ANTIBIOTIC RESISTANT IN AQUATIC MEDIA

Antibiotics are used in our daily life to treat illnesses and protect animals from them in general. Then, these are expulsed from human and animal metabolism and destined as a residual water. This is the main reason for the presence of antibiotics in the waste water, surface water and drinking water biofilms. Also, they’re found in soil, marine sediment, rivers and activated sludge.
Gene resistances are created in this kind of media, but the main problem is collective gene transmission where quorum sensing has a roll to take into account. In other words, if bacteria have the antibiotic resistance genes, we can not longer treat ourselves with the same medicines (ergo humans and animals are no longer immune).

WHAT ARE ANTIBIOTICS AND WHERE DO THEY COME FROM?
Antibiotics are composed by any substance that inhibits the growth of bacteria, making the proliferation impossible, or kills them in the process (1). Nowadays, antibiotics can be found everywhere and the main sources are anthropogenic (human fluids, medicines, antibiotics used in farms, etc). Some of them may not be reduced or eliminated by water treatment such as human fluids)

It’s true that bacteria can produce antibiotic by themselves, but the widespread use of antibiotics in Medicine and intensive animal husbandry (wastewater as a conveyance) has lead to a severe antibiotic contamination in aquatic media (2).

ANTIBIOTIC RESISTANCE GENES AND THEIR TRANSFERENCE
But, if antibiotic are used to eradicate bacteria, how have they developed different mechanisms to suppress the effects? The answer is vertical and horizontal gene transfer (3). 


The vertical gene transfer promote the transmission of antibiotic resistance genes (ARGs) to the next generation of bacteria while horizontal gene transfer exchange (HGT) genetic elements among bacteria of different taxonomic affiliation.

One of the main ways in HGT is conjugation, when plasmids (who have these ARGs) are transferred between bacteria or between bacterial cells and eukaryotic cells. Conjugation can transfer plasmids and the integrative conjugative elements in many different environments (soils, marine sediments, freshwater, wastewater and activated sludge). 

In drinking water sources, it has been found various antibiotic resistance genes like ampC, tet(A), mecA, β-lactamase genes (SHV-type, TEM-type, CTX-M-type, OXA-1, and CMY-2-type), and carbapenemase genes (KPC, IMP, VIM, NDM, GES, and OXA-48 genes) (3). 

Transduction has been shown to be common in marine environments. Although, viral metagenomic analyses (b-lactamase genes) have been detected in activated sludge and urban sewage. Also, the gene of methicillin resistance (Methicillin-resistant Staphylococcus aureus (MRSA)) has been found in bacteriophage DNA in wastewater treatment plant (4).

Also, some compounds promote horizontal transfer of ARGs like ZnO nanoparticles at sublethal concentrations (1 to 10 mg/l) as it’s demonstrated in the experiment done by X. Wang (2018) (5).


Figure 1. Graphical abstract of how nZnO facilitates horizontal gene transfer (5)
ZnO it’s an inorganic compound used as an additive in materials and products as plastics, ceramics, cement, paints, pigments, foods, batteries, cigarette filters… Therefore, this anthropogenic source has been promoting horizontal gene transfer of ARGs directly.

CONCENTRATIONS OF ANTIBIOTICS IN AQUATIC MEDIA
A study made in the water streams that receive wastewater effluents in South-Central Pennsylvania (2006) has shown concentrations of numerous antibiotics resumed in table (1):

Table 1. Summary of numbers of detections (of antibiotic and pharmaceuticals) by season analyzed at the U.S Geological Survey Organic Geochemistry Research Laboratory with their relative percent differences (6).

In this summary we can see the antibiotics that have concentration above of the minimum reporting level and that have to be controlled or eliminated somehow. It varies depending on the season and the place where the analysis had been made.

ELIMINATION OF ANTIBIOTICS
With the presence of antibiotic in water streams and the ARG’s being transferred between bacteria, the effectivity of antibiotics decrease in a alarmant velocity. That’s why there are some elimination processes of these substances:

Table 2. Summary of the elimination of antibiotics processes and their characteristics (7).

