Vancomycin-resistant Enterococcus faecium shunt infection in an infant: an antibiotic cure

First Confirmed Case of Vancomycin-ResistantEnterococcus faeciumMeningitis in Turkey:

Vancomycin-resistant enterococci are unusual etiologic agents of bacterial meningitis and pose significant therapeutic difficulties. We report the first confirmed case of nosocomial vancomycin-resistant Enterococcus faecium meningitis in Turkey. The patient was treated with chloramphenicol and cerebrospinal fluid cultures became negative, but clinical success was not achieved. We also review the previously reported cases of vancomycin-resistant Enterococcus faecium meningitis.

Vancomycin-resistant enterococcal meningitis treated with intrathecal streptomycin

Enterococcal meningitis is a rare complication of neurosurgical procedures. We present a patient who developed vancomycin-resistant enterococcal ventriculitis - meningitis after a brain tumor resection and ventriculoperitoneal shunt placement, treated successfully with intrathecal streptomycin through bilateral cerebrospinal fluid drainage catheters in addition to systemic antibiotics. This is the first report of such treatment for this resistant organism.

Enterococcal meningitis: a clinical study of 39 cases and review of the literature

To describe the clinical features and outcome of enterococcal meningitis, we retrospectively reviewed the charts of 39 cases seen at 2 tertiary hospitals during a 25 years and collected 101 additional, previously reported cases for review. Among these 140 cases, there were 82 cases (59%) of postoperative meningitis and 58 cases (41%) of spontaneous meningitis. Eighty-six patients (61%) were adults and 54 (39%) were children. Patients with spontaneous meningitis had a higher frequency of community-acquired infection (50% versus 18%; p < 0.01), severe underlying diseases (67% versus 22%; p < 0.01), and associated enterococcal infection (29% versus 8%; p < 0.01) than patients with postoperative meningitis. The clinical presentation was similar in both groups, but patients with spontaneous infection had a higher frequency of bacteremia (58% versus 12%; p < 0.01), and a lower frequency of mixed infection (9% versus 29%; p < 0.01). Spontaneous meningitis in children was associated with a significantly lower frequency of fever, altered mental status, headache, and meningeal signs (p < 0.01), probably explained by the high proportion of neonates in this age-group. Most infections were caused by Enterococcus faecalis, which accounted for 76% of the isolates identified at the species level. Fifteen of the 25 cases due to Enterococcus faecium were produced by vancomycin-resistant strains. Most patients were treated with ampicillin, penicillin, or vancomycin, with or without aminoglycosides, for a median period of 18 days (range, 1-85 d). Overall mortality was 21%. The mortality rate was higher in spontaneous than in postoperative meningitis (33% versus 12%; p < 0.01), but was similar in patients treated with beta-lactams (18%), glycopeptides (14%), or other antibiotics (25%), as well as in patients treated with monotherapy (16%) or combination therapy (22%). An adverse outcome correlated significantly with advanced age, the presence of severe underlying diseases, associated enterococcal infection, bacteremia, septic shock, and the absence of fever at presentation. Shunt removal was associated with a lower mortality. Multivariate analysis showed that the presence of severe underlying diseases was the only prognostic factor associated with mortality (odds ratio = 6.8, 95% confidence intervals = 2.7-17.5, p < 0.01).

Vancomycin-resistant enterococci: a road map on how to prevent the emergence and transmission of antimicrobial resistance

Nosocomial acquisition of microorganisms resistant to multiple antibiotics represents a threat to patient safety. Here we review the mechanisms that have allowed highly resistant strains belonging to the Enterococcus genus to proliferate within our health-care institutions. These mechanisms indicate that decreasing the prevalence of resistant organisms requires active surveillance, adherence to vigorous isolation, hand hygiene and environmental decontamination measures, and effective antibiotic stewardship. We suggest how to tailor such a complex, multidisciplinary program to the needs of a particular health-care setting so as to maximize cost-effectiveness.

Treatment of central nervous system infection by vancomycin-resistant enterococcus faecium

Enterococci are uncommon causes of CNS infection. We describe a case of ventriculitis and Ommaya reservoir infection due to vancomycin-resistant Enterococcus faecium successfully treated with the combination of i.v. quinupristin/dalfopristin and i.v. linezolid. The patient deteriorated after receiving three dosages of intraventricular quinupristin/dalfopristin. He recovered after discontinuation of intraventricular quinupristin/dalfopristin.

