How inkjet printing technology can defeat multidrug-resistant pathogens

Background The rapid global spread of multi-resistant bacteria and loss of antibiotic effectiveness increases the risk of initial inappropriate antibiotic therapy (IAT) and poses a serious threat to patient safety. We conducted a systematic review and meta-analysis of published studies to summarize the effect of appropriate antibiotic therapy (AAT) or IAT against gram-negative bacterial infections in the hospital setting. Methods MEDLINE, EMBASE, and Cochrane CENTRAL databases were searched until May 2014 to identify English-language studies examining use of AAT or IAT in hospitalized patients with Gram-negative pathogens. Outcomes of interest included mortality, clinical cure, cost, and length of stay. Citations and eligible full-text articles were screened in duplicate. Random effect models meta-analysis was used. Results Fifty-seven studies in 60 publications were eligible. AAT was associated with lower risk of mortality (unadjusted summary odds ratio [OR] 0.38, 95 % confidence interval [CI] 0.30-0.47, 39 studies, 5809 patients) and treatment failure (OR 0.22, 95 % CI 0.14–0.35; 3 studies, 283 patients). Conversely, IAT increased risk of mortality (unadjusted summary OR 2.66, 95 % CI 2.12–3.35; 39 studies, 5809 patients). In meta-analyses of adjusted data, AAT was associated with lower risk of mortality (adjusted summary OR 0.43, 95 % CI 0.23–0.83; 6 studies, 1409 patients). Conversely, IAT increased risk of mortality (adjusted summary OR 3.30, 95 % CI 2.42–4.49; 16 studies, 2493 patients). A limited number of studies suggested higher cost and longer hospital stay with IAT. There was considerable heterogeneity in the definition of AAT or IAT, pathogens studied, and outcomes assessed. Discussion Using a large set of studies we found that IAT is associated with a number of serious consequences,including an increased risk of hospital mortality. Infections caused by drug-resistant, Gram-negative organisms represent a considerable financial burden to healthcare systems due to the increased costs associated with the resources required to manage the infection, particularly longer hospital stays. However, there were insufficient data that evaluated AAT for the outcome of costs among patients with nosocomialGram-negative infections. Conclusions IAT in hospitalized patients with Gram-negative infections is associated with adverse outcomes. Technological advances for rapid diagnostics to facilitate AAT along with antimicrobial stewardship, surveillance, infection control, and prevention is needed. Electronic supplementary material The online version of this article (doi:10.1186/s12879-015-1123-5) contains supplementary material, which is available to authorized users.

With rapid emergence of multidrug-resistant bacteria, there is often a need to perform susceptibility testing for less commonly used or newer antimicrobial agents. Such testing can often be performed only by using labor-intensive, manual dilution methods and lies outside the capacity of most clinical labs, necessitating reference laboratory testing and thereby delaying the availability of susceptibility data. To address the compelling clinical need for microbiology laboratories to perform such testing in-house, we explored a novel, automated, at-will broth microdilution-based susceptibility testing platform. Specifically, we used the modified inkjet printer technology in the HP D300 digital dispensing system to dispense, directly from stock solutions into a 384-well plate, the 2-fold serial dilution series required for broth microdilution testing. This technology was combined with automated absorbance readings and data analysis to determine MICs. Performance was verified by testing members of the Enterobacteriaceae for susceptibility to ampicillin, cefazolin, ciprofloxacin, colistin, gentamicin, meropenem, and tetracycline in comparison to the results obtained with a broth microdilution reference standard. In precision studies, essential and categorical agreement levels were 96.8% and 98.3%, respectively. Furthermore, significantly fewer D300-based measurements were outside ±1 dilution from the modal MIC, suggesting enhanced reproducibility. In accuracy studies performed using a panel of 80 curated clinical isolates, rates of essential and categorical agreement and very major, major, and minor errors were 94%, 96.6%, 0%, 0%, and 3.4%, respectively. Based on these promising initial results, it is anticipated that the D300-based methodology will enable hospital-based clinical microbiology laboratories to perform at-will broth microdilution testing of antimicrobials and to address a critical testing gap.

Legionella pneumophila is a Gram-negative opportunistic human pathogen that causes a severe pneumonia known as Legionnaires' disease. Notably, in the human host, the organism is believed to replicate solely within an intracellular compartment, predominantly within pulmonary macrophages. Consequently, successful therapy is predicated on antimicrobials penetrating into this intracellular growth niche. However, standard antimicrobial susceptibility testing methods test solely for extracellular growth inhibition. Here, we make use of a high-throughput assay to characterize intracellular growth inhibition activity of known antimicrobials. For select antimicrobials, high-resolution dose-response analysis was then performed to characterize and compare activity levels in both macrophage infection and axenic growth assays. Results support the superiority of several classes of nonpolar antimicrobials in abrogating intracellular growth. Importantly, our assay results show excellent correlations with prior clinical observations of antimicrobial efficacy. Furthermore, we also show the applicability of high-throughput automation to two- and three-dimensional synergy testing. High-resolution isocontour isobolograms provide in vitro support for specific combination antimicrobial therapy. Taken together, findings suggest that high-throughput screening technology may be successfully applied to identify and characterize antimicrobials that target bacterial pathogens that make use of an intracellular growth niche.