Sensitivity of Staphylococcus Aureus to cephalothin and oxacillin in patients with secondary Sjogren’s syndrome assessed by E-Test method

Abstract

Purpose:  Sjogren’s syndrome is a systemic autoimmune disease that causes severe dry mouth leading to acute infection of parotid gland with methicillin resistant Staphylococcus Aureus (MRSA). Methicillin resistant antibiotics and first generation cephalosporins, both, have been suggested as the treatment of choice for this condition, yet there is no study that has compared the efficacy of these antibiotics to introduce the more effective one. The purpose of this study is to  compare the sensitivity of Staphylococcus Aureus (SA) to cephalothin and oxacillin in patients with secondary Sjogren’s syndrome by E-Test.

Material and Method: This study was conducted on 62 patients with secondary Sjogren’s syndrome referred from a rheumatologist. Sampling was done from the right parotid gland and the samples were sent to the lab within 2 hours. After the microbial lab procedures (culture, isolation and SA identification), Minimum Inhibitory Concentration (MIC) was measured in each sample for both cephalothin and oxacillin by using E-Test. Positive samples for SA were collected and then coded. The data were analyzed by SPSS and Paired T-Test. We also compared MIC50 and MIC90 (MICs required to inhibit the growth of 50% and 90% of organisms, respectively) for these two antibiotics. 

Result: SA was isolated from 30 patients (48%). The difference between the average MIC antibiotic sensitivity across these two antibiotics was significant (P=0.001). The correlation coefficient between variables was 0.821, which was significant (P<0.0001). MIC50 for oxacillin was higher than the value for cephalothin. The same was observed for MIC90. 

Conclusion: The average MIC in oxacillin was greater than cephalothin. In other words, oxacillin was more effective than cephalothin.