CONCLUSIONS
Since bacteria are part of the water ecosystem, they have developed resistance against antibiotics that humans transfer into wastewaters. With that said, we must reduce the presence of antibiotics (up to an acceptable threshold) in water environments if we do not wish for antibiotic resistance bacteria (9). 

As said before, there are mechanisms that can eliminate antibiotics from water, but these treatments difficult to perform in open waters. For this reason, it’s better to go for alternative techniques that are sustainable, like produce biodegradable antibiotics or find microorganisms that can degrade this compounds.

If it’s not possible to carry out alternative methods, we can increase the efficiency of the antibiotic elimination methods by building specific modules on EDAR to normalize the process and contribute to reduce antibiotics in water streams, seas, etc; which can affect underwater streams. 

REFERENCES

1. Microbiologistsociety.org. England: Microbiology Society,Inc.;c2018 [citada 2 de novembre de 2018]. Recuperat de: https://microbiologysociety.org/education-outreach/antibiotics-unearthed/antibiotics-and-antibiotic-resistance/what-are-antibiotics-and-how-do-they-work.html

2. T. Schwartz i W. Kohnen i B. Jansen i U. Obst. (2003). Detection of antibiotic-resistant bacteria and their resistance genes in wastewater, surface water, and drinking water biofilms. FEMS Microbiology Ecology, (43), 325-335. Recuperat de: https://academic.oup.com/femsec/article/43/3/325/480052
3. Fernando, D. M., Tun, H. M., Poole, J., Patidar, R., Li, R., Mi, R., Amarawansha, G., Fernando, W., Khafipour, E., Farenhorst, A., … Kumar, A. (2016). Detection of Antibiotic Resistance Genes in Source and Drinking Water Samples from a First Nations Community in Canada. Applied and environmental microbiology, 82(15), 4767-4775.. Recuperat de: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4984272/

4. B Berglund (2015) Environmental dissemination of antibiotic resistance genes and correlation to anthropogenic contamination with antibiotics, Infection Ecology & Epidemiology, 5:1. Recuperat de: https://www.tandfonline.com/doi/full/10.3402/iee.v5.28564

5. X. Wang i F. Yang i J. Zhao i Y. Xu i D. Mao i X. Zhu i Y. Luo i P.J.J Alvarez. (2018). Bacterial exposure to ZnO nanoparticles facilitates horizontal transfer of antibiotic resistance genes. NanoImpact, (10), 61-67. Recuperat de: https://www.sciencedirect.com/science/article/pii/S2452074817301325

6. Loper, C.A., Crawford, J.K., Otto, K.L., Manning, R.L., Meyer, M.T., and Furlong, E.T. (2007). Concentrations of selected pharmaceuticals and antibiotics in south-central Pennsylvania waters, March through September 2006: U.S. Geological Survey Data Series 300. Recuperat de: https://pubs.usgs.gov/ds/300/pdf/ds300.pdf

7. Klaus K, (2009) Antibiotic in the aquatic environment-a review-Part 1. Chemosphere (75) 426-428. Recuperat de: https://fenix.tecnico.ulisboa.pt/downloadFile/3779580650433/Kummerer_Antibiotics-environ-I_Chemosphere_2009.pdf

8. Rocha, Otidene & Brandão Pinheiro, Rannúzya & Duarte, Marta & Dantas, Renato & Pacheco Ferreira, Andrea & Benachour, Mohand & Silva, Valdinete. (2013). Degradation of the antibiotic chloramphenicol using photolysis and advanced oxidation process with UVC and solar radiation. Desalination and Water Treatment. 51. 7269-7275. 10.1080/19443994.2013.792148. Recuperat de: https://www.researchgate.net/publication/271673268_Degradation_of_the_antibiotic_chloramphenicol_using_photolysis_and_advanced_oxidation_process_with_UVC_and_solar_radiation

9. Klaus K, (2009) Antibiotic in the aquatic environment-a review-Part 2. Chemosphere (75) 435-441. Recuperat de: https://fenix.tecnico.ulisboa.pt/downloadFile/3779580650434/Kummerer_Antibiotics-environ-II_Chemosphere_2009.pdf


