Nosocomial enterococcal blood stream infections in the SCOPE Program: antimicrobial resistance, species occurrence, molecular testing results, and laboratory testing accuracy. SCOPE Hospital Study Group

Identification of potential inhibitors against Corynebacterium diphtheriae MtrA response regulator protein; an in-silico drug discovery approach

Corynebacterium diphtheriae is a multi-drug resistant bacteria responsible for the life-threatening respiratory illness, diphtheria which can lead to severe Nervous system disorders, mainly infecting the lungs, heart, and kidneys if left untreated. In the current study, Corynebacterium diphtheriae MtrA response regulator protein was targeted, which regulates a two-component system of bacterial pathogenesis, and initiates DNA replication and cell division. In the current study a computational approach have been described for drug development against C. diphtheriae infections by inhibiting MtrA protein by small molecules acting as potential inhibitors against it. Molecular docking analysis of the equilibrated MtrA protein revealed compound-0.2970, compound-0.3029, and compound-0.3016 from Asinex Library as the promising inhibitors based on their lowest binding energies (-9.8 kJ/mol, -9.2 kJ/mol, and -8.9 kJ/mol), highest gold scores (40.53, 47.41, and 48.41), drug-likeness and pharmacokinetic properties. The MD simulation studies of the identified top-ranked inhibitors at 100 ns elucidated the system stability and fluctuations in the binding pocket of MtrA protein. Molecular Dynamics Simulations of the top three docked complexes further revealed that the standard binding pocket was retained ensuring the system stability. The rearrangements of H-bonds, van der Waals, pi-pi, and solid hydrophobic interactions were also observed. The binding free energy calculations (MM/PBSA and MM/GBSA) suggested a fundamental binding capability of the ligand to the target receptor MtrA. Therefore, the current study has provided excellent candidates acting as potent inhibitors for developing therapeutic drugs against C. diphtheriae infections. However, in vivo and in vitro animal experiments and accurate clinical trials are needed to validate the potential inhibitory effect of these compounds.

Antibiotic choices among healthcare professionals for enterococcal bacteremia with patterns of resistance and risk factors of mortality, in settings of poor antibiotic stewardship program - a five-year retrospective cohort study

BACKGROUND

Enterococcal bacteremia has become prevalent in the recent decade, especially in hospitalized patients. Moreover, the rise in resistance patterns against antibiotic drugs regarding enterococci infection, such as cephalosporins, ampicillin and vancomycin, is prevailing. The major driving force behind this is the incongruous use of antibiotics with a minor contribution from environmental stressors which calls for vigilant and prudent administration of evidence-based antibiotics.

METHODS

A retrospective study was conducted from January 1 2017 until December 31 2021, at the tertiary care center, Dr Ziauddin Hospital in Karachi, Pakistan.

RESULTS

Our research revealed ampicillin resistance in 87 (63.5%), with an estimated 25 (18.8%) mortality. Male gender 19 (76%) and vancomycin resistance 13 (52%) were associated with increased mortality. Furthermore, appropriate antibiotic therapy reduced the risk of death compared with inappropriate and excessive use of antibiotics 10 (40%) vs. 15 (60%) vs. 20 (80%) respectively. Targeted therapy with amoxicillin/clavulanic acid was associated with lower mortality 1 (4%) and higher discharge rates 34 (32.1%). On Kaplan-Meier survival, targeted therapy with amoxicillin/clavulanic acid was associated with shorter hospital stays and prolonged survival. UTI was found as the most common source of enterococcal bacteremia 57 (41.6%), followed by respiratory 21 (15.3%) and intra-abdominal 13 (9.5%). In 26 (19%) patients, no identifiable source of infection was found.

CONCLUSION

Vancomycin resistance and male gender were found independent risk factors for mortality. The use of inappropriate antibiotics significantly increases mortality in these patients. The appropriate antibiotic therapy reduces the risk of death. Furthermore, overuse of antibiotics didn't reduce mortality; instead increased the financial burden and chances of developing multi-drug resistant strains of other organisms by increasing hospital stays of patients.

Comparative Evaluation of Intracanal Smear Layer Removal by Different Root Canal Irrigants: A Scanning Electron Microscope Study

Aim

The purpose of the study is to compare and evaluate the efficacy of different root canal irrigants-100, 75, 50, and 25% neem extract, 100, 75, 50, and 25% apple cider vinegar (ACV), a combination of 5.25% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA), and saline on smear layer removal using a scanning electron microscope (SEM).

Materials and methods

A total of 80 freshly extracted single-rooted teeth were collected and divided into 10 groups-group I: normal saline (negative control), group II: NaOCl with EDTA (positive control), group III: 100% neem extract, group IV: 75% neem extract, group V: 50% neem extract, group VI: 25% neem extract, group VII: 100% ACV, group VIII: 75% ACV, group IX: 50% ACV, and group X: 25% ACV. The samples were irrigated with a specific group of irrigants, then split in a longitudinal axis and processed for analysis in an SEM. Microphotographs were obtained and scored according to Torabinejad et al.

Results

Microphotographs were assessed and showed that 100% neem extract was similar to NaOCl with EDTA, followed by 75% neem extract and 100% ACV.

Conclusion

This study showed that 100% neem extract removed the smear layer, similar to the NaOCl with EDTA.

How to cite this article

Sudhakar S, Gupta N, Ghambir N, et al. Comparative Evaluation of Intracanal Smear Layer Removal by Different Root Canal Irrigants: A Scanning Electron Microscope Study. Int J Clin Pediatr Dent 2023;16(4):633-638.

Application of Next-Generation Sequencing for Characterization of Surveillance and Clinical Trial Isolates: Analysis of the Distribution of β-lactamase Resistance Genes and Lineage Background in the United States

Background

Sequencing technologies and techniques have seen remarkable transformation and innovation that have significantly affected sequencing capability. Data analyses have replaced sequencing as the main challenge. This paper provides an overview on applying next-generation sequencing (NGS) and analysis and discusses the benefits and challenges. In addition, this document shows results from using NGS and bioinformatics tools to screen for β-lactamase genes and assess the epidemiological structure of Escherichia coli– and Klebsiella pneumoniae–causing bloodstream (BSIs) and urinary tract (UTIs) infections in patients hospitalized in the United States during the SENTRY Antimicrobial Surveillance Program for 2016.

Methods

A total of 3525 isolates (2751 E. coli and 774 K. pneumoniae) causing BSIs (n = 892) and UTIs (n = 2633) in hospitalized patients in the United States were included. Isolates were tested for susceptibility by broth microdilution, and those that met a minimum inhibitory concentration (MIC)–based screening criteria had their genomes sequenced and analyzed.

Results

A total of 11.6% and 16.1% of E. coli–causing UTIs and BSIs, respectively, met the MIC-based criteria, whereas 11.0% and 13.7% of K. pneumoniae isolates causing UTIs and BSIs, respectively, met the criteria. Among E. coli, bla_CTX-M variants (87.6% overall) prevailed (60.5% of CTX-M group 1 and 26.9% of group 9). A total of 60.3% of K. pneumoniae isolates carried bla_CTX-M variants (52.7% and 7.6% of groups 1 and 9, respectively). Two E. coli (0.6%) and 13 K. pneumoniae (12.9%) isolates harbored bla_KPC. Among KPC-producing K. pneumoniae (2 from BSIs and 11 from UTIs), 84.6% (11/13) were ST258 (CC258). Seventeen and 38 unique clonal complexes (CCs) were noted in E. coli that caused BSIs and UTIs, respectively, and CC131 (or ST131) was the most common CC among BSI (53.6%) and UTI (58.2%) isolates. Twenty-three and 26 CCs were noted among K. pneumoniae–causing BSIs and UTIs, respectively. CC258 (28.3%) prevailed in UTI pathogens, whereas CC307 (15.0%) was the most common CC among BSI isolates.

