# Occurrence and Seasonal Variation of Antibiotics in Fez-Morocco Surface Water

Oualid Chaib, Btissam Arhoune, Sanae Achour, Elodie Moreau-Guigon, Fabrice Alliot, Marc Chevreuil, Samira El Fakir, Ilham El Arabi, Bouchra Oumokhtar

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## To cite this version:

Oualid Chaib, Btissam Arhoune, Sanae Achour, Elodie Moreau-Guigon, Fabrice Alliot, et al. Occurrence and Seasonal Variation of Antibiotics in Fez-Morocco Surface Water. American Journal of Environmental Sciences, 2019, The Handbook of Environmental Chemistry, 15 (4), pp.127-136. 10.3844/ajessp.2019.127.136. [hal-03809750](https://hal.sorbonne-universite.fr/hal-03809750)

HAL Id: hal-03809750

https://hal.sorbonne-universite.fr/hal-03809750

Submitted on 30 May 2023

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Distributed under a Creative Commons Attribution 4.0 International License
Original Research Paper

# Occurrence and Seasonal Variation of Antibiotics in Fez-Morocco Surface Water

¹,⁵Oualid Chaib, <fnref n="1" />,⁶Btissam Arhoune, ²Sanae Achour, ³Elodie Moreau-Guigon, ³Fabrice Alliot, ³Marc Chevreuil, ⁴Samira El Fakir, ⁵Ilham El Arabi and ¹Bouchra Oumokhtar

### Article history

Received: 25-03-2019

Revised: 22-07-2019

Accepted: 26-08-2019

### Corresponding Author:

Bouchra Oumokhtar

Laboratory of Microbiology
and Molecular Biology, Faculty
of Medicine and Pharmacy,
University Sidi Mohammed
Ben Abdallah USMBA, Fez,
Morocco

Tel: +212 668 979 890/

+212 642 333 164

Fax:+212 535 619 321

E-mail: bouchra.oumokhtar@usmba.ac.ma

**Abstract:** The presence and accumulation of antibiotics in the water environment has become emerging contaminants of concern causing disruption of ecosystems worldwide. We describe here the seasonal variation and the occurrence of antibiotic residues in Fez city surface water (Morocco). During one year between February 2014 and January 2015, 8 surface water samples were collected monthly. Quantification of the 7 antibiotics was performed by on-line Solid Phase Extraction (SPE) liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of 96 surface water samples were investigated and the results revealed that 100% of the sites were contaminated by at least one antibiotic. Amoxicillin had the highest concentration with maximum concentration (4107 ng L⁻<fnref n="1" />), followed by ciprofloxacin (1058 ng L⁻<fnref n="1" />) and sulfamethoxazole was the most widely detected (93%). Seasonal variation showed that the concentration of antibiotics was higher in winter for trimethoprim (96 ng L⁻<fnref n="1" />), ciprofloxacin (438 ng L⁻<fnref n="1" />) and in summer for amoxicillin (1113 ng L⁻<fnref n="1" />), sulfamethoxazole (162 ng L⁻<fnref n="1" />) and erythromycin (47 ng L⁻<fnref n="1" />). The results from this research show that antibiotics are frequent contaminants in Fez city surface water. This is the first attempt to assess the occurrence of these 7 pharmaceutical residues in water samples in Fez Morocco.

**Keywords:** Contamination, Antibiotics, Surface Water, LC/MS/MS, Seasonal Variation, Fez

## Introduction

Water, the essential substance to humans and the source of life, can become a serious hazard to our health, as well as to the life of the flora and fauna. Water bodies are generally sources of drinking water for many people and are used in agriculture for irrigation processes. Water quality can be affected by the increasing discharge of organic contaminant coming from different applications.

The presence of antibiotic in water bodies have been drawing extensive attention because of their high

water solubility, resistance to degradation and potential risks to ecosystem and human health (Tang *et al.*, 2015). These emerging contaminants may originate from different sources and many studies have shown that antibiotics were introduced to the environment from Wastewater Treatment Plants (WWTPs) (Leung *et al.*, 2012; Proia *et al.*, 2016; Zhang *et al.*, 2017), hospitals (Szekeres *et al.*, 2017), or land application of animal manure (Karcı and Balcıoğlu, 2009). Aquaculture (Cabello, 2006), and industrial garbage (Collado *et al.*, 2014; Shishir *et al.*, 2011).

