The study presented here was performed in order to create a rule that identifies subjects at high risk for invasive candidiasis in the intensive care setting. Retrospective review and statistical modelling were carried out on 2,890 patients who stayed at least 4 days in nine hospitals in the USA and Brazil; the overall incidence of invasive candidiasis in this group was 3% (88 cases). The best performing rule was as follows: Any systemic antibiotic (days 1-3) OR presence of a central venous catheter (days 1-3) AND at least TWO of the following-total parenteral nutrition (days 1-3), any dialysis (days 1-3), any major surgery (days -7-0), pancreatitis (days -7-0), any use of steroids (days -7-3), or use of other immunosuppressive agents (days -7-0). The rate of invasive candidiasis among patients meeting the rule was 9.9%, capturing 34% of cases in the units, with the following performance: relative risk 4.36, sensitivity 0.34, specificity 0.90, positive predictive value 0.01, and negative predictive value 0.97. The rule may identify patients at high risk of invasive candidiasis.

Pulmonary tuberculosis (TB) is caused by Mycobacterium tuberculosis in susceptible humans. Here, we infected Diversity Outbred (DO) mice with ∼100 bacilli by aerosol to model responses in a highly heterogeneous population. Following infection, ‘supersusceptible’, ‘susceptible’ and ‘resistant’ phenotypes emerged. TB disease (reduced survival, weight loss, high bacterial load) correlated strongly with neutrophils, neutrophil chemokines, tumor necrosis factor (TNF) and cell death. By contrast, immune cytokines were weak correlates of disease. We next applied statistical and machine learning approaches to our dataset of cytokines and chemokines from lungs and blood. Six molecules from the lung: TNF, CXCL1, CXCL2, CXCL5, interferon-γ (IFN-γ), interleukin 12 (IL-12); and two molecules from blood – IL-2 and TNF – were identified as being important by applying both statistical and machine learning methods. Using molecular features to generate tree classifiers, CXCL1, CXCL2 and CXCL5 distinguished four classes (supersusceptible, susceptible, resistant and non-infected) from each other with approximately 77% accuracy using completely independent experimental data. By contrast, models based on other molecules were less accurate. Low to no IFN-γ, IL-12, IL-2 and IL-10 successfully discriminated non-infected mice from infected mice but failed to discriminate disease status amongst supersusceptible, susceptible and resistant M.-tuberculosis-infected DO mice. Additional analyses identified CXCL1 as a promising peripheral biomarker of disease and of CXCL1 production in the lungs. From these results, we conclude that: (1) DO mice respond variably to M. tuberculosis infection and will be useful to identify pathways involving necrosis and neutrophils; (2) data from DO mice is suited for machine learning methods to build, validate and test models with independent data based solely on molecular biomarkers; (3) low levels of immunological cytokines best indicate a lack of exposure to M. tuberculosis but cannot distinguish infection from disease.

During tuberculosis (TB), some Mycobacterium tuberculosis bacilli persist in the presence of an active immunity and antibiotics that are used to treat the disease. Herein, by using the Cornell model of TB persistence, we further explored our recent finding that suggested that M. tuberculosis can escape therapy by residing in the bone marrow (BM) mesenchymal stem cells. We initially showed that M. tuberculosis rapidly disseminates to the mouse BM after aerosol exposure and maintained a stable burden for at least 220 days. In contrast, in the lungs, the M. tuberculosis burden peaked at 28 days and subsequently declined approximately 10-fold. More important, treatment of the mice with the antibiotics rifampicin and isoniazid, as expected, resulted in effective clearance of M. tuberculosis from the lungs and spleen. In contrast, M. tuberculosis persisted, albeit at low numbers, in the BM of antibiotic-treated mice. Moreover, most viable M. tuberculosis was recovered from the bone marrow CD271(+)CD45(-)-enriched cell fraction, and only few viable bacteria could be isolated from the CD271(-)CD45(+) cell fraction. These results clearly show that BM mesenchymal stem cells provide an antibiotic-protective niche for M. tuberculosis and suggest that unraveling the mechanisms underlying this phenomenon will enhance our understanding of M. tuberculosis persistence in treated TB patients.

