Antibiotic Resistance, Biofilms and Quorum Sensing in Acinetobacter Species

Acinetobacter is a Gram-negative coccobacillus that is strictly aerobic, nonmotile, catalase positive and oxidase negative. It is ubiquitous in nature, being found in soil and water. Members of the genus Acinetobacter have now clearly emerged as opportunistic nosocomial pathogens (Forster et al., 1998). Bacteremia, pneumonia, meningitis, urinary tract and surgical wound infections are the most common infections caused by this organism (Cisneros et al., 2002; Dijkshoorn et al., 2007). The taxonomy of the genus Acinetobacter has undergone extensive revision during the last two decades, and at least 31 named and unnamed species have now been described (Dijkshoorn et al., 2007). Of these, Acinetobacter baumannii and the closely related unnamed genomic species 3 and 13 sensu Tjernberg and Ursing (13TU) species were the most clinically relevant. In recent years, multidrug-resistant (MDR) A. baumannii are increasingly held responsible for nosocomial infections and MDR A. baumannii clones are spreading into new geographic areas with increasing number of strains acquiring many resistance genes (Navon venezia et al., 2005). Unfortunately, newer extended-spectrum ┚-lactamases and different carbapenemases are emerging fast, leading to pan-resistant strains of A. baumannii.