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Use chemometric techniques in the optimization of a specific bioassay for betalactams in milk
Author(s) -
Nagel O.G.,
Molina M.P.,
Althaus R.L.
Publication year - 2012
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/j.1472-765x.2011.03169.x
Subject(s) - bioassay , penicillin , tetracycline , chemometrics , chromatography , oxytetracycline , cloxacillin , biology , chemistry , microbiology and biotechnology , antibiotics , genetics
Aims: A microbiological bioassay using Geoacillus stearothermophilus was optimized to detect betalactams at concentrations near to the Maximum Residue Limits (MRLs), with low cross‐specificity for tetracycline. Methods and Results: A factorial design (3 × 4) was used to evaluate the effects of concentration of spores (2·0 × 10 6 , 4·0 × 10 6 and 8·0 × 10 6 spores ml −1 ) and incubation time (3·0, 3·5, 4·0 and 4·5 h) on the response of the bioassay. Then, desirability function to raise the detection capabilities (CC β ) of tetracyclines and increase sensitivity to betalactams was implemented. Significant effects of Log[ S ] and incubation time [It] on the CC β of betalactams and tetracyclines were observed. Finally, high value of global desirability ( D = 0·853), adequate betalactams CC β (3·8 μg l −1 of penicillin ‘G’, 27 μg l −1 of oxacillin, 8·1 μg l −1 of ampicillin, 48 μg l −1 of cloxacillin) and high tetracyclines CC β (5260 μg l −1 chlortetracycline, 1550 μg l −1 of oxytetracycline, 1070 μg l −1 of tetracycline) were calculated. Conclusions: The application of chemometric tools allows the optimization of a bioassay that detects betalactam residues in milk. The more robust conditions have been achieved in Log[ S ] = 6·30 and [It] = 4·20 h. Significance and Impact of the Study: The logistic regression model and the desirability function are adequate chemometric techniques to improve the properties of the methods, because it is possible to increase sensitivity and decrease cross‐specificity simultaneously.