Conclusions

This study provides a benchmark for the distribution of β-lactamase genes and the population structure information for the most common Enterobacteriaceae species responsible for BSIs and UTIs in US medical centers during the 2016 SENTRY Program.

Temporal and Geographic Variation in Antimicrobial Susceptibility and Resistance Patterns of Enterococci: Results From the SENTRY Antimicrobial Surveillance Program, 1997-2016

Background

The SENTRY Antimicrobial Surveillance Program was established in 1997 and presently encompasses more than 750 000 bacterial isolates from over 400 medical centers worldwide. Among these pathogens, enterococci represents a prominent cause of bloodstream (BSIs), intra-abdominal (IAIs), skin and skin structure, and urinary tract infections (UTIs). In the present study, we reviewed geographic and temporal trends in Enterococcus species and resistant phenotypes identified throughout the SENTRY Program.

Methods

From 1997 to 2016, a total of 49 491 clinically significant enterococci isolates (15 species) were submitted from 298 medical centers representing the Asia-Pacific (APAC), European, Latin American (LATAM), and North American (NA) regions. Bacteria were identified by standard algorithms and matrix-assisted laser desorption ionization–time of flight mass spectrometry. Susceptibility (S) testing was performed by reference broth microdilution methods and interpreted using Clinical and Laboratory Standards Institute/US Food and Drug Administration and European Committee on Antimicrobial Susceptibility Testing criteria.

Results

The most common Enterococcus species in all 4 regions were Enterococcus faecalis (64.7%) and E. faecium (EFM; 29.0%). Enterococci accounted for 10.7% of BSIs in NA and was most prominent as a cause of IAIs (24.0%) in APAC and of UTIs (19.8%) in LATAM. A steady decrease in the susceptibility to ampicillin and vancomycin was observed in all regions over the 20-year interval. Vancomycin-resistant enterococci (VRE) accounted for more than 8% of enterococcal isolates in all regions and was most common in NA (21.6%). Among the 7615 VRE isolates detected, 89.1% were the VanA phenotype (91.0% EFM) and 10.9% were VanB. Several newer antimicrobial agents demonstrated promising activity against VRE, including daptomycin (99.6–100.0% S), linezolid (98.0%–99.6% S), oritavancin (92.2%–98.3% S), tedizolid (99.5%–100.0% S), and tigecycline (99.4%–100.0% S).

Conclusions

Enterococci remained a prominent gram-positive pathogen in the SENTRY Program from 1997 through 2016. The overall frequency of VRE was 15.4% and increased over time in all monitored regions. Newly released agents with novel mechanisms of action show promising activity against VRE.

Incidence, clinical characteristics, and outcomes of nosocomial Enterococcus spp. bloodstream infections in a tertiary-care hospital in Beijing, China: a four-year retrospective study

Background

Enterococcus spp. are the common cause of nosocomial bloodstream infections (BSIs) with high morbidity and mortality. The purpose of this study was to characterize the incidence, clinical and microbiological features, and mortality of nosocomial enterococcal BSIs at a large Chinese tertiary-care hospital in Beijing, China.

Methods

A retrospective cohort study on adult patients with nosocomial BSIs due to Enterococcus spp. was performed between January 1, 2012, and December 31, 2015 at the Chinese People’s Liberation Army General Hospital. Patients’ data were gathered by reviewing electronic medical records.

Results

A total of 233 episodes of BSI due to Enterococcus spp. occurred among 224 patients during these 4 years. The overall incidence was 3.9 episodes per 10,000 admissions. Enterococcus faecium (E. faecium) was the major pathogen (74%, 95% CI 68–80%), followed by Enterococcus faecalis (E. faecalis) (20%, 95% CI 15–25%). E. faecium showed higher antimicrobial resistance than E. faecalis. The 30-day mortality of nosocomial enterococcal BSI was 24% (95% CI 18–29%). Predictors for mortality included the Acute Physiology and Chronic Health Evaluation II (APACHE II) score, Charlson comorbidity index (CCI), impaired renal function, prior use of immunosuppressive agents, and appropriate empirical antimicrobial treatment.

Conclusions

This study emphasizes that Enterococcus spp. were major pathogens for nosocomial BSIs and associated with high mortality. Appropriate empirical antimicrobial treatment can improve outcomes. Vancomycin is the best choice for patients with E. faecium BSIs. Penicillins, aminoglycosides, fluoroquinolones, and vancomycin can be considered for patients with E. faecalis BSIs.

High rates of multidrug resistance in Enterococcus faecalis and E. faecium isolated from inpatients and outpatients in Taiwan

Longitudinal national data on resistance in Enterococcus faecalis and E. faecium from different sources in Taiwan are rare. The present study analyzed data from the Taiwan Surveillance of Antimicrobial Resistance program to address this issue. Between 2002 and 2010, a total of 1696 E. faecalis and 452 E. faecium isolates were studied. Although these 2 species together comprised similar percentages of all enterococci in each study year (94.1-97.2%, P = 0.19), the proportion of E. faecium increased from 12.4% in 2002 to 27.3% in 2010 (P < 0.001). The most noteworthy change in susceptibilities of these 2 species was vancomycin resistance in E. faecium (VREfm), which increased from 0.3% in 2004 to 24.9% in 2010 (P < 0.001). VREfm prevalence differed significantly between geographic regions, patient age groups, and locations. Multidrug resistance was very common in both species even in isolates from outpatients (82.7% for E. faecalis and 98.1% for E. faecium), at rates similar to those from intensive care unit (ICU) and non-ICU patients (80.5-80.9% in E. faecalis and 97.2-98.6% in E. faecium). Nonsusceptibility to linezolid was <0.5% in both species. All tested isolates were susceptible to daptomycin. Continuous surveillance of VRE prevalence and survey of community reservoirs of multidrug-resistant enterococci are warranted.

