Geographical variability in the likelihood of bloodstream infections due to gram-negative bacteria: correlation with proximity to the equator and health care expenditure.

OBJECTIVE: Infections due to Gram-negative bacteria exhibit seasonal trends, with peak infection rates during warmer months. We hypothesized that the likelihood of a bloodstream infection due to Gram-negative bacteria increases with proximity to the equator. We tested this hypothesis and identified geographical, climatic and social factors associated with this variability. DESIGN: We established a network of 23 international centers in 22 cities. SETTING: De-identified results of positive blood cultures from 2007-2011 and data sources for geographic, climatic and socioeconomic factors were assembled for each center. PARTICIPANTS: Patients at the 23 centers with positive blood cultures. MAIN OUTCOME: Due to variability in the availability of total culture volumes across sites, our primary outcome measure was the fraction of positive blood cultures that yielded Gram-negative bacteria; sources of variability in this outcome measure were explored using meta-regression techniques. RESULTS: The mean fraction of bacteremia associated with Gram-negative bacteria was 48.4% (range 26.4% to 61.8%). Although not all sites displayed significant seasonality, the overall P-value for seasonal oscillation was significant (P<0.001). In univariate meta-regression models, temperature, latitude, latitude squared, longitude, per capita gross domestic product and percent of gross domestic product spent on healthcare were all associated with the fraction of bacteremia due to Gram-negative bacteria. In multivariable models, only percent of gross domestic product spent on healthcare and distance from the equator (ie. latitude squared) were significantly associated with the fraction of bacteremia due to Gram-negative bacteria. CONCLUSIONS: The likelihood of bacteremia due to Gram-negative bacteria varies markedly between cities, in a manner that appears to have both geographic (latitude) and socioeconomic (proportion gross domestic product devoted to health spending) determinants. Thus, the optimal approach to initial management of suspected bacteremia may be geographically specific. The rapid emergence of highly antibiotic-resistant Gram-negative pathogens may have geographically specific impacts.

Video-assisted Thoracoscopic Surgery (VATS) drainage of salmonella enteritidis empyema and needle-localization for retrieval of a dropped gallstone.

INTRODUCTION: Spillage of gallstones into the peritoneal cavity (dropped gallstones) is more common in laparoscopic compared with open cholecystectomy. Subsequent infectious complications are often delayed, occurring in 0.1% to 2.9% of cases. We present the first reported case of Salmonella enterica subphrenic abscess and empyema complicating dropped gallstones, treated with video-assisted thoracoscopic surgery (VATS), and surgical retrieval. CASE REPORT: A 67-year-old male with symptomatic cholelithiasis underwent an uncomplicated laparoscopic cholecystectomy. Four years later, he presented with a mass in his right flank, and an abdominal computed tomography (CT) revealed a right flank intramuscular abscess containing gallstones. The abscess was drained surgically with removal of gallstones. He was readmitted 15 months later with right upper quadrant pain, fever, and dyspnea. Chest and abdominal computer tomography (CT) showed a right pleural effusion and a right subphrenic abscess containing a dropped gallstone. The gallstone was localized with a needle using CT guidance. He subsequently underwent a right VATS for decortication. A separate flank incision was made at the site of the needle to drain the subphrenic abscess and retrieve the gallstone. Cultures from his empyema grew S enteritidis. The patient made an uneventful recovery. DISCUSSION: During laparoscopic cholecystectomy, efforts should be made to retrieve dropped gallstones as they can cause abscess and empyema, which might necessitate furthermore surgical intervention. The use of VATS has been established as a safe and effective alternative to thoracotomy, including the treatment of empyema. Needle-localization resulted in a successful retrieval of the gallstone in our patient. Culture of the abscess is important, as unusual organisms such as Salmonella could be present. S. enteritidis has not been implicated as a cause of cholecystitis and is rarely associated with abdominal abscesses. We postulate that the organism reached the gallbladder through the bile or bloodstream after gastrointestinal colonization and that its persistence in the gallbladder may have been facilitated by gallstones.

The kinetics of T regulatory cells in shock: beyond sepsis.

