Antibiotic resistance in bacterial isolates from freshwater samples in Fildes Peninsula, King George Island, Antarctica

Abstract

Anthropic activity in Antarctica has been increasing considerably in recent years, which could have an important impact on the local microbiota affecting multiple features, including the bacterial resistome. As such, our study focused on determining the antibiotic-resistance patterns and antibiotic-resistance genes of bacteria recovered from freshwater samples collected in areas of Antarctica under different degrees of human influence. Aerobic heterotrophic bacteria were subjected to antibiotic susceptibility testing and PCR. The isolates collected from regions of high human intervention were resistant to several antibiotic groups, and were mainly associated with the presence of genes encoding aminoglycosides-modifying enzymes (AMEs) and extended-spectrum β-lactamases (ESBLs). Moreover, these isolates were resistant to synthetic and semi-synthetic drugs, in contrast with those recovered from zones with low human intervention, which resulted highly susceptible to antibiotics. On the other hand, we observed that zone A, under human influence, presented a higher richness and diversity of antibiotic-resistance genes (ARGs) in comparison with zones B and C, which have low human activity. Our results suggest that human activity has an impact on the local microbiota, in which strains recovered from zones under anthropic influence were considerably more resistant than those collected from remote regions.

Figure 1

Sampling sites in Peninsula Fildes showing ARGs detected, antibiotic resistance index (ARI) and richness (Simpson Index) and diversity (Shannon Index) of genes in each area. Zone A: places under human influence M51, M52, M55, M56, M59, M60, M70; Zone B: places without human influence but with possible animal influence M41; and Zone C: remote places without human or animal intervention M15, M72, M74.

Figure 2

Percentage of antibiotic resistant strains in Antarctic areas. Antibiotics tested: ampicillin (AMP), cefalotin (CEF), cefuroxime (CXM), cefotaxime (CTX), ceftazidime (CAZ), cefepime (FEP), streptomycin (STR), kanamycin (KAN), amikacin (AMK), gentamicin (GEN), nalidixic acid (NAL), ciprofloxacin (CIP), tetracycline (TET), chloramphenicol (CHL). Antibiotics with p < 0.05 are indicated with (*).