Stephanie Davis

Mouse Model of Necrotic Tuberculosis Granulomas Develops Hypoxic Lesions

BACKGROUND Preclinical evaluation of tuberculosis drugs is generally limited to mice. However, necrosis and hypoxia, key features of human tuberculosis lesions, are lacking in conventional mouse strains. METHODS We used C3HeB/FeJ mice, which develop necrotic lesions in response to Mycobacterium tuberculosis infection. Positron emission tomography in live infected animals, postmortem pimonidazole immunohistochemistry, and bacterial gene expression analyses were used to assess whether tuberculosis lesions in C3HeB/FeJ are hypoxic. Efficacy of combination drug treatment, including PA-824, active against M. tuberculosis under hypoxic conditions, was also evaluated. RESULTS Tuberculosis lesions in C3HeB/FeJ (but not BALB/c) were found to be hypoxic and associated with up-regulation of known hypoxia-associated bacterial genes (P < .001). Contrary to sustained activity reported elsewhere in BALB/c mice, moxifloxacin and pyrazinamide (MZ) combination was not bactericidal beyond 3 weeks in C3HeB/FeJ. Although PA-824 added significant activity, the novel combination of PA-824 and MZ was less effective than the standard first-line regimen in C3HeB/FeJ. CONCLUSIONS We demonstrate that tuberculosis lesions in C3HeB/FeJ are hypoxic. Activities of some key tuberculosis drug regimens in development are represented differently in C3HeB/FeJ versus BALB/c mice. Because C3HeB/FeJ display key features of human tuberculosis, this strain warrants evaluation as a more pathologically relevant model for preclinical studies.

Noninvasive pulmonary [18F]-2-fluoro-deoxy-D-glucose positron emission tomography correlates with bactericidal activity of tuberculosis drug treatment

ABSTRACT Tools for monitoring response to tuberculosis (TB) treatment are time-consuming and resource intensive. Noninvasive biomarkers have the potential to accelerate TB drug development, but to date, little progress has been made in utilizing imaging technologies. Therefore, in this study, we used noninvasive imaging to monitor response to TB treatment. BALB/c and C3HeB/FeJ mice were aerosol infected with Mycobacterium tuberculosis and administered bactericidal (standard and highly active) or bacteriostatic TB drug regimens. Serial pulmonary [18F]-2-fluoro-deoxy-d-glucose (FDG) positron emission tomography (PET) was compared with standard microbiologic methods to monitor the response to treatment. [18F]FDG-PET correctly identified the bactericidal activity of the drug regimens. Imaging required fewer animals; was available in real time, as opposed to having CFU counts 4 weeks later; and could also detect TB relapse in a time frame similar to that of the standard method. Lesion-specific [18F]FDG-PET activity also broadly correlated with TB treatment in C3HeB/FeJ mice that develop caseating lesions. These studies demonstrate the application of noninvasive imaging to monitor TB treatment response. By reducing animal numbers, these biomarkers will allow cost-effective studies of more expensive animal models of TB. Validated markers may also be useful as “point-of-care” methods to monitor TB treatment in humans.

Bacterial Thymidine Kinase as a Non-Invasive Imaging Reporter for Mycobacterium tuberculosis in Live Animals

Background Bacteria can be selectively imaged in experimentally-infected animals using exogenously administered 1-(2′deoxy-2′-fluoro-β-D-arabinofuranosyl)-5-[125I]-iodouracil ([125I]-FIAU), a nucleoside analog substrate for bacterial thymidine kinase (TK). Our goal was to use this reporter and develop non-invasive methods to detect and localize Mycobacterium tuberculosis. Methodology/Principal Findings We engineered a M. tuberculosis strain with chromosomally integrated bacterial TK under the control of hsp60 - a strong constitutive mycobacterial promoter. [125I]FIAU uptake, antimicrobial susceptibilities and in vivo growth characteristics were evaluated for this strain. Using single photon emission computed tomography (SPECT), M. tuberculosis Phsp60 TK strain was evaluated in experimentally-infected BALB/c and C3HeB/FeJ mice using the thigh inoculation or low-dose aerosol infection models. M. tuberculosis Phsp60 TK strain actively accumulated [125I]FIAU in vitro. Growth characteristics of the TK strain and susceptibility to common anti-tuberculous drugs were similar to the wild-type parent strain. M. tuberculosis Phsp60 TK strain was stable in vivo and SPECT imaging could detect and localize this strain in both animal models tested. Conclusion We have developed a novel tool for non-invasive assessment of M. tuberculosis in live experimentally-infected animals. This tool will allow real-time pathogenesis studies in animal models of TB and has the potential to simplify preclinical studies and accelerate TB research.