During the past decade, there have been an increasing number of studies investigating the precise role of T regulatory cells in human disease. First recognized for their ability to prevent autoimmunity, T regulatory cells control effector CD4+ and CD8+ T lymphocytes and innate immune cells by several different suppressive mechanisms, like cell to cell contact, secretion of inhibitory cytokines and cytolysis. This suppressive function of T regulatory cells could contribute in a similar way to the profound immune dysfunction seen in critical illness whether the latter is due to sepsis or severe injury.

Red cell exchange transfusion for babesiosis in Rhode Island.

We report four cases of clinically severe tick borne babesiosis treated with chemotherapy and adjunctive red cell exchange (RCE) at two Rhode Island hospitals from 2004 to 2007. All RCE procedures were performed using a Cobe Spectra device and were well tolerated without complications. The volume of allogeneic red cells used in the exchange was determined using the algorithm in the apheresis device with the input variables of preprocedure hematocrit, weight, height, an assumed allogeneic red cell hematocrit of 55 and a desired post procedure hematocrit of 27. The preprocedure level of parasitemia varied between 2.4% and 24% and the postprocedure level of parasitemia between 0.4 and 5.5% with an average overall percent reduction in parasitemia of 74%. Retrospectively, application of a new formula to calculate red cell mass appeared to correlate better with the percent reduction in parasitemia. Previous reports of RCE in babesiosis were reviewed. The reported reduction in parasitemia varied from 50% to >90%. Although a preprocedure level of parasitemia of 10% is sometimes used as a threshold for RCE in clinically severe babesiosis, this threshold does not have a firm empirical basis. No postprocedure desired level of parasitemia is indicated nor the mass of allogeneic red cells needed to achieve such a level. We conclude that current estimates of the dose of allogeneic red cells used in RCE are probably inaccurate, advocate a new formula to estimate this dose and suggest that a 90% reduction in parasitemia should be the minimally desired target of RCE in babesiosis.

Does influenza transmission occur from asymptomatic infection or prior to symptom onset?

A better understanding of transmission dynamics is essential in influenza pandemic planning. If a substantial proportion of transmissions were to occur during the presymptomatic phase or from asymptomatic individuals, then infection control measures such as contact tracing and quarantine of exposures would be of limited value. Infectiousness has been inferred based on the presence of influenza in the upper respiratory tract rather than from transmission experiments. Although asymptomatic individuals may shed influenza virus, studies have not determined if such people effectively transmit influenza. We performed a systematic review of published studies describing the relationship between viral shedding and disease transmission. Based on the available literature, we found that there is scant, if any, evidence that asymptomatic or presymptomatic individuals play an important role in influenza transmission. As such, recent articles concerning pandemic planning, some using transmission modeling, may have overestimated the effect of presymptomatic or asymptomatic influenza transmission. More definitive transmission studies are sorely needed.

A cluster of community-acquired methicillin-resistant Staphylococcus aureus infections in hospital security guards.

We investigated a cluster of methicillin-resistant Staphylococcus aureus soft-tissue infections in 5 security guards employed in a hospital emergency department. An epidemiologic investigation and molecular subtyping of isolates revealed that the source was a patient and that a community-acquired methicillin-resistant S. aureus strain (USA-300) was transmitted to healthcare workers through physical contact.

Translational research in the development of novel sepsis therapeutics: logical deductive reasoning or mission impossible?

The successful translation of promising research findings from basic research laboratories into useful clinical products for the management of septic patients has proven to be a daunting challenge. The complexity and variability of the clinical entity referred to as sepsis makes it intrinsically difficult to model preclinical systems and predict efficacy of potentially useful, experimental, therapeutic agents. Technological innovations in microarrays, microfluidics, and nanotechnology make it feasible to study the evolution of sepsis in small animal models in considerable detail. The recognized limitations of standard preclinical platforms used to study sepsis have lead to innovative approaches to study sepsis in silico, and in more complex and clinically more valid ex vivo tissue perfusion models and animal systems. It is abundantly clear that sepsis researchers need to do a better job informing clinicians about the possible benefits and potential risks of new treatment interventions as they traverse the gap between the bench and the bedside.