Background: Nosocomial infections are the most important challenge in the health system, due to the mortality and economic costs. The aim of this study was to evaluate the epidemiology of nosocomial infections and determine antibiotic resistance patterns.
Materials and Methods: This retrospective descriptive study was carried out on the medical records of 738 patients hospitalized in Poursina Hospital from April 2013 to September 2015.  The kind of nosocomial infection, its causes and antibiotic resistance patterns were gathered.  All data was entered in SPSS 16 and analyzed by descriptive tests.
Results: 62.6% of patients were male. The most common cause of a nosocomial infection was Acinetobacter (24.66%) and the lowest bacterial infection was observed with Klebsiella (21 %.). Urinary tract infections were the most commonly reported nosocomial infection (35.2%). Acinetobacter had the most resistance (98.48%) to Cefazolin and the least resistance (57.14%) to Tobramycin. Staphylococcus aureus had the most resistance (75.2%) to Amoxicillin and the least resistance (6.12%) to Vancomycin. E. coli had the most resistance (74.33%) to Ampicillin and the least resistance (8.86%) to Nitrofurantoin. Enterobacter had the most resistance (96.87%) to Cephalexin and the least resistance (41.37%) to Meropenem. Klebsiella had the most resistance (90.19%) to Ampicillin and the least resistance (21.5%) to Amikacin. Pseudomonas had the most resistance (98%) to Cefazolin and the least resistance (22.22%) to Meropenem. 
Conclusion: Recognition and timely detection of antibiotic resistance, and the proper use of antibiotics to reduce drug resistance are the most important principles that should be followed when selecting antibiotics