Risk factors for acquiring ampicillin-resistant enterococci and clinical outcomes at a Canadian tertiary-care hospital

Faecal carriage of high-level aminoglycoside-resistant and ampicillin-resistant Enterococcus species in healthy Iranian children

OBJECTIVES

High-level aminoglycoside, ampicillin and vancomycin resistance and virulence genes among enterococcal isolates collected from healthy middle-school children in Ardabil, Iran, during 2016 were investigated.

METHODS

Totally, 305 faecal specimens were collected. Isolates underwent antimicrobial susceptibility testing, virulence gene detection and molecular typing.

RESULTS

Totally, 409 enterococcal isolates were collected, comprising Enterococcus faecium (235; 57.5%), Enterococcus faecalis (56; 13.7%) and other Enterococcus spp. (118; 28.9%). Overall, 71 (17.4%), 11 (2.7%) and 10 (2.4%) isolates were identified as high-level streptomycin-resistant (HLSR), high-level gentamicin-resistant (HLGR) and ampicillin-resistant (AR), respectively. Among HLSR isolates, 40 (56.3%), 5 (7.0%) and 26 (36.6%) were E. faecium, E. faecalis and other Enterococcus spp., respectively. Among HLGR isolates 4 (36.4%) and 7 (63.6%) and among AR isolates 7 (70.0%) and 3 (30.0%) were E. faecium and other Enterococcus spp., respectively. Accordingly, 21.6%, 3.6% and 3.3% of subjects were colonised with HLSR, HLGR and AR Enterococcus spp. Carriage of HLGR, HLSR and AR isolates was associated with prior antibiotic consumption (P≤0.05). Additionally, male sex and antacid consumption were associated with AR enterococcal carriage. Moreover, 69 (97.2%), 10 (90.9%) and 9 (90.0%) of HLSR, HLGR and AR isolates were multidrug-resistant, respectively. No vancomycin-resistant enterococci were detected. ERIC-PCR revealed high genetic diversity among isolates. gelE and asa1 were major virulence genes both in E. faecalis and E. faecium. Presence of gelE was associated with HLSR and HLGR phenotypes (P≤0.05).

CONCLUSION

Community intestinal carriage of HLSR enterococci was high; however, carriage of HLGR and AR enterococci was low.

Enterococcal bacteraemia: predictive and prognostic risk factors for ampicillin resistance

To identify the predictive and prognostic factors associated with ampicillin-resistant enterococcal bacteraemia, we retrospectively reviewed demographic, microbiological and clinical data of patients attending the Kyoto University Hospital, Japan, between 2009 and 2015. Logistic regression and Cox regression analyses were performed to determine the predictive and prognostic factors, respectively. In total, 235 episodes of enterococcal bacteraemia were identified. As ampicillin susceptibility was uniform for Enterococcus faecalis isolates and almost all ampicillin-resistant isolates were E. faecium, bacteraemia due to these species was investigated separately. E. faecalis and E. faecium accounted for 41.7% (98/235) and 48.1% (113/235) of the isolates, respectively and 91.2% of all E. faecium were ampicillin resistant. Nosocomial E. faecium bacteraemia acquisition (odds ratio (OR), 13.6; 95% confidence intervals, 3.16-58.3) was associated with ampicillin-resistant isolates. Bacteraemia from an unknown source (hazard ratio (HR), 2.91; 95% CI 1.36-6.21) and an increased Pitt bacteraemia score (PBS) (HR, 1.36; 95% CI 1.21-1.52) were associated with 30-day mortality in E. faecium infections. Likewise, bacteraemia from an unknown source (HR, 4.17; 95% CI 1.25-13.9) and increased PBS (HR, 1.27; 95% CI 1.09-1.48) were associated with 30-day mortality in patients with E. faecalis bacteraemia. The empirical therapeutic administration of glycopeptides is recommended for patients with bacteraemia from an unknown source in whom severe E. faecium bacteraemia is suspected.

