Presence Of Virulence Factor Genes Research Articles

The presence of virulence factor genes downregulates uterine AQP3 and alters glutathione peroxidase activity and uterine histopathology in canine pyometra.

Present study was designed to evaluate the role of virulence factor genes (papG, cnf1 and hylA) in the pathogenesis of canine pyometra. Antimicrobial susceptibility test and detection of virulence genes were performed Escherichia coli (E. coli) detected in uterine swab samples. Animals were divided into two groups based on the presence (VF+, n:14) or absence (VF-, n:7) of the virulence factor genes papG, cnf1 and hylA. Blood and tissue glutathione peroxidase activity, uterine histopathologic analysis and AQP3, ESR1, PGR, OXTR gene expressions were determined in both groups. Statistical analyses were performed using Stata version 15.1. All E. coli isolates were susceptible to amikacin, whereas resistant to ampicillin, amoxicillin/clavulanic acid and lincomycin. None of the isolates were susceptible to cefotaxime. E. coli isolates had at least one virulence gene. The most prevalent gene was fimH (100%), followed by fyuA (95.8%), usp (83.3%), sfa (75%), cnf1 and hlyA (70.8%) genes. Blood GPx activity was greater in VF+ animals. On the other hand, uterine tissue GPx activity was lower in VF+ group compared to the control group. Expression levels of AQP3 were upregulated more than fivefold in VF-dogs compared to the control group. In addition, AQP3 expression levels were found approximately threefold higher in VF (-) than VF (+) group (p < .05). Varying degree of inflammation noted for all animals with pyometra, but the presence of bacteria noted only in VF+ animals. In conclusion, the presence of virulence factor genes does not play a role in the histopathological degree of inflammation, the presence of bacteria was found to vary. Serum GPx activity increased in VF+ animals. While the hormone receptor expressions were similar, AQP expression was upregulated in the absence of virulence factor genes.

Exploring the resistome and virulome in major sequence types of Acinetobacter baumannii genomes: Correlations with genome divergence and sequence types

The increasing global prevalence of antimicrobial resistance in Acinetobacter baumannii has led to concerns regarding the effectiveness of infection treatment. Moreover, the critical role of virulence factor genes in A. baumannii's pathogenesis and its propensity to cause severe disease is of particular importance. Comparative genomics, including multi-locus sequence typing (MLST), enhances our understanding of A. baumannii epidemiology. While there is substantial documentation on A. baumannii, a comprehensive study of the antibiotic-resistant mechanisms and the virulence factors contributing to pathogenesis, and their correlation with Sequence Types (STs) remains incompletely elucidated. In this study, we aim to explore the relationship between antimicrobial resistance genes, virulence factor genes, and STs using genomic data from 223 publicly available A. baumannii strains. The core phylogeny analysis revealed five predominant STs in A. baumannii genomes, linked to their geographical sources of isolation. Furthermore, the resistome and virulome of A. baumannii followed an evolutionary pattern consistent with their pan-genome evolution. Among the major STs, we observed significant variations in resistant genes against “aminoglycoside” and “sulphonamide” antibiotics, highlighting the role of genotypic variations in determining resistance profiles. Furthermore, the presence of virulence factor genes, particularly exotoxin and nutritional / metabolic factor genes, played a crucial role in distinguishing the major STs, suggesting a potential link between genetic makeup and pathogenicity. Understanding these associations can provide valuable insights into A. baumannii's virulence potential and clinical outcomes, enabling the development of effective strategies to combat infections caused by this opportunistic pathogen.

