Background: Spontaneous bacterial peritonitis is the most frequent infection complicating liver cirrhosis. Recent changes in bacterial ecology and emerging antibiotic resistance have resulted in failure to respond to empirical therapy with 3rd generation cephalosporin in 33%-75% of cases and such failure is associated with reduced survival. Aim of the work: To identify the causative bacteria of community acquired and nosocomial SBP and their antimicrobial resistance patterns in an attempt to perform a local bacteriological surveillance to optimize empirical treatment. Patients and methods: Three hundred patients with ascites due to liver cirrhosis were enrolled in this study. All patients were subjected to history taking, clinical examination, ascitic fluid analysis, culture and ultrasonography. SBP was diagnosed by ascitic PNL >250/mm3. Results: One hundred and eighty-five patients (61.7%) were diagnosed as SBP. Community acquired SBP (83.8%) was more common than nosocomial SBP (16.2%). One hundred and forty patients (75.7%) had culture positive, and 45 patients (24.3%) had culture negative SBP. Gram positive (G+) cocci (64.3%) were more common than Gram negative (G-) bacilli (35.7%). Among culture positive cases, 110 patients had community-acquired and 30 patients had nosocomial SBP. The overall cefotaxime resistance was 44.4%; being higher in nosocomial (100%) than community acquired group (37.5%). No resistance to ampicillin/salbactam, piperacillin/tazobactam, vancomycin, linezolid, meropenem or tigecyclin was identified. Conclusion: There is an emerging pattern towards G+ bacteria and 3rd generation cephalosporins resistance in the causative bacteria of SBP especially nosocomial type while piperacillin/tazobactam, vancomycin, linezolid, meropenem or tigecycline still can be used in resistant cases.