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<footnote n="1">¹Laboratory of Microbiology and Molecular Biology,
Faculty of Medicine and Pharmacy, University Sidi Mohammed Ben Abdallah USMBA, Fez, Morocco</footnote>

<footnote n="2">²Laboratory Central of Medical Analysis, CHU Hassan II,
Faculty of Medicine and Pharmacy, University Sidi Mohammed Ben Abdallah USMBA, Fez, Morocco</footnote>

<footnote n="3">³EPHE, PSL, Sorbonne Université, CNRS, Milieux Environnementaux,
Transferts et Interactions dans les Hydrosystèmes et les Sols, METIS, 75005 Paris France</footnote>

<footnote n="4">⁴Laboratory of Epidemiology and Clinical Research,
Faculty of Medicine and Pharmacy, University Sidi Mohammed Ben Abdallah USMBA, Fez, Morocco</footnote>

<footnote n="5">⁵Laboratory of Physiology, Pharmacology and Environmental Health, Faculty of Sciences Dhar El Mehraz,
University Sidi Mohammed Ben Abdallah USMBA, Fez, Morocco</footnote>

<footnote n="6">⁶Laboratory of Biotechnolgy, Faculty of Sciences Dhar El Mehraz, University Sidi Mohammed Ben Abdallah USMBA, Fez, Morocco</footnote>
Several studies from different countries reported contamination by antibiotics in tap water (Cai *et al.*, 2015), surface water (Batt and Aga, 2005), groundwater (Ruixue *et al.*, 2015), sediments (Kim and Carlson, 2007), wastewater treatment plant effluents (Khan *et al.*, 2013). In Morocco, the antibiotics consumption has increased from 9.68 in 2003 to 13.85 Defined Daily Dose/1000 Inhabitant/Day (DDD) in 2012 (Inouss *et al.*, 2015). The public has easy accessibility to antibiotics in low and middle-income countries, from a variety of sources, including drugstores, over-the-counter chemical shops, hospitals, and roadside stalls (Lerbech *et al.*, 2014). Antibiotics can sometimes be bought at pharmacies and drugstores without prescription, despite prohibiting legislation's to stop selling (Bekoe *et al.*, 2014; Lerbech *et al.*, 2014). Extensive accessibility to antibiotics in developing countries could lead to continuous exposure to antibiotics via food and water (Belaïche, 2014). Therefore, the existing treatment facilities of wastewater treatment plants, which are designed for removing biodegradable organics and nutrients, cannot effectively eliminate these recalcitrant chemicals, leading to considerable discharge of pharmaceuticals into aquatic environments (Jin-Lin and Wong, 2013; Tamtam *et al.*, 2008). The use of wastewater for irrigation is common in low and middle-income countries (Drechsel and Keraita, 2014). Usually, untreated and/or partially treated wastewater from urban areas is discharged into drains, smaller streams and other tributaries of larger water bodies, where it is mixed with

storm and freshwater (diluted wastewater) before it is used by farmers. This surface water is referred to as low quality water (Raschid-Sally and Jayakody, 2008).

Thus, the monitoring program of the present study is being implemented for determining the occurrence and seasonal variation of seven antibiotics in Fez city surface water (Morocco).

## Material and Methods

### Target Chemicals

In this study, 7 molecules of antibiotics belonging to several families were selected as target chemicals regarding their rates of consumption in either human or veterinary practices in Fez city (Belaïche, 2014), their detections and persistence in the water environment. Nevertheless, these molecules have been chosen in accord to the availability of analytical standards in the market. Detailed information of the target chemicals is summarized in Table 1.

### Description of Study Area

Oued Fez is the main water body crossing the city of Fez in Morocco (Derwich *et al.*, 2008). It is a tributary of the Sebou River, the biggest river system in Morocco with its 40,000 km² catchment (Fig. 1). The river flows in an easterly direction from the springs of “Ras el Ma” (elevation = 420 m a.s.l.) through the Fez medina and into the Sebou, 4 km downstream from the city of Fez (elevation = 210 m a.s.l.).

