Transcript Lab 1-introduction

Microorganism
Identification Process
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.
Cultural Characteristics
Microorganisms 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.
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 (pigmentproduction),
exhibiting a white, beige, or gray growth. Pigmentation within
the organism may be red, yellow, violet, or other colors (see
demonstration tubes). Soluble pigments may be blue, green,
yellow, brown, or other colors (see demonstration tubes). Hold
the slant up to the light to examine for diffusible pigments. It
may be helpful to compare the color of the agar with an
uninoculated slant.
Cultural Characteristics are observed
according to
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 ofthe growth from
the single streak inoculation is described by comparing itto the
drawings shown in Figure 1.
a. filiform - uniform growth along the line of inoculation.
b. echinulate- margins of growth have a toothed appearance.
c. beaded- separate or semiconfluent colonies.
d. effuse- growth is thin, veil-like, unusually spreading.
e. arborescent- branched, tree-like growth.
f. rhizoid- root-like appearance
Morphology and staining
There 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 Stain
Other stains used to visualize bacterial structure
1. Spore stain
2. Capsular stain
3. Flagellar stain
Biochemical Characteristcs
1. Fermetation & oxidation
2. IMVIC
3. Biochemical tests
4. API 20 E
Serological characteristics
To Identify several strains of the same type
of bacteria we need to perform
serotyping of themsuch as:
1. Widal test
2. Lancefield grouping
3. Protien A latex
4. others
Other Characteristics
1. PCR
2. Phage typing
3. Other molecular techniques
How to handle microbiological sample
Some 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.
How to handle microbiological
sample
Soo it necessary to ensure:
1. Proper collection of the sample
2. Adequate amount
3. Requisitions
4. Tightly capped container
How to handle microbiological
sample
When needed, a written test request must include the following
information:
1. Hospital No.
2. Full name
3. Gender
4. Date of birth
5. Address
6. Social security no.
7. For female pregnant/ lactating
8. Date of illness
9. Signs/ symptoms
10. Date of onset
11. Recent travel history
12. Immunization
Identification of samples
1. Type of specimen
2. Collection date and time
3. Laboratory number
4. Laboratory findings
5. Test requested
6. Ordering physician
Specimen handling and storage
Samples should be deliverd to microbiology central processing
area, within the specified period and then CPA will
1. Check requisition for completeness
2. Store the sample untill they are picked up to microbiology
staff.
When STAT requests are received, the CPA staff should inform
the microbiology supervisor.
Specimen rejection criteria
1. 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.
Comments
1. Blood received in blood culture is unsuitable sor
fungal isolation.
2. Saliva is unacceptable for culture
3. Multiple samples sent with the same request should
be noticed.
Samples not satisfactory for culturing
1. Sample in fixative
2. Dried out swab
3. 24hrs urine or sputum
4. Urine still more than 2hrs at room temperature.
5. Antibiotic medicated patient
6. Anaerobic culture for vaginal, cervical, or urine
samples
7. Stool samples from more than 5 days inpatient.