Antimicrobial resistance remains a significant challenge for global health in clinical control and infection prevention. According to a global report, more than 1.2 million people died worldwide in 2019 from infections caused by antibiotic-resistant bacteria [1]. Of particular concern is the rise in antimicrobial resistance associated with extended-spectrum beta-lactamase (ESBL)-producing bacteria, which has seen an increase in hospital and community settings in recent years [2]. The proliferation of antimicrobial resistance is significantly fuelled by the overuse of antibiotics in human medicine and animal husbandry, particularly in sub-Saharan Africa [3]. In the absence of intervention, projections suggest that within 5 years (2030), infections due to antimicrobial resistance will pose a substantial threat to the global economy, with low- and middle-income countries (LMICs), particularly in sub-Saharan Africa, bearing a disproportionate burden [4].

In low-income countries, the lack of enforcement of regulations and guidelines to control the sale and unreasonable use of antibiotics in animals and humans has contributed to the emergence and spread of resistant bacteria [5]. The problem with antimicrobial resistance is that it leads to more extended hospital stays and the need for more expensive drugs, which are often not readily available in resource-limited countries like Togo due to the inability to treat bacteria that are resistant to locally available antimicrobial agents [6][7].

In Africa, the prevalence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae during infectious processes remains high, fluctuating between 30% and 50% [8]. In Ghana, a study carried out at Korle-Bu Teaching Hospital revealed that almost half of all enterobacteria isolated from clinical infections (49.4%) were ESBL producers [9][10]. In Togo, the few data available come from surveys carried out between 2009 and 2011 to determine the frequency of ESBL strains and assess their antibiotic susceptibility profile. The prevalence of ESBL Enterobacteriaceae was estimated at 22.44%, with a predominance of Escherichia coliand Klebsiellaspp. both showing marked resistance to most antibiotics tested [11]. Initially, these ESBL-producing bacteria were considered purely nosocomial [7]. As causative agents of serious infections, they pose a significant problem for hospitalized patients. However, community-acquired infections and healthy fecal carriers have also been reported [12].

Although transmission of Enterobacteriaceae producing extended-spectrum-β-lactamase has been studied extensively in clinical settings [12], little is known about the risk and routes of transmission in the general population. This transmission is favored by poor hygiene (fecal hazard). Because latrines do not exist in some parts of our developing world, fecal matter enters the environment and can contaminate water, food, and plants. Animal and human populations, therefore, remain at high risk of contamination by Enterobacteriaceae that produce broad-spectrum-β-lactamases. Because the hospital environment is also conducive to the spread of multidrug-resistant bacteria, the admission of patients with ESBLs is a significant contributor to the spread of these antimicrobial resistance genes.

Thus, the present work aimed to investigate the transmission of ESBL-producing Enterobacteriaceae in the digestive tract of ambulatory patients and the factors associated with this transmission and indirectly to determine the presence of a community reservoir of ESBL-producing Enterobacteriaceae in this region of southern Togo.

Resistance of bacteria, particularly Enterobacteriaceae, to antibiotics is a real public health problem. This resistance affects both developed and especially developing countries, where self-medication and the anarchic sale of drugs outside legal structures coexist [17]. In West African countries, the endemicity of diarrheal diseases and other infectious diseases has increased the consumption of antibiotics [18]. In this study, we aimed to determine the prevalence of ESBL-producing Enterobacteriaceae in the digestive tract of non-hospitalized adult patients treated at Saint Jean de Dieu Afagnan Hospital.

Enterobacteriaceae were isolated from predominantly female patients (62.9%) during our study. This observation can be justified because they are often responsible for the sick and household chores. In our study, five different species of Enterobacteriaceae were isolated, with a predominance of Escherichia coli(66.1%), followed by Klebsiella pneumoniae (14.5%) and Klebsiellaoxytoca (9.7%). On the other hand, the species poorly represented were Enterobacter spp (6.5%) and Citrobacter spp (3.2%). The same observation was made by Onduru et al. [19]. These authors showed that the species most frequently isolated from outpatients attending community health centers in Blantyre, Malawi was Escherichia coli(66%), followed by Klebsiella spp (8%). These results could be explained by the fact that E. coli strains, being a commensal species and an opportunistic pathogen commonly found in the intestinal tract of animals and humans [20], are considered an indicator organism of antibiotic resistance for many bacteria [2].