Comparative study of virulence factor genes, β-hemolysis and biofilm production in invasive and colonizing enterococci

Objectives: In humans, enterococci are among the most important opportunistic pathogens. This study aims to compare invasive isolates obtained from blood cultures of patients with sepsis and endocarditis with colonizing isolates obtained from healthy donors’ stool samples. Methods: A case-by-case assessment was conducted on invasive infection cases to determine whether enterococci were involved in their pathogenesis. They were tested for the presence of virulence factor genes, β-hemolysis on agars supplemented with human and sheep blood, and biofilm forming capacity. Results: Three species of enterococci were identified among invasive isolates: Enterococcus faecalis, Enterococcus faecium, and Enterococcus durans. All endocarditis isolates were biofilm producers. Genes esp, gelE, asa1, ace, hyl, cylB, and cylA were present in 7 (41.2%), 11 (64.7%), 11 (64.7%), 13 (76.5%), 0, 3 (17.6%), and 1 (5.9%) invasive isolate, but none of them could be linked to a particular infection (sepsis or endocarditis). Colonizing isolates proved to have had more virulence factor genes, but the differences were not statistically significant. Members of that group produced a greater amount of biofilm when the ace gene was absent ( p = 0.047). The production of β-hemolysis by noninvasive strains was detected more frequently when agar was supplemented with human blood ( p = 0.021). In general, the presence of either cyl gene on that specific agar was in direct connection with the production of β-hemolysis: cylA ( p = 0.047) or cylB ( p = 0.020). Conclusion: We have been unable to establish any correlation between invasive isolates and any virulence gene carriage and biofilm formation. β-hemolysis was produced significantly more often by colonizing strains when agar had been supplemented with human blood.

Oral microbiota in patients with oropharyngeal cancer with an emphasis on &lt;i&gt;Candida&lt;/i&gt; spp.

Introduction. Interactions between the 2 microbiota components – bacteria and fungi – are of interest as diagnostic and prognostic markers in selection of treatment tactics for oncological patients.Aim. To study microbiota of the oral cavity in patients with primary squamous cell carcinoma of the oropharyngeal area before and after surgical intervention to find biomarkers for rational selection of antifungal drugs.Materials and methods. At the Surgical Department of Head and Neck Tumors of the N. N. Blokhin National Research Center of Oncology, three-component study was performed: investigations of spectrum of Candida spp. isolates, Candida spp. strains’ resistance to antifungals, and oral washes in primary patients before and after surgery. mALDI-Tof microflex LT (Biotyper, Bruker Daltonics, germany) was used for strain identification; Sensititre Yeast ONE, YO10 (Trek Diagnostic System, united kingdom) plates were used for determination of minimal inhibiting concentrations of anti fungals. values of minimal inhibiting concentrations were evaluated based on the European Committee on Antimicrobial Susceptibility Testing (EuCAST) criteria (version 10.0).Results. four-year observation of patients at the surgical department of head and neck tumors of the N. N. Blokhin National Research Center of Oncology showed that the most common species of Candida is C. albicans (73.5 % of cases). Candida spp. resistance to antifungals was detected only for fluconazole (9.3 % of cases) and micafungin (8.0 % of cases), mostly among C. albicans strains. In 31.8 % of primary patients, oral washes prior to surgery showed growth of Candida spp. (probably, tissue colonization). After surgical intervention, Candida spp. growth was detected in 36.4 % of cases, only 1 of which was diagnosed as invasive mycosis. In 54.5 % of cases before and in 72.7 % of cases after surgery, gram-negative rods were detected. After surgical intervention, percentage of enterobacteria and non-fermenters significantly increased: 59.1 % versus 27.3 % (p &lt;0.05) and 63.6 % versus 27.3 % (p &lt;0.02), respectively. prior to surgery, non-fermenting gram-negative bacteria were represented only by P. aeruginosa; after surgery, the spectrum of non-fermenting gram-negative bacteria became wider but percentage of P. aeruginosa remained high: 71.4 %. ERG11 gene was identified only in 1 strain: C. albicans. FKS1 gene also was identified only in 1 strain: C. inconspicua. virulence factor genes were detected in 57.1 % of strains.Conclusion. Surgical intervention is associated with changes in bacterial microbiota but not fugal microbiota. presence of virulence factor genes and resistance genes in Candida spp. strains should be considered a biomarker allowing to differentiate between colonization and candida infection and can be used for rational selection of antifungal drugs in prevention and treatment of invasive candidiasis, especially in the absence of criteria for interpretation of measured minimal inhibiting concentrations of antifungals.