The effect of Haemophilus influenzae type B and pneumococcal conjugate vaccines on childhood meningitis mortality: a systematic review

BackgroundTwo of the most prevalent causes of severe bacterial meningitis in children, Haemophilus influenzae type B (Hib) and Streptococcus pneumoniae, are preventable by existing vaccines increasingly available in developing countries. Our objective was to estimate the dose-specific effect of Hib and pneumococcal conjugate vaccines (PCV) on childhood meningitis mortality in low-income countries for use in the Lives Saved Tool (LiST).MethodsWe systematically searched and reviewed published vaccine efficacy trials and observational studies reporting the effect of Hib or PCV vaccines on organism-specific meningitis, bacterial meningitis and all-cause meningitis incidence and mortality among children less than five years old in low- and middle-income countries. Data collection and quality assessments were performed using standardized guidelines. For outcomes available across multiple studies (≥2) and approximating meningitis mortality, we pooled estimates reporting dose-specific effects using random effects meta-analytic methods, then combined these with meningitis etiology data to determine the preventable fraction of childhood meningitis mortality for inclusion in LiST.ResultsWe identified 18 studies of Hib conjugate vaccines reporting relevant meningitis morbidity and mortality outcomes (2 randomized controlled trials [RCTs], 16 observational studies) but few provided dose-specific effects. A meta-analysis of four case-control studies examined the dose-specific effect of Hib conjugate vaccines on Hib meningitis morbidity (1 dose: RR=0.64, 95% CI 0.38-1.06; 2 doses: RR=0.09, 95% CI 0.03-0.27; 3 doses: RR=0.06, 95% CI 0.02-0.22), consistent with results from single RCTs. Pooled estimates of two RCTs provided evidence for the effect of three doses of PCV on vaccine-serotype meningitis morbidity (RR=0.16, 95% CI 0.02-1.20). We considered these outcomes of severe disease as proxy estimates for meningitis mortality and combined the estimates of protective effects with meningitis etiology data to provide an estimate of the preventable fraction of childhood meningitis mortality with three doses of Hib (38-43%) and pneumococcal conjugate vaccines (28-35%) for use in LiST.ConclusionsFew RCTs or vaccine effectiveness studies evaluated the dose-specific impact of Hib and PCV vaccines on childhood meningitis mortality, necessitating use of proxy measures to estimate population impact in LiST. Our analysis indicates that approximately three-quarters of meningitis deaths are preventable with existing Hib and PCV vaccines.

Prevalence of Hepatitis B and Hepatitis C Coinfections in an Adult HIV Centre Population in Gaborone, Botswana

The objective of this study was to assess the prevalence of hepatitis B and hepatitis C coinfections in human immunodeficiency virus (HIV) -infected adults at an HIV center in Gaborone, Botswana. A retrospective review was performed of charts of currently active HIV-infected adult patients in the Family Model Clinic (FMC) of the Botswana-Baylor Childrens Clinical Center of Excellence (BCOE) in Gaborone, Botswana, for the results of serum hepatitis B surface antigen (HBsAg) and antihepatitis C IgG tests performed between January 1, 2005 and December 15, 2009. Of 308 active FMC patients, 266 underwent HBsAg serology testing within the period of study. The HBsAg coinfection prevalence was 5.3% (14/266); 2 of 252 patients had at least one positive antihepatitis C IgG serology, a 0.8% prevalence. Hepatitis B coinfection is relatively common in HIV-infected adults at our center in Botswana, whereas hepatitis C coinfection is rare. In this setting, where the diagnosis of hepatitis B coinfection with HIV has implications for choice of first-line antiretroviral therapy and prevention of perinatal hepatitis B transmission, broader sampling to establish the true population prevalence of hepatitis B coinfection and the desirability of adding screening to HIV management should be considered. These findings provide little justification for adding hepatitis C coinfection screening to the management of HIV infection in Botswana.

