Treatment of vancomycin-resistant enterococcal infections in the immunocompromised host: quinupristin-dalfopristin in combination with minocycline

In vitro activity of salicylamide derivatives against vancomycin-resistant enterococci

A series of 13 salicylamide derivatives was assessed for antibacterial activity against three isolates of vancomycin-resistant Enterococcus faecalis (VRE) and Enterococcus faecalis ATCC 29212 as a quality standard. The minimum inhibitory concentration was determined by the broth microdilution method with subsequent subcultivation of aliquots to assess minimum bactericidal concentration. The growth kinetics was established by the time-kill assay. Ampicillin, ciprofloxacin, tetracycline and vancomycin were used as the reference antibacterial drugs. Three of the investigated compounds showed strong bacteriostatic activity against VRE (0.199-25 µM) comparable to or more potent than ampicillin and ciprofloxacin. In addition, these compounds were tested for synergistic effect with vancomycin, ciprofloxacin and tetracycline, while 5-chloro-2-hydroxy-N-[4-(trifluoromethyl)phenyl]benzamide showed the highest potency as well as synergistic activity with vancomycin against VRE 368. Screening of the cytotoxicity of the most effective compounds was performed using human monocytic leukemia THP-1 cells, and based on LD₅₀ values, it can be stated that the compounds have insignificant toxicity against human cells.

Vancomycin-Resistant Enterococci: Therapeutic Challenges in the 21st Century

Vancomycin-resistant enterococci are serious health threats due in part to their ability to persist in rugged environments and their propensity to acquire antibiotic resistance determinants. Enterococci have now established a home in our hospitals and possess mechanisms to defeat most currently available antimicrobials. This article reviews the history of the struggle with this pathogen, what is known about the traits associated with its rise in the modern medical environment, and the current understanding of therapeutic approaches in severe infections caused by these microorganisms. As the 21st century progresses, vancomycin-resistant enterococci continue to pose a daunting clinical challenge.

Role of Combination Antimicrobial Therapy for Vancomycin-Resistant Enterococcus faecium Infections: Review of the Current Evidence

Enterococcus species are the second most common cause of nosocomial infections in the United States and are particularly concerning in critically ill patients with preexisting comorbid conditions. Rising resistance to antimicrobials that were historically used as front-line agents for treatment of enterococcal infections, such as ampicillin, vancomycin, and aminoglycosides, further complicates the treatment of these infections. Of particular concern are Enterococcus faecium strains that are associated with the highest rate of vancomycin resistance. The introduction of antimicrobial agents with specific activity against vancomycin-resistant Enterococcus (VRE) faecium including daptomycin, linezolid, quinupristin-dalfopristin, and tigecycline did not completely resolve this clinical dilemma. In this review, the mechanisms of action and resistance to currently available anti-VRE antimicrobial agents including newer agents such as oritavancin and dalbavancin will be presented. In addition, novel combination therapies including β-lactams and fosfomycin, and the promising results from in vitro, animal studies, and clinical experience in the treatment of VRE faecium will be discussed.

Composition and dynamics of the respiratory tract microbiome in intubated patients

BACKGROUND

Lower respiratory tract infection (LRTI) is a major contributor to respiratory failure requiring intubation and mechanical ventilation. LRTI also occurs during mechanical ventilation, increasing the morbidity and mortality of intubated patients. We sought to understand the dynamics of respiratory tract microbiota following intubation and the relationship between microbial community structure and infection.

RESULTS

We enrolled a cohort of 15 subjects with respiratory failure requiring intubation and mechanical ventilation from the medical intensive care unit at an academic medical center. Oropharyngeal (OP) and deep endotracheal (ET) secretions were sampled within 24 h of intubation and every 48-72 h thereafter. Bacterial community profiling was carried out by purifying DNA, PCR amplification of 16S ribosomal RNA (rRNA) gene sequences, deep sequencing, and bioinformatic community analysis. We compared enrolled subjects to a cohort of healthy subjects who had lower respiratory tract sampling by bronchoscopy. In contrast to the diverse upper respiratory tract and lower respiratory tract microbiota found in healthy controls, critically ill subjects had lower initial diversity at both sites. Diversity further diminished over time on the ventilator. In several subjects, the bacterial community was dominated by a single taxon over multiple time points. The clinical diagnosis of LRTI ascertained by chart review correlated with low community diversity and dominance of a single taxon. Dominant taxa matched clinical bacterial cultures where cultures were obtained and positive. In several cases, dominant taxa included bacteria not detected by culture, including Ureaplasma parvum and Enterococcus faecalis.

