Isolation and Characterization of Metal and Antibiotic Resistant Psychrotrophic Bacteria from Refrigerated Spoiled Food

The aim of this study was to isolate and characterize psychrotrophic bacteria resistant to antibiotic and metals from cold samples of refrigerated spoiled food and ice. Two isolates named H and F were successfully isolated from samples incubated at 10°C and 4°C, respectively. Both isolates were able to grow at 4°C, 10°C, 20°C and 30°C and exhibited multidrug resistance to antibiotics (chloramphenicol, ampicillin, tetracycline and kanamycin). Bacteria H and F were then further tested for their resistance to metal ions such as Cd^2+, Zn^2+, Cr^6+ and As^3+ at concentrations ranging from 0-10 mM. The results of the test revealed that the minimum inhibitory concentration (MIC) for isolate H was determined at 2 mM for all the metal ions. By comparison, isolate F was highly resistant to Cr^6+, Cd^2+ and Zn^2+ with MIC of 10 mM for these cations, while MIC for As^3+ was 4 mM. 16S rRNA analysis revealed that isolate F shares a 98% identity match to Bacillus sp. This strain could be used as a model microbial strain to understand the mechanisms of metal resistance and as a source of psychrotrophic enzymes with potential application for bioremediation of heavy metals in cold environments.