Journal of American Science 2013;9(11s) http://www.jofamericanscience.org 76 Relationship between Clinical and Environmental Isolates of Acinetobacter baumannii in Assiut University Hospitals Enas A. Daef, Ismael S. Mohamad, Ahmad S. Ahmad, Sherein G. El-Gendy, Entsar H. Ahmed and Ibrahim M. Sayed Department of Microbiology and Immunology, Infection Control Unit, Assiut University, Egypt. shereinelgendy@yahoo.com Abstract: This study was conducted during the period from February 2010 to February 2011 to correlate the Acinetobacter baumannii strains isolated from clinical and environmental samples by different methods including biotyping, antibiogram, phenotyping (detection of metallo-B-lactamase enzyme) and also molecular typing throw detection of universal gene of Acinetobacter species. We isolated a total of 51 Acinetobacter species from clinical and environmental samples from different wards and ICUs of Assiut University Hospitals. Biotyping of the isolates were done using API 20NE Index system which identified all clinical & environmental isolatesas Acinetobacter baumannii / calcoaceticus complex. Antimicrobial susceptibility testing was determined by Kirby Bauer disk diffusion method. The highest resistance was to penicillin derivatives (66.7% and 51.9% in clinical and environmental samples respectively). The lowest resistance was to tetracycline (20.8% and 29.6%) and imipenem (29.2% and 33.3% in clinical and environmental samples respectively). Phenotypic detection of Metallo-B- lactamase (MBL) was done by double disc synergy test. All the imipenem resistant Acinetobacter baumannii strains isolated from clinical and environmental samples expressed MBL phenotypically. Molecular typing by PCR showed that 49 of Acinetobacter baumannii isolated from clinical and environmental samples had positive ITS of 602-622bp with an overall sequence similarity of more than96%.These methods supported a close relationship between clinical and environmental isolates and also indicated the important role of hospital environment in spread and transmissibility of multidrug resistant A. baumanii among hospitalized patients. [Enas A. Daef, Ismael S. Mohamad, Ahmad S. Ahmad, Sherein G. El-Gendy, Entsar H. Ahmed and Ibrahim M. Sayed. Relationship between Clinical and Environmental Isolates of Acinetobacter baumannii in Assiut University Hospitals. J Am Sci 2013;9(11s):67-73]. (ISSN: 1545-1003). http://www.jofamericanscience.org. 12 Keywords: A. baumanii, environmental isolates, 16S rRNA-23S rRNA gene. Introduction: Acinetobacter species are saprophytic bacteria found in living organism and inanimate beings. Owing to its scarce virulence, the great majority of infections are in the hospital environment, with great incidence in patients who are seriously ill and even in a critical state (Pedro et al., 2011). Acinetobacter baumannii, a very common hospital pathogen in ICUs and wards, has been identified as one of the six important and highly drug resistant hospital pathogens by the “Infectious Disease Society of America” (Gant et al., 2007). A. baumannii has been isolated from various types of opportunistic infections, including septicemia, pneumonia, endocarditic, meningitis, skin and wound infection, and urinary tract infections (Stapleton, 2002; Zurowska et al., 2008). A number of risk factors have been associated with Acinetobacter nosocomial infections. They include sever underlying diseases, immuno- suppressed hosts, exposure to frequent use of invasive devices and advanced age (Manfredi et al.,2002; Mahgoub et al., 2002). Prolonged hospitalization or ICU stay for 5 days or more appear to be another important risk factor for nosocomial Acinetobacter infections (Infectious Diseases Society of America, 2005). During the last two decades, hospital acquired infections involving multi-resistant A. baumannii isolates have been reported. Once it enters a hospital ward, A. baumannii can spread from the colonized patient to the environment and other susceptible patients. The direct environment of the patient can become contaminated by excreta, air droplets and scales of skin (Zeana et al., 2003). Since then, strains of A. baumanniihave also gained resistance to newly developed antimicrobial drugs. Although multidrug resistant (MDR) A. baumannii is rarely found in the community isolates, it became prevalent in many hospitals (Poirel and Nordmann, 2006). Interpreting the significance of isolates from clinical specimens is often difficult, because of the wide distribution of Acinetobacter species in the nature and its ability to colonize healthy or damaged tissue (Lahiri et al., 2004). Nosocomial Acinetobacter infection is commonly acquired through cross transmission