Listeria monocytogenes is usually thought of as a bacterial pathogen that causes invasive disease including meningitis and bacteraemia in susceptible hosts. It remains a rare cause of bone and joint infection; there is therefore potential for clinical and laboratory delay in diagnosis and for uncertainty over optimal management. We describe our experience of two such cases of L. monocytogenes prosthetic joint infection to highlight key features in clinical presentation and management.

Two case reports of L. monocytogenes prosthetic joint infection are described with reference to previous published cases.

A 57 year old woman presented with a 10 day history of severe pain and swelling around a left knee prosthesis which had been implanted as bilateral total knee replacements three years previously. She had a background of rheumatoid arthritis, controlled with prednisolone, methotrexate and ritixumab. Cultures from the left knee isolated L. monocytogenes. The patient was commenced on IV amoxicillin and after 4 weeks underwent 1st stage revision including radical debridement and removal of prosthesis. During the procedure an antibiotic-impregnated spacer (gentamycin/clindamycin with additional vancomycin added in house) was inserted. Antibiotic therapy with intravenous amoxicillin was continued for 2 weeks post-procedure and on discharge the patient was converted to oral amoxicillin for a further 8 weeks. The patient went on to have a 2nd stage revision, making a good recovery.

An 85 year old woman presented with an 18 month history of discomfort and recurrent abscesses along the wound line of a left hip prosthesis, implanted over 20 years ago. She had a background of osteoarthritis and bullous phemphigoid, previously on steroid treatment. Fluid from the abscess was aspirated and isolated L. monocytogenes. Due to patient preference and frailty, radical revision was not thought a viable management option. Chronic suppressive therapy with oral amoxicillin was therefore instigated; one year on the infection remains well controlled and discomfort in the left hip has improved.

L. monocytogenes has previously been infrequently implicated as a pathogen in prosthetic joint infection; however, there are reports of increasing numbers of cases particularly amongst immunosuppressed individuals. With an expanding at-risk population(1), its importance as a cause of prosthetic joint infection is set to rise in the future. Optimal management has not been well studied; it is likely that the best option combines antimicrobial therapy and prosthetic removal if possible.

The purpose of the study was to retrospectively assess the patients treated to date with the vac ulta system using a technique of antibiotic instillation.

The vac ulta system is licensed for use with anti-septic instillation fluid but we have now treated a number of patients with antibiotic instillation under the guidance of the microbiology department. All patients being treated with the vac ulta system were included in the study. There were no exclusions. Pathology treated, infecting organism, antibiotic used and length of treatment were all recorded. Any antibiotic related complications were noted. Treatment was judged successful with resolution of presenting symptoms, normalization of inflammatory markers and three negative foam cultures.

There were 21 patients included in the study. There were 13 male and 8 female patients. Length of treatment ranged from 1 week to 10 weeks with a mean of 4.2 weeks. Follow up ranged from 1 month to 42 months with a mean follow up of 17.9 months

The most common pathogen was Staph. Aureus(11 cases). Enterobacter, ESBL, Strep. Milleri, MRSA and Citrobacter were also treated. Antibiotics instilled included flucloxacillin, meropenem, gentamicin, vancomycin, meropenem and teicoplanin. There were no antibiotic reactions/allergies. Pathologies treated included osteomyelitis, two stage amputations for infection, infected non-union and infected metalwork. Infection recurred in 2 of 21 patients (10%), with one recurring at 18 months and one at 2 years.

The 90% treatment success rate is highly encouraging in this notoriously difficult group of patients to treat. In this series vac instill was an effective treatment of infection and allows antibiotic treatment to be targeted to the infected tissues. There were no adverse reactions seen.

Larger series with longer follow up are no needed but we believe this technique is safe, successful and easily administered can be cautiously adopted on a wider basis.