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.

Use of MALDI-TOF Mass Spectrometry for the Fast Identification of Gram-Positive Fish Pathogens

“…This characteristic suggests, taking into consideration there is no traceable information for the isolates in addition to the recent studies of S. dysgalactiae spp. (Jensen and Kilian, 2012 ; Ciszewski et al, 2016 ), that a reclassification, based on genomic analyses, should be done for such isolates from the Bruker MSP library.…”

Pathogenicity and drug resistance of animal streptococci responsible for human infections

“…They presented the results of a study in which the α-haemolysis pattern of SDSD changed after 72 h to β-haemolysis [117]. More profound identification to a subspecies is not easy in a diagnostic laboratory and the results of advanced tests may not coincide with the early assignment [118]. SDSE is expected to induce β-haemolysis, degrade human fibrin and produce streptokinase.…”

“…Attempts to identify S. dysgalactiae subspecies using 16S RNA PCR or MALDI-TOF methods often yielded inconclusive or inconsistent results [118].…”

Pathogenicity of Virulent Species of Group C Streptococci in Human

“…To identify S. dysgalactiae subs. equisimilis strains Ciszewski presents the RISA method (analysis of ribosomal intergenic region) [ 19 ]. In the RISA method, in the course of PCR reaction, one uses S. dysgalactiae species-specific primers and SDSE subspecies-specific primers [ 19 ].…”

“…An alternative for the aforementioned molecular identification can be the sequencing of the 16S rRNA, in combination with gyrB gene sequencing generally regarded as a golden standard [ 16 , 19 , 20 ]. Zhou's test confirms that by having examined 181 isolates the similarities with the sequences in GenBank reached over 99% and 96% [ 20 ].…”