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Isolation and Phenotypic Characterization of Virulent Bacteriophages Against Multidrug-Resistant Escherichia coli and
Ashetu Fikadu1,2, Stephen Amankwah3, Bikila Alemu1,4
1School of Medical Laboratory Sciences, Jimma University, Jimma, Ethiopia.
Purpose:
The use of lytic bacteriophages for the control or elimination of pathogenic multidrug-resistant (MDR) bacteria is the promising alternative. However, the emergence of resistant bacterial variants after phage application may challenge its therapeutic benefit. In this study, we aimed to isolate candidate phages from sewage samples against two MDR Escherichia coli as well as their phage-resistant variant.
Methods:
MDR E. coli isolates (n = 10) obtained from Jimma Medical Center that had been properly identified and stored were used to isolate bacteriophages. Two lytic coliphages were isolated from hospital sewage samples following standard protocols. Upon single phage infection, phage-resistant variant quickly evolved serving as a new host for the isolation of a third lytic phage. This virulent phage's lytic activity against both its host and the wild host was investigated. The host infectivity of the various cocktails was assessed, and each phage's biological properties were studied.
Results:
Out of the first round of phage isolation process, two lytic phages were identified as VBO-E. coli 4307 and VBW-E. coli 4194. When exposed to VBO-E. coli 4307, the wild-type E. coli 4307 developed resistant variants. A third phage (VBA-E. coli 4307R) was isolated specific to this resistant variant (E. coli 4307R) under optimum condition. For VBO-E. coli 4307, VBW-E. coli 4194, and VBA-E. coli 4307R, the plaque assays generated under comparable conditions were 2.13 × 1010 PFU mL-1, 9.17 × 1012 PFU mL-1, and 3.3 × 1010 PFU mL-1, respectively. These phages have nearly identical stability and lytic ability but differ greatly in their host ranges for VBA-E. coli 4307R.
Conclusion:
While the wild-type MDR pathogen could easily evolve resistance when exposed to a single phage infection by VBO-E. coli 4307, it is still possible to isolate a novel bacteriophage from environmental samples that is effective against the phage-resistant variants. This indicates that it is possible to manage the effects of phage resistance pathogens even if they are MDR.
Insights
Lytic bacteriophages offer a promising alternative for combating multidrug-resistant bacteria. New phages can be isolated to target resistant variants, suggesting phage therapy can manage resistant pathogens.
Area of Science:
- Microbiology
- Bacteriophage Therapy
Background:
- Multidrug-resistant (MDR) bacteria pose a significant global health threat.
- Lytic bacteriophages are being explored as an alternative to antibiotics for controlling MDR pathogens.
- Bacterial resistance to phages can emerge, potentially limiting therapeutic efficacy.
Purpose of the Study:
- To isolate lytic bacteriophages effective against MDR Escherichia coli.
- To investigate the potential for isolating phages effective against phage-resistant bacterial variants.
- To assess the feasibility of phage therapy in managing MDR bacterial infections.
Main Methods:
- Isolation of bacteriophages from hospital sewage samples against MDR E. coli.
- Generation and characterization of phage-resistant E. coli variants.
- Isolation of a novel phage targeting the resistant variant.
- Evaluation of phage lytic activity, host range, and biological properties.
Main Results:
- Two lytic coliphages, VBO-E. coli 4307 and VBW-E. coli 4194, were isolated.
- A phage-resistant E. coli variant emerged after exposure to VBO-E. coli 4307.
- A third lytic phage, VBA-E. coli 4307R, was isolated specifically against the resistant variant.
- All three phages demonstrated high plaque-forming units (PFU/mL) and comparable stability and lytic ability, with VBA-E. coli 4307R exhibiting a distinct host range.
Conclusions:
- Wild-type MDR pathogens can rapidly develop resistance to single phage infections.
- Novel bacteriophages effective against phage-resistant variants can be isolated from environmental samples.
- Phage therapy remains a viable strategy for managing MDR bacterial infections, even in the presence of emerging resistance.
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