Impact of Medicated Feed on the Development of Antimicrobial Resistance in Bacteria at Integrated Pig-Fish Farms in Vietnam

Abstract

Integrated livestock-fish aquaculture utilizes animal excreta, urine, and feed leftovers as pond fertilizers to enhance the growth of plankton and other microorganisms eaten by the fish. However, antimicrobial-resistant bacteria may be transferred and develop in the pond due to selective pressure from antimicrobials present in animal feed, urine, and feces. In an experimental pig-fish farm located in periurban Hanoi, Vietnam, nine piglets were provided feed containing 5 g of tetracycline (TET)/kg pig weight/day and 0.45 g of enrofloxacin (ENR)/kg pig weight/day during the second and fourth (last) months of the experiment. The aim of this study was to determine the association between the provision of pig feed with antimicrobials and the development of antimicrobial resistance, as measured in a total of 520 Escherichia coli and 634 Enterococcus strains isolated from pig manure and water-sediment pond samples. MIC values for nalidixic acid (NAL) and ENR showed that E. coli and Enterococcus spp. overall exhibited significant higher frequencies of resistance toward NAL and ENR during the 2 months when pigs were administered feed with antimicrobials, with frequencies reaching 60 to 80% in both water-sediment and manure samples. TET resistance for both indicators was high (>80%) throughout the study period, which indicates that TET-resistant E. coli and Enterococcus spp. were present in the piglets before the initiation of the experiment. PCR-based identification showed similar relative occurrences of Enterococcus faecium, Enterococcus faecalis, and other Enterococcus spp. in the water-sediment and manure samples, suggesting that Enterococcus spp. isolated in the ponds originated mainly from the pig manure. The development of antimicrobial resistance in integrated animal husbandry-fish farms and possible transfers and the impact of such resistance on food safety and human health should be further assessed.

Antibiotic Use And Practices In Selected Fish Farms In The Ashanti Region Of Ghana

“…This is in agreement with findings reported in a study of some fish ponds in Ghana by Ampofo et al [13] where fish farmers used poultry waste, blood waste, sewage, cow dung and pig dung to fertilise ponds. The use of organic manure by farmers may contribute to antibiotic resistance on the farms by transfer of antibiotic residues and resistant bacteria to fish farms if the commercial farms from which the manure is sourced use antibiotics [9,29,30]. Elsaidy et al [29] in a study of bacterial isolates from water and fish raised in ponds receiving chicken manure recommended the use of fermented chicken manure as a bacteriologically safe fish pond fertilizer.…”

“…There has been an alarming increase in global reports of antibiotic resistance on fish farms over the years [7,8]. Though some farms do not use antibiotics directly, fish farming practices such as the use of animal manure, waste water, human excreta in fish farms and disposal of untreated effluents from fish farms may contribute to antibiotic resistance in fish farms and adjoining water bodies [9,10]. Ghana has a thriving freshwater aquaculture industry with tilapia and catfish being the most farmed species in freshwater farms with tilapia farming alone contributes 88% of total fish farming in Ghana [11].…”

Public Health Risks of Multiple-Drug-Resistant Enterococcus spp. in Southeast Asia

“…Legislation and regulations to control the supply and excessive use of antimicrobials are very poor in many developing Southeast Asian countries (5)(6)(7), and the prevalence of antimicrobial resistance in major bacterial pathogens such as enterococci has been rapidly increasing in Asia (8)(9)(10)(11). In particular, the rise of multidrug-resistant (MDR) enterococci is of great concern.…”

Understanding the contribution of environmental factors in the spread of antimicrobial resistance

“…This results in further selection and transfer of antibiotic resistance genes within the microbial community, within in the surrounding environment [38,51]. A study of pigs in VAC systems, revealed high levels of resistance to tetracycline, nalidixic acid and enrofloxacin, among enteric bacteria [52]. This suggests that as a result of exposure to high concentrations of various antibiotics, the risk of colonisation with antibiotic-resistant bacteria and genes increases in the intestinal tracts of livestock.…”