Risk factors for colonization with ampicillin and high-level aminoglycoside-resistant enterococci during hospitalization in the ICU and the impact of prior antimicrobial exposure definition: a prospective cohort study

The aim of our prospective cohort study was to determine the incidence, genetic relatedness and risk factors for colonization with ampicillin and high-level aminoglycoside-resistant enterococci (ARHLARE) among patients hospitalized in the intensive care unit. During 15-month period, we included 105 patients. The only independent risk factor for ARHLARE colonization was days of cefotaxime/ceftriaxone therapy [odds ratio (OR): 1.13; 95% confidence interval (CI) 1.10-1.27; P  =  0.045]. Patients with higher total use of antibiotics, patients on prolonged mechanical ventilation, and patients with urinary tract infection (UTI), were also found to be at increased risk to become colonized with ARHLARE. Pulsed-field gel electrophoresis suggested multifocal origin of the majority of the colonizing strains. Our results show that an increase in total antibiotic consumption for 10 defined daily doses (DDD)/patient increased the odds of colonization with ARHLARE for 36%. Further efforts to optimize antimicrobial use in high risk patients are proposed.

Microbiological and epidemiological studies of Enterococcus faecium resistant to amoxycillin in a university hospital in eastern France

Over 3 years, during six 1-month periods of surveillance, 69 cases of Enterococcus faecium colonisation or infection were detected in a university hospital in eastern France. Thirty-two cases involved strains resistant to amoxycillin (crude incidence of 0.21/1000 patient-days). The risk of infection with E. faecium was higher if the patient was hospitalised in a haematology ward and/or treated with cephalosporins. Amoxycillin-resistant isolates (AmRE) were isolated from different wards and time periods, and none of the characteristics studied were associated significantly with amoxycillin resistance. Amoxycillin-sensitive and -resistant isolates were characterised by pulsed-field gel electrophoresis. Three epidemic patterns were identified which contained 87.5% (28/32) of the AmRE isolates, indicating that clonal spread was responsible, at least partially, for the high incidence of AmRE in this hospital.

Exploring the pathogenesis of necrotizing fasciitis due to Streptococcus pneumoniae

Monobacterial necrotizing fasciitis is a rare form of soft tissue infection usually caused by the group A beta-hemolytic Streptococcus. Soft tissue infection is an uncommon clinical manifestation of invasive disease due to Streptococcus pneumoniae. We describe 3 cases of pneumococcal necrotizing fasciitis and explore potential pathogen-specific mechanisms of pathogenesis. The clinical characteristics of necrotizing fasciitis due to S. pneumoniae and group A beta-hemolytic Streptococcus appear to overlap. The similarities include predominant occurrence in elderly adults with underlying chronic illness, predilection for lower extremity infection, progression to toxic shock-like syndrome and a high case fatality rate. No DNA fragments corresponding to speA, speB or speC were amplified by PCR from the 3 pneumococcal isolates. Western immunoblot revealed no evidence of SpeA, SpeB or SpeC protein expression. Evaluation for protease production and cytotoxicity was unrevealing. The similar clinical presentation of pneumococcal necrotizing fasciitis to the disease caused by the group A beta-hemolytic Streptococcus has important therapeutic implications. The molecular mechanisms underlying the pathogenesis are unclear. Prospective population-based studies are required to define the epidemiology of this infection.

vanE gene cluster of vancomycin-resistant Enterococcus faecalis BM4405

Acquired VanE-type resistance to low levels of vancomycin (MIC = 16 microg/ml) in Enterococcus faecalis BM4405 is due to the inducible synthesis of peptidoglyean precursors terminating in D-alanine-D-serine (Fines,M., B. Prichon, P. Reynolds, D. Sahm, and P. Courvalin, Antimicrob. Agents Chemother. 43:2161-2164, 1999). A chromosomal location was assigned to the vanE operon by pulsed-field gel electrophoresis and hybridization, and its sequence was determined. Three genes, encoding the VanE ligase, the VanXYE DD-peptidase, and the VanTE serine racemase, that displayed 43 to 53% identity with the corresponding genes in the vanC operon were found. In addition, two genes coding for a two-component regulatory system, VanRE-VanSE, exhibiting 60 and 44% identity with VanR,-VanS, were present downstream from vanTE. However, because of a stop codon at position 78, VanSE was probably not functional. The five genes, with the same orientation, were shown to be cotranscribed by Northern analysis and reverse transcription-PCR. The vanE, vanXYE, and vanTE genes conferred inducible low-level resistance to vancomycin after cloning in E. faecalis JH2-2, probably following cross talk with a two-component regulatory system of the host.