A novel method for simultaneous Enterococcus species identification/typing and van genotyping by high resolution melt analysis

In order to develop a typing and identification method for van gene containing Enterococcus faecium, two multiplex PCR reactions were developed for use in HRM-PCR (High Resolution Melt-PCR): (i) vanA, vanB, vanC, vanC23 to detect van genes from different Enterococcus species; (ii) ISR (intergenic spacer region between the 16S and 23S rRNA genes) to detect all Enterococcus species and obtain species and isolate specific HRM curves. To test and validate the method three groups of isolates were tested: (i) 1672 Enterococcus species isolates from January 2009 to December 2009; (ii) 71 isolates previously identified and typed by PFGE (pulsed-field gel electrophoresis) and MLST (multi-locus sequence typing); and (iii) 18 of the isolates from (i) for which ISR sequencing was done. As well as successfully identifying 2 common genotypes by HRM from the Austin Hospital clinical isolates, this study analysed the sequences of all the vanB genes deposited in GenBank and developed a numerical classification scheme for the standardised naming of these vanB genotypes. The identification of Enterococcus faecalis from E. faecium was reliable and stable using ISR PCR. The typing of E. faecium by ISR PCR: (i) detected two variable peaks corresponding to different copy numbers of insertion sequences I and II corresponding to peak I and II respectively; (ii) produced 7 melt profiles for E. faecium with variable copy numbers of sequences I and II; (iii) demonstrated stability and instability of peak heights with equal frequency within the patient sample (36.4±4.5 days and 38.6±5.8 days respectively for 192 patients); (iv) detected ISR-HRM types with as much discrimination as PFGE and more than MLST; and (v) detected ISR-HRM types that differentiated some isolates that were identical by PFGE and MLST. In conjunction with the rapid and accurate van genotyping method described here, this ISR-HRM typing and identification method can be used as a stable identification and typing method with predictable instability based on recombination and concerted evolution of the rrn operon that will complement existing typing methods.

Widespread Emergence of Multidrug Resistant Pseudomonas aeruginosa Isolated from CSF Samples

Bacterial infections of the central nervous system, especially acute infections such as bacterial meningitis require immediate, invariably empiric antibiotic therapy due to the widespread emergence of resistance among bacterial species. Nosocomial infections by Pseudomonas aeruginosa have been described with an increasing trend towards multidrug resistance. P. aeruginosa isolates n = 53 (66%) isolated from the cerebrospinal fluid (CSF) were used for this study. Antibiotic resistance in 53 P. aeruginosa clinical isolates from 80 CSF samples were evaluated. Of these, n = 42 (80%) of the isolates showed multidrug resistance to more than eight antibiotics and n = 17 (32%) isolates were found to be imipenem resistant P. aeruginosa (IMPR-Pa). Genotypical examination by ERIC based PCR revealed minor genetic variations. Polymicrobial infections are common in the CSF samples. However, high prevalence of P. aeruginosa as an opportunistic pathogen has been developing with increased resistance to antimicrobial agents and thus becoming a significant threat.

Multicenter study evaluating the role of enterococci in secondary bacterial peritonitis

A 1-year prospective multicenter study was performed to explore the significance of the presence of enterococci in cultures of peritoneal fluid from patients with secondary bacterial peritonitis in seven Spanish hospitals. The clinical records of patients with positive peritoneal fluid cultures were reviewed and distributed into cases (patients with cultures yielding enterococci) and controls (patients with cultures not yielding enterococci). Of a total of 158 records, 38 (24.1%) were cases and 120 (75.9%) were controls. The percentages or the scores (cases versus controls) for the variables included in the multivariate analysis were as follows: age of >50 years, 89.5% versus 68.3%; malignancy, 39.5% versus 18.3%; chronic obstructive pulmonary disease (COPD), 15.8% versus 4.2%; postoperative peritonitis, 55.3% versus 30.1%; nosocomial onset, 57.9% versus 34.2%; a higher Charlson comorbidity index, 3.29 +/- 3.38 versus 1.84 +/- 2.31; APACHE II score, 10.71 +/- 4.37 versus 8.76 +/- 5.49; ultimately or rapidly fatal disease, 63.2% versus 34.8%; need for surgical reintervention, 36.1% versus 15.1%; and admission to an intensive care unit, 45.9% versus 30.8%. In the multivariate analysis, enterococci were associated only with postoperative peritonitis (P = 0.009; odds ratio [OR] = 5.0; 95% confidence interval [CI] = 1.49 to 16.80), a higher Charlson comorbidity index (P = 0.002; OR = 1.30; 95% CI = 1.11 to 1.54), and COPD (P = 0.046; OR = 6.50; 95% CI = 1.04 to 40.73). The results of this study showed that enterococci were associated with comorbidity. An association with mortality could not be demonstrated.

Escherichia coli and its lipopolysaccharide modulate in vitro Candida biofilm formation

Demystification of microbial behaviour in mixed biofilms could have a major impact on our understanding of infectious diseases. The objectives of this study were to evaluate in vitro the interactions of six different Candida species and a Gram-negative coliform, Escherichia coli, in dual-species biofilms, and to assess the effect of E. coli LPS on Candida biofilm formation. A single isolate of E. coli ATCC 25922 and six different species of Candida, Candida albicans ATCC 90028, Candida glabrata ATCC 90030, Candida krusei ATCC 6258, Candida tropicalis ATCC 13803, Candida parapsilosis ATCC 22019 and Candida dubliniensis MYA-646, were studied using a standard biofilm assay. Each Candida species was co-cultured with E. coli on a polystyrene surface and biofilm formation was quantified by a c.f.u. assay. The biofilm was then analysed by Live/Dead staining and fluorescence microscopy (confocal laser-scanning microscopy, CLSM), whilst scanning electron microscopy (SEM) was employed to visualize the biofilm architecture. The effect of E. coli LPS on Candida biofilm cell activity at defined time intervals was assessed with an XTT reduction assay. A significant quantitative reduction in c.f.u. counts of C. tropicalis (after 90 min), C. parapsilosis (after 90 min and 24 h), C. krusei (after 24 h) and C. dubliniensis (after 24 and 48 h) was noted on incubation with E. coli in comparison with their monospecies biofilm counterparts (P <0.05). On the other hand, a simultaneous and significant reduction in E. coli cell numbers occurred on co-culture with C. albicans (after 90 min), and an elevation of E. coli cell numbers followed co-culture with C. tropicalis (after 24 h) and C. dubliniensis (after 24 h and 48 h) (P <0.05). All quantitative findings were confirmed by SEM and CLSM analyses. By SEM observation, dual-species biofilms demonstrated scanty architecture with reduced visible cell counts at all stages of biofilm development, despite profuse growth and dense colonization in their single-species counterparts. Significantly elevated metabolic activity, as assessed by XTT readings, was observed in E. coli LPS-treated C. tropicalis and C. parapsilosis biofilms (after 48 h), whilst this had the opposite effect for C. dubliniensis (after 24 h) (P <0.05). These data indicate that E. coli and Candida species in a mixed-species environment mutually modulate biofilm development, both quantitatively and qualitatively, and that E. coli LPS appears to be a key component in mediating these outcomes.

Clinical practice guidelines for the diagnosis and management of intravascular catheter-related infection: 2009 Update by the Infectious Diseases Society of America

These updated guidelines replace the previous management guidelines published in 2001. The guidelines are intended for use by health care providers who care for patients who either have these infections or may be at risk for them.