<figure><img src="image_4.png" /><figcaption>Fig. 1: Sample sites locations on Fez water course</figcaption></figure>
<table><caption>**Table 1:** Uses of selected antibiotic targets</caption><thead><tr><td>Family</td><td>Compound</td><td>Uses</td></tr></thead><tbody><tr><td>β-lactams</td><td>Amoxicillin</td><td>Veterinary, Human</td></tr><tr><td>Tetracycline</td><td>Tetracycline</td><td>Veterinary, Human and Pisciculture</td></tr><tr><td>Macrolide</td><td>Erythromycin</td><td>Human</td></tr><tr><td>Sulfamide</td><td>Sulfamethoxazole</td><td>Veterinary, Human</td></tr><tr><td>Fluoroquinolone</td><td>Ciprofloxacin</td><td>Human</td></tr><tr><td>Quinolone</td><td>Oxolinic Acid</td><td>Veterinary</td></tr><tr><td>Diaminopirymidimes</td><td>Trimethoprim</td><td>Veterinary, Human and Pisciculture</td></tr></tbody></table>

<table><caption>**Table 2:** Geophysical coordinates, land use and location of the sampling points</caption><thead><tr><td>Sampling points</td><td>Geophysical Coordinates</td><td>Land use</td><td>Sections of the main stream</td></tr></thead><tbody><tr><td>S1</td><td>34°2′25.03″-5°3′40.21″</td><td>Rural with farming activities</td><td>Upstream</td></tr><tr><td>S2</td><td>34°3′19.14″-5°0′14.62″</td><td>Urban</td><td></td></tr><tr><td>S3</td><td>34°2′31.35″-4°59′38.63″</td><td>Urban</td><td>Midstream</td></tr><tr><td>S4</td><td>34°3′19.66″-4°58′29.85″</td><td>Urban with farming activities</td><td></td></tr><tr><td>S5</td><td>34°3′13.49″-4°58′59.95″</td><td>Urban</td><td></td></tr><tr><td>S6</td><td>34°4′28.71″-4°57′36.14″</td><td>Urban</td><td></td></tr><tr><td>S7</td><td>34°4′29.77″-4°56′20.36″</td><td>Rural with farming activities</td><td></td></tr><tr><td>S8</td><td>34°4′48.61″-4°54′58.31″</td><td>Rural with farming activities</td><td>Downstream</td></tr></tbody></table>

Its main course is 33 km long and its catchment area is 615 km² (Lombard-Latune *et al.*, 2010). The climate is characterized by hot and dry summers and cold winters. Diurnal temperature swings are large; the mean range is 17-34°C in July and 4-15°C in January. The temperature can, however, rise above 40°C in the summer, especially when the desert wind, is blowing from the Sahara, and fall below 0°C in winter. The rainfall maximum is in the winter period whereas the summer period is almost completely dry and daily hours of bright sunshine varies between about 6h in December and 11 H in July (Perrin *et al.*, 2014). All of Fez's sewage estimated 38 million m³ (or 110.000 m³/j) by Autonomous distribution control of water and electricity Fez) is flushed directly into nearby watercourses. This includes industrial effluents generated by many industries including tanneries, oil mills, metal works, potteries, resulting in serious degradation of water quality. Tanneries, where the different processes are still carried out traditionally, are probably the most polluting and flush, day after day, considerable amounts of chemicals including chromium and ammonium in addition to organic matter into the river (Nazer *et al.*, 2006; Prabhavathy, 2010).

## Sampling Schedule

During one year between February 2014 and January 2015, we collected 96 surface water samples from various urban environments (S1-S8) to cover major land use types in Fez city (Fig. 1), which includes rural areas with farming activities (n = 36), urban (n = 48) and urban area with farming activities (n = 12) (Table 2).

Water samples were collected from the surface of water bodies with 1L glass bottles, which has been conditioned before sampling to avoid contamination by organic compounds. Sample bottles were stored in a cooler with ice until transportation to the laboratory. The

samples were filtered using 0.7 µm Whatman glass fiber filters immediately after collection. Filtrates were stored at -18°C until analyses.

