2015 Microorganism Identification Process Lecture 1 Introduction to Bacterial Identification Accurate and definitive microorganism identification including bacterial identification and pathogen detection is essential for ID: 342006
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Diagnostic Microbiology Laboratory -2015-
Microorganism Identification Process *Lecture 1*Slide2
Introduction to Bacterial Identification Accurate and definitive microorganism identification, including bacterial identification and pathogen detection, is essential for correct disease diagnosis, treatment of infection and
trace-back of disease outbreaks associated with microbial infections. Bacterial identification is used in a wide variety of applications including microbial forensics, criminal investigations, bioterrorism threats and environmental studies.Slide3
Approach to Laboratory DiagnosisThe laboratory diagnosis of infectious diseases involves two main approaches:Bacteriological approach; in which the organism is identified by: microscopic observation, macroscopic identification, biochemical reactions and molecular diagnosis techniques.Immunological (serological) approach; in which the organism is identified by detection of antibodies against the organism in the patient’s serum.Slide4
Cultural CharacteristicsMicroorganisms may show distinguishing gross morphologies when cultured on different media. This macroscopic
appearance of bacteria (characteristic growth patterns which can be observed with the naked eye) is often used in their identification.Slide5
Cultural Characteristics are observed according to 1. Observe the amount of growth none =
0 slight = +moderate = ++ abundant = +++ 2. Coloration-
Two types of pigmentation may occur:
a. pigmentation occurring within the organism itself; or
b
. water soluble pigment that diffuses into the surrounding medium.
Most organisms will lack
chromogenesis
(
pigment production
), exhibiting a white, beige, or gray growth. Pigmentation within the organism may be red, yellow, violet, or other
colors.
Soluble
pigments may be blue, green, yellow, brown, or other
colors.
Hold the
plate
up to the light to examine for diffusible pigments. It may be helpful to compare the color of the agar with an
uninoculated
media. Slide6
3. Opacity- Surface growth can be termed as opaque, as transparent, or as translucent partial transparency) depending on the degree of growth.4. Form- The gross or macroscopic appearance
of the growth from the single streak inoculation is described by:a. filiform - uniform growth along the line of inoculation. b. echinulate- margins of growth have a toothed appearance. c. beaded- separate or semi confluent colonies. d. effuse- growth is thin, veil-like, unusually spreading.
e. arborescent- branched, tree-like growth.
f. rhizoid- root-like appearanceSlide7Slide8
Morphology and stainingThere are many different ways to stain bacteria so that they can be more easily visualized under the microscope. Some stains can also be used to identify and classify bacteria. 1. Gram stain
2. Acid fast StainOther stains used to visualize bacterial structureSpore stainFlagellar stainCapsule stainSlide9
Biochemical Characteristics1. Fermetation & oxidation.2.
IMVIC tests.3. Biochemical tests.4. API 20 E.Slide10
Other techniques1. PCR2. Phage typing3. Other molecular techniquesSlide11
Serological characteristicsTo Identify several strains of the same type of bacteria we need to perform serotyping of them such as:1. Widal test
2. Lancefield grouping3. Protien A latex4. othersSlide12
How to handle microbiological sampleSome samples will demonstrate microbial growth and require further laboratory analysis to identify the contaminants. When growth is detected, the sample should be taken from the clean section of the laboratory to the live culture section without undue delay. Subculturing, staining, microbial identification, or other investigational operations should be undertaken in the live culture section of the laboratory.
If possible, any sample found to contain growing colonies should not be opened in the clean zone of the laboratory. Careful segregation of contaminated samples and materials will reduce false-positive result.. Slide13
How to handle microbiological sampleSoo it necessary to ensure:1. Proper collection of the sample2. Adequate amount3. Requisitions
4. Tightly capped containerSlide14
How to handle microbiological sampleWhen needed, a written test request must include the following information:1. Hospital No.2. Full name
3. Gender4. Date of birth5. Address6. Social security no.7. For female pregnant/ lactating8. Date of illness9. Signs/ symptoms10. Date of onset
11. Recent travel history
12. Immunization Slide15
Identification of samples1. Type of specimen2. Collection date and time3. Laboratory number
4. Laboratory findings5. Test requested6. Ordering physicianSlide16
Specimen handling and storageSamples should be delivered to microbiology central processing area, within the specified period and then CPA will1. Check requisition for completeness.
2. Store the sample until they are picked up to microbiology staff.When STAT requests are received, the CPA staff should inform the microbiology supervisor. Slide17
Specimen rejection criteria1. The information in the label doesn’t match the information on the request form.2. The specimen was transported in improper container or at wrong temperature.3. Leaking specimen.4. The quantity of specimen is insufficient.Slide18
Comments1. Blood received in blood culture is unsuitable for fungal isolation.2. Saliva is unacceptable for culture.
3. Multiple samples sent with the same request should be noticed.Slide19
Samples not satisfactory for culturing1. Sample in fixative2. Dried out swab3. 24hrs urine or sputum4. Urine still more than 2hrs at room temperature.
5. Antibiotic medicated patient6. Anaerobic culture for vaginal, cervical, or urine samples7. Stool samples from more than 5 days inpatient.Slide20
Media ClassificationConsistencySolidSemisolidLiquid –Broth-
Nutritional componentSimpleComplexSynthetic or Chemically Defined Media: Exact chemical composition is knownFunctional useBasic-General- mediaSelective
Differential
Enriched
Enrichment
TransportSlide21
End of Lecture