Occurrence, population structure, and antimicrobial resistance of enterococci in marginal and apical periodontitis

Subgingival plaque samples and root canal samples were collected from 2,839 marginal periodontitis (MP) patients and 21 apical periodontitis (AP) patients. Enterococcus species were identified by a series of phenotypic and genotypic tests. Antimicrobial susceptibility assays were performed by an agar disk diffusion test. Multilocus sequence typing (MLST), eBURST, and minimum spanning tree were used for enterococcal genetic clustering and population analysis. Enterococcus faecalis was recovered from 3.7% MP patients and 9.5% AP patients, and Enterococcus faecium was recovered from 0.04% MP patients. Enterococci were detected more often in older male patients. E. faecalis isolates of MP were found resistant to tetracycline (49.1%), erythromycin (8.5%), trimethoprim (2.8%), and gentamicin (1.9%), while one AP isolate was resistant to tetracycline. A total of 40 sequence types (STs) were resolved in 108 E. faecalis isolates. Comparison with E. faecalis international MLST database revealed that 27 STs were previously found, 13 STs were novel, and several major clonal complexes in the database were also found in MP isolates. The tetracycline-resistant isolates distributed mainly in the major clonal complexes and singletons, whereas the erythromycin-resistant isolates were more dispersed. Although the rate of occurrence of enterococci recovered in the MP and AP samples was low, 50% of these isolates are resistant to at least one antimicrobial agent, which is most often tetracycline. This implies that subgingival E. faecalis might represent a reservoir of resistance to tetracycline and erythromycin. The subgingival E. faecalis isolates show high genetic diversity but are grouped, in general, with the known isolates from the international database.

Empiric therapy for intravenous central line infections and nosocomially-acquired acute bacterial endocarditis

Intravascular catheters are essential devices in the intensive care unit, yet catheter-related bloodstream infections (CR-BSI) are associated with increased morbidity and mortality, prolonged hospitalization, and increased medical costs. Management of a CR-BSI requires antibiotics, with or without catheter removal, depending on patient and etiologic factors. Because of the high frequency of staphylococcal infections, it is wise to use a glycopeptide empirically. Extra coverage for Gram-negative bacilli should be administered in severely ill or immunocompromised patients. Once culture and sensitivity results are known, antibiotic therapy can be more selective.

Hospital outbreak of vancomycin-resistant enterococci caused by a single clone of Enterococcus raffinosus and several clones of Enterococcus faecium

A mixed outbreak caused by vancomycin-resistant Enterococcus raffinosus and Enterococcus faecium carrying the vanA gene was analysed. The outbreak occurred in a large hospital in Poland and affected 27 patients, most of whom were colonised, in three wards, including the haematology unit. The E. raffinosus isolates had a high-level multiresistant phenotype and were initially misidentified as Enterococcus avium; their unambiguous identification was provided by multilocus sequence analysis. The molecular investigation demonstrated the clonal character of the E. raffinosus outbreak and the polyclonal structure of the E. faecium isolates. All of the isolates carried the same Tn1546-like element containing an IS1251-like insertion sequence, located on a c. 50-kb conjugative plasmid. One of the E. faecium clones, found previously to be endemic in the hospital, was probably the source of the plasmid. The results of the study suggest that difficulties in identification may have led to an underestimate of the importance of E. raffinosus in vancomycin-resistant enterococci (VRE) control strategies.

Comparison of the BD GeneOhm VanR assay to culture for identification of vancomycin-resistant enterococci in rectal and stool specimens

Active screening for vancomycin-resistant enterococci (VRE) in rectal and stool specimens has been recommended to limit the spread of antimicrobial resistance within certain high-risk populations. Directly from 502 rectal swabs and stool specimens, we evaluated the diagnostic performance of the BD GeneOhm VanR assay (BD GeneOhm, San Diego, CA), a rapid real-time PCR test that detects the presence of vanA and/or vanB genes. The VanR assay was compared to culture consisting of both bile-esculin-azide agar with 6 mug/ml vancomycin (BEAV agar) (BD Diagnostics, Sparks, MD) and BEAV broth with 8 mug/ml vancomycin (Hardy Diagnostics, Santa Maria, CA). Enterococci were identified to the species level using standard biochemical tests and a Phoenix automated microbiology system (BD Diagnostics, Sparks, MD). The susceptibility of the enterococci to vancomycin and teicoplanin was determined using an Etest (AB Biodisk, Solna, Sweden). VRE were initially isolated from 147 cultures, and the VanR assay detected 142 of the 147 positive cultures for a sensitivity of 96.6%. The specificity was 87.0% (309/355) largely due to false positives seen with the vanB portion of the assay. The sensitivity when testing rectal swabs was 98.3%, and the sensitivity for stool samples was 95.4% (P = 0.643). The specificity of rectal swabs was comparable to that of the stool specimens (87.5% and 86.5%, respectively). When used only to detect VanA resistance, the VanR assay was 94.4% (136/144) sensitive and 96.4% (345/358) specific, with positive and negative predictive values of 91.3% and 97.7%, respectively. In summary, the BD GeneOhm VanR assay is a good screening test for VRE in our population of predominantly vanA-colonized patients. However, patient samples testing only vanB positive should be confirmed by another method for the presence of VRE.

Antimicrobial resistance and molecular epidemiology of vancomycin-resistant enterococci from North America and Europe: a report from the SENTRY antimicrobial surveillance program

Increases in prevalence of vancomycin-resistant enterococci (VRE) have been documented globally since its emergence in the 1980s. A SENTRY Antimicrobial Surveillance Program (2003) objective monitored VRE isolates with respect to antimicrobial susceptibility trends, geographic resistance variability, and clonal dissemination. In 2003, VRE isolates from North America (United States and Canada, n = 839, 26 sites) and Europe (n = 56, 10 sites) were susceptibility tested using Clinical and Laboratory Standards Institute (CLSI) reference methodologies. Based on resistance profiles, 155 isolates displayed similar multidrug-resistant (MDR) profiles and were temporally related; these were subsequently submitted for typing by pulsed-field gel electrophoresis (PFGE). Most of the submitted isolates were Enterococcus faecium (91.0%) and Enterococcus faecalis (7.8%). Among VRE, the VanA phenotype was more prevalent in North America (76%) than Europe (40%), and all isolates had elevated resistance rates to other antimicrobial classes including the following: 1) chloramphenicol resistance among E. faecalis being greater in North America than in Europe (28.6% versus 7.1%, respectively) but reversed among E. faecium (0.5% and 15.0%, the latter due to clonal occurrences); 2) ciprofloxacin resistance in North America >99% for both species and in Europe varying from 85.7% to 87.5%; 3) rare occurrences of linezolid resistance in North America (0.8% to 1.8%) due to G2576U ribosomal mutation; 4) higher quinupristin/dalfopristin resistance observed among European E. faecium strains (10.0% versus 0.6%); and 5) higher rifampin resistance rates among European E. faecalis (21.4% versus 5.4%). Thirty-five MDR epidemic clusters were identified by PFGE in 21 North American and 2 European medical centers including the following: 1) VanA (20 sites, 27 clonal occurrences) and VanB (1 site, 2 clonal occurrences); 2) elevated quinupristin/dalfopristin MIC results (not vatD/E, 3 sites); and 3) chloramphenicol resistance (chloramphenicol acetyltransferase-positive strains, 3 sites). The esp gene, part of the putative E. faecium pathogenicity island and a marker for the clonal complex-17 lineage, was detected in 76% of vancomycin-resistant E. faecium. Clonal spread appears to be a dominant factor of MDR VRE dissemination on both continents, and further monitoring is critical to assist in the control of these resistant pathogens.