Antibiotic resistance and virulence factor gene profile of A. hydrophila isolated from carp (Cyprinidae) suspected with hemorrhagic septicemia in Gilan, Iran.

The present study was conducted to determine the antibacterial resistance profile of Aeromonas hydrophila (n = 42) isolated from the 100 hemorrhagic septicemia-suspected carp in Gilan, Iran. The prevalence of class 1 and 2 integrons, antibiotic resistance genes (ARG) and virulence factor genes (VFG) among these isolates was investigated using PCR. Also, the possible association between the presence of VFGs and the antibiotic resistance profile of isolates was assessed. The majority of A. hydrophila isolates (83·33%) exhibited multi-drug resistance (MDR) profile, and all isolates were resistant to clindamycin, while all isolates were susceptible to amikacin. intI1 and intI2 gene was found in 26·2 and 4·8% isolates, respectively. This is the first report of the presence of the intI2 gene in A. hydrophila isolates in Iran. The blaTEM (40·5%) and tetA (33·3%) genes were found as the predominant ARGs. The most frequently detected VFGs were lip and ahh1(90·5%), while the examined isolates carrying at least three VFGs and the most prevalent VFGs profile was ast+, act+, alt+, ahhl+, aerA+, ahyB+ and lip+. The results of this study indicate a positive association between the presence of VFGs and antibiotic resistance, and most MDR A. hydrophila isolates showed high frequencies of VFGs.

Correlation Between Antimicrobial Resistance, Virulence Determinants and Biofilm Formation Ability Among Extraintestinal Pathogenic Escherichia coli Strains Isolated in Catalonia, Spain.

Escherichia coli is a well-characterized bacterium highly prevalent in the human intestinal tract and the cause of many important infections. The aim of this study was to characterize 376 extraintestinal pathogenic E. coli strains collected from four hospitals in Catalonia (Spain) between 2016 and 2017 in terms of antimicrobial resistance, siderophore production, phylogroup classification, and the presence of selected virulence and antimicrobial resistance genes. In addition, the association between these characteristics and the ability to form biofilms was also analyzed. The strains studied were classified into four groups according to their biofilm formation ability: non-biofilm formers (15.7%), weak (23.1%), moderate (35.6%), and strong biofilm formers (25.6%). The strains were highly resistant to ciprofloxacin (48.7%), trimethoprim-sulfamethoxazole (47.9%), and ampicillin (38%), showing a correlation between higher resistance to ciprofloxacin and lower biofilm production. Seventy-three strains (19.4%) were ESBL-producers. However, no relationship between the presence of ESBL and biofilm formation was found. The virulence factor genes fimH (92%), pgaA (84.6%), and irp1 (77.1%) were the most prevalent in all the studied strains. A statistically significant correlation was found between biofilm formation and the presence of iroN, papA, fimH, sfa, cnf, hlyA, iutA, and colibactin-encoding genes clbA, clbB, clbN, and clbQ. Interestingly, a high prevalence of colibactin-encoding genes (19.9%) was observed. Colibactin is a virulence factor, which interferes with the eukaryotic cell cycle and has been associated with colorectal cancer in humans. Most colibactin-encoding E. coli isolates belonged to phylogroup B2, exhibited low antimicrobial resistance but moderate or high biofilm-forming ability, and were significantly associated with most of the virulence factor genes tested. Additionally, the analysis of their clonal relatedness by PFGE showed 48 different clusters, indicating a high clonal diversity among the colibactin-positive strains. Several studies have correlated the pathogenicity of E. coli and the presence of virulence factor genes; however, colibactin and its relationship to biofilm formation have been scarcely investigated. The increasing prevalence of colibactin in E. coli and other Enterobacteriaceae and the recently described correlation with biofilm formation, makes colibactin a promising therapeutic target to prevent biofilm formation and its associated adverse effects.

