Resistance Profile of Vibrio spp. Strains Collected from Lagoon Bays and Wastewater in the City of Abidjan, Côte d'Ivoire, from January to June 2017

1. INTRODUCTION

Discharges of untreated wastewater to the environment can be a source of infection by pathogenic microorganisms from a variety of sources [1]. According to the World Health Organization, each year nearly 1.8 million people, 90% of whom are children under five years of age, die from diarrheal diseases [2]. However, globally, the vast majority of diarrheal diseases are attributable to poor quality drinking water and inadequate wastewater sanitation [3]. While wastewater sanitation has become an imperative for modern societies, African countries face serious challenges in terms of both water supply and wastewater disposal and treatment [4]. It should be noted that 78% of African cities do not have any formal sewerage disposal and treatment services, and where they exist, most of them are outdated [5]. In these countries, the inadequacy of sanitation networks and the fact that the majority of the population (more than 30% in Abidjan) is not connected to the sewerage system mean that untreated wastewater is discharged into the natural environment [4].

In Côte d'Ivoire, the city of Abidjan was developed on the periphery of the Ebrié lagoon. The lack of a real sanitation system leads to the abusive discharge of wastewater [domestic and agro-industrial wastewater] into the natural environment without prior treatment [6]. The lagoon thus becomes the obligatory receptacle for all the wastes generated by human activities [7]. These discharges are responsible for eutrophication and microbial pollution [8], which are particularly accentuated by the confinement of the water in the city's bays. The aquatic environment then becomes the reservoir of many microorganisms potentially pathogenic to humans [9]. The aquatic environment constitutes the natural habitat for bacteria of the genus Vibrio [10-12]. This work reports the presence of pathogenic bacteria in the Ebrié lagoon, that contribute to the endemic nature of certain waterborne diseases such as cholera, gastroenteritis and septicemia [8, 10, 13-16]. Unlike many enteric pathogens, vibrios are well adapted to survive outside humans naturally in the aquatic environment [17]. The ubiquity of these bacteria in the aquatic environment and the potential severity of these infections are a cause for concern, given the increasing resistance to different families of antibiotics of certain vibrios that are emerging pathogens [18-23]. Thus, the general objective of this work was to study antibiotic resistance in environmental bacteria of the genus Vibrio isolated from Ebrié Lagoon bays and wastewater.

2. MATERIALS AND METHODS

2.3. Identification of Vibrio cholerae O1 strains

The identification of V. cholerae O1 strains was carried out using specific serum immunosera by slide agglutination. Immune serum O1 (antibodies to V. cholerae O1, Bio-Rad^®F-92430 Mannes-la-coquette) was used.

3. RESULTS

4. DISCUSSION

The presence of V. cholerae in the waters of lagoon bays and sewage suggests faecal contamination caused by poor excreta management and open defecation at the edge of lagoons or in vacant lots at the edge of neighborhoods [28]. The presence of V. cholerae and V. parahaemolyticus in lagoon bays and sewage could pose serious problems that would be even more serious if these bacteria are resistant. The use of antibiotics, both in human and veterinary medicine, exerts selection pressure over commensal and pathogenic bacteria from humans or animals that can reach the natural environment [continental waters, coastal waters, or wastewater]. This could lead to the emergence and dissemination of antibiotic resistance genes in environmental microbial communities.

The existence of links between different ecological compartments leads to interest in the pathways of resistant bacteria and resistance genes in the environment. The resistance of these strains is independent of their origin [29].