Biofilm formation byCandida albicansmutants for genes coding fungal proteins exhibiting the eight-cysteine-containing CFEM domain

Several features and functions of a Candida albicans gene, PGA10 (also designated as RBT51), coding for a putative polypeptide species belonging to a subset of fungal proteins containing an eight-cysteine domain referred as CFEM (Common in several Fungal Extracellular Membrane proteins), are described. The ORF of the gene (ORF19.5674) encoded a protein of 250 amino acids, with a predicted molecular mass of 25.17 kDa. The product of the PGA10 gene also exhibited some features reminiscent of a class II-type hydrophobin. Deletion of PGA10 resulted in a cascade of pleiotropic effects, mostly affecting cell-surface-related properties. Thus, the null pga10Delta mutant displayed an increased sensitivity to cell-wall-perturbing agents and formed fragile biofilms that appeared partially split and weakly attached to the substratum. The biofilm-forming ability of several C. albicans mutants with single, double and triple deletions of genes encoding other protein species also containing the CFEM domain (RBT5 and WAP1/CSA1) was determined. These mutants also exhibited an abnormal ability to form biofilms. Overall, the evidence presented here suggests that fungal proteins containing the CFEM domain (Pga10p/Rbt51p, Rbt5p and Wap1p/Csa1p) may play a key role in the formation, development and/or maintenance of the biofilm structure in C. albicans.

Glycopeptides: Update on an old successful antibiotic class

The natural product glycopeptides vancomycin and teicoplanin have come to play a significant role in the therapy for Gram-positive bacterial infections. In particular vancomycin is the choice for empiric therapy of these infections primarily due to its activity against and the significance of methicillin-resistant Staphylococcus aureus. While high-level problematic glycopeptide resistance among enterococci was observed initially and continues to increase, the slow creep of vancomycin intermediate susceptibility and the fear of frank resistance among the staphylococci have precipitated increasing work leading to creation of new semisynthetic analogs. These new agents, including dalbavancin and telavancin, are within 1-2 years availability in the clinic. Interestingly, chemical modifications resulting in these second-generation analogs and additional characterization have revealed new mechanisms of antibacterial action, and plasticity regarding additional properties including pharmacokinetics for the drug candidates. The unique beneficial properties of the near term vancomycin replacements, semisynthesis of additional important analogs, and advances in metabolic engineering resulting in novel scaffolds signal a new era for the glycopeptide antibiotics.

Antimicrobial Management of Complicated Skin and Skin Structure Infections in the Era of Emerging Resistance

BACKGROUND

Complicated skin and skin structure infections (cSSSIs) are among the most common infections treated in the hospital setting. The mainstays of treatment continue to be antimicrobial therapy combined with appropriate surgical intervention. Due to increasing resistance among pathogens commonly implicated in cSSSIs, the objectives of this review were to describe the potential pathogens causing skin infections, the implications of resistance to currently used drug therapy, and the role of new antibiotics with activity for pathogens causing cSSSIs.

METHODS

Relevant information from the primary literature and review articles were identified through a MEDLINE search of the medical literature (1980 to the present) using the terms abscess, wound infection, skin and skin structure infection, antibiotics, resistance, quinupristin- dalfopristin, linezolid, daptomycin, tigecycline, oritavancin, and dalbavancin. Meeting posters and slides were identified from the Interscience Conference of Antimicrobial Agents and Chemotherapy (1998-2004) for supplemental data.

RESULTS

The most commonly implicated pathogens in cSSSIs include gram-positive bacteria, specifically Staphylococcus aureus. Gram-negative and mixed organisms are additionally encountered in serious cSSSI. Antimicrobial resistance among both gram-positive and gramnegative bacteria has increased significantly during the last decade, with methicillin resistance among S. aureus approaching 60% in hospitals and becoming more frequent in the community as well. As a result, resistance is the driving factor for treatment failure and rising costs for infection management. Few antimicrobial agents are available currently to treat resistant bacteria in cSSSIs; vancomycin is currently the drug of choice against resistant grampositive cocci; however, resistance to this agent has appeared in enterococci and S. aureus. Several new antibiotics such as linezolid and daptomycin are now available for the management of cSSSIs. Other agents such as tigecycline are under investigation and should be available soon to increase treatment options for cSSSIs caused by resistant bacteria.

CONCLUSIONS

Although the resistance of cSSSI pathogens is problematic, new antibiotics with broad-spectrum activity against resistant gram-positive and gram-negative bacteria are promising for the management of severe cSSSIs.

Comparison of Mortality Associated with Vancomycin-Resistant and Vancomycin-Susceptible Enterococcal Bloodstream Infections: A Meta-analysis

BACKGROUND

Whether vancomycin resistance is independently associated with mortality among patients with enterococcal bloodstream infection (BSI) is controversial. To address this issue, we performed a systematic literature review with meta-analysis.

METHODS

Data sources were studies identified using the MEDLINE database (for articles from 1988 through March 2003), the Cochrane Library (for articles published up to March 2003), and bibliographies of identified articles. Inclusion criteria were that the study assessed mortality after enterococcal BSI, compared mortality after vancomycin-resistant enterococci (VRE) BSI with that after vancomycin-susceptible enterococci (VSE) BSI, and adjusted for severity of illness. Study exclusion criteria were as follows: no report of the adjusted measure of effect (adjusted odds ratio [OR], adjusted hazard ratio, or adjusted relative risk) of vancomycin resistance on mortality available and/or its adjusted 95% confidence interval (95% CI). Data in the tables, figures, or text were independently extracted by 2 of the authors. Individual weights were calculated using the 95% CI of the adjusted measures of effect performing both fixed-effect and random-effects models.

RESULTS

Nine studies were eligible (11 studies met the inclusion criteria, and 2 were excluded), with a total of 1614 enterococcal BSI episodes (683 VRE episodes and 931 VSE episodes). Patients with bacteremia caused by VRE were more likely to die than were those with VSE bacteremia (summary OR, 2.52; 95% CI, 1.9-3.4).

CONCLUSIONS

Vancomycin resistance is independently associated with increased mortality among patients with enterococcal bloodstream infection.

New therapeutic agents for resistant Gram-positive infections

Gram-positive bacteria are an increasingly common cause of community acquired and nosocomial infections, and their resistance to antibiotics is increasing. The recent reports from several continents of methicillin-resistant Staphylococcus aureus with reduced glycopeptide-susceptibility is of grave concern. New agents are required to meet these threats and several classes of compounds are under development. This review focuses on agents that have been recently licensed or are presently in clinical development for the treatment of serious multidrug-resistant staphylococcal, enterococcal and pneumococcal infections, including methicillin-resistant S. aureus and vancomycin-resistant enterococci.

Nosocomial bloodstream infections in US hospitals: analysis of 24,179 cases from a prospective nationwide surveillance study

BACKGROUND

Nosocomial bloodstream infections (BSIs) are important causes of morbidity and mortality in the United States.

METHODS

Data from a nationwide, concurrent surveillance study (Surveillance and Control of Pathogens of Epidemiological Importance [SCOPE]) were used to examine the secular trends in the epidemiology and microbiology of nosocomial BSIs.

