Pasteurella multocida Bacteremia With Associated Knee Arthroplasty Infection in an 80-Year-Old Caucasian Man

Sophie Arbefeville, MD; Anthony Harris, BS; Steven Dittes, MD; Patricia Ferrieri, MD

Disclosures

Lab Med. 2016;47(3):241-245. 

In This Article

Discussion

In the case of this patient, his history of owning a pet dog was discovered only after we identified that he was septic with P. multocida. This turn of events suggests that many physicians are still not considering the possibility of zoonotic infections in diagnosis of patients. Cat bites and cat scratches are more commonly reported as the source of infection than dogs in Pasteurella prostatic joint infections (PJIs), and the knee joints are more commonly affected than the hip joints.[5] Older age is a known risk factor for P. multocida PJIs; our patient was 80 years old.[3] This case is unique because the knee exam showed only tenderness and pain with range of motion but no erythema, warmth, or obvious effusion, as one might expect with joint infection, and his X-ray results were unremarkable. The P. multocida bacteria were introduced possibly through small skin breaks that caused bacteremia and subsequently hematogenously seeded to the right knee, or the bacteremia present on admission was secondary to the infected right knee joint. Pasteurella infections that are not directly associated with bite wounds often occur due to P. multocida species.[3] Commonly, affected patients have severe comorbidities and/or immunocompromise. These patients usually have bacteremia, need ICU management, and have increased mortality.[3]

Subspecies of P. multocida clinical isolates are rarely reported in the literature. The MALDI-TOF mass spectrometry system does not identify P. multocida to the subspecies level, and the differentiation of the 3 subspecies via biochemical testing can be challenging. In our case, the 16S rRNA gene sequencing showed a close genetic relatedness to P. multocida subsp. septica.

The identification of P. multocida to the subspecies level can have clinical and epidemiological implications. P. multocida subsp. multocida and P. multocida subsp. septica are more frequently associated with bacteremia. P. multocida subsp. multocida has been found in dog- and cat-associated injuries, whereas P. multocida subsp. septica most often has been isolated from wounds afflicted by cats. To our knowledge, we are the first to report a case of P. multocida PJI associated with bacteremia for which the identification of the 2 isolates was made by sequencing the 16S rRNA gene.

The leading organisms responsible for PJIs are Staphylococcus aureus and coagulase-negative Staphylococcus;[6]P. multicoda is still a relatively rare cause of PJIs. Review of the literature since 1975 shows approximately 33 reported cases of PJIs with P. multocida; in each case, contact with a cat or dog through a bite, scratch, or lick was reported.[5,7,8]

Pasteurella spp. generally are susceptible to penicillin, broad-spectrum cephalosporins, azithromycin, tetracyclines, and quinolones. Resistance to erythromycin has been reported. In our case individual, both isolates were susceptible to ampicillin, ceftriaxone, levofloxacin, penicillin, and trimethoprim/sulfamethoxazole. Prolonged therapy of 6 weeks of IV antibiotics was instituted in our patient to protect his repaired mitral and aortic valves from infection, as well as to treat his knee-joint infection. At follow up the patient finished his 6 weeks of antibiotic IV therapy. The patient underwent a revision of his right total knee arthroplasty without complication and was discharge to the nursing home setting 3 days after the procedure.

The high prevalence of pets in American families increases the risk of exposure to P. multocida and thus to possible infections. It is important for clinical microbiology laboratories to identify this organism accurately and in a timely manner. We have shown that 3 different methods were able to identify this organism accurately, but only the 16S rRNA gene sequencing was able to determine its subspecies.

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