Removal of Amoxicillin and Sulfanomide by Freshwater Bacteria in Sri Lanka

Abstract

Antibiotics are an important group of pharmaceuticals used in human and animal health care.
Most of the antibiotics are prone to release to the environment due to improper usage. This
has resulted in bacterial resistance development and toxicity in aquatic communities. Present
study reports the biodegradation of amoxicillin (AMX) and sulfanomide (SUF) by Bacillus
cereus, Enterobacter ludwigii and Enterobacter sp. strains which were previously reported as
crude oil degraders. Different concentrations of AMX and SUF (0, 60, 120, 180, 240, 300,
360, 420 ppm) were used to detect minimum inhibition concentration (MIC) by standard pour
plate method. AMX and SUF degradation kinetics were studied by introducing 0.5 ml of
overnight starved bacterial suspensions into sterile antibiotic medium in triplicate at final
concentration of 60 and 120 ppm respectively. The samples were incubated at 280 C shaking
at 100 rpm and 0.5 ml sub-sample aliquots were removed at two days interval for a period of
14 days. Analyses of antibiotics were performed by high performance liquid chromatography
(HPLC). The MIC values for SUF and AMX were detected as 240, 420 ppm for B. cereus,
120, 360 ppm for E. ludwigii and 180 and 300 ppm for Enterococcus sp. respectively. After
14 days of incubation complete removal of AMX and 80% degradation of SUF was recorded
by bacterium B. cereus. E. ludwigii showed 75% degradation of AMX and 60% degradation
of SUF where Enterobacter sp. showed degradation of both AMX (80%) and SUF (70%)
respectively. Thus, the present study illustrate antibiotics degradation potential of microbial
community is important to understand their role in removal of antibiotics from the natural
environment.
Keywords: Biodegradation, Minimum Inhibitory Concentrations (MICs), Amoxicillin,
Sulfanomide, Bacillus cereus, Enterobacter ludwigii, Enterobacter sp.