Antibiofilm activity of bacteriophage Φ WL-3 conjuncted with ciprofloxacin, fosfomycin, gentamicin, meropenem or ceftriaxone against a ciprofloxacin/ceftriaxone-resistant Escherichia coli clinical isolate

Objectives Escherichia coli is among the most common cause of Gram-negative prosthetic joint infections (PJI) and ciprofloxacin is the first-line recommended antibiotic for anti-biofilm therapy. Due to the emergence of fluoroquinolone resistance, the management of E. coli PJI becomes more challenging with an increased rate of treatment failure. Here, we investigated the efficacy of a newly isolated bacteriophage Φ WL-3 as a therapeutic agent in combination with ciprofloxacin, fosfomycin, gentamicin, meropenem or ceftriaxone against the biofilm of a ciprofloxacin/ceftriaxone resistant E. coli strain.

Methods Bacteriophage Φ WL-3 was isolated from hospital sewage targeting a ciprofloxacin/ceftriaxone resistant E. coli clinical strain obtained from a patient diagnosed with PJI. Twenty-four-hour old biofilm formed on porous glass beads were exposed to antibiotics alone or combined with bacteriophage Φ WL-3 (10⁸ PFU/mL) simultaneously for 24h or in a staggered manner (first bacteriophage for 4h followed by antibiotic for 24h). Recovering bacteria after treatment was detected by measuring

growth-related heat production at 37°C for 48h by isothermal microcalorimetry. The minimum biofilm bactericidal concentration (MBBC) was defined as the lowest concentration of antibiotic that strongly reduced biofilm cells viability and led to the absence of heat flow production.

Results and Conclusion Table 1. Summary of minimum biofilm bactericidal concentrations

Tab. 1 Summary of minimum biofilm bactericidal concentrations

Antibiotics	MBBCantibiotic (µg/mL)	MBBCantibiotc/Φ (Simultaneous,µg/mL)	MBBCantibiotc/Φ (Staggered,µg/mL)
Ciprofloxacin	>1024	>1024	4
Fosfomycin	>1024	8	2
Gentamicin	32	8	8
Meropenem	32	4	1
Ceftriaxone	>1024	>1024	>1024

Results: All tested antibiotics presented high MBBC values (ranging from 32 to >1024 µg/mL) when tested alone against biofilm (Table 1). A simultaneous administration of Φ WL-3 and antibiotics showed an improved antibiofilm activity for fosfomycin, gentamicin or meropenem, but not for ciprofloxacin and ceftriaxone. However, the highest antibiofilm efficacy was observed after staggered exposure, where the MBBC of ciprofloxacin could also be decreased from >1024 to 4µg/mL. In contrast, ceftriaxone showed no improved activity in either case.

Conclusions: The co-administration of bacteriophage with antibiotics improved considerably the antibiotic efficacy against biofilm, especially after staggered exposure. Our data also suggest that the use of bacteriophages could restore the susceptibility of biofilms to antibiotics, as seen in our case with ciprofloxacin. These results have implications for optimal combined treatment approaches.

Stichwörter Bacteriophage, Biofilm, Ciprofloxacin-resistance E.coli

Publication History

Article published online:
15 October 2020