The resistance of Vibrio spp documented so far to Beta-lactam is mediated by plasmid coding at the same time for many other antibiotics [30, 31]. Plasmid-mediated penicillinases have often been found in most gram-negative bacilli, the best known of which are the narrow spectrum penicillinases TEM1 and SHV1 [32]. A study carried out by Aucher in 1998 reports that ampicillin is generally inactive against the majority of vibrios. In this study, more than 30% of vibrio cholerae strains were resistant to Ampicillin. According to Guévard [22], this resistance is due to multiple mechanisms, including transferable plasmid and chromosomal resistance. The resistance of V. cholerae to 3rd generation cephalosporins (ceftriaxone, cefoxitin, and cefotaxime)is linked to the production of a cephalosporinase or Broad Spectrum Beta-Lactamase (ESBL). This enzyme-like resistance mechanism is developed in most Gram-negative bacilli [33]. Fluoroquinolones are generally active on V. cholerae, but this study showed an increase in the resistance of Vibrio to fluoroquinolone to about 50%. In general, vibrios are usually sensitive to beta-lactam antibiotics, aminosides, quinolones, tetracyclines, chloramphenicol, sulfonamides, trimethoprim, furans, nalidixic acid and fluoroquinolones. This study showed an increase in the resistance of Vibrio Cholerae strains to antibiotics. Indeed, this work observed a decrease in the sensitivity of most antibiotics to vibrio, unlike previous observations, in particular, that of Tiécoura in 2010 [34]. Multi resistance acquired through transferable genetic elements (plasmids, conjugative transposons, genomic islands) within Vibrionaceae has become very common [35, 36]. This ability of Vibrio cholerae non O1, non O139 to acquire genetic material that could modify its virulence and its resistance has also been demonstrated by Arteaga et al. [37].

This work has also shown that although it has been an accepted fact that the resistance of vibrio to antibiotics has increased in the endemic areas of Cholera [38], the resistance of these bacteria to Fluoroquinolones was a new observation in Côte d'Ivory to our knowledge.

Horizontal transfer of antibiotic resistance in V. cholerae is commonly associated with plasmids [39]. Other conjugative elements allow the acquisition of this resistance. For instance, a conjugative transposon called SXT confers resistance to several antibiotics [Chloramphenicol, Streptomycin, Ampicillin, Neomycin, Tetracycline, Gentamicin, Sulfonamide and Furazolidone] [40-42]. Unlike plasmids, the genome of the SXT transposon does not contain the genes necessary for autonomous replication and segregation. Nevertheless, this structure has all the genes necessary for its excision, transmission and integration into the chromosome. The presence of V. cholerae in wastewater supports the hypothesis that wastewater discharges contribute to an increase in bacterial contamination of lagoon bays. The distribution of bacteria in Ebrié lagoon bays and wastewater varies from one sampling site to another. The detection of V. parahaemolyticus in the lagoon bays (Boribana Attenuated) could be explained by the hydrodynamics and geographical location. This station is located in bays, where confinement reduces the flow velocity and water renewal rate [43]. Boribana's remoteness from the sea makes the water there less salty and more eutrophic. Given the halophilic nature of V. parahaemolyticus, it is not surprising that this organism is found in aquatic environments around the world, particularly in waters with a salinity intermediate between fresh and seawater. The combination of these factors creates a favorable environment for the survival and development of bacteria of the genus Vibrio.

CONCLUSION

The results of this study showed the presence of 2 Vibrio species among the strains isolated from the wastewater: Vibrio cholerae (V cholerae O1 and V cholerae non O1) and Vibrio parahaemolyticus, with a predominance of Vibrio cholerae non O1. The isolated strains showed resistance to at least one usually active antibiotic, indicating a relatively high circulation of resistant strains. Since the effective management of gastroenteritis is based primarily on the replacement of hydroelectrolytic loss and antibiotic therapy, the circulation of multi-resistant Vibrio spp may compromise the effectiveness of probabilistic treatments and explain treatment failures.

In view of this bacterial pollution in wastewater and lagoon bays, we can propose possible solutions to try to reduce the contamination: 1) - build a good sanitation system for the collection of domestic wastewaters; 2)build treatment centers for domestic wastewater and industrial effluents; and 3) implement actions to raise awareness of the community and prescribers on the rational use of antimicrobials in order to contribute to limiting the spread of resistant strains.

In an environmental context of preserving the quality of groundwater, lagoons and marine waters where wastewater is discharged without prior treatment, a study of the impact of emerging pollutants on the growth and resistance of these bacteria must be carried out, bearing in mind that there is a risk of proliferation of these strains in groundwater and on the sea surface by the coastal current.

REFERENCES