The prevalence of faecal carriage of ampicillin-resistant and high-level gentamicin-resistant enterococci among inpatients at 10 major Norwegian hospitals

From March to October 1999, 854 patients hospitalized at 10 major Norwegian hospitals were screened for rectal carriage of ampicillin-resistant enterococci (ARE) and high-level gentamicin-resistant enterococci (HLGRE). A total of 59 ARE carriers (prevalence 6.9%, range 0-22% among hospitals) and 28 HLGRE carriers (prevalence 3.3%, range 1-11%) were detected. All ARE or HLGRE strains were susceptible to vancomycin, whereas 77% of the ARE isolates were resistant to ciprofloxacin. All the ARE strains were identified as Enterococcus faecium, and 48% of these were genomically closely related as shown by PFGE. Specific point mutations in the pbp5 gene were associated with reduced susceptibility to ampicillin. The adjusted risk of becoming a carrier of ARE was related to the use of glycopeptides [odds ratio (OR) = 4.8], the use of any antimicrobial agent (OR = 3.1) and more than one hospital admission during the last six months (OR = 2.0). Twenty-five of 28 HLGRE isolates were Enterococcus faecalis. The aacA/aphD genes were detected in 26 (93%) and the aphA3 in 19 (68%) of the HLGRE isolates. Sixty-four percent of the HLGRE isolates belonged to two PFGE clusters. Consumption of antimicrobial agents was also a significant risk factor for HLGRE colonization (OR = 5.4), while prescription of penicillins was associated with reduced risk (OR = 0.28).

In vitro assessment of urinary isolates of ampicillin-resistant enterococci

OBJECTIVE

Susceptibility and minimum inhibitory concentration (MIC) studies of ampicillin-resistant enterococci (ARE) were performed with vancomycin, ciprofloxacin, and trovafloxacin. Ampicillin MICs were determined to make comparisons with achievable urinary concentrations of ampicillin.

DESIGN

From July 1998 to April 1999, all enterococci isolated from urinary specimens were tested for susceptibility to ampicillin by disk diffusion. For all ARE, vancomycin, ciprofloxacin, and trovafloxacin susceptibilities were determined by use of either disk diffusion or the E-test. Ampicillin MICs were determined for these isolates by liquid agar microdilution testing. ARE were identified to the species level on the basis of biochemical reactions.

SETTING

The study was performed at a university-affiliated tertiary care hospital.

OUTCOME MEASURES

In vitro susceptibility studies and MIC determinations were performed in accordance with the National Committee for Clinical Laboratory Standards.

RESULTS

A total of 310 urine samples were culture positive for enterococcus. Thirty (9.7%) unduplicated isolates were resistant to ampicillin. Of these, nine ARE isolates (30%) were also vancomycin resistant, whereas only 2 ampicillin-susceptible isolates were vancomycin resistant (p < 0.05). All ARE were resistant to ciprofloxacin, and 29 (96.7%) were resistant to trovafloxacin. Nine (30%), 18 (60%), and 3 (10%) isolates had an ampicillin MIC of 128, 256, and 512 micrograms/mL, respectively. Ampicillin MICs did not differ significantly between vancomycin-susceptible and -resistant isolates (p = 0.963). Twenty-seven isolates (90%) were identified as Enterococcus faecium; the other 3 were either Enterococcus avium or Enterococcus raffinosus.

CONCLUSIONS

Ampicillin resistance is associated with resistance to vancomycin. Most ARE are resistant to fluoroquinolone antibiotics such as ciprofloxacin and trovafloxacin. Ampicillin MICs for ARE found in these urinary specimens were all within 1 dilution of 256 micrograms/mL, a concentration achievable in the urine with higher doses of oral amoxicillin or intravenous ampicillin. Additional studies are needed to assess the clinical implications of these data.

