Methicillin-Resistant Staphylococcus pseudintermedius Infection in a Bone Marrow Transplant Recipient

Abstract

Staphylococcus pseudintermedius is a veterinary pathogen that has seldom been described as an agent of human disease. Features of this probably underreported coagulase-positive Staphylococcus species are depicted here through the description of a graftversus-host disease-related wound infection caused by a multidrug-resistant strain. CASE REPORTA 65-year-old male patient who had received (3 years previously) an allogeneic bone marrow transplant (BMT) for chronic lymphoblastic leukemia was admitted to the Pescara Civic Hospital (Italy) because of a wound infection, located in the periumbilical region and showing two different purulent discharges. The lesion was due to chronic graft-versus-host disease (GvHD) that complicated the BMT. The patient affirmed that he lived in proximity to a pet dog and farm cows.Pus staining revealed Gram-positive cocci within leukocytes, while cultures yielded a massive growth of mannitol-nonfermenting coagulase-positive staphylococci (CPS). Based on colony aspect (brightness of the white-gray color), two different isolates (named S32 and S33) were recognized, sharing a double-zone hemolysis on the sheep blood agar plate (Fig. 1). They were identified as Staphylococcus intermedius by both the Vitek2 and the API system (bioMérieux, Marcy l'Etoile, France). However, S. intermedius is the only species belonging to the so-called Staphylococcus intermedius group included in these systems' databases. The S. intermedius group includes S. intermedius, cultured from a wide variety of animals, Staphylococcus pseudintermedius, which recent studies indicate is the prevalent S. intermedius group species harbored by dogs and cats, and Staphylococcus delphini, first isolated from dolphins but later collected from several terrestrial animals (1, 2). Thus, we did not consider this identification as conclusive. Moreover, since the absence of mannitol fermentation, along with the double-zone hemolysis, was highly suggestive for S. intermedius/S. pseudintermedius, the patient was screened for S. intermedius group nasal and skin colonization. Five phenotypically similar organisms were grown from the nasal and the hand skin swabs. Again, they were identified as S. intermedius by the Vitek2 and the API system. Different tests (both phenotypic and genotypic) were performed to confirm the identification. Phenotypically, all the strains were colistin resistant and showed a slow positivity to the Voges-Proskauer reaction (suggesting that the isolates were S. pseudintermedius rather than S. intermedius). Among genotypic assays, 16S rRNA sequencing did not provide a definitive discrimination among S. intermedius, S. pseudintermedius, and S. delphini. The isolates were then analyzed through automated ribotyping (RiboPrinter; Qualicon DuPont, USA). The instrument provided identical fingerprints for all of the strains and identified them as S. intermedius. A specific multiplex PCR was performed, as previously described (3). The isolates were identified as S. pseudintermedius, since a clear band was obtained at 926 ...

Distribution of coagulase-positive staphylococci in humans and dogs

“…There are some case reports of methicillin-resistant Staphylococcus pseudintermedius (MRSP) infection in dog owners. The increasing number of dogs carrying MRSP constitutes a risk for pet owners to become colonized with MRSP, and MRSP infections in humans may also increase in the near future (Stegmann et al 2010;Savini et al 2013). A high prevalence of S. pseudintermedius in dogs (45.9%) was detected in our research.…”

“…Staphylococcus pseudintermedius is a veterinary pathogen that has seldom been described as an agent of human disease (Savini et al 2013). Van Hoovels et al presented the first clinical report of S. pseudintermedius infection in a human in 2006.…”

“…Importantly, it was discovered that S. pseudintermedius, not S. intermedius, is the common pathogen in dog (Bannoehr et al 2009;Youn et al 2011). It is likely that human and veterinary S. pseudintermedius isolates have been misidentified as S. aureus, S. intermedius, and S. delphini in the past (Sasaki et al 2007;Savini et al 2013).…”

“…Better diagnostic tools are needed for the identification of S. pseudintermedius, and to avoid misidentification with S. aureus and S. intermedius, according to researchers. Molecular methods must be used for the correct differentiation of coagulase positive staphylococci (Van Duijkeren et al 2010;Savini et al 2013).…”

Small Colony Variant of Methicillin-Resistant Staphylococcus pseudintermedius ST71 Presenting as a Sticky Phenotype

“…Among these organisms, Staphylococcus pseudintermedius, although primarily affecting dogs and cats, has also occasionally been recognized as a human pathogen. Most worrying is the emergence of human infections by methicillin-resistant S. pseudintermedius (MRSP) strains (1,2). However, the interpretative criteria for methicillin resistance in this species are available only in the Clinical and Laboratory Standards Institute (CLSI) guidelines for bacterial pathogens from animals, which do not recommend cefoxitin as a surrogate antibiotic in the prediction of mecA-mediated methicillin resistance.…”