Antibiotic Resistance and Virulence Profiles of Klebsiella pneumoniae Strains Isolated From Different Clinical Sources.

Klebsiella pneumoniae is a Gram-negative bacterium capable of colonizing, invading, and causing infections in different anatomical sites of the human body. Its ability to evade the immune system, its increasing antimicrobial resistance and the emergence of hypervirulent pathotypes have become a major challenge in the medical field. In this study, 127 strains from different clinical sources (urine, respiratory tract or blood) were characterized for antimicrobial resistance, the presence of virulence factor genes, serum resistance, hypermucoviscosity and the ability to form biofilms. Specific characteristics of the uropathogenic strains were examined and compared with the other clinical groups. Differences were found between urine and the other groups of strains. Urine strains showed the highest antibiotic resistance (64.91%) compared to blood (63.64%) or respiratory strains (51.35%) as well as the highest extended-spectrum beta-lactamases (ESBL) production. These strains also showed statistically significant high resistance to fosfomycin (24.56%) compared to the other groups (p = 0.008). Regarding virulence, 84.21% of the urine strains presented the uge gene, showing a statistically significant difference (p = 0.03) compared to the other clinical sources, indicating a possible role of this gene in the development of urinary tract infection. In addition, 46% of biofilm-forming strains belonged to the urine sample group (p = 0.043). In conclusion, K. pneumoniae strains isolated from urine samples showed higher antimicrobial resistance, ESBL production, and biofilm-forming ability compared to those isolated from respiratory or blood samples. The rapid spread of clinical strains with these characteristics is of concern, and new therapeutic alternatives are essential to mitigate their harmful effects.

Investigation of antimicrobial susceptibility and virulence factor genes in Trueperella pyogenes isolated from clinical mastitis cases of dairy cows.

Trueperella pyogenes is an opportunistic pathogen causing important diseases including mastitis and metritis in domestic animals such as dairy cows leading to prominent economic losses in food production industry. The aim of this study was to investigate bacterial species, antimicrobial susceptibility, and presence of virulence factor genes and genotyping of T. pyogenes isolates associated with summer mastitis cases from 22 different farms around Tehran, Iran. Fifty‐five percent of dairy cows with clinical mastitis symptoms was infected by T. pyogenesis indicated that this pathogen is the most important contributor to clinical mastitis in dairy cows in the present study. A significant correlation was illustrated between presence of virulence factor genes of isolated pathogen, biochemical patterns, and the utter infected types. Multidrug resistance susceptibility observed between isolates indicated the important need for prudent use of antimicrobials in treatment of mastitis caused by T. pyogenes and increased concerning of consumer health associated with recent problems of antimicrobial resistance. The categorization of isolates was implemented into seven different clonal related types by COX‐PCR at 80% of similarity cutoff with significance relationship to clonal types, CAMP test result and sampling time and biochemical profile. Regarding to the results obtained at the present study, T. pyogenes can be considered as an important typically cause of purulent and acute form of clinical bovine mastitis and loss of dairy productivity. Further studies with more sample size and high‐throughput omic methods in various sampling time and areas are suggested for study of this pathogen precisely.

Antimicrobial resistance and presence of virulence factor genes in Trueperella pyogenes isolated from pig lungs with pneumonia.

Trueperella pyogenes (T. pyogenes) is a worldwide known pathogen of domestic ruminants and pigs causing a wide variety of infections. The objective of this study was to report the presence of major virulence genes in T. pyogenes isolated from pigs with respiratory clinical signs and determine their resistance to antibiotics at the same time. A total of 27 T. pyogenes strains were obtained from Jilin Province, and the nanH, nanP, cbpA, fimC, and fimE virulence genes were detected in 7 (25.9%), 14 (51.9%), 18 (66.7%), 8 (29.6%), and 16 (59.3%) isolates, respectively. All isolates were observed to harbor plo and fimA genes. However, 27 T. pyogenes strains tested negative for fimG gene. Antibiotic susceptibility tests revealed that the isolated strains had extensive drug resistance, all isolates were sensitive to fluoroquinolones and penicillins antibiotics, and high levels of resistance were found to gentamicin (77.8%), amikacin (74.1%), erythromycin (85.2%), and azithromycin (85.2%). These results highlights the need for prudent use of specific antimicrobial agents in veterinary clinical treatment.

