The complete genomes of Staphylococcus aureus bacteriophages 80 and 80α--implications for the specificity of SaPI mobilization.

Staphylococcus aureus pathogenicity islands (SaPIs) are mobile elements that are induced by a helper bacteriophage to excise and replicate and to be encapsidated in phage-like particles smaller than those of the helper, leading to high-frequency transfer. SaPI mobilization is helper phage specific; only certain SaPIs can be mobilized by a particular helper phage. Staphylococcal phage 80α can mobilize every SaPI tested thus far, including SaPI1, SaPI2 and SaPIbov1. Phage 80, on the other hand, cannot mobilize SaPI1, and ϕ11 mobilizes only SaPIbov1. In order to better understand the relationship between SaPIs and their helper phages, the genomes of phages 80 and 80α were sequenced, compared with other staphylococcal phage genomes, and analyzed for unique features that may be involved in SaPI mobilization.

Early outcomes of coronary artery bypass with and without cardiopulmonary bypass in octogenarians.

BACKGROUND: Off-pump coronary artery bypass (OPCAB) surgery has been successfully used in diverse patient populations and has been postulated to be safer than conventional coronary artery bypass (CCAB) surgery in some high-risk patients, including the elderly. OBJECTIVE: To compare the safety of OPCAB surgery versus CCAB surgery in the octogenarian population of two large southwestern Ontario cardiac surgical units. RESULTS: Two hundred thirty-six consecutive octogenarians underwent primary isolated coronary artery bypass surgery from November 2000 to March 2005. Patients undergoing OPCAB surgery tended to have higher Parsonnet scores, while patients undergoing CCAB surgery had a greater number of emergent operations. The Canadian Cardiovascular Network predicted that mortality risk was similar in both groups. In-hospital mortality was similar between groups, as was postoperative myocardial infarction and new onset of renal dysfunction. However, in the OPCAB group, there was a decreased incidence of postoperative neurological dysfunction (2.3% in the OPCAB group versus 10.5% in the CCAB group, P=0.01), in particular cerebrovascular accidents (1.5% in the OPCAB group versus 7.6% in the CCAB group, P=0.05), and a decreased incidence of prolonged intubation (5.3% in the OPCAB group versus 13.3% in the CCAB group, P=0.04). Multivariable analysis found that cardiopulmonary bypass had no significant impact on mortality or length of stay. CONCLUSIONS: In octogenarian patients, OPCAB surgery is as safe as CCAB surgery in terms of mortality and major morbidity. Furthermore, a significant reduction in neurological dysfunction and prolonged intubation was seen in the OPCAB group compared with the CCAB group.

Change in practice patterns in the management of diabetic cardiac surgery patients.

Diabetes and elevated blood glucose (BG) levels > 11.1 mmol/L in the acute post-operative period have been identified as risk factors for surgical site infections (SSI) and nosocomial infections (Furnary, Zerr, Grunkemeir, & Starr, 1999; American College of Endocrinology consensus guidelines for glycemic control, 2002). Some studies have suggested that intensive insulin therapy reduced in-hospital mortality and that a continuous insulin infusion should be a standard of care for diabetic cardiac surgery patients (Furnary et al., 2003; Brown & Dodek, 2001). Our urban tertiary care teaching hospital initiated an insulin nomogram in the intensive care unit intending to more effectively control blood glucose (BG) levels in cardiac surgical patients. This cohort study compared glucose control and clinical outcomes in 53 diabetic cardiac surgery patients prior to the initiation of the insulin infusion and 50 patients following the implementation between October 2002 and April 2003. Results demonstrated target glucose control in the ICU was improved by 20% (p < .001) and mean BG was lower in the intervention group (p < .001). However, target glucose (6.1-10.0 mmol/L) was exceeded in 45% of patients in the intervention group, 65% in the control group as well as 42% of patients on the ward. The insulin nomogram is now initiated as soon as the BG is obtained immediately following patient transfer from the operating room (OR). There is more aggressive use of sliding scale insulin, and earlier resumption of pre-operative diabetic regimens on the ward.

