Paul H. Johnson

Impact of Cefepime Therapy on Mortality among Patients with Bloodstream Infections Caused by Extended-Spectrum-β-Lactamase-Producing Klebsiella pneumoniae and Escherichia coli

ABSTRACT Extended-spectrum-β-lactamase (ESBL)-producing pathogens are associated with extensive morbidity and mortality and rising health care costs. Scant data exist on the impact of antimicrobial therapy on clinical outcomes in patients with ESBL bloodstream infections (BSI), and no large studies have examined the impact of cefepime therapy. A retrospective 3-year study was performed at the Detroit Medical Center on adult patients with BSI due to ESBL-producing Klebsiella pneumoniae or Escherichia coli. Data were collected from the medical records of study patients at five hospitals between January 2005 and December 2007. Multivariate analysis was performed using logistic regression. One hundred forty-five patients with BSI due to ESBL-producing pathogens, including K. pneumoniae (83%) and E. coli (16.5%), were studied. The mean age of the patients was 66 years. Fifty-one percent of the patients were female, and 79.3% were African-American. Fifty-three patients (37%) died in the hospital, and 92 survived to discharge. In bivariate analysis, the variables associated with mortality (P < 0.05) were presence of a rapidly fatal condition at the time of admission, use of gentamicin as a consolidative therapeutic agent, and presence of one or more of the following prior to culture date: mechanical ventilation, stay in the intensive care unit (ICU), and presence of a central venous catheter. In multivariate analysis, the predictors of in-hospital mortality included stay in the intensive care unit (odds ratio [OR], 2.17; 95% confidence interval [CI], 0.98 to 4.78), presence of a central-line catheter prior to positive culture (OR, 2.33; 95% CI, 0.77 to 7.03), presence of a rapidly fatal condition at the time of admission (OR, 5.13; 95% CI, 2.13 to 12.39), and recent prior hospitalization (OR, 1.92; 95% CI, 0.83 to 4.09). When carbapenems were added as empirical therapy to the predictor model, there was a trend between empirical carbapenem therapy and decreased mortality (OR, 0.61; 95% CI, 0.26 to 1.50). When added to the model, receipt of empirical cefepime alone (n = 43) was associated with increased mortality, although this association did not reach statistical significance (OR, 1.66; 95% CI, 0.71 to 3.87). The median length of hospital stay was shorter for patients receiving empirical cefepime than for those receiving empirical or consolidated carbapenem therapy. In multivariate analysis, empirical therapy with cefepime for BSI due to an ESBL-producing pathogen was associated with a trend toward an increased mortality risk and empirical carbapenem therapy was associated with a trend toward decreased mortality risk.

Electrophoresis of DNA in agarose gels: II. Effects of loading mass and electroendosmosis on electrophoretic mobilities

Abstract We have investigated several experimental factors which affect the accurate determination of electrophoretic mobilities of circular and linear DNAs in agarose gels. We demonstrate that: (1) The mobility of individual DNA species is affected by the total mass in the sample loaded. The increased mobility and band distortion observed become apparent when the DNA mass exceeds approximately 0.2 μg per 0.15 cm 2 of surface area in the loading well. (2) The migration velocity of a given DNA species depends on the coefficient of electroendosmosis (− m r ) of the agarose preparations used. In the range 0.081 ≤ − m r ≤ 0.441, the DNA migration velocity is proportional to (− m r ) −0.5 .

Epidemiology of Bloodstream Infections Caused by Acinetobacter baumannii and Impact of Drug Resistance to both Carbapenems and Ampicillin-Sulbactam on Clinical Outcomes

