Acinetobacter baumannii causes hospital infections and negatively impacting patient outcome. A. baumannii is characterized by its exceptional ability to acquire multidrug resistance and spread among hospitalized patients. The rate of resistance to carbapenems in A. baumannii has now exceeded 40% in the U.S. Carbapenem- resistant strains are frequently resistant to all other agents except colistin. Infections due to these organisms are treated with colistimethate (prodrug of colistin) alone or in combination with another antimicrobial agent. However, the increased use of colistin has resulted in the emergence of colistin-resistant A. baumannii. Colistin interacts with the lipid A moiety of lipopolysaccharide and causes disorganization of the membrane. Modification of lipid A with phosphoethanolamine has been proposed as playing a key role in colistin resistance in A. baumannii. Findings from laboratory-generated colistin-resistant mutant strains suggest that this modification carries substantial fitness cost and impairs virulence. However, a subset of patients with colistin- resistant A. baumannii suffer prolonged infection and high mortality. This suggests that colistin-resistant clinical strains have additional mechanisms, which enable them to remain virulent and survive in the human hosts. Our collection of paired colistin-susceptible and -resistant clinical strains from same patients provides us with an unparalleled opportunity to define clinically relevant mechanisms of resistance, fitness and virulence, and their implications for the diagnosis and treatment of colistin-resistant A. baumannii. The central hypotheses to be tested are: (1) lipid A modification is the predominant mechanism of resistance to colistin and can be exploited for rapid diagnosis of resistance, (2) fitness and virulence of colistin-resistant A. baumannii is variable and dependent on the specific mechanism of resistance, and (3) combinations of antimicrobial agents have unique activity against colistin-resistant A. baumannii. To test these hypotheses, we plan to conduct the following Specific Aims: (1) Elucidate the lipid A structures associated with colistin resistance, (2) Characterize the fitness and virulence potential of colistin-resistant A. baumannii and the activity of antimicrobial combinations in in vitro and in vivo models, and (3) Define the genomic and proteomic correlates of colistin resistance. In addition to the existing colistin-resistant clinical strains,those collected prospectively from three hospitals with diverse epidemiology will also be studied, enhancing the generalizability of the findings. The study aims to elucidate the mechanisms of colistin resistance in A. baumannii that are relevant to clinical settings using a multifaceted yet integrated approach. The findings will substantially enhance our understanding of the biology of colistin-resistant A. baumannii, and contribute in devising both novel diagnostic and therapeutic approaches to improve the care of severely ill patients affected by this otherwise untreatable organism.

Public Health Relevance

Acinetobacter baumannii has become a common cause of hospital-acquired infection in the U.S. Colistin is an antibiotic reserved for treatment of infectin from A. baumannii which has become resistant to all other antibiotics. Development of resistance to colistin is therefore a major problem in treating patients infected with A. baumannii Utilizing an extensive collection of colistin-resistant A. baumanni strains identified from patient, this study will investigate the mechanisms underlying resistance to colistin and aim to apply the findings to improve diagnosis and treatment of this infection.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI104895-03
Application #
8997435
Study Section
Drug Discovery and Mechanisms of Antimicrobial Resistance Study Section (DDR)
Program Officer
Huntley, Clayton C
Project Start
2014-03-15
Project End
2019-02-28
Budget Start
2016-03-01
Budget End
2017-02-28
Support Year
3
Fiscal Year
2016
Total Cost
Indirect Cost
Name
University of Pittsburgh
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Ballaben, Anelise S; Andrade, Leonardo N; Galetti, Renata et al. (2018) Diversity of High-Level Aminoglycoside Resistance Mechanisms among Gram-Negative Nosocomial Pathogens in Brazil. Antimicrob Agents Chemother 62:
Hazen, Tracy H; Mettus, Roberta; McElheny, Christi L et al. (2018) Diversity among blaKPC-containing plasmids in Escherichia coli and other bacterial species isolated from the same patients. Sci Rep 8:10291
Tran, Thien B; Wang, Jiping; Doi, Yohei et al. (2018) Novel Polymyxin Combination With Antineoplastic Mitotane Improved the Bacterial Killing Against Polymyxin-Resistant Multidrug-Resistant Gram-Negative Pathogens. Front Microbiol 9:721
Hazen, Tracy H; Mettus, Roberta T; McElheny, Christi L et al. (2018) Draft Genome Sequences of blaKPC-Containing Enterobacter aerogenes, Citrobacter freundii, and Citrobacter koseri Strains. Genome Announc 6:
Mustapha, Mustapha M; Li, Bin; Pacey, Marissa P et al. (2018) Phylogenomics of colistin-susceptible and resistant XDR Acinetobacter baumannii. J Antimicrob Chemother 73:2952-2959
Lucas, Aaron E; Ito, Ryota; Mustapha, Mustapha M et al. (2018) Frequency and Mechanisms of Spontaneous Fosfomycin Nonsusceptibility Observed upon Disk Diffusion Testing of Escherichia coli. J Clin Microbiol 56:
Leung, Lisa M; Cooper, Vaughn S; Rasko, David A et al. (2017) Structural modification of LPS in colistin-resistant, KPC-producing Klebsiella pneumoniae. J Antimicrob Chemother 72:3035-3042
Barker, William T; Martin, Sara E; Chandler, Courtney E et al. (2017) Small molecule adjuvants that suppress both chromosomal and mcr-1 encoded colistin-resistance and amplify colistin efficacy in polymyxin-susceptible bacteria. Bioorg Med Chem 25:5749-5753
Jiménez, Adriana; Castro, José G; Munoz-Price, L Silvia et al. (2017) Outbreak of Klebsiella pneumoniae Carbapenemase-Producing Citrobacter freundii at a Tertiary Acute Care Facility in Miami, Florida. Infect Control Hosp Epidemiol 38:320-326
Iovleva, Alina; Doi, Yohei (2017) Carbapenem-Resistant Enterobacteriaceae. Clin Lab Med 37:303-315

Showing the most recent 10 out of 53 publications