Agriculture Reference
In-Depth Information
involving fluoroquinolones (FQs), are of particular environmental concern.
Quinolones belong to the family of gyrase inhibitors. They denote a striking
potency against enteric gram-negative bacilli, lesser activity against non-enteric
gram-negative bacilli and staphylococci and usually marginal activity against
anaerobes and streptococci. Quinolones have been used in veterinary and human
medicine for over a decade; during this time, their entry into the environment
has been continuous. In recent years, different reviews have covered, totally or
partly, the subject of the analysis of quinolone residues in edible animal products
(Carlucci
1998
; Hernandez-Arteseros et al.
2002
) or in the environment (Pico ve
Andreu
2007
).
Food products are complex mixtures consisting of naturally occurring com-
pounds such as proteins, carbohydrates, lipids, vitamins, phenolic compounds,
aromas and organic acids, as well as contaminants from agrochemical or veterinary
treatments, packaging materials or technological processes. Quinolone analysis in
those samples requires, additionally, a sensitive chromatographic method, an
extraction procedure that offers suitable recoveries for the analytes and a clean-
up step to remove some of the co-extracted compounds (Andreu et al.
2007
). Thus,
biosensors have demonstrated improved ability to monitor quinolones and other
residues as cheaply and as quickly as possible and even to have the possibility of
allowing on-site field monitoring. An electrochemical biosensor was described for
the detection and the presumptive identification of quinolones and tetracycline in
milk (Pellegrini et al.
2004
). The measurement was based on the dioxide-
production rate in relation to inhibition of microbial growth (
Escherichia coli
ATCC 11303). Sensitivity was satisfactory, considering that, for all tetracyclines
and quinolones studied, it has been possible to detect residue concentrations equal
to or below 25 lg/kg. MRLs for milk are all higher than this concentration. Besides,
the most successful approach in this field has been the coupling of immunoassays
with flow-through sensors, which makes possible the detection of biological inter-
actions by an appropriate transducer in real time (Andreu et al.
2007
).
The
-lactam antibiotics, including penicillins, are the most important antimi-
crobial substances used for mastitis treatment. Eventually, this is also the most
usually occurring type of antibiotic residues in milk. Today, in addition to the
traditional microbial inhibitor tests, sensitive and rapid immunoassays and receptor
are used in residue control. Because of the limitations in throughput capacity of
these tests, recent applications of automated biosensor technology in food analysis
are of great interest. An SPR-based biosensor (Biacore) was used to design an
inhibition assay to detect
β
-lactam antibiotics in milk. A microbial receptor protein
with carboxypeptidase activity was used as a detection molecule. One advantage of
using this receptor protein over antibodies that are more usually used is that only the
active, intact
β
-lactam structure is recognized, whereas most antibodies detect both
active and inactive forms. In the presence of
β
-lactam antibiotics, the formation of a
stable complex between receptor protein and antibiotic inhibits the enzymatic
activity of the protein. The decrease in enzymatic activity was measured using an
antibody against the degraded penicillin G, and substrate in milk samples was
quantitatively determined. The limit of detection of the assay for penicillin G was
β
