Prevalence and abundance of antibiotic-resistant genes in culturable bacteria inhabiting a non-polar passu glacier, karakorum mountains range, Pakistan

Natural pristine environments including cold habitats are thought to be the potent reservoirs of antibiotic-resistant genes and have been recurrently reported in polar glaciers’ native bacteria, nevertheless, their abundance among the non-polar glaciers’ inhabitant bacteria is mostly uncharted. Herein we evaluated antibiotic resistance profile, abundance of antibiotic-resistant genes plus class 1, 2, and 3 integron integrases in 65 culturable bacterial isolates retrieved from a non-polar glacier. The 16S rRNA gene sequencing analysis identified predominantly Gram-negative 43 (66.15%) and Gram-positive 22 (33.84%) isolates. Among the Gram-negative bacteria, Gammaproteobacteria were dominant (62.79%), followed by Betaproteobacteria (18.60%) and Alphaproteobacteria (9.30%), whereas Phyla Actinobacteria (50%) and Firmicutes (40.90%) were predominant among Gram-positive. The Kirby Bauer disc diffusion method evaluated significant antibiotic resistance among the isolates. PCR amplification revealed phylum Proteobacteria predominantly carrying 21 disparate antibiotic-resistant genes like; bla AmpC 6 (100%), bla VIM-1 , bla SHV and bla DHA 5 (100%) each, bla OXA-1 1 (100%), bla CMY-4 4 (100%), followed by Actinobacteria 14, Firmicutes 13 and Bacteroidetes 11. Tested isolates were negative for bla KPC, qnrA , vanA , ermA , ermB, intl2 , and intl3 . Predominant Gram-negative isolates had higher MAR index values, compared to Gram-positive. Alignment of protein homology sequences of antibiotic-resistant genes with references revealed amino acid variations in bla NDM-1 , bla OXA-1 , bla SHV, mecA, aac(6)-Ib3, tetA , tetB, sul2 , qnrB, gyrA , and intI1 . Promising antibiotic-resistant bacteria, harbored with numerous antibiotic-resistant genes and class 1 integron integrase with some amino acid variations detected, accentuating the mandatory focus to evaluate the intricate transcriptome analysis of glaciated bacteria conferring antibiotic resistance. Graphical abstract