Jundishapur J Microbiol. 2013 October; 6(8): e9892. DOI: 10.5812/jjm.9892 Published online 2013 October 1. Research Article Nosocomial Outbreak of Extensively and Pan Drug-Resistant Acinetobacter baumannii in Tertiary Hospital in Central Part of Iran Alireza Japoni-Nejad 1,2 , Masoomeh Sofian 3,4 , Alex van Belkum 5,6 , Ehsanollah Ghaznavi-Rad 2,7,* 1 Student Research Committee, Arak University of Medical Sciences, Arak, IR Iran 2 Department of Microbiology and Immunology, Faculty of Medicine, Arak University of Medical Sciences, Arak, IR Iran 3 Department of Infectious Disease, Arak University of Medical Sciences, Arak, IR Iran 4 Tuberculosis and Pediatric Infectious Research Center, Arak University of Medical Sciences, Arak, IR Iran 5 Department of Medical Microbiology and Infectious Diseases Erasmus MC, Rotterdam, The Netherlands 6 Unit Microbiology, R&D Microbiology, BioMerieux, France 7 Molecular and Medicine Research Center, Department of Microbiology, School of Medicine, Arak University of Medical Sciences, Arak, IR Iran *Corresponding author: Ehsanollah Ghaznavi-Rad, Department of Microbiology and Immunology, Faculty of Medicine, Arak University of Medical Sciences, Arak, IR Iran. Tel: +98- 8614173526, E-mail: e.ghaznavirad@arakmu.ac.ir, ghaznaviehs@yahoo.com. Received: December 26, 2012; Revised: February 20, 2013; Accepted: March 10, 2013 Background: Acinetobacter baumannii has emerged as a cause of nosocomial infections in hospitalized patients, particularly in intensive care units. Carbapenems are a common choice for treating nosocomial infections caused by A. baumannii strains. Increasing antimicrobial resistance among Acinetobacter isolates has been documented and multidrug-resistant A. baumannii is recognized to be among the most difficult antimicrobial-resistant bacilli to control and treat. Objectives: This study describes carbapenem resistance in A. baumannii isolates obtained during an outbreak from intensive care units of a peripheral hospital in central part of Iran. Patients and Methods: Sixty-three non-repetitive A. baumannii isolates were collected over a six months period. Susceptibility of the isolated bacteria to a panel of 23 different antimicrobial agents was defined by using the standard disk diffusion method. Production of Metallo-β-lactamases (MBL) and AmpC β-lactamase were determined by using the E-test MBL strip and AmpC disk tests, respectively. Results: The present study indicates that carbapenems and new cephalosporin antibiotics were practically ineffective against the extensive drug resistance (XDR) strains. Colistin was observed to be more effective, although in seven cases resistance to colistin observed. AmpC β-lactamase and MBL could be an important contributory factor for imipenem resistance among the isolates in our hospital. The elevated prevalence of XDR and pan drug resistance (PDR) strains indicates that local antibiotic prescription policies should be revised and infection control should be improved. Conclusions: The elevated prevalence of XDR and PDR strains indicates that local antibiotic prescription policies should be revised and infection control should be improved. Keywords: Acinetobacter baumannii; Nosocomial Infection; PDR; XDR Implication for health policy/practice/research/medical education: This data will be helpful for infection control committee of the hospital in developing strategy to limit the frequency of this microorganism. Copyright © 2013, Ahvaz Jundishapur University of Medical Sciences; Published by Kowsar Corp. This is an open-access article distributed under the terms of the Cre- ative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1. Background Acinetobacter baumannii is currently considered to be one of the most important Gram-negative bacteria caus- ing infections in immunecompromised patients, mainly hospitalized in intensive care units (1). A. baumannii is considered to be responsible for 2 - 10% of all Gram-nega- tive bacterial infections of patients in intensive care units in Europe and the United States (2). Infection due to A. baumannii has become a significant challenge for healthcare systems. Several associated mechanisms with carbapenem resistance have been de- scribed in A. baumannii, including metallo B-lactamases (MBLs), carbapenem-hydrolysing oxacillinases, de- creased permeability due to the loss of outer membrane proteins (OMPs), overexpression of efflux pumps and hy- perproduction of AmpC B-lactamases (3). The terms pan drug resistance (PDR), extensive drug resistance (XDR), and multidrug resistance (MDR) are explained, respec- tively, resistance of a pathogen to all, resistance to all ex- pect 1 or 2, and resistance to ≥ 3 classes of antimicrobial agents (4). 2. Objectives The purpose of the present study was to investigate an- tibiotic susceptibility profile and the rate of XDR or PDR A. baumannii isolated from clinical and environmental specimens of intensive care units of central teaching hos- pital of Arak University located in center of Iran. 3. Patients and Methods The outbreak occurred in the 350-bed central teaching hospital of Arak University of Medical Sciences in the central part of Iran and a total of 63 non-duplicate A. bau- mannii isolates were collected from clinical and environ-