CONCLUSIONS

Longitudinal analysis of respiratory tract microbiota in critically ill patients provides insight into the pathogenesis and diagnosis of LRTI. 16S rRNA gene sequencing of endotracheal aspirate samples holds promise for expanded pathogen identification.

Optimizing therapy for vancomycin-resistant enterococcal bacteremia in children

PURPOSE OF REVIEW

Uncertainties exist regarding the optimal treatment for vancomycin-resistant enterococcal (VRE) bloodstream infections, particularly in settings in which ampicillin cannot be used.

RECENT FINDINGS

Quinupristin-dalfopristin, linezolid, and daptomycin, all approved between 1999 and 2003, represent the mainstays of therapy for VRE bacteremia, although only linezolid has been specifically approved by the United States Food and Drug Administration for this indication. The main objective of this review is to compare the relative efficacies, dosing strategies, and side-effect profiles of quinupristin-dalfopristin, linezolid, and daptomycin for VRE bacteremia in the pediatric population. A brief description of recently approved broad-spectrum Gram-positive agents that may have a role in the management of VRE bacteremia in upcoming years is also provided.

SUMMARY

Linezolid, despite its bacteriostatic activity against VRE, may be the most versatile of the available drugs. It has activity against both Enterococcus faecalis and E. faecium, can be administered orally, and resistance appears to be less of a concern with linezolid compared with the other agents. Additionally, the results of two recent meta-analyses demonstrate more favorable outcomes with linezolid compared with daptomycin for the treatment of VRE bacteremia. The clinical pharmacokinetics of linezolid have been well described in children. The most notable concern with linezolid, however, is toxicities associated with prolonged use. Until more prospective data are available, we favor linezolid as first-line therapy for the treatment of VRE bacteremia in children.

Enterococcal endocarditis revisited

The Enterococcus species is the third main cause of infective endocarditis (IE) worldwide, and it is gaining relevance, especially among healthcare-associated cases. Patients with enterococcal IE are older and have more comorbidities than other types of IE. Classical treatment options are limited due to the emergence of high-level aminoglycosides resistance (HLAR), vancomycin resistance and multidrug resistance in some cases. Besides, few new antimicrobial alternatives have shown real efficacy, despite some of them being recommended by major guidelines (including linezolid and daptomycin). Ampicillin plus ceftriaxone 2 g iv./12 h is a good option for Enterococcus faecalis IE caused by HLAR strains, but randomized clinical trials are essential to demonstrate its efficacy for non-HLAR EFIE and to compare it with ampicillin plus short-course gentamicin. The main mechanisms of resistance and treatment options are also reviewed for other enterococcal species.

Vancomycin-Resistant Enterococcal Bacteremia Pharmacotherapy

Objective: To review the literature on the pharmacotherapy of bloodstream infections (BSI) caused by vancomycin-resistant enterococci (VRE). Data Sources: A MEDLINE literature search was performed for the period 1946 to May 2014 using the search terms Enterococcus, enterococci, vancomycin-resistant, VRE, bacteremia, and bloodstream infection. References were also identified from selected review articles. Study Selection and Data Extraction: English-language case series, cohort studies, and meta-analyses assessing the options in the pharmacotherapy of VRE BSIs in adult patients were evaluated. Data Synthesis: Studies were identified that utilized linezolid, quinupristin/dalfopristin (Q/D), and daptomycin. In all, 8 comparative retrospective cohort studies, 2 meta-analyses of daptomycin and linezolid, and 3 retrospective comparisons of linezolid and Q/D were included for review. Mortality associated with VRE BSIs was high across studies, and the ability to determine differences in outcomes between agents was confounded by the complex nature of the patients included. Two meta-analyses comparing daptomycin with linezolid for VRE BSIs found modest advantages for linezolid, but these conclusions may be hampered by heterogeneity within the included studies. Conclusions: VRE BSIs remain a difficult-to-treat clinical situation. Differences in toxicity between the agents used to treat it are clear, but therapeutic differences are more difficult to discern. Meta-analyses suggest that a moderate advantage for linezolid over daptomycin may exist, but problems with the nature of studies that they included make definitive conclusions difficult.

