Emanuel N. Vergis

Determinants of Vancomycin Resistance and Mortality Rates in Enterococcal Bacteremia: A Prospective Multicenter Study

Enterococcus species have become increasingly prominent as etiologic agents of nosocomial bacteremia (19). Enterococcal bacteremia has a mortality rate of 42% to 73% (10, 11) and is common among debilitated patients and those with severe underlying illnesses (5, 6, 1217). Enterococci have low-level resistance to penicillins, aminoglycosides, and clindamycin and are intrinsically resistant to cephalosporins. Enterococci may acquire resistance to additional antibiotics, including -lactams, aminoglycosides, and glycopeptides (18). Resistance to multiple antibiotics, in particular vancomycin coupled with high-level ampicillin and aminoglycoside, has been reported with increasing frequency (19). At present, more than 20% of enterococci isolated from intensive care units exhibit vancomycin resistance. The addition of vancomycin resistance to high-level ampicillin and aminoglycoside resistance limits available therapeutic options (20). To investigate the clinical implications of antibiotic resistance in enterococci, we instituted a prospective, multicenter observational study of outcome in patients with enterococcal bacteremia. We sought to determine 1) factors associated with infection with vancomycin-resistant enterococci [VRE], 2) factors predictive of death in patients with enterococcal bacteremia, 3) the effect of vancomycin resistance on mortality rates, and 4) the effect of antibiotic therapy on outcome. Methods All patients with enterococcal bacteremia were hospitalized at the University of Pittsburgh Medical Center and the Veterans Affairs (VA) Medical Center (Pittsburgh, Pennsylvania), Detroit Medical Center and John D. Dingell VA Medical Center (Detroit, Michigan), Rush-Presbyterian-St. Lukes Medical Center (Chicago, Illinois), New England Medical Center (Boston, Massachusetts), and William Beaumont Hospital (Royal Oak, Michigan). Clinical data were obtained from review of medical records. The institutional review boards of four participating institutions approved the study. At the fifth institution, the study was considered exempt from review because it involved confidential use of existing records and bacterial isolates. Microbiology Blood for culture was obtained by venipuncture or through central venous catheters. Enterococcal species were determined by using either VITEK (bioMerieux Vitek, Inc., Hazelwood, Missouri) or MicroScan (MicroScan, Inc., West Sacramento, California) systems according to the manufacturers recommendations. Identification of species other than E. faecalis and E. faecium was confirmed as reported elsewhere (21). One of the authors standardized antimicrobial susceptibilities by using Etest strips (AB BIODISK North America, Inc., Piscataway, New Jersey). Enterococcus faecium isolates showing resistance or intermediate susceptibility to quinupristindalfopristin were tested by broth microdilution and disk diffusion to confirm reduced susceptibility. If the isolate was unavailable, antimicrobial susceptibilities reported by the submitting microbiology laboratories were used. Minimum inhibitory concentration (MIC) breakpoints from the Ninth National Committee for Clinical Laboratory Standards (NCCLS) were used (22). Because imipenem MIC values for enterococci are not defined, NCCLS breakpoints for Enterobacteriaceae were used (22). Quality control was monitored by using E. faecalis American Type Culture Collection (ATCC) 29212. Nine enterococcal isolates displayed intermediate susceptibility to vancomycin (MIC, 8 to 16 g/mL) but were considered resistant for the purposes of analysis. Vancomycin resistance genotypes of selected clinical isolates were determined by using polymerase chain reaction (PCR) amplification with primers specific for intragenic sequences of the vanA and vanB genes (23, 24). Control strains included vancomycin-susceptible E. faecalis ATCC 29212, E. faecium BM4147 (vanA) (25), and E. faecalis V583 (vanB) (26). For determination of aminoglycoside resistance genes, genomic DNA for PCR amplification was prepared with the InstaGene Matrix kit (BioRad Laboratories, Hercules, California) and PCR performed as reported elsewhere (27). Aminoglycoside resistance genes detected included aac(6)-Ie-aph(2)-Ia (28), aph(2)-Ic (29), aph(2)-Id (30), and aph(2)-Ib (31). Definitions Clinically significant bacteremia was defined as isolation of enterococci in two or more separately obtained blood cultures or from a single blood culture and from a concomitant site of infection in a clinical scenario compatible with bacteremic infection (6). Endocarditis was defined by using the Duke criteria (32). Polymicrobial bacteremia was defined as isolation from blood culture of one or more additional species of bacteria concomitantly with enterococci (same blood culture or another blood culture within 24 hours of the initial blood culture yielding enterococci). A single concomitant isolation of another bacterial species was