Studies on antibiotic residues in milk in Punjab and its public health significance
Loading...
Files
Date
2014-03-27
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The presence of residues of antimicrobial agents in food of animal origin in excess of the established maximum residue limits (MRLs) indicates that good veterinary practices are not being respected. Consequently, it is necessary to establish simple, sensible and reliable analytical methods for the determination of multiresidues of different classes of antimicrobials in food and particularly in milk. Therefore, the present study was conducted to determine antibiotic residues in milk, evaluate the effect of various processing techniques on these residues and to assess the risk associated with consumption of the milk having residues.
In total, 356 milk samples were collected from individual animals. Out of these, 46 (12.9%) and 33 (9.2 %) samples were found positive for enrofloxacin and ciprofloxacin, respectively. Similarly, for tetracyclines, a total of 321 milk samples were collected from individual animals. Out of these 321 milk samples, 51 (15.8%), 8 (2.4 %) and 0 (0%) samples were found positive for oxytetracycline, tetracycline and doxycycline, respectively. While, for cloxacillin, 314 individual animal milk samples were collected from various districts of Punjab. Out of these 314 milk samples collected, 7 (2.2%) samples revealed the presence of cloxacillin residues.
Among the 108 pooled milk samples collected from market yielded 14 (12.9%) and 13 (12%) samples as positive for enrofloxacin and ciprofloxacin, respectively. Apart from the pooled milk samples, 19 pasteurized milk samples were also collected from market in which one (5.2%) and two (10.5%) samples were found positive for enrofloxacin and ciprofloxacin, respectively. Among the total fluoroquinolones, 17 (15.7%) and 3 (15.7%) samples were found positive in pooled and pasteurized milk samples, respectively. Similarly, in 100 pooled milk samples collected from market, 11 (11%) and 2 (2%) were found to be positive for oxytetracycline and tetracycline respectively. While none of the samples were found to be positive for doxycycline. Among the 19 pasteurised milk samples collected from market, one (5.2%) and one (5.2%) were found positive for oxytetracycline and tetracycline, respectively. Doxycycline was not found in any of the pasteurised milk samples. While none of the
pooled (108) and pasteurized milk (19) samples showed the presence of cloxacillin residues.
The effect of heat treatment on antibiotic residues was evaluated. The different types of heat treatment given to milk samples included, boiling, autoclaving, microwave heating and pasteurization. The percentage reduction of antibiotic residues was recorded for different heat treatment. The percentage reduction of cloxacillin residues at 100 and 500 μg/kg ranged from 1.92-7.6 and 0.9-9.2 %, respectively. The percentage reduction for enrofloxacin and ciprofloxacin at 100μg/kg ranged from 1.820.7 and 5.8-18.7%, respectively. While for oxytetracycline, tetracycline and doxycycline residues, the percentage reduction at 100 and 500 μg/kg concentrations ranged from 11.2-30, 11.1-32, 2.7-27.7 and 10.4-26.4, 5.9-17.9, 9.2-26.3%, respectively. Based on the mean values of antibiotic residues, the Hazard Quotient was evaluated for tetracycline, oxytetracycline, fluoroquinolones and cloxacillin in pooled raw milk samples having values 0.027, 0.03, 0.04 and 0, respectively.
The residual levels of tetracyclines, fluoroquinolones, aminoglycosides, chloramphenicol and sulfamethazine in raw milk samples from Punjab were also monitored. Out of 133 milk samples analysed for the presence of tetracycline residues, 18 samples were found to contain tetracycline residues. Similarly, out of 60 cattle milk samples analyzed, 6 samples were found positive for fluoroquinolone (enrofloxacin/ciprofloxacin) residues, while 4 samples were found positive for aminoglycoside (streptomycin/dihydrostreptomycin) residues giving a prevalence rate of 10% and 6.67%, respectively.
Out of 122 milk samples analyzed, 16 E coli isolates were obtained giving a prevalence rate of 13.1%. All the biochemically confirmed isolates were confirmed for the presence of uidA gene by PCR. E coli specific primer amplifying a 1487 bp fragment of the uidA gene was used. Similarly, for the β lactam resistance, a primer amplifying a 857 bp fragment of blaTEM gene was used.All the sixteen isolates of E coli were also tested for their sensitivity against 27 different commonly used antibiotics and chemotherapeutic agents. Among all the cephalosporins tested, 100% susceptibility was found for ceftriaxone, cefotaxime and cefuroxime. All the isolates were resistant to cephalothin. While, 50% isolates were resistant to cefixime and ceftazidime and 50% isolates showed intermediate susceptibility to cefixime. Similarly, 100% resistance was found for oxacillin and carbenicillin.
Description
Keywords
Antibiotics, HPLC, Tetracycline, Fluoroquinolones, Beta lactam, Hazard Quotient, E coli, ELISA