Vancomycin-resistant enterococci

Vancomycin-resistant enterococci (VRE) consist mainly of Enterococcus faecalis and E faecium, the latter mostly hospital-acquired. In addition, E gallinarum and E casseliflavus are intrinsically vancomycin-resistant and are community-acquired. VRE have become common in many hospitals throughout the world and, once established, are very difficult to eradicate. VRE are difficult to treat; therefore, infection control measures in hospitals are of prime importance in preventing the establishment of these pathogens. Most severe VRE infections will need combination therapy because many of the effective antimicrobial agents, when used alone, have only a bacteriostatic effect.

Antimicrobial treatment of febrile neutropenia: pharmacokinetic-pharmacodynamic considerations

Patients with cancer or hematologic diseases are particularly at risk of infection leading to high morbidity, mortality and costs. Extensive data show that optimization of the administration of antimicrobials according to their pharmacokinetic and pharmacodynamic parameters improves clinical outcome. Evidence is growing that when pharmacokinetic and pharmacodynamic parameters are used to target not only clinical cure but also eradication, the selection resistance is also contained. This is of particular importance in patients with neutropenia in whom increasing rates of drug-resistant Gram-negative bacteria have been reported, particularly Pseudomonas aeruginosa. Based on experimental and clinical studies, pharmacokinetic and pharmacodynamic parameters are discussed in this review for each antibiotic used in febrile neutropenia in order to help physicians improve dosing and optimization of antimicrobial agents.

Targeted therapy against multi-resistant bacteria in leukemic and hematopoietic stem cell transplant recipients: guidelines of the 4th European Conference on Infections in Leukemia (ECIL-4, 2011)

The detection of multi-resistant bacterial pathogens, particularly those to carbapenemases, in leukemic and stem cell transplant patients forces the use of old or non-conventional agents as the only remaining treatment options. These include colistin/polymyxin B, tigecycline, fosfomycin and various anti-gram-positive agents. Data on the use of these agents in leukemic patients are scanty, with only linezolid subjected to formal trials. The Expert Group of the 4(th) European Conference on Infections in Leukemia has developed guidelines for their use in these patient populations. Targeted therapy should be based on (i) in vitro susceptibility data, (ii) knowledge of the best treatment option against the particular species or phenotype of bacteria, (iii) pharmacokinetic/pharmacodynamic data, and (iv) careful assessment of the risk-benefit balance. For infections due to resistant Gram-negative bacteria, these agents should be preferably used in combination with other agents that remain active in vitro, because of suboptimal efficacy (e.g., tigecycline) and the risk of emergent resistance (e.g., fosfomycin). The paucity of new antibacterial drugs in the near future should lead us to limit the use of these drugs to situations where no alternative exists.

Tigecycline use in cancer patients with serious infections: a report on 110 cases from a single institution

Tigecycline, the first in a new class of glycylcyclines, has been approved for the treatment of complicated skin and skin structure and intraabdominal infections in adults. However, clinical data on its safety and effectiveness in cancer patients are lacking. We reviewed the records of all cancer patients treated with tigecycline for more than 48 hours between June 2005 and September 2006 at our institution and identified 110 consecutive cases (median age, 58 yr; range, 18-81 yr). We collected data on demographics, cancer type, tigecycline indication, microbiologic characteristics, side effects, and outcome. Sixty-four (58%) patients had hematologic malignancies; 27 patients had undergone hematopoietic stem cell transplantation. Thirty-one (28%) patients had neutropenia, and 62 (56%) were in the intensive care unit at the start of therapy. Most patients (106 [96%]) received tigecycline as a second-line agent (after not responding to other broad-spectrum antibiotics), and 101 (92%) received it in combination with an antipseudomonal drug. The mean duration of therapy was 11 days (range, 3-35 d). Sixty-six (60%) patients received tigecycline for refractory pneumonia, 19 (17%) had bacteremia, 9 (8%) had intraabdominal infections, and 7 (6%) had complicated skin and soft tissue infections. Fifty (45%) patients had microbiologically documented infections, and the remaining patients had negative cultures at the start of therapy.An overall clinical response was noted in 70 (64%) patients. More clinical responses were seen in patients with bacteremia than in those with pneumonia (79% vs. 51%; p = 0.029). Patients with microbiologically documented infections had significantly higher clinical response rates than patients with non-microbiologically documented infections (73% vs. 55%; p = 0.047). Forty (36%) patients did not respond to treatment; 36 of these patients died of active infection during tigecycline therapy. Patients with pneumonia had a significantly higher mortality rate than patients with bacteremia (44% vs. 16%; p = 0.026). During the 60 days of follow-up from the date of clinical response, patients with pneumonia had significantly shorter survival durations than patients with other infections. Of the 42 patients who were not on antiemetics or ventilator support at the start of tigecycline therapy, 2 (5%) experienced mild nausea, and 1 (2%) experienced nausea and vomiting. Only 4 (4%) patients overall experienced diarrhea during tigecycline therapy, all of whose stools were negative for Clostridium difficile toxin. No serious adverse events related to tigecycline use were identified. The combination of tigecycline and an antipseudomonal drug may be appropriate for treating refractory infections and multidrug-resistant organisms in cancer patients, including hematopoietic stem cell transplant recipients. Patients with refractory pneumonia had a relatively low clinical response rate in our study.

