Clenched-fist injury complicated by methicillin-resistant Staphylococcus aureus

Hand infections are a common sequela of clenched-fist injuries. The majority of these infections are due to Staphylococcus and Streptococcus species. Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly being isolated in Canadian health care facilities. In addition, MRSA now needs to be considered in community acquired hand infections that fail to respond to common empiric therapy. A 51-year-old man with MRSA due to a hand injury was treated successfully with vancomycin. The prevalence, mechanism of resistance and treatment of MRSA are briefly reviewed.     

Exploring and embracing complexity in a distance-learning curriculum for physicians.

The recent pressures on clinical medicine such as the attention to medical error and the challenges of interdisciplinary care have also exerted pressure on health professions education. Educators must now gauge how to redesign education systems to adapt quickly to these disruptions. Sometimes disruptions can be self-inflicted, such as the VA National Quality Scholars Fellowship's decision to use interactive video (IV) as its primary medium for delivering the curriculum to its six sites around the nation. The authors describe how this disruption to their education system helped to fashion a learning environment that is adaptable. Along the journey from a classroom-based curriculum to an IV-based curriculum, the authors and others involved in the program learned the basic tenets of IV sessions, redefined the roles of the teachers and learners, and discovered an IV environment that functions as a complex adaptive learning system. This distance-learning curriculum can be a model for other health professions education, since it starts with simple rules, changes from within, has a tolerance for unpredictability, and continually moves forward and transforms itself despite tension.     

Changes in human muscle transverse relaxation following short-term creatine supplementation

The rapid increase in body mass that often occurs following creatine (Cr) supplementation is believed to be due to intracellular water retention. The purpose of this study was to determine whether Cr consumption alters the magnetic resonance (MR) transverse relaxation (T(2)) distribution of skeletal muscle. Transverse relaxation can be used to model water compartments within a cell or tissue. In this double-blind study, subjects were asked to supplement their normal diet with creatine monohydrate (20 g day(-1) for 5 days) mixed with a grape drink (Creatine group, n = 7), or the grape drink alone (Placebo group, n = 8). Phosphorous MR spectroscopy was used to determine the effectiveness of the supplementation protocol. Subjects that responded to the Cr supplementation (i.e. showed a > 5 % increase in the ratio of the levels of phosphocreatine (PCr) and ATP) were placed in the Creatine group. Both proton MR imaging and spectroscopy were used to acquire T(2) data, at 1.89 T, from the flexor digitorum profundus muscle of each subject before and after supplementation. Following the supplementation period, the Creatine group showed a gain in body mass (1.2 +/- 0.8 kg, P < 0.05, mean +/- S.D.), and an increase in PCr/ATP ratio (23.8 +/- 16.4 %, P < 0.001). Neither group showed any changes in intracellular pH or T(2) calculated from MR images. However, the spectroscopy data revealed at least three components (> 5 ms) at approximately 20, 40 and 125 ms in both groups. Only in the Creatine group was there an increase in the apparent proton concentration of the two shorter components combined (+5.0 +/- 4.7 %, P < 0.05). According to the cellular water compartment model, the changes observed in the shorter T(2) components are consistent with an increase in intracellular water.     

Staphylococcus aureus aconitase inactivation unexpectedly inhibits post-exponential-phase growth and enhances stationary-phase survival

Staphylococcus aureus preferentially catabolizes glucose, generating pyruvate, which is subsequently oxidized to acetate under aerobic growth conditions. Catabolite repression of the tricarboxylic acid (TCA) cycle results in the accumulation of acetate. TCA cycle derepression coincides with exit from the exponential growth phase, the onset of acetate catabolism, and the maximal expression of secreted virulence factors. These data suggest that carbon and energy for post-exponential-phase growth and virulence factor production are derived from the catabolism of acetate mediated by the TCA cycle. To test this hypothesis, the aconitase gene was genetically inactivated in a human isolate of S. aureus, and the effects on physiology, morphology, virulence factor production, virulence for mice, and stationary-phase survival were examined. TCA cycle inactivation prevented the post-exponential growth phase catabolism of acetate, resulting in premature entry into the stationary phase. This phenotype was accompanied by a significant reduction in the production of several virulence factors and alteration in host-pathogen interaction. Unexpectedly, aconitase inactivation enhanced stationary-phase survival relative to the wild-type strain. Aconitase is an iron-sulfur cluster-containing enzyme that is highly susceptible to oxidative inactivation. We speculate that reversible loss of the iron-sulfur cluster in wild-type organisms is a survival strategy used to circumvent oxidative stress induced during host-pathogen interactions. Taken together, these data demonstrate the importance of the TCA cycle in the life cycle of this medically important pathogen.