TITLE:
Sensitivity of Planktonic Aquatic Bacteria to Ciprofloxacin
AUTHORS:
Brij Verma, David Verma
KEYWORDS:
Planktonic Bacteria, Aquatic, Antibiotics, Antibiotic Resistance, Ciprofloxacin, Thymidine Incorporation, Bacterial Production, DNA Production, DNA Inhibition
JOURNAL NAME:
Advances in Microbiology,
Vol.6 No.10,
August
26,
2016
ABSTRACT: Many anthropogenic compounds, such as antibiotics,
are found at trace levels (-1) in aquatic and terrestrial systems. The effect of
these compounds on the metabolism and function of microbes are difficult to
assess because the assays used, such as the minimum inhibitory concentration
(MIC) and the disk diffusion methods, lack the sensitivities to measure bacterial
response to these very low levels of antibiotics on bacterial populations.
Therefore, we theorized that the [3H] thymidine incorporation
into DNA method might be sensitive in determining the effect of DNA inhibiting antibiotics
on DNA production in planktonic bacteria in aquatic systems. Utilizing the 3H thymidine method, we measured the effects of ciprofloxacin on DNA
production on planktonic bacteria in river and pond waters. Ciprofloxacin
significantly (P -1 but significant inhibition (P -1in pond water. The very low concentration required
to inhibit DNA production in river water bacteria indicates that bacteria are
extremely sensitive to antibiotics at very low concentrations. A likely reason
for the differences in inhibition between the two waters is due to
ciprofloxacin becoming bound, and possibly becoming biologically inactive, in
the pond water due to higher dissolved organic carbon content. This work demonstrates
that bacteria in some aquatic systems can be significantly impacted by low
concentrations of anthropogenic antibiotics finding their way into these
systems and that our assumptions as to the concentrations at which antibiotics
affect microbes are highly underestimated.