Monitoring and comparison of antibiotic resistant bacteria and their resistance genes in municipal and hospital wastewaters

Human exposure to antibiotic resistant
bacteria (ARB) is a public health concern which could occur in a
number of ways. Wastewaters seem to play an important role in the
dissemination of bacteria and antibiotic resistant genes (ARGs)
in our environment. The aim of this study was to evaluate the
occurrence of three groups of ARB and their resistance genes in
hospital and municipal wastewaters (MWs) as possible sources.
Methods: A total of 66 samples were collected from raw MWs
and hospital wastewaters (HWs) and final effluents of related
wastewater treatment plants (WWTPs). Samples were analyzed for
the detection of three groups of ARB including gentamicin (GM),
chloramphenicol (CHL) and ceftazidime resistant bacteria and
their ARGs (aac (3)‑1, cmlA1 and ctx‑m‑32, respectively).
Results: The mean concentration of GM, CHL and ceftazidime
resistant bacteria in raw wastewater samples was 1.24 × 107,
3.29 × 107and 5.54 × 107 colony forming unit/100 ml, respectively.
There is a variation in prevalence of different groups of ARB
in MWs and HWs. All WWTPs decreased the concentration of
ARB. However, high concentration of ARB was found in the
final effluent of WWTPs. Similar to ARB, different groups of
ARGs were found frequently in both MWs and HWs. All genes
also detected with a relative high frequency in effluent samples of
MWs WWTPs.
Conclusions: Discharge of final effluent from conventional
WWTPs is a potential route for dissemination of ARB and ARGs
into the natural environment and poses a hazard to environmental
and public health