[Bioluminescent assay of total bacterial contamination of raw milk].
A rapid (30-35 min) bioluminescence assay of total bacterial contamination (TBC) of raw milk was optimized. This method includes incubation of milk samples in the presence of Neonol-10 and medical purity grade pancreatin with further removal of nonbacterial ATP by filtration through a membrane filter, cell disruption by treatment with dimethyl sulfoxide, and measurement of ATP concentration in a reaction with the bioluminescent reagent Immolum. The TBC detection threshold is 0.5 x 10(5) colony-forming units (CFU) per ml milk. Coefficients of correlation between the standard plate count method and bioluminescence assay (R) and residual standard deviations (Sxy) in raw milk samples (n = 140) were 0.83 and 0.54, respectively. In sterilized milk samples artificially contaminated with pure cultures of the main representatives of milk microflora (coli-forms, Staphylococcus aureus, Streptococcus thermophilus, and Streptococcus group D), these values were 0.89-0.99 and 0.09-0.29, respectively. The specific content of ATP was found to be (0.8 +/- 0.1) x 10(-18) mol/CFU in coli-forms; (12.0 +/- 8.1) x 10(-18) mol/CFU in S. aureus; (35.2 +/- 16.9) x 10(-18) mol/CFU in S. thermophilus; and (42.5 +/- 1.3) x 10(-18) in Streptococcus group D.
Frundzhiam
V G
VG
Lomonosov Moscow State University, Russia. vgf@ipcom.ru
Brovko
L Iu
LIu
Babunova
V S
VS
Kartashova
V M
VM
Ugarova
N N
NN
D000818:Animals; D015169:Colony Count, Microbial / Q000379:methods*; D008163:Luminescent Measurements; D008892:Milk / Q000382:microbiology*