A novel kit for rapid and low cost detection of Staphylococcus aureus causing neonatal sepsis / Sally Atef Mohamed Ahmed ; Supervised Magdy A. Amin , Ahmed S. Attia , Omneya M. Helmy

Thesis (Ph.D.) - Cairo University - Faculty of Pharmacy - Department of Microbiology and Immunology

Neonatal sepsis is a life-threatening condition and Staphylococcus aureus is one of its major causes. However, to date, no rapid and sensitive diagnostic tool has been developed for its direct detection. Bioinformatics analyses identified two surface exposed polypeptides of two cell wall proteins. The first polypeptide is a 161 amino acid (aa) polypeptide of the SdrD, a surface protein involved in colonization and adhesion to human cells and the second is a 112 aa polypeptide of the NWMN_1649, a surface protein involved in cell aggregation and biofilm formation. Both polypeptides were species-specific and highly conserved moieties in S. aureus. The polypeptides were cloned, purified, and used to immunize mice to raise specific immunoglobulins. Antibodies against NWMN_1649 polypeptide were purified, conjugated to gold nano-particles and used in the preparation of an immunochromatographic strip (ICS). The developed prototype ICS detected as low as 5 og purified polypeptide and 102 CFU/ml S. aureus within 15 min. The strip showed superior ability to directly detect S. aureus in neonatal sepsis blood specimens without prior sample processing. Moreover, it showed no crossreactivity when used in testing specimens positive for two other major causes of neonatal species; coagulase-negative staphylococci and Klebsiella pneumoniae. The selected NWMN_1649-derived polypeptide demonstrates success as a promising biomolecule upon which a prototype ICS was developed. This ICS provides a rapid, direct, sensitive, and specific option for the detection of S. aureus causing neonatal sepsis. Such tool is urgently needed especially in resourceslimited countries

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