Tropical Medicine and Infectious Diseases

Enterobacter cloacae is a Gram-negative bacterium that contributes to a wide range of nosocomial infections all over the world. It causes blood stream infections in both adults and infants, including neonates. Th e mortality associated with such infections have reached alarming rates, up to 60% in some instances. The emergence of strains that are highly-resistant to multiple antibiotics adds more complexity to situation. In this work, we are developing a rapid assay for the detection of E. cloacae using conjugated gold nano-particles. Bioinformatics analyses of E. cloacae proteome identifi ed two peptides that are unique to E. cloacae. Th ey are highly conserved among E. cloacae strains that are sequenced in Genbank. In addition, they showed almost

no similarities to peptides in other members of the Enterobacteriaceae family nor other species within the Enterobacter genus.The two peptides were chemically-synthesised, and their identity and purity were verifi ed, then they were used individually to  immunize BALB/C mice to produce specifi c anti-sera. Gold nano particles (GNPs) were produced with the citrate reduction

method and their size was verifi ed using electron microscopy. Antibodies were purifi ed and then conjugated to the GNPs. The developed GNPs were then used to detect E. cloacae in solution through microscopic examination, spectrophotometrically, and visual inspection. The developed GNPs detected E. cloacae with both high sensitivity and specificity. More importantly the time taken for getting the results was less than 1 hour as compared to the 48 hours required for traditional methods and with much less cost than the nucleic acids-based methods. The developed assay provides a sensitive, rapid, and low-cost tool forn detection of E. cloacae and would contribute in reducing the harms caused by this pathogen through prompt accurate diagnosis.