Role of the double-strand origin cruciform in pT181 replication.

pT181 is a small rolling-circle plasmid from Staphylococcus aureus whose initiator protein, RepC, melts the plasmid's double-strand origin (DSO) and extrudes a cruciform involving IR II, a palindrome flanking the initiation nick site. We have hypothesized that the cruciform is required for initiation, providing a single-stranded region for the assembly of the replisome (R. Jin et al., 1997, EMBO J. 16, 4456-4566). In this study, we have tested the requirement for cruciform extrusion by disrupting the symmetry of the IR II palindrome or by increasing its length. The modified DSOs were tested for replication with RepC in trans. Rather surprisingly, disruption of the IR II symmetry had no detectable effect on replication or on competitivity of the modified DSO, though plasmids with IR II disrupted were less efficiently relaxed than the wild type by RepC. However, in conjunction with IR II disruption, modification of the tight RepC binding site IR III blocked replication. These results define two key elements of the pT181 initiation mechanism--the IR II conformation and the RepC binding site (IR III)--and they indicate that pT181 replication initiation is sufficiently robust to be able to compensate for significant modifications in the configuration of the DSO.

Single vs bilateral, sequential lung transplantation for end-stage emphysema: influence of recipient age on survival and secondary end-points.

BACKGROUND: The appropriate age to perform bilateral, sequential lung transplants (BSLT) in patients with chronic obstructive pulmonary disease (COPD) remains controversial. Although single lung transplant (SLT) offers an advantage in terms of organ availability, the long-term survival may not warrant this strategy in all age groups. METHODS: We analyzed 2,260 lung transplant recipients (1835 SLT, 425 BSLT) with COPD recorded in the International Society for Heart and Lung Transplantation/United Network for Organ Sharing thoracic registry between January 1991 and December 1997. To assess mortality, we performed univariate (Kaplan-Meier method and the chi-square statistic) and multivariate analyses (proportional hazards method). Because of incomplete morbidity data in the international registry, only data from U.S. centers (n = 1778, 1467 SLT, 311 BSLT) were used in the morbidity analysis. RESULTS: Survival rates (%) computed using the Kaplan-Meier method at 30 days, 1 year, and 5 years for the patients aged < 50 years were 93.6, 80.2, and 43.6, respectively, for the SLT patients, and 94.9, 84.7, and 68.2, respectively, for the BSLT patients. For patients aged 50 to 60 years, survival rates (%) were 93.5, 79.4, and 39.8 for the SLT patients compared with 93.0, 79.7, and 60.5 for the BSLT patients. For those aged > 60 years, SLT survival (%) was 93.0, 72.9, and 36.4, compared with 77.8 and 66.0 for the BSLT group (a 5-year rate could not be completed in this group). The multivariate model showed a higher risk ratio for mortality in patients aged 40 to 57 years who received SLT vs BSLT. Recipient age and procedure type did not appear to affect the development of rejection, bronchiolitis obliterans, bronchial stricture, or lung infection. CONCLUSIONS: Single lung transplant may offer acceptable early survival for patients with end-stage respiratory failure. However, long-term survival data favors BSLT in recipients until approximately age 60 years. These data suggest that a BSLT approach offers a significant survival advantage to recipients younger than 60 years of age.

Cumulative sum failure analysis of a policy change from on-pump to off-pump coronary artery bypass grafting.