Enterococcal infections in a Greek intensive care unit: a 5-y study

In this study we determined the incidence, resistance pattern, and mortality rate associated with infection caused by Enterococcus faecalis and Enterococcus faecium among patients in a multidisciplinary intensive care unit (ICU). A total of 111 patients with E. faecalis and 60 with E. faecium infections were identified during a 5-y period (1992-96). We observed an increase in the incidence of enterococcal infections (from 5.46 to 8.46 per 1000 patients-days, p = 0.0112), due mainly to the increased incidence of E. faecium (from 0.45 to 4.06 per 1000 patients-days, p = 0.002). Blood was the most common site of enterococcus isolation. E. faecium was more resistant to antibiotics than E. faecalis, but no vancomycin resistant enterococcus was isolated. Patients with E. faecium infection had a significantly higher mortality than patients with E. faecalis infection (66% vs. 41.5%, p = 0.0035 for infection from any site and 85.7 vs. 47.7%, p = 0.012 for bacteremic patients). r 4n- D I .- .- - .. . .

Nosocomial enterococcal infections in children

OBJECTIVES

To identify factors that are associated with an increased risk of nosocomial enterococcal infection in children.

METHODS

A matched case-control study was conducted between January 1989 and July 1993 at the Children's National Medical Center, Washington DC. One control patient for each case was identified. Control patients did not have nosocomial enterococcal infections and were matched with cases on the basis of age and time of admission closest to the case within a three-month period. Data were collected from systematic review of patient medical records. One hundred and one study patients (cases) were matched with 101 control patients. A case was defined as a patient with enterococcal infection who met the Centers for Disease Control and Prevention criteria for nosocomial infection. Microbiology methods included isolation, identification, and antimicrobial susceptibility testing of enterococci from clinical specimens.

RESULTS

Risk factors associated with nosocomial enterococcal infections were determined by multiple conditional logistic regression analyses of the cases and controls. Factors identified were placement of a central line, gastrointestinal tract pathology, and administration of multiple antimicrobial agents. The median duration of antimicrobial therapy prior to diagnosis of nosocomial enterococcal infection was approximately 1 week.

CONCLUSION

The incidence of nosocomial enterococcal infections in children may be controlled by limiting the number of antimicrobial agents administered to hospitalized high risk patients. The importance of our findings is relevant in an era of increasing rates of antimicrobial resistance in nosocomial enterococcal infections.

Near absence of vancomycin-resistant enterococci but high carriage rates of quinolone-resistant ampicillin-resistant enterococci among hospitalized patients and nonhospitalized individuals in Sweden

Rates of colonization with enterococci with acquired resistance to vancomycin (vancomycin-resistant enterococci [VRE]) and ampicillin (ampicillin-resistant enterococci [ARE]) were determined by using fecal samples from 670 nonhospitalized individuals and 841 patients in 27 major hospitals. Of the hospitalized patients, 181 (21.5%) were carriers of ARE and 9 (1.1%) were carriers of VRE. In univariate analyses, length of hospital stay (odds ratio [OR], 4.6; 95% confidence interval [CI], 2.5 to 8.9) and antimicrobial therapy (OR, 4.7; 95% CI, 3.3 to 6.7) were associated with ARE colonization, as were prior treatment with penicillins (OR, 3.1; 95% CI, 1.8 to 5. 5), cephalosporins (OR, 2.9; 95% CI, 1.7 to 5.0), or quinolones (OR, 2.7; 95% CI, 1.5 to 4.7). In logistic regression analysis, antimicrobial therapy for at least 5 days was independently associated with ARE carriage (adjusted OR, 3.8; 95% CI, 2.6 to 5.4). Over 90% of the ARE isolates were fluoroquinolone resistant, whereas 14% of the ampicillin-susceptible Enterococcus faecium isolates were fluoroquinolone resistant. ARE carriage rates correlated with the use of fluoroquinolones (P = 0.04) but not with the use of ampicillin (P = 0.68) or cephalosporins (P = 0.40). All nine VRE isolates were E. faecium vanB and were found in one hospital. Seven of these isolates were related according to their types as determined by pulsed-field gel electrophoresis. Among the nonhospitalized individuals, the ARE carriage rate was lower (6%; P < 0.05), and only one person, who had recently returned from Africa, harbored VRE (E. faecium vanA). The absence of VRE colonization in nonhospitalized individuals reflects an epidemiological situation in Sweden radically different from that in countries in continental Europe where glycopeptides have been widely used for nonmedical purposes.