The resistance of Enterobacteriaceae isolates varied among antibiotics. The antibiotic susceptibility profile showed that isolates of E. coli were susceptible to tobramycin and imipenem and very resistant to amoxicillin. This result agrees with previous studies showing that isolates from urine samples were susceptible to imipenem [21]. In this study, tobramycin and imipenem proved to be the most effective antimicrobials against isolates of Enterobacteriaceae from stools in outpatients at Saint Jean Hospital. At the same time, these strains of Enterobacteriaceae showed high resistance to trimethoprim/sulfamethoxazole and amoxicillin + clavulanic acid. Our results are alarming and call for urgent measures to control the threatening development of antibacterial resistance, particularly to Amoxicillin, Trimethoprim/sulfamethoxazole, and Amoxicillin + clavulanic acid, in the region. As for the cephalosporins, 17.7%, 8.1%, 11.3%, and 14.5% of the strains were resistant to Cefuroxime, Ceftazidime, respectively, Cefotaxime, and Cefixime. Our results are contrary to those obtained by Li et al. . These authors showed that bacteria isolated from fecal samples of patients with diarrhea were highly resistant to cefazolin, ceftriaxone, and cefuroxime. These differences in the antibiotic susceptibility pattern could be attributed to the time difference between the two studies, population variations, and significant differences in sample sizes and types. Levofloxacin, the only fluoroquinolone tested in the study, was 100% sensitive to strains isolated from E. coli, of which 22% were resistant. Fluoroquinolones are a widely used family of antibiotics. This family has not been spared from bacterial resistance either, the levels of which are becoming worrying. Several mechanisms may explain the resistance of EPBLSEs to fluoroquinolones. This resistance can be either chromosomal or plasmid. Chromosomal resistance is mainly manifested by the modification of the enzymatic target of the fluoroquinolones, which are DNA-gyrase and topoisomerase IV, by the reduction in the intracellular concentration of the antibiotic which is done by reducing the production of porins or by modification of the activity of various efflux pumps . One of the genetic determinants of the plasmid resistance of Enterobacteriaceae to Fluoroquinolones is the qnr gene, the main characteristic of which is to be carried by a class 1 integron which is highly mobile between different plasmids [23].

On the other hand, 6.45% of the Enterobacteriaceae strains were resistant to gentamicin. This record can be attributed to the use and abuse of antibiotics in the area studied. In our societies where drugs continue to be sold on street corners, where the hospital is generally the last resort after risky and sometimes disastrous self-medication, inevitably, 90% of the population has already had access to antibiotics such as amoxicillin, which would explain the acquired resistance to the latter within the population of E. coli. The excessive and uncontrolled use of Co-trimoxazole would also be at the origin of the resistance of 61.3% observed within the population. Indeed, sulfonamides and trimethoprim have been used for several decades as effective and inexpensive antibacterial agents in animals and humans [24]. This observation would explain the resistance to these two agents, which has spread widely and rapidly.