Safety and efficacy of quinupristin/dalfopristin for treatment of invasive Gram-positive infections in pediatric patients

BACKGROUND

Antibiotic-resistant Gram-positive pathogens are an increasingly common cause of serious pediatric infections. Although quinupristin/dalfopristin demonstrates favorable activity against resistant Gram-positive pathogens (including many vancomycin-resistant and methicillin-resistant staphylococci), published experience in the pediatric patient population is limited.

METHODS

We retrospectively analyzed data from the global quinupristin/dalfopristin Emergency-Use Program, which enrolled patients with serious Gram-positive infections who had no further therapy options because of resistance to, failure on or intolerance to standard antibiotic treatments. Our subset included safety and efficacy data from pediatric patients (age <18 years). There were no restrictions on underlying diseases, severity of illness or prior/concomitant antimicrobial use.

RESULTS

Between May 1995 and October 1999, 127 pediatric patients with 131 infections were enrolled. Microbiologic confirmation of etiology was available in 124 patients. All patients had 1 or more concomitant conditions, including malignancy and solid organ or bone marrow transplantation. The most frequent causative pathogens were vancomycin-resistant (80%), spp. (7%), methicillin-resistant (6%) and (4%). All but 21 patients received intravenous quinupristin/dalfopristin 7.5 mg/kg every 8 h. The favorable clinical response rate of quinupristin/dalfopristin was 86 of 124 (69%); the favorable microbiologic response rate was 97 of 124 (78%). Eleven patients (8%) had nonvenous adverse events classified as possibly or probably related to quinupristin/dalfopristin.

CONCLUSIONS

Quinupristin/dalfopristin demonstrated favorable response rates and was reasonably well-tolerated in pediatric patients with serious Gram-positive infections unable to receive alternative therapy. In our opinion quinupristin/dalfopristin is a therapeutic option for the management of such infections.

Linezolid treatment of vancomycin-resistant Enterococcus faecium ventriculitis

The successful treatment of a 7-month-old infant with shunt-associated ventriculitis caused by vancomycin-resistant Enterococcus faecium is presented. Linezolid was administered intravenously every 8 h; children have a greater volume of distribution and total body clearance than adults and therefore require more frequent dosing. The patient tolerated the therapy without adverse effects.

