Chapter X E. coli in Urban Water
X. 4. Control Techniques
X.4.2. Advanced treatment
Advanced treatments aim at improving the quality of the secondary effluent before of disposal or reuse. Sand filtration, adsorption, membranes and advanced oxidation processes are among the most applied and studied advanced treatment processes/technologies. Despite a lot of available studies regarding the effect of advanced treatment technologies on bacteria inactivation [33], these processes have not been well documented yet for the control of gne etransfer for antibiotic resistance control. This section focuses mainly on innovative processes such as advanced oxidation processes and nanoparticules/nanocomposites
14
adsorption which have been found effective for inactivation of both E coli bacteria and and genes provoking E coli growth. Main outlines of those processes are given in Figure 6.
Insert Figure 6 here.
X.4.2.1. Inactivation of E. coli by Advanced oxidation proesses
Cengiz et al. [11], compared Fenton and ozone oxidation processes in the removal of tetM gene and its host E. coli HB101 from synthetically contaminated cow manure, PCR-based monitoring assays showed that the band intensity of the tetM gene gradually decreased by increasing the Fenton reagent and the applied ozone dose.
Ozonation and TiO2 heterogeneous photocatalysis were compared with conventional chlorination in terms of effects on DNA structure and integrity [35]. They reported that chlorine did not affect plasmid DNA structure at the studied doses. Ozone and photocatalytic treatment resulted in increased damage with increasing oxidant doses.
A different approach was used by Paul et al. [36], to evaluate the effects of photolytic and TiO2 photocatalytic treatment processes on the antibacterial activity of ciprofloxacin. In particular, quantitative microbiological assays with a reference E. coli strain showed that for each mole of ciprofloxacin degraded, the antibacterial potency of irradiated solutions
decreased by approximately one “mole” of activity relative to that of the untreated ciprofloxacin solution. The authors inferred that the ciprofloxacin photocatalytic transformation products retain negligible antibacterial activity compared to the parent compound. Moreover, according to their experimental system the lower energy demand (20 J/cm2) to reduce antibacterial activity by one order of magnitude was achieved by UVA-TiO2
15
photocatalysis. Table 3 compares slurry and thin film based stuides for inactivation of E coli and genes.
Insert Table 3 here.
X.4.2.2. Nanoparticles
Among different their functions, nanoparticles can overcome drug resistance mechanisms of microbes, including decreased uptake and increased efflux of drug from the microbial cell [20, 53] biofilm formation and intracellular bacteria [6, 20]. Nanoparticles have been used to target antimicrobial agents to the site of infection, so that higher doses of drug can be given at the infected site, thereby overcoming resistance with fewer adverse effects upon the patient [28]. The main group of nanoparticules applied as antimicrobial agent have been revised by Pelgrift et al. [37], and shown schematically in Figure 6. The mode of actions and application fileds of most commonly used nanoparticules for bacteria control are given in Table 4.f
Insert Table 4 here
4.3. Disinfection
Many factors must be considered in order to develop and implement treatment systems to improve the microbial quality of surface water and prevent the accidental introduction of plant and human pathogens into vegetable crops. The most applied disinfection process in wastewater treatment is chlorination, but UV radiation also finds extended applications.
Germicidal effects of chlorine (as chlorine gas or hypochlorites) include the following mechanisms: oxidizing the germ cells, altering cell permeability, altering cell protoplasm, inhibiting enzyme activity and damaging the cell DNA and RNA. Chlorine appears to react
16
strongly with the lipids of the membrane and the membranes that have high lipid
concentrations appear to be more susceptible to destruction. The predominant disinfection mechanism depends on the microorganism (the resistance of a particular strain), the
wastewater characteristics and chlorine dose. Unfortunately, bacteria injured by disinfection process can survive and re-grow at low chlorine doses. UV radiation can also damage DNA, resulting in inhibition of cell replication and, in case of lethal doses, in a loss of
reproducibility. The effectiveness of a UV disinfection system depends on the characteristics of the wastewater, the intensity of UV radiation (optimum wavelength to effectively inactivate microorganisms is 250–270 nm), the time the microorganisms are exposed to the radiation and the reactor configuration [34]
Antibiotic resistant E. coli and other coliforms were investigated in an UWTP in Tokyo Metropolitan Prefecture [22]. E. coli strains, randomly isolated from wastewater samples, were tested for their sensitivity to seven antimicrobial agents in three different UWTP
locations: the inflow, before chlorination and after chlorination. Chlorination treatment did not significantly affect the percentage of resistance in E. coli to one or more antibiotics (from 14.7 to 14.0%) or specifically to ampicillin (constant at 7.3%) and tetracycline (from 8.0 to 6.7%).
