Performance of Five Commercial Identification Platforms for Identification of Staphylococcus delphini

Abstract

The Staphylococcus intermedius group (SIG) is a collection of coagulase-positive staphylococci consisting of four distinct species, namely, Staphylococcus cornubiensis, Staphylococcus delphini, Staphylococcus intermedius, and Staphylococcus pseudintermedius. SIG members are animal pathogens and rare causes of human infection. Accurate identification of S. pseudintermedius has important implications for interpretation of antimicrobial susceptibility testing data and may be important for other members of the group. Therefore, we sought to evaluate the performance of five commercially available identification platforms with 21 S. delphini isolates obtained from a variety of animal and geographic sources. Here, we show that automated biochemical platforms were unable to identify S. delphini to the species level, a function of its omission from their databases, but could identify isolates to the SIG level with various degrees of success. However, all automated systems misidentified at least one isolate as Staphylococcus aureus. One matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) system was able to identify S. delphini to the species level, suggesting that MALDI-TOF MS is the best option for distinguishing members of the SIG. With the exception of S. pseudintermedius, it is unclear if other SIG members should be routinely identified to the species level; however, as our understanding of their role in animal and human diseases increases, it may be necessary and important to do so.

One Affectionate Puppy: A Case of Septic Arthritis Due to Staphylococcus Pseudintermedius

“…S. pseudintermedius is a rarely described pathogen in humans, though identification is increasingly common due to the use of more accurate diagnostic tools. 4 Similar to previous cases, our patient reported extensive physical contact with a dog, but unlike prior reports, she did not have predisposing medical conditions or suffer a traumatic bite. We hypothesize that her infection was due to either transient bacteremia from a distant colonized site or local spread from microtrauma to the foot, which the dog licked frequently, though she lacked evidence of overt spread directly from the skin.…”

“…6 Although MALDI-ToF MS is considered more accurate, incorrect species allocations also occur. 4 Methicillin-resistant and multidrug resistant strains of S. pseudintermedius have been described and are increasingly common. A recent case series 3 of S. pseudintermedius among 33 patients with chronic rhinosinusitis found an 82% resistance rate to penicillin and 27% to oxacillin.…”

Characterization of Staphylococcus intermedius Group Isolates Associated with Animals from Antarctica and Emended Description of Staphylococcus delphini

“…Cluster analysis based on MALDI-TOF MS protein data was able to separate the S. pseudintermedius and S. delphini Antarctic isolates, place them together with corresponding type strains, and create separate clusters from S. intermedius and S. cornubiensis type strains. Unlike a recent report [72], mass spectrometry was unable to identify two Antarctic isolates of S. delphini using a MALDI-TOF MS-based scoring identification workflow.…”

Implanted Port Catheter System Infection Caused by Methicillin-resistant <i>Staphylococcus pseudintermedius</i> ST71-SCC<i>mec</i> type III

“…The Vitek2 system database, which is used in our clinical laboratory, includes S. pseudintermedius. In contrast, other commercially available automated biochemical identification platforms such as the MicroScan WalkAway (Beckman Coulter, Inc., Brea, CA, USA) and BD Phoenix (BD Biosciences, Franklin Lakes, NJ, USA) database, do not include S. pseudintermedius (30). The true incidence of S. pseudintermedius as a cause of human infection may therefore be underestimated.…”

“…Recent studies have showed MALDI-TOF MS to be a rapid and accurate method for the species-level identification of SIG group members ( 30 , 33 , 34 ). However, the accurate species level identification of S. pseudintermedius depends on the database.…”