title: 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 μg of tetracycline (TET)/kg pig weight/day and 0.45 μg 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.
authors: Veterinary Hygiene Department, National Institute of Veterinary Research, Hanoi, Vietnam.
authors: Son Thi Thanh
authors: ST
authors: Dang
authors: Andreas
authors: A
authors: Petersen
authors: Dung
authors: D
authors: Van Truong
authors: Huong Thi Thanh
authors: HT
authors: Chu
authors: Anders
authors: A
authors: Dalsgaard
references: Int J Food Microbiol. 2003 Dec 1;88(2-3):133-45
references: 14596986
references: Appl Environ Microbiol. 2008 Jul;74(14):4405-16
references: 18502931
references: Environ Microbiol. 2003 May;5(5):395-402
references: 12713465
references: Int J Food Microbiol. 2003 Dec 1;88(2-3):311-4
references: 14597003
references: Appl Environ Microbiol. 2002 Dec;68(12):6036-42
references: 12450826
references: J Water Health. 2007 Jun;5(2):209-18
references: 17674570
references: J Anim Sci. 1996 Jun;74(6):1284-7
references: 8791200
references: Int J Antimicrob Agents. 2006 Feb;27(2):131-7
references: 16388931
references: Microb Drug Resist. 2008 Jun;14(2):163-9
references: 18500921
references: J Clin Microbiol. 1995 Jan;33(1):24-7
references: 7699051