Assessment of The Imipenem Antibiotic Effects on The Expression of Staphylococcus Saprophyticus Serine-Aspartate Repeat Protein-Encoding Genes Isolated from Clinical Cases

Staphylococcus saprophyticus is one of the most common causes of urinary tract infections (UTIs). Antibiotic resistance against imipenem is increasing worldwide. Our study aimed to investigate the effect of imipenem on expression of the S. saprophyticus serine-aspartate repeat proteinencoding genes by isolating multidrug-resistant strains.

In this descriptive study, 500 specimens were randomly collected from clinical specimens. Firstly, isolates were identified using standard tests. Then, S. saprophyticus species harboring sdrC, D and E genes were detected using multiplex PCR. Antibiotic susceptibility testing and MIC values of imipenem were performed. the expression of target gene was evaluated by Real time PCR.

Out of 500 samples, 387 Staphylococcus species were isolated, among which 155 strains were S. saprophyticus. PCR data indicated that 36.77% of S. saprophyticus isolates harbored one of sdr family genes. The MIC and subMIC values of S. saprophyticus species which were treated with imipenem were 125 μg/ml and 225 µg/ml, respectively. Treatment with imipenem induced significant decrease in the expression of sdrC and sdrD genes as fold changes were -1.241 and -1.322, respectively. There was no statistically significant in sdrE gene expression.

The results of our study showed that resistance to imipenem was significantly high in strains harboring sdrE gene. Also, treatment with imipenem did not cause any significant change in the expression of sdrE gene, which could be a factor in the application of antibiotic resistance by bacteria to this antibiotic. In addition, the present study raises another alarm about the increased risk of antibiotic resistance.