Abstract
Staphylococcus aureus typing using gene encoding protein A (spa typing) seems to have a high potential discriminatory power for typing this bacterium. This study was designed based on spa typing method to compare the S. aureus types among healthy carrier vs patients, and MRSA vs MSSA isolates. Method: This study was carried out on 182 spa typeable S. aureus isolates, including 52 MRSA. DNA was extracted by phenol chloroform-isoamyl alcohol method and it was amplified by specific primer of polymorphic X region of spa. Spa types were determined by Ridom Staph Type software. The spa types distribution among MRSA vs MSSA and healthy carrier vs patients, isolates were statistically compared by X2 method and P < 0.05 was considered as significant. Result: The most common types of spa in our region were t037 (18.3%) and t937 (13.9%) from 50 spa types which were identified in this study. spa types in this study were isolated from various age groups but t660 spa types were only isolated from children. Distribution of all spa types among MRSA and MSSA isolates was 16 and 38 types, respectively which is significant. In this study we found seven new spa types (belong to twelve isolates) which are reported for the first time. In 5 out of the above 7 new types the 24 bp repeated sequences in spa gene X region were already recognized but their 24 bp arrangement is introduced in our present investigation. In the remaining 2 new types we found new 24 bp nucleotide sequences which are also introduced for the first time in our present study. Conclusion: The distribution of spa types in MSSA strains was significantly higher than MRSA isolates, but there are not any specific spa types for discrimination between MRSA and MSSA. The novelty of our study is the introducing 7 new spa types including 2 new 24 bp repeated sequences in the X region of spa gene.
Highlights
Staphylococcus aureus is a well known agent as commensal organism lived on the human skin and as a leading cause of human disease
Rapid and accurate determination of the different Staphylococcus aureus isolated from patients and carriers are a great help in understanding the epidemiology of this bacteria and its infection control [7]
pulsed-field gel electrophoresis (PFGE) is still considering the gold standard in molecular typing, owing to its excellent discriminatory ability
Summary
Staphylococcus aureus is a well known agent as commensal organism lived on the human skin and as a leading cause of human disease. This bacterium responsible for a variety of disorders ranging from superficial skin infections up to serious abnormalities such as pneumonia, Bacteremia and Endocarditis and Staphylococcus aureus colonizes the anterior nares of 20% - 80% of the human population [1] [2]. There are many molecular methods that have been employed to type, differentiate and group the S. aureus isolates, such as pulsed-field gel electrophoresis (PFGE), which have been used as the gold-standard method [3], Multilocus Sequence Typing (MLST), coa typing, phage typing and SCCmec typing. The X region was amplified and its size estimated by electrophoresis [6]
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