Klaudia Polakowska

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.

The virulence of Staphylococcus aureus correlates with strain genotype in a chicken embryo model but not a nematode model

Staphylococcus aureus infections are of major importance in human and veterinary medicine. Studies of the virulence of this bacterium are complicated by inconsistent results obtained in different animal models. We searched for an uncomplicated and inexpensive model suitable to study virulence of poultry strains of S. aureus using a genome-wide approach. We determined that a useful model would clearly differentiate strains of high and low virulence, and that this would generally correlate with the genetic relatedness among strains. To this end Gallus gallus (chicken) embryo and Caenorhabditis elegans (nematode) models were selected, and their response to challenge by a set of well-characterized Staphylococcus strains was evaluated. The chicken embryo model allowed to determine variation in virulence among strains of poultry and human origin. The survival of embryos ranged from 0% to almost 100% for the various strains. In contrast, variation in virulence of most strains in the nematode model was comparable, regardless of their origin or genotype, demonstrating limited usefulness of this model. Most importantly, a clear correlation was found between the virulence level in the embryo model and the genotype of the tested poultry strains. Our findings indicate the potential usefulness of embryo model for future identification of host-specific adaptations and virulence factors in S. aureus.

Identification of Secreted Exoproteome Fingerprints of Highly-Virulent and Non-Virulent Staphylococcus aureus Strains

Staphylococcus aureus is a commensal inhabitant of skin and mucous membranes in nose vestibule but also an important opportunistic pathogen of humans and livestock. The extracellular proteome as a whole constitutes its major virulence determinant; however, the involvement of particular proteins is still relatively poorly understood. In this study, we compared the extracellular proteomes of poultry-derived S. aureus strains exhibiting a virulent (VIR) and non-virulent (NVIR) phenotype in a chicken embryo experimental infection model with the aim to identify proteomic signatures associated with the particular phenotypes. Despite significant heterogeneity within the analyzed proteomes, we identified alpha-haemolysin and bifunctional autolysin as indicators of virulence, whereas glutamylendopeptidase production was characteristic for non-virulent strains. Staphopain C (StpC) was identified in both the VIR and NVIR proteomes and the latter fact contradicted previous findings suggesting its involvement in virulence. By supplementing NVIR, StpC-negative strains with StpC, and comparing the virulence of parental and supplemented strains, we demonstrated that staphopain C alone does not affect staphylococcal virulence in a chicken embryo model.

Species determination within Staphylococcus genus by extended PCR-restriction fragment length polymorphism of saoC gene

Genetic methods based on PCR-restriction fragment length polymorphism (RFLP) are widely used for microbial species determination. In this study, we present the application of saoC gene as an effective tool for species determination and within-species diversity analysis for Staphylococcus genus. The unique sequence diversity of saoC allows us to apply four restriction enzymes to obtain RFLP patterns, which appear highly distinctive even among closely related species as well as atypical isolates of environmental origin. Such patterns were successfully obtained for 26 species belonging to Staphylococcus genus. What is more, tracing polymorphisms detected by different restriction enzymes allowed for basic phylogeny analysis for Staphylococcus aureus, which is potentially applicable for other staphylococcal species.

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.

Multiple-locus variable-number tandem repeat fingerprinting as a method for rapid and cost-effective typing of animal-associated Staphylococcus aureus strains from lineages other than sequence type 398

In veterinary medicine, Staphylococcus aureus is associated with a range of mild to severe infections. The high density of livestock in intensive farming systems increases the risk of disease spread and hampers its control and measures of prevention, making S. aureus one of the most important animal pathogens. Multiple-locus variable-number tandem repeat fingerprinting (MLVF) has been successfully applied to the characterization of livestock-associated meticillin-resistant Staphylococcus aureus (MRSA) ST398 but not to the characterization of a wide range of other animal isolates. The objective of the current study was to examine the effectiveness of MLVF for studying S. aureus strains isolated from households, farms and exotic animals in three regions of Poland. MLVF, random amplification of polymorphic DNA (RAPD), spa typing and diagnostic microarrays were compared to determine the most suitable combination of methods for veterinary purposes. MLVF generated results consistent with host and geographic origins, reflecting population structures with a high concordance to spa typing results. MLVF has been proven to be a rapid, highly discriminatory and cost-effective method suitable for molecular typing in veterinary settings.

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).