RESULTS

Our study detected 24,179 cases of nosocomial BSI in 49 US hospitals over a 7-year period from March 1995 through September 2002 (60 cases per 10,000 hospital admissions). Eighty-seven percent of BSIs were monomicrobial. Gram-positive organisms caused 65% of these BSIs, gram-negative organisms caused 25%, and fungi caused 9.5%. The crude mortality rate was 27%. The most-common organisms causing BSIs were coagulase-negative staphylococci (CoNS) (31% of isolates), Staphylococcus aureus (20%), enterococci (9%), and Candida species (9%). The mean interval between admission and infection was 13 days for infection with Escherichia coli, 16 days for S. aureus, 22 days for Candida species and Klebsiella species, 23 days for enterococci, and 26 days for Acinetobacter species. CoNS, Pseudomonas species, Enterobacter species, Serratia species, and Acinetobacter species were more likely to cause infections in patients in intensive care units (P<.001). In neutropenic patients, infections with Candida species, enterococci, and viridans group streptococci were significantly more common. The proportion of S. aureus isolates with methicillin resistance increased from 22% in 1995 to 57% in 2001 (P<.001, trend analysis). Vancomycin resistance was seen in 2% of Enterococcus faecalis isolates and in 60% of Enterococcus faecium isolates.

CONCLUSION

In this study, one of the largest multicenter studies performed to date, we found that the proportion of nosocomial BSIs due to antibiotic-resistant organisms is increasing in US hospitals.

The status of antimicrobial resistance in Taiwan among gram-negative pathogens: the Taiwan surveillance of antimicrobial resistance (TSAR) program, 2000

In a nationwide surveillance of antimicrobial resistance (Taiwan Surveillance of Antimicrobial Resistance, TSAR), isolates were collected from 21 medical centers and regional hospitals throughout Taiwan over a three-month period in 2000 (TSAR II). This report summarizes susceptibility data of 7 common Gram-negative bacilli (Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Proteus mirabilis, Enterobacter cloacae, Pseudomonas aeruginosa, and Acinetobacter baumannii) in the TSAR II collection and compared selected key forms of resistance by epidemiologic factors and with isolates collected in 1998 (TSAR I) as well as with data from international surveillance studies. Resistance of the 5 Enterobacteriaceae species to most of the commonly prescribed "first-line" antimicrobials in Taiwan, such as ampicillin (78% in E. coli, 68% in P. mirabilis), gentamicin (19% in K. pneumonia to 66% in S. marcescens), and trimethoprim/sulfamethoxazole (29% in K. pneumoniae to 70% in P. mirabilis), was high, several of which are higher than other countries. Resistance to certain broad-spectrum antimicrobials is also more acute in Taiwan than most Western countries, such as ceftazidime resistant A. baumannii (73%) and ciprofloxacin resistant E. coli (12%). Differences in geographic regions and specimen types were associated with certain forms of resistance in TSAR II; however, the resistance problem is prevalent among both inpatients and outpatients of not only medical centers but also regional hospitals throughout Taiwan.

History of the development of azole derivatives

Until the 1940s, relatively few agents were available for the treatment of systemic fungal infections. The development of the polyene antifungals represented a major advance in medical mycology. Although amphotericin B quickly became the mainstay of therapy for serious infections, its use was associated with infusion-related side-effects and dose-limiting nephrotoxicity. The continued search for new and less toxic antifungals led to the discovery of the azoles several decades later. Ketoconazole, the first available compound for the oral treatment of systemic fungal infections, was released in the early 1980s. For almost a decade, ketoconazole was regarded as the drug of choice in nonlife-threatening endemic mycoses. The introduction of the first-generation triazoles represented a second major advance in the treatment of fungal infections. Both fluconazole and itraconazole displayed a broader spectrum of antifungal activity than the imidazoles and had a markedly improved safety profile compared with amphotericin B and ketoconazole. Despite widespread use, however, these agents became subject to a number of clinically important limitations related to their suboptimal spectrum of activity, the development of resistance, the induction of hazardous drug-drug interactions, their less than optimal pharmacokinetic profile (itraconazole capsules), and toxicity. In order to overcome these limitations, several analogues have been developed. These so-called 'second-generation' triazoles, including voriconazole, posaconazole and ravuconazole, have greater potency and possess increased activity against resistant and emerging pathogens, in particular against Aspergillus spp. If the toxicity profile of these agents is comparable to or better than that of the first-generation triazoles and drug interactions remain manageable, then these compounds represent a true expansion of our antifungal arsenal.

[Antimicrobial susceptibility and frequency of occurrence of clinical blood isolates in Sfax-Tunisia (1993-1998)]

Antimicrobial susceptibility and frequency of occurrence of clinical blood isolates in Sfax-Tunisia (1993-1998). The choice of antimicrobial therapy for the treatment of bacteremia is often empirical and based on the knowledge of susceptibility profiles of the most common bacteria causing such infections. This study determines the bacterial etiology of bacteremic episodes and antimicrobial susceptibility patterns recorded at a teaching hospital, from January 1993 to December 1998. We collected 2979 strains responsible for bacteremia. Gram negative bacteria were predominant (60%). The organisms recovered most frequently were Staphylococcus aureus (18.9%), Escherichia coli (14.7%), Klebsiella pneumoniae (14%) and Pseudomonas aeruginosa (7.6%). The incidence of resistance to methicillin were 17.4% for Staphylococcus aureus and 26.8% for coagulase negative Staphylococcus. No resistance to glycopeptides was observed among the enterococci and staphylococci studied. 27.7% of enterobacteriaceae were resistant to third generation cephalosporins. Imipenem was the most active agent against gram negative bacteria. To carry out a surveillance of bacteremic episodes occurring at every hospital, it is necessary to provide valuable information which should be the basis for effective empiric therapy.

Enterococcal infections: host response, therapeutic, and prophylactic possibilities

The emergence of resistance against multiple antibiotics and the increasing frequency with which Enterococcus faecalis and Enterococcus faecium are isolated from hospitalized patients underscore the necessity for a better understanding of the virulence mechanisms of this pathogen and the development of alternatives to current antibiotic treatments. The genetic plasticity of enterococci and their ability to rapidly acquire and/or develop resistance against many clinically important antibiotics and to transfer these resistance determinants to other more pathogenic microorganisms makes the search for alternative treatment and preventive options even more important. A capsular polysaccharide antigen has recently been characterized that is the target of opsonic antibodies. A limited number of clinically relevant serotypes exist, and the development of an enterococcal vaccine based on capsular polysaccharides may improve our ability to prevent and treat these infections. Additional enterococcal surface antigens, including ABC transporter proteins and other virulence factors, such as aggregation substance (AS), may also be useful targets for therapeutic antibodies.

Comparative in vitro activities of AC98-6446, a novel semisynthetic glycopeptide derivative of the natural product mannopeptimycin alpha, and other antimicrobial agents against gram-positive clinical isolates

AC98-6446 is a novel semisynthetic cyclic glycopeptide antibiotic related to the natural product mannopeptimycin alpha (AC98-1). In the present study the activity of AC98-6446 was evaluated against a variety of recent clinical gram-positive pathogens including multiply resistant strains. AC98-6446 demonstrated similar potent activities against methicillin-susceptible and methicillin-resistant staphylococci and glycopeptide-intermediate staphylococcal isolates (MICs at which 90% of isolates are inhibited [MIC(90)s], 0.03 to 0.06 microg/ml). AC98-6446 also demonstrated good activities against both vancomycin-resistant and -susceptible strains of enterococci (MIC(90)s, 0.12 and 0.25 microg/ml, respectively) as well as against streptococcal strains (MIC(90)s, <or= 0.008 to 0.03 microg/ml). AC98-6446 demonstrated bactericidal activity in terms of the reduction in the viable counts (>3 log(10) CFU/ml) of staphylococcal and streptococcal isolates and a marked decrease in the viable counts of most enterococcal strains (from 0.2 to 2.5 log(10) CFU/ml). Unlike vancomycin, which demonstrates time-dependent killing, AC98-6446 demonstrated concentration-dependent killing. The potent activity, novel structure, and bactericidal activity demonstrated by AC98-6446 make it an attractive candidate for further development.