Treatment options for vancomycin-resistant enterococcal infections

Serious infection with vancomycin-resistant enterococci (VRE) usually occurs in patients with significantly compromised host defences and serious co-morbidities, and this magnifies the importance of effective antimicrobial treatment. Assessments of antibacterial efficacy against VRE have been hampered by the lack of a comparator treatment arm(s), complex treatment requirements including surgery, and advanced illness-severity associated with a high crude mortality. Treatment options include available agents which don't have a specific VRE approval (chloramphenicol, doxycycline, high-dose ampicillin or ampicillin/sulbactam), and nitrofurantoin (for lower urinary tract infection). The role of antimicrobial combinations that have shown in vitro or animal-model in vivo efficacy has yet to be established. Two novel antimicrobial agents (quinupristin/ dalfopristin and linezolid) have emerged as approved therapeutic options for vancomycin-resistant Enterococcus faecium on the basis of in vitro susceptibility and clinical efficacy from multicentre, pharmaceutical company-sponsored clinical trials. Quinupristin/dalfopristin is a streptogramin, which impairs bacterial protein synthesis at both early peptide chain elongation and late peptide chain extrusion steps. It has bacteriostatic activity against vancomycin-resistant E. faecium [minimum concentration to inhibit growth of 90% of isolates (MIC(90)) = 2 microg/ml] but is not active against Enterococcus faecalis (MIC(90 )= 16 microg/ml). In a noncomparative, nonblind, emergency-use programme in patients who were infected with Gram-positive isolates resistant or refractory to conventional therapy or who were intolerant of conventional therapy, quinupristin/dalfopristin was administered at 7.5 mg/kg every 8 hours. The clinical response rate in the bacteriologically evaluable subset was 70.5%, and a 65.8% overall response (favourable clinical and bacteriological outcome) was observed. Resistance to quinupristin/dalfopristin on therapy was observed in 6/338 (1.8%) of VRE strains. Myalgia/arthralgia was the most frequent treatment-limiting adverse effect. In vitro studies which combine quinupristin/dalfopristin with ampicillin or doxycyline have shown enhanced killing effects against VRE; however, the clinical use of combined therapy remains unestablished. Linezolid, an oxazolidinone compound that acts by inhibiting the bacterial pre-translational initiation complex formation, has bacteriostatic activity against both vancomycin resistant E. faecium (MIC(90) = 2 to 4 microg/ml) and E. faecalis (MIC(90) = 2 to 4 microg/ml). This agent was studied in a similar emergency use protocol for multi-resistant Gram-positive infections. 55 of 133 evaluable patients were infected with VRE. Cure rates for the most common sites were complicated skin and soft tissue 87.5% (7/8), primary bacteraemia 90.9% (10/11), peritonitis 91.7% (11/12), other abdominal/pelvic infections 91.7% (11/12), and catheter-related bacteraemia 100% (9/9). There was an all-site response rate of 92.6% (50/54). In a separate blinded, randomised, multicentre trial for VRE infection at a variety of sites, intravenous low dose linezolid (200mg every 12 hours) was compared to high dose therapy (600 mg every 12 hours) with optional conversion to oral administration. A positive dose response (although statistically nonsignificant) was seen with a 67% (39/58) and 52% (24/46) cure rate in the high- and low-dose groups, respectively. Adverse effects of linezolid therapy have been predominantly gastrointestinal (nausea, vomiting, diarrhoea), headache and taste alteration. Reports of thrombocytopenia appear to be limited to patients receiving somewhat longer courses of treatment (>14 to 21 days). Linezolid resistance (MIC > or = 8 microg/ml) has been reported in a small number of E. faecium strains which appears to be secondary to a base-pair mutation in the genome encoding for the bacterial 23S ribosome binding site. At present a comparative study between the two approved agents for VRE (quinupristin/dalfopristin and linezolid) has not been performed. Several investigational agents are currently in phase II or III trials for VRE infection. This category includes daptomycin (an acidic lipopeptide), oritavancin (LY-333328; a glycopeptide), and tigilcycline (GAR-936; a novel analogue of minocycline). Finally, strategies to suppress or eradicate the VRE intestinal reservoir have been reported for the combination of oral doxycyline plus bacitracin and oral ramoplanin (a novel glycolipodepsipeptide). If successful, a likely application of such an approach is the reduction of VRE infection during high risk periods in high risk patient groups such as the post-chemotherapy neutropenic nadir or early post-solid abdominal organ transplantation.

Meningitis and shunt infection caused by anaerobic bacteria in children

This review describes the microbiology and management of meningitis and shunt infections caused by anaerobic bacteria in children. The predominant anaerobes recovered in meningitis are Bacteriodes spp., Bacteriodes fragilis, Fusobacterium spp., and Clostridium spp. Peptostreptococcus, Veillonella, Actinomyces, Propionibacterium acnes, and Eubacterium are less commonly isolated. The predisposing conditions for meningitis are acute or chronic middle-ear infection, sinusitis, pharyngitis, and pulmonary infections. In newborn and preterm infants the predisposing conditions are rupture of membranes, amnionitis, fetal distress, necrotizing enterocolitis, gastric perforation and subsequent ileus followed by bacteremia, aspiration pneumonitis and septicemia, infected ventriculoperitoneal or ventriculoatrial shunt, and complicating dermal sinus tract infections. Shunt infection with Propionibacterium spp. has been reported in children, especially in association with ventriculoauricular and ventriculoperitoneal shunts. Clostridium perfringens has been recovered from infants with a ventriculoperitoneal shunt. Multiple-organism meningitis was reported as a complication of ventriculoperitoneal and lumboperitoneal shunts that perforated the gastrointestinal tract. Early recognition and effective therapy are essential to recovery. Management of meningitis includes the use of antimicrobials effective against anaerobes that penetrate the blood-brain barrier. These include metronidazole, chloramphenicol, the combination of a penicillin and a beta-lactamase inhibitor, and carbapenems. The treatment of shunt infection includes antimicrobial therapy and removal of the shunt.

Successful treatment of ventriculostomy-related meningitis caused by vancomycin-resistant Enterococcus with intravenous and intraventricular quinupristin/dalfopristin

We report a case of ventriculostomy-related meningitis caused by vancomycin-resistant Enterococcus faecium (VRE). The patient was successfully treated with administration of quinupristin/dalfopristin by both intravenous and intraventricular routes. A brief review of the literature is provided, which indicates that optimal management with quinupristin/dalfopristin should include daily intraventricular doses of at least 2 mg.

