Health care-associated infections in children after cardiac surgery.

Few recent studies have assessed the epidemiology of health care-associated infections (HAIs) in the pediatric population after cardiac surgery. A retrospective cohort study was performed to assess the epidemiology of several types of HAIs in children 18 years of age or younger undergoing cardiac surgery from July 2010 to June 2012. Potential pre-, intra-, and postoperative risk factors, including adherence to the perioperative antibiotic prophylaxis regimen at the authors' hospital, were assessed by multivariable analysis using Poisson regression models. Microorganisms associated with HAIs and their susceptibility patterns were described. Overall, 634 surgeries were performed, 38 (6 %) of which were complicated by an HAI occurring within 90 days after surgery. The HAIs included 7 central line-associated bloodstream infections (CLABSIs), 12 non-CLABSI bacteremias, 6 episodes of early postoperative infective endocarditis (IE), 9 surgical-site infections (SSIs), and 4 ventilator-associated pneumonias (VAPs). Mechanical ventilation (rate ratio [RR] 1.07 per day; 95 % confidence interval [CI] 1.03-1.11; p = 0.0002), postoperative transfusion of blood products (RR 3.12; 95 %, CI 1.38-7.06; p = 0.0062), postoperative steroid use (RR 3.32; 95 % CI 1.56-7.02; p = 0.0018), and continuation of antibiotic prophylaxis longer than 48 h after surgery (RR 2.56; 95 % CI 1.31-5.03; p = 0.0062) were associated with HAIs. Overall, 66.7 % of the pathogens associated with SSIs were susceptible to cefazolin, the perioperative antibiotic prophylaxis used by the authors' hospital. In conclusion, HAIs occurred after 6 % of cardiac surgeries. Bacteremia and CLABSI were the most common. This study identified several potentially modifiable risk factors that suggest interventions. Further studies should assess the role of improving adherence to perioperative antibiotic prophylaxis, the age of transfused red blood cells, and evidence-based guidelines for postoperative steroids.

Interaction of onconase with the human ribonuclease inhibitor protein.

One of the tightest known protein-protein interactions in biology is that between members of the ribonuclease A superfamily and the ribonuclease inhibitor protein (RI). Some members of this superfamily are able to kill cancer cells, and the ability to evade RI is a major determinant of whether a ribonuclease will be cytotoxic. The archetypal cytotoxic ribonuclease, onconase (ONC), is in late-stage clinical trials for the treatment of malignant mesothelioma. We present here the first measurement of the inhibition of the ribonucleolytic activity of ONC by RI. This inhibition occurs with K(i)=0.15muM in a solution of low salt concentration.

Surgical site infections and bloodstream infections in infants after cardiac surgery.

OBJECTIVE: Few recent studies have assessed the epidemiology of and risk factors for surgical site infections (SSIs) and bloodstream infections (BSIs) in infants after cardiac surgery. We hypothesized that infants younger than 30 days old and those with higher Risk Adjustment in Congenital Heart Surgery-1 scores would have an increased risk of SSIs, but not an increased risk of BSIs after surgery. METHODS: We performed a retrospective cohort study of infants younger than 1 year of age undergoing cardiac surgery from January 2010 to December 2011 to determine the rates of SSIs and BSIs occurring within 3 months of surgery, risk factors associated with these infections, and causative pathogens. Multivariable associations using Cox proportional hazard modeling assessed potential risk factors for BSIs or SSIs. RESULTS: Overall, 8.7% (48 of 552) of surgical procedures were complicated by SSIs (n = 19) or BSIs (n = 29). Thus, SSIs and BSIs occurred after 3.4% and 5.3% of procedures, respectively. Multivariate models found age younger than 30 days, incorrect timing of preoperative antibiotics, and excessive bleeding within 24 hours of surgery to be significant predictors for SSIs, and duration of use of arterial lines to be a significant predictor for BSIs. Gram-positive bacteria caused 75% of SSIs and BSIs and methicillin-susceptible Staphylococcus aureus caused 63% of SSIs. DISCUSSION: We identified some potential strategies to reduce risk, including closer monitoring of timing of preoperative antimicrobial prophylaxis and enhanced efforts to achieve intraoperative hemostasis and earlier removal of arterial lines. CONCLUSIONS: SSIs and BSIs remain important complications after cardiac surgery in infants.

Onconase cytotoxicity relies on the distribution of its positive charge.

Onconase (ONC) is a member of the ribonuclease A superfamily that is toxic to cancer cells in vitro and in vivo. ONC is now in Phase IIIb clinical trials for the treatment of malignant mesothelioma. Internalization of ONC to the cytosol of cancer cells is essential for its cytotoxic activity, despite the apparent absence of a cell-surface receptor protein. Endocytosis and cytotoxicity do, however, appear to correlate with the net positive charge of ribonucleases. To dissect the contribution made by the endogenous arginine and lysine residues of ONC to its cytotoxicity, 22 variants were created in which cationic residues were replaced with alanine. Variants with the same net charge (+2 to +5) as well as equivalent catalytic activity and conformational stability were found to exhibit large (> 10-fold) differences in toxicity for the cells of a human leukemia line. In addition, a more cationic ONC variant could be either much more or much less cytotoxic than a less cationic variant, again depending on the distribution of its cationic residues. The endocytosis of variants with widely divergent cytotoxic activity was quantified by flow cytometry using a small-molecule fluorogenic label, and was found to vary by twofold or less. This small difference in endocytosis did not account for the large difference in cytotoxicity, implicating the distribution of cationic residues as being critical for lipid-bilayer translocation subsequent to endocytosis. This finding has fundamental implications for understanding the interaction of ribonucleases and other proteins with mammalian cells.

Design and characterization of an HIV-specific ribonuclease zymogen.

Ribonucleases are evoking medical interest because of their intrinsic cytotoxic activity. Most notably, ranpirnase, which is an amphibian ribonuclease, is in advanced clinical trials as a chemotherapeutic agent for the treatment of cancer. Here, we describe a strategy to create a novel antiviral agent based on bovine pancreatic ribonuclease (RNase A), a mammalian homologue of ranpirnase. Specifically, we have linked the N- and C-termini of RNase A with an amino acid sequence that is recognized and cleaved by human immunodeficiency virus (HIV) protease. This linkage obstructs the active site, forming an HIV-specific RNase A zymogen. Cleavage by HIV-1 protease increases ribonucleolytic activity by 50-fold. By relying on the proper function of HIV-1 protease, rather than its inhibition, our approach will not engender known mechanisms of resistance. Thus, we report an initial step toward a new class of agents for the treatment of HIV/AIDS.