Comentarios

  1. Unknown15 de noviembre de 2018, 2:20

    Caldria canviar l’enfoc del treball per aprofundir-hi més. No cal que parleu del que és la reproducció asexual dels bacteris, ni que expliqueu els mecanismes de transferència horitzontal de gens. Tot això ja ho sabeu o bé ho heu treballat en altres assignatures. Cal dedicar l’espai del blog a aprofundir en el tema sense entrar en generalitats. Si algun lector no entén aquests conceptes ja els preguntarà en forma de comentari. En aquest sentit, no cal que expliqueu detalladament els mecanismes d’eliminació d’aquests antibiòtics (Elimination of Antibiotics). Si voleu, podeu posar aquesta informació en format de taula, però especificant l’efectivitat de cada procés, on s’aplica, costos, etc...). Tampoc cal explicar el que és el quòrum sensing, eviteu repetir el que ja hem vist a classe. El blog és per aprofundir en determinats continguts. Per exemple; no dieu quines concentracions d’antibiòtics es detecten en el medi natural i en quins ambients, no dieu quins són els gens de resistència implicats en aquesta problemàtica i en quins microorganismes es troben, no queda clar quin és el principal mecanisme responsable de la transferència horitzontal (conjugació, transformació o tranducció).... Altres qüestions més de detall: A la Introducció dieu que les resistències a antibiòtics es creen o generen. Això és cert, però el principal problema és la disseminació d’aquestes resistències, més que no pas que n’apareguin de noves. Per altra banda, no tots els antibiòtics causen la mort dels bacteris, alguns tenen efecte bacteriostàtic i per tant només eviten la seva proliferació, però no els maten. Malgrat tot, això fa que les defenses de l’organisme els puguin atacar abans no es reprodueixin. Us recomano que visiteu la pàgina web de l’ICRA (Institut Català de Recerca de l’Aigua), ubicat al Parc Científic de Girona. Hi ha un grup de recerca en “Qualitat de l’Aigua i Diversitat Microbiològica” i la seva línia principal de treball és l’estudi de les resistències a antibiòtics en el medi aquàtic. Us pot ajudar a trobar informació d’interès.

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  2. Unknown16 de diciembre de 2018, 11:12

    (Evaluable) He has explained some methods to eliminate antibiotics from water, what method do you think or have you found that is better? (Either for the effectiveness, for being more economical ...). Thanks!

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    Respuestas
    1. Gerard Casacuberta23 de diciembre de 2018, 10:52

      The best way to eliminate antibiotics is under laboratory conditions, because we control all the factors. But if we had antibiotic in aquatic media, we think that hidrolosy and termolisy is better, because it’s only affected by temperature and pH. Although, the equipment is expensive, but the cost of manteniment is low.

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  3. Unknown16 de diciembre de 2018, 11:40

    (Evaluable) If the presence of antibiotics is due to the use of medications, have you considered that the problem is the high concentration of antibiotics in these medicines? And if the problem is the concentration of antibiotics in a medicine is higher than we need or can assimilate, a solution would not be to decrease the concentration until we reach the one that we fully assimilate?

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    Respuestas
    1. Nerea Martínez Porras23 de diciembre de 2018, 10:53

      The problem is not the high concentration of antibiotic in medicines, antibiotic are medicines by themselves. Doctors prescribe a moderate amount of antibiotic in order to make good use of them (low doses of antibiotics in humans would not cure illness either). The main problem is the abuse of them when humans/animals do not really need them.

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  4. Lukas_barrero16 de diciembre de 2018, 13:15

    (Evaluable) Once we eliminate antibiotics in our bodies, these will pass to the wastewater and subsequently concentrated in the WWTP. How do these concentrations of antibiotics affect the communities of microorganisms that live in the biological reactors of WWTPs?

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    Respuestas
    1. Nerea Martínez Porras23 de diciembre de 2018, 10:59

      It depends on the concentration of these antibiotics in the wastewater. Also, we have to remember the existence of bacteriophages. If the microbiota in the biological reactor is damaged, there’s a possibility to create the resistance to those antibiotics by the horizontal gene transfer. Bacteriophages not only infect and transfer ARG’s (antibiotic resistance genes), they establish a reservoir of those genes.

      For more information you can see these websites: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5702337/ and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5783987

      -Gerard Casacuberta i Nerea Martínez

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