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Streptococcus dysgalactiae subsp. equisimilis Isolated From Infections in Dogs and Humans: Are Current Subspecies Identification Criteria accurate?

ABSTRACT: Streptococcus dysgalactiae is a pyogenic species pathogenic both for humans and animals. Until recently, it has been considered an exclusive animal pathogen causing infections in wild as well as domestic animals. Currently, human infections are being reported with increasing frequency, and their clinical picture is often similar to the ones caused by Streptococcus pyogenes. Due to the fact that S. dysgalactiae is a heterogeneous species, it was divided into two subspecies: S. dysgalactiae subsp. equisimilis (SDSE) and S. dysgalactiae subsp. dysgalactiae (SDSD). The first differentiation criterion, described in 1996, was based on strain isolation source. Currently applied criteria, published in 1998, are based on hemolysis type and Lancefield group classification. In this study, we compared subspecies identification results for 36 strains isolated from clinical cases both in humans and animals. Species differentiation was based on two previously described criteria as well as MALDI-TOF and genetic analyses: RISA and 16S rRNA genes sequencing. Antimicrobial susceptibility profiles were also determined according to CLSI guidelines. The results presented in our study suggest that the subspecies differentiation criteria previously described in the above two literature positions seem to be inaccurate in analyzed group of strains, the hemolysis type on blood agar, and Lancefield classification should not be here longer considered as criteria in subspecies identification. The antimicrobial susceptibility tests indicate emerging of multiresistant human SDSE strains resistant also to vancomycin, linezolid and tigecycline, which might pose a substantial problem in treatment.

SUBMITTER: Ciszewski M

PROVIDER: S-EPMC5039219 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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Streptococcus dysgalactiae subsp. equisimilis Isolated From Infections in Dogs and Humans: Are Current Subspecies Identification Criteria accurate?

Ciszewski Marcin M Zegarski Kamil K Szewczyk Eligia M EM

Current microbiology 20160809 5

Streptococcus dysgalactiae is a pyogenic species pathogenic both for humans and animals. Until recently, it has been considered an exclusive animal pathogen causing infections in wild as well as domestic animals. Currently, human infections are being reported with increasing frequency, and their clinical picture is often similar to the ones caused by Streptococcus pyogenes. Due to the fact that S. dysgalactiae is a heterogeneous species, it was divided into two subspecies: S. dysgalactiae subsp. ...[more]

PMID: 27502064

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Project description:BACKGROUND:During the past decades, Streptococcus dysgalactiae subspecies equisimilis (SDSE) has been increasingly recognized as an important human pathogen. Osteoarticular infections is one of the predominant disease manifestations of SDSE, but the pathogenetic rationale for its arthritogenicity has yet to be unravelled. We aimed to explore if the rising incidence of osteoarticular infections caused by this pathogen in our region emanated from clonal expansion of strains with enhanced tropism for bone and joint tissue components or orthopaedic implants. RESULTS:Twenty-nine SDSE-isolates associated with osteoarticular infections were retrospectively identified. Their genomic content and affinity for fibronectin, collagen and stainless steel were compared to 24 temporally and geographically matched SDSE blood culture isolates obtained from patients without bone or joint infections. Despite a thorough genetic and phenotypic dissection, neither the presence or absence of any single gene, nor the binding abilities of the SDSE isolates, were predictive of clinical entity. SNP analysis revealed a heterogenous population, and a correlation between phylogenetic relationships and disease manifestation was not evident. However, we identified a strong concordance between phenotypic binding abilities and genetic variations in the pilus-region, also denoted as the FCT-region (Fibronectin binding, Collagen binding and T-antigen). This observation could be related to the ample and varied repertoire of putative adhesins residing within this region, including proteins predicted to adhere to fibronectin and collagen, as well as fibrinogen. CONCLUSIONS:SDSE strains associated with osteoarticular infections do not emanate from subpopulation characterized by distinct genetic or phenotypic traits. The genetic architecture of the pilus region was predictive of the adhesive properties of the SDSE-isolates, but its role in tissue tropism needs further investigation. To the best of our knowledge, this is the first comprehensive characterization of the genetic landscape of the SDSE pilus region.

