Abstract: Oligonucleotide probes for detecting Enterobacteriaceae species. Unique gyrA coding regions permit the development of probes specific for eight different species: Escherichia coli, Citrobacter freundii, Enterobacter aerogenes, Enterobacter cloacae, Klebsiella oxytoca, Klebsiella pneumoniae, Providencia stuartii and Serratia marcescens. The invention thereby provides methods for the species-specific identification of these Enterobacteriaceae in a sample, and detection and diagnosis of Enterobacteriaceae infection in a subject. Further, nucleic acids are provided for determining quinolone-resistant status of these Enterobacteriaceae.