sufficient, except for isolation of coagulase-negative staphylococci, diphtheroids, -hemolytic streptococci, and Bacillus species that required isolation from two blood cultures. Length of hospitalization was defined as the time in days from hospital admission to development of clinically significant enterococcal bacteremia. Enterococcal bacteremia occurring 60 days or more from a previous episode in patients already enrolled was counted as a separate episode. The end point was survival at 14 days from the first positive blood culture. Patients discharged from the hospital before 14 days were considered survivors. Medical records were reviewed at entry, at 2 weeks, at 4 weeks, and at 6 weeks (or at time of discharge or death if earlier than 6 weeks). We collected information on patient demographic characteristics, underlying disease, Acute Physiology and Chronic Health Evaluation (APACHE) II scores at bacteremia onset, antibiotic use, use of glucocorticosteroids and other immunosuppressive drugs, and receipt of invasive devices and procedures in the 2 weeks before bacteremia onset. Antibiotic therapy during the 6 weeks after the onset of bacteremia was recorded. Beyond 6 weeks, patients were followed for evidence of relapse of bacteremia and for survival to discharge or death. Immunosuppressive drugs included cyclosporine, cyclophosphamide, azathioprine, tacrolimus, methotrexate, and cytotoxic chemotherapy. Appropriate antibiotic therapy was defined as treatment with at least one antibiotic that had in vitro activity (as defined by Etest) against the enterococcal isolate, initiated within 48 hours of the initial positive enterococcal blood culture and continuing for at least 72 hours. Antibiotics considered potentially active included penicillin, ampicillin, ureidopenicillin, vancomycin, quinupristindalfopristin, chloramphenicol, doxycycline, and rifampin. Statistical Analysis For categorical variables, proportions were compared by using the Fisher exact test. Continuous variables were analyzed with the MannWhitney rank-sum test. Multivariate analysis was done by using logistic regression. Variables with a two-tailed P value of 0.05 were included in stepwise logistic regression models for vancomycin resistance and 14-day mortality. The initial bacteremic episode for each patient (n = 398) was used for the evaluation of risk factors for bacteremia caused by VRE. Patients who were alive 14 days after the onset of enterococcal bacteremia (n = 321) were evaluated for factors associated with microbiological failure. Statistical analysis of the data was performed by using the Prophet system (MarketMiner, Inc., Charlottesville, Virginia) and Epistat (Epistat Services, Richardson, Texas). Results Enterococcal Bacteremia We studied hospitalized patients 16 years of age or older with clinically significant hospital- or community-acquired enterococcal bacteremia. From February 1995 through March 1997, 391 consecutive patients from five participating institutions were entered into the study. An additional 9 patients from Pittsburgh were entered into the study over a 6-month period (October 1998 through March 1999) to increase the total number of patients to 400. These patients were consecutive and unselected. Two patients younger than 16 years of age were excluded, leaving 398 patients for evaluation. Eighty-nine patients were from the University of Pittsburgh Medical Center and the VA Medical Center, 97 were from Rush-Presbyterian-St. Lukes Medical Center, 95 were from the Detroit Medical Center and John D. Dingell VA Medical Center, 61 were from New England Medical Center, and 56 were from the William Beaumont Hospital. Blood cultures yielded 398 enterococcal isolates. Of these, 60% (239 of 398) were E. faecalis and 37% (148 of 398) were E. faecium. Three percent (10 of 398) of the isolates belonged to the less common enterococcal species, which include E. avium, E. casseliflavus, E. durans, E. gallinarum, and E. raffinosus. The species of one isolate could not be identified. Seventeen recurrences were seen at 60 or more days after the initial bacteremia. Of these, 14 were caused by the same enterococcal species as the initial episode. In 12 of these 14 episodes, the pair of isolates had the same susceptibilities to vancomycin. Overall, 35% of the 398 enterococcal isolates were resistant to vancomycin (MIC 32 g/mL), 63% were susceptible to vancomycin (MIC 4 g/mL), and 2% displayed intermediate susceptibility (MIC, 8 to 16 g/mL). Table 1 shows the susceptibility patterns of the two major Enterococcus species. Eight percent of the E. faecalis isolates were resistant to vancomycin, 91% were susceptible, and 1% displayed intermediate susceptibility. In contrast, 80% of the E. faecium isolates were resistant to vancomycin, 18% were susceptible, and 2% displayed intermediate susceptibility. Of the 11 isolates of other species, none were resistant to vancomycin, 73% (8 of 11) were susceptible to vancomycin, and 27% (3 of 11) displayed intermediate susceptibility to vancomycin. Table 1. Pr

