A statistical approach to determine co-existence of heavy metal and antibiotic resistance in environmental isolates of Khewra salt range, Pakistan

High concentration of heavy metals in the environment triggers metal resistance mechanisms and act as a driving force in the proliferation of antibiotic resistance in microorganisms thereby raising ecological and health concerns. Hypersaline soils are naturally augmented with heavy metals. In current study, nine halophilic bacteria i.e. Halomonas elongata MB590, H. elongata MB591, H. elongata MB593, H. elongata MB594 , H. elongata MB595, Halobacillus karajiensis MB588, Alkalibacillus almallahensis MB589, Aquisalibacillus elongatus MB592, and H. elongata MB596 were investigated for multiple heavy metal and antibiotic resistance patterns. These observations were further subjected to correlation as well as Principle Component Analysis (PCA) to identify the association between resistance of bacterial strains with respect to antibiotics and metals. All the isolates showed resistance to various antibiotics with Multiple Antibiotic Resistance (MAR) index above 0.2 for each strain. MAR and Multiple Heavy Metal Resistance (MHMR) indices revealed H. elongata MB593 as the most resistant strain to most of the heavy metals and antibiotics. Alkalibacillus almallahensis MB589 and A. elongatus MB592 were sensitive to all heavy metals and only isolate A. elongatus MB592 was found sensitive to most of the antibiotics. This MAR and MHMR in halophilic bacteria might be the consequence of a common mechanism they shared for antibiotic and heavy metal resistance. Correlation analysis between heavy metal and antibiotic resistance spectra of halophilic bacteria indicated strong association among heavy metal and antibiotic tolerance. This study provided a strong evidence for co-existence of heavy metal and antibiotic resistance in halophilic bacteria and gives insight for future study on the molecular basis of resistomes of these bacteria.