2. BACTECT - 9240
BACTEC SYSTEM – BECTON DICKINSON Microbiology system , Sparks , Maryland
It is a fully automated machine, in which the detection is based on the
fluorescene produced as a result of the CO2 which is released by the micro
organisms
PRINCIPLE -
Microbial detection system monitors the presence and production of
CO2,dissolved in the culture medium.
If micro organism is present CO2 is produced as the organism metabolises the
substrate in the culture medium.
When the CO2 production occurs, the gas permeable sensor installed in the
bottom of each culture bottle produces a colour indication.
CO2 diffuses into the sensor and dissolves into the water present in the
sensory matrix.
H+ ion causes a drecease in pH which inturn increases the flurescent output
of the sensor
3. BLOOD CULTURE BOTTLES
Bac Tec Plus
- Aerobic plus – Blue
- Anerobic plus – Orange
- Paediatric plus – Pink
- Mycosis - Fluorescent green
- Bone marrow -Black
4. BacT/ALERT
This is an another automated technique to detect the pathogens causing
bacteremia , septicemia or blood stream infections.
They are of 3 types – aerobic cultures
- anaerobic cultures
- paediatric cultures
The media contains – absorbant polymeric beads (resins)
- and other complex amino acid and carbohydrate
substrate in purified water.
BacT/ALERT Bottles
Aerobic - Green
Anaerobic - Orange
Paediatric - Yellow
5. PRINCIPLE
The CO2 produced by the microorganism is detected by the colourimetric
sensor.
The CO2 production is intiated as the organisms metabolise the substrate in
the culture medium.
When the micro organism produces the CO2, the gas permeable sensor
installed in the bottom of each culture bottle changes from blue-green to
yellow.
The light colour results in the increase in the reflectance unit.
Bottle reflectance is monitored and recorded by the instrument every 10 min
each.
6. BACTECT aerobic plus bottle / BacT/ALERT FA
BACTECT anaerobic plus bottle / BacT/ALERT FN
Sample collection – 5-10ml blood is collected aseptically.
If a bottle flages positive pull out the bottle aspirate 2mlof the broth and centrifuge
(3000rpm) and smear the deposite, and subculture on corresponding media for further
confirmation.
If the bottle is negative send the report after 5 days
BACTEC Paediatric plus bottle / BacT/ALERT PF
Sample collection – 1-3ml blood is collected aseptically in paediatric bottle.
If the botte is negative send the report after 5 days. If endocarditis suspected then
give 21 days protocol.
7. MALDI – TOF MS
Matrix – assisted laser desorption ionisation – time of flight (MALDI-TOF)
mass spectroscopy uses 16s ribosomal protein.
Compares the mass peaks achieved by the test strains to those of approx.
3,500 known strains in the Bruker MALDI Biotyper Library.
Organism identification within 20 minutes of starting the process.
The resultant identification is meant to be robust, as it relies on high
abundance proteins.
8. VITEK 2
Automated microbiology system utilizing growth-based technology.
The system is available in three formats (VITEK 2 compact, VITEK 2, and VITEK 2
XL) based on the difference in increasing levels of capacity and automation
All three systems accommodate the same colorimetric technology to determine
individual biochemical reaction contained in the variety of microbe identification
cards.
The Identification cards are based on established biochemical methods and newly
developed substrates measuring carbon source utilization, enzymatic activities,
and resistance.
There are 47 biochemical tests in GN card and one negative control well and 43
biochemical tests in GP card.
Final results are available in approximately 10 hours or less in GN cards and
approximately 8 hours or less in GP cards.
9. INOCULUM PREPARATION
Select the vitek2 compact cassette with labelled barcode defining casette
number & place the polysterene tube in the casettes.
Then take the 3 ml vitek saline in the tube and select the isolated colonies
from the plate & suspend in saline and vortex.
Check the inoculum density with the help of densicheck plus
Mc Farland for GNB 0.50-0.63
GPC 0.50-0.63
YST 1.80-2.20
Put the selected cards pre inserted transfer tube in the respective suspension
in selected polstyrene tubes
11. QUALITY CONTROL
Quality control for bacteria
Klebsiella pneumoniae ATCC 700603
Pseudomonas aeruginosa ATCC 25853 for ID GN
Staph aureus ATCC 25923 with each lot change.
Quality control for yeast
Candida albicans ATCC 90028 with each lot change.