Association between the Presence of Enterococcal Virulence Factors Gelatinase, Hemolysin, and Enterococcal Surface Protein and Mortality among Patients with Bacteremia Due to Enterococcus faecalis

The potential virulence factors of enterococci include production of enterococcal surface protein (Esp), gelatinase, and hemolysin. Gelatinase- and hemolysin-producing strains of Enterococcus faecalis have been shown to be virulent in animal models of enterococcal infections. Esp production has been shown to enhance the persistence of E. faecalis in the urinary bladder. We determined the presence of the esp gene and production of gelatinase and hemolysin in 219 E. faecalis isolates from a larger prospective study of 398 patients with enterococcal bacteremia. Thirty-two percent of isolates carried the esp gene, 64% produced gelatinase, and 11% produced hemolysin. There was no significant association between 14-day mortality and any of the markers studied, singly or in combination.

NATURAL HISTORY OF HIV-1 INFECTION

Infection with the human immunodeficiency virus type 1 (HIV-1) results in progressive loss of immune function marked by depletion of the CD4+ T-lymphocytes, leading to opportunistic infections and malignancies characteristic of AIDS. Although both host and viral determinants influence the rate of disease progression, the median time from initial infection to the development of AIDS among untreated patients ranges from 8 to 10 years. The clinical staging of HIV disease and the relative risk of developing opportunistic infections historically relied on the CD4+ T-lymphocyte counts. Although more recent studies have shown the importance of viral load quantitation in determining the rate of disease progression, it is still useful to categorize HIV disease stage on the basis of the degree of immunodeficiency: early disease (CD4+ > 500 cells/mL), mid-stage disease (CD4+ between 200 and 500 cells/mL), and end-stage disease (CD4+ < 50 cell/mL). This article reviews the natural history of HIV disease at each stage of HIV-1 infection with emphasis on acute infection and the major virologic and immunologic determinants of disease progression.

Combining fosamprenavir with lopinavir/ritonavir substantially reduces amprenavir and lopinavir exposure: ACTG protocol A5143 results

Objective:To evaluate fosamprenavir/lopinavir (LPV)/ritonavir (RTV), fosamprenavir/RTV, or LPV/RTV in antiretroviral treatment-experienced patients. Lack of drug interaction data prompted a pharmacokinetic substudy to minimize subject risk. Design:Multi-center, open-label, selectively randomized, steady-state pharmacokinetic study in HIV-infected subjects. Methods:A planned independent interim review occurred after at least eight subjects were randomized to each arm. Subjects received twice daily LPV/RTV 400/100 mg (arm A; n = 8); fosamprenavir/RTV 700/100 mg (arm B; n = 8) or LPV/RTV/fosamprenavir 400/100/700 mg (arm C; n = 17). Plasma samples were collected over 12 h between study weeks 2 and 4. Pharmacokinetic parameters were compared based on a one-sided t-test on log-transformed data with a Peto stopping boundary (P < 0.001). Results:Amprenavir mean area under the curve over 12 h (AUC0–12 h) and concentration at 12 h (C12 h) (μg/ml) were, respectively, 42.7 μg × h/ml (range, 33.1–55.1) and 2.4 μg/ml (range, 1.4–3.2) in arm B and 17.4 μg × h/ml (range, 4.6–41.3) and 0.9 μg/ml (range, 0.2–2.7) in arm C: geometric mean ratio (GMR) arm C:B was 0.36 [99.9% upper confidence boundary (UCB), 0.64] and 0.31 (99.9% h UCB, 0.61), respectively (P ≤ 0.0001). Lopinavir AUC0–12 h and C12 h were, respectively, 95.3 μg × h/ml (range, 60.3–119.3) and 6.3 μg/ml (range, 2.2–9.2) in arm A and 54.4 μg × h/ml (range, 23.5–112.2) and 3.0 μg/ml (range, 0.4–7.9) in arm C: GMR arm C:A of 0.52 (99.9% UCB, 0.89) and 0.39 (99.9% UCB, 0.98), respectively (P ≤ 0.0008). Ritonavir exposure was not significantly different between arms. Conclusion:APV and LPV exposures are significantly reduced using LPV/RTV/fosamprenavir, possibly increasing the risk of virologic failure. Consequently, A5143 was closed to enrollment.

