Occurrence of antimicrobial residues in pasteurized milk commercialized in the state of Paraná, Brazil.

Milk containing antimicrobial residues presents a health risk to the human population. The objective of this study was to use an enzyme-immunoassay technique to determine the occurrence of antimicrobial residues in 151 samples of pasteurized milk sold in cities of the State of Paraná, Brazil, from March 2005 to April 2006. Fifty-nine (41.3%) of the 151 samples contained antimicrobial residues. Residues of neomycin, streptomycin, and/or dihydrostreptomycin and chloramphenicol were found in three, two, and four, respectively. None of the samples with neomycin residues had levels above the maximum residue limit (MRL) permitted in this country, which is 500 microg/kg. Only one sample had a higher level of streptomycin-dihydrostreptomycin (260 microg/kg) than the MRL (200 microg/kg). The four samples positive for chloramphenicol had levels above the zero tolerance level. In the qualitative analysis, 41 of 151 samples contained tetracyclines (tetracycline, chlortetracycline, and/or oxytetracycline), 4 of 82 samples contained gentamicin, and 5 of 151 samples contained beta-lactams (amoxicillin, ampicillin, ceftiofur, cephapirin, and/or penicillin G). It was not possible to determine whether the levels of the antimicrobials found in the qualitative analyses (tetracyclines, gentamicin, and beta-lactams) were above the MRLs because the detection limits were below the MRLs in Brazil. In nine samples, two or more antimicrobial residues were found. The results demonstrate the need for monitoring various antimicrobial residues in pasteurized milk to ensure safety, quality, and integrity and to protect the health of the Brazilian population.