Edoardo Carretto

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 graft-versus-host disease-related wound infection caused by a multidrug-resistant strain.

Rapid Identification of Five Classes of Carbapenem Resistance Genes Directly from Rectal Swabs by Use of the Xpert Carba-R Assay

ABSTRACT Carbapenemase-producing organisms (CPO) have been identified by global health leaders as an urgent threat. Detection of patients with gastrointestinal carriage of CPO is necessary to interrupt their spread within health care facilities. In this multisite study, we assessed the performance of the Xpert Carba-R test, a rapid real-time quantitative PCR (qPCR) assay that detects five families of carbapenemase genes (blaIMP, blaKPC, blaNDM, blaOXA-48, and blaVIM) directly from rectal swab specimens. Using dual swabs, specimens from 755 patients were collected and tested prospectively. An additional 432 contrived specimens were prepared by seeding well-characterized carbapenem-susceptible and -nonsusceptible strains into a rectal swab matrix and inoculating them onto swabs prior to testing. Antimicrobial susceptibility testing, broth enriched culture, and DNA sequencing were performed by a central laboratory blind to the Xpert Carba-R results. The Xpert Carba-R assay demonstrated a positive percentage of agreement (PPA) between 60 and 100% for four targets (blaKPC, blaNDM, blaVIM, and blaOXA-48) and a negative percentage of agreement (NPA) ranging between 98.9 and 99.9% relative to the reference method (culture and sequencing of any carbapenem-nonsusceptible isolate). There were no prospective blaIMP-positive samples. Contrived specimens demonstrated a PPA between 95 and 100% and an NPA of 100% for all targets. Testing of rectal swabs directly using the Xpert Carba-R assay is effective for rapid detection and identification of CPO from hospitalized patients.

Arginine dehydrolase and β-gentiobiose cannot discriminate within the Staphylococcus intermedius group.

Staphylococcus intermedius [SI], Staphylococcus pseudinrmedius [SP] and Staphylococcus delphini [SD] belong to e so-called ‘Staphylococcus intermedius group (SIG)’; they habit various animal species and have been well known be responsible for skin and postoperative infections in ts and dogs (SI, SP), enteritis in minks (SD), and human seases (Sledge et al., 2010; Sasaki et al., 2007; Stegmann al., 2010). In this context, we have read with great interest the ork of Devriese et al. (2009) that has been recently blished on Veterinary Microbiology. Of course, this per contains relevant messages for readers, as it phasizes the risk of misidentifying SIG species unless olecular tools are employed. Especially, authors highht that tuf, sodA and hsp60 gene sequencing may provide liable characterization at a species level, whereas 16S NA analysis may fail to distinguish among such closely lated species (Devriese et al., 2009). Nonetheless, authors state that some phenotypical pects may aid to characterize SI, SP and SD isolates; in is ambit, we do not agree with the assessment that bntiobiose acidification and arginine dehydrolase activity ay discriminate among SI, SP and SD (Devriese et al., 09). Particularly, in the cited paper it is stated that, unlike both SP and SD, SI acidifies b-gentiobiose but fails to exert an arginine dehydrolase activity; conversely, Chuang et al. describe SP as lacking arginine dehydrolase activity (Chuang et al., 2010); again, although supporting the failure of SP to acidify b-gentiobiose (in agreement with the Devriese’s paper), Sasaki et al. report 60% SD strains (group B) as able to determine b-gentiobiose acidification, as well as 20% SD isolates as arginine dehydrolase negative (group B) (Sasaki et al., 2007). The mentioned discrepancies emerging from the published literature are summarized in Table 1. To conclude, it is clear from the published papers that biochemical features may vary among isolates of the same SIG species. Should b-gentiobiose acidification and arginine dehydrolase be considered as discriminating tests, isolates belonging to different species could be confused each other. On the contrary, gene analyses must always be performed, aiming to more deeply understand the phylogeny, epidemiology and pathogenicity of SI, SP and SD, as well as physiological variation of biochemical activities among different strains of these species. Therefore, discrimination among SIG members may not rely on phenotype-based methodologies but can be provided by accurate molecular diagnostics only.

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

ABSTRACT We first observed the phenomenon of small colony variants (SCVs) in a Staphylococcus pseudintermedius sequence type 71 (ST71) strain, isolated from a non-pet owner. Although we found that small-sized colonies share main features with Staphylococcus aureus SCVs, they nevertheless show a novel, particular, and sticky phenotype, whose expression was extremely stable, even after subcultivation.

Beta-Hemolytic, Multi-Lancefield Antigen-Agglutinating Enterococcus durans from a Pregnant Woman, Mimicking Streptococcus agalactiae

ABSTRACT A beta-hemolytic Lancefield antigen A-, B-, C-, D-, F-, and G-positive Enterococcus durans strain was cultivated from the rectovaginal swab of a pregnant woman who underwent antenatal screening for Streptococcus agalactiae. The isolate raised concern as to what extent similar strains are misrecognized and lead to false diagnosis of group B streptococci.

May Staphylococcus pseudintermedius be non-haemolytic?

However, it is known that S. (pseud)intermedius exhibits typical doublezone haemolysis (Fig. 1) that is bhaemolytic in the inner band but ahaemolytic (due to b-haemolysin, a sphingomyelinase) on the external one (Devriese et al., 2005; Savini et al., 2013a). Preliminary recognition of this species should then rely on the observation of coagulase-positive staphylococci (CoPS), that do not ferment mannitol (or show a weak and delayed fermentation of this sugar) and produce double-band haemolysis on sheep blood agar (Devriese et al., 2005; Savini et al., 2013a).