Presence of virulence factor genes (gelE and esp) and biofilm formation in clinical Enterococcus faecalis and Enterococcus faecium isolated from urinary tract infection in Isfahan, Iran

BackgroundThe aim of present study was to determine the prevalence of two major virulence genes (gelE and esp) and biofilm-forming ability in Enterococcus faecalis and E. faecium isolated from patients with urinary tract infections (UTIs), and the correlation of selected virulence factors with biofilm formation. MethodsOne hundred Enterococcus isolates were collected from urine of patients with urinary tract infections (UTIs) attending to Alzahra and Gharazi hospitals affiliated to Isfahan University of Medical Sciences. The isolates were confirmed by phenotypic and genotypic methods. Biofilm formation was determined by microtiter plate method and the frequency of gelE and esp genes was evaluated using PCR assay. ResultsOf the 100 confirmed isolates, 83% and 17% were E. faecalis and E. faecium recpectively. The capacity of biofilm formation was 91.5% and 58.7% in E. faecalis and E. faecium respectively. The prevalence of gel E and esp genes was 81.9% and 79.5% in E. faecalis and 76.5% and 58.8% in E. faecium, respectively. There was a significant correlation between biofilm formation and presence of both virulence genes (P < 0.05). ConclusionsIn conclusion, we observed a high frequency of biofilm formation, esp and gelE genes in Enterococcoci strains isolated from UTIs. As an important result was a significant association between the presence of these two genes and biofilm production. Therefore, the new and more effective strategies should be applied to prevent and spread of these strains.

Is staphylococci population from milk of healthy goats safe?

The aim of this study was to assess the species and the genetic diversity of the staphylococci population in raw milk from healthy goats. Isolates representative of all genotypes were screened for their potential pathogenicity by the occurrence of some relevant safety-related properties, such as antibiotic resistance, presence of virulence factor genes, biofilm formation ability and biogenic amine production. A total of 314 staphylococci were isolated, and randomly amplified polymorphic DNA-PCR analysis displayed 48 genotypes. Isolates were identified as belonging to S. epidermidis (87.5%), S. caprae (6.2%), S. aureus (4.2%) and S. simulans (2.1%) species.The antibiotic resistance varied strongly with strains, with S. epidermidis and S. aureus strains showing resistance to more number of antibiotics. A high occurrence of strains harbouring hemolysin genes was also found in both species. On the contrary, none of the strains assayed harboured enterotoxin or amino acid decarboxylase genes, and, although a moderate or high biofilm formation was observed in 29% of the strains, they did not harbour icaA or icaD genes. This study gives a first and extensive picture of safety-related properties within Staphylococcus species isolated from milk of healthy goats, displaying that these species can act as a reservoir for spreading genes related to safety.

Antibiotic resistance and virulence genes of extraintestinal pathogenic Escherichia coli from tropical estuary, South India.

Escherichia coli strains can cause a variety of intestinal and extraintestinal diseases. Extraintestinal pathogenic E. coli (ExPEC) strains have the ability to cause severe extraintestinal infections. Multidrug resistance among ExPEC could complicate human infections. Escherichia coli strains were isolated during the period of January 2010 to December 2012 from five different stations set at Cochin estuary. Susceptibility testing was determined by the disk-diffusion method using nine different antimicrobial agents. A total of 155 strains of Escherichia coli were screened for the presence of virulence factor genes including papAH, papC, sfa/focDE, iutA,and kpsMT II associated with ExPEC. Among the 155 E. coli isolates, 26 (16.77%), carried two or more virulence genes typical of ExPEC. Furthermore, 19.23% of the ExPEC isolates with multidrug resistance were identified to belong to phylogenetic groups B2 and D. Statistically significant association of iutA gene in ExPEC was found with papC (p < 0.001) and kpsMT II (p < 0.001) genes. ExPEC isolates were mainly resistant to ampicillin (23.07%), tetracycline (19.23%), co-trimoxazole (15.38%), and cefotaxime (15.38%). The adhesion genes papAH and sfa/focDE were positively associated with resistance to gentamicin, chloramphenicol, and cefotaxime (p < 0.05). Co-occurrence of virulence factor genes with antibiotic resistance among ExPEC poses considerable threat to those who use this aquatic system for a living and for recreation.

