No abstract

It is important to know the spectrum of the microbial aetiology of prosthetic joint infections (PJIs) to guide empiric treatment and establish antimicrobial prophylaxis in joint replacements. There are no available data based on large contemporary patient cohorts. We sought to characterize the causative pathogens of PJIs and to evaluate trends in the microbial aetiology. We hypothesized that the frequency of antimicrobial-resistant organisms in PJIs has increased in the recent years. We performed a cohort study in 19 hospitals in Spain, from 2003 to 2012. For each 2-year period (2003-2004 to 2011-2012), the incidence of microorganisms causing PJIs and multidrug-resistant bacteria was assessed. Temporal trends over the study period were evaluated. We included 2524 consecutive adult patients with a diagnosis of PJI. A microbiological diagnosis was obtained for 2288 cases (90.6%). Staphylococci were the most common cause of infection (1492, 65.2%). However, a statistically significant rising linear trend was observed for the proportion of infections caused by Gram-negative bacilli, mainly due to the increase in the last 2-year period (25% in 2003-2004, 33.3% in 2011-2012; p 0.024 for trend). No particular species contributed disproportionally to this overall increase. The percentage of multidrug-resistant bacteria PJIs increased from 9.3% in 2003-2004 to 15.8% in 2011-2012 (p 0.008), mainly because of the significant rise in multidrug-resistant Gram-negative bacilli (from 5.3% in 2003-2004 to 8.2% in 2011-2012; p 0.032). The observed trends have important implications for the management of PJIs and prophylaxis in joint replacements.

Aorto-cavitary fistulous tract formation is an uncommon but extremely serious complication of IE. In-hospital mortality was exceptionally high despite aggressive management with surgical intervention in the majority of patients. Prosthetic IE, urgent surgery, and the development of HF identify the subgroup of patients with IE and ACF that have significantly increased risk of in-hospital death.

The risk factors for complications in patients with influenza A (H1N1)v virus infection have not been fully elucidated. We performed an observational analysis of a prospective cohort of hospitalized adults with confirmed pandemic influenza A (H1N1)v virus infection at 13 hospitals in Spain, between June 12 and November 10, 2009, to identify factors associated with severe disease. Severe disease was defined as the composite outcome of intensive-care unit (ICU) admission or in-hospital mortality. During the study period, 585 adult patients (median age 40 years) required hospitalization because of pandemic (H1N1) 2009. At least one comorbid condition was present in 318 (54.4%) patients. Pneumonia was diagnosed in 234 (43.2%) patients and bacterial co-infection in 45 (7.6%). Severe disease occurred in 75 (12.8%) patients, of whom 71 required ICU admission and 13 (2.2%) died. Independent factors for severe disease were age <50 years (OR, 2.39; 95% CI, 1.05-5.47), chronic comorbid conditions (OR, 2.93; 95% CI, 1.41-6.09), morbid obesity (OR, 6.7; 95% CI, 2.25-20.19), concomitant and secondary bacterial co-infection (OR, 2.78; 95% CI, 1.11-7) and early oseltamivir therapy (OR, 0.32; 95% CI 0.16-0.63). In conclusion, although adults hospitalized for pandemic (H1N1) 2009 suffer from significant morbidity, mortality is lower than that reported in the earliest studies. Younger age, chronic comorbid conditions, morbid obesity and bacterial co-infection are independent risk factors for severe disease, whereas early oseltamivir therapy is a protective factor.

Studies presented here demonstrate that individually expanded clones of murine Ly-1 B cells, perhaps analogous to the expanded neoplastic Leu-1 B-cell clones in human chronic lymphocytic leukemias, are universally detectable in young New Zealand Black (NZB)-related autoimmune mice and in senescent normal mice (>18 months old). These clones are visible as phenotypically homogeneous cell populations in multiparameter fluorescence-activated cell sorter analyses of peritoneal and splenic B cells; they show unique immunoglobulin heavy-and light-chain gene rearrangements in Southern gel analyses of peritoneal and splenic DNA; and, like the self-replenishing Ly-1 B-cell population from which they are drawn, they tend to grow readily in irradiated or unirradiated syngeneic or allotype congenic hosts. Furthermore, they develop and generalize in primary and secondary hosts in a characteristic pattern (peritoneum >> spleen > lymph node > bone marrow) that suggests that their initial growth is controlled by the mechanisms that normally control Ly-1 B-cell distribution in lymphoid organs. The universal emergence of these clones within the Ly-1 B-cell lineage may be explained by the substantially greater opportunity for hyperplastic and neoplastic transformation events in this long-lived self-replenishing Ly-1 B-cell population, which must divide relatively frequently to maintain its normal size throughout adulthood. Repeated exposure to internal or environmental antigens (with which Ly-1 B cells are known to react) may also play a role in driving the development of these clones.Recent studies divide murine B lymphocytes into two lineages: the conventional B-cell lineage, which is replenished from surface immunoglobulin-negative progenitors in the bone marrow; and the Ly-1 B lineage (Ly-1 B), which in the adult is a self-renewing population replenished from immunoglobulin-positive progenitors found largely in the peritoneal cavity (1-3). Ly-1 B cells normally comprise only 1-3% of splenic B cells; however, they constitute 40-80% of the B cells in the peritoneum (1-3). They can express two surface antigens not found on conventional murine B cells, CD5 (Ly-1) (1, 4) and CD11 (MAC-1) (5). In addition, recent studies have shown that within the Ly-1 B-cell lineage two populations exist that can be distinguished by their expression of the CD5 (Ly-1) antigen (ref. 1; A.M.S., unpublished observation). The CD5 + Ly-1 lineage B cells and the CD5 -Ly-1 B cells (also referred to as the sister population) are, except for the expression of the CD5 antigen, phenotypically, developmentally, and functionally indistinguishable. Homologous antigens Leu-1 (CD5) (6) and Leu-15 (CD11) (7) are expressed on human Leu-1 B cells.At the functional level, Ly-1 lineage B cells produce many of the autoantibodies found in normal and New Zealand Black (NZB)-related autoimmune mice (4); in addition, Ly-1