Acinetobacter baumannii is a Gram negative, obligate aerobe, coccobacillus and one of the most prevalent causes of nosocomial infections. With only a limited number of “traditional” virulence factors, the mechanisms contributing to the success of this pathogen are of increasing interest to researchers and clinicians alike. During previous investigations we have shown the putative lactate metabolism operon is significantly upregulated during an in vivo systemic infection. Therefore, to understand the contribution of lactate metabolism to bacterial physiology and pathogenesis, we investigated the role of the lactate permease, lldP, in the contemporary A. baumannii clinical strain AB5075-UW, using a transposon disrupted mutant acquired from the Manoil A. baumannii mutant library. As part of our study we have engineered two plasmid vectors for complementation, through modification of the A. baumannii expression vector pBASE, to encode either tellurite or hygromycin resistance cassettes, respectively. Using a multifaceted approach, combining traditional microbiology, molecular techniques and virulence assessments we have confirmed lldP is responsible for lactate metabolism in vitro. In addition, we have shown that the elevated expression observed previously in vivo is not strain specific, and is a phenotype conserved across multiple strains, whereby disruption of this pathway results in attenuation during a murine systemic in vivo competition assay. Our study provides both molecular resources for the Acinetobacter community in the form of two new expression vectors for use with multidrug resistant A. baumannii strains, in addition to advancing our understanding of the molecular and biochemical mechanisms responsible for the success of this pathogen in vivo.