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For the traditional detection of bacterial concentration, there
are somedisadvantages needed to be improved as following:First,
the detecting bacteria need to be cultured on the nutrient agar
orbroth for growing and metabolizing, so the detection time is
much longer(ca. 24 ~ 48 hr). Second, if the bacterial
concentration of samples are toohigh to count, then the original
bacterial concentration must to be dilutedby ten-fold dilution
method. Third, the culture results of bacteria needmanpower to
concern, and the process will waste more time and manpower.
Finally, the traditional method is not suitable to monitor the
cultureprocesses continuously and save the detection time.
Therefore, look like thediseases of bacterial infection, such as
bacteriuria and bacteremia, even thefood poisoning, etc. The
traditional methods can not shorten the detectiontime
effectively. Although there are mature techniques and equipment
forbacterial detection, most of current systems are too
expensive for commonly use.In this study, we had constructed a
multi-channel series piezoelectric quartzcrystal system. This
system can be applied to monitor the small change ofconductivity
by its frequency response, and it also has good sensitivity(the
best sensitivity of frequency is 0.15 Hz/(S). Here, we use the
detectionsystem to distinguish conductivity method and impedance
method for shorteningthe detection time of bacterial
concentration, and afford another high sensitivitytool for
conductivity detection. By this way, due to different initial
conductivity of samples, the multi-channelpiezoelectric quartz
crystal system can achieve the optimal frequency sensitivityby
proper impedance match. Therefore, the algorithm " Neural
Network " is adoptedto find out the optimal frequency
sensitivity. For the conductivity change from1.6 to 2.3 mS, the
system matched a resistance about 500 ( can achieve the
bestfrequency sensitivity 130 Hz.The optimal system is applied
for food, such as fresh milk. It expresses a highsensitivity and
reliability which samples cultured in the SPYE broth. The
frequencydetection time (FDT) is 3.5 and 5 hr respected to 107
and 105 cells/ml of milk\bacterial counts individually, the
final results are shorter than traditionalmethods. The system
also can be used for the bacteriuria (bacterial
concentrationfrom 5×108~2.6×101 cells/ml, the detection time
from 40~343 min, MuellerHinton broth) and bacteremia ( bacterial
concentration from 8×106~2×102 cells/ml, the detection time
from 172~502min, Nutrient broth).The MMSPQC system is easy to
develop a convenient and efficient analysis tool,especially for
food and clinical medical detection of microorganisms.
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