scholarly journals Plasmid-mediated multiple antibiotic resistance of Escherichia coli in crude and treated wastewater used in agriculture

2009 ◽  
Vol 7 (2) ◽  
pp. 251-258 ◽  
Author(s):  
S. Pignato ◽  
M. A. Coniglio ◽  
G. Faro ◽  
F. X. Weill ◽  
G. Giammanco
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Treated Wastewater ◽  
Resistant Bacteria ◽  
Multiple Antibiotic Resistance ◽  
Reclaimed Wastewater ◽  
Salmonella Spp ◽  
Antibiotic Resistant ◽  
E Coli ◽  
R Plasmids

A total of 273 Escherichia coli isolates from raw and treated municipal wastewaters were investigated to evaluate the frequency and persistence of antibiotic resistance and to detect the occurrence of conjugative R plasmids and integrons. The highest resistance rates were against ampicillin (22.71%), tetracycline (19.41%), sulfamethoxazole (16.84%) and streptomycin (14.28%). Multiple antibiotic resistance was present in 24.17% of the isolates. Several multiple antibiotic-resistant isolates proved to be able to transfer en bloc their resistance patterns by conjugative R plasmids with different molecular sizes and restriction profiles. Class 1 integrons of 1 or 1.5 kbp were found in 5 out of 24 representative multiresistant E. coli isolates. Although wastewater treatments proved to be effective in eliminating Salmonella spp. and in reaching WHO microbiological standards for safe use of wastewater in agriculture, they were ineffective in reducing significantly the frequency of plasmid-mediated multiple antibiotic resistance in surviving E. coli. Since multiple antibiotic-resistant bacteria carrying integrons and conjugative R plasmids can constitute a reservoir of antibiotic-resistance genes in wastewater reclaimed for irrigation, risks for public health should be considered. Bacterial strains carrying R plasmids and integrons could contaminate crops irrigated with reclaimed wastewater and transfer their resistances to the consumers' intestinal bacteria.

scholarly journals Antibiotic-resistant Escherichia coli and Salmonella spp. associated with dairy cattle and farm environment having public health significance

2019 ◽  
Vol 12 (7) ◽  
pp. 984-993 ◽  
Author(s):  
Md. Abdus Sobur ◽  
Abdullah Al Momen Sabuj ◽  
Ripon Sarker ◽  
A. M. M. Taufiqur Rahman ◽  
S. M. Lutful Kabir ◽  
...  
Keyword(s):  
Public Health ◽  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Resistance Genes ◽  
One Health ◽  
Dairy Farm ◽  
Antibiotic Resistance Genes ◽  
Salmonella Spp ◽  
Antibiotic Resistant ◽  
E Coli

Aim: The present study was carried out to determine load of total bacteria, Escherichia coli and Salmonella spp. in dairy farm and its environmental components. In addition, the antibiogram profile of the isolated bacteria having public health impact was also determined along with identification of virulence and resistance genes by polymerase chain reaction (PCR) under a one-health approach. Materials and Methods: A total of 240 samples of six types (cow dung - 15, milk - 10, milkers' hand wash - 10, soil - 10 water - 5, and vegetables - 10) were collected from four dairy farms. For enumeration, the samples were cultured onto plate count agar, eosin methylene blue, and xylose-lysine deoxycholate agar and the isolation and identification of the E. coli and Salmonella spp. were performed based on morphology, cultural, staining, and biochemical properties followed by PCR. The pathogenic strains of E. coli stx1, stx2, and rfbO157 were also identified through PCR. The isolates were subjected to antimicrobial susceptibility test against 12 commonly used antibiotics by disk diffusion method. Detection of antibiotic resistance genes ereA, tetA, tetB, and SHV were performed by PCR. Results: The mean total bacterial count, E. coli and Salmonella spp. count in the samples ranged from 4.54±0.05 to 8.65±0.06, 3.62±0.07 to 7.04±0.48, and 2.52±0.08 to 5.87±0.05 log colony-forming unit/g or ml, respectively. Out of 240 samples, 180 (75%) isolates of E. coli and 136 (56.67%) isolates of Salmonella spp. were recovered through cultural and molecular tests. Among the 180 E. coli isolates, 47 (26.11%) were found positive for the presence of all the three virulent genes, of which stx1 was the most prevalent (13.33%). Only three isolates were identified as enterohemorrhagic E. coli. Antibiotic sensitivity test revealed that both E. coli and Salmonella spp. were found highly resistant to azithromycin, tetracycline, erythromycin, oxytetracycline, and ertapenem and susceptible to gentamycin, ciprofloxacin, and imipenem. Among the four antibiotic resistance genes, the most observable was tetA (80.51-84.74%) in E. coli and Salmonella spp. and SHV genes were the lowest one (22.06-25%). Conclusion: Dairy farm and their environmental components carry antibiotic-resistant pathogenic E. coli and Salmonella spp. that are potential threat for human health which requires a one-health approach to combat the threat.

