Pathogenesis of implant infections by enterococci

Antibiogram Pattern and Virulence Trait Characterization of Enterococcus Species Clinical Isolates in Eastern India: A Recent Analysis

Objective We aimed to evaluate the current antimicrobial susceptibility pattern and characterize putative virulence traits among Enterococcus species isolates from various clinical specimens in view of their increased isolation rates in both community-related and serious nosocomial infections, as well as resistance to many antibiotics.

Methods Study (April 2017–March 2018) included consecutive, nonrepeated, discrete, and clinically significant isolates of enterococci. Susceptibility testing included detection of high-level aminoglycoside-resistant (HLAR) and glycopeptide-resistant enterococci (GRE). All screen-positive GRE isolates were investigated by polymerase chain reaction for species confirmation and presence of vanA/vanB genes. Virulence genes ace, asa1, cyt, efa, esp, gelE, and hyl were investigated by molecular methods. Hemolysin and biofilm production were studied using phenotypic methods.

Results Of 111 isolates, 89 (80.1%), 16 (14.4%), and 6 (5.4%) were from urine, pus, and blood, respectively, consisting predominantly of E. faecalis (67, 60.4%) and E. faecium (32, 28.8%). E. hirae (5, 4.5%) was the predominant non-E. faecalis non-E. faecium isolate. Other species were E. durans (4, 3.6%), E. avium (2, 1.8%), and E. mundtii (1, 0.9%). Seven (6.3%) out of the 111 isolates were GRE, all vanA genotype. HLAR was observed in 70 (63.1%) isolates, significantly higher in E. faecium than E. faecalis (81.2 vs. 58.2%; p < 0.05). All were susceptible to daptomycin. Hemolysin activity and biofilm production were observed in 38 (34.2%) and 36 (32.4%) isolates. Most frequent virulence genes were efa (77, 69.4%), ace (71, 63.9%), asa1 (67, 60.3%), and gelE (66, 59.4%). There was a predominant association of esp and hyl genes with E. faecium and that of the other genes with E. faecalis.

Conclusion The study will contribute to the existing limited data on virulence trait characterization of clinical E. spp. isolates in India. At the same time, it will help to serve as a guide in the choice of empirical therapy in enterococcal infections leading to favorable clinical outcomes by decreasing the clinical failure, microbiological persistence, and associated mortality, and will lead to future studies on controlling the spread of virulent and multiresistant isolates.

Surgical site infection at chest tube drainage site following pulmonary resection for malignant lesions

Background

We sometimes experience postoperative surgical site infection (SSI) at the chest tube drainage site (CDS) after thoracotomy. The incidence of and risk factors for SSI at the CDS have remained unclear.

Methods

We conducted a prospective study to determine the incidence and risk factors for SSI at the CDS. We analyzed 99 patients who underwent lobectomy or segmentectomy for pulmonary malignant lesions.

Results

There were 56 males and 43 females with an average age of 71 years. The postoperative drainage period was 2–15 days. Bacterial species were detected in secretions in 18 of 99 cases (18.2%). Older age was a risk factor for the detection of bacteria at the timing of chest tube removal. Eighteen cases (18.2%) were diagnosed with presence of SSI at the CDS at the timing of staple or suture removal. A pathological diagnosis of squamous cell carcinoma was regarded as a candidate risk factor for SSI. Eleven of 18 SSI patients showed delayed wound healing. A higher level of HbA1c was found in patients with delayed wound healing. Enterococcus faecalis infection may influence the development of complex SSI.

Conclusions

We identified the bacterial profiles, incidence of and risk factors for SSI at the CDS. More intense preoperative glycemic control and an understanding of the bacterial profile and may be useful for reducing the incidence of SSI chest tube drainage sites (CDS).