Successful treatment of vancomycin-resistant enterococcus meningitis with linezolid: Case report and review of the literature

OBJECTIVE

To describe the successful treatment of a case of vancomycin-resistant enterococcus meningitis with linezolid.

DESIGN

Case report and review of the literature.

PATIENTS

The patient is a 35-yr-old man who suffered a cerebellar hemorrhage after embolization of a cerebellar arteriovenous malformation. The patient underwent ventriculostomy drainage and craniectomy. The patient was on broad-spectrum antibiotics for pneumonia including vancomycin. The patient remained febrile and grew vancomycin-resistant Enterococcus faecium from the cerebrospinal fluid.

INTERVENTIONS

The patient was treated with intravenous chloramphenicol without success. On postoperative day 16, the patient was begun on intravenous linezolid.

MAIN RESULTS

The patient received 4 wks of intravenous linezolid with complete eradication of the meningitis.

CONCLUSIONS

Intravenous linezolid appears to be a safe and effective therapy for vancomycin-resistant enterococcus meningitis.

Vancomycin-resistant Enterococcus faecium meningitis successfully managed with linezolid: case report and review of the literature

Enterococci cause serious illness in immunocompromised patients and severely ill, hospitalized patients. Resistance to vancomycin has increased in frequency during the past few years. Limited therapeutic options are available for vancomycin-resistant enterococcal infections and the optimum therapy has not been established. We report a case of nosocomial vancomycin-resistant Enterococcus faecium meningitis in the setting of hyperinfection with Strongyloides stercoralis that was successfully treated with linezolid. We also review the previously reported cases of vancomycin-resistant E. faecium meningitis.

Cerebrospinal fluid concentrations of quinupristin-dalfopristin in a patient with vancomycin-resistant Enterococcus faecium [correction of faecalis] ventriculitis

A 44-year-old man was treated successfully for vancomycin-resistant Enterococcus faecium (VREF) ventriculitis with intrathecal quinupristin-dalfopristin 1 mg, 2 mg, and 4 mg, and other intravenous antibiotics. Cerebrospinal fluid samples were collected before and after the 1-mg and 2-mg doses to determine the concentrations of quinupristin-dalfopristin and its active metabolites. Concentrations were above the minimum inhibitory concentration for VREF immediately after unclamping the extraventricular drain and were quantifiable for at least 7 hours.

Vancomycin-resistant enterococci

After they were first identified in the mid-1980s, vancomycin-resistant enterococci (VRE) spread rapidly and became a major problem in many institutions both in Europe and the United States. Since VRE have intrinsic resistance to most of the commonly used antibiotics and the ability to acquire resistance to most of the current available antibiotics, either by mutation or by receipt of foreign genetic material, they have a selective advantage over other microorganisms in the intestinal flora and pose a major therapeutic challenge. The possibility of transfer of vancomycin resistance genes to other gram-positive organisms raises significant concerns about the emergence of vancomycin-resistant Staphylococcus aureus. We review VRE, including their history, mechanisms of resistance, epidemiology, control measures, and treatment.

Antienterococcal antibiotics

The treatment of severe enterococcal infections based on the currently available antibacterial agents is difficult. The help of the microbiology laboratory for determining MICs, MBCs, and most effective synergistic combinations is crucial. There is a need for good prospective multicenter clinical trials to improve the prognosis of such infections by defining therapeutic strategies better. Such a requirement is highly suitable for the treatment of infections caused by enterococci exhibiting acquired resistance mechanisms to the available agents. The current clinical development of new compounds looks promising in these persistently life-threatening infections mostly occurring in deficient hosts.

Vancomycin-resistant enterococci

After they were first identified in the mid-1980s, vancomycin-resistant enterococci (VRE) spread rapidly and became a major problem in many institutions both in Europe and the United States. Since VRE have intrinsic resistance to most of the commonly used antibiotics and the ability to acquire resistance to most of the current available antibiotics, either by mutation or by receipt of foreign genetic material, they have a selective advantage over other microorganisms in the intestinal flora and pose a major therapeutic challenge. The possibility of transfer of vancomycin resistance genes to other gram-positive organisms raises significant concerns about the emergence of vancomycin-resistant Staphylococcus aureus. We review VRE, including their history, mechanisms of resistance, epidemiology, control measures, and treatment.