BACKGROUND: Use of the sequential probability cumulative sum (CUSUM) technique may be more sensitive than standard statistical analyses in detecting a cluster of surgical failures. We applied CUSUM methods to evaluate the learning curve after a policy change by a single surgeon from routine on-pump (cardiopulmonary bypass [CPB]) to off-pump coronary artery bypass grafting (OPCAB). METHODS: Fifty-five consecutive first-time coronary artery bypass patients (CPB group) were compared with the next 55 patients undergoing an attempt at routine OPCAB using the same coronary stabilizer. The goal in OPCAB patients was to obtain complete revascularization, albeit with a low threshold for conversion to CPB to maximize patient safety during the learning curve. Preoperative patient risk was calculated using previously validated models of the Cardiac Care Network of Ontario. The occurrence of operative mortality and nine predefined major complications (myocardial infarction, bleeding, stroke, renal failure, balloon pump use, mediastinitis, respiratory failure, life-threatening arrhythmia, and sepsis) was compared between the CPB and OPCAB groups using Wilcoxon, Fisher exact, and two-tailed t tests, as well as CUSUM methodology. An intention to treat analysis was performed. RESULTS: The CPB and OPCAB groups had similar predicted mortality and length of stays (2.2% +/- 2.5%, 8.1 +/- 2.5 days versus 2.4% +/- 3.5%, 8.1 +/- 2.4 days, respectively). The mean number of grafts per patient was 3.1 +/- 0.7 in the CPB group versus 3.0 +/- 0.7 in the OPCAB group (p = 0.45). Two of 55 (3.6%) CPB patients died, as opposed to 1 of 55 (1.8%) OPCAB patients (p = 0.99). Eight of 55 CPB patients (14.5%) incurred major complications, as opposed to 4 of 55 (7.3%) OPCAB patients (p = 0.36). Median hospital length of stay was 6.0 days in the CPB group versus 5.0 days in the OPCAB group (p = 0.28). On CUSUM analysis, the failure curve in CPB patients approached the upper 80% alert line after eight cases, whereas the curve in OPCAB patients reached below the lower 80% (reassurance) boundary 28 cases after the policy change, indicating superior results in the OPCAB group despite the learning curve. CONCLUSIONS: A policy change from coronary artery bypass on CPB to routinely attempting OPCAB can be accomplished safely despite the learning curve. CUSUM analysis was more sensitive than standard statistical methods in detecting a cluster of surgical failures and successes.

Molecular genetics of SaPI1--a mobile pathogenicity island in Staphylococcus aureus.

The Staphylococcus aureus gene for toxic shock toxin (tst) is carried by a 15 kb mobile pathogenicity island, SaPI1, that has an intimate relationship with temperate staphylococcal phage 80alpha. During phage growth, SaPI1 is excised from its unique chromosomal site, attC, replicates autonomously, interferes with phage growth, and is efficiently encapsidated into special small phage heads commensurate with its size. Upon transfer to a recipient organism, SaPI1 integrates at attC by means of a self-coded integrase. One or more phage functions are required for excision, autonomous replication and encapsidation of the element and, thus, the overall relationship between SaPI1 and 80alpha is similar to that between coliphages P4 and P2. Among other staphylococcal phages tested, only phi13 interacts with SaPI1, inducing excision but not replication or transfer of the element.

Predictors of general surgical complications after heart transplantation.

BACKGROUND: Several studies have reported the incidence, morbidity, and mortality of general surgical conditions (GSCs) in orthotopic heart transplant (OHT) patients. The following is the largest reported series of such patients and the first study with sufficient patient numbers to formally evaluate peritransplant variables as risk factors for GSC development. STUDY DESIGN: A GSC was defined as a condition for which a general surgeon had been consulted or as a general surgical condition recognized at the time of autopsy. The records of 453 consecutive patients who underwent OHT between 1981 and 1999 were reviewed to identify patients who developed a GSC. Kaplan-Meier actuarial analysis on this cohort, and univariate and multivariate logistic regression models applied to a subpopulation of 324 consecutive OHT patients between 1987 and 1997 were used to determine factors associated with and predictive of GSC after OHT. RESULTS: Of 453 OHT patients, 371 (81.9%) were men, and the average age was 44.5 +/- 15 (standard deviation) years. Median followup was 2,086 days (range 1 to 6,642 days). Ninety-three patients (20.5%) developed 111 GSCs. Of these, 78 were men, and the average age was 49.9+/-10.2 years. There were 83 general surgical interventions. Actuarial analyses revealed that age greater than 50 years, pretransplant diagnosis of ischemic (PTDxI) versus nonischemic heart disease, and previous general surgical history were factors associated (p < 0.05) with a higher GSC incidence. Gender, more urgent transplant priority status, cardiopulmonary bypass time, total graft ischemic time, and intensive care unit length of stay were not associated with GSC. Factors associated with GSC on univariate analysis, with odds ratios (ORs) and 95% confidence intervals (CIs) included: age analyzed as a continuous variable (OR 1.04 per year; CI 1.01, 1.06 per year; p = 0.0021), PTDxI (OR 2.40; CI 1.39, 4.15; p = 0.0016), and pretransplant general surgical history (OR 3.35; CI 1.65, 6.82; p = 0.0008). Multivariate analysis revealed that only pretransplant general surgical history (OR 3.27; CI 1.58, 6.76; p = 0.0004) and PTDxI (OR 2.37; CI 1.35, 4.16; p = 0.0023) were associated with subsequent development of GSC. CONCLUSIONS: A pretransplant diagnosis of ischemic heart disease and previous history of a general surgical procedure are two independent risk factors that predispose OHT patients to development of GSC. Because GSC may arise insidiously in immunosuppressed patients, identification of OHT patients at higher risk for GSC will permit timely intervention decisions, decreasing morbidity and mortality in this challenging group of patients.