## Experimental

### Reagents and Chemicals

The following antibiotics were purchased from A2S via CIL-Cluzeau (Sainte-Foy-la-Grande, France): amoxicillin (AMO), erythromycin (ERY), sulfamethoxazole (SMX), tetracycline (TET), ciprofloxacin (CIP), oxolinic acid (OXO). Trimethoprim (TRI) was meanwhile purchased from LGC Standards (Molsheim, France).

¹³C- or deuterium-labelled compounds were used as internal standards (ISs): ethyl-d5-oxolinic acid (OXO-d5) was purchased from Sigma-Aldrich and Amoxicillin 3 H₂O; phenyl-13C6,99% (¹³C-AMO), erythromycin, N,N dimethyl-13C2 (¹³C-ERY), sulfamethoxazole, ring-13C6 (¹³C-SMX), ciprofloxacin; HCL-2,3 carboxyl-13C3; quinoline-15N (¹³C-CIP) were purchased from LGC Standards. All ISs had purity higher than 95% (isotopic purity >99%).

LC-grade methanol (MeOH) and acetonitrile (ACN) were purchased from VWR (Fontenay Sous Bois, France). Ultrapure water (UP-water) was dispensed from an Elga Purelab Maxima water purification system (Elga LabWater, Le Plessis Robinson, France). Analytical grade formic acid (99%), ortho-phosphoric acid (85%), EDTA disodium salt (Na₂-EDTA) (99%) and NaOH 50% were purchased from Sigma-Aldrich.

For most analytes, commercial stock standard solution of each compound were sold in MeOH or in acetonitrile except for OXO-d5 and ¹³C-AMO who was sold in powder. OXO-d5 was prepared in MeOH with 0.1% NaOH 50% to increase her solubility. For the same reason, ¹³C-AMO was
prepared in UP-water. These stock solutions were stored in amber glass vials at -18°C.

Working mix solutions of ISs and native compounds were prepared in MeOH (0.1 ng µL⁻¹).

## Sample Collection and Preparation

Fifty milliliter of water samples were filtered through 25 mm glass fiber GF/F filters, nominal cut-off size 0.7 µm (Whatman, Fontenay Sous Bois, France). pH was adjusted at 7 with 5% ortho-phosphoric acid or 5% NaOH. Then 2 mL of the so-obtained filtrate was passed through 0.2 µm nylon membrane filters (Millipore, France) and 0.1% Na2-EDTA 1 M and ISs (at 0.1 ng µL⁻¹) was added just before analyze. EDTA was used as a chelating agent to reduce antibiotic binding to major cations, thereby promoting analyte retention on the SPE cartridge.

## On-line SPE-LC-MS/MS Analysis of Antibiotics

We used the method On-line SPE-LC-MS/MS as described previously with a few modifications (Dinh et al., 2011). Separation in the LC column was achieved using an Agilent Zorbax Eclipse XDB-C 18 column (4.6 mm I.D. × 50 mm, 1.8 m particle size) with a 0.2 µm prefilter upstream to protect the analytical column, the total run time in separation was 15 min and the IS used for quantification were 13C-AMO was used for AMO, 13C-SMX was used for SMX, TRI and TET, 13C-ERY was used for ERY and 13C-CIP was used for CIP and OXO-d5 for OXO.

All steps of the LC-MS/MS analytical methods, the validation of the method and the limits of quantification (LOQs) are detailed in the Supplementary Information.

# Results

## Spatial Distribution of Antibiotic Residues in Surface Water

Results of our study revealed that 100% of the study sites were contaminated by at least one antibiotic (positive detection). The highest positive samples percentage was recorded in downstream respectively with 63% and 59% respectively in S7 and S8, followed by midstream 48% in S3, 46% in S4, 31% in S5 and 57% in S6. Finally, the contamination rate in upstream was lower with 28% and 32% respectively in S1 and S2.

Concerning antibiotic detection, sulfamethoxazole was the most frequent antibiotics detected in all sites (93%) followed by ciprofloxacin (75%). Trimethoprim came in third range with (69%), amoxicillin and erythromycin were detected at (60%). However, the least detected antibiotics were tetracycline and oxolinic acid with 3% (Fig. 2).

