine,Step 1. Samples of body fluids . blood, urine,
cerebrospinal fluid, Abscess)cerebrospinal fluid, Abscess)
 streaked on culture platesstreaked on culture plates
 isolated colonies of bacteria appear afterisolated colonies of bacteria appear after
incubation for one to several days.incubation for one to several days.
 Observation of colonies (size, texture, color, &Observation of colonies (size, texture, color, &
hemolysis)hemolysis)
 differentiating characteristic- e.g oxygendifferentiating characteristic- e.g oxygen
requirementrequirement

5. IdentificationIdentification
 Colony CharacterColony Character
 Stainining ReactionStainining Reaction
 MorophologyMorophology
 Biochemical tests and serological testsBiochemical tests and serological tests
-Commercial kits commonly used, e.g. API20-Commercial kits commonly used, e.g. API20

6. THE GRAM STAINTHE GRAM STAIN
 A colony is dried on a slideA colony is dried on a slide
 Step 1. Staining with crystal violet.Step 1. Staining with crystal violet.
 Step 2. Fixation with iodine stabilizes crystalStep 2. Fixation with iodine stabilizes crystal
violet staining. All bacteria remain purple orviolet staining. All bacteria remain purple or
blue.blue.
 Step 3. Extraction with alcohol or other solvent.Step 3. Extraction with alcohol or other solvent.
Decolorizes some bacteria (Gram negative) andDecolorizes some bacteria (Gram negative) and
not others (Gram positive).not others (Gram positive).
 Step 4. Counterstaining with safraninStep 4. Counterstaining with safranin

7. Crystal
violet
Gram's
iodine
Decolorise with
acetone
Counterstain with
e.g. methyl red
Gram-positives
appear purple
Gram-negatives
appear pink
The Gram Stain

8. Gram-positive rods
Gram-negative rods
Gram-positive cocci
Gram-negative cocci

9. Gram-positive
cocci
Anaerobic
Gram-positive rods
Anaerobic
Gram-negative rods
Anaerobic
Gram-positive cocci
Anaerobic
Gram-negative cocci

10. Gram-negativeGram-negative
Pink on
Macconkey
Agar
Pale on
Macconkey
Agar

11. Biochemical TestsBiochemical Tests

12. VocabularyVocabulary
AerobicAerobic – required oxygen.– required oxygen.
AnaerobicAnaerobic – growing only in the absence of– growing only in the absence of
oxygen.oxygen.
Antibiotic susceptibility testingAntibiotic susceptibility testing ––
determining the susceptibility ofdetermining the susceptibility of
microorganisms to specific antibiotics.microorganisms to specific antibiotics.
BacillusBacillus – rod-shaped bacterium– rod-shaped bacterium
CoccusCoccus – spherical bacterium– spherical bacterium
ColonyColony - defined mass of bacteria assumed to- defined mass of bacteria assumed to
assumed to have grown form a singleassumed to have grown form a single
organismorganism
CommunicableCommunicable – able to be transmitted– able to be transmitted
directly of indirectly from one individualdirectly of indirectly from one individual
to another.to another.
CultureCulture – growth of microorganisms in a– growth of microorganisms in a
special medium; the process of growingspecial 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 carriesnucleus of all living cells that carries
genetic information; deoxyribonucleicgenetic information; deoxyribonucleic
acid.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) andlose the crystal violet (purple stain) and
retain the safranin (red stain) in the Gramretain 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 theretain 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 thenutrients 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.

13. 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