Template registration with missing parts: Application to the segmentation of M. tuberculosis infected lungs

Many techniques have been proposed to segment organs from images, however the segmentation of diseased organs remains challenging and frequently requires lots of user interaction. The challenge consists of segmenting an organ while its appearance and its shape vary due to the presence of the disease in addition to individual variations. We propose a template registration technique that can be used to recover the complete segmentation of a diseased organ from a partial segmentation. The usual template registration method is modified in such a way that it is robust to missing parts. The proposed method is used to segment Mycobacterium tuberculosis infected lungs in CT images of experimentally infected mice. Using synthetic data, we evaluate and compare the performance of the proposed algorithm with the usual sum of squared difference cost function.

Probiotics and Fecal Microbiota Transplant for Primary and Secondary Prevention of Clostridium difficile Infection.

Clostridium difficile infection (CDI) is the most common cause of nosocomial diarrhea and is associated with an increased risk of mortality. The use of probiotics and fecal microbiota transplantation (FMT) has been studied to reduce the incidence and severity of this infection, but variable efficacy and safety data have been reported. Probiotics are hypothesized to be effective in the management of CDI through a number of mechanisms that include maintenance of normal gastrointestinal flora, antimicrobial and antitoxin properties, and immunomodulatory effects. Despite promising results in small trials and meta‐analyses, prospective, randomized, controlled trials have not demonstrated probiotics to be effective in the primary prevention of C. difficile–associated diarrhea (CDAD). Probiotics may be effective for secondary prevention in patients with recurrent CDI, but guidelines acknowledge the lack of compelling evidence. Trials are limited by the use of varying types of strains, numbers of strains, and doses of probiotics, as well the definitions of CDI and CDAD. FMT has been proposed as a method for restoring gut microbiota and has been shown to significantly increase the rate of cure in patients with recurrent CDI. Current studies have demonstrated minimal adverse effects, with no reports of transmission of infectious diseases; however, the optimal delivery method, sample preparation, and donor selection remain unclear. In this review, findings from recent literature are highlighted, and guideline recommendations for the use of these agents in the primary and secondary prevention of CDI are summarized.

Adaptation of a general primary care package for HIV-infected adults to an HIV centre setting in Gaborone, Botswana

As life expectancy of HIV‐infected patients improves due to antiretroviral treatment (ART) and the importance of associated co‐morbidities and chronic diseases increases, preventive care will become increasingly important. Adaptation of existing preventive guidelines to local environments will become a priority for HIV treatment programmes.

Impact of Intraoperative Continuous-Infusion Versus Intermittent Dosing of Cefazolin Therapy on the Incidence of Surgical Site Infections after Coronary Artery Bypass Grafting

To determine whether intraoperative continuous‐infusion (CI) cefazolin reduces the incidence of surgical site infections (SSIs) compared with intermittent (INT) cefazolin dosing in patients undergoing coronary artery bypass grafting (CABG) on cardiopulmonary bypass (CPB); safety end points and protocol adherence comparing the two dosing strategies were also explored.

Appropriateness of peripheral parenteral nutrition use in adult patients at an academic medical center

BACKGROUND & AIMS Current evidence and guidelines identify patient populations who may benefit from parenteral nutrition. Peripheral parenteral nutrition (PPN) may be indicated for a subset of patients; however, PPN therapy carries a risk of associated adverse effects. The purpose of this project was to assess appropriateness of current PPN prescribing practices at an academic medical center to determine whether additional guidance and oversight may be beneficial. METHODS Adult patients admitted from August 1, 2015 to November 30, 2015 with at least one order of PPN administered were included. PPN use was evaluated for appropriateness using definitions derived from clinical practice guidelines and standard of practice. Adverse events, including phlebitis and bacteremia, were also examined. RESULTS Of the 159 patients included, 51 (32.1%) received appropriate PPN therapy, in which all four criteria for appropriateness were met. In regards to the criteria for appropriateness, 128 (80.5%) had an appropriate indication, 85 (53.5%) had appropriate time to PPN initiation, 157 (98.7%) had an appropriate duration of therapy, and 112 (70.4%) achieved an appropriate percentage of goal daily calories. In terms of complications associated with PPN therapy, 69 (43.4%) patients had documented phlebitis and bacteremia occurred in 5 (3.1%) of the patients. CONCLUSION During the study period, PPN was appropriately utilized in only one-third of patients and phlebitis occurred in almost half of all patients. Restrictions on PPN prescribing may allow nutrition support clinicians to prospectively evaluate patients to optimize nutrition therapy and minimize the incidence of inappropriate PPN use.