BackgroundTuberculosis, the disease due to Mycobacterium tuberculosis, is an important cause of morbidity and mortality in the elderly. Use of mouse models may accelerate insight into the disease and tests of therapies since mice age thirty times faster than humans. However, the majority of TB research relies on inbred mouse strains, and these results might not extrapolate well to the genetically diverse human population. We report here the first tests of M. tuberculosis infection in genetically heterogeneous aging mice, testing if old mice benefit from rapamycin.FindingsWe find that genetically diverse aging mice are much more susceptible than young mice to M. tuberculosis, as are aging human beings. We also find that rapamycin boosts immune responses during primary infection but fails to increase survival.ConclusionsGenetically diverse mouse models provide a valuable resource to study how age influences responses and susceptibility to pathogens and to test interventions. Additionally, surrogate markers such as immune measures may not predict whether interventions improve survival.

Tuberculosis (TB) develops in 5% to 10% of people infected with Mycobacterium tuberculosis (M.tb), but we do not understand how TB develops. CBA/J mice may model these events, as sick mice share features with TB patients, including weight loss, M.tb growth, extensive granulomatous infiltrates, neutrophils, necrosis, and fibrosis. Here, M.tb-infected CBA/J mice were categorized clinically: those with no signs or those with 10% weight loss to determine whether clinical state was associated with lung lesions. The type and distribution of infiltrates (granulomatous with lymphoid aggregates and scattered neutrophils) were similar in mice with weight loss and in mice with no signs. The amount of infiltration and neutrophil foci were higher in mice with weight loss than in mice with no clinical signs. Necrosis and fibrosis were only identified in mice that lost weight. Our results suggest that CBA/J mice may be useful to determine if and how neutrophils contribute to TB disease progression in mouse models. Keywords CBA/J, mouse model, mycobacterium tuberculosis, neutrophils, tuberculosisIntact TH1 immunity is essential for resistance to Mycobacterium tuberculosis (M.tb) in animal models and in humans. 9,16,18,26,27,38 However, pulmonary tuberculosis (TB), which is the most common form of TB and is responsible for M.tb transmission, does not appear to be due to severe immune defects.22 How pulmonary TB develops is not fully understood but is important to investigate.11 Some contributing mechanisms have been identified such as the sst1 locus, 34 the matrix metalloproteinase-1, 13 interleukin-10, 2 and neutrophils or neutrophil-like cells. 24,30,33 We use CBA/J mice to model pulmonary TB because these mice have no known immunological defects, are relatively susceptible to M.tb infection, and maintain long-term stable M.tb burdens. 2,3,36 Yet, the manifestation of TB disease in CBA/J mice has not been completely described. Here, we show microscopic features of TB disease in CBA/J mice and in M.tb-infected CBA/J mice that have no clinical signs. This may provide another method to investigate the transition between controlled M.tb infection and TB disease.Specific-pathogen-free, 6-to 8-week-old, female CBA/J mice from Charles River Laboratories (Wilmington, MA) were maintained in ventilated cages within biosafety level 3 (BSL3) facilities at The Ohio State University (Columbus, OH) and provided with sterile food and water ad libitum. All protocols were approved by The Ohio State University's Institutional Laboratory Animal Care and Use Committee (IACUC). Mice were infected with M.tb by aerosol exposure and weighed weekly throughout M.tb infection, as previously described. 3Mice were euthanized when all of the following IACUC removal criteria were met: weight loss of 20%, unthrifty hair coat, social isolation, and tachypnea or dyspnea. In some experiments, mice were euthanized when 10% of their peak body weight was lost and there were no other clinical signs. The M.tb pulmonary burden was calculated by colonyforming u...