Comparison of Susceptibility Testing of E-test Strips with Cefoxitin and Oxacillin Disks in Identification of Methicillin-resistant Staphylococcus saprophyticus Strains

Over the years, Staphylococcus saprophyticus, in addition to becoming a serious pathogen, has become resistant to a wide range of antibiotics. Offering an inexpensive, rapid, and available method for identification of resistant bacteria can prevent the spread of infections caused by these bacteria. The aim of this study was to compare susceptibility testing of E-test strips with cefoxitin and oxacillin disks in identification of methicillin-resistant Staphylococcus saprophyticus strains in clinical samples.
In this study, 590 isolates of Staphylococcus saprophyticus were isolated from different parts of treatment centers in Zahedan city. After confirmation of the genus of isolates, resistance to methicillin, was defined in 262 samples using cefoxitin 30 μg and oxacillin 1 μg antibiotic disks. To determine minimum inhibitory concentration, E-test strips and cefoxitin and oxacillin disks, were used. The mecA gene was identified by PCR and considered as gold standard.
Sensitivity of the test performed for cefoxitin and oxacillin antibiotics in the disk diffusion method, was 89.09% and 68.81%, respectively, and in the minimum inhibitory concentration, was 98.18% and 97.27%, respectively. Out of 262 samples, 110 were identified to be resistant to methicillin based on PCR assay.
According to the findings of this study, oxacillin antibiotic disk showed acceptable sensitivity to determine methicillin-resistant Staphylococcus saprophyticus strains. Also, the methods based on the use of E-Test strips had the highest sensitivity and specificity.