Enterococcal bacteremia in a tertiary care centre in Winnipeg

OBJECTIVE

To review experience with enterococcal bacteremia before the emergence of vancomycin-resistant enterococcus at a tertiary care teaching hospital.

DESIGN

Retrospective chart review of episodes of enterococcal bacteremia identified through the clinical microbiology laboratory from January 1990 to December 1994. Antimicrobial susceptibilities were performed for all isolates and pulsed-field gel electrophoresis for genetic typing of selected strains.

RESULTS

One hundred and twenty-six episodes of bacteremia were identified in 109 patients: 108 Enterococcus faecalis, 13 Enterococcus faecium, four both E faecalis and E faecium, and one Enterococcus durans. Enterococcal isolates occurred with polymicrobial bacteremia in 62 (49%) episodes. The most common sites of infection were central venous catheters (45%) and the urinary tract (21%). Enterococcal bacteremia was usually nosocomially acquired (88%), and associated with older age, instrumentation, and prior or current antimicrobial therapy. Overall mortality was 22%, and 7.2% was partially or fully attributable to enterococcal bacteremia. Resistance to ampicillin, high level gentamicin and high level streptomycin were 0%, 32% and 31% for E faecalis, respectively, and 44%, 0% and 47% for E faecium, respectively.

CONCLUSIONS

During this review, the frequency and impact of enterococcal bacteremia at this institution was relatively limited. Isolates resistant to ampicillin and aminoglycosides were emerging, but differences in patient outcomes were similar for resistant and susceptible isolates.

Enterococcal bacteremia in children: a review of seventy-five episodes in a pediatric hospital

BACKGROUND

Enterococcal bacteremia is being increasingly reported. Although there have been a number of recent studies of enterococcal bacteremia in adults, there are few studies involving children. We carried out a prospective study to determine the epidemiologic, clinical and laboratory characteristics of such bacteremia in children.

METHODS

Clinical and microbiologic data were recorded prospectively for all episodes of enterococcal bacteremia occurring during a 3-year period between January 1, 1995, and December 31, 1997.

RESULTS

Seventy-five episodes of enterococcal bacteremia occurring in children at our institution during a 3-year period were prospectively analyzed. Serious underlying disease was present in 67 (89.3%) episodes, and in 48 (64.%) episodes patients had received antibiotics during the 2 weeks preceding enterococcal bacteremia. Forty-seven (62.7%) episodes were nosocomial in origin and 26 (34.7%) were polymicrobial. Fifty (66.7%) episodes occurred in children 1 year old or less. A source of bacteremia was identified in 33 (44%) episodes, intravascular device being the most common identifiable source. Of the 73 isolates identified to species level, there were 36 Enterococcus faecium, 36 Enterococcus faecalis and one Enterococcus avium. In 60 (80%) episodes appropriate anti-enterococcal therapy was given. The overall mortality rate was 7.5%. Four clinical patterns of infection were identified: self-limited bacteremia, 16.0%; low grade sepsis with a favorable outcome after specific therapy, 65.3%; severe and prolonged infection associated with a high mortality rate, 14.7%; and fulminant neonatal sepsis in previously healthy babies, 4.0%.

CONCLUSION

Enterococcal bacteremia in children comprises a heterogeneous group. Bacteremias that are mild and self-limited and respond promptly to antibiotic therapy appear to be more common in children.

