By IDSE News Staff
Marine bacteria in coastal waters appear to be developing resistance to several commonly used antibiotics, including ofloxacin, clindamycin and clarithromycin, according to a presentation at ASM Microbe 2024, held in Atlanta.
They found 70% of marine bacteria had developed resistance to ofloxacin, 95% to clindamycin, 58% to clarithromycin and 100% to novobiocin. The study found more resistance among bacteria in seawater samples collected from the sea surface microlayer than from the water below, even when different amounts of the antibiotic ciprofloxacin were added to the samples.
As would be expected, when the level of ciprofloxacin increased, the number of bacteria in seawater samples decreased, at least initially. However, over time, the bacteria in seawater samples started to grow even with high levels of ciprofloxacin (50 and 100 ng mL-1), which shows that they were becoming resistant, according to Adenike Adenaya, PhD, at the Carl von Ossietzky University of Oldenburg, in Germany.
In the presence of high levels of ciprofloxacin, the researchers found 97 strains of bacteria distributed over 14 bacterial genera. Fifty-seven could cause infections in humans, especially those with weakened immune systems, while 40 are marine bacteria that do not infect people. The team also found many antibiotics, including ofloxacin, clindamycin, clarithromycin, lincomycin, tylosin, novobiocin, erythromycin, trimethoprim, sulfamethoxazole, roxithromycin and chloramphenicol present in the seawater samples, particularly in those collected from the sea surface microlayer of Jade Bay.
However, they found only a few bacterial strains in the water below.
“Our results emphasize the collective effort needed to reduce the potential ecological effects of introducing antibiotics into coastal waters because antibiotics may accumulate more in the sea surface microlayer, affect the bacteria diversity, and lead to the adaptation of marine bacteria to antibiotics,” Dr. Adenaya said.
