Enterococci are the normal gastrointestinal flora of humans and animals that today, as a hospital pathogen, they can create a variety of diseases in hospitalized patients . The spread of these potentially pathogenic enterococci from the hospital environment or other sources could enhance the outbreak of these strains in the human population as a risk factor to human health . We found that, in concordant with another Iranian research on the clinical isolates of enterococci , all gentamicin-resistant isolates of our study were possessed the aac(6´)-Ie-aph(2´´)-Ia resistance gene. However, 20% of our hospital environmental isolates of enterococci were high-level gentamicin resistant (HLGR), and among all Enterococcus isolates of the present study, 26 (28.8%) isolates were contained this gene. This range was 42.8% in E. faecalis isolates, although 16.6% of E. faecium isolates were carrying this gene. However, a research in 2016, conducted in Iran , showed that 32.8% and 67.2% of their E. faecium and E. faecalis clinical isolates were contained aac(6´)-Ie-aph(2´´)-Ia, respectively, while the prevalence of aph(3´)-IIIa gene was 77.3% and 22.7%, respectively, which both of them were more prevalent than our study. However, another Iranian study on burn patients showed that 65.2% of their E. faecalis isolates were detected as HLGR, while 47.8% of them had aac(6´)-Ie-aph(2´´)-Ia gene . This data confirmed that the prevalence of these genes in clinical Enterococcus isolates is higher than the environmental isolates, may be due to the high prescription of aminoglycosides for treatment of infections caused by Gram-negative bacteria and enterococci in Iran. This was in concordant with a study carried out in India , from which aac(6´)-Ie-aph(2´´)-Ia and aph (3´)-IIIa genes were detected in 39.5% and 37.5% of their clinical isolates, respectively. Also, the prevalence of aac(6´)-Ie-aph(2´´)-Ia in enterococci isolated from non-hospital samples and surface waters in Thailand were reported as 0.9% and 1.6%, respectively . While, the prevalence of E. faecalis and E. faecium isolated from wastewater containing this gene in Tunisia were 5.8% and 3.7%, respectively . The emergence of high-level gentamicin resistance in enterococci, and concurrent resistance to ampicillin and vancomycin due to the role of the same plasmid in the transfer of their genes were reported in some studies [3, 27]. Considering such a finding, the detection of HLGR strains together with vancomycin-resistant enterococci in this research displays an alarming situation in our region. Vancomycin-resistant enterococci (VRE) have led to hospital prevalence worldwide, and vanA gene has connected to methicillin-resistant S. aureus . While we detected this gene just in 8.8% of E. faecium isolates and our E. faecalis ones were negative, in an Australian research in 2012 , any vancomycin-resistant strains isolated from water were contained this gene. However, some of their E. faecium and E. faecalis clinical isolates were carrying vanA and vanB genes, indicating the more prevalence in clinical isolates than environmental ones. Moreover, a research conducted in Iran , exhibited that all of their E. faecalis isolated from burned patients were susceptible to vancomycin and the vanA and vanB genes were not found. This range in Italy was 10.7% and 0.7% among meat and environmental isolates of glycopeptide resistant Enterococcus (GRE), respectively . Also, we detected that all of our isolates carrying vanA and vanB genes were detected as tetL, tetM, and esp positive, while 4 of them were contained aac(6´)-Ie-aph(2´´)-Ia and aph (3´)-IIIa genes, too, and 2 isolates had all resistance and putative virulence genes tested in the current study. The most common antibiotic resistance phenotype in enterococci is tetracycline resistance . In the present study, 60% of enterococci isolates were positive for tetM and tetL, this range in animal meat samples and clinical specimens were different in research conducted by Ebru Sneb Yılmaz et al. . In addition, in Tunisia, just 3.7% and 11.7% of E. faecium and E. faecalis isolated from wastewater and surface water samples carrying the tetM gene . In the most studies on enterococci in the world, similar to the present research, the resistance rate to erythromycin is equal to the level of resistance to tetracyclines, and among them, the ermB resistance gene was the most prevalent in both E. faecalis and E. faecium erythromycin-resistant isolates [2, 14, 30, 31]. In the current study, in addition to all 56 erythromycin-resistant environmental isolates of enterococci, 4 intermediate resistant isolates were contained the ermB gene, too. This ermB high prevalence was concordant to all above-mentioned studies worldwide, may be due to the role of mosaic plasmids harboring Tn1546-ermB element transferable among S. aureus and Enterococcus Spp., as a developing problem requiring constant monitoring . Meanwhile, almost 43% of the enterococci isolated from the waste and surface waters were carrying this gene , but the prevalence of ermB gene among the erythromycin-resistant clinical isolates of enterococci in Spain  was almost similar to our study . However, the prevalence of ermB gene in E. faecalis isolated from burned patients was 54.3% , in concordant to Bulgarian research , which 59.5% of their clinical isolates contained this gene, while just 4.3% of their E. faecium isolates were ermB positive. According to the prescription of erythromycin in different countries, the prevalence of ermB gene in enterococci is varied, as just 33% of the clinical E. faecalis isolated from Mexico were carrying the ermB gene, while all of them were susceptible against vancomycin and 62% of their isolates were resistant to tetracycline . On the other hand, in a study conducted in Turkey, the higher prevalence of tetracycline resistance genes in enterococci isolated from chicken meats than beef was observed about the ermB gene, too . However, 76% and 83.8% of E. faecalis and E. faecium isolated from slaughter pigs in Australia were detected as the ermB positive, respectively, in 2011 . These data indicate that the hospital environments, waters and animal isolates of enterococci could be the major sources of the ermB resistance gene transferring it to the clinical isolates by plasmids. However, among hospital environmental isolates in Tunisia, 97.3% of them were resistant to erythromycin and all tetracycline and vancomycin-resistant, were contained tetM and vanA genes, respectively . Considering the antibiotic resistance pattern of the enterococcal isolates, we found that linezolid and nitrofurantoin are the most effective antibiotics for treatment of possible infections caused by our environmental isolates in immunocompromised hospitalized patients. However, even erythromycin or tetracycline intermediate resistant and non-HLAR isolates of the present study were carrying the resistance genes. Another thing to consider in this study is that we also tested ampicillin in this study, although the bacterium is almost inherently resistant to this antibiotic. We had two reasons for this: 1) because the CLSI has recommended this drug for antibiotic susceptibility testing. 2) because in our area the use of this antibiotic has reached the lowest possible level, and we wanted to investigate whether the rate of enterococci ampicillin resistance could be reduced. We concluded that this is possible, because only 24.4% of our isolates were resistant to this antibiotic. The esp gene was defined as characteristic to hospital strains and claimed to be greatly correlated to the capability of the isolates to cause health-care associated infection . The importance of the presence of esp and ace genes in the biofilm synthesis process was highlighted by the results of a study conducted by Papadimitriou, et al., 2015 . In the present study, 97.7% of the isolates had esp gene, while 17.7% of them were contained the ace gene. According to the study conducted in China, ace gene was found in 92% of environmental enterococcal strains (23/25). This difference may be due to the various samples which used in two types of research . However, in a study conducted in Mexico, 39% of the E. faecalis clinical isolates were ace positive . E. faecalis and E. faecium can survive outside the host for a long time using the biofilm construction, as well as being able to resist routine cleaning and antibiotics due to the possession of resistance genetic elements, contaminate the environments and transfer to hospitalized patients by contact with the medical equipments, other patients, and contaminated surfaces [31, 39].