Templeton et al. [47], investigated the effect of free chlorine and ultraviolet (UV intensity 0.247 mW/cm2) disinfection on E. coli strains resistant to ampicillin and trimethoprim, in comparison to an antibiotic-susceptible strain of E. coli isolated from sewage sludge.
Trimethoprim-resistant E. coli was found to be slightly more resistant to chlorine than the antibiotic-susceptible isolate and the ampicillinresistant E. coli, under the studied conditions (95% confidence).Moreover, no statistically significant differences between the UV dose–
17
response profiles of the antibiotic-resistant and antibiotic-susceptible E. coli strains over the UV dose range tested were observed.
When 2.0 mg/ L chlorine dose was used to investigate the inactivation of multi-drug resistant E. coli strains selected from an UWTP effluent, the number of colonies decreased by 99.999%
after 60 min of contact time [41]. However, the minimum inhibitory concentration to the antibiotics amoxicillin, ciprofloxacin and sulfametoxazole was not altered for the surviving cultures.
Ivey et al. [21], evaluated the efficacy of chlorine gas (Cl2(g)) and chlorine dioxide (ClO2) injection systems in combination with rapid sand filtration (RSF) in killing fecal indicator microorganisms in irrigation water in a vegetable intensive production area. Sampling date and sampling point also had a significant effect on the abundance of generic E. coli in Cl2(g) treated water but only sampling point was significant in ClO2 treated water. Accordingly injection of ClO2 and Cl2(g) into surface water prior to rapid sand filtration is inadequate in reducing fecal indicator microorganism populations and ClO2 ineffectively kills infectious propagules of P.capsici.
5. Conclusions
Escherichia coli has been globally spread antibiotic resistant bacria to many antibiotics.
Recent surveilence reports showed that the data banks for occuerence of E coli are growing and this will help to map this inforation for more effective control of outbreaks and resistance.
18
The origin and ptahways of E coli to homan contact are clear and among these sources Urban water is to deal with accurately to protect human and enironental health. This work outlines the following issues for Urban water safety:
-Conventional UWTPs may positively affect ARB spread and selection as well as ARG transfer.
-All known types of antibiotic resistance mechanisms are represented in UWTP, suggesting the relevance of these facilities as reservoirs and environmental suppliers of genetic
determinants of resistance.
-Advanced oxidation processes such as ozone, UV, photocatalysis seem to be very effective for bacteria inactivation. However reactivation is not to be ignored and a final disinfection seems unavoidable for long term safety.
- Effect of conventional (e.g., chlorination and UV radiation) and new/alternative disinfection processes on the inactivation of specific ARB as well as the capacity to control resistance spread into the environment are strongly recommended because the few studies available show that, despite an effective decrease of the total number of bacteria, they may
simultaneously promote the selection of ARB.
6.Acknowledgement
This work has been performed in the context of Research and Development Fund of NKU (NKUBAP.00.17.AR.13.13).
19
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Figure 1. Contact routes of E. coli with human
27
Human being
Figure 2. Pathways of E. coli contamination from contaminated water origin
28
Figure 3a. Trend and number of confirmed cases of STEC/VTEC reported in the EU/EEA, 2007–2011 [17]
Figure 3b. Rates of confirmed STEC/VTEC cases reported in the EU/EEA, by age and gender, 2011 [17]
29
Figure 3c. Seasonal distribution: Number of confirmed cases of STEC/VTEC by month, EU/EEA, 2007–2011 [17]
Figure 3d. Number of confirmed STEC/VTEC HUS cases, by age and most common O-serogroups, 2011 [17]
30
Figure 4. Escherichia coli: percentage (%) of invasive (blood and cerebrospinal fluid) isolates resistant to thirdgeneration cephalosporins, EU/EEA, 2011 (EU Surveilence <report, 2013) [17]
31
Figure 5. Examples for presence of E. coli resistant to antibiotis treated in biologial treatment
32
Figure 6. Advenced oxidation prosesses used for inactivation of E coli and genes 33
Table 1. E coli surveilance in the World (Adopted from WHO [51]) Resistance to third-generation cephalosporinsa
(summary of reported or published proportions of resistance, by WHO region)
Resistance to fluoroquinolonesa
Data sources based on at least 30 tested isolatesb in invasive isolatesc (no.
of reports)
Data sources based on at least 30 tested isolatesb in invasive isolatesc (no.
