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Relationship of carbapenem restriction in 22 university teaching hospitals to carbapenem use and carbapenem-resistant Pseudomonas aeruginosa.

Antimicrob Agents Chemother. 2009 May;53(5):1983-6

Authors: Pakyz AL, Oinonen M, Polk RE

Many hospital antimicrobial stewardship programs restrict the availability of selected drugs by requiring prior approval. Carbapenems may be among the restricted drugs, but it is unclear if hospitals that restrict availability actually use fewer carbapenems than hospitals that do not restrict use. Nor is it clear if restriction is related to resistance. We evaluated the relationship between carbapenem restriction and the volume of carbapenem use and both the incidence rate and proportion of carbapenem-resistant Pseudomonas aeruginosa isolates from 2002 through 2006 in a retrospective, longitudinal, multicenter analysis among a consortium of academic health centers. Carbapenem use was measured from billing records as days of therapy per 1,000 patient days. Hospital antibiograms were used to determine both the incidence rate and proportion of carbapenem-resistant P. aeruginosa isolates. A survey inquired about restriction policies for antibiotics, including carbapenems. General linear mixed models were used to examine study outcomes. Among 22 hospitals with sufficient data for analysis, overall carbapenem use increased significantly over the 5 years of study (P < 0.0001), although overall carbapenem resistance in P. aeruginosa did not change. Hospitals that restricted carbapenems (n = 8; 36%) used significantly fewer carbapenems (P = 0.04) and reported lower incidence rates of carbapenem-resistant P. aeruginosa (P = 0.01) for all study years. Fluoroquinolone use was a potential confounder of these relationships, but hospitals that restricted carbapenems actually used fewer fluoroquinolones than those that did not. Restriction of carbapenems is associated with both lower use and lower incidence rates of carbapenem resistance in P. aeruginosa.

PMID: 19273670 [PubMed - indexed for MEDLINE]

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Continuous versus intermittent infusion of oxacillin for treatment of infective endocarditis caused by methicillin-susceptible Staphylococcus aureus.

Antimicrob Agents Chemother. 2009 May;53(5):2014-9

Authors: Hughes DW, Frei CR, Maxwell PR, Green K, Patterson JE, Crawford GE, Lewis JS

Infective endocarditis (IE) is the fourth leading cause of life-threatening infection in the United States and imposes significant morbidity and mortality. The American Heart Association guidelines for the diagnosis and treatment of IE do not address continuous-infusion (CI) oxacillin. This retrospective study compares outcomes between CI oxacillin and intermittent-infusion (II) oxacillin in the treatment of IE caused by methicillin-susceptible Staphylococcus aureus (MSSA). A total of 709 medical records were reviewed for inpatients with definitive IE treated between 1 January 2000 and 31 December 2007. Continuous data were analyzed by Student’s t test or the Wilcoxon rank sum test. The chi-square test or Fisher’s exact test was used to compare nominal data. A multivariate logistic model was constructed. One hundred seven patients met eligibility criteria for inclusion into the study. Seventy-eight patients received CI oxacillin, whereas 28 received II oxacillin. CI and II groups were similar with respect to 30-day mortality (8% versus 10%, P = 0.7) and length of stay (20 versus 25 days, P = 0.4) but differed in 30-day microbiological cure (94% versus 79%, P = 0.03). Sixty-three patients received synergistic gentamicin, whereas 44 did not. The gentamicin and no-gentamicin groups were similar with respect to 30-day mortality (11% versus 4%, P = 0.2) and 30-day microbiological cure (90% versus 89%, P = 0.8); however, times to defervescence (4 versus 2 days, P = 0.02) were significantly different. CI oxacillin is an effective alternative to II oxacillin for the treatment of IE caused by MSSA and may improve microbiological cure. This convenient and pharmacodynamically optimized dosing regimen for oxacillin deserves consideration for patients with IE caused by MSSA.

PMID: 19258261 [PubMed - indexed for MEDLINE]

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Microbiological and genotypic analysis of methicillin-resistant Staphylococcus aureus bacteremia.

Antimicrob Agents Chemother. 2008 Sep;52(9):3441-3

Authors: McCalla C, Smyth DS, Robinson DA, Steenbergen J, Luperchio SA, Moise PA, Fowler VG, Sakoulas G

In a recent landmark trial of bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA) isolates, vancomycin MICs were >or=1 microg/ml for only 16% of the isolates, and accessory gene regulator (agr) function as measured by delta-hemolysin activity was absent or reduced in only 28.1% of the isolates. This clinical study did not capture a population of MRSA isolates predictive of vancomycin treatment failure.

PMID: 18606839 [PubMed - indexed for MEDLINE]

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Relationship between vancomycin MIC and failure among patients with methicillin-resistant Staphylococcus aureus bacteremia treated with vancomycin.

