3. Antibiotics and antibiotic-resistant bacteria are being detected in
many streams. One of the sources for antibiotic resistance in
streams is wastewater treatment plant (WWTP) effluent.
Incomplete elimination of bacteria and pharmaceutical drugs
during wastewater treatment results in the entry of antibiotics
and antibiotic-resistant bacteria into receiving streams with
effluent inputs.
Studies on antibiotic resistance of bacteria showed serious
results: mortality rates doubled in cases where resistant
infections were present; furthermore, length of treatments
increased
often requiring the use of more expensive antibiotics or
antibiotic cocktails (WHO, 2007).
Hence, the prevalence of antibiotic-resistant pathogens is
becoming a major public health issue.
4. Group I included exposure to penicillin, ampicillin, cephalothin or
chloramphenicol, while group II included tetracycline or rifampicin
exposures.
Total heterotrophic bacteria in group I decreased less than 50% when
exposed to antibiotic concentrations of 32mg/L.The curves remained
stable when the concentrations of these four antibiotics were between
16mg/L and 32mg/L.
However, there was an approximate 99% decrease in group II when
exposed to antibiotics at a concentration of 32mg/L. Hence, total
heterotrophic bacteria in the municipal wastewater effluent had a
higher tolerance to penicillin G, ampicillin, cephalothin and
chloramphenicol than to tetracycline and rifampicin.
5.
6. • Three devices were installed in house branch connections
of the distribution system. These sampling points were
supplied with bank-altered drinking water from the
waterworks and were located at a distance of 1^2 km from
the plant.
•Two sampling points were arranged in the wastewater
system of a hospital one downstream of the surgical
department and the other at the outlet of the clinical
wastewater system.
•Two biofilm sampling points were located in the municipal
sewage system.
• Antibiotics were added to the nutrient media to evaluate
the percentage of resistant bacteria by comparison with
plating experiments without any antibiotics in the media.
7. The enterococci/streptococci loads and the presence of
resistant bacteria were highest in hospital biofilms. Biofilms
from activated sludge at the municipal sewage treatment plant
showed slightly lower colony counts for enterococci/
streptococci. Another reduction in the biofilm load was
observed at the outlet end of the conditioned wastewater from
the plant.
8. UV doses required for ARG damage against those required
for bacterial inactivation, four model antibiotic resistant
pathogens of concern were selected: methicillin-resistant
Staphylococcus aureus (MRSA), vancomycin-resistant
Enterococcus faecium (VRE), multi-antibiotic resistant
Escherichia coli, and multi-antibiotic resistant
Pseudomonas aeruginosa.
The two former ARBs are Gram positive, whereas the two
latter are Gram negative. This provided insight into
potential shielding roles of the outer cell wall and envelope,
as did comparison of UV effects on intracellular versus
extracellular DNA.
9. The four specific ARGs selected: mecA, vanA, tet(A), and
ampC, respectively, provided a means to consider the
effect of UV as a function of DNA sequence
characteristics, both inside and outside the bacterial host
cell.
Finally, extended amplicon-length quantitative
polymerase chain reaction (qPCR) assays were developed
in order to enhance capture of DNA damage events and to
normalize to an equivalent DNA segment (~1000 bp),
which enabled comparison of DNA sequenceeffects. The
findings help assess the feasibility of UV disinfection of
water and wastewater for inactivating ARBs of particular
health concern and also controlling the dissemination of
their ARGs
10. Seven antibiotics - amoxicillin, ceftriaxone, amikacin,
ofloxacin, ciprofloxacin, norfloxacin and levofloxacin -
were selected.
Prescribed quantities were obtained from hospital records.
The samples of the hospital associated water were analysed
for the above mentioned antibiotics using well developed
and validated liquid chromatography/mass spectrometry
technique.
Escherichia coli isolates from these waters were tested for
antibiotic susceptibility.
11. E.coli antibiotic susceptibility study The estimation
of total coliform group and fecal coliform group was
done by determining the Most Probable Number
(MPN) of bacteria in test samples, using standard
multiple tube technique .
The results of prescription data are presented as the
total amount of antibiotics prescribed in milligrams
(mg) during the six days and number of defined daily
doses (DDDs).
The amount of antibiotic residue levels is presented
in μg/l. To determine the relationship between
quantities of antibiotic prescribed and antibiotic
residue levels obtained in hospital wastewater,
Spearman rank correlation was performed.
12. Ciprofloxacin was the highest prescribed antibiotic in the
hospital and its residue levels in the hospital wastewater were
also the highest. Although ciprofloxacin was the most prevalent
antibiotic detected in the wastewater, E.coli was not resistant to
it.
In samples of the municipal water supply and the groundwater,
no antibiotics were detected. There was a positive correlation
between the quantity of antibiotics prescribed in the hospital and
antibiotic residue levels in the hospital wastewater.
Wastewater samples collected in the afternoon contained both a
higher number and higher levels of antibiotics compared to
samples collected in the morning hours.
No amikacin was found in the wastewater, but E.coli isolates
from all wastewater samples were resistant to amikacin.
