A study of antibiotic residues in meat sold in butcheries and supermarkets around Mafikeng, North West Province
This study examined antibiotic residue and the frequency of contamination of meat purchased from main butcheries and supermarket around Mafikeng, North West Province, South Africa. The present study was thus designed to estimate residue levels of tetracycline, sulphonamides, ciprofloxacin and streptomycin antimicrobial residues in chicken, pork and beef samples. A total of 150 ( 50 chicken, 50 pork and 50 beef) samples composed of kidney, liver and muscles were analysed using Enzyme-Linked-Immunosorbent Assay (ELISA), Thin Layer Chromatography (TLC) and High Performance Liquid Chromatography (HPLC). Results obtained from this study reaveled the presence of antibiotic residues in different organs (liver, kidney and muscle) with pork tissues having contamination of 8 (6%), 1 (2%) and 10 (20%) samples respectively of liver, muscles and kidneys contained tetracycline, streptomycin, sulphonamides and ciprofloxacin residues. In chicken, tissues, 22 ( 44%) and 10 (20%) samples of liver and muscles respectively, contained tetracycline, streptomycin, sulphonamides and quinolones ( ciprofloxacin) residues. While beef, tissues, 15 (30%), 5 (10%) and 1 (2%) samples of liver, kidney and muscles respectively contained tetracycline, streptomycin, sulphonamides and quinolones ( ciprofloxacin) residues In addition, the results obtained in this study revealed that 65 ( 43%) out of 150 samples were simultaneously detected positive for four antibiotics (tetracycline, sulphonamides, ciprofloxacin and streptomycin) residues, however all the samples were bellow MRL. Although the levels were below their MRL given by the European Union, South Africa and the Codex Alimentarius Commission, their presence may still be regarded as a health hazard as they may causes allergic reactions or produce drug-tolerant bacteria in human after long exposure. There were some samples which had more than one antibiotic residue. In this study, significant correlations (P~0.05) between different methods (TLC, ELISA HPLC) used as well as among sample types (muscles, liver and kidney), and species (beef, chicken and pork) were observed. This showed the regularity, consistancy repeatability and quality of techniques used in this study. In addition the relaibility of results obtained in this study is shown by the recovery rate as well as by the calibration curves of each antibiotic and for each method used. The novelity of this work is that three different techniques (TLC, ELISA and HPLC) were used to analyse samples and results obtained are generally in correlation. Moreover, collected samples which were confirmed positive for residues were cultured for bacterial contamination and identification using the conventional biochemical methods as well as molecular techniques based on 16S rRNA species specific gene amplification by PCR and MALDI-TOF. Results obtained showed relatively high frequency 30 ( 40%) of occurrence of organisms; Macrococcus caseolyticus (60%), Enterococcus mundtii (3.3%), Bacillus spp.(3 .3%), Bacillus cereus (3.3%), Enterococcus spp.((10%) and Escherichia spp.(3 .3%) Surveillance of a pathogen over time in a regular manner is necessary to update the distribution level and to estimate its public health importance. Lastly, all the isolates were evaluated for their antibiotic resistance patterns against some common antibiotics using Kirby-Bauer antibiotic discs diffusion method. The antimicrobial profile of eight isolates showed a high resistance rates for Macrococcus caseolyticu 66.6% (20/30), followed by Enterococcus spp. 10% (3 /30), Enterococcus faecalis 10% (3/30), Enterococcus mundtii (3.33%), Escherichia spp. 3.33% (1 /30), Bacillus spp. 3.33% (1 /30), Bacillus cereus 3.33% (1 /30). The majority of isolates (83.3%) were resistant to tetracyclines followed by sulphonamides (13.3%) and lastly ciprofloxacin (3.33%). However, these results revealed that only 33.3% of pathogens were resistance. However, 66.6% of isolates were Macrococcus caseolyticus which is a non-pathogenic bacterium. Only tetracycline showed strong correlation (p<0.05) between residues and resistance from two species; chicken (1 .00) and beef (1 .00). It was observed that more bacteria were isolated from the butcheries than supermarkets. Some isolates showed resistance to multiple antibiotics. Although results of antibiotic residues obtained in this study were mostly just below the MRLs, there is a risk for consumers in case of chronic exposure. Hense, there is a need of a continous monitoring to ensure the safety of consumers. In addition, training of and information sessions with farmers to ensure that they adhere to the withdrawal periods of antimicrobial in order to obtain low/absence of antimicrobial residues should be maintained. The presence of microbial contaminants and antibiotic resistance isolated in meat might be explained by several factors such as contamination and transfer of resistance integron genes to animals. It is therefore recommended that effective food safety education and training of personnel that handle food at retail points will help in reducing the effect of these pathogens on humans.