Antimicrobial activity of mupirocin, daptomycin, linezolid, quinupristin/dalfopristin and tigecycline against vancomycin-resistant enterococci (VRE) from clinical isolates in Korea (1998 and 2005)

It is a hot clinical issue whether newly approved antimicrobial agents such as daptomycin, linezolid, quinupristin/dalfopristin (synercid) and tigecycline are active enough to be used for infections caused by vancomycin resistant bacteria. We performed susceptibility tests for mupirocin, which is in widespread clinical use in Korea, and four new antimicrobials, daptomycin, linezolid, quinupristin/dalfopristin and tigecycline, against vancomycin-resistant Enterococcus faecalis and Enterococcus faecium isolated from Korean patients in 1998 and 2005 to evaluate and compare the in vitro activity of these antimicrobials. Among these agents, quinupristin/dalfopristin, which is rarely used in hospitals in Korea, showed relatively high resistance to several vancomycin-resistant enterococci (VRE) isolated in 2005. Likewise, daptomycin, linezolid and tigecycline have not yet been in clinical use in Korea. However, our results showed that most of the 2005 VRE isolates were already resistant to linezolid and daptomycin (highest minimum inhibitory concentration (MIC) value >100 microg/ml). Compared with the other four antimicrobial agents tested in this study, tigecycline generally showed the greatest activity against VRE. However, four strains of 2005 isolates exhibited resistance against tigecycline (MIC >12.5 microg/ml). Almost all VRE were resistant to mupirocin, whereas all E. faecium isolated in 1998 were inhibited at concentrations between 0.8 to approximately 1.6 microg/ml. In conclusion, resistances to these new antimicrobial agents were exhibited in most of VRE strains even though these new antibiotics have been rarely used in Korean hospitals.

Vancomycin-resistant Enterococcus faecium: catheter colonization, esp gene, and decreased susceptibility to antibiotics in biofilm

To evaluate the molecular characteristics and antibiotic susceptibility in biofilm of vancomycin-resistant Enterococcus faecium (VREF) organisms that had caused catheter-related VREF bacteremia (VREF-CRB), we compared 22 isolates causing bacteremia obtained from patients with VREF-CRB with 30 isolates from control patients with gastrointestinal colonization by VREF. Using pulsed-field gel electrophoresis, we identified 17 unique strains among the 22 VREF-CRB isolates and 23 strains among the gastrointestinal isolates. The esp gene was detected in 53% (9 of 17) of the VREF-CRB and 61% (14 of 23) of the control strains (P = 0.6). VREF-CRB produced heavier biofilm colonization of silicone disks than did control organisms (P < 0.001). Daptomycin, minocycline, and quinupristin-dalfopristin were each independently more active than linezolid in reducing biofilm colonization by VREF-CRB (P < 0.01), with daptomycin being the most active, followed by minocycline. In conclusion, the esp gene in VREF is not associated with heavy biofilm colonization or catheter-related bacteremia. In biofilm, daptomycin and minocycline were the most active antibiotics against VREF, and linezolid was the least active.

Comparative in vitro activities of daptomycin, linezolid, and quinupristin/dalfopristin against Gram-positive bacterial isolates from a large cancer center

