Introduction 

Chronic, multi-revised periprosthetic joint infections (PJI) remain challenging. Phage therapy (PT) is a promising adjunctive strategy given its ability to target biofilm-embedded bacteria. We describe salvage PT combined with Debridement Antibiotics and Implant Retention (DAIR) for chronic left hip PJI caused by multi-drug resistant (MDR) Staphylococcus epidermidis. 

Methods 

A 65-year-old female with thalidomide-related upper limb phocomelia and congenital bilateral hip dysplasia underwent primary left total hip replacement in 2018. She experienced multiple dislocations requiring open reduction and subsequently developed Staphylococcus epidermidis PJI. Seven surgical procedures were performed to eradicate infection including DAIR and washout. Complete revision was deemed too high risk due to complex pelvic metalwork and prosthesis stability. Antibiotic suppression with pristinamycin and doxycycline failed, and she also developed linezolid-related optic neuritis. The isolate (2020–2024) remained sensitive to Teicoplanin, Linezolid and Daptomycin only. Pre-treatment, she had intermittent fevers, fatigue, a painful left hip mass, and declining mobility. 

The case was discussed at a national orthopaedic phage multidisciplinary team (MDT) meeting. Due to lack of oral suppressive options and high revision risk, salvage DAIR with adjunctive PT was recommended. 

Following phage susceptibility testing and local ethics and regulatory approvals, a fixed lytic 5-phage anti-staphylococcal cocktail was selected (1 × 10⁹ PFU per 10 mL dose; equivalent to 1 × 10⁸ PFU/mL total cocktail). Treatment comprised extensive DAIR with phage-loaded hydrogel applied to the prosthesis, intra-articular and intravenous (IV) phage on day 0, twice-daily IV phages for 7 days, and ultrasound-guided intra-articular injections on days 7 and 14 (with microbiological sampling and seroma aspiration). Concurrent antibiotics included IV Teicoplanin and oral Doxycycline for 12 weeks, then Doxycycline monotherapy. 

Results 

The combination of topical, IV and intra-articular PT was well tolerated with no serious adverse events. Transient asymptomatic eosinophilia occurred from day 10–45. At 8 weeks, the wound had healed and pain decreased significantly. Left hip swelling persisted, but she regained mobility and autonomy. CRP normalised (<10 mg/L) by day 20 and chronic anaemia improved (haemoglobin 82 to 106 g/L). Intraoperative cultures grew the same S. epidermidis (now Doxycycline-sensitive). Day 7 and 14 aspiration cultures demonstrated no bacterial growth. 

Conclusions 

We describe the first combined triple-route (IV, topical hydrogel, and intra-articular) adjunctive PT for chronic MDR PJI. This regimen was well tolerated, with encouraging early clinical, biochemical, and microbiological responses at 8 weeks. Longer follow-up is ongoing to assess infection eradication.