scholarly journals The occurrence of antibiotic-resistant bacteria, including Escherichia coli, in municipal wastewater and river water

2019 ◽  
Vol 100 ◽  
pp. 00061 ◽  
Author(s):  
Adriana Osińska ◽  
Ewa Korzeniewska ◽  
Monika Harnisz ◽  
Sebastian Niestępski ◽  
Piotr Jachimowicz
Keyword(s):  
Escherichia Coli ◽  
Wastewater Treatment ◽  
River Water ◽  
Municipal Wastewater ◽  
High Efficiency ◽  
Treated Wastewater ◽  
Resistant Bacteria ◽  
Antibiotic Resistant Bacteria ◽  
Antibiotic Resistant ◽  
E Coli

Wastewater treatment plants (WWTPs) are major reservoirs of antibiotic-resistant bacteria (ARB) which are transported to the natural environment with discharged effluents. Samples of untreated wastewater (UWW) and treated wastewater (TWW) from four municipal WWTPs and samples of river water collected upstream (URW) and downstream (DRW) from the effluent discharge point were analyzed in the study. The total counts of bacteria resistant to β-lactams and tetracyclines and the counts of antibiotic-resistant Escherichia coli were determined. Antibiotic-resistant bacteria, including antibiotic-resistant E. coli, were removed with up to 99.9% efficiency in the evaluated WWTPs. Despite the above, ARB counts in TWW samples were high at up to 1.25x105 CFU/mL in winter and 1.25x103 CFU/mL in summer. Antibiotic-resistant bacteria were also abundant (up to 103 CFU/ml) in URW and DRW samples collected in winter and summer. In both UWW and TWW samples, the counts of ARB and antibiotic-resistant E. coli were at least one order of magnitude lower in summer than in winter. The study revealed that despite the high efficiency of bacterial removal in the wastewater treatment processes, considerable amounts of ARB are released into the environment with TWW and that the percentage of ARB in total bacterial counts increases after wastewater treatment.

scholarly journals Escherichia coli Antibiotic Resistance Patterns from Co-Grazing and Non-Co-Grazing Livestock and Wildlife Species from Two Farms in the Western Cape, South Africa

Antibiotics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 618
Author(s):  
Michaela Sannettha van den Honert ◽  
Pieter Andries Gouws ◽  
Louwrens Christiaan Hoffman
Keyword(s):  
Escherichia Coli ◽  
South Africa ◽  
Antibiotic Resistance ◽  
Resistant Bacteria ◽  
Antibiotic Resistant ◽  
E Coli ◽  
Wildlife Species ◽  
Resistance Patterns ◽  
Antibiotic Resistance Patterns ◽  
Grazing Livestock

Although limited, studies have found conflicting results on whether co-grazing results in significant antibiotic resistance transfer between species. This type of farming system can act as a vector in the geographical spread of antibiotic-resistant bacteria in the environment. The aim of this study was to determine the antibiotic-resistant patterns between co-grazing and non-co-grazing livestock and wildlife species in South Africa. Escherichia coli was isolated from the faeces of various wildlife and livestock species from two farms in South Africa and was tested for antibiotic resistance using the Kirby–Bauer disk diffusion method against chloramphenicol, nalidixic acid, ampicillin, streptomycin, sulphafurazole, and tetracycline. A selection of some common antibiotic-resistant genes (blaCMY, aadA1, sul1, sul2, tetA, and tetB) were detected using PCR. The E. coli isolates from wildlife and livestock that co-grazed showed no significant differences in antibiotic resistance patterns. However, this was not the case for tetracycline resistance as the livestock isolates were significantly more resistant than the co-grazing wildlife isolates. The E. coli isolates from the non-co-grazing livestock and wildlife had significant differences in their antibiotic susceptibility patterns; the wildlife E. coli isolates were significantly more resistant to sulphafurazole and streptomycin than the livestock isolates, whilst those isolated from the cattle were significantly more resistant to ampicillin than the wildlife and sheep isolates. The results of this study suggest that there could be an exchange of antibiotic-resistant bacteria and genes between livestock and wildlife that co-graze.

