title: Antibiotic resistance of Gram-negative benthic bacteria isolated from the sediments of Kardzhali Dam (Bulgaria).
abstract: The aim of the present study was to carry out a preliminary assessment for the occurrence of bacterial strains resistant to frequently used antibiotics in the sediments beneath the sturgeon cage farm in Kardzhali Dam (Bulgaria). Samples were taken from the top 2 cm of sediments under a fish farm and from a control station in the aquatory of the reservoir in the period July-October 2011. Surveillance of bacterial susceptibility to 16 antimicrobial agents was performed for 160 Gram-negative strains (Pseudomonas mandelii- 100 strains;Hafnia alvei- 30 strains; andRaoultella ornithinolytica- 30 strains). No significant differences in the resistance to the tested antibiotics were observed between the strains isolated from the two stations (analysis of variance,P> 0.05). Widespread resistance to penicillins and certain cephalosporin antibiotics was observed in both stations. None of the studied strains showed resistance to the aminoglycoside antibiotics gentamicin and amikacin, or to ciprofloxacin. Minimal Inhibitory Concentrations (MIC) were determined for five of the tested antimicrobial agents by the microdilution antibiotic sensitivity assay. The data indicate that amikacin, tetracycline and ciprofloxacin effectively suppress the growth of the tested micro-organisms. The isolates from genusPseudomonasshowed the highest MIC and were characterized by the highest percentage of antibiotic resistance.
authors.affiliation: Department of Biochemistry and Microbiology, Faculty of Biology, University of Plovdiv "Paisii Hilendarski" , Plovdiv , Bulgaria.
authors.forename: Ivan
authors.initials: I
authors.lastname: Iliev
authors.affiliation: Department of Biochemistry and Microbiology, Faculty of Biology, University of Plovdiv "Paisii Hilendarski" , Plovdiv , Bulgaria.
authors.forename: Mariana
authors.initials: M
authors.lastname: Marhova
authors.affiliation: Department of Biochemistry and Microbiology, Faculty of Biology, University of Plovdiv "Paisii Hilendarski" , Plovdiv , Bulgaria.
authors.forename: Velizar
authors.initials: V
authors.lastname: Gochev
authors.affiliation: Department of Biochemistry and Microbiology, Faculty of Biology, University of Plovdiv "Paisii Hilendarski" , Plovdiv , Bulgaria.
authors.forename: Marinela
authors.initials: M
authors.lastname: Tsankova
authors.affiliation: Department of Biochemistry and Microbiology, Faculty of Biology, University of Plovdiv "Paisii Hilendarski" , Plovdiv , Bulgaria.
authors.forename: Sonya
authors.initials: S
authors.lastname: Trifonova
keywords: Gram-negative microflora; antibiotic resistance; fish farm; sediments