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Microbial growth analyzer
Bioscreen C displays growth curves
and microbiological calculations in MS Excel.
Almost any strain can be used. 200 samples at time.
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Food QC - Microbiology Reader Bioscreen C
Basic Information:
In routine food QC testing a Bioscreen can be used for a total count
measuremen and for 60-70 % of food
samples only, as a mean. Bioscreen is
is not
suitable for measurement of count of special strains of bacteria (it makes only
Total Count).
From some type of food (e.g. from meat, potatoes, fish .. ) 100% of samples
are suitable for Bioscreen measurement of total count by Bioscreen because these
samples are transparent after dilution. From milk, ice cream, yogurt most of
samples can be done by Bioscreen for total count.
From some groups of samples total count cannot be done at all because these
are still too turbid even also after 1100 or 11000 dilution.
Bioscreen C Method Restrictions:
Count of special separate strains is not possible to run by Bioscreen because
as a rule Bioscreen cannot detect smaller amounts than 1000 bacteria per ml -
but special strains (Salmonella, E. coli etc) are needed to detect at range
10..100 bacteria per ml.
Not all samples can be run in Bioscreen. E.g. talc, cream, facial wash, hair
lotion, shampoo, oil, toothpaste and foam/bath/soap) cannot be done by Bioscreen
because these are too turbid even after extensive dilution. Both total count and
special bacteria (Salmonella, E. coli, S. aureus, Ps. Aeruginosa, S. typosa, Cl.
tetani and Candida albicans) cannot be measured from these too turbid samples.
Most of microorganism strains (e.g. Salmonella, E. coli, S. aureus, Ps.
Aeruginosa, S. typosa, Cl. tetani, Candida albicans etc) grow in Bioscreen very
well - even in case if only a single cell is seeded (dispensed) into a Bioscreen
well. But Bioscreen method cannot be used for measuring of low count of specific strains
- Bioscreen C method can be used if more than1000 bacteria / ml is wanted to
measure (as it is a case when measuring a Total Count).
Sterility measurement (e.g. measurement of sterility of water) cannot be
measured by Bioscreen because Bioscreen sample volume is too small (0.4 ml). But
for measurement of total count values > 1000 microorganisms / ml Bioscreen
can be used.
Growth Medium
Any own-made or commercial liquid growth medium (broth) is accepted.
Sample Preparation:
Sample preparation work is for most of samples very much the same that is for
petri dish work or for test tube work - when ready then sample is dispensed into
honeycomb well instead of dispensing into petri dish or into test tube.
Incubation Temperature:
Bioscreen C includes a wide incubation temperature range dynamic
range is 1.0-60.0 'C. Bioscreen C has heating/cooling system
(circulating heat transfer liquid) for temperature control.
QC total count test is done at 37.0, 32.0 or at 30.0 'C.
Detection Limit:
Bioscreen C detection limit in food QC is approximately 1000
bacteria/liter. The reason of that limit is that Bioscreen C
cuvette volume is small and there is needed to get some bacteria from sample
into cuvette to run test. For example for drinking water sterility testing Bioscreen
C is not suitable because in drinking water it is allowed only 3 bacteria
per LITER. If to take sample into honeycomb (50 uL of sample + 300 uL of growth
medium) then it is not possible to catch the bacteria from normal drinking water
into Bioscreen wells.
Detection limit can be easily calculated by taking into account that there
must be at least 10 bacteria in honeycomb well to get reliable results. Example
calculation Usually sample volume is 50 ul. So 10 bacteria must be in 50 uL of
sample (rest up to 350 uL is growth medium). 10 bact/50 uL = 200 bacteria/ 1 mL.
But if dilution is needed (e.g. meat homogenization 110 then 200 changes to
2000).
Bioscreen C runs as mean 60-70% of food samples for total count.
Rest of 30% of food samples are needed to run manually or by other means. And
special bacteria counts (like Salmonella, E. coli etc.) cannot be done because
the allowed limits are too small
Bioscreen C can run total count with these samples where it is
accepted over 1000 bact/ml (e.g. fish, meat, milk). E.g. 100% of meat samples
can be run for total count.
Experiment Length:
In Bioscreen viable count can be found 2-4 times quicker than with Petri dish
method. The Bioscreen gives full total count answer in 12-16 hours (Petri dish
method takes 48 hours).
