Environ Monit Assess (2010) 167:309–320 DOI 10.1007/s10661-009-1051-1 Aeromonas and Pseudomonas: antibiotic and heavy metal resistance species from Iskenderun Bay, Turkey (northeast Mediterranean Sea) Fatih Matyar · Tamer Akkan · Yasemin Uçak · Buse Eraslan Received: 27 November 2008 / Accepted: 11 June 2009 / Published online: 24 June 2009 © Springer Science + Business Media B.V. 2009 Abstract We studied the susceptibility patterns to 15 different antibiotics and six heavy metals in Aeromonas spp. and Pseudomonas spp. iso- lated from Iskenderun Bay, Turkey (northeast Mediterranean Sea). A high percentage of Aeromonas isolates showed resistance to cefazolin (66.6%) and trimethoprim–sulphamethoxazole (66.6%). Amongst the Pseudomonas isolates, there was a high incidence of resistance to nitrofurantoin (86.2%), cefazolin (84.8%) and cefuroxime (71.7%). Most isolates showed toler- ance to different concentrations of heavy met- als, and minimal inhibition concentrations ranged from 25 to >3,200 μg/ml. The Aeromonas spp. and Pseudomonas spp. showed high resistance to copper of 98.3% and 75.4%, respectively, and low resistance to lead of 1.7% and 7.2%, respec- tively. Our results show that antibiotic and heavy metal resistant Aeromonas spp. and Pseudomonas spp. were widespread in Iskenderun Bay in 2007 and 2008. The increasing presence of antibiotic F. Matyar (B ) · B. Eraslan Department of Science and Technology Education, Faculty of Education, Çukurova University, 01330 Balcalı, Adana, Turkey e-mail: fmatyar@cu.edu.tr T. Akkan · Y. Uçak Department of Biology, Faculty of Science and Letters, Çukurova University, 01330 Balcalı, Adana, Turkey and heavy metal resistant Aeromonas spp. and Pseudomonas spp. may become a potential human health hazard. Keywords Aeromonas · Pseudomonas · Antibiotic resistance · Heavy metal resistance · Human health Introduction Aquatic bacteria that are resistant to multiple antibiotics are of great importance in many areas of the world. Many aquatic bacteria are responsi- ble for various types of serious diseases; for this reason, they have been the focus of numerous studies (Calomiris et al. 1984; Messi et al. 2005; Lobova et al. 2008; Matyar et al. 2008). Hospitals discharge large quantities of untreated antibiotic wastes in to the environment, which has lead to an increase in bacteria having multiple antibiotic resistances (MARs) and to an increase in more virulent pathogens. Aeromonas spp., autochthonous inhabitants of aquatic environments, are widespread in nat- ural habitats such as soil, fresh and brackish water, sewage and wastewater (Araoju et al. 1991). These bacteria cause both gastrointesti- nal and, to a lesser extent, extra-intestinal in- fections in humans (Janda and Abbott 1998).