Favorable impact of a multidisciplinary antibiotic management program conducted during 7 years

OBJECTIVE

To evaluate the impact of an interventional multidisciplinary antibiotic management program on expenditures for antibiotics and on the incidence of nosocomial infections caused by Clostridium difficile and antibiotic-resistant pathogens during 7 years.

DESIGN

Prospective study with comparison with preintervention trends.

SETTING

University-affiliated teaching hospital.

PATIENTS

All adult inpatients.

INTERVENTION

A multidisciplinary antibiotic management program to minimize the inappropriate use of third-generation cephalosporins was implemented in 1991. Its impact was evaluated prospectively. The incidence of nosocomial C. difficile and resistant Enterobacteriaceae infections as well as the rate of vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) were compared with those of National Nosocomial Infections Surveillance System hospitals of similar size.

RESULTS

Following implementation of the program, there was a 22% decrease in the use of parenteral broad-spectrum antibiotics (P < .0001) despite a 15% increase in acuity of patient care during the following 7 years. Concomitantly, there was a significant (P = .002) decrease in nosocomial infections caused by C. difficile and a significant (P = .02) decrease in nosocomial infections caused by resistant Enterobacteriaceae. The program also appeared to have a favorable impact on VRE rates without a sustained impact on MRSA rates.

CONCLUSION

These results suggest that an ongoing multidisciplinary antibiotic management program may have a sustained beneficial impact on both expenditures for antibiotics and the incidence of nosocomial infection by C. difficile and resistant bacterial pathogens.

Prediction model to identify patients with Staphylococcus aureus bacteremia at risk for methicillin resistance

OBJECTIVES

To identify institution-specific risk factors for MRSA bacteremia and develop an objective mechanism to estimate the probability of methicillin resistance in a given patient with Staphylococcus aureus bacteremia (SAB).

DESIGN

A cohort study was performed to identify institution-specific risk factors for MRSA. Logistic regression was used to model the likelihood of MRSA. A stepwise approach was employed to derive a parsimonious model. The MRSA prediction tool was developed from the final model.

SETTING

A 279-bed, level 1 trauma center.

PATIENTS

Between January 1, 1999, and June 30, 2001, 494 patients with clinically significant episodes of SAB were identified.

RESULTS

The MRSA rate was 45.5%. Of 18 characteristics included in the logistic regression, the only independent features for MRSA were prior antibiotic exposure (OR, 9.2; CI95, 4.8 to 17.9), hospital onset (OR, 3.0; CI95, 1.9 to 4.9), history of hospitalization (OR, 2.5; CI95, 1.5 to 3.8), and presence of decubitus ulcers (OR, 2.5; CI95, 1.2 to 4.9). The prediction tool was derived from the final model, which was shown to accurately reflect the actual MRSA distribution in the cohort.

CONCLUSION

Through multivariate modeling techniques, we were able to identify the most important determinants of MRSA at our institution and develop a tool to predict the probability of methicillin resistance in a patient with SAB. This knowledge can be used to guide empiric antibiotic selection. In the era of antibiotic resistance, such tools are essential to prevent indiscriminate antibiotic use and preserve the longevity of current antimicrobials.

Methods used for the isolation, enumeration, characterisation and identification of Enterococcus spp

This paper reviews the methodology applied for the identification and characterisation of enterococci and covers phenotypic, genotypic and phylogenetic techniques. Although conventional phenotypic typing schemes are useful for rapid and simple identification of enterococcal species for routine applications, other methods like standardised sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE), multilocus enzyme electrophoresis (MLEE), antimicrobial susceptibility testing, serotyping, pyrolysis mass spectrometry (pyMS) and vibrational spectroscopic methods allow a more in-depth characterisation of enterococci. Many of the recently described enterococcal species exhibit deviations from hitherto so-called classical enterococci with regard to their phenotypical properties. Therefore, genotypic methods have to be used to clarify their possible assignment to the genus Enterococcus. In this review, special emphasis is given on recently developed polymerase chain reaction (PCR)-based typing methods such as random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), specific and random amplification (SARA) and modifications of PCR-ribotyping as well as pulsed-field gel electrophoresis (PFGE) and partial sequence analysis. The use of PCR and probes for genus and species identification of enterococci is also considered like the application of sequence data of conserved DNA regions (e.g., ribosomal ribonucleic acid (rRNA) genes) in the case of species identification.

Development of a thermally regulated broad-spectrum promoter system for use in pathogenic gram-positive species

Selectively regulating gene expression is an essential molecular tool that is lacking for many pathogenic gram-positive bacteria. In this report, we describe the evaluation of a series of promoters regulated by the bacteriophage P1 temperature-sensitive C1 repressor in Enterococcus faecium, Enterococcus faecalis, and Staphylococcus aureus. Using the lacZ gene to monitor gene expression, we examined the strength, basal expression, and induced expression of synthetic promoters carrying C1 operator sites. The promoters exhibited extremely low basal expression and, under inducing conditions, gave high levels of expression (100- to 1,000-fold induction). We demonstrate that the promoter system could be modulated by temperature and showed rapid induction and that the mechanism of regulation occurred at the level of transcription. Controlled expression with the same constructs was also demonstrated in the gram-negative bacterium Escherichia coli. However, low basal expression and the ability to achieve derepression were dependent on both the number of mismatches in the C1 operator sites and the promoter driving c1 expression. Since the promoters were designed to contain conserved promoter elements from gram-positive species and were constructed in a broad-host-range plasmid, this system will provide a new opportunity for controlled gene expression in a variety of gram-positive bacteria.

Rapid detection of vanA and vanB genes directly from clinical specimens and enrichment broths by real-time multiplex PCR assay

A real-time PCR assay previously developed for use on the Roche LightCycler platform was investigated as an alternative to culture for the direct detection of vancomycin-resistant enterococci (VRE) in clinical specimens. PCR primers and fluorescence resonance energy transfer hybridization probes specific for the vanA and vanB genes were combined in a multiplex real-time PCR assay performed directly with fecal material obtained by rectal swabbing and with enrichment broth samples. DNA was prepared from the rectal swabs and enrichment broths with a commercially available DNA preparation column designed specifically for use with fecal specimens. One hundred eighty duplicate rectal swabs were obtained from 42 patients who were previously found to be positive for VRE and who were being monitored for carriage of VRE. Direct and enrichment broth cultures were performed with one swab, while PCR was performed with the other swab as well as any corresponding presumptive positive enrichment broth. In total, 100 specimens from 30 patients remained positive for VRE by at least one method. The multiplex real-time PCR was positive for 88 enrichment broths of rectal swabs from 27 patients but for only 45 rectal swabs from 15 patients. Direct culture was positive for VRE for only 43 specimens from 11 patients, while enrichment broth culture was positive for VRE for 75 specimens from 22 patients. Inhibition studies for the multiplex real-time PCR assay, performed by spiking the DNA extracts from 50 negative rectal swabs and the corresponding enrichment broths with between 1 and 10 CFU of a VanB Enterococcus faecium strain, detected inhibition rates of 55.1 and 10%, respectively. PCR performed directly with enrichment broths was found to be significantly more sensitive than enrichment broth culture (P < 0.025). Negative samples were identified significantly earlier by PCR than by culture alone.

