ANTIBIOTIC RESISTANCE GENES IN BLOOM FORMING CYANOBACTERIA

KUNZ, IE; MIÑO, ML; ZAPATA, PD; KOLMAN, MA

Chapadmalal

Congreso; XVIII Congreso de la Sociedad Argentina de Microbiologia General; 2023

Sociedad Argentina de Microbiologia General

Antibiotics are active biological molecules used to prevent and treat microbial infections. In Argentina, antibiotic usage for human infections increased by 39% from 2010 to 2020. Antibiotics can be found in freshwater and wastewater, impacting ecosystems and causing the development of antibiotic-resistant strains in prokaryotic microorganisms. The ecological risk in aquatic ecosystems is their impact in non-target microorganisms like cyanobacteria. These photosynthetic prokaryotes are primary producers in freshwater ecosystems, and some species can grow exponentially to produce blooms. During the past two decades, there has been a growing interest in investigating the influence of antibiotics on cyanobacteria and their contribution to the spreading of antibiotic resistance genes (ARGs). The aim of this study is to determine the prevalence of ARGs during bloom events and in isolates of cyanobacteria.Cyanobacterial bloom samples were collected from the Mártires and Zaimán streams, and the Paraná River (Posadas, Misiones). These samples were subjected to microscopic analysis to identify the presence of cyanobacteria, followed by isolation procedures to obtain monoalgal cultures. DNA from bloom samples and isolates was extracted and amplification of the mcyE was performed to assess the potential toxicity. Molecular identification of 5 isolated strains was made by amplifying the cpcBA intergenic spacer. The presence of one transposase gene and eight ARGs was analyzed by PCR. Antibiotic susceptibility to ampicillin, chloramphenicol and gentamicin was evaluated on BG11-agar and in liquid BG11 medium using antibiotic concentrations of 1, 10, 100 and 1000 μgL-1.Microscopic analysis confirmed the presence of Microcystis sp. in all bloom samples and amplification of the mcyE gene confirmed the potential production of microcystin. Three isolated strains were identified as Synechocystis sp. and two as Microcystis sp. The mcyE gene was detected by PCR only in the Synechocystis strains. Regarding the amplification of the tnpA gene (transposase) and ARGs, in environmental samples: tnpA, tetA, sul1, ermC, strA and qnrB genes were amplified, whereas in the isolated strains tnpA, tetA, sul1, ermC, blaTEM, qacH, and oprJ amplicons were obtained. Antibiotic sensibility test conducted on agar plates on two Synechocystis sp. strains revealed tolerance to chloramphenicol up to 1000 μgL-1, and for gentamicin and ampicillin up to 100 μgL-1. One Microcystis sp. strain was subjected to a sensibility test to gentamicin in a liquid medium and the growth inhibition effect was only detected at the maximal concentration.In conclusion, our study demonstrates the presence of ARGs in samples of cyanobacterial blooms as well as in the five isolated strains. This contributes to the understanding of environmental antimicrobial resistance and its connection with cyanobacterial blooms.