Our objective was to evaluate and compare the in vitro activity of daptomycin, linezolid, and quinupristin/dalfopristin against clinical bloodstream isolates of Gram-positive pathogens from a large cancer center in the Northeastern United States. Minimum inhibitory concentrations (MICs) were determined for daptomycin, quinupristin/dalfopristin, and linezolid against 258 isolates; bactericidal activity was evaluated using time-kill experiments against 14 representative pathogens. Vancomycin-resistant enterococci represented the largest proportion of bacteria tested (32% of the isolates), followed by methicillin-resistant coagulase-negative staphylococci (23%), and vancomycin sensitive enterococci (14%). Against staphylococci, the MIC90 was 1 microg/mL for both daptomycin and quinupristin/dalfopristin and 4 microg/mL for linezolid. Against enterococci, the MIC90 for both daptomycin and linezolid was 4 microg/mL and was 16 microg/mL for quinupristin/dalfopristin. The quinupristin/dalfopristin MIC90 for Enterococcus faecium was 2 microg/mL. Two enterococci were linezolid resistant and remained susceptible to daptomycin. In vitro time-kill studies found daptomycin to be rapidly bactericidal against the majority of organisms tested, killing 99.9% of bacteria within 6 h. Quinupristin/dalfopristin was bactericidal against staphylococci and bacteriostatic against most enterococci. Linezolid was bacteriostatic against all organisms evaluated. Daptomycin, quinupristin/dalfopristin, and linezolid each demonstrated in vitro activity against this collection of organisms. Future clinical studies to evaluate a potential role for these agents in the management of infections in cancer patients, including the treatment of febrile neutropenia, appear warranted.

In vitro antibacterial activity of echinomycin and a novel analogue, YK2000, against vancomycin-resistant enterococci

The in vitro inhibitory and bactericidal activity of echinomycin and its the novel synthetic analogues of echinomycin,YK2000 and YK2005, were evaluated using 93 clinical isolates of vancomycin-resistant enterococci (VRE). In agar dilution tests, the MIC(90) of echinomycin and YK2000 were 0.125 and 8 mg/l, respectively, using Mueller-Hinton II agar, while that of YK2005 was 32 mg/l. Bactericidal activity of echinomycin and YK2000 were two to four times higher than the MIC in time-kill assay experiments. These results suggest that echinomycin and its analogues might be useful as anti-VRE drugs.

Clinical-use-associated decrease in susceptibility of vancomycin-resistant Enterococcus faecium to linezolid: a comparison with quinupristin-dalfopristin

The susceptibility of 135 vancomycin-resistant Enterococcus faecium bacteremic isolates to linezolid and quinupristin-dalfopristin was determined. All were susceptible to linezolid, while 88% were susceptible to quinupristin-dalfopristin prior to the clinical use of the drugs at our hospital. More than 6 months after their clinical use, a decrease in susceptibility was noted for only linezolid at 83%. This was related in part to a single G2576U gene mutation in domain V of the 23S rRNA gene.

Antibiotic-coated hemodialysis catheters for the prevention of vascular catheter-related infections: a prospective, randomized study

PURPOSE

To determine the efficacy of minocycline-rifampin-coated hemodialysis catheters in reducing catheter-related infections in patients requiring hemodialysis for acute renal failure.

METHODS

Between May 2000 and March 2002, 66 patients were randomly assigned to receive a minocycline-rifampin-impregnated central venous catheter and 64 were randomly assigned to receive an unimpregnated catheter. Patients were followed prospectively until the catheter was removed. Catheter-related infection was determined through quantitative catheter cultures, quantitative blood cultures, or both.

RESULTS

Both groups of patients were similar in age, sex, underlying disease, type of dialysis (continuous vs. intermittent), neutropenia during catheterization and its duration, catheter insertion difficulties, and administration of blood products or medication. The mean (+/- SD) catheter dwell time was the same in both groups (8 +/- 6 days, P = 0.7). There were seven catheter-related infections (11%), all associated with the use of unimpregnated catheters. Kaplan-Meier estimates for the risk of catheter-related infection showed that coated catheters were less likely to be associated with infection (P = 0.006).

CONCLUSION

The use of polyurethane hemodialysis catheters impregnated with minocycline and rifampin decreases the risk of catheter-related infection in patients with acute renal failure.

Safety, efficacy and pharmacokinetics of linezolid for treatment of resistant Gram-positive infections in cancer patients with neutropenia

BACKGROUND

Linezolid is a recently approved oxazalidinone with extended activity against Gram-positive bacteria. We evaluated the results of linezolid therapy in neutropenic cancer patients with Gram-positive bacterial infections from a compassionate-use program.

PATIENTS AND METHODS

This was a prospective, multicenter, open-label, non-comparative, non-randomized compassionate-use treatment program in patients with serious Gram-positive infections. To qualify for enrollment patients were required to have an infection resistant to available antimicrobial agents, or in whom available agents had failed or to which they were intolerant. Patients with absolute neutrophil counts (ANC) <500 cells/mm(3) or <1000 cells/mm(3) and expected to decrease to <500 cells/mm(3), and who received linezolid 600 mg twice daily were included. Plasma samples for population pharmacokinetic analysis were collected. Clinical and microbiological assessments of outcomes were made at the end of therapy and at short-term follow-up.

