Antimicrobial Resistance in Escherichia coli Isolates from Healthy Poultry, Bovine and Ovine in Tunisia: A Real Animal and Human Health Threat

A total of 174 E. coli isolates collected from healthy poultry, bovine and ovine recovered between December 2009 and June 2013 in different geographic location in Tunisia, were assessed and examinated for resistance to antimicrobial agents. Avian isolates showed the highest rates of antibiotic resistance: tetracycline (74.7 %), trimethoprim/sulfamethoxazole and amoxicillin with the same rate of resistance (57 %). Prevalences of resistance to the same four antimicrobials in bovine isolates were 33.3 %, 65 %, 30 %, 28.3 %, respectively. However, for ovine isolates, low resistance rates were observed, except for tetracycline (40 %) and amoxicillin (22.85 %). Only one ESBL-producing isolate from chicken was detected. In addition, seventy-seven (44.2 %) isolates were resistant to three or more classes of antibiotics and were considered multidrug resistant (MDR). Interestingly, avian E. coli isolates were more resistant than bovine and ovine ones. These results provide novel insights into the epidemiological characteristics of poultry, bovine and ovine E.coli isolates in Tunisia, and suggest the need for the prudent use of antimicrobial agents in husbandry and the urgent need to establish a national antibiotic resistance monitoring program. Research Article Antimicrobial Resistance in Escherichia coli Isolates from Healthy Poultry, Bovine and Ovine in Tunisia: A Real Animal and Human Health Threat Mohamed Salah Abbassi1*, Hajer Kilani1, Mohamed Zouari3, Riadh Mansouri1, Oussama El Fekih1, Salah Hammami1 and Noureddine Ben Chehida1 1Institute of Veterinary research of Tunisia, Bab Saadoun, 1006 Tunis, Tunisia 2University of Tunis El Manar, Faculty of Medicine of Tunis, LR99ES09 Laboratory of Antimicrobial Resistance, Tunis, Tunisia 3Offi ce des Terres Domaniales de Mateur, Tunisia Dates: Received: 06 February, 2017; Accepted: 18 March, 2017; Published: 20 March, 2017 *Corresponding author: Abbassi Mohamed Salah, Institute of Veterinary Research of Tunisia, 20 Street Jebel Lakhdhar, Bab Saadoun, Tunis 1006, Tunisia, Tel: 00216 71 561 070; Fax: 00216 71 569 692; E-mail: https://www.peertechz.com


Introduction
Multi-drug-resistant bacteria have emerged as a major concern for human and veterinary medicine. To fi ght against this worrisome problem, reliable data on the rates of antimicrobial resistance in bacteria isolated from both human and animal are required. Therefore, it is necessary to develop monitoring programs to survey for the objective the extent of antimicrobial resistance [1,2]. Continued surveillance of the antimicrobial susceptibility profi les of foodborne pathogens, including Escherichia coli, has been strongly recommended to identify emerging antimicrobial-resistant phenotypes [3]. E.
coli is a common component of the gut fl ora of food animals that can serve as an indicator for the acquisition of resistance to various antibiotics by enteric organisms [4,5]. The use of E. coli as the indicator bacteria is also appropriate because changes in the antibiotic resistance of this species may serve as an early warning of the development of resistance by related pathogenic bacteria [5]. Although, antimicrobial therapy is an available tool for treating clinical infections, antibiotic resistance in pathogenic bacteria from human, animal and environmental sources is recognized as a global problem in public health. Especially, the high degree of resistance to common antibiotics, the worldwide emergence of multidrug resistant phenotypes (MDR) and extended spectrum -lactamases (ESBLs)-producing E.coli strains are of increasing concern [6,7]. A number of studies have reported that antimicrobial drugs commonly used for the treatment of human infections are misused in animals either for therapy or prevention, which has signifi cant clinical implications for both human and veterinary medicine [8,9].
Resistant bacteria can compromise public and animal health and lead to severe economic losses in animal production [10,11].
Nowadays, the resistance to antimicrobial agents increased signifi cantly for E. coli [12]. Initially, this resistance was described for certain antimicrobial agents such ampicillin, trimethoprime, sulphonamides and tetracycline [13]. However, since many years, large phenotypes of resistance have been observes such as resistance to all beta-lactams, aminosides, and quinolones.
Many studies on antimicrobial resistance in E. coli strains isolated from human origins in Tunisia have been published. In addition, same studies have been published, where genetic characterization of ESBL-producing E. coli isolates from animal origins and from food products of animal of origin. However, little is known about the antibiotic resistance in commensal E. coli from livestock. Indeed, it is very important to know the actual epidemiology of antibiotic susceptibility of E. coli from livestock in order to establish a guide for Tunisian veterinarians for the reasonable use of antibiotic in husbandry. For these reasons, we carried out this study to investigate antimicrobial resistance in E. coli isolates from healthy poultry, bovine and ovine during a period of 4 years and 6 months (June 2009 to December 2013). E. coli ATCC 25922 was used as a control strain. The double-disc synergy test with cefotaxime or ceftazidime in the proximity to amoxicillin-clavulanic acid was used for the screening of Extended-Spectrum Beta-lactamases (ESBL) [16].

