261. Plasmid-Mediated Multidrug-resistance in Gram-Negative Bacteria Isolated from a New Hospital in Iraq
Session: Poster Abstract Session: Antimicrobial Susceptibility and Resistance
Friday, October 21, 2011
Room: Poster Hall B1
Background: Multi, extensively, and pandrug resistant (MDR) Gram negative bacteria such as A. baumannii-calcoaceticus complex (ABC), Escherichia coli, and Klebsiella spp are increasing common causes of infections in the Military Health System. Plasmid-mediated transfer plays an important role for the dissemination of antibiotic resistance in Gram negative bacteria. In this study, we investigated and evaluated the impact of the plasmids harbored in above bacteria on drug resistance.

Methods: Thirty-two MDR and 43 non-MDR Gram negative bacteria strains isolated from patients, personnel and environmental surfaces in a new CSH in Iraq underwent antimicrobial susceptibility test (AST), plasmid profile analysis and plasmid transformation assays to characterize the relationship between the plasmids and phenotypic antimicrobial resistance. Ampicillin, gentamicin, tobramicin and ceftazidime were added to the LB agar plates for antibiotics selection test. Fisher’s Exact Test was used for statistical significance.

Results: MDR E. coli and K. pneumonia isolates harbored significantly more (three or more) plasmids compared to their non-MDR counterparts, which carried less than two plasmids or none (p <0.01). Plasmids from 16 representative MDR bacteria including E. coli, K. pneumonia conferred resistance to 2 or more classes of antibiotics when transferred to a commercially purchased susceptible competent E. coli. Various large plasmids (~70kb) from these Gram negative bacteria were confirmed carrying resistant genes by the transformation assay and antibiotics selection test. The transformation assay and antibiotic selection test also revealed that the antibiotic genes can be located on different large plasmids harbored in the same host strain.

Conclusion: Plasmids significantly impacted antimicrobial resistant in this specific group of Gram negative bacteria. The large plasmids carrying the resistant genes instead of the smaller plasmid may be the major causes for the drug resistance in this group of Gram negative bacteria and can be a potential factor for dissemination of the resistance through genetic horizontal transfer.

Subject Category: A. Antimicrobial agents and Resistance

Xiaozhe Huang, PhD1, Mohamad Chahine, MD1, Julie Ake, MD, MSc2, Melissa Barber, AS, MLT (AMT)3 and Emil Lesho, DO4, (1)Walter Reed Army Institute of Research, Silver Spring, MD, (2)Walter Reed Army Medical Center, Washington, DC, (3)Infectious Diseases Clinical Research Program, Washington, DC, (4)WRAIR, Silver Spring, MD


X. Huang, None

M. Chahine, None

J. Ake, None

M. Barber, None

E. Lesho, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.