Treatment of a vancomycin-resistant Enterococcus faecium ventricular drain infection with quinupristin/dalfopristin and review of the literature

Central nervous system infections involving vancomycin-resistant Enterococcus faecium (VREF) are infrequently described and pose significant therapeutic difficulties, because these organisms are intrinsically resistant to many antibiotics. We describe the use of intrathecal quinupristin/dalfopristin to treat a VREF-associated infection in a neuro--surgical patient.

Quinupristin/dalfopristin (RP 59500) therapy for vancomycin-resistant Enterococcus faecium aortic graft infection: case report

A 46-year-old woman was admitted to the hospital with severe peripheral vascular disease, requiring multiple vascular surgical procedures. During the sixth hospital week, after prior therapy with multiple antibiotics, Enterococcus faecium was isolated as the only organism from an operating room culture of an infected aortic graft. Histological examination of the graft showed infiltration with polymorphonuclear leukocytes. Subsequently, cultures of an infected inguinal wound yielded Enterococcus faecium with mixed bacterial growth. Both isolates of Enterococcus faecium were resistant to all available antimicrobials, including ampicillin, vancomycin, tetracycline, chloramphenicol, and ciprofloxacin. Compassionate use therapy with quinupristin/dalfopristin (RP59500) was administered for 25 days, the patient's clinical condition improved, and wound healing occurred. Transient elevation of serum alkaline phosphatase was noted. This case demonstrates successful eradication of deep VREF infection by quinupristin/dalfopristin with good tolerance of prolonged therapy.

Quinupristin/dalfopristin: spectrum of activity, pharmacokinetics, and initial clinical experience

In recent years, the prevalence of multiple drug-resistant strains of common Gram-positive pathogens has grown in many regions of the world. Increasingly, methicillin-resistant Staphylococcus aureus, coagulase-negative staphylococci, vancomycin-resistant enterococci, and penicillin-resistant pneumococci have been identified as causative organisms in serious and life-threatening infections. This increase in resistance highlights the need for new antimicrobial agents to expand the therapeutic armamentarium. Quinupristin/dalfopristin is the first of a unique class of antibiotics called streptogramins. It is characterized by a unique mechanism of action, intracellular activity, synergistic activity of its components, broad spectrum of activity against most Gram-positive cocci, common respiratory pathogens, and anaerobes, and demonstrated postantibiotic effect. Clinical evidence to date indicates that quinupristin/dalfopristin may be effective for the treatment of multidrug-resistant infections, especially those due to vancomycin-resistant enterococci and methicillin-resistant staphylococci. This article reviews the pharmacology, microbiology, and clinical experience with quinupristin/dalfopristin to date.

Treatment of vancomycin-resistant Enterococcus faecium infections with an investigational streptogramin antibiotic (quinupristin/dalfopristin): a report of fifteen cases

New therapies for vancomycin-resistant Enterococcus faecium (VREF) infections are urgently needed. We describe the treatment of 15 patients with VREF infection with quinupristin/dalfopristin (RP 59500), a new injectable streptogramin antibiotic. Primary infections treated were bacteremia (4), urinary tract (4), intraabdominal (5), otitis externa (1), and meningitis (1). Minimum inhibitory concentrations for quinupristin/dalfopristin ranged from 0.5 microgram/ml or less to 2 micrograms/ml, and minimum bactericidal concentrations were greater than 64 micrograms/ml for all VREF isolates tested. Peak serum inhibitory titers following infusion of quinupristin/dalfopristin ranged from 1:8 to 1:64; all bactericidal titers were less than 1:2. Development of resistance to quinupristin/dalfopristin during therapy was not observed. The only drug-related adverse effect noted was phlebitis in 4 patients; all had received quinupristin/dalfopristin by peripheral venous infusion. Three patients had clinical and bacteriologic cures. Relapses occurred in 5 patients with recovery of VREF from infected sites in post-treatment cultures. Ten patients died of severe underlying disease; VREF was believed to contribute directly to the death of only 1 patient. While evaluation of clinical efficacy was complicated by the severity of underlying disease in patients with VREF infection, our experience suggests that quinupristin/dalfopristin is a safe and potentially useful agent for the treatment of VREF infections.

Serious infections caused by multiply-resistant Enterococcus faecium

Three liver transplant patients developed serious intraabdominal infections and recurrent bacteremias due to strains of Enterococcus faecium with high-level resistance to vancomycin. The enterococci were also resistant to all other antibacterials except pristinamycin, which, given orally, proved ineffective. One strain was sensitive to tetracycline. Increasingly, clinicians are likely to encounter infections caused by multiply-resistant enterococci, and these cases illustrate the seriousness of such infections in compromised patients.

