P. multocida Bacteremia With Knee Arthroplasty Infection

Abstract and Introduction

Abstract

Objectives: To identify the gram-negative rods grown from blood cultures and a right-knee fluid aspirate from an 80-year-old caucasian man who had undergone a total right knee arthroplastic procedure 6 years ago, and to assess the genetic similarity between the 2 isolates.

Methods: We used 3 different approaches: biochemical testing, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, and 16S ribosomal RNA (rRNA) gene sequencing.

Results: The 3 methods identified the gram-negative rods as Pasteurella multocida; 16S rRNA gene sequencing further identified the organisms as P. multocida subsp. septica.

Conclusion: A concordant identification of P. multocida was observed using biochemical testing, mass spectrometry, and 16S rRNA gene sequencing. Only 16S rRNA sequencing was able to determine the subspecies of P. multocida and to determine the genetic relatedness of the 2 isolates.

Introduction

Pasteurella multocida (P. multocida) is a facultative anaerobic, gram-negative, small, pleomorphic, nonflagellated coccobacillus with bipolar staining that belongs to the Pasteurellaceae family. P. multocida is divided into 3 subspecies (multocida, septica, and gallicida), 16 somatic serovars, and 5 capsular serogroups (A to F, excluding C) based on a capsular antigen.^[1,2]P. multocida often exists as a commensal organism in the normal microbiota of the oral, nasopharyngeal, and upper respiratory tracts of many livestock, poultry, and domestic pet species; cats and dogs have the highest carriage rates, at 70% to 90% and 20% to 50%, respectively.^[3]P. multocida infection in humans is primarily acquired through contact with animals, most often through bites, scratches, licks on skin abrasions, or exposure to mucous secretions from pets. In the United States, according to the 2015–2016 American Pet Products Association (APPA) National Pet Owners Survey, 65% of United States (US) households own a pet, which translates to approximately 77.8 million pet dogs and 85.8 million pet cats.^[4] With the abundance of cats and dogs in US households and the commensal nature of the bacteria, the risk of acquiring Pasteurella infections is increasing, particularly in patients who have predisposing factors such as prosthetic joints, malignant neoplasms, and immunosuppression.^[3]