Purification and characterization of bacteriocins-like inhibitory substances from food isolated Enterococcus faecalis OS13 with activity against nosocomial enterococci

Nosocomial infections caused by enterococci are an ongoing global threat. Thus, finding therapeutic agents for the treatment of such infections are crucial. Some Enterococcus faecalis strains are able to produce antimicrobial peptides called bacteriocins. We analyzed 65 E. faecalis isolates from 43 food samples and 22 clinical samples in Egypt for 17 common bacteriocin-encoding genes of Enterococcus spp. These genes were absent in 11 isolates that showed antimicrobial activity putatively due to bacteriocins (three from food, including isolate OS13, and eight from clinical isolates). The food-isolated E. faecalis OS13 produced bacteriocin-like inhibitory substances (BLIS) named enterocin OS13, which comprised two peptides (enterocin OS13α OS13β) that inhibited the growth of antibiotic-resistant nosocomial E. faecalis and E. faecium isolates. The molecular weights of enterocin OS13α and OS13β were determined as 8079 Da and 7859 Da, respectively, and both were heat-labile. Enterocin OS13α was sensitive to proteinase K, while enterocin OS13β was resistant. Characterization of E. faecalis OS13 isolate revealed that it belonged to sequence type 116. It was non-hemolytic, bile salt hydrolase-negative, gelatinase-positive, and sensitive to ampicillin, penicillin, vancomycin, erythromycin, kanamycin, and gentamicin. In conclusion, BLIS as enterocin OS13α and OS13β represent antimicrobial agents with activities against antibiotic-resistant enterococcal isolates.

Matrix metalloprotease-1 inhibits and disrupts Enterococcus faecalis biofilms

Enterococcus faecalis is a major opportunistic pathogen that readily forms protective biofilms leading to chronic infections. Biofilms protect bacteria from detergent solutions, antimicrobial agents, environmental stress, and effectively make bacteria 10 to 1000-fold more resistant to antibiotic treatment. Extracellular proteins and polysaccharides are primary components of biofilms and play a key role in cell survival, microbial persistence, cellular interaction, and maturation of E. faecalis biofilms. Degradation of biofilm components by mammalian proteases is an effective antibiofilm strategy because proteases are known to degrade bacterial proteins leading to bacterial cell lysis and growth inhibition. Here, we show that human matrix metalloprotease-1 inhibits and disrupts E. faecalis biofilms. MMPs are cell-secreted zinc- and calcium-dependent proteases that degrade and regulate various structural components of the extracellular matrix. Human MMP1 is known to degrade type-1 collagen and can also cleave a wide range of substrates. We found that recombinant human MMP1 significantly inhibited and disrupted biofilms of vancomycin sensitive and vancomycin resistant E. faecalis strains. The mechanism of antibiofilm activity is speculated to be linked with bacterial growth inhibition and degradation of biofilm matrix proteins by MMP1. These findings suggest that human MMP1 can potentially be used as a potent antibiofilm agent against E. faecalis biofilms.

Prevalence and antimicrobial susceptibility pattern of Enterococcus species isolated from different clinical samples at Black Lion Specialized Teaching Hospital, Addis Ababa, Ethiopia

OBJECTIVE

Enterococci which are parts of the normal intestinal flora are opportunistic human pathogens. Their increasing importance is largely due to their resistance to antimicrobials. So the aim this study was to determine the prevalence and antimicrobial pattern of Enterococcus spp.

RESULT

From the total of 422 samples processed, 15 Enterococcus species were isolated. In this study, linezolid were the drug of choice for Enterococcus species, which showed 100% sensitive followed by vancomycin 93.3% sensitive. In contrast, highly resistance (80%) was observed for ampicillin followed by doxycycline (73.3%). All of isolated Enterococci were sensitive to linezolid, however, resistance was observed to common antibiotics. The presence of multidrug resistant Enterococci in our study should be considered as an alarm for Enterococcal infections.

The Alpha-Like Surface Proteins: An Example of an Expanding Family of Adhesins

The Alpha-like protein (Alp) family, repeat-containing surface proteins once thought to be important adhesion factors confined to pathogenic streptococci and enterococci, is broader than previously known. Analysis of the annotated microbial genomes has identified new potential members of the Alp family not only in other Gram- positive opportunistic pathogens but also in commensal microflora of the human gut and the skin. This finding has highlighted the importance of genome sequencing projects for unraveling in greater detail lateral gene transfer events involving virulence factors between pathogens and commensals. These should receive constant attention not only as part of infectious disease prevention programs, but also in the food and biotechnology industries. (Int J Artif Organs 2008; 31: 834–40)