Table 3 summarized the variation of antibiotic concentration of the 8 sample sites analyzed during one year from February 2014 to January 2015. The results showed that the maximum concentration was recorded to amoxicillin with a maximum of 4107 ng L⁻¹ recorded in site S8 on July and to ciprofloxacin with a maximum of 1058 ng L⁻¹ recorded in site S7 on December. Besides, SMX comes in second range with a respectively 553 ng L⁻¹ recorded in site S8 on August, followed by ERY with a maximum of 114 ng L⁻¹ recorded in site S6 on December for and TRI with 264 ng L⁻¹ recorded in site S8 on July and L⁻¹.

<figure><img src="image_5.png" /><figcaption>Fig. 2: Detection percentages of antibiotics in 96 surface water samples</figcaption></figure>
<table><caption>**Table 3:** Minimum/maximum, median and extended antibiotic concentrations in ng L⁻¹ of the 96 samples analyzed</caption><thead><tr><th>Site</th><th></th><th>AMO</th><th>CIP</th><th>SXM</th><th>TET</th><th>TRI</th><th>ERY</th><th>OXO</th></tr></thead><tbody><tr><td rowspan="3">S1</td><td>Ranges</td><td>&lt;158.3</td><td>&lt;7.2-20</td><td>2-12</td><td>&lt;111.4</td><td>&lt;1.9-5</td><td>&lt;7.8</td><td>&lt;12.2</td></tr><tr><td>Mean</td><td>&lt;158.3</td><td>7</td><td>4</td><td>0</td><td>1</td><td>25</td><td>0</td></tr><tr><td>Median</td><td>&lt;158/3</td><td>8</td><td>4</td><td>&lt;111.4</td><td>&lt;1.9</td><td>&lt;7.8</td><td>&lt;12.2</td></tr><tr><td rowspan="3">S2</td><td>Ranges</td><td>&lt;158.3-205</td><td>&lt;7.2-20</td><td>4-47</td><td>&lt;111.4</td><td>&lt;1.9-5</td><td>&lt;7.8-65</td><td>&lt;12.2</td></tr><tr><td>Mean</td><td>23</td><td>62</td><td>12</td><td>0</td><td>1,1</td><td>46</td><td>0</td></tr><tr><td>Median</td><td>&lt;158.3</td><td>8</td><td>6</td><td>&lt;111.4</td><td>&lt;1.9</td><td>53</td><td>&lt;12.2</td></tr><tr><td rowspan="3">S3</td><td>Ranges</td><td>&lt;158.3-2323</td><td>&lt;7.2-357</td><td>&lt;1.9-327</td><td>&lt;111.4</td><td>&lt;1.9-44</td><td>&lt;7.8-65</td><td>&lt;12.2-55</td></tr><tr><td>Mean</td><td>914</td><td>133</td><td>49</td><td>0</td><td>13,4</td><td>38</td><td>6</td></tr><tr><td>Median</td><td>554</td><td>70</td><td>17</td><td>&lt;111.4</td><td>1</td><td>55</td><td>&lt;12.2</td></tr><tr><td rowspan="3">S4</td><td>Ranges</td><td>&lt;158.3-1350</td><td>&lt;7.2-277</td><td>&lt;1.9-52</td><td>&lt;111.4-286</td><td>&lt;1.9-22</td><td>&lt;7.8-70</td><td>&lt;12.2-64</td></tr><tr><td>Mean</td><td>362</td><td>34</td><td>15</td><td>24</td><td>6</td><td>25</td><td>10</td></tr><tr><td>Median</td><td>211</td><td>9</td><td>9</td><td>&lt;111.4</td><td>7</td><td>&lt;7.8</td><td>&lt;12.2</td></tr><tr><td rowspan="3">S5</td><td>Ranges</td><td>&lt;158.3-286</td><td>&lt;7.2-30</td><td>4-35</td><td>&lt;111.4</td><td>&lt;1.9-7</td><td>&lt;7.8-64</td><td>&lt;12.2</td></tr><tr><td>Mean</td><td>37</td><td>6</td><td>10</td><td>0</td><td>2</td><td>24</td><td>0</td></tr><tr><td>Median</td><td>&lt;158.3</td><td>6</td><td>8</td><td>&lt;111.4</td><td>&lt;1.9</td><td>&lt;7.8</td><td>&lt;12.2</td></tr><tr><td rowspan="3">S6</td><td>Ranges</td><td>325-4005</td><td>11-1023</td><td>12-385</td><td>&lt;111.4-134</td><td>10-264</td><td>&lt;7.8-114</td><td>&lt;12.2</td></tr><tr><td>Mean</td><td>1165</td><td>207</td><td>80</td><td>11</td><td>50</td><td>31</td><td>0</td></tr><tr><td>Median</td><td>708</td><td>58</td><td>43</td><td>&lt;111.4</td><td>19</td><td>6</td><td>&lt;12.2</td></tr><tr><td rowspan="3">S7</td><td>Ranges</td><td>389-3204</td><td>26-1058</td><td>23-410</td><td>&lt;111.4-142</td><td>12-242</td><td>&lt;7.8-84</td><td>&lt;12.2</td></tr><tr><td>Mean</td><td>1715</td><td>381</td><td>182</td><td>12</td><td>95</td><td>45</td><td>0</td></tr><tr><td>Median</td><td>1687</td><td>109</td><td>126</td><td>&lt;111.4</td><td>70</td><td>38</td><td>&lt;12.2</td></tr><tr><td rowspan="3">S8</td><td>Ranges</td><td>&lt;158.3-4107</td><td>&lt;7.2-951</td><td>15-553</td><td>&lt;111.4</td><td>3-120</td><td>&lt;7.8-81</td><td>&lt;12.2</td></tr><tr><td>Mean</td><td>2247</td><td>188</td><td>178</td><td>0</td><td>56</td><td>30</td><td>0</td></tr><tr><td>Median</td><td>2247</td><td>109</td><td>154</td><td>&lt;111.4</td><td>47</td><td>16</td><td>&lt;12.2</td></tr></tbody></table>