Ribotyping, Antibiotic Resistance Pattern, and Virulence Factors of Vancomycin-Resistant Enterococcus faecium Isolates From UTIs

Aims This study was performed to assess the virulence factors and antibiotic resistance of Enterococcus faecium isolated from urinary tract infection and genetic relatedness of the vancomycin-resistant isolates. Materials and Methods The ribotyping, antibiotic resistance pattern, and the presence of virulence factor genes were examined in the isolated vancomycin-resistant E. faecium. Results Of 759 urine samples, 40 (5.3%) vancomycin-resistant E. faecium were isolated. Seventeen ribotypes were identified among the isolates. The most common ribotype patterns (A-G) constituted approximately 75% of the isolates and they were resistant to 4 antibiotics including ciprofloxacin, erythromycin, ampicillin, and gentamicin. The highest (100%) and lowest (5%) resistance among E. faecium strains isolated from urinary tract infection were found against ampicillin and chloramphenicol, respectively. The results showed that the isolates with certain ribotype, A, B, D, E, and F, always carried esp gene, whereas the other isolates with ribotypes A and B always lacked hyl gene. Conclusions The results may suggest the genetic linkage of hyl and esp genes with certain genotype as determined by ribotyping.

Investigation of virulence factors of Enterococcus faecalis strains isolated in secondary/ persistent infections

Objective: More virulent strains may result from the acquisition of genes by genetic exchange, pathogenicity islands in several species encoding toxins, adhesion factors and other factors associated with virulence. The aim of this study was to investigate the prevalence of E. faecalis strains in secondary endodontic/ persistent using endodontic infection by culture and PCR technqiues; and to investigate for the presence of virulence factor genes of gelatinase (gelE), cytolysin activator (Cyla), surface adhesin of Enterococcus (ESP) and collagen adhesin of Enterococcus (ACE). Material and methods: Microbial samples were obtained from 12 teeth with secondary/ persistent endodontic infection showing apical periodontitis. Culture techniques were used including serial dilution, plating, incubation, and biochemical identification. For PCR detection, samples were analyzed using a species-specific primer of the 16S rDNA and the downstream intergenic spacer region. Results: Culture and PCR detected the test species in 3/12 (25%) and 5/12 (41.6%) of teeth, respectively. A total of 38 Enterococcus faecalis strains were isolated and submitted to the virulence factor genes analysis. PCR products consistent with genes encoding surface adhesion (ESP), gelatinase (gelE) and collagen binding antigen (ACE) were found in 26/38 (68%), 31/38 (81%) and 38/38 (100%) of the isolates. The Cytolysin activator (Cyla) gene was not recovered from E. faecalis isolates. Conclusions: In conclusion, the present study revealed by culture and molecular methods revealed a high prevalence of E. faecalis in teeth with secondary/ persistent endodontic infection. Moreover, of a clinical relevance, we found different E. faecalis strains carrying different virulence determinants.KEYWORDS Bacteria; E. faecalis; Root canal, virulence.