Combating Implant Infections. Remarks by a Women's Team

Research on implant infections requires cooperative efforts and integration between basic and clinical expertises. An international group of women scientists is acting together in this field. The main research topics of the participants of this group are described. Formation of bacterial biofilms, antibiotic resistance and production of virulence factors like adhesins and toxins are investigated. New biomaterials, coatings and drugs designed to inhibit microbial adhesion are evaluated, and infection-resistant biomaterials are under study, such as a novel heparinizable polycarbonate-urethane (Bionate) or incorporation of diamino-diamide-diol (PIME) to reduce bacterial attachment. The correlation between biofilm production and the accessory-gene-regulator (agr) is investigated in Staphylococcus aureus. The ability to form biofilm has also been shown to be one of the important virulence factors of Enterococcus faecalis, favouring colonization of inert and biological surfaces. The study of quorum sensing has led to the discovery of a quorum sensing inhibitor termed RIP that suppresses staphylococcal biofilm and infections. The immune response and the local defence mechanisms of the host against implant-associated infections, activation and infiltration of immunocompetent cells into the sites of infection have been studied in patients with implant-associated osteomyelitis. Production of monoclonal antibodies (mAbs) as possible vaccines against the staphylococcal collagen-binding MSCRAMMs is in progress. (Int J Artif Organs 2008; 31: 858–64)

Underestimated Collateral Effects of Antibiotic Therapy in Prosthesis-Associated Bacterial Infections

Antibiotic treatment of infections associated with the use of indwelling medical devices in ageing and/or severely ill patients represents a significant healthcare problem due to the difficulty of treating such infections and to the various collateral effects that may be observed following the often aggressive therapy We summarize some effects of antibiotics on the expression of virulence factors of the microorganisms which cause such infections. These effects, particularly those resulting in a stimulation of bacterial virulence, might be usefully included among the other well-known collateral effects of antibiotic therapy

A novel bacteriocin from Enterococcus faecalis 478 exhibits a potent activity against vancomycin-resistant enterococci

The emergence of multidrug-resistant enterococci (MDRE) and particularly vancomycin-resistant enterococci (VRE) is considered a serious health problem worldwide, causing the need for new antimicrobials. The aim of this study was to discover and characterize bacteriocin against clinical isolates of MDRE and VRE. Over 10,000 bacterial isolates from water, environment and clinical samples were screened. E. faecalis strain 478 isolated from human feces produced the highest antibacterial activity against several MDRE and VRE strains. The optimum condition for bacteriocin production was cultivation in MRS broth at 37°C, pH 5-6 for 16 hours. The bacteriocin-like substance produced from E. faecalis strain EF478 was stable at 60°C for at least 1 hour and retained its antimicrobial activity after storage at -20°C for 1 year, at 4°C for 6 months, and at 25°C for 2 months. A nano-HPLC electrospray ionization multi-stage tandem mass spectrometry (nLC-ESI-MS/MS) analysis showed that the amino acid sequences of the bacteriocin-like substance was similar to serine protease of E. faecalis, gi|488296663 (NCBI database), which has never been reported as a bacteriocin. This study reported a novel bacteriocin with high antibacterial activity against VRE and MDRE.

Virulence factors, antimicrobial resistance pattern and molecular analysis of Enterococcal strains isolated from burn patients

The enterococci are emerging as a significant cause of hospital acquired infections. The pathogenesis of enterococci is attributed to the production of virulence factors and resistance to antibiotics. The purpose of the study was to assess the prevalence of genes encoding virulence factor, antimicrobial resistance determinant and molecular characteristic of enterococci isolated from burn patients. A total of 57 enterococci isolated from wound specimens of patients with burn injury were characterized by phenotypic and genotypic methods. The efaA was the most frequently detected gene (100%), followed by ace (89.1%), asa1 (54.3%), gelE (50%), cylA (30.4%), esp (23.9%) and hyl (8.7%) among Enterococcus faecalis isolates. The Enterococcus faecium strains carried asa1 and ace genes. All isolates were susceptible to tigecycline and vancomycin. Inducible resistance to clindamycin was not observed and 64% of isolates had resistance to erythromycin. High-level gentamicin resistance (HLGR) was seen in 65.2% of E. faecalis strains. The aac(6')-Ie-aph(2″)-Ia gene was found in 47.8% of E. faecalis isolates. Our data indicated that the efaA, ace and asa1 were most frequent genes encoding virulence factors among Enterococci isolated from burn wound infection and the incidence of virulence factor genes was higher in E. faecalis rather than other isolates. The molecular analysis demonstrated high genetic diversity among Enterococcus populations from burn patients.