RESULTS

Of the patients in the compassionate-use trial, 103 were neutropenic. The mean [standard deviation (SD)] age was 50.1 (17.5) years, 47% were female, and 47.6% had a baseline ANC </=100 cells/mm(3). The mean (SD) duration of linezolid therapy was 14.6 (11.4) days. The most common site of infection was the bloodstream (90.3%), and the most commonly identified pathogen was vancomycin-resistant Enterococcus faecium (83%). A total of 83 (80.5%) and 52 (50.4%) patients were evaluable for clinical and microbiological outcomes at the end of therapy, respectively. Clinical and microbiological cure rates in the evaluable patients were 79% and 86%, respectively. Linezolid was well-tolerated in this patient population, with an overall adverse event rate of 17.5%; 5% of patients required discontinuation of the drug due to side-effects. The pharmacokinetics of linezolid in patients with neutropenia did not differ from the overall compassionate-use population.

CONCLUSIONS

Linezolid was safe and effective in treating resistant Gram-positive infections in neutropenic cancer patients. Comparative clinical trials to evaluate further the effectiveness and safety of linezolid in this patient population are warranted.

Quinupristin-dalfopristin and linezolid: evidence and opinion

Quinupristin-dalfopristin and linezolid demonstrate in vitro activity against a wide range of gram-positive bacteria, including many isolates resistant to earlier antimicrobials. Quinupristin-dalfopristin is inactive against Enterococcus faecalis but has been effective for treatment of infections due to vancomycin-resistant Enterococcus faecium associated with bacteremia. In comparative trials, linezolid proved to be equivalent to comparator agents, resulting in its approval for several clinical indications. The almost-complete bioavailability of linezolid permits oral administration. Each agent can cause adverse effects that may limit use in individual patients. Resistance to these drugs has been encountered infrequently among vancomycin-resistant E. faecium. Resistance to quinupristin-dalfopristin is rare among staphylococci in the United States, and resistance to linezolid is very rare. Whether there is any benefit to use of these agents in combination regimens, and whether there are circumstances in which they might be alternatives to cell-wall active antibiotics for treatment of bone or endovascular infections, are questions that deserve further study.

Risk factors for arthralgias or myalgias associated with quinupristin-dalfopristin therapy

STUDY OBJECTIVE

To evaluate risk factors for the development of arthralgias or myalgias associated with quinupristin-dalfopristin.

DESIGN

Retrospective chart review and case-control analysis.

SETTING

An 850-bed tertiary care medical center.

PATIENTS

All adult and pediatric patients who had received quinupristin-dalfopristin through either a compassionate-use protocol (February 1996-October 1999) or in the year after quinupristin-dalfopristin was added to the hospital formulary (November 1999-October 2000) were included in this study. Case patients were those who developed arthralgias or myalgias while receiving quinupristin-dalfopristin therapy; control patients were those who received quinupristin-dalfopristin but did not develop arthralgias or myalgias.

INTERVENTION

Medical records, pharmacy dispensing information, and microbiology data were reviewed by a physician and a pharmacist, both of whom specialized in infectious diseases. Presence or absence of arthralgias or myalgias was the primary outcome assessed.

MEASUREMENTS AND MAIN RESULTS

Quinupristin-dalfopristin was administered to 68 patients during the period defined by the study. Arthralgias and myalgias could not be assessed in 18 of the 68 patients because they were sedated and paralyzed, or they were young children who could not communicate the presence of pain. Univariate analysis demonstrated that significant risk factors for arthralgias or myalgias associated with quinupristin-dalfopristin were female sex, chronic liver disease, receipt of liver transplant, elevated bilirubin level at baseline, major surgery, and receipt of either mycophenolate or cyclosporine. Multivariate analysis demonstrated a strong association with chronic liver disease, receipt of liver transplant, elevated bilirubin level at baseline, and receipt of either cyclosporine or mycophenolate. Of 50 evaluable patients receiving quinupristin-dalfopristin, 25 had pain that may have been associated with this antimicrobial agent.

CONCLUSION

The mechanism for development of arthralgias or myalgias associated with quinupristin-dalfopristin remains unknown, but these adverse events are more likely to occur in patients with chronic liver disease and those who have received a liver transplant or are receiving cyclosporine or mycophenolate.