ABSTRACT Acinetobacter baumannii has become a leading cause of bloodstream infections (BSI) in health care settings. Although the incidence of infection with carbapenem- and ampicillin-sulbactam-resistant (CASR) A. baumannii has increased, there is a scarcity of studies which investigate BSI caused by CASR A. baumannii. A retrospective cohort study was conducted on adult patients with BSI caused by A. baumannii and who were admitted to the Detroit Medical Center between January 2006 and April 2009. Medical records were queried for patients demographics, antimicrobial exposures, comorbidities, hospital stay, and clinical outcomes. Bivariate analyses and logistic regression were employed in the study. Two hundred seventy-four patients with BSI caused by A. baumannii were included in the study: 68 (25%) caused by CASR A. baumannii and 206 (75%) caused by non-CASR A. baumannii. In multivariate analysis, factors associated with BSI caused by CASR A. baumannii included admission with a rapidly fatal condition (odds ratio [OR] = 2.83, 95% confidence interval [CI] = 1.27 to 6.32, P value = 0.01) and prior use of antimicrobials (OR = 2.83, 95% CI = 1.18 to 6.78, P value = 0.02). In-hospital mortality rates for BSI caused by CASR A. baumannii were significantly higher than those for non-CASR A. baumannii-induced BSI (43% versus 20%; OR = 3.0, 95% CI = 1.60 to 5.23, P value < 0.001). However, after adjusting for potential confounders, the association between BSI caused by CASR A. baumannii and increased risk of in-hospital mortality was not significant (OR = 1.15, 95% CI = 0.51 to 2.63, P value = 0.74). This study demonstrated that CASR A. baumannii had a distinct epidemiology compared to more susceptible A. baumannii strains; however, clinical outcomes were similar for the two groups. Admission with a rapidly fatal condition was an independent predictor for both CASR A. baumannii and in-hospital mortality.

Isolation and characterization of deoxyribonucleic acid from tissue of the woolly mammoth, Mammuthus primigenius.

DNA was isolated from tissue samples of several mammoth specimens, radiocarbon dated between 10,000 and 53,000 years old. The DNA was purified by chromatography on hydroxyapatite at 60 degrees C and was characterized as a heterogeneous population of fragments ranging in size from 3000 to 200 base pairs. Thermal denaturation analysis demonstrated that approximately 25% of the DNA had a base composition similar to Asian elephant DNA calculated as 36% G + C. Preliminary analysis by nucleic acid hybridization indicated that only a small fraction of DNA isolated from mammoth tissue (2-5%) was homologous to DNA of Asian elephant, a close living relative of the mammoth. Our results provide the first definitive isolation and characterization of DNA from ancient tissue and suggest a purification strategy that will lead to preparations of DNA from mammoth tissue significantly enriched in elephant-related DNA sequences.

Enhancement of buoyant separations between DNAs in preparative CsCl gradients containing distamycin A or netropsin

Abstract The buoyant separation in CsCl gradients between DNAs of various base composition has been studied in the presence of the polypeptide antibiotics, distamycin A and netropsin. The DNAs covered a range between 39,8 and 72% guanine + cytosine. The antibiotics, which bind preferentially to adenine-thymine-rich sequences, enhanced the separation between DNAs by an average factor of 3.5 for distamycin and 2.7 for netropsin over that found in their absence. The absolute separation for a pair of DNAs is a linear function of the base compositional difference between them.

The relaxation complex of colicinogenic factor E1: Electrophoretic properties and a novel assay system for sodium dodecyl sulfate-mediated induction☆

Abstract The relaxation complex of plasmid colicinogenic factor E1 is demonstrated to be stable during agarose gel electrophoresis in low ionic strength buffer and to migrate as a distinct species having a 3% reduction in electrophoretic mobility relative to uncomplexed native supercoiled DNA. Treatment of complex with sodium dodecyl sulfate results in the apparent activation of a repressed endonucleolytic activity (induction) resulting in conversion to a species having a mobility coincident with nicked circular DNA. We have further demonstrated that if sodium dodecyl sulfate is applied to an agarose gel at times subsequent to the application of relaxation complex, sodium dodecyl sulfate will overtake the DNA, cause induction, and result in complete separation of induced complex from all other DNA forms. This technique constitutes a rapid, sensitive, and quantitative assay for induction as well as a single-step purification procedure. Induced complex can be readily isolated from preparative gels by electroelution and demonstrated to be a substrate for DNA polymerase I in a nick translation reaction. Incorporation of radioactive nucleotides occurs specifically in a 460 base pair restriction fragment known to contain the relaxation cleavage site, the likely origin of transfer of the heavy strand during F-factor-mediated plasmid mobilization.