Food Control 18 (2007) 1391–1396 www.elsevier.com/locate/foodcont 0956-7135/$ - see front matter  2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodcont.2006.10.003 Antibiotic resistance in Gram-negative bacteria isolated from farmed catWsh Samira Sarter a,¤ , Hoang Nam Kha Nguyen b , Le Thanh Hung b , Jérôme Lazard a , Didier Montet a a CIRAD, Centre de Coopération Internationale en Recherche Agronomique pour le Développement, TA40/16, 73 rue Jean-François Breton, 34398 Montpellier Cedex 5, France b Nong Lam University, Faculty of Fisheries, Tan Phu, Thu Duc Dist., Ho Chi Minh, Viet Nam Received 14 April 2006; received in revised form 17 September 2006; accepted 2 October 2006 Abstract Feeding practices for Pangasius sp. aquaculture in Mekong Delta (Viet Nam) are assessed and the importance of home-made feeding is highlighted. Farmers spend 5% production cost for disease prevention, mainly antibiotics for prophylactic and therapeutic treatments. Therefore, the study aims to analyse the resistance of Wsh bacteria to antibiotics to help them improve their practices. Bacteria isolated from catWsh (n D 92) were arbitrarily-selected from 3 diVerent Wsh farms to analyse their antibiotic resistance and evaluate the antibiotic pressure exerted on the surrounding environment. Antimicrobial susceptibility was examined for selected isolates against 6 major antibiotics using the agar diVusion method: oxytetracycline, chloramphenicol, trimethoprim-sulphamethoxazole, nitrofu- rantoin, nalidixic acid, and ampicillin. The predominant bacterial microXora consisted of members of the Enterobacteriaceae (49.1%), Pseudomonads (35.2%) and Vibrionaceae (15.7%) families. The main multiple antibiotic resistance proWles included AM-OTC-SXT-NA (17.8% of isolates), OTC-SXT-NA (15.1%), AM-C-FT-SXT-NA (13.7%), AM-FT-OTC (9.6%), AM-C-FT-OTC-SXT-NA (8.2%). MAR index values of the 3 farms ranged from 0.36 to 0.62 which indicates a high-risk exposed-antibiotic source. These results showed that antibiotic resistance among Wsh indigenous bacteria is of a high concern in catWsh aquaculture in the Mekong River Delta.  2006 Elsevier Ltd. All rights reserved. Keywords: Pangasius catWsh; Feeding; Antibiotic resistance 1. Introduction In 2002, Asia accounted for 91.2% of the aquaculture production quantity, which averaged 35 496 000 tons (SOFIA, 2004). The impact of the intensive use of antimi- crobial agents worldwide for prophylactic and therapeutic purposes has been associated with the increase of bacterial resistance in the exposed microbial environment. Currently, multiple antibiotic resistance has been reported in a wide range of human pathogenic or opportunistic bacteria such as Campylobacter sp. (Randall et al., 2003), Klebsiella pneu- moniae (Carneiro, Silva, Merquior, & Queiroz, 2003), Salmonella sp. (Randall, Cooles, Osborn, Piddock, & Woodward, 2004), Pseudomonas aeruginosa (Ziha-ZariW, Llanes, Köhler, Pechere, & Plesiat, 1999), and also in Wsh pathogens (Schmidt, Bruun, Larsen, & Dalsgaard, 2001; Teuber, 2001). Reservoirs of antibiotic resistance can inter- act between diVerent ecological systems and potential transfer of resistant bacteria or resistant genes from ani- mals to humans may occur through the food chain (Teuber, 2001; van den Bogaard & Stobberingh, 2000; Witte, 2000). In view of this and because of their broad environmental distribution, indigenous Wsh microXora are likely important reservoirs to be considered. To ensure a proper use of antibiotics, standards and methods are developed to monitor and control their residual * Corresponding author. Tel.: +33 4 67 61 58 00x5355; fax: +33 4 67 61 55 15. E-mail address: samira.sarter@cirad.fr (S. Sarter).