Prevalence and In Vivo Assessment of Virulence in Shiga Toxin-Producing Escherichia coli Clinical Isolates from Greater Cairo Area

Shiga toxin-producing (STEC) has been identified as an important etiologic agent of human disease in Egypt. To investigate the occurrence and describe the characterization as well as prevalence of STEC in Greater Cairo hospitals as well as molecular characterization of virulence and resistance genes. Four hundred seventy clinical isolates were collected from eight hospitals and analyzed by genotypic and phenotypic methods for STEC, followed by histopathological examination and scoring of different organs lesions. The highest proportion of isolates was from urine (151 isolates), whereas the lowest was from splenic drain (3 isolates). In tandem, when serogrouping was performed, 15 serogroups were obtained where the most prevalent was O157 and the least prevalent was O151. All isolates were positive when screened for identity gene A, while only typable strains were screened for seven virulence genes 1 (gene encoding Shiga toxin 1), 2 (gene encoding Shiga toxin 2), (gene encoding thermostable hemagglutinin), A (gene encoding intimin), (gene encoding invasion protein), (gene encoding aggregative adherence transcriptional regulator), and A (aspartate transaminase) where the prevalence was 48%, 30%, 50%, 57%, 7.5%, 12%, and 58%, respectively. Of 254 typable isolates, 152 were STEC carrying 1 or 2 genes or both. Relying on comparison between different pathotypes via histopathological examination of different organs, pathotypes could be divided into mild virulent, moderate virulent, and high virulent strains. Statistical analysis revealed significant correlation between different serogroups and presence of virulence genes.