Tetracycline resistant lactococci from fish farms – a case study

Tetracycline resistantlactococci from fish farms –a case study Atte von Wright
University of Kuopio (UKU)
Institute of Applied Biotechnology
P.O. Box 1627
FIN-70211 Kuopio
Finland
† Dairy lactococci are very sensitive to most antibiotics (antibiotic residues in milk a majorcause of starter failures) † Occasional multiresistant isolates have been detected lately in foods (i.e. Perreten et al. 1997.
Nature, 389:801-802) † Cold water fish apparently are one of the natural habitats of lactococci, and fish farmscould represent an environment, wherelactococci have (in the past) been exposed to awidespread use of antibiotics in the form ofmedicated feeds Intestinal microflora of farmed fish
Background
† Little is known about the composition of the intestinal microflora of either wild or cultivatedsalmonid species † A major study on the effects of different feed formulation on the fysiology and gutmicrobiology of cultivated rainbow trout(Oncorhynchus mykiss) is being conducted atUKU in collaboration with Fish InnovationCentre (a regional aquaculture developmentproject) and Finnish Game and FisheriesResearch Institute (ProBio-project) Intestinal microflora of farmed fish
Outline of the study
† Newly hatched fingerlings have been fed with experimental diets (traditional fishmeal based feeds and soya feeds) up to 18weeks † Due to a Flavobacterium infection, the hatchlings had been treated with tetracycline-containig feed (appr. 7 g kg-1) beforeentering the trial † At every 4 weeks fishes (5 fishes/tank, 25 fishes per feed formulation) were withdrawn, their intestinal contents evacuated,and microbiological examinations on the cultivable microflorawere undertaken (total aerobes/anaerobes, lactic acid bacteria,proteolytic and lipolytic bacteria) using 15 ºC as the incubationtemperature † Typical representatives of lactic microflora were picked up, purified and characterised using the API CH50 kit and 16SrDNA sequencing † The total numbers of lactic acid bacteria generally in the order of log cfu 2.5 – 3.5 g-1intestinal content † 30 lacitc acid bacterial isolates from MRS- plates were randomly picked forcharacterization † The preliminary species distribution among the 16S rDNA sequenced isolates was the following:an unknown lactobacillus-like organism (16SrDNA shows no matches with known species) 7;Lactococcus lactis ssp. lactis 5;Carnobacterium sp. 3 and 2 Micrococcus sp.
† The lactococcal isolates were included among the strains screened in the ACE-ART -project † The screening was done using agar dilution † The antibiotics tested were: erythromycin, tetracycline, chloramphenicol, ampicillin,ciprofloxacin, vancomycin, thrimethoprim andkanamycin The antibiotic resistance pattern of thelactococcal isolates Type of
feed
Fishmeal
Fishmeal
< 0.25
Fishmeal
† In this trial Lactococcus lactis ssp. lactis is a relatively common finding in the fish intestine † Among five randomly picked isolates there were two showing an unambiguous resistance totetracycline (the molecular nature of theresistance has not been clarified, yet) † All the fish had been exposed to tetracycline † Although there is no proof of a causal relationship, the possibility of selection forresistance end enrichment of resistant strainsdue to the antibiotic treatment cannot beexcluded † Atte von Wright (ACE-ART, ProBio)† Jouni Heikkinen, MSc, post grad.
† Outi Kemiläinen, MSc, (ProBio)† Jenni Korhonen, MSc, post grad. (ACE-

Source: http://d1128636.pre58.site-manager.com/images/site/assets/attes%20refined%20version.pdf