Prevalence and antimicrobial resistance patterns of nosocomial pathogens causing surgical site infections in an Egyptian university hospital Background: Surgical site infections (SSI) are a common type of health care associated infections. The emergence of multidrug resistant (MDR) nosocomial pathogens represents a major health burden. This study was conducted to determine the frequency of isolation and patterns of antimicrobial resistance of nosocomial pathogens causing SSI in Zagazig University Hospitals Methods: Samples obtained from the infected surgical wounds were subjected to microbiological identification and antibiotic susceptibility testing. The role of extended spectrum beta lactamase (ESBL) and carbapenemase in bacterial resistance to some antibiotic were evaluated. Results: The most frequently isolated species were S. aureus (31%) followed by Klebsiella pneumoniae (K. pneumonia) (22%), Escherichia coli (E. coli) (15%), Pseudomonas aeruginosa (P. aeruginosa) (11%), Coagulase negative staphylococci (CoNs) (8%), Proteus spp (7%) and Acinetobacter spp (6%). Methicillin resistance was detected in 38 (97 %) and 8(80 %) of S. aureus and CoNs isolates, respectively. Among Gramnegative organisms, 65.8% of isolates were ESBL producers, of which 60% were Carbapenem resistant. Metallo-β-lactamase was detected in 30% of Gram-negative isolates. Multi-drug resistance was observed in 50 isolates (68.5%), whereas extensively drug resistance (XDR) occurred in 23(31.5%) of Gram-negative isolates. Conclusions: Most of Gram-negative isolates were MDR or XDR. Antibiotic therapy of SSI must be guided by microbiological culture and antibiotic sensitivity testing. Infection prevention and control practice needs more improvement. Rationalization of antibiotic prescription must be carried out. Post discharge surveillance of SSI needs to be considered.