Persistence of vancomycin-resistant Enterococcus faecium gastrointestinal tract colonization in antibiotic-treated mice

Colonization with vancomycin-resistant Enterococcus faecium (VREF) is strongly associated with previous antimicrobial therapy. The gastrointestinal (GI) tract appears to be the major reservoir for this organism. We used antibiotic-treated Swiss Webster mice to study GI tract colonization with a characterized strain of VREF (E. faecium 228). Mice were pretreated with antibiotics in their daily drinking water and inoculated with 10(9) colony-forming units (CFU) of E. faecium 228 by oral gavage. We were able to establish persistent colonization with high concentrations of E. faecium 228 (> 8.0 log10 CFU/g of feces) in animals treated with 5 mg/ml of streptomycin plus 1 mg/ml of cefotetan. RP 59500, a streptogramin antibiotic with good in vitro activity against VREF, was administered orally in mice (n = 8) colonized with E. faecium 228. After 14 days of treatment VREF was undetectable in feces of all treated mice (< 3.0 CFU/g). Seven days after discontinuation of RP 59500, VREF was present in the feces of all animals. VREF isolates recovered after treatment remained susceptible to RP 59500. Attempts to eradicate E. faecium 228 colonization by oral administration of a vancomycin-sensitive E. faecium strain (SF68) or Lactobacillus spp. were unsuccessful as long as animals continued to receive streptomycin and cefotetan. Recovery of E. faecium 228 from cultures of livers and gallbladders in some animals with persistent GI tract colonization suggests that the organisms may also colonize the hepatobiliary system.

Experience with quinupristin/dalfopristin in treating infections with vancomycin-resistant Enterococcus faecium in children

BACKGROUND

The emergence and spread of vancomycin-resistant Enterococcus faecium (VREF) has presented serious therapeutic difficulties because of the lack of reliably active antibiotics. Quinupristin/dalfopristin is a new injectable streptogramin antibiotic that is active against most strains of VREF. Experience with this agent in adults with VREF infections is well-documented; however, there are few reports of its use in children. We report on eight children with VREF infections who received quinupristin/dalfopristin under a compassionate use protocol.

METHODS

Quinupristin/dalfopristin was administered according to the manufacturer's recommendations. Clinical and laboratory data were recorded for each patient.

RESULTS

The infections treated comprised six cases of bacteremia and two of peritonitis. All patients had serious underlying conditions. Seven patients recovered fully. One patient died, having experienced a relapse of his infection after quinupristin/dalfopristin was discontinued. None of the patients experienced side effects or other adverse events.

CONCLUSION

Quinupristin/dalfopristin was well-tolerated and generally effective in children with infections caused by VREF. There is increasing evidence that it may be more effective than other currently available antibiotics in some such patients.

Quinupristin-Dalfopristin

The incidence of infection with multidrug-resistant or pan-resistant gram-positive bacteria has drastically limited or eliminated the conventional antimicrobial options available to clinicians. Quinupristin-dalfopristin, a unique parenteral streptogramin that lacks cross-resistance with other antimicrobials, has shown clinical efficacy against many of these important bacteria. This review focuses on quinupristin-dalfopristin"s mechanism of action, in vitro spectrum of activity, clinical efficacy and toxicity, and likely future role in the management of serious gram-positive infections.

Quinupristin/dalfopristin: a review of its use in the management of serious gram-positive infections

