Original Article

Prevalence of Virulence Factors and Vancomycin-Resistant Genes among Enterococcus faecalis and E. faecium Isolated from Clinical Specimens


Background: The aim of this study was to determine the occurrence of virulence determinants and vancomycin- resistant genes among Enterococcus faecalis and E. faecium obtained from various clinical sources.

Methods: The study was performed on the 280 enterococcal isolated from clinical specimens in Hamadan hospitals, western Iran in 2012-14. Antibiotic susceptibility testing was performed using disk diffusion and Minimal Inhibitory Concentration (MIC) methods. The presence of vancomycin-resistant genes and virulence genes was investigated using PCR.

Results: Totally 280 enterococcal isolates were identified as follows: E. faecalis (62.5%), E. faecium (24%) and Enterococcus spp (13.5%). The results of antibiotic susceptibility testing showed that resistance rates to vancomycin and teicoplanin in E. faecalis and E. faecium isolates were 5% and 73%, respectively. Of Sixty vancomycin-resistant Enterococci strains, fifty-one isolates were identified as E. faecium (VREfm) and nine as E. faecalis (VREfs). Prevalence of esp, hyl, and asa1 genes were determined as 82%, 71.6%, and 100%, respectively in E. faecium strains; and 78%, 56/6%, and 97%, respectively in E. faecalis strains.

Conclusion: The increased frequency of VREF, as seen with rapid rise in the number of vanA isolates should be considered in infection control practices.



Xu H, Tian R, Chen D, Xiao F, Nie ZY, Hu YJ, et al. (2011). Nosocomial spread of hospital-adapted CC17 vancomycin-resistant Enterococcus faecium in a tertiary-care hospital of Beijing, China. Chin Med J, 124 (4):498-503.

Vagnerova I, Sauer P, Kolar M, Slepickova S, Hubacek J, Faber E, et al (2006). Sources and pathways of spread of vancomycin-resistant en¬terococci in hemato-oncological patients. Bio¬med Pap Med Fac Univ Palacky Olomouc Czech Repub, 150 (1):117-20.

Batistão DWdF, Gontijo-Filho PP, Conceição N, Oliveira AG, Ribas RM (2012). Risk factors for vancomycin-resistant enterococci colonization in critically ill patients. Mem Inst Oswaldo Cruz, 107(1):57-63.

Hegstad K, Giske CG, Haldorsen B, Matuschek E, Schønning K, Leegaard TM, et al (2014). Per-formance of the EUCAST disk diffusion method, the CLSI agar screen method, and the Vitek 2 au-tomated antimicrobial susceptibility testing system for detection of clinical isolates of enterococci with low-and medium-level VanB-type vancomycin re-sistance: a multicen¬ter study. J Clin Microbiol, 52 (5):1582-9.

Sharifi Y, Hasani A, Ghotaslou R, Varshochi M, Hasani A, Aghazadeh M, et al (2012). Sur¬vey of virulence determinants among vancomy¬cin re-sistant Enterococcus faecalis and Entero¬coccus faecium isolated from clinical specimens of hospi-talized patients of North west of Iran. Open Microbiol J, 6:34-39.

Ji GY, Son BR, Kim JW (2014). Development of a Novel Immunochromatographic Assay for Rapid Detection of VanA Ligase-Producing Vancomy-cin-Resistant Enterococci. J Microbiol Biotechnol, 24:427-30.

Song JY, Cheong HJ, Seo YB, Kim IS, Heo JY, Noh JY, et al (2013). Clinical and microbiologi¬cal charac-teristics of vancomycin-resistant en¬terococci with the VanD phenotype and vanA genotype. Jpn J In-fect Dis, 66 (1):1-5.

Feizabadi MM, Sayadi S, Shokrzadeh L, Parvin M,YadegaryniA D (2008). Increase in preva¬lence of vancomycin resistant isolates of Entero¬coccous faecium at Labbafinejad hospital. Clin Infect Dis, 3 (2):123-26.

Mira M-U, Deana M, Zora J, Vera G, Biljana M, Biljan R (2014). Prevalence of different entero¬coccal spe-cies isolated from blood and their susceptibility to antimicrobial drugs in Vojvo¬dina, Serbia, 2011-2013. Afr J Microbiol Res, 8 (8):819-24.

