Prevalence of Antimicrobial Resistance and Hemolytic Phenotypes in Culturable Arctic Bacteria

Abstract

Many Arctic biomes, which are populated with abundant and diverse microbial life, are under threat: climate change and warming temperatures have raised concerns about diversity loss and possible emergence of pathogenic microorganisms. At present, there is little information on the occurrence of Arctic virulence-associated phenotypes. In this study we worked with 118 strains of bacteria (from 10 sampling sites in the Arctic region, located in Greenland and the Svalbard Archipelago) isolated using R2A medium. These strains belong to 4 phyla and represent 36 different bacterial genera. Phenotypic resistance to 8 clinically important antimicrobials (ampicillin, chloramphenicol, ciprofloxacin, cefotaxime, erythromycin, imipenem, kanamycin, and tetracycline) and thermotolerance range were determined. In addition, a screening of all isolates on blood agar media and erythrocytes suspension of bovine and sheep erythrocytes for virulence-linked hemolytic activity was performed. Although antimicrobial resistance profiles varied among the isolates, they were consistent within bacterial families and genera. Interestingly, a high number of isolates (83/104) were resistant to the tested concentration of imipenem (4 mg/L). In addition, one third of the isolates showed hemolytic activity on blood agar, however, in only 5% of the isolates hemolytic activity was also observed in the cell extracts when added to erythrocyte suspensions for 60 min. The observed microbial phenotypes contribute to our understanding of the presence of virulence-associated factors in the Arctic environments, while highlighting the potential risks associated with changes in the polar areas in the light of climate change.

First report on antibiotic resistance and antimicrobial activity of bacterial isolates from 13,000-year old cave ice core

“…Interestingly, the Phyllobacterium cave isolates from 700 and 7000-years old ice homologous to plants-associated species 68 , 69 could originate from the abundant vegetation above the cave 70 . Firmicutes strains belonging to Bacillus and Sporosarcina genera were retrieved from different Scarisoara ice strata, confirming the resilience of these genera in recent and old icy habitats 8 , 9 , 53 , 54 , 71 – 75 . The presence of Flavobacterium glaciei in 100-years old Scarisoara ice, previously reported in China No.1 glacier 76 , highlighted a wide geographical distribution of this psychrophilic species.…”

“…Most of the cave isolates with broad AR were Gram-negative belonging to Proteobacteria (6) and Bacteroidetes (1), while Arthrobacter psychrolactophilus SC7AB.1 isolated from 400-years old ice was resistant only to nalidixic acid and cefixime, (Supplementary Table S3 ). Although not specific for cold-habitats 81 , 82 , a high tetracycline susceptibility rate of the cave isolates was observed, also reported in Arctic bacteria 9 .…”

“…Most Scarisoara isolates exhibiting MDR and XDR phenotypes thrived in ice strata formed at least 1000-years ago. Bacterial strains with the broadest (PDR) resistance belonged to Pseudomonas species originating from 13,000-years old ice, similar to Arctic 9 and Antarctic 80 homologs.…”

“…To overcome the challenges of life in harsh conditions (nutrients scarcity, high salinity, dryness, and low water activity, high UV irradiation and oxidative stress at high altitudes, and high pressure in the deep sea) 4 , cold-adapted microorganisms have developed a wide range of adaptations, from cellular envelope (incorporation of unsaturated membrane fatty acids and carotenoid pigments, cell wall peptidoglycan layer, modified lipopolysaccharides of the outer cell membrane) and metabolic adaptation (antifreeze and ice-nucleating proteins, cold-active enzymes with increased structural flexibility, cold-inducible promotors, increased variety and number of tRNA species, multiple stress-responsive genes), to cryoprotectants (extracellular polymeric substances, biosurfactants, compatible solutes) and increased variety and number of chaperons production, and novel metabolic capabilities (microbial growth and multiplication possible at 0–30 °C, vitrification, storage materials such as polyhydroxyalkanoates and cyanophycins), that can be exploited to develop novel biotechnological perspectives 5 . Despite the constantly increasing data on the microbial composition and diversity in Polar ice sheets and glaciers 6 – 9 , Polar soil and permafrost 10 , 11 , and aquatic environments 12 , 13 , microbiomes entrapped in perennial ice from caves still remain a largely undiscovered life system 14 .…”

“…Due to their multiple physiological roles in natural environments, antibiotics acted as selecting and accelerating factors of AR evolution 32 , 38 , 39 . Bacterial strains highly resistant to known antimicrobial compounds usually have the potential for antimicrobial activity against other bacteria 9 .…”