ABSTRACT
beta-lactame antibiotics are very important in the cure of diseases, beta-lactamase as a virulence agent causes resistance to these antibiotics. Existence of beta-lactamase in the pathogen bacteria can cause delay in the treatment. The aim of this research was to compare the frequency of beta-lactamase enzyme existence in different types of isolated nosocomial infection bacteria in Alzahra hospital, Isfahan, Iran. This laboratory study was performed in Alzahra hospital of Isfahan in 2005-2006. According to sample size estimation, 100 infection samples [blood, urine, skin] were randomly selected. Identification of bacteria was performed using microbiological methods; such as: staining, chemical test, and use of differential and selective media. To determine beta-lactamase production in bacteria, acidimetric method was used. Data was analyzed using descriptive statistics. From the 100 isolated pathogen bacterias, 68.45% produced beta-lactamase; 83.33% produced Staphylococcus spp. 70.95% produced Enterobacteriaceae spp. and 18.8% produced Pseudomonas 18.8%. Based on the results, the frequency of beta-lactamase Enzyme existence in isolated bacteria of nosocomial infection was very high, which can be due to the increase of resistance of beta-lactam antibiotics in pathogen Bacteria