Abstract
Citrobacter species often occur in sewage, food, soil, wastewater, and in the intestinal tract of animals and humans. Citrobacter spp. cause urinary tract infections (UTIs) and infantile meningitis in humans. Due to the presence of plasmid-encoded resistance genes, Citrobacter spp. are often resistant to many antibiotics. In this study, Citrobacter virus HCF1, a novel virulent bacteriophage capable of killing Citrobacter amalonaticus and Citrobacter freundii, was isolated from the sewage water. The isolated bacteriophage was characterized with respect to transmission electron microscopy, one-step growth curve, host range, in vitro efficacy, storage stability, and environmental stress tolerance. The one-step growth curve analysis revealed that the latent period of HCF1 was 30 min and the estimated burst size was 121 plaque-forming units (PFU) per bacterial cell. Host range testing indicated that the HCF1 was specific to the Citrobacter genus. In vitro efficacy assay in the effluent of an anaerobic biodigester showed that the HCF1 completely eliminated the host within 4 and 5 h at MOI:100 and MOI:10, respectively, thereby indicating its potential for combating C. amalonaticus infections. The isolated bacteriophage is considerably stable and tolerant to environmental stress. Furthermore, the complete genome of HCF1 was sequenced using Oxford Nanopore sequencing and the data were subjected to detailed bioinformatic analyses. NCBI-BLASTn analysis revealed that the HCF1 genome had a query coverage of 15–21% and a maximum similarity of 77.27–78.49% with 11 bacteriophages of the Drexlerviridae family. Detailed bioinformatic analysis of the genome profile suggests that HCF1 is a novel T1svirus belonging to the Tempevirinae subfamily of the Drexlerviridae family.
Highlights
Citrobacter is a genus of aerobic, Gram-negative bacteria belonging to the Enterobacteriaceae family
One-step growth curve analysis, as studied by infecting the C. amalonaticus NAIMCC 1364 with the bacteriophage, suggests that HCF1 has a latent period of 30 min and that the estimated burst size is 121 plaque-forming units (PFU) per bacterial cell (Figure 1D)
The literature suggests that the latent period and burst size of other Citrobacter spp. bacteriophages are 20–25 min and 45–801 PFU per bacterial cell, respectively (Chaudhry et al, 2014; Oliveira et al, 2016) which agrees well to the present observations
Summary
Citrobacter is a genus of aerobic, Gram-negative bacteria belonging to the Enterobacteriaceae family. A study (Garcia et al, 2016) reporting four cases of C. amalonaticus infection in patients hospitalized in Marseille, France, using MALDI-TOF technique observed statistically higher prevalence of the UTI episodes, thereby indicating that this bacterium could be an emerging pathogen responsible for UTIs in immunocompromised patients. These studies suggest that C. amalonaticus could be a potential pathogen and a causative agent of UTIs in immunocompromised patients worldwide
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