Antimicrobial resistance and presence of virulence factor genes in Arcanobacterium pyogenes isolated from the uterus of postpartum dairy cows

Arcanobacterium pyogenes is considered the most significant bacterium involved in the pathogenesis of metritis in cattle. Infections caused by antimicrobial-resistant bacteria are a great challenge in both human and veterinary medicine. The purpose of this study was to present an overview of antimicrobial resistance in A. pyogenes isolated from the uteruses of postpartum Holstein dairy cows and to identify virulence factors. Seventy-two A. pyogenes isolates were phenotypically characterized for antimicrobial resistance to amoxicillin, ampicillin, ceftiofur, chloramphenicol, florfenicol, oxytetracycline, penicillin, spectinomycin, streptomycin and tetracycline by the broth microdilution method. Presence of virulence factor genes of A. pyogenes was investigated. Isolates exhibited resistance to all antimicrobial agents tested; high levels of resistance were found to amoxicillin (56.9%); ampicillin (86.1%), chloramphenicol (100%), florfenicol (59.7%), oxytetracycline (54.2%), penicillin (86.1%) and tetracycline (50%). Of all isolates, 69 (95.8%) were resistant to at least 2 of the antimicrobial agents tested and multidrug resistance (resistant to at least 3 antimicrobials) was observed in 64 (88.9%) of the A. pyogenes isolates. The major multidrug resistance profile was found for chloramphenicol–ampicillin–penicillin–florfenicol–amoxicillin–tetracycline, which was observed in 21 (29.2%) multidrug resistant isolates. No isolate was resistant to all nine antimicrobial agents tested but four isolates (5.6%) were resistant to eight antimicrobials. The information highlights the need for prudent use of specific antimicrobial agents. All four virulence factor genes occurred in isolates from normal puerperium and clinical metritis; however, the fimA gene was present in significantly higher frequency in isolates from metritis cows.

Virulence factors in vancomycin-resistant and vancomycin- susceptible Enterococcus faecalis from Brazil.

Enterococci are members of commensal flora of animals and insects, but are also important opportunistic pathogens. Our objective was to observe if there was any difference of virulence in several groups of E. faecalis, mainly between vancomycin-resistant E. faecalis (VREFS) of colonization and infection. VREFS and vancomycin-sensitive E. faecalis from Brazil were screened for the presence of virulence factor genes. Phenotypic assays were used to assess in vitro expression, to understand the pathogenic potential of these isolates and to determine whether a correlation exists between virulence and antibiotic resistance. Different virulence profiles were found suggesting that the disseminating clone may have generated several variations. However, our study showed that one constellation of traits appeared most commonly: gelatinase, aggregation substance and esp (GEA). These factors are important because they have been implicated in cell aggregation and biofilm formation. Biofilm formation may promote the conjugation of plasmids harboring resistance and virulence genes, enhancing the probability of entry of new resistance genes into species. Curiously, the profile GEA was not exclusive to VREFS, it was the second most observed in VSEFS isolates from colonization and infection in hospitalized patients and also from rectal swabs of healthy volunteers. Such strains appear to represent the entry gateway to new resistance genes into E. faecalis and may contribute to the spreading of E. faecalis mainly in hospitals.

Survey for virulence determinants among Enterococcus faecalis isolated from different sources.

A collection of Enterococcus faecalis strains from clinical isolates, healthy individuals and the environment was screened for the presence of virulence factor genes, such as those for collagen-binding protein (ace), endocarditis antigen (efaA), haemolysin activator (cylA), gelatinase (gelE), aggregation substances (asa1 and asa373), a surface protein (esp) and two novel putative surface antigens (EF0591 and EF3314). Apart from some genes that were present in all strains (ace, efaA and EF3314), the gelE gene was the most common factor, although its presence did not correlate with its expression. The genes that encode Esp and CylA were never detected in endocarditis isolates, whereas an association was noted between the esp gene and isolates from urinary tract infection (UTI) and bacteraemia. An aggregation substance gene was always present in commensal strains. As for gelatinase, the presence of the cylA and asa genes did not correlate completely with their phenotypic expression. Generally, isolates from endocarditis, biliary stents and the environment were equipped with fewer virulence factors than isolates from other sources. UTI strains possessed the highest number of factors.