Kariyama R, Mitsuhata R, Chow JW, Clewell DB, Kumon H (2000). Simple and reliable mul-tiplex PCR assay for surveillance isolates of van-comycin-resistant enterococci. J Clin Microbiol, 38 (8):3092-5.

Jahangiri S, Talebi M, Eslami G, Pourshafie MR (2010). Prevalence of virulence factors and an¬tibiotic resistance in vancomycin-resistant En¬terococcus faecium isolated from sewage and clinical samples in Iran. Indian J Med Microbiol, 28 (4):337-41.

Dutka-Malen S, Evers S, Courvalin P. Detection of glycopeptide resistance genotypes and identifi¬cation to the species level of clinically relevant enterococci by PCR. J Clin Microbiol, 1995;33(1):24-7.

Creti R, Imperi M, Bertuccini L, Fabretti F, Orefici G, Di Rosa R, et al (2004). Survey for virulence deter-minants among Enterococcus faecalis isolated from dif-ferent sources. J Med Microbiol, 53 (p1):13-20.

Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing; Twenty-Third Informational Supplement. CLSI document M100-S23. Wayne, PA: Clin Labora Stand Institu. 2013.

Mulla S, Patel KG, Panwala T, Rewadiwala S (2012). Prevalence of enterococci with higher resistance level in a tertiary care hospital: a mat¬ter of concern. Nat J Med Rse, 2 (1):25-27.

Ghalandarzadeh DZ, Javadpour S, Kargar M (2013). Frequency of vana & vanb genes in van¬comycin-resistant enterococci isolated from clinical speci-mens at shahid mohammadi hospi¬tals bandar ab-bass. J Microbiol Wrd, 6 (114):23-33.

Mohammadi F, Tabaraie B, Sadeghifard N, Ghafoo-rian S, Maleki A, Davoodian E, et al (2011). Evalua-tion of drug resistance frequency among Entrococci faecium and E. faecalis strains and detection of VanA/B genes in vancomycin resistance isolated by PCR method in ilam and kermanshah hospi-tals. J Ilam Univ Med Sci, 19:1-8.

Rafiei Tabatabaei S, Karimi A, Navidinia M, Fallah F, Tavakkoly Fard A, Rahbar M (2012). A study on prevalence of vancomycin-resistant enterococci carriers admitted in a children hospital in Iran. Ann Biol Res,3 (12):5441-45.

Daikos GL, Bamias G, Kattamis C, Zervos MJ, Chow JW, Christakis G, et al. (2003). Struc-tures, locations, and transfer frequencies of ge¬netic elements conferring high-level gentamicin re-sistance in Enterococcus faecalis isolates in Greece. Antimicrob Agents Chemother, 47 (12):3950-3.

Khair H, VanTassell P, Henderson J, Warren DK, Marschall J (2013). Vancomycin resistance has no influence on outcomes of enterococcal bacteriu-ria. J Hosp Infect, 85 (3):183-8.

Hoseinizadeh A, Abtahi H, ShojaPour M, Akbari M, Nazari R , Sofian M (2012). Prevalence and an-timicrobial susceptibility pattern of vancomy¬cin re-sistant enterococci isolated from clinical sample of educational hospitals in Arak. Arak Med Univ J, 15 (6):11-6.

Nateghian A, Robinson J, Arjmandi K, Vosough P, Karimi A, Behzad A, et al. (2011). Epidemi¬ology of vancomycin-resistant enterococci in children with acute lymphoblastic leukemia at two referral centers in Tehran, Iran: a descrip¬tive study. Int J Infect Dis, 15 (5):e332-5.

Shaghaghian S, Pourabbas B, Alborzi A, Askarian M, Mardaneh J (2012). Vancomycin-Resistant En-trococci colonization in chronic hemodialysis patients and its risk factors in southern Iran (2005-2006). Iran Red Crescent Med J, 14 (10):686-691.

Praharaj I, Sujatha S, Parija SC (2013). Phenotypic & genotypic characterization of vancomycin re¬sistant Enterococcus isolates from clinical speci¬mens. Indian J Med Res, 138(4): 549–556.

Resende M, Caierão J, Prates JG, Narvaez GA, Dias CA, d'Azevedo PA (2014). Emer¬gence of vanA vancomycin-resistant Enterococcus faecium in a hospital in Porto Alegre, South Bra¬zil. J Infect Dev Ctries, 8 (2):160-7.