Dyslipidaemia in HIV-infected patients: association with adherence to potent antiretroviral therapy

Metabolic complications are being increasingly recognized among HIV-infected patients treated with potent combination antiretroviral therapies. We sought to assess the association of dyslipidaemia with adherence to protease inhibitor (PI) therapy and with the markers of clinical response to antiretroviral therapy (CD4 count, HIV RNA viral level) through a prospective, cross-sectional cohort study. Fifty-six HIV-infected patients who were already on, or who were started on PI-containing antiretroviral therapy were monitored for the development of dyslipidaemias. Therapy with PI-containing antiretroviral therapy was significantly associated with elevated serum triglyceride level (>250 mg/dl) (52% vs 8%, P=0.001). Patients with an adherence rate of at least 80% to a PI-containing regimen were significantly more likely to have elevated low density lipoprotein (LDL) cholesterol level as compared to patients with an adherence rate of <80% (79% vs 26%, P=0.03). Patients with an adherence rate of at least 80% to a PI-containing regimen were also significantly more likely to have severe hypertriglyceridaemia (>800 mg/dl) as compared to patients with an adherence rate of <80% (21% vs 4%, P=0.04). Viral load at the last study visit did not correlate with total cholesterol (r=-0.39, P=0.30), LDL cholesterol (r=0.57, P=0.30), or triglyceride level (r=0.55, P=0.20). However, there was a significant correlation between the last viral load and high density lipoprotein (HDL) cholesterol (r=0.79, P=0.035), i.e. lower viral load was associated with higher HDL cholesterol level. In conclusion, dyslipidaemia in patients with HIV infection was significantly associated with adherence to PI-containing antiretroviral therapy. Patients who are adherent to PI-containing regimens at least 80% of the time warrant close monitoring for the development of dyslipidaemia.

Indinavir-associated hepatitis in patients with advanced HIV infection

Protease inhibitors including indinavir have gained widespread use in the management of HIVinfected patients. Although nephrolithiasis and asymptomatic bilirubinaemia occur commonly in association with indinavir, acute hepatitis is not a well recognized adverse effect of indinavir. We report a case of indinavir-associated severe acute hepatitis in a patient with AIDS. To our knowledge, only 3 cases of this serious adverse effect have been reported previously1. A 46-year-old man with CD4 count of 10 cells/ml had been on treatment with trimethoprim-sulfamethoxazole, zidovudine, didanosine, and desimipramine for 7 months prior to the addition of indinavir (800 mg, thrice a day). Serology for hepatitis B and C virus was negative. Liver function tests 3 weeks after the institution of indinavir were normal. Forty-six days after treatment with indinavir, the patient presented with mid-epigastric pain and nausea of one week’s duration. On examination, right upper quadrant tenderness and hepatomegaly were documented. Total bilirubin was 3.7 mg/dl, alanine aminotransferase was 123 IU/l, gamma glutamyl transpeptidase was 520 IU/l and the alkaline phosphatase was 136 IU/l. An ultrasound and CT scan of the abdomen revealed hepatomegaly with no evidence of duct dilatation. All medications were discontinued. An endoscopic retrograde cholangiopancreatogram (ERCP) was unremarkable. A liver biopsy (performed via transjugular approach) revealed steatosis, eosinophilic degeneration, and ® brosis; these ® ndings were similar to a previous biopsy proven case of indinavir hepatitis1. Over the ensuing several days, the patient developed massive ascites and anasarca requiring diuretics. His serum bilirubin peaked at 12.2 mg/dl before gradually returning to normal. Our patient developed acute onset hepatitis with severe hepatocellular injury, hypoprothrombinaemia, ascites, and anasarca that was temporally related to the initiation of indinavir. There was no evidence of viral or alcoholic hepatitis on liver biopsy and extensive workup including ERCP failed to reveal an alternative aetiology of his acute hepatitis. At the time when this case was encountered, the only reported adverse effect of indinavir associated with jaundice was asymptomatic indirect hyperbilirubinaemia documented in up to 10% of the patients2,3; discontinuation of indinavir is not recommended in such patients. Our patient, as in the 3 previous cases, had advanced AIDS as indicated by CD4 counts of less than 50/ml. Thus, indinavir-associated hepatitis should be a consideration in patients with advanced HIV infection who develop acute hyperbilirubinaemia in conjunction with abnormal transaminases upon institution of indinavir. Indinavir treatment should be promptly withheld in such patients.

