31Aim: Infective endocarditis (IE) is a major complication of Staphylococcus (S.) aureus infection 32 in humans particularly those with bacteremia. Although Staphylococcus species are commensal 33 on or in different parts of the human body, it is also known to be a serious pathogen causing 34 bacteremia and sepsis that could lead to IE. Therefore, our aim was to assess the prevalence as 35 well as phenotypic and genotypic association of the Staphylococcal superantigens (SAgs) among 36 bacteremic and IE patients.37 Methods: This study was conducted on Staphylococcus isolates recovered from bacteremic and 38 IE patients. The isolates were screened phenotypically for the detection of SAgs including 39Staphylococcal enterotoxins (SEs) and toxic shock syndrome toxin-1 (TSST-1). Molecular 40 detection and analysis of sea, seb, sec, sed, see and tsst-1, the major SAgs coding genes were 41 performed using PCR and agarose gel electrophoresis, respectively. The obtained findings were 42 statistically analyzed using standard methods.
43Results: Detection of SAgs using ELISA revealed that 12 (46%) isolates were positive for 44 enterotoxin production. However, the PCR revealed that 19 (73%) isolates were positive for 45 enterotoxin genes with the highest prevalence of the sea gene (79%), followed by the seb (63%), 46 tsst-1 (21%). The least frequent gene was the sed (5.3%). Accordingly, phenotypic and genotypic 47 screening for prevalence of SAgs among Staphylococcal isolates showed significant difference 48 (P value =0.046703), however, no significant correlation could be observed among the coagulase 49 negative Staphylococci (CoNS) isolates (P value =0.248213). Statistical correlations between 50 bacteremic and IE isolates with respect to prevalence of SAgs, showed no significant difference 51 (P-value = 0.139, Effect size = 0.572) indicating no specific association between any of the 52 detected SAgs and IE. 3 53 Conclusion: no significant difference has been found between Staphylococcal IE and bacteremia 54 isolates regarding both phenotypic and genotypic detection of the most commonly SAgs. 55 Therefore, all Staphylococcal bacteremic patients are suspected for IE. Also, future work should 56 be conducted for analysis of SAgs gene expression. 57 58 59 Introduction 60 S. aureus is a dangerous and versatile human pathogen because of its ability to cause various 61 types of infections, including skin and soft tissue sepsis, pneumonia, bloodstream infections 62 (BSIs), osteomyelitis and infective endocarditis (IE) [1]. Higher mortality rate (15-25%) was 63 recently reported from serious S. aureus infections, particularly bacteremia and endocarditis 64 [2,3]. IE is a major devastating complications of Staphylococcal bacteremia [3,4]. In 2018, 65 Asgeirsson et al. reported that S. aureus is the foremost cause of IE where it comprises about 15-66 40% of all IE cases worldwide [3]. 67 IE is caused principally with bacteria or fungi where serious clinically relevant complications 68 including, damaging of one or more of the ...