Plasmids carried by antibiotic-resistant marine bacteria

Area of Science:

• Environmental Microbiology
• Marine Biology
• Antimicrobial Resistance

Background:

• Antibiotic resistance is a growing global health concern.
• The presence and spread of antibiotic-resistant bacteria (ARB) in marine environments are not fully understood.
• Marine ecosystems may serve as reservoirs and pathways for the dissemination of ARB.

Purpose of the Study:

• To investigate the prevalence and characteristics of antibiotic-resistant bacteria in Atlantic Ocean seawater.
• To determine the distribution of ARB in relation to proximity to shore and depth.
• To assess the potential for horizontal gene transfer of antibiotic resistance in marine bacteria.

Main Methods:

• Isolation and enumeration of bacteria from seawater and sediment samples collected offshore and inshore.
• Determination of antibiotic resistance profiles for isolated bacterial strains.
• Characterization of autochthonous marine bacteria, including plasmid analysis using ethidium bromide-cesium chloride density sedimentation.

Main Results:

• High numbers of ARB were detected in both inshore and offshore Atlantic Ocean waters.
• ARB resistant to tetracycline, chloramphenicol, and streptomycin were ubiquitous, found even 200 miles offshore and at depths of 8,200 m.
• Sediment samples generally contained lower populations of resistant strains compared to seawater.
• Several marine isolates displayed unstable antibiotic resistance transferable to Escherichia coli, with 6 out of 10 strains containing plasmid DNA.

Conclusions:

• The Atlantic Ocean, even remote offshore regions, harbors significant populations of antibiotic-resistant bacteria.
• Marine bacteria possess transferable antibiotic resistance, potentially mediated by plasmids, highlighting environmental dissemination risks.
• Further research is needed to understand the ecological and public health implications of ARB in marine environments.