In vitro activities of 15 antimicrobial agents against clinical isolates of South African enterococci

The activities of a panel of currently available antibiotics and the investigational agents LY 333328, linezolid, CL 331,002, CL 329,998, moxifloxacin (BAY 12-8039), trovafloxacin, and quinupristin-dalfopristin against 274 clinical isolates of enterococci were determined. No vancomycin resistance or beta-lactamase production was observed. Except for 12 isolates (all non-Enterococcus faecalis) showing reduced susceptibility to quinupristin-dalfopristin (MIC, >/=4 microg/ml), the new agents exhibited promising in vitro antienterococcal activity.

Comparison of risk factors and outcome in patients with Enterococcus faecalis vs Enterococcus faecium bacteraemia

The purpose of our study was to determine retrospectively the risk factors for the acquisition of Enterococcus faecalis vs E. faecium bacteraemia, as well as the clinical outcomes of these patients. 62 patients with Enterococcus faecalis bacteraemia were compared to 31 patients with E. faecium bacteraemia. Haematologic malignancies, neutropenia, high-risk source and previous use of aminoglycosides, carbapenems, cephalosporins and clindamycin were significantly associated with E. faecium bacteraemia. Instead, urinary catheterization was found to be related to Enterococcus faecalis bacteraemia. The mortality rates within 7 d and 30 d were 13% and 27%, respectively, in patients with E. faecalis bacteraemia and 6% and 29%, respectively, in patients with E. faecium bacteraemia. There was no difference in mortality between E. faecalis and E. faecium bacteraemia, nor was there a difference in seriousness of disease at the time of bacteraemia. In the subgroups of patients with monomicrobial or clinically significant E. faecalis vs E. faecium bacteraemia, the mortality rates were similar to the results of all subjects. Our results do not support the theory that E. faecium would be a more virulent organism than E. faecalis.

Avoparcin, a glycopeptide used in animal foods: antimicrobial spectrum and potency tested against human isolates from the United States

Avoparcin is a glycopeptide antimicrobial that is widely used as a growth promoter in animal feeds in portions of Western Europe. Recently, concern has emerged about the possible contribution of avoparcin use to the emergence of glycopeptide resistance in enterococci. Relatively little information exists on the spectrum of activity and potency of avoparcin. We studied the activity of avoparcin compared to vancomycin, teicoplanin, and 3 other antimicrobials against 814 recent human clinical isolates, including Staphylococcus spp. (240 strains), Streptococcus spp. (90 strains), and Enterococcus spp. (60 strains), using reference susceptibility test methods. Our results indicate that avoparcin was less potent than either vancomycin or teichoplanin against staphylococci (MIC50, 4 micrograms/ mL). There was a good correlation of avoparcin MICs with the MICs for vancomycin and teichoplanin for most species; however, the avoparcin MICs for Enterococcus spp. of the vanB phenotype were quite variable (MIC range, 2 to > 16 micrograms/mL). For Staphylococcus haemolyticus, high avoparcin MICs (> or = 16 micrograms/mL) were associated with oxacillin resistance. These results are relevant to the debate concerning the appropriateness of continued use of avoparcin as a growth promoter in animal husbandry. In particular, avoparcin as a glycopeptide with limited potency against some staphylococci seems to represent a theoretically greater risk for selecting glycopeptide resistance among staphylococci, but may not represent any greater threat for the selection of resistance in enterococci.

Clinical and epidemiological significance of enterococci intrinsically resistant to vancomycin (possessing the vanC genotype)

Constitutive low-level vancomycin resistance is found intrinsically in certain enterococcal species and is encoded by vanC ligase genes. These intrinsically vancomycin-resistant enterococci (VRE) will be referred to as VANC VRE. A prospective study to determine the clinical and epidemiologic significance of VANC VRE was conducted. VANC VRE were recovered from the stools of 34 of 601 (5.7%) patients, a rate similar to that obtained for the stools of 100 outpatients in the community (5%). VANC VRE were also isolated from the nonstool specimens of 9 of 538 patients (1.7%), including two patients with bacteremia. No VRE of the vanA or vanB genotypes were detected in nonstool specimens. Eighty-two hospital contacts of the first 23 patients found to be colonized or infected with VANC VRE were screened, and 6 contacts were found to be gastrointestinal carriers of VANC VRE. However, typing of isolates from these 6 contacts by pulsed-field gel electrophoresis with SmaI showed the isolates to be unique and different from those recovered from the index patients. In fact, all VANC VRE isolates from different patients in this study were unique. A case-control study with patients who were negative when screened for VANC VRE as controls failed to identify any risk factor associated with colonization or infection with this organism. VANC VRE were infrequently recovered from clinical specimens but were occasionally found as part of the normal stool flora. Since no transmission between patients was documented, additional isolation procedures may not be necessary for patients colonized or infected with VANC VRE.