scholarly journals Prevalence of Escherichia coli and Antibiotic-Resistant Bacteria During Fresh Produce Production (Romaine Lettuce) Using Municipal Wastewater Effluents

2021 ◽  
Vol 12 ◽  
Author(s):  
Harvey N. Summerlin ◽  
Cícero C. Pola ◽  
Eric S. McLamore ◽  
Terry Gentry ◽  
Raghupathy Karthikeyan ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Water Reuse ◽  
Municipal Wastewater ◽  
Treatment Plant ◽  
Treated Wastewater ◽  
Resistant Bacteria ◽  
Romaine Lettuce ◽  
Potential Health ◽  
Antibiotic Resistant ◽  
E Coli

High demand for food and water encourages the exploration of new water reuse programs, including treated municipal wastewater usage. However, these sources could contain high contaminant levels posing risks to public health. The objective of this study was to grow and irrigate a leafy green (romaine lettuce) with treated wastewater from a municipal wastewater treatment plant to track Escherichia coli and antibiotic-resistant microorganisms through cultivation and post-harvest storage to assess their fate and prevalence. Contamination levels found in the foliage, leachate, and soil were directly (p < 0.05) related to E. coli concentrations in the irrigation water. Wastewater concentrations from 177 to 423 CFU ml−1 resulted in 15–25% retention in the foliage. Leachate and soil presented means of 231 and 116% retention, respectively. E. coli accumulation on the foliage was observed (p < 0.05) and increased by over 400% during 14-day storage (4°C). From randomly selected E. coli colonies, in all four biomass types, 81 and 34% showed resistance to ampicillin and cephalothin, respectively. Reclaimed wastewater usage for leafy greens cultivation could pose potential health risks, especially considering the bacteria found have a high probability of being antibiotic resistance. Successful reuse of wastewater in agriculture will depend on appropriate mitigation and management strategies to guarantee an inexpensive, efficient, and safe water supply.

scholarly journals Effect of Urban Wastewater Discharge on the Abundance of Antibiotic Resistance Genes and Antibiotic-Resistant Escherichia coli in Two Italian Rivers

2020 ◽  
Vol 17 (18) ◽  
pp. 6813 ◽  
Author(s):  
Fabrizio Pantanella ◽  
Itziar Lekunberri ◽  
Antonella Gagliardi ◽  
Giuseppe Venuto ◽  
Alexandre Sànchez-Melsió ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Resistance Genes ◽  
Antibiotic Resistance Genes ◽  
Treated Wastewater ◽  
Flow Volume ◽  
Antibiotic Resistant ◽  
E Coli ◽  
Absolute Concentrations ◽  
The Impact

Background: Wastewater treatment plants (WWTPs) are microbial factories aimed to reduce the amount of nutrients and pathogenic microorganisms in the treated wastewater before its discharge into the environment. We studied the impact of urban WWTP effluents on the abundance of antibiotic resistance genes (ARGs) and antibiotic-resistant Escherichia coli (AR-E. coli) in the last stretch of two rivers (Arrone and Tiber) in Central Italy that differ in size and flow volume. Methods: Water samples were collected in three seasons upstream and downstream of the WWTP, at the WWTP outlet, and at sea sites near the river mouth, and analyzed for the abundance of ARGs by qPCR and AR-E. coli using cultivation followed by disk diffusion assays. Results: For all studied genes (16S rRNA, intI1, sul1, ermB, blaTEM, tetW and qnrS), absolute concentrations were significantly higher in the Tiber than in the Arrone at all sampling sites, despite their collection date, but the prevalence of target ARGs within bacterial communities in both rivers was similar. The absolute concentrations of most ARGs were also generally higher in the WWTP effluent with median levels between log 4 and log 6 copies per ml but did not show differences along the studied stretches of rivers. Statistically significant site effect was found for E. coli phenotypic resistance to tetracycline and ciprofloxacin in the Arrone but not in the Tiber. Conclusions: In both rivers, diffuse or point pollution sources other than the studied WWTP effluents may account for the observed resistance pattern, although the Arrone appears as more sensitive to the wastewater impact considering its lower flow volume.