Pathogenicity and resistance islands of staphylococci.

Variable genetic elements including plasmids, transposons and prophages are involved in pathogenesis and antibiotic resistance, and are an important component of the staphylococcal genome. This review covers a set of newly described variable chromosomal elements, pathogenicity and resistance islands, carrying superantigen and resistance genes, especially toxic shock and methicillin resistance, respectively.

Subinhibitory clindamycin differentially inhibits transcription of exoprotein genes in Staphylococcus aureus.

It has long been known that certain antibiotics, at subinhibitory concentrations, differentially inhibit the synthesis of alpha-hemolysin and other staphylococcal virulence factors. In this report, we show that subinhibitory clindamycin (SBCL) eliminates production of nearly all exoproteins by Staphylococcus aureus but has virtually no effect on cytoplasmic proteins. The effect was abolished by a gene conferring resistance to macrolides-lincosamides-streptogramin B, showing that differential inhibition of protein synthesis is responsible; remarkably, however, subinhibitory clindamycin blocked production of several of the individual exoprotein genes, including spa (encoding protein A), hla (encoding alpha-hemolysin), and spr (encoding serine protease), at the level of transcription, suggesting that the primary effect must be differential inhibition of the synthesis of one or more regulatory proteins. In contrast to earlier reports, however, we found that subinhibitory clindamycin stimulates synthesis of coagulase and fibronectin binding protein B, also at the level of transcription. agr and sar expression was minimally affected by subinhibitory clindamycin. These effects varied from strain to strain and do not seem to be responsible for the effects of subinhibitory clindamycin on the overall exoprotein pattern.

RAVECAB: improving outcome in off-pump minimal access surgery with robotic assistance and video enhancement.

OBJECTIVE: To determine the efficacy of using the harmonic scalpel and robotic assistance to facilitate thoracoscopic harvest of the internal thoracic artery (ITA). DESIGN: A case series. SETTING: London Health Sciences Centre, University of Western Ontario, London, Ont. PATIENTS AND METHODS: Fifteen consecutive patients requiring harvest of the ITA for coronary artery bypass grafting. INTERVENTION: Robot-assisted, video-enhanced coronary artery bypass (RAVECAB) through limited-access incisions, using the harmonic scalpel and a voice-activated robotic assistant. MAIN OUTCOME MEASURES: Ease and duration of the harvesting technique, complications of the procedure, graft flow and patency, and duration of postoperative hospitalization. RESULTS: RAVECAB facilitated thoracoscopic dissection of the ITA with the harmonic scalpel in all cases. There were no conversions to a standard approach and no reoperations for bleeding. The mean (and standard deviation) ITA harvest time was 64.1 (22.9) minutes (range from 40 to 118 minutes). Robotic voice command capture rate was greater than 95%. Mean (and SD) intraoperative graft flows were 33.1 (26.8) mL/min (range from 14 to 126 mL/min). There was 100% graft patency on postoperative angiography. There were no deaths, perioperaive myocardial infarction or arrhythmias. Mean (and SD) postoperative hospitalization was 3.3 (0.8) days. CONCLUSIONS: RAVECAB is a demanding procedure that addresses many of the disadvantages of the "conventional" minimally invasive coronary artery bypass. It allows complete pedicle dissection with minimal ITA manipulation and assures sufficient conduit length and a tension-free coronary artery anastomosis. All anastomoses were performed under direct vision through a 5- to 8-cm inferior mammary incision.