Vancomycin-resistant enterococci

OBJECTIVE

To review vancomycin resistance in enterococci (Enterococcus faecalis and Enterococcus faecium) with respect to history, epidemiology, mechanism of resistance, and management.

DATA SOURCES

A MEDLINE, IDIS, and current journal search of English-language articles on vancomycin-resistant enterococci (VRE) published between 1982 and 1994 was conducted.

STUDY SELECTION

Studies and reports pertaining to vancomycin-resistant E. faecalis and E. faecium were evaluated. Case reports, cohort, epidemiologic, in vitro and in vivo studies were evaluated.

DATA EXTRACTION

Reports in which vancomycin minimum inhibitory concentrations were 32 micrograms/mL or more were evaluated.

DATA SYNTHESIS

Large outbreaks of VRE infection have occurred as a result of nosocomial spread. Such outbreaks have required intensive infection control procedures to limit the spread of VRE. Vancomycin resistance in E. faecalis and E. faecium has been subdivided into phenotypes, VanA and VanB. The mechanism of vancomycin resistance is caused by the production of depsipeptide D-Ala-D-Lac, which replaces D-Ala-D-Ala in the peptidoglycan pathway, thereby preventing the binding of vancomycin to D-Ala-D-Ala in the peptidoglycan cell wall. The vanA gene is associated with a transpositional element (Tn1546) that can be transferred via conjugation while most data suggest that vanB has an endogenous origin. Education, aggressive infection control practices. surveillance programs, and appropriate use of vancomycin are necessary to respond to the VRE problem.

CONCLUSIONS

The prevalence of VRE has increased significantly in recent years and has become a worldwide problem. Several factors, such as prior exposure to vancomycin and antibotics (e.g., cephalosporins, antianaerobic agents), physical location in the hospital, immunosuppression, prolonged hospital stay, and VRE gastrointestinal colonization are associated with VRE infection and colonization. Antibiotic treatment of serious VRE infection depends on the phenotype. Optimal treatment of the VanA phenotype is unknown; the VanB phenotype may be treated with teicoplanin and an aminoglycoside.

Emerging resistance to antimicrobial agents in gram-positive bacteria. Enterococci, staphylococci and nonpneumococcal streptococci

Staphylococci (Staphylococcus aureus and coagulase-negative Staphylococcus species) and enterococci are the aetiological organisms in 47 to 52% of nosocomial blood stream infections and approximately 30% of all nosocomial infections in the US. In European intensive care units, almost half of all infections are attributed to staphylococci. The streptococci have also become increasingly important because of the modified virulence of Streptococcus pyogenes strains, and the emerging role of the viridans group streptococci as a cause of potentially fatal bacteraemia in the neutropenic host. Resistance to available antimicrobial agents is increasing and includes, in particular, resistance to the glycopeptides (vancomycin and teicoplanin) amongst enterococci, resistance to penicillinase-resistant penicillins (oxacillin and methicillin) and fluoroquinolones (ciprofloxacin and ofloxacin) amongst staphylococci, and resistance to penicillin and some other beta-lactams amongst viridans group streptococci. New compounds for effective therapy of infection with antimicrobial-resistant Gram-positive species are needed urgently. To this end, the streptogramin combinations [quinupristin/dalfopristin (RP 59500; Synercid)], everninomycin derivatives (SCH 27899), oxazolidinones (U-100572, U-100766) and several newer fluoroquinolones (clinafloxacin, DU 6859a, grepafloxacin, levofloxacin, sparfloxacin, trovafloxacin) are under rapid development and clinical investigation.