Deep infection represents one of the most devastating complications of total knee arthroplasty. Commonly implicated organisms are gram positive bacteria such as staphylococcus aureus, staphylococcus epidermidis and group B streptococcus. Occasionally, infection may be caused by rare organisms, particularly in the immunocompromised host.

We present a case of infected total knee arthroplasty in a penicillin allergic patient, caused by Pasteurella multocida, 13 weeks after the initial surgery. This was treated by open debridement and change of insert as well as aggressive antibiotic therapy. The patient admitted contact with a cat and three dogs at home.

Pasteurella multocida is a facultatively anaerobic gram negative coccobacillus. It is a commensal in the nasopharygeal tract of domestic pets such as cats and dogs. Human infection can often be attributed to a bite or scratch. Prosthetic joint infection caused by Pasteurella is uncommon. Only a few cases have been reported in the literature.

Our case has several learning points: (1) It is very important to definitively identify Pasteurella because standard therapy for prosthetic joint infection (e.g. flucloxacillin or vancomycin) is not optimal for this species.(2) Pasteurella are susceptible to penicillin, but the optimal antibiotic therapy for infections in patients allergic to beta lactam antibiotics is uncertain. A combination of ciprofloxacin and linezolid is recommended. (3) There is no consensus regarding appropriate management. There are reports of washout and antibiotic therapy alone, single and two stage revision procedures. In our case, at five months follow up, open debridement and change of insert along with antibiotic treatment appears to have been effective, although more long term follow up is required. (4)Post arthroplasty, all patients with pets at home should be advised to seek medical attention following any bite or scratch so that timely prophylaxis can be administered before sepsis becomes deep-seated.