Antimicrobial effect of Lippia sidoides and thymol on Enterococcus faecalis biofilm of the bacterium isolated from root canals

The species Lippia sidoides Cham. (Verbenaceae) is utilized in popular medicine as a local antiseptic on the skin and mucosal tissues. Enterococcus faecalis is the bacterium isolated from root canals of teeth with persistent periapical lesions and has the ability to form biofilm, where it is responsible for the failure of endodontic treatments. Essential oil of L. sidoides (EOLS) and its major component, thymol, were evaluated for reducing the CFU in biofilms of E. faecalis in vitro. The essential oil was obtained by hydrodistillation and examined with respect to the chemical composition, by gas chromatography-mass spectrometry (GC-MS). The GC-MS analysis has led to the identification of thymol (84.9%) and p-cymene (5.33%). EOLS and thymol reduced CFU in biofilms of E. faecalis in vitro (time of maturation, 72 h), with an exposure time of 30 and 60 min at concentrations of 2.5 and 10%. There was no statistical difference in effect between EOLS and thymol, demonstrating that this phenolic monoterpene was the possible compound responsible for the antimicrobial activity of EOLS. This study provides a basis for the possible utilization of EOLS as an adjuvant in the treatment of root canals that show colonization by E. faecalis.

Efficacy of tigecycline and rifampin alone and in combination against Enterococcus faecalis biofilm infection in a rat model of ureteral stent

BACKGROUND

We investigated the efficacy of tigecycline and rifampin alone or combined in preventing ureteral stent infection due to Enterococcus faecalis.

MATERIALS AND METHODS

The activities of the two antibiotics were previously studied in vitro in absence or in presence of biofilm. For in vivo research, the study included a control group without bacterial challenge to evaluate the sterility of surgical procedure, a challenged control group that did not receive any antibiotic prophylaxis and, for each bacterial strain, three challenged groups that received: (1) 2 mg/kg intraperitoneal tigecycline, immediately after stent implantation; (2) rifampin-coated ureteral stents where 0.2 cm(2) sterile ureteral stents were incubated in 10 mg/L rifampin solution for 30 min immediately before implantation; and (3) intraperitoneal tigecycline plus rifampin-coated ureteral stent at the above concentrations. Ureteral stents were explanted at d 5 following implantation and biofilm bacteria enumerated.

RESULTS

The in vitro studies showed that the biofilm was strongly affected by the presence of rifampin and, in its presence, tigecycline had MICs and MBCs lower than those obtained in the absence of rifampin. Intraperitoneal tigecycline exerted stronger effect than rifampin on bacterial numbers. The combination rifampin plus tigecycline showed efficacies higher than that of each single compound.

CONCLUSION

These results highlight the potential usefulness of tigecycline in preventing enterococcal ureteral stent infections and the role of rifampin as an interesting antibiotic enhancer.

Abdominal pseudocysts following peritoneal dialysis-associated peritonitis: a report of 3 cases

Common complications of peritoneal dialysis are peritonitis, leakages, hernias, catheter dislocation, and loss of ultrafiltration. We describe 3 cases of abdominal pseudocysts with progressive difficulty instilling and draining peritoneal dialysis fluid. The 3 patients had been treated with peritoneal dialysis for 1, 2, and 6 years. Two patients had experienced previous episodes of peritonitis and 1 had signs of peritonitis when the pseudocyst was first detected. In all 3 patients, ultrasound and computed tomographic scans, obtained because of progressive decreases in solute clearance, showed dialysate entrapped in a cyst that enclosed the inner tip of the Tenckhoff catheter. The cyst was resected in 2 patients, and the Tenckhoff catheter was removed in 1 patient. Histologic samples were not suggestive of encapsulating peritoneal sclerosis. Abdominal pseudocysts are a rare complication after peritoneal dialysis therapy, but are reported in 1% of patients with ventriculoperitoneal shunts. The outcome of our described patients was good, although they had to be switched to hemodialysis therapy.

Surface protein EF3314 contributes to virulence properties of Enterococcus faecalis

PURPOSE

Identification of putative new virulence factors as additional targets for therapeutic approaches alternative to antibiotic treatment of multi-resistant enterococcal infections.