Biochemical and biological properties of Staphylococcal enterotoxin K.

Staphylococcus aureus is an important human pathogen which is implicated in a wide variety of diseases. Major determinants of the virulence of this organism include extracellular virulence factors. Staphylococcal enterotoxins (SEs) are important causative agents in staphylococcal toxic shock syndrome and food poisoning. Our study identified a novel enterotoxin, SEK, and examined its biochemical and biological properties. SEK had a molecular weight of 26,000 and an experimentally determined pI of between 7.0 and 7.5. SEK was secreted by clinical isolates of S. aureus. We demonstrated that SEK had many of the biological activities associated with the SEs, including superantigenicity, pyrogenicity, the ability to enhance the lethal effect of endotoxin, and lethality in a rabbit model when administered by subcutaneous miniosmotic pump. Recombinant SEK was shown to stimulate human CD4(+) and CD8(+) T cells in a Vbeta-specific manner; T-cells bearing Vbeta 5.1, 5.2, and 6.7 were significantly stimulated to proliferate.

An alternative arterial conduit for totally endoscopic multivessel coronary artery bypass.

BACKGROUND: The ultimate goal of coronary artery bypass grafting (CABG) is the performance of a totally endoscopic procedure using multiple arterial conduits. At our center we have been routinely performing endoscopic robotic harvesting of internal thoracic arteries (ITAs) for use in minimally invasive CABG. The right gastroepiploic artery (RGEA) has been shown to be a reliable and versatile arterial conduit for bypass to coronary vessels not easily accessible by an ITA. The RGEA has already been harvested less invasively through a small laparotomy. This procedure could be made even less invasive by harvesting the RGEA laparoscopically, but this procedure has not yet been reported. The purpose of this study was to develop an endoscopic technique for harvesting the RGEA and demonstrate the safety and efficacy of this less invasive approach. METHODS: Twenty Duroc X Hampshire swine were administered general anesthesia and intubated. Ten mm and 5 mm trocars were then inserted. A 10 mm, 30-degree endoscope was adapted to a voice-activated robotic arm (AESOP), and the RGEA was harvested totally endoscopically using 5 mm harmonic scalpel shears. Intraoperative events and RGEA harvest times were recorded, and RGEA flows were measured after harvest. RGEA was delivered into the pericardial sac endoscopically. RESULTS: All RGEAs were successfully harvested without injury. Harvest time averaged 29.9+/- 10.9 min. The harvested conduits averaged 24.7+/- 2.37 cm in length. Flows were excellent in all harvested conduits, averaging 81.1+/- 31.8 cc/min. The harmonic scalpel controlled all RGEA branches with excellent hemostasis. CONCLUSION: The RGEA can be harvested safely through port access with robotic assistance. This conduit is of sufficient length to be used as an alternative arterial conduit for totally endoscopic multivessel coronary artery bypass.

Robot-assisted computer enhanced closed-chest coronary surgery: preliminary experience using a Harmonic Scalpel and ZEUS.

