Abstract

The emergence of opportunistic nosocomial bacteria Acinetobacter baumannii, which causes infections in critically ill patients with compromised immune systems, is one of the most clinically challenging pathogens to treat effectively.
Most nosocomial pathogens grow as monoculture or poly-species biofilms in infections and the biofilm mode of existence for A. baumannii may almost certainly contribute to its increased multi-drug resistant (MDR), although resistance can also be attributed to many contributing factors including overuse and misuse of antibiotics in hospitals and the community.
In vitro methods for studying microbial biofilms have developed to include the CDC biofilm reactor, Flow cell devices and MBEC™ but in vivo biofilm model development has been very limited. Few simple animal models are available which reflect either the biofilm nature of growth of pathogens or the treatment of infection influenced by biofilm development in vivo. Biofilm formation is a critical virulence and defence strategy for bacteria, the present study focuses on working towards establishing a biofilm generated in-vivo model to assess the efficacy of antimicrobials against A. baumannii infections.
The present study looks at the effects of broad spectrum antibiotics (BSA) and colistin combinations against lethal planktonic or biofilm A. baumannii infections with a pre-clinical insect model, Galleria mellonella (Greater wax moth larvae). The work shows colistin to be an important synergist both in vitro and in a simple in vivo model. This work is the first to describe a model biofilm associated infection in G. mellonella.