METHODS

The EF3314 gene, coding for a putative surface-exposed antigen, was identified by the analysis of the Enterococcus faecalis V583 genome for LPXTG-motif cell wall anchor surface protein genes. A non-polar EF3314 gene deletion mutant in the E. faecalis 12030 human clinical isolate was obtained. The wild type and the isogenic mutant strain were investigated for biofilm formation, adherence to Hela cells, survival in human macrophages and a Caenorhabditis elegans infection model. The aminoterminal portion of the EF3314 protein was overexpressed in E. coli to obtain mouse polyclonal antibodies for use in Western blotting and immunolocalization experiments.

RESULTS

The EF3314 gene has an unusually high GC content (46.88% vs. an average of 37.5% in the E. faecalis chromosome) and encodes a protein of 1744 amino acids that presents a series of 14 imperfect repeats of 90 amino acids covering almost the entire length of the protein. Its global organization is similar to the alpha-like protein family of group B streptococci, enterococcal surface protein Esp and biofilm associated protein Bap from S. aureus. The EF3314 gene was always present and specific for E. faecalis strains of human, food and animal origin. Differences in size depended on variable numbers of repeats in the repetitive region.

CONCLUSIONS

EF3314 is a newly described, surface exposed protein that contributes to the virulence properties of E. faecalis.

Extracellular gelatinase of Enterococcus faecalis destroys a defense system in insect hemolymph and human serum

We isolated Enterococcus faecalis from the body fluids of dead larvae of the greater wax moth, Galleria mellonella. Extracellular gelatinase (GelE) and serine protease (SprE), both of which are considered putative virulence factors of E. faecalis, were purified from the culture supernatant of E. faecalis. In an attempt to elucidate their virulence mechanisms, purified GelE and SprE were injected into hemolymph of G. mellonella and evaluated with regard to their effects on the immune system of insect hemolymph. As a result, it was determined that E. faecalis GelE degraded an inducible antimicrobial peptide (Gm cecropin) which is known to perform a critical role in host defense during the early phase of microbial infection. The results obtained from the G. mellonella-E. faecalis infection model compelled us to assess the virulence activity of GelE against the complement system in human serum. E. faecalis GelE hydrolyzed C3a and also mediated the degradation of the alpha chain of C3b, thereby inhibiting opsonization and the formation of the membrane attack complex resultant from the activation of the complement cascade triggered by C3 activation. In contrast, E. faecalis SprE exhibited no virulence effect against the immune system of insect hemolymph or human serum tested in this study.

Virulence factors in enterococcal infections of orthopedic devices

Enterococci are opportunistic pathogens which today represent one of the leading causes of nosocomial infections. We have examined a collection of 52 Enterococcus faecalis isolated from orthopedic infections to determine if they were characterized by a specific pattern of virulence factors. The isolates were evaluated for biofilm formation, presence of genes coding the enterococcal surface protein (esp) and gelatinase (gelE), as well as for gelatinase production. While the rate of esp-positive isolates was comparable to that found among strains from other clinical sources, we found a significantly higher rate of strong biofilm formers and gelatinase producers. Particularly high was the rate of gelE-carrying strains expressing the gene. Data suggest that these two factors in particular may play an important role in enterococcal infections associated with biomaterials.

Cervical infection with descending mediastinitis: a review of six cases

The aim of this study was to retrospectively review cases of cervical infection with descending mediastinitis, and to analyse the clinical character, diagnosis and treatment of this infection. Six patients were identified from December 1998 to June 2005. Their aetiology, associated systemic diseases, bacteriology, radiology, treatments and outcomes were reviewed. Four cases resulted from odontogenic infection, one from upper airway infection, and one had an unknown cause. Diffuse swelling in face and neck, chest distress, tachypnea, and fever were the main symptoms. Chest radiography showed a widening of the upper mediastinal shadow in four patients. Four patients underwent computed tomographic scanning that confirmed the diagnosis of descending mediastinitis, which suggests that routine use of this scan be highly recommended for early detection. Six different pathogens were identified through pus and blood culture. All patients underwent surgical drainage. Three patients received a tracheotomy. Of the six patients, four achieved good results, and there were two deaths. Early surgical drainage remains the main treatment for cervical infection with descending mediastinitis. Delayed diagnosis, inadequate drainage and multidrug-resistant bacterial infection were responsible for the deaths.