Abstract
Seawater could be considered a reservoir of antibiotic-resistant bacteria and antibiotic resistance genes. In this communication, we evaluated the presence of bacterial strains in seawater collected from different coasts of Sicily by combining microbiological and molecular methods. Specifically, we isolated viable bacteria that were tested for their antibiotic resistance profile and detected both antibiotic and heavy metal resistance genes. Both antibiotic-resistant Gram-negative bacteria, Vibrio and Aeromonas, and specific antibiotic resistance genes were found in the seawater samples. Alarming levels of resistance were determined towards cefazolin, streptomycin, amoxicillin/clavulanic acid, ceftriaxone, and sulfamethoxazole/trimethoprim, and mainly genes conferring resistance to β-lactamic and sulfonamide antibiotics were detected. This survey, on the one hand, presents a picture of the actual situation, showing the pollution status of the Tyrrhenian coast of Sicily, and, on the other hand, can be considered as a baseline to be used as a reference time for future analysis.
Highlights
Antibiotic resistance is one of the biggest public health challenges in every country over the world [1,2]
The presence of these two genera in the coastal water of southern Italy was already assessed by other studies [6,21,23]. Their physiological characteristics make them a part of the autochthonous microflora of marine waters, with consequent contaminations of sediments and aquatic organisms, such as seafood and sea turtles [15,21]. The incidence of these two genera in our samples is in agreement with what was previously detected by Pace et al (2019) who report, in oral swabs of sea turtles in the Tyrrhenian coast of southern Italy, a higher incidence of Vibrio spp. (53.4%) in comparison with Aeromonas spp (17%) [15]
A study conducted on loggerhead sea turtle nesting samples recorded only Aeromonas spp. (55.6%) [24], while our group reported a prevalence of Aeromonas spp. (45.4%) compared with Vibrio spp. (9%) on the coastal water and sea turtles [6]
Summary
Antibiotic resistance is one of the biggest public health challenges in every country over the world [1,2]. The spread of antibiotic-resistant bacteria (ARB) in the environment is linked to the overuse and misuse of antibiotics, and their uncontrolled release into waste in many parts of the world. Together with ARB, it is currently quite common to find antibiotic resistance genes (ARGs) in the environment, as well as in those that have never experienced antibiotic treatment [3]. The presence of ARGs in soil and environmental bacteria represents a threat to human health, while horizontal gene transfer mechanisms contribute to the diffusion of resistance determinants in pathogenic bacteria [4]. Antimicrobial agents and pathogenic-resistant bacteria can access sewage through the waste released from these “hotspots”, reaching water ecosystems with the final effluent [5]. ARGs are frequently associated with gene cassettes containing the class
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