Evaluating Sensitivity and Resistance Pattern of Cefazolin and Ceftriaxone Against Different Pathogenic Organisms-A Comparative In-Vitro Analysis

Objectives: To evaluate the zone of inhibition and sensitivity pattern of cefazolin and ceftriaxone against selected pathogenic organisms. Methodology: This was an invitro experimental study that was conducted on clinical isolates of Escherichia coli, Klebsiella spp., Proteus spp., Pseudomonas aeruginosa and Staphylococcus aureus from urine and pus samples. These samples were collected from four pathological laboratories in Karachi and tested against two commonly used cephalosporins; cefazolin and ceftriaxone from the period of 1st January-27th February 2011. The resistant pattern was determined by disc diffusion method (Kirby-Bauer test). The data was analyzed by Statistical Package for Social Sciences version 19. Mean +/- SD used for continuous measurements whereas frequencies and percentages were used for categorical variables. Independent sample t-test was applied to see antibiotic sensitivity pattern in urine and pus samples. Results: The results of this study reveal that Escherichia coli are the most common uropathogen that was present in more than 35% of samples. The zone of inhibition of Ceftriaxone is greater than Cefazolin for all types of clinical isolates. Moreover, the sensitivity pattern of Ceftriaxone for all the clinical isolates was greater 90.25%, 85.72%, 100%, 75% and 85% to Escherichia coli, Klebsiella spp., Proteus spp., Pseudomonas aeruginosa, Staphylococcus aureus respectively than does Cefazolin. The pathogenic organisms present in urine were more susceptible to ceftriaxone. The p-value obtained after applying independent sample t-test for ceftriaxone was 0.012. Therefore, a significant difference in the sensitivity pattern of ceftriaxone for pathogens present in urine and pus samples. Conclusion: Ceftriaxone is more effective than cefazolin in most of the cases and there is clear difference in their zone of inhibition. Moreover, resistance to cefazolin develops more easily than for Ceftriaxone. Continuous surveillance, public awareness and health care education can decrease the irrational use of these antibiotics.