Horizontal gene transfer (HGT) has long been recognized as an important source of genetic diversity. In the clinical setting, HGT plays an important role in the spread of antibiotic resistance genes and has the ability to turn easily treatable infections by common organisms like E. coli into untreatable, life-threatening conditions. Carbapenem-resistance, often mediated by plasmids carrying the blaKPC gene, is a worldwide threat. Although evidence-based guidelines to prevent transmission of carbapenemase-producing organisms (CPO) exist, they don't explicitly take into account HGT; which may complicate tracking nosocomial transmission. Here I'll present clinical investigations that underscore the consequences of HGT.

First, I'll present a study that tracked the long-term colonization of patients from a 2011 K. pneumoniae outbreak have remained consistently colonized with CPOs. Analysis of isolates collected from these patients revealed a complex network of plasmids, plasmid rearrangements and evidence of strain succession and re-emergence. Then I'll describe a study conducted at our hospital, where broad-range environmental sampling was conducted, including housekeeping closets, wastewater from hospital internal pipes, and external manholes. Whole-genome sequencing and analysis of 108 carbapenem-resistant isolates was compared to five years of patient isolates. We identified a vast, underappreciated reservoir of CPOs and identified a number of putative transmission links between patients and the environment. 

Learning Objectives: 

1. Understand the importance of horizontal gene transfer for the spread of antibiotic resistance
2. Appreciate the diversity of antibiotic resistance plasmids in environmental reserviors