Isolation and Characterization of Enterobacter species from Environmental and Clinical samples in Adama, Ethiopia

Abstract

Enterobacter is emerging as one of the most important bacterial genera due to the increasing prevalence of drug resistance observed in this species. This study aimed to isolate and characterize Enterobacter species from environmental and clinical samples. A total of 65 samples were collected, comprising 40 environmental samples and 25 clinical samples. Bacterial isolates were identified using standard culture methods and characterized through biochemical tests and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS). Additionally, biofilm formation was assessed using the crystal violet method, and antimicrobial susceptibility was evaluated using the disk diffusion method. Molecular characterization on selected isolates was performed through PCR amplification of the intergenic spacer region and 16S rRNA sequencing. In this study a total of 88 bacterial isolates were identified, of which 41 (46.6%) were identified as Enterobacter spp. based on Gram staining, biochemical tests, and MALDI-TOF MS results, comprising 21 isolates from soil and 20 isolates from clinical samples. Among these, 17 (80%) of the soil isolates and 18 (90%) of the clinical isolates were found to be strong biofilm producers. The soil isolates predominantly exhibited resistance to chloramphenicol and ampicillin, followed by cephalexin. Similarly, the clinical isolates demonstrated high resistance to ampicillin, chloramphenicol, and cephalexin. Notably, the both soil and clinical isolates were found susceptible to cefepime. PCR amplification of the IGS region indicated that two of the isolates (ENV048 and ENV052) share an evolutionary relationship, while the remaining four samples represent distinct strains, suggesting genetic divergence. The 16S rRNA sequencing of isolate ENV053 revealed 98% similarity to E. asburiae. Overall, we demonstrated that Enterobacter spp. are prevalent in both environmental and clinical samples, displaying significant biofilm formation and resistance to available therapeutic options. This warrants close monitoring to prevent the spread of drug resistance.