Exploring multidrug-resistant Acinetobacter baumannii toxicity in Caenorhabditis elegans

Acinetobacter baumannii is a gram-negative, opportunistic human pathogen that has been shown to cause nosocomial infections that exhibit multidrug resistant characteristics in immunocompromised patients. The occurrence of infection caused by A. baumannii has increased from 1.5% of hospital-acquired pneumonia cases in 1975 to 6.9% in 2003. In order to understand the mechanisms associated with multidrug resistant bacterial infections, the nematode Caenorhabditis elegans has been used to study in vivo responses to bacterial infection and treatment. In this study, we are exploring the model system, C. elegans, to study the efficiency of treatments for multidrug resistant A. baumannii strains.  To develop a model, A. baumannii toxicity in C. elegans was tested via the killing assay. The killing assay consists of scoring for nematode survival over the course of several days while the C. elegans population ingests three strains of A. baumannii (A14, 19606, A118), each harboring a different drug-resistant profile, and the nonpathogenic bacterium, Escherichia coli OP50-1, separately. Independent trials show that after approximately 150 hours of exposure to each bacterial strain, A. baumannii A14 and 19606 significantly infects and kills C. elegans. Further trials will determine which of the three strains has the most toxic effect on C. elegans. Once a strain is identified, we will test the efficiency of A. baumannii drug treatments by introducing a series of drugs into the infected C. elegans population, and score for nematode survival.