Antibacterial agents and heavy metal resistance in Gram-negative bacteria isolated from seawater, shrimp and sediment in Iskenderun Bay, Turkey Fatih Matyar a, ⁎ , Aysenur Kaya b , Sadık Dinçer b a Çukurova University, Faculty of Education, Department of Science and Technology Education, 01330 Balcalı, Adana, Turkey b Çukurova University, Faculty of Science and Letters, Department of Biology, 01330 Balcalı, Adana, Turkey ARTICLE DATA ABSTRACT Article history: Received 1 February 2008 Received in revised form 23 July 2008 Accepted 10 August 2008 Available online 19 September 2008 The aim of the present study was to determine the level of antibiotic resistance patterns and distribution of heavy metal resistance of bacterial isolates from seawater, sediment and shrimps, and to determine if there is a relationship between antibiotic and heavy metal resistance. We undertook studies in 2007 in the industrially polluted Iskenderun Bay, on the south coast of Turkey. The resistance of 236 Gram-negative bacterial isolates (49 from seawater, 90 from sediment and 97 from shrimp) to 16 different antibiotics, and to 5 heavy metals, was investigated by agar diffusion and agar dilution methods, respectively. A total of 31 species of bacteria were isolated: the most common strains isolated from all samples were Escherichia coli (11.4%), Aeromonas hydrophila (9.7%) and Stenotrophomonas maltophilia (9.3%). There was a high incidence of resistance to ampicillin (93.2%), streptomycin (90.2%) and cefazolin (81.3%), and a low incidence of resistance to imipenem (16.5%), meropenem (13.9%) and cefepime (8.0%). Some 56.8% of all bacteria isolated from seawater, sediment and shrimp were resistant to 7 or more antibiotics. Most isolates showed tolerance to different concentrations of heavy metals, and minimal inhibition concentrations ranged from 12.5 μg/ml to N 3200 μg/ml. The bacteria from seawater, sediment and shrimp showed high resistance to cadmium of 69.4%, 88.9%, and 81.1% respectively, and low resistance to manganese of 2%, 6.7% and 11.3% respectively. The seawater and sediment isolates which were metal resistant also showed a high resistance to three antibiotics: streptomycin, ampicillin and trimethoprim-sulphamethoxazole. In contrast, the shrimp isolates which were metal resistant were resistant to four antibiotics: cefazolin, nitrofurantoin, cefuroxime and ampicillin. Our results show that Iskenderun Bay has a significant proportion of antibiotic and heavy metal resistant Gram-negative bacteria, and these bacteria constitute a potential risk for public health. © 2008 Elsevier B.V. All rights reserved. Keywords: Antibiotic resistance Gram-negative bacteria Heavy metal Shrimp 1. Introduction Bacterial resistance to antibiotics is an emerging public health concern because of the wide availability of antibiotics and their improper usage without proper prescription (Davis and Amabile-Cuevas, 2003). In aquatic environments, the presence of antibiotic resis- tant pathogen bacteria belonging to the Enterobacteriaceae is of particular concern. Many antibiotics persist in the sedi- ment, and elsewhere in the aquatic environment, for several months following administration (Pouliquen and Le, 1996; Hirsch et al., 1999). Their residues may affect the microbial SCIENCE OF THE TOTAL ENVIRONMENT 407 (2008) 279 – 285 ⁎ Corresponding author. Tel.: +90 322 338 60 84 2789; fax: +90 322 338 68 30. E-mail address: fmatyar@cu.edu.tr (F. Matyar). 0048-9697/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2008.08.014 available at www.sciencedirect.com www.elsevier.com/locate/scitotenv