Metal and antibiotic resistance of bacteria isolated from the Baltic Sea

Abstract

The resistance of 49 strains of bacteria isolated from surface Baltic Sea waters to 11 antibiotics was analyzedand the resistance of selected strains to three metal ions (Ni2+, Mn2+, Zn2+) was tested. Most isolates belonged to Gammaproteobacteria (78 %), while Alphaproteobacteria (8 %), Actinobacteria (10 %), and Bacteroidetes (4 %) were lessabundant. Even though previous reports suggested relationships between resistance and the presence of plasmids or the abilityto produce pigments, no compelling evidence for such relationships was obtained for the strains isolated in this work. In particular, strains resistant to multiple antibiotics did not carry plasmids more frequently than sensitive strains. A relationbetween resistance and the four aminoglycosides tested (gentamycin, kanamycin, neomycin, and streptomycin), but not tospectinomycin, was demonstrated. This observation is of interest given that spectinomycin is not always classified as anaminoglycoside because it lacks a traditional sugar moiety. Statistical analysis indicated relationships between resistance tosome antibiotics (ampicillin and erythromycin, chloramphenicol and erythromycin, chloramphenicol and tetracycline, erythromycinand tetracycline), suggesting the linkage of resistance genes for antibiotics belonging to different classes. The effectsof NiSO4, ZnCl2 and MnCl2 on various media suggested that the composition of Marine Broth might result in low concentrationsof Mn2+ due to chemical interactions that potentially lead to precipitation. [Int Microbiol 2012; 15(3):131-139]