Quinupristin/dalfopristin is the first parenteral streptogramin antibacterial agent, and is a 30:70 (w/w) ratio of 2 semisynthetic pristinamycin derivatives. The combination has inhibitory activity against a broad range of gram-positive bacteria including methicillin-resistant staphylococci, vancomycin-resistant Enterococcus faecium (VREF), drug-resistant Streptococcus pneumoniae, other streptococci, Clostridium perfringens and Peptostreptococcus spp. The combination also has good activity against selected gram-negative respiratory tract pathogens including Moraxella catarrhalis, Legioniella pneumophila and Mycoplasma pneumoniae. Quinupristin/dalfopristin has poor activity against E. faecalis. The combination is bactericidal against staphylococci and streptococci, although constitutive erythromycin resistance can affect its activity. As for many other agents, quinupristin/dalfopristin is generally bacteriostatic against E. faecium. In patients with methicillin-resistant S. aureus (MRSA) or VREF infections participating in prospective emergency-use trials, quinupristin/dalfopristin 7.5 mg/kg every 8 or 12 hours achieved clinical or bacteriological success in > or =64% of patients. Emergence of resistance to quinupristin/dalfopristin was uncommon (4% of patients) in those with VREF infections. Quinupristin/dalfopristin 7.5 mg/kg 8- or 12-hourly also achieved similar clinical success rates to comparator agents in patients with presumed gram-positive complicated skin and skin structure infections or nosocomial pneumonia (administered in combination with aztreoman) in 3 large multicentre randomised trials. Systemic adverse events associated with quinupristin/dalfopristin include gastrointestinal events (nausea, vomiting and diarrhoea), rash and pruritus. Myalgias and arthralgias also occur at an overall incidence of 1.3%, although higher rates (2.5 to 31%) have been reported in patients with multiple comorbidities. Venous events are common if the drug is administered via a peripheral line; however, several management options (e.g. use of central venous access, increased infusion volume) may help to minimise their occurrence. Hyperbilirubinaemia has been documented in 3.1% of quinupristin/dalfopristin recipients versus 1.3% of recipients of comparator agents. Quinupristin/dalfopristin inhibits cytochrome P450 3A4 and therefore has the potential to increase the plasma concentrations of substrates of this enzyme.

CONCLUSIONS

Quinupristin/dalfopristin, the first parenteral streptogramin, offers a unique spectrum of activity against multidrug-resistant gram-positive bacteria. In serious gram-positive infections for which there are other treatment options available, the spectrum of activity and efficacy of quinupristin/ dalfopristin should be weighed against its tolerability and drug interaction profile. However, in VREF or unresponsive MRSA infections, where few proven treatment options exist, quinupristin/dalfopristin should be considered as a treatment of choice for these seriously ill patients.

Vancomycin-resistant enterococci: recent advances in genetics, epidemiology and therapeutic options

Vancomycin-resistant enterococci (VRE) have gained much attention in the last decade. Currently, there are five known types of vancomycin resistance based on genes encoding ligase enzymes that the organisms use to produce their cell wall precursors, namely, VanA, VanB, VanC, VanD and VanE. An additional unclassified type was discovered in Australia. The basis of resistance among these phenotypes appears to be similar in that the resistant organisms produce peptidoglycan precursors that end in moieties other than D-alanyl-D-alanine, the usual target of vancomycin. The other dipeptide-like termini identified to date include D-alanyl-D-lactate and D-alanyl-D-serine, which have low affinity for glycopeptides. Recent evidence suggests that glycopeptide-producing organisms might be the remote origin of the vancomycin resistance genes. In European countries, avoparcin, a glycopeptide used in farm animals as a growth promoter, has been linked to the occurrence of VRE and occasional common strains have been identified in food products, farm animals, healthy subjects and hospitalized patients. There have been no such reports in the USA where heavy use of vancomycin and use of broad spectrum antibiotics such as cephalosporins have been identified as important risk factors for acquisition of VRE. Transmission within the same or between hospitals has been reported in many countries. Infection control measures and efforts to use antibiotics, particularly vancomycin, more appropriately have been implemented in a number of healthcare facilities with varying degrees of success. Many antibiotics, as a single agent or a combination of drugs, as well as various new antibiotics have been tested in vitro, in animal models, or used in anecdotal cases but clinical data from large comparative trials are not available to date. Because of the limited susceptibility of many VRE to other agents, efforts to control these organisms are particularly important. Copyright 1999 Harcourt Publishers LtdCopyright 1999 Harcourt Publishers Ltd.

Vancomycin-resistant enterococci: the clinical effect of a common nosocomial pathogen