Antimicrob Agents Chemother. 2008 Sep;52(9):3315-20

Authors: Lodise TP, Graves J, Evans A, Graffunder E, Helmecke M, Lomaestro BM, Stellrecht K

There is growing concern that vancomycin has diminished activity for methicillin-resistant Staphylococcus aureus (MRSA) infections, with vancomycin MICs at the high end of the CLSI susceptibility range. Despite this growing concern, there are limited clinical data to support this notion. To better elucidate this, a retrospective cohort study was conducted among patients with MRSA bloodstream infections who were treated with vancomycin between January 2005 and May 2007. The inclusion criteria were as follows: at least 18 years old, nonneutropenic, with an MRSA culture that met the CDC criteria for bloodstream infection, had received vancomycin therapy within 48 h of the index blood culture, and survived >24 h after vancomycin administration. Failure was defined as 30-day mortality, bacteremia >or=10 days on vancomycin therapy, or a recurrence of MRSA bacteremia within 60 days of vancomycin discontinuation. Classification and regression tree (CART) analysis identified the vancomycin MIC breakpoint associated with an increased probability of failure. During the study period, 92 patients met the inclusion criteria. The vancomycin MIC breakpoint derived by CART analysis was >or=1.5 mg/liter. The 66 patients with vancomycin MICs of >or=1.5 mg/liter had a 2.4-fold increase in failure compared to patients with MICs of <or=1.0 mg/liter (36.4% and 15.4%, respectively; P = 0.049). In the Poisson regression, a vancomycin MIC of >or=1.5 mg/liter was independently associated with failure (adjusted risk ratio, 2.6; 95% confidence interval, 1.3 to 5.4; P = 0.01). These data strongly suggest that patients with MRSA bloodstream infections with vancomycin MICs of >or=1.5 mg/liter respond poorly to vancomycin. Alternative anti-MRSA therapies should be considered for these patients.

PMID: 18591266 [PubMed - indexed for MEDLINE]

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Bloodstream infections caused by extended-spectrum-beta-lactamase- producing Escherichia coli: risk factors for inadequate initial antimicrobial therapy.

Antimicrob Agents Chemother. 2008 Sep;52(9):3244-52

Authors: Tumbarello M, Sali M, Trecarichi EM, Leone F, Rossi M, Fiori B, De Pascale G, D’Inzeo T, Sanguinetti M, Fadda G, Cauda R, Spanu T

Extended-spectrum-beta-lactamase (ESBL)-producing strains of Escherichia coli are a significant cause of bloodstream infections (BSI) in hospitalized and nonhospitalized patients. We previously showed that delaying effective antimicrobial therapy in BSI caused by ESBL producers significantly increases mortality. The aim of this retrospective 7-year analysis was to identify risk factors for inadequate initial antimicrobial therapy (IIAT) (i.e., empirical treatment based on a drug to which the isolate had displayed in vitro resistance) for inpatients with BSI caused by ESBL-producing E. coli. Of the 129 patients considered, 56 (43.4%) received IIAT for 48 to 120 h (mean, 72 h). Independent risk factors for IIAT include an unknown BSI source (odds ratios [OR], 4.86; 95% confidence interval [CI], 1.98 to 11.91; P = 0.001), isolate coresistance to >or=3 antimicrobials (OR, 3.73; 95% CI, 1.58 to 8.83; P = 0.003), hospitalization during the 12 months preceding BSI onset (OR, 3.33; 95% CI, 1.42 to 7.79; P = 0.005), and antimicrobial therapy during the 3 months preceding BSI onset (OR, 2.65; 95% CI, 1.11 to 6.29; P = 0.02). IIAT was the strongest risk factor for 21-day mortality and significantly increased the length of hospitalization after BSI onset. Our results underscore the need for a systematic approach to the management of patients with serious infections by ESBL-producing E. coli. Such an approach should be based on sound, updated knowledge of local infectious-disease epidemiology, detailed analysis of the patient's history with emphasis on recent contact with the health care system, and aggressive attempts to identify the infectious focus that has given rise to the BSI.

PMID: 18591273 [PubMed - indexed for MEDLINE]

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Larger vancomycin doses (at least four grams per day) are associated with an increased incidence of nephrotoxicity.

Antimicrob Agents Chemother. 2008 Apr;52(4):1330-6

Authors: Lodise TP, Lomaestro B, Graves J, Drusano GL

Recent guidelines recommend vancomycin trough concentrations between 15 and 20 mg/liter. In response, some clinicians increased vancomycin dosing to >or=4 g/day. Scant data are available regarding toxicities associated with higher vancomycin doses. The purpose of this study was to examine vancomycin-associated nephrotoxicity at >or=4 g/day. To accomplish the study objective, a cohort study among a random selection of patients receiving vancomycin or linezolid between 2005 and 2006 was performed. Patients were included if they (i) were >or=18 years of age, (ii) were nonneutropenic, (iii) were on therapy for >48 h, (iv) had baseline serum creatinine levels of <2.0 mg/dl, (v) did not suffer from cystic fibrosis, and (vi) had no intravenous contrast dye within the previous 7 days. For drug exposure, three treatment strata were created: standard vancomycin dose (<4 g/day), high vancomycin dose (>or=4 g/day), and linezolid. Nephrotoxicity was defined as a serum creatinine increase of 0.5 mg/dl or 50%, whichever was greater, after therapy initiation. Stratified Kaplan-Meier analysis and Cox modeling were used to compare times to nephrotoxicity across groups. During the study, 246 patients on vancomycin (26 patients taking >or=4 g/day and 220 patients taking <4 g/day) and 45 patients on linezolid met the criteria. A significant difference in nephrotoxicity between patients receiving >or=4 g vancomycin/day, those receiving <4 g vancomycin/day, and those receiving linezolid was noted (34.6%, 10.9%, and 6.7%, respectively; P = 0.001), and Kaplan-Meier analysis identified significant differences in time to nephrotoxicity for the high-vancomycin-dose cohort compared to those for groups taking the standard dose and linezolid. In the Cox model, patients taking >or=4 g vancomycin/day, a total body weight of >or=101.4 kg, estimated creatinine clearance of </=86.6 ml/min, and intensive care unit residence were independently associated with time to nephrotoxicity. The data suggest that higher-dose vancomycin regimens are associated with a higher likelihood of vancomycin-related nephrotoxicity.