Production of enterolysin A by a raw milk enterococcal isolate exhibiting multiple virulence factors

Even though enterococci are a common cause of human infection they can readily be isolated from a range of food sources, including various meat and dairy products. An enterococcal strain, DPC5280, which exhibits a broad spectrum of inhibition against many Gram-positive bacteria was recently isolated from an Irish raw milk sample. Characterization of the inhibition revealed that the strain exhibits haemolytic activity characteristic of the two-component lantibiotic cytolysin and also produces a heat-labile antimicrobial protein of 34 kDa. The latter protein displayed cell wall hydrolytic activity, as evidenced by zymogram gels containing autoclaved lactococcal cells. N-terminal sequencing of the purified protein yielded the sequence ASNEWS which is 100 % identical to enterolysin A (accession no. AF249740), a protein which shares 28 and 29 % identity to the Gly-Gly endopeptidases, lysostaphin and zoocin A, respectively. Indeed, amplification of entL from DPC5280 and sequencing revealed that the protein is 100 % identical to enterolysin A. The DPC5280 strain also contained the determinants associated with multiple virulence factors, including gelatinase, aggregation substance and multiple antibiotic resistance. The linkage of this cell-wall-degrading enzyme to other virulence factors in enterococci may contribute to the competitiveness of pathogenic enterococci when found in complex microbial environments such as food and the gastrointestinal tract.

Vancomycin-resistant enterococci: 15 years and counting

We review the history of vancomycin-resistant enterococci (VRE) and propose a causal model illustrating the roles of exposure to VRE reservoirs, patient characteristics, antimicrobial exposure, and prevalence of VRE in the progression from potential VRE reservoirs to active disease in hospitalized patients. Differences in VRE colonization and VRE infection are discussed with respect to hospital surveillance methodology and implications for interventions. We further document clonal transmission of VRE in a large, urban, teaching hospital and demonstrate VRE susceptibility to a wide array of antimicrobial agents. This model can guide the identification of mutable factors that are focal points for intervention.

Species prevalence and antibacterial resistance of enterococci isolated in Kuwait hospitals

This study investigated the species prevalence and antibacterial resistance among enterococci isolated in Kuwait hospitals. They consisted of 415 isolates of Enterococcus faecalis (85.3 %), Enterococcus faecium (7.7 %), Enterococcus casseliflavus (4.0 %), Enterococcus avium (1.2 %), Enterococcus durans (1.0 %), Enterococcus gallinarium (0.5 %) and Enterococcus bovis (0.2 %) isolated from urine (36.6 %), blood (10.4 %), wound swabs (11.0 %), stool samples (12.0 %), high vaginal swabs (9.0 %), endocervical swabs (3.0 %) and miscellaneous sources (18.0 %). All of them were susceptible to linezolid. Fifty-two (12.5 %) isolates were ampicillin resistant but none of them produced beta-lactamase. They were resistant to erythromycin (63.3 %), tetracycline (60.5 %), ciprofloxacin (40.0 %), chloramphenicol (28.0 %), vancomycin (2.6 %), and teicoplanin (2.6 %). Fourteen, 19 and 20 % of them expressed high-level resistance to gentamicin, kanamycin and streptomycin, respectively. All of the vancomycin-resistant strains carried the vanA phenotype and genotype. There was no evidence of clonal spread of the vancomycin-resistant isolates.

Real-time PCR for the rapid detection of vanA and vanB genes

A real-time PCR assay suitable for use on the Roche LightCycler platform was developed to replace an existing gel-based PCR assay for the simultaneous detection of the vanA & vanB genes in enterococcal isolates. Novel Fluorescence Resonance Energy Transfer (FRET) hybridization probes were designed. The multiplex real-time PCR assay and the existing gel-based assay were 100% concordant and both correctly detected the vanA or vanB genes in 4/4 VanA E. faecium and 25/25 VanB E. faecium. Additionally, 1/1 VanC1 E. gallinarum, 1/1 VanC2 E. casseliflavus and 47/47 vancomycin susceptible enterococci were negative for the vanA and vanB genes in both PCR assays. Results were available within 1.5 h for the real-time PCR assay compared to up to 5.5 h for the conventional PCR assay.

Epidemiology of vancomycin-resistant Enterococcus faecium under a selective isolation policy at an urban county hospital

BACKGROUND

We report our experience in a county hospital with the use of selective contact isolation for patients with vancomycin-resistant Enterococcus faecium (VREF). About 12% of patients with VREF are isolated for reasons such as draining wounds and uncontrolled diarrhea.

METHODS

Passive surveillance identified all inpatients (181) from 1995 to 1999 with cultures positive for VREF. Data were collected via electronic databases and from prospectively maintained infection control records. Isolates were typed with use of pulsed-field gel electrophoresis.

RESULTS

Nearly all patients (175/181) with VREF had been admitted at least 48 hours or had a history of previous hospitalization. Most patients (69%) had urine cultures positive for VREF without blood cultures positive for the organism. Only 12 of 127 (9.%) patients with complete data had VREF infection on the basis of receiving treatment and/or having more than 1 blood culture positive for VREF. After VREF became endemic, statistically significant increased prevalence was not detected via surveillance of clinical cultures nor sequential point-prevalence studies. Two major genotypes carrying vanB resistance genes were identified and persisted throughout the period studied. VREF persisted in individual patients up to 46 months.

CONCLUSIONS

The number of VREF infections in this facility has been low, despite appreciable colonization, for an extended period during which selective isolation was used.

Inhibition of Candida albicans biofilm formation by farnesol, a quorum-sensing molecule

Farnesol is a quorum-sensing molecule that inhibits filamentation in Candida albicans. Both filamentation and quorum sensing are deemed to be important factors in C. albicans biofilm development. Here we examined the effect of farnesol on C. albicans biofilm formation. C. albicans adherent cell populations (after 0, 1, 2, and 4 h of adherence) and preformed biofilms (24 h) were treated with various concentrations of farnesol (0, 3, 30, and 300 micro M) and incubated at 37 degrees C for 24 h. The extent and characteristics of biofilm formation were then assessed microscopically and with a semiquantitative colorimetric technique based on the use of 2,3-bis(2-methoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium-5-carboxanilide. The results indicated that the effect of farnesol was dependent on the concentration of this compound and the initial adherence time, and preincubation with 300 micro M farnesol completely inhibited biofilm formation. Supernatant media recovered from mature biofilms inhibited the ability of planktonic C. albicans to form filaments, indicating that a morphogenetic autoregulatory compound is produced in situ in biofilms. Northern blot analysis of RNA extracted from cells in biofilms indicated that the levels of expression of HWP1, encoding a hypha-specific wall protein, were decreased in farnesol-treated biofilms compared to the levels in controls. Our results indicate that farnesol acts as a naturally occurring quorum-sensing molecule which inhibits biofilm formation, and we discuss its potential for further development and use as a novel therapeutic agent.