<figure><img src="image_6.png" /><figcaption>**Fig. 3:** Annual variations of antibiotic concentrations in midstream</figcaption></figure>

However, the lowest value was recorded to tetracycline with a maximum of 286 ng L⁻¹ recorded in site S4 on December, followed by oxolinic acid 64 ng L⁻¹ recorded in site S4 on November (Table 3).

## Seasonal Variation of Antibiotic Concentrations

Seasonal variation of antibiotic concentration has shown that during periods with high flow, the concentration was 6 times lower than during low flow

periods (Fig. 3). Depending on the season, the river flow ranged from 0.058 to 0.827 m³ s⁻¹ which corresponded to a theoretical dilution factor from 6 to 15.

Annual variations of the antibiotic flux in Fez city midstream ranged between 0.004 to 5.28 g d⁻¹, with the presence of two substantial peaks recorded during the winter period (February 2014 and January 2015) respectively, corresponding to high-flow events (Fig. 4).
<figure><img src="image_7.png" /><figcaption>Fig. 4: Antibiotic flux in midstream</figcaption></figure>

Discussion

Because compound detection and concentration are
dependent on source strength, hydrologic condition, timing
of sampling and other factors (Focazio et al., 2008)
interpretations of these reconnaissance data are limited.
Surface water samples recorded higher contamination levels
by most of the pharmaceuticals than reported worldwide
(Locatelli et al., 2011; Kasprzyk-Hordern et al., 2007;
Boix et al., 2015). Once entering into water, these
antibiotics may have direct toxicity to aquatic organisms,
even at low concentrations (ng L⁻¹ or µg L⁻¹ level) (Chen
and Zhou, 2015). For example, they could cause
phytoplankton toxicity, inhibition of microbial activity
and change the microbial community structure (Liao et al.,
2017). Additionally, antibiotics could promote the
development of bacterial resistant (Chaib et al., 2017),
which might be potentially harmful to the ecosystem and
human health (Zhang et al., 2011).