BACKGROUND: Successful endoscopic harvesting of arterial conduits is critical to the performance of totally endoscopic bypass grafting. Recent success with computer-enhanced robotic systems in the performance of endoscopic single vessel coronary artery bypass (ENDOCAB) has paved the way for developing techniques for multivessel ENDOCAB. The Harmonic Scalpel (Ethicon Endo-Surgery, Cincinnati, OH) has previously demonstrated versatility and efficacy in manual endoscopic internal thoracic artery (ITA) harvesting. This study was undertaken to determine the feasibility of adapting this technology to a robotic telemanipulation system and its safety and efficacy in telerobotic ITA harvesting. METHODS: The Harmonic Scalpel was adapted to the ZEUS robotic surgical system (Computer Motion, Goleta, CA) and used to harvest the ITA in 19 patients undergoing multivessel off-pump coronary artery bypass (OPCAB) surgery. With the left lung collapsed, the ITA was harvested in all patients with CO2 insufflation through three 5 mm ports in the left chest. Postoperative angiography and transthoracic Doppler studies were performed in all patients. RESULTS: There were no ITA injuries and patients tolerated insufflation without hemodynamic compromise. Side branches were controlled easily without bleeding. Average ITA harvest time was 65 +/- 21 minutes. All vessels were patent after harvesting and demonstrated no angiographic evidence of injury. CONCLUSIONS: This paper demonstrates a technique by which the Harmonic Scalpel can be readily adapted to the ZEUS robotic telemanipulation system. Using this system, ITA's can be safely harvested totally endoscopically within a reasonable time frame for patients undergoing ENDOCAB.

Effect of donor age and ischemic time on intermediate survival and morbidity after lung transplantation.

BACKGROUND: Pressure to expand the donor pool has required the use of lungs from older donors or from more-distant procurement areas. The long-term consequences of this policy have not yet been fully addressed. The effect of donor age and donor ischemic time on intermediate survival and important secondary end points after lung transplantation was therefore examined. METHODS: A cohort of 1,800 lung transplant recipients with complete 2-year follow-up, operated on in the United States between April 1, 1993, and March 31, 1996, was studied to assess survival. For analysis of secondary end points, the cohort was limited to 1,450 patients. RESULTS: Donor age when analyzed independently did not significantly affect intermediate survival (p = 0.4). Secondary end points were also not affected by age, with the exception of the incidence of hospitalization for rejection in the univariate analysis (p = 0.02) and in the multivariate analysis (p = 0.04). Moreover, there was not a significant impact of donor age or ischemic time independently on survival in the multivariate analysis. Similarly, when the interaction between ischemic time and donor age was examined in all of the multivariate models, none of the secondary end points were found to be significantly influenced. However, the combined interaction between donor age and ischemia time demonstrated a significantly worse survival at 2 years (p = 0.02) with donor age of > 50 years and donor ischemic time > 7 h. CONCLUSIONS: Donor age and donor ischemic time did not independently influence survival or important secondary end points after lung transplantation. However, intermediate-term survival was affected by the use of older donors when combined with a prolonged ischemic time. The impact of this combination should be considered when attempting to expand the donor pool.

Rational design of a global inhibitor of the virulence response in Staphylococcus aureus, based in part on localization of the site of inhibition to the receptor-histidine kinase, AgrC.

Two-component signaling systems involving receptor-histidine kinases are ubiquitous in bacteria and have been found in yeast and plants. These systems provide the major means by which bacteria communicate with each other and the outside world. Remarkably, very little is known concerning the extracellular ligands that presumably bind to receptor-histidine kinases to initiate signaling. The two-component agr signaling circuit in Staphylococcus aureus is one system where the ligands are known in chemical detail, thus opening the door for detailed structure-activity relationship studies. These ligands are short (8- to 9-aa) peptides containing a thiolactone structure, in which the alpha-carboxyl group of the C-terminal amino acid is linked to the sulfhydryl group of a cysteine, which is always the fifth amino acid from the C terminus of the peptide. One unique aspect of the agr system is that peptides that activate virulence expression in one group of S. aureus strains also inhibit virulence expression in other groups of S. aureus strains. Herein, it is demonstrated by switching the receptor-histidine kinase, AgrC, between strains of different agr specificity types, that intragroup activation and intergroup inhibition are both mediated by the same group-specific receptors. These results have facilitated the development of a global inhibitor of virulence in S. aureus, which consists of a truncated version of one of the naturally occurring thiolactone peptides.