Genotypic identification and study some virulence factors of Aeromonas hydrophila isolated from children's diarrheal specimens in Baghdad

Abstract

In this study, 266 watery diarrhea specimens were collected from children less than 12 years that suffering from gastroenteritis in Welfare teaching hospital and Teaching laboratories/ Medical city. Out of 266 specimens, 19 (7.14) were identified as Aeromonas hydrophila isolates. The bacteria were identified as Aeromonas hydrophila phenotypically by Api-20 E system. Genotypic identification of Aeromonas hydrophila isolates also done by detection 16S rRNA gene by PCR assay and the results showed the presence of 16S rRNA gene in all 19 (100%) Aeromonas hydrophila studied isolates and this confirm the identification of Aeromonas hydrophila isolates. The antimicrobial susceptibility of Aeromonas hydrophila isolates was determined and the results showed that all 19 Aeromonas hydrophila isolates were resistant to Ampicillin and Amoxicillin (100%), while all 19 isolates were sensitive to Cefotaxime, Cefteriaxon, Norfloxacin and Imipenem (100%). Some virulence factors of the Aeromonas hydrophila isolates were investigated, all 19 Aeromonas hydrophila isolates were tested to detect their ability to produce hemolysin (toxin), protease, lipase, agglutinate human erythrocytes groups and ability to bind to Congo red. Out of 19 isolates, 14(73.68%) Aeromonas hydrophila isolates were hemolysin (toxin) producer which showed a clear zone of lysis on blood agar plates, 11(57.9%) isolates gave a positive result for protease production and 5(26.3%) isolates were gave a positive result for lipase production. Also isolates of Aeromonas hydrophila were tested for their ability to agglutinate human erythrocytes groups (O, A, B, AB). In which 10(52.6%) isolates showed agglutination with group (A) human erythrocytes, 9(47.4%) isolates showed agglutination with group (B) human erythrocytes, 9(47.4%) isolates showed agglutination with group (AB) human erythrocytes, 12(63.2%) isolates showed agglutination with group (O) human erythrocytes and 8 (42.1%) isolates showed agglutination with human erythrocytes groups (O, A, B, AB). The results of the ability to bind to Congo red revealed that 13(68.4%) isolates were bind to Congo red dye, while 6(31.6%) isolates were failed to bind to Congo red.