scholarly journals Isolation and Identification of Infection-Causing Bacteria in Dairy Animals and Determination of Their Antibiogram

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Safia Arbab ◽  
Hanif Ullah ◽  
Weiwei Wang ◽  
Ka Li ◽  
Ali Akbar ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Dairy Farm ◽  
Farm Animals ◽  
Resistant Bacteria ◽  
Salmonella Spp ◽  
Isolation And Identification ◽  
Antibiotic Resistant ◽  
E Coli ◽  
Shigella Spp ◽  
Dairy Animals

Pathogens are always a threat to the livestock and domestic animals due to their exposure to the contaminated environments. The study was conducted to evaluation of the prevalence of Escherichia coli, Shigella spp., Salmonella spp., and S. aureus, in farm animals (cattle and buffalos). A total of 150 (n = 150) samples were collected from cattle and buffaloes, 60 samples from cows’ and buffalo’s teats milk, 30 of water samples, and 60 of fecal samples isolates from dairy farm animals, which may act as reservoir disseminating such pathogens. Farm hygiene, management, and milking procedure were listed through a questionnaire. The most common pathogens detected in this study was E. coli 88 (58%) and S. aureus 81 (54%), followed by Salmonella spp. 32 (21%), and Shigella spp. 44 (29%), respectively. During the antibiogram studies, the results revealed that the highest number of bacterial isolates showed resistance against ampicillin 50 (56.8%), followed by ciprofloxacin 23 (26.1%) and augmentin 22 (25%) of Escherichia coli and ampicillin 49 (60.4%), cefpodoxime 23 (28.3%), and augmentin 20 (24.6%) of S. aureus. In the case of Salmonella spp., the highest resistance was showed by amoxicillin 16 (50%). In Shigella spp., the highest resistance was shown by ampicillin 16 (36.3%), followed by cefpodoxime and ceftazidime 10 (22.7%). The high frequency of isolates in this investigation with multiple antibiotic resistance ranges from 15. MARI % value of S. aureus and E. coli 15 (12.5%), followed by Salmonella and Shigella spp. ranges from 12 (10%), suggesting the presence of various antibiotic-resistant bacteria as well as highly resistant bacteria. The mean ± SD zone areas for the greater resistance are for E. coli and S. aureus, already known to be multiresistant, followed by Salmonella spp. and Shigella spp., when the zone areas are for the low resistance, and the findings determined that there was a little difference between S. aureus and E. coli.

scholarly journals Antibiotic resistance and prevalence of class 1 and 2 integrons in Escherichia coli isolated from hospital wastewater

2018 ◽  
Vol 37 (3) ◽  
pp. 209 ◽  
Author(s):  
Reza Ranjbar ◽  
Maryam Zeynali ◽  
Nooshin Sohrabi ◽  
Asghar Ali Kamboh
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Diffusion Method ◽  
Resistant Bacteria ◽  
Hospital Wastewater ◽  
Isolation And Identification ◽  
Antibiotic Resistant ◽  
E Coli ◽  
Class 1 ◽  
Hospital Wastewaters