In this study, the prevalence of Enterobacteriaceae strains possessing the study ESBL genes was 12.9%. This prevalence is close to that found in a study conducted in Iran by Agha Mohammad et al. [25]. These authors showed that the prevalence rate of ESBL fecal carriage was 18.3% among patients in intensive care units and outpatients. The majority of studies have focused on humans in the context of infectious diseases and antimicrobial resistance, and we have observed a human prevalence of 20.23% in sub-Saharan Africa [26]. Fecal carriage of ESBL in patients with urinary tract infections was reported to be 35% in another study by Bazargani et al. [27] The incidence of fecal carriage was estimated to be high in these patients due to frequent hospital visits, frequent contact with medical personnel and devices, food intake, and antibiotics [28]. According to the literature, E. coli represents the most isolated ESBL-producing species. Our study confirms that E. coli carried 87.5% of ESBL genes. Since the 2000s, the number of publications concerning the emergence of E. coli possessing BlaCTX-M, BlaSHV, and BlaTEM genes has exploded [29]. Our results are contrary to those obtained by Gadou (2019) [23]. The author showed that the β-lactam resistance genes detected were the BlaCTX-M-1 (96.7%), blaTEM (67.8%), blaSHV (27.8%), and blaCTX-M-9 (5.56%). This difference in the proportions of genes between the studies may be explained by the fact that our strains are not producers of the ESBL used in each of them. The observations of a low level of resistance to Cefuroxime, Ceftazidime, Cefotaxime, and Cefixime among the strains analyzed in the present study explain this difference.

The absence of synergy on the antibiogram of the 12.9% strains carrying the blaCTX-M, blaTEM, and blaSHV genes suggests the presence of hyperproduced cephalosporins of the chromosomal or plasmid type. According to the antibiogram committee of the SFM, ESBL-producing strains would have other mechanisms of resistance to beta-lactams, such as the hyperproduction of cephalosporins; in this case, the image of synergy could have been facilitated by bringing together the cephalosporin discs and that of the clavulanic acid disc or by carrying out a standard antibiogram on Mueller-Hinton agar supplemented with 250 mg/L of Cloxacillin (inhibitor of cephalosporins) (French Society of Microbiology, 2020) [14]. Preventing and implementing measures to limit the spread of EPBLSE requires correct detection of these bacteria. Unfortunately, this detection can be complex, mainly due to the complexity of the resistance mechanisms that accumulate within the same microorganism and the variability in the expression of the corresponding resistance factors. According to Chassagne, the phenotypic detection of the mechanisms in question is increasingly complex, especially since the same resistance can be due to different associated mechanisms [19]. Our study shows the limits of the double disc synergy test for detecting ESBL production. According to some studies, this synergy test can also give false positives [13]. All this, therefore, makes the task of a medical biology laboratory easier, as it usually only has a limited number of phenotypic methods. The phenotypic characterization seems insufficient to apprehend the problem insofar as the cause of these resistances resides at the level of the genes. The coexistence of blaCTX-M, blaTEM and blaSHV genes with a negative synergy test may be explained by low or silent expression of these genes, or by their functional inhibition by other resistance mechanisms [30][31]. This discrepancy between genotype and phenotype underlines the need for an integrated approach combining molecular and phenotypic methods for reliable ESBL detection .

Another part of our study focused on the presence of virulence factors stx1 in strains of E. coli in Patients in Outpatient Consultation at Saint Jean de Dieu Hospital in Afagnan in southern Togo. The absence of this factor in strains of E. coli has shown their low pathogenicity for humans and, in particular, for patients. Our results are contrary to those obtained by Ranjbar et al. [32]. These authors showed a strong presence of the stx1 genes in the strains of E. coli from hospital foods. This difference could be explained by the fact that the samples are different, and our strains do not express the enzymes blaCTX-M, blaTEM, and blaSHV.

This study confirms the existence of a community reservoir of ESBL-producing Enterobacteriaceae in southern Togo. Our results reveal an absence of ESBL phenotypes in Enterobacteriaceae strains of Patients in Outpatient Consultation at Saint Jean de Dieu Hospital in Afagnan in southern Togo. Some of its Enterobacteriaceae possess the genes coding for the production of ESBLs. These results suggest community acquisition of ESBL Enterobacteriaceae at Saint Jean de Dieu Hospital in Afagnan. Suppose these carrier patients in the community are not treated. In that case, they may serve as a community reservoir of resistant pathogen potential for transmission and the spread of acquired ESBLs in the community. The low prevalence of ESBL Enterobacteriaceae in community settings makes it necessary to monitor the prevalence and transmission of Enterobacteriaceae, which possess the genes coding for ESBL production.