Clostridium difficile Infections in Outpatient Dialysis Cohort

We examined the Clostridium difficile infection rate and risk factors in an outpatient dialysis cohort. The Cox proportional hazard for developing C. difficile infection was significantly higher with high comorbidity index and low serum albumin level. Conversely, it was lower for patients who had frequent bloodstream and dialysis access-related infections.

Randomized study of dual versus single ritonavir-enhanced protease inhibitors for protease inhibitor-experienced patients with HIV.

Abstract Purpose: To compare activity and safety of a regimen containing lopinavir/ritonavir (LPV/r) + fosamprenavir (FPV) to regimens with LPV/r or FPV + r and to test the hypothesis that a ritonavir-enhanced dual protease inhibitor (PI) regimen has better antiviral activity. Method: This study was a multicenter, open-label, randomized study. HIV-infected adults with prior PI failure were selectively randomized based on prior PI experience to either LPV/r, FPV + r, or LPV/r + FPV. All patients received tenofovir DF and 1 to 2 nucleoside reverse transcriptase inhibitors. Results: Baseline characteristics were similar across arms. Study enrollment and follow-up were stopped early (N = 56) because pharmacokinetic analyses showed significantly lower LPV and FPV exposures in the dual-PI arm. At Week 24, proportions achieving >1 log10 decline in HIV RNA or <50 copies/mL in the dual-PI versus single-PI arms combined were 75% vs. 61% in intent-to-treat (ITT, p = .17) and 100% vs. 64% in as-treated (AT) analyses (p = .02), respectively. Median CD4+ T cell/mm3 increases were 81 vs. 41 (ITT, p = .4) and 114 vs. 43 (AT, p = .08), respectively. Clinical events and toxicity rates were not different between arms. Conclusion: The trial was unable to show a difference between dual versus single PIs in ITT analyses but favored dual PIs in AT analyses.

Invasive polyarticular septic arthritis caused by nontypeable haemophilus influenzae in a young adult: a case report and literature review.

Nontypeable Haemophilus influenzae is a rare cause of septic arthritis in adults and has been reported to be associated with underlying medical conditions. We present a case of nontypeable H. influenzae-infected severe invasive polyarticular septic arthritis in a young adult without any underlying predisposing medical conditions. Diagnosis was made from both positive blood culture and joint aspiration culture. The patient was successfully treated with employment of aggressive surgical debridement of multiple affected septic joints as well as prolonged antibiotic treatment. Further laboratory testing did not reveal significant underlying medical conditions including negative HIV, normal levels of complement and IgG subclasses, and normal-appearing spleen on computed tomography. This case illustrates that nontypeable H. influenzae can cause serious invasive septic arthritis infection in both patients with and without predisposing underlying medical conditions and that prompt diagnosis with aggressive treatment of combined surgical and medical treatment can result in optimal recovery.

Actinomyces israelii endocarditis misidentified as "Diptheroids".

Actinomyces is a rare cause of endocarditis, however misidentification as Cornyebacteria often hampers the diagnosis.