Project description:Streptococcus dysgalactiae subsp. equisimilis (SDSE) is an emerging human pathogen that causes severe invasive streptococcal diseases. Recent reports have shown that SDSE exhibits high pathogenicity with different mechanisms from that of Streptococcus pyogenes, although the two streptococci possess some common virulence factors such as streptolysin, streptokinase, and cell-binding proteins. To date, only a few studies have examined the variety of mechanisms expressing the pathogenicity of SDSE. Among nine SDSE clinical isolates sequenced in this study, we present in vitro and in vivo analyses of KNZ01 and KNZ03, whose emm and multilocus species types (MLSTs) are prevalent in Japan and other countries. For the comparison of pathogenicity, we also utilized the ATCC 12394 strain. The whole-genome analysis showed that KNZ03 and ATCC 12394 are categorized into an identical clonal complex by MLST and are phylogenetically close. However, the three strains exhibited different characteristics for pathogenicity in vitro; ATCC 12394 showed significant cytotoxicity to human keratinocytes and release of streptolysin O (SLO) compared to KNZ01 and KNZ03; KNZ03 exhibited significantly high hemolytic activity, but did not secrete SLO. KNZ01 and KNZ03 adhered to human keratinocytes at a higher rate than ATCC 12394; KNZ03 showed a higher rate of survival after a brief (30 min) incubation with human neutrophils compared to the other two strains; also, KNZ01 grew more rapidly in the presence of human serum. In vivo subcutaneous infection commonly resulted in ulcer formation in the three strains 7 days after infection. KNZ01-infected mice showed significant body weight loss 2 days after infection. Besides, on post-infection day 2, only KNZ01 remained in the cutaneous tissues of mice. Scanning electron microscopy analysis revealed that KNZ01 formed an extracellular structure (biofilm), which was probably composed of cell wall-anchoring proteins, in the presence of glucose and human serum. The extracellular structure of ATCC 12394 was also changed dramatically in response to culture conditions, whereas that of KNZ03 did not. Our study proposed that each SDSE strain possesses different virulence factors characteristics for mediating pathogenicity in humans.

Project description:Streptococcus dysgalactiae subsp. equisimilis (SDSE) causes cellulitis, bacteremia, and invasive diseases, such as streptococcal toxic shock syndrome. Although SDSE infection is more prevalent among elderly individuals and those with diabetes mellitus than infections with Streptococcus pyogenes (Group A streptococci; GAS) and Streptococcus agalactiae (Group B streptococci; GBS), the mechanisms underlying the pathogenicity of SDSE remain unknown. SDSE possesses a gene hylD encoding a hyaluronate lyase (HylD), whose homologue (HylB) is involved in pathogenicity of GBS, while the role of HylD has not been characterized. In this study, we focused on the enzyme HylD produced by SDSE; HylD cleaves hyaluronate (HA) and generates unsaturated disaccharides via a ?-elimination reaction. Hyaluronate-agar plate assays revealed that SDSE promoted dramatic HA degradation. SDSE expresses both HylD and an unsaturated glucuronyl hydrolase (UGL) that catalyzes the degradation of HA-derived oligosaccharides; as such, SDSE was more effective at HA degradation than other ?-hemolytic streptococci, including GAS and GBS. Although HylD shows some homology to HylB, a similar enzyme produced by GBS, HylD exhibited significantly higher enzymatic activity than HylB at pH 6.0, conditions that are detected in the skin of both elderly individuals and those with diabetes mellitus. We also detected upregulation of transcripts from hylD and ugl genes from SDSE wild-type collected from the mouse peritoneal cavity; upregulated expression of ugl was not observed in ?hylD SDSE mutants. These results suggested that disaccharides produced by the actions of HylD are capable of triggering downstream pathways that catalyze their destruction. Furthermore, we determined that infection with SDSE?hylD was significantly less lethal than infection with the parent strain. When mouse skin wounds were infected for 2 days, intensive infiltration of neutrophils was observed around the wound areas infected with SDSE wild-type but not SDSE?hylD. Our investigation suggested that HylD and UGL play important roles in nutrient acquisition from hosts, followed by the bacterial pathogenicity damaging host tissues.

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Streptococcus dysgalactiae subsp. equisimilis Isolated From Infections in Dogs and Humans: Are Current Subspecies Identification Criteria accurate?

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Streptococcus dysgalactiae subsp. equisimilis Isolated From Infections in Dogs and Humans: Are Current Subspecies Identification Criteria accurate?

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