The level of antibiotics in upstream (sites S1 and S2)
were approximately two folds lower than midstream
(from sites S3 to S6). This large difference may be
directly related to the contamination sources in
midstream (urban area), where was little disturbance by
human activities and the presence of several private
hospitals, clinics, and medical analysis laboratories. In
addition, the antibiotic detection percentage was much
higher in site S6 (57%) than the other urban sites. In fact,
site S6 is a well-known as a hots-pot and has a denser
population (around 612489 of inhabitants), this finding
highlight the contribution of excessive antibiotics
consumption in water environment contamination.
Besides, the level of antibiotics in downstream were

much higher than up and midstream. Sites S7 and S8
(rural with farming activities) are impacted by the
agricultural activities and the continuously WWTP's
discharges into surface water.

We showed that AMO was the most concentrated and
SMX was the most frequent in surface water samples. β-
lactam antibiotics are among the most frequently used
and consumed in large quantities in Morocco and
worldwide (Belaïche, 2014), their detection is difficult
and the studies which investigated the presence of β-
lactam and antibiotics are scarce. because of the poor
stability of the β-lactam ring under pH conditions
(Moreno-Bond et al., 2009). Some studies were not
successful in detecting β-lactam and cephalosporin
antibiotics in water matrices (Gros et al., 2013; Zhou and
Chen, 2013). Also, SMX is among the most widely used
prescribed antibiotics, the large scale of livestock and
poultry farming and the high population density result in
high usage of SMX (Binh et al., 2018). Levels of CIP
found was higher, this result was not surprising because
CIP is typically used in human and veterinary medicine
to treat and prevent diarrhoea and other intestinal
infections (Chen et al., 2012; Liang et al., 2013).
Additionally, ERY is widely used in concentrated animal
feeding operations to treat bacterial infection diseases of
animal and human, such as respiratory diseases,
intestinal infections (Lien et al., 2016). More even, TET
constitute one of the most extensively used antibiotic
classes due to their low cost, ease of use and relatively
minor side effects (Li et al., 2016; Ahmed et al., 2017).
Tetracycline are also the most widely used veterinary
drugs and feed additives in aquaculture and livestock
industries. TET is also added at the sub-therapeutic level to animal feed to prevent infection and act as growth promoters (Sarmah et al., 2006). Besides, OXO is widely used in aquaculture to cure and prevent skin infections in fish. The pisciculture production is usually made in the winter because of the low temperature; the non-negligible fish farming activity present around the city could be involved in the release of the measured OXO (Tamtam et al., 2008).

The seasonal variation of antibiotic concentration has shown that during periods with high flow, the antibiotics concentration was 6 times lower than during low flow periods. This difference in sampling periods can be explained by the variation in antibiotics consumption, physicochemical behavior such as photo-degradation and river flow conditions between summer and winter.

The period of high flows in Oued Fez from December to February (with an average precipitation of 32.6 mm) could led to dilution on the antibiotics concentration in surface water. Studies have reported that the Seasonal variation in antibiotics concentration is related to production, consumption, excretion or environmental factors such as solar irradiation, precipitation, and temperature (Conley et al., 2008). Our results have been confirmed by other studies reporting higher concentrations in summer (Jiang et al., 2011; Gracia-Lor et al., 2012). This variation can partially be explained by the fact that more antibiotics are used and discharged into the aqueous environment during summer because they are utilized to treat higher rates of gastrointestinal infection and diarrhea among both humans and domestic animals (Gracia-Lor et al., 2012). In contrast, levels of antibiotics in waterways increase during the dry season because there is much lower flow runoff in rivers, although the consumption of antibiotics is reduced to some extent due to fewer outbreaks of gastrointestinal infection (Jiang et al.,

2011). However, the differences observed in Antibiotic flux in midstream might be related to sediment resuspension by the flood under high river flow events. Moreover, antibiotic persistence in sediment (Hektoen et al., 1995) and their possible desorption towards the aqueous phase have been reported (Smith and Samuelsen, 1996; Simon, 2005).