BACKGROUND <br />Hospital wastewaters may contain antibiotic resistant bacteria such as Escherichia coli. These E. coli harbor integron genes that are responsible for antibiotic resistance. The purpose of the current study was to evaluate the frequency of class 1 and 2 integrons in environmental antibiotic resistant E. coli strains isolated from the hospital wastewaters in Tehran, Iran.<br /><br />METHODS<br />As a descriptive cross-sectional study, this research was performed from April to September 2015 on hospital wastewaters in Tehran. Bacterial isolation and identification was performed by standard biochemical and bacteriological procedures. Susceptibility testing was done by employing the disk diffusion method using different antibiotics. Total DNAs were extracted to evaluate the presence of class 1 and 2 integrons by using the polymerase chain reaction (PCR) method with specific primers. <br /><br />RESULTS<br />Fifty E. coli strains were isolated and identified from the wastewaters of 25 hospitals in Tehran. The phenotype results showed that 46 isolates (92%) were resistant to at least one antibiotic and 27 isolates (54%) were multidrug resistant. PCR showed that 35 (70%) and 20 (40%) of the isolates had class 1 and 2 integrons respectively and 14 isolates (28%) had both class 1 and class 2 integrons.<br /><br />CONCLUSION<br />This study has shown a considerable presence of class 1 and class 2 integrons in E. coli strains isolated from hospital wastewaters in Tehran. Proper antibiotics prescription and appropriate hospital wastewater treatment can prevent resistance genes in E. coli from circulating in the environment.

scholarly journals Predominance of blaTEM and tetA genes in antibiotic-resistant Escherichia coli isolates from Laguna Lake, Philippines

2021 ◽  
Author(s):  
Daile Meek Salvador-Membreve ◽  
Windell L. Rivera
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Antibiotic Resistance Genes ◽  
Multidrug Resistant ◽  
The Philippines ◽  
Resistant Bacteria ◽  
Antibiotic Resistant ◽  
E Coli ◽  
Laguna Lake ◽  
Antibiotic Genes

Abstract Lakes are one of the sinks of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs); however, information on ARB and ARGs in lakes in the Philippines is scarce. In this study, Escherichia coli was isolated from the largest freshwater lake in the Philippines, Laguna Lake, to detect antibiotic resistance and the presence of ARGs. Broth microdilution assay (BMA) and molecular identification of five environmentally prevalent ARGs (strA, blaCTX-M, blaSHV, blaTEM, and tetA) were performed. The majority (75.70%) of the isolates harbored at least one of the targeted antibiotic genes. Multiplex PCR detected about 49.07% of the isolates had genes for extended-spectrum β-lactamases (ESBL), which were mostly represented by blaTEM (47.66%). The genes strA and tetA were observed in this study with detection frequencies of 29.91 and 45.33%, respectively. About 95.69% of thermotolerant E. coli isolates were non-susceptible to six different antibiotics using BMA. Nearly 37% of the isolates were found to be multidrug-resistant (MDR) with most isolates resistant to ampicillin (81.72%). Furthermore, the occurrence of ESBL genes was significantly correlated with tetA genes (P = 0.013). To date, this study is the first to report on the presence of MDR and thermotolerant E. coli in Laguna Lake, Philippines.

scholarly journals Therapeutic effect of biosynthetic gold nanoparticles on multidrug-resistant Escherichia coli and Salmonella species isolated from ruminants

2021 ◽  
pp. 3200-3210
Author(s):  
Abeer M. Abdalhamed ◽  
Alaa A. Ghazy ◽  
Eman S. Ibrahim ◽  
Amany A. Arafa ◽  
Gamil S. G. Zeedan
Keyword(s):  
Escherichia Coli ◽  
Gold Nanoparticles ◽  
Antibiotic Resistance ◽  
Resistance Genes ◽  
Antibiotic Resistance Genes ◽  
Multidrug Resistant ◽  
Pathogenic Microorganisms ◽  
Salmonella Spp ◽  
Antibiotic Resistant ◽  
E Coli