PMID: 18227177 [PubMed - indexed for MEDLINE]

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Outcome of vancomycin treatment in patients with methicillin-susceptible Staphylococcus aureus bacteremia.

Antimicrob Agents Chemother. 2008 Jan;52(1):192-7

Authors: Kim SH, Kim KH, Kim HB, Kim NJ, Kim EC, Oh MD, Choe KW

Limited data on the clinical outcome of vancomycin treatment compared with that of beta-lactam treatment in patients with methicillin-susceptible Staphylococcus aureus bacteremia (MSSA-B) are available. We used different and complementary approaches: (i) a retrospective cohort study using a propensity score to adjust for confounding by treatment assignment and (ii) a matched case-control study. Of all patients with S. aureus bacteremia (SAB) in two university-affiliated hospitals over a 7-year period, 294 patients with MSSA-B were enrolled in the cohort study. The cases for the case-control study were defined as patients who received vancomycin treatment for MSSA-B; the controls, who were patients that received beta-lactam treatment for MSSA-B, were selected at a 1:2 (case:control) ratio according to the objective matching scoring system and the propensity score system. In the cohort study, SAB-related mortality in patients with vancomycin treatment (37%, 10/27) was significantly higher than that in those with beta-lactam treatment (18%, 47/267) (P = 0.02). In addition, multivariate analysis revealed that vancomycin treatment was associated with SAB-related mortality when independent predictors for SAB-related mortality and propensity score were considered (adjusted odds ratio of 3.3, 95% confidence interval of 1.2 to 9.5). In the case-control study using the objective matching scoring system and the propensity score system, SAB-related mortality in case patients was 37% (10/27) and in control patients 11% (6/54) (P < 0.01). Our data suggest that vancomycin is inferior to beta-lactam in the treatment of MSSA-B.

PMID: 17984229 [PubMed - indexed for MEDLINE]

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Phase II, randomized, multicenter, double-blind, placebo-controlled trial of a polyclonal anti-Staphylococcus aureus capsular polysaccharide immune globulin in treatment of Staphylococcus aureus bacteremia.

Antimicrob Agents Chemother. 2007 Dec;51(12):4249-54

Authors: Rupp ME, Holley HP, Lutz J, Dicpinigaitis PV, Woods CW, Levine DP, Veney N, Fowler VG

New treatment modalities are needed for the treatment of infections due to multidrug-resistant Staphylococcus aureus. S. aureus capsular polysaccharide immune globulin (Altastaph) is a polyclonal immune globulin preparation that is being developed as adjunctive therapy for persons with S. aureus infections complicated by bacteremia. In a phase II, multicenter, randomized, double-blind, placebo-controlled trial, 40 subjects with documented S. aureus bacteremia received standard therapy plus either Altastaph at 200 mg/kg of body weight in each of two infusions 24 h apart or placebo. During the 42-day observation period, antibody pharmacokinetics and safety were the primary characteristics studied. Information regarding the resolution of bacteremia and fever was also analyzed. Anti-type-5 and anti-type-8 capsular antibody levels peaked after the second infusion at 550 mug/ml and 419 mug/ml, respectively, and remained above 100 mug/ml at day 28. A total of 316 adverse events were noted in 39 of 40 subjects. Infusion-related adverse events in Altastaph recipients were infrequent and similar to those among recipients of commercial intravenously administered immunoglobulin G products. Five of 21 (23%) subjects in the Altastaph group died, whereas 2 of 18 (11%) subjects in the placebo group died (P = 0.42). Compared to the control patients, the Altastaph recipients had a shorter median time to the resolution of fever (2 days and 7 days, respectively; P = 0.09) and a shorter length of hospital stay (9 days and 14 days, respectively; P = 0.03). However, these findings are exploratory, and there were few differences in the other variables measured. High levels of opsonizing antibodies were maintained for the initial 4 weeks. Although the study was not powered to show efficacy, these preliminary findings and safety profile suggest that Altastaph may be an effective adjunct to antibiotics and warrants further investigation (ClinicalTrials.gov number NCT00063089).

PMID: 17893153 [PubMed - indexed for MEDLINE]

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