Abstract

Horizontal gene transfer (HGT) plays a major role in the spread of antibiotic resistance. Of particular concern are Acinetobacter baumannii bacteria, which recently emerged as global pathogens, with nosocomial mortality rates reaching 19-54% (Centers for Disease Control and Prevention, 2013; Joly Guillou, 2005; Talbot et al., 2006). Acinetobacter gains antibiotic resistance remarkably rapidly (Antunes et al., 2014; Joly Guillou, 2005), with multi drug-resistance (MDR) rates exceeding 60% (Antunes et al., 2014; Centers for Disease Control and Prevention, 2013). Despite growing concern (Centers for Disease Control and Prevention, 2013; Talbot et al., 2006), the mechanisms underlying this extensive HGT remain poorly understood (Adams et al., 2008; Fournier et al., 2006; Imperi et al., 2011; Ramirez et al., 2010; Wilharm et al., 2013). Here, we show bacterial predation by Acinetobacter baylyi increases cross-species HGT by orders of magnitude, and we observe predator cells functionally acquiring adaptive resistance genes from adjacent prey. We then develop a population-dynamic model quantifying killing and HGT on solid surfaces. We show DNA released via cell lysis is readily available for HGT and may be partially protected from the environment, describe the effects of cell density, and evaluate potential environmental inhibitors. These findings establish a framework for understanding, quantifying, and combating HGT within the microbiome and the emergence of MDR super-bugs.

Highlights

  • The spread of antibiotic resistance among pathogenic microbes is a major and growing threat to public health

  • After 3 hr, Acinetobacter had lysed a large number of E. coli cells, and multiple independent Horizontal gene transfer (HGT) events were visible within the device’s approximately 104 um2 traps (Figure 1b–d)

  • Humanity’s dwindling arsenal of antibiotics is a significant and growing concern. This threat stems from pathogens such as Acinetobacter that are able to rapidly accumulate multiple resistance genes, which can make them nearly impossible to treat

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Summary

Introduction

The spread of antibiotic resistance among pathogenic microbes is a major and growing threat to public health. Gram-negative Acinetobacter spp. are a worrisome example - these bacteria thrive in hospital settings, causing around 9% of nosocomial infections, in the respiratory tract (Joly-Guillou, 2005). This prevalence, combined with high levels of antibiotic resistance (Antunes et al, 2014), has led the Infectious Diseases Society of America to designate Acinetobacter baumanii one of six problematic multidrug-resistant (MDR) pathogens (Talbot et al, 2006) and the US Centers for Disease Control to assign it threat level ‘Serious’ (Centers for Disease Control and Prevention (CDC), 2013).

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