Background and Aim: Multidrug-resistant (MDR) pathogenic microorganisms have become a global problem in ruminants as a result of the intensive use of antibiotics, causing the development of resistance among gut microbiota. The antibiotic-resistant microorganisms can be transferred from diseased animals to humans. This study aimed to determine the prevalence of MDR Escherichia coli and Salmonella spp. isolated from cattle, buffaloes, sheep, and goats suffering from respiratory signs, diarrhea, and mastitis and to screen the antibiotic sensitivity of selected isolated bacteria. It also detected antibiotic-resistance genes by polymerase chain reaction (PCR), produced green gold nanoparticles (AuNPs) using plant extracts (Artemisia herba-alba and Morus alba), and evaluated the antimicrobial activities of these biosynthesized nanoparticles on selected pathogens (E. coli and Salmonella spp.). Materials and Methods: MDR E. coli and Salmonella spp. were investigated using fecal samples (n=408), nasal swabs (n=358), and milk samples (n=227) of cattle, buffaloes, sheep, and goats with or without clinical signs, including respiratory manifestations, pneumonia, diarrhea, and mastitis, from different governorates in Egypt. E. coli and Salmonella spp. were isolated and identified on selective media, which were confirmed by biochemical reactions and PCR. Antimicrobial susceptibility testing against 10 commonly used antibiotics was performed using the Kirby-Bauer disk diffusion method. Antibiotic resistance genes blaTEM, blaSHV, blaOXA, and blaCTX-M were detected by PCR. The antibacterial effect of the biosynthesized AuNPs was evaluated by MIC and well diffusion assay. The biosynthesized AuNPs were also characterized by ultraviolet-visible spectrophotometry and transmission electron microscopy (TEM). Results: Among all fecal samples, the prevalence of E. coli was 18.4% (183/993) and that of Salmonella spp. was 16.7% (66/408), as determined by cultural and molecular tests. All isolates of E. coli and Salmonella spp. were 100% resistant to ampicillin (AM) and amoxicillin and highly resistant to cefoxitin and AM-sulbactam. The total rate of resistance genes in E. coli was 61.2% (112/183), while that in Salmonella was 63.6% (42/66) for pathogens isolated from ruminants with respiratory manifestations, pneumonia, diarrhea, and mastitis. Among the resistance genes, blaTEM had the highest prevalence rate in E. coli (25.9%, 21/81) while blaSHV had the lowest (9.8%, 8/81) in fecal swabs. AuNPs were successfully synthesized using aqueous leaf extract of A. herba-alba and M. alba as bioreducing agents. TEM analysis showed particle size of 10-42 nm for A. herba-alba and M. alba AuNPs. The biosynthesized AuNPs showed antibacterial activity against MDR E. coli and Salmonella spp. Conclusion: Rapid and accurate diagnostic methods are the cornerstone for effective treatment to reduce the risk of antimicrobial-resistant pathogenic microorganisms. This is particularly important for overcoming the increasing rate of MDR in ruminants with respiratory manifestations, pneumonia, diarrhea, and mastitis. This can be complemented by the development of AuNPs synthesized in an environmentally friendly manner AuNPs using natural plant extracts for the treatment of antibiotic-resistant microorganisms.

scholarly journals Fate and seasonal change of Escherichia coli resistant to different antibiotic classes at each stage of conventional activated sludge process

2020 ◽  
Vol 18 (6) ◽  
pp. 879-889 ◽  
Author(s):  
Ryo Honda ◽  
Chihiro Tachi ◽  
Mana Noguchi ◽  
Ryoko Yamamoto-Ikemoto ◽  
Toru Watanabe
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Activated Sludge ◽  
Diffusion Method ◽  
Resistant Bacteria ◽  
Secondary Treatment ◽  
Activated Sludge Process ◽  
Antibiotic Resistant ◽  
E Coli ◽  
Influent Wastewater

Abstract This study investigated the impact of each treatment stage of the activated sludge process on the fate of antibiotic resistant bacteria (ARB) in wastewater treatment plants (WWTPs). Wastewater and sludge samples were collected monthly at each stage of a commercial-scale WWTP. After 20–25 strains of indicator Escherichia coli were isolated from each sample on Chromocult Coliform Agar, antibiotic resistance of the isolates to amoxicillin (AMX), ciprofloxacin (CIP), norfloxacin (NFX), kanamycin (KM), sulfamethoxazole/trimethoprim (ST) and tetracycline (TC) were tested with the Kirby–Bauer disk diffusion method. As a result, activated sludge in the aeration tank and return sludge had higher abundance of antibiotic resistant E. coli than influent wastewater and secondary treatment effluent. AMX resistant E. coli was enriched in return sludge at the secondary clarifier. Higher temperature was also likely to cause an increase of AMX resistant E. coli in sludge. The antibiotic resistance profile of E. coli in secondary treatment effluent was more dependent on activated sludge than influent wastewater. These results suggested that activated sludge in WWTP possibly serves as a reservoir of ARB, and that behavior of ARB in WWTP differs by antibiotic classes.

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