Comerlato CB, Resende MCCd, Caierao J, Caierão J, d'Azevedo PA (2013). Presence of virulence factors in Enterococcus faecalis and Enterococcus fae¬cium susceptible and resistant to vancomycin. Mem Inst Oswaldo Cruz, 108 (5):590-5.

Sharifi Y, Hasani A, Ghotaslou R, Aghazadeh M, Milani M, Bazmany A (2013). Virulence and an-timicrobial resistance in Enterococci isolated from urinary tract infections. Adv Pharm Bull, 3 (1):197-201.

Kafil HS, Mobarez AM, Moghadam MF (2012). Multidrug resistant and most virulent Enterococcus faecium (strain 2653), isolated from hospitalized patient wound in Iran. Schol J Med, 2 (3):36-9.

Shankar V, Baghdayan AS, Huycke MM, Lindahl G, Gilmore MS (1999). Infection-derived Enter-ococcus faecalis strains are enriched in esp, a gene encod-ing a novel surface protein. Infect Immun, 67 (1):193-200.

Eaton TJ, Gasson MJ (2001). Molecular Screening of Enterococcus Virulence Determinants and Po¬tential for Genetic Exchange between Food and Medical Isolates. Appl Environ Microbiol, 67 (4):1628-35.

Medeiros AW, Pereira RI, Oliveira DVd, Martins PD, d'Azevedo PA, Van der Sand S, et al. (2014). Molecular detection of virulence factors among food and clinical Enterococcus faecalis strains in South Brazil. Braz J Microbiol, 45 (1):327-32.

Leavis HL, Willems RJ, Top J, Spalburg E, Mascini EM, Fluit AC, et al (2003). Epidemic and nonepidemic multidrug-resistant Enterococcus fae¬cium. Emerg Infect Dis, 9 (9):1108-1115.

Terkuran M, Erginkaya Z, ÜNAL E, Güran M, Kızılyıldırım S, Ugur G, et al. (2014). The rela-tionship between virulence factors and vanco¬mycin resistance among Enterococci collected from food and human samples in Southern Turkey. Ankara Univ Vet Fak Derg, 61:133-40.

Worth L, Slavin M, Vankerckhoven V, Goossens H, Grabsch EA, Thursky KA (2008). Virulence de-terminants in vancomycin-resistant Enterococ¬cus faeci-um vanB: clonal distribution, prevalence and signifi-cance of esp and hyl in Australian pa¬tients with haematological disorders. J Hosp Infect, 68 (2):137-44.

Kowalska-Krochmal B, Dworniczek E, Dolna I, Ban-ia J, Wałecka E, Seniuk A, et al (2011). Re¬sistance patterns and occurrence of virulence determinants among GRE strains in southwest¬ern Poland. Adv Med Sci, 56 (2):304-10.

Rice LB, Carias L, Rudin S, Vael C, Goossens H, Konstabel C et al (2003). A potential viru¬lence gene, hylEfm, predominates in Enterococcus faecium of clinical origin. J Infect Dis, 187 (3):508-12.

Duprè I, Zanetti S, Schito AM, Fadda G, Sechi LA (2003). Incidence of virulence determinants in clini-cal Enterococcus faecium and Enterococcus faecalis isolates collected in Sardinia (Italy). J Med Microbiol, 52 (Pt 6):491-8.

Lund B, Edlund C (2003). Bloodstream isolates of Enterococcus faecium enriched with the enter-ococcal surface protein gene, esp, show in¬creased adhesion to eukaryotic cells. J Clin Microbiol, 41 (11):5183-5.

Van Wamel WJ, Hendrickx AP, Bonten MJ, Top J, Posthuma G, Willems RJ (2007). Growth condi-tion-dependent Esp expression by Entero¬coccus faeci-um affects initial adherence and biofilm formation. Infect Immun, 75 (2):924-31.

IssueVol 45 No 6 (2016) QRcode
SectionOriginal Article(s)
E. faecalis E. faecium Vancomycin-resistant enterococci Minimum inhibitory concentration

Rights and permissions
Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
How to Cite
NASAJ M, MOUSAVI SM, HOSSEINI SM, ARABESTANI MR. Prevalence of Virulence Factors and Vancomycin-Resistant Genes among Enterococcus faecalis and E. faecium Isolated from Clinical Specimens. Iran J Public Health. 2016;45(6):806-813.