Statistical analysis
Statistical testing was performed using SPSS version 12.0. P < 0.05 was considered statistically signifi cant.
coli isolate of avian origin was detected.

Discussion
The aim of our study was to identify the profi les of antibiotics resistance for a collection of E. coli isolates (174) recovered from apparently healthy poultry, bovine and ovine.
Our work showed high rates of resistance to tetracycline and streptomycin. Average rates of resistance were noted for amoxicillin, trimethoprim/sulfamethoxazole, nalidixic acid and ciprofl oxacin. Low frequencies were observed for the resistance to amoxicilline/clavulanic-acid, gentamicin, cefotaxime and ceftazidime. A single ESBL producing strain was detected from chicken. High rates of resistance to tetracycline and streptomycin have been reported previously [17]. These antibiotics were the oldest molecules very widely used in veterinary medicine [18]. Indeed, tetracycline was usually used in the treatment of omphalites, respiratory infections, whit lows and interdigites dermatitis in ruminants as well as respiratory diseases and enteritis in poultry; it was also used as a growth promoter. Streptomycin is used for the treatment of diarrhea and streptococcal infections. These two molecules (streptomycin and tetracycline) are used very frequently and for a long time in the poultry sector. Studies made by other authors [14,19] were in agreement with our fi ndings. Indeed, they showed a high rates of resistance to tetracycline (90.8-95.2 %), and streptomycin (46 %). High rates of antibiotic resistance in E. coli towards tetracycline were reported at most species breeding [8,[20][21][22]. Although frequencies of streptomycin resistance vary according to countries and conditions of breeding, the reported rates were generally very high whatever the type of animal species [8,[20][21][22].
A moderate rate of resistance was noted for trimethoprimsulfamethoxazole (39 %), similarly to other studies from many countries (66.1-88.6 %) [23][24][25][26]. However, a very high frequency of resistance to trimethoprim -sulfamethoxazole (80 %) was reported in our previous work [27]. Trimethoprim is used in medicine against a wide specter of bacteria including E. coli and other enterobacteria. Furthermore, the combination with sulfonamides increases its effi ciency. However, the use of this antimicrobial in the animal feed, as well as its use in uncontrolled way in human medicine, during a prolonged time can entail the development and the transmission of genes encoding this resistance marker [27].
The mechanisms of resistance to beta-lactams in E. coli from animal origins is mainly encoded by extended spectrum beta-lactamases (ESBL) [28][29][30][31][32][33]. In this study, a single isolate producing ESBL from poultry origin, was identifi ed. In Tunisia, the presence of isolates producing ESBL was reported for the fi rst time by [34], from poultry meat, by using a selective protocol for the isolation of these isolates. However [35], did not identify ESBL-producing isolates from 164 isolates by using a non-selective protocol. [36], were the fi rst researchers in Tunisia to report ESBL-producing E. coli from avian feces using a selective protocol. Moderate rates of resistance were observed for quinolones, nalidixic acid (28.7 %) and ciprofl oxacin (18.4 %). Actually, worldwide, high rates of quinolones-resistance are increasingly reported in E. coli from animal origins.
Our study showed that antibiotics resistance rates in E.
coli varied according to the animal species. Indeed, and for all antibiotics, except for streptomycin in bovine isolates, avian isolates were the most resistant ones, especially for tetracycline, streptomycin, trimethoprim/sulfamethoxazole, and amoxicillin. On the other hand, in cattle, the resistance rates were lower and concern only streptomycin, tetracycline and trimethoprim/sulfamethoxazole.
The results concerning the frequencies of antibiotic resistance in poultry are in agreement with other studies   isolates were resistant to 3 families of antibiotics or more. In