of reports) African Region
– National data (n=13 countries)
Region of the Americas – National data or
report to ReLAVRA (n=14 countries)
0-48 National data or report
to ReLAVRA (n=16 countries)
8–58
– Publications (n=10) from 5 additional ountries
0-68 – Publications (n=5)
from 4 additional countries
2–60
Eastern Mediterranean Region – National data (n=4
countries)
22-63 41 (n=1) National data (n=4
countries)
21–62 54 (n=1)
– Surveillance network in 1 countryd
39 (caz)–50 (cro) – Surveillance
networkd, one additional country
35
– Publications (n=44) 2-94 11–33 (n=6) – Publications (n=32) 0–91 15–53 (n=5)
35
from 11 additional countries
from 10 additional countries
European Region – National data or
report to EARS-Net (n=35 countries)
3-82 3–43 (n=32) – National data or report to EARS-Net (n=35 countries)
8–48 8–47 (n=33)
– Publications (n=5) from 2 additional countries
0-8 0-8 (n=2) – Publications (n=3)
from 2 additional countries
0–18 0–18 (n=2)
South-East Asia Region – National data (n=5
countries)
16–68 – National data (n=5
countries)
32–64
– Publications (n=26) from 2 additional
19–95 20–61 (n=2) – Publications (n=19) from 2 additional
4–89
36
countries countries Western Pacific Region – National data (n=13
countries)
0–77 – National data (n=16
countries)
3–96 7 (n=1)
– Institute surveillance (data from 3 hospitals in one country)
4–14 – Institute surveillance
(data from 3 hospitals in 1 country)
0–14
– Publications (n=4) from 2 additional countries
8–71 – Publications (n=5)
from 3 additional counties
0.2–65 31 (n=1)
EARS-Net, European Antimicrobial Resistance Surveillance Network;
ReLAVRA, Latin American Antimicrobial Resistance Surveillance Network. (For
details see Annex 2, Tables A2.1–A2.6).
EARS-Net, European Antimicrobial Resistance Surveillance Network;
ReLAVRA, Latin American Antimicrobial Resistance Surveillance Network (For
details see Annex 2, Tables A2.7–A2.12).
37
a. Based on antibacterial susceptibility testing with caz, ceftazidim;
cefotaxim or cro, ceftriaxone
b. Reported proportions may vary between compound used for testing and some countries report data for several compounds, or data from more than one surveillance system.
c. Invasive isolates are deep infections, mostly bloodstream infections and meningitis.
d. US Naval Medical Research Unit No 3, Global Disease Detection Program, Egypt.
a. Based on antibacterial susceptibility testing with ciprofloxacin, gatifloxacin, levofloxacin, moxifloxacin, norfloxacin, ofloxacin,
pefloxacin, refloxacin or sparfloxacin. Where the fluoroquinolone was not specified, ciprofloxacin was used.
b. Reported proportions may vary between compound used for testing and some countries report data for several compounds, or data from more than one surveillance system.
c. Invasive isolates are deep infections, mostly bloodstream infections and meningitis.
d. US Naval Medical Research Unit No 3, Global Disease Detection Program, Egypt.
38
Table 2. Mitigation strategies to control pathogens in the Enrviornment (Adopted from [50]) Control point Mitigation strategies
Wastewater treatment
• Reduced microbial pollution, the present best practice in
wastewater treatment (UV treatment). Only undertaken in so-called sensitive areas.
• Dedicated hospital wastewater treatment.
• Adoption of new technologies to remove pharmaceuticals from wastewater such as ozonation and membrane technology.
• Further investment in wastewater system to reduce combined storm overfl ow discharges of raw sewage.
Farming • Observe best practice in reducing livestock access to water courses. Implementation of buffer zones to reduce run-off .
• Treatment of animal wastes to reduce microbial pollution.
• Reduction in antibiotic use in agriculture—prophylactic use supporting unsustainable farming practice. Use alternative therapies where possible (probiotics).
Medical • Ensure best practice in prescription of antibiotics, use alternative therapies such as bacteriophage or probiotics where possible.
• Green drug choice: use of degradable pharmaceuticals rather than environmentally persistent compounds.
• Ethical procurement: purchase from sources not polluting the environment with pharmaceuticals.
39
Table 3. Removal of E coli by TiO2 based photocatalysis process
Reference Reactor Strain Time (h) Light emission TiO2
Matsunaga and Okochi [30] Suspended system 2 69 mEinstein/s.m2 0.4 mg/L
Bekbölet [4] Suspended system HB 1001
(103 cells /mL)
1 67.9 µEinstein/s.m2) 1 mg/mL
Oller et al. [32] full-scale continuous flow solar Parabolic and
V-grove reactors
V-grove reactors