Enterococcus spp. is now the third most common pathogen among hospitalized patients, accounting for nearly 12% of nosocomial infections. Enterococcus faecalis is the most prevalent enterococcal species (85%-89%), whereas Enterococcus faecium accounts for 10%-15% of enterococcal isolates. Only 5% of E. faecalis isolates are resistant to glycopeptides. E. faecium has also been shown to be resistant to nonglycopeptide compounds, such as penicillins (97%), high-level gentamicin (52.1%), and high-level streptomycin (58.3%). Numerous risk factors for vancomycin-resistant enterococci (VRE) have been identified, including as length of hospital- or ICU-stay, proximity to a hospitalized, colonized VRE, patient severity of illness, renal failure, recent surgery, immunosuppression, and organ recipient status. An important risk factor is prior exposure to antibiotics such as vancomycin, ceftazidime, ciprofloxacin, and metronidazole, as well as the number and duration of recent antibiotics. Interventions to reduce nosocomial VRE cross-transmission have also been studied. Using gowns in addition to gloves diminished the incidence of VRE in one study, but had a negligible effect in a second study. Studies have shown that in many cases (> 60%) vancomycin usage is inappropriate. While controlling the use of vancomycin alone has only variably diminished VRE colonization, other efforts such as narrowing the spectrum of antibiotics, antiseptics, and reducing immunosuppression may be salutary. Attempts to eradicate VRE intestinal carriage with enteral agents (bacitracin, tetracycline + rifampin, novobiocin) have been reported but seem to have only a transient effect. Non-antimicrobial interventions such as removal of intravenous or bladder catheters and/or surgical or percutaneous drainage may be beneficial. In addition, the development of new antimicrobial agents such as streptogramins, glycopeptides, everninomicins, and oxazalididones will hopefully play an important role in reducing morbidity from these pathogens.

Clinical implications of nosocomial gram-positive bacteremia and superimposed antimicrobial resistance

The coexistence of a pathogen population with an ever-increasing resistance to many antibiotics and a patient population characterized by increasingly complex clinical problems has contributed to an increase in the bloodstream infections associated with gram-positive bacteria. This serious therapeutic challenge has already been associated with an increase in infection-related morbidity and mortality, a prolongation of hospital stays, and an escalation of healthcare costs. Vancomycin resistance, long prevalent among the enterococci, has emerged in strains of Staphylococcus aureus. Several cases of infection caused by S. aureus strains with intermediate-level resistance to vancomycin (MIC=8 microg/mL) have recently been reported. As glycopeptide resistance accelerates among the gram-positive bacteria, so does the potential for adverse clinical consequences associated with bloodstream infections caused by these pathogens. The patients least able to tolerate the effects of uncontrolled bloodstream infections are also those at the highest risk for the development of infections caused by glycopeptide-resistant pathogens. In this at-risk population, a poor outcome may be anticipated if effective antibiotic therapy is unavailable. Appropriate rationing of vancomycin and other antimicrobial agents that increase the selection of antibiotic-resistant strains of gram-positive bacteria and the rapid development of novel antimicrobial agents with reliable gram-positive activity must be immediate priorities if the threat posed by glycopeptide-resistant gram-positive pathogens is to be countered.

Quinupristin-dalfopristin

Quinupristin-dalfopristin (RP 59500) is an injectable streptogramin antibiotic. It possesses a wide spectrum of activity against Gram-positive bacteria including methicillin-resistant staphylococci, glycopeptide-resistant. Enterococcus faecium and penicillin-resistant pneumococci. Quinupristin-dalfopristin has activity against some anaerobes and selected Gram-negative pathogens. Quinupristin-dalfopristin, by way synergism of between its 2 components, is unaffected by most forms of bacterial resistance. Rare forms of macrolide-lincosamide-streptogramin group B resistance may affect its activity; however, at present the incidence of strains with this type of resistance remains low. Quinupristin-dalfopristin is bactericidal against streptococci and staphylococci but has weak or no bactericidal activity against enterococci. In a compassionate use programme, 67% of 95 evaluable patients with vancomycin-resistant Gram-positive infections or intolerant of vancomycin showed improvement with eradication of infection.

Current perspectives on glycopeptide resistance

In the last 5 years, clinical isolates of gram-positive bacteria with intrinsic or acquired resistance to glycopeptide antibiotics have been encountered increasingly. In many of these isolates, resistance arises from an alteration of the antibiotic target site, with the terminal D-alanyl-D-alanine moiety of peptidoglycan precursors being replaced by groups that do not bind glycopeptides. Although the criteria for defining resistance have been revised frequently, the reliable detection of low-level glycopeptide resistance remains problematic and is influenced by the method chosen. Glycopeptide-resistant enterococci have emerged as a particular problem in hospitals, where in addition to sporadic cases, clusters of infections with evidence of interpatient spread have occurred. Studies using molecular typing methods have implicated colonization of patients, staff carriage, and environmental contamination in the dissemination of these bacteria. Choice of antimicrobial therapy for infections caused by glycopeptide-resistant bacteria may be complicated by resistance to other antibiotics. Severe therapeutic difficulties are being encountered among patients infected with enterococci, with some infections being untreatable with currently available antibiotics.