The worldwide comparison of the 7 pharmaceuticals in the river surface water is presented in Table 4. The highest concentration of each of the pharmaceuticals obtained in the streams surface water was at moderate to high levels of contamination compared to the concentrations in other regions of the world. In the case of β-lactams for example, AMO (4107 ng L⁻¹) was detected at much higher levels than that of Brazil (8.9 ng L⁻¹, Locatelli et al., 2011), United Kingdom (245 ng L⁻¹, Kasprzyk-Hordern et al., 2007). For the macrolide, ERY (114 ng L⁻¹) was detected at a higher concentration than that of Spain (5 ng L⁻¹, Boix et al., 2015), Serbia (9.1 ng L⁻¹, Petrović et al., 2014) but was much lower than that of the China (810 ng L⁻¹, Gulkowska et al., 2006). In addition, OXO (64 ng L⁻¹) was detected at low level than that of France (140 ng L⁻¹, Tamtam et al., 2008) and higher than that of Denmark (5 ng L⁻¹, Sørensen et al., 2004).

## Conclusion

The results of this study confirm that several antibiotics residues originating from domestic, hospital waste and farming contaminate Fez surface water. This finding is very interesting and may constitute the basis for future work on other Moroccan cities surface water and other environmental matrices. There is a need to continuously predict the concentrations of these antibiotic compounds and to design strategies to minimize exposure to these compounds.

<table><caption>**Table 4:** Global comparison of antibiotic concentrations in surface water</caption><thead><tr><th></th><th>Antibiotics</th><th>Our results</th><th>Other results</th><th>Reference</th></tr></thead><tbody><tr><td rowspan="11">Surface water</td><td>Amoxicillin</td><td>159 to 4107ng L<sup>-1</sup></td><td>8.9 ng L<sup>-1</sup><br>39 to 245ng L<sup>-1</sup></td><td>Kasprzyk-Hordern et al. (2007)<br>Locatelli et al. (2011)</td></tr><tr><td>Trimethoprim</td><td>2 to 264 ng L<sup>-1</sup></td><td>6.9ng L<sup>-1</sup><br>Not detected</td><td>Petrović et al. (2014)<br>Locatelli et al. (2011)</td></tr><tr><td>Erythromycin</td><td>78 to 114ng L<sup>-1</sup></td><td>470 to 810ng L<sup>-1</sup><br>9.1ng L<sup>-1</sup><br>5ng L<sup>-1</sup></td><td>Gulkowska et al. (2006)<br>Petrović et al. (2014)<br>Boix et al. (2015)</td></tr><tr><td>Sulfamethoxazole</td><td>1.9 to 553ng L<sup>-1</sup></td><td>106ng L<sup>-1</sup><br>0.3 to 56.8ng L<sup>-1</sup></td><td>Locatelli et al. (2011)<br>Yan et al. (2013)</td></tr><tr><td>Tetracyclin</td><td>111.4 to 286ng L<sup>-1</sup></td><td>39.3 to 142ng L<sup>-1</sup><br>11ng L<sup>-1</sup></td><td>Tamtam et al. (2008)<br>Locatelli et al. (2011)</td></tr><tr><td>Oxolinic acid</td><td>12.2 to 64ng L<sup>-1</sup></td><td>2 to 5ng L<sup>-1</sup><br>25 to 140 ng L<sup>-1</sup></td><td>Sørensen et al. (2004)<br>Tamtam et al. (2008)</td></tr><tr><td>Ciprofloxacin</td><td>8 to 1058ng L<sup>-1</sup></td><td>2.5ng L<sup>-1</sup><br>0 to 28.2ng L<sup>-1</sup><br>0 to 1250ng L<sup>-1</sup></td><td>Locatelli et al. (2011)<br>Petrović et al. (2014)<br>Verlicchi et al. (2014)</td></tr></tbody></table>
Adoption of effective proceeds in WWTP's must be applied to eliminate antibiotics. A risk assessment of antibiotic residues study will be very helpful to target the environmental impacts, to sensitize population and medical professional about the severity of the antibiotic presence in environment and to seek urgent actions.

## Study Limitation

To perceive the variations of the antibiotics in water body, and significant variations among the sampling sites, a risk assessment of antibiotic concentration will be dealt in our next article. Also, there is a need to demonstrate the contribution of hospitals effluent, WWTP's and agricultural activities in the hydrological system.

## Acknowledgement

This work was supported by Faculty of Medicine, USMBA, Fez.

## Ethics

This article is original and contains unpublished material. The corresponding author confirms that all of the other authors have read and approved the manuscript and no ethical issues involved.

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