Potential Factors Enabling Human Body Colonization by Animal Streptococcus dysgalactiae subsp. equisimilis Strains
Curr Microbiol
Potential Factors Enabling Human Body Colonization by Animal Streptococcus dysgalactiae subsp. equisimilis Strains
Marcin Ciszewski 0
Eligia M. Szewczyk 0
0 Department of Pharmaceutical Microbiology and Microbiological Diagnostics, Medical University of Łódź , 137 Pomorska St., 90-235 Lodz , Poland
1 Marcin Ciszewski
Streptococcus dysgalactiae subsp. equisimilis (SDSE) is a pyogenic, Lancefield C or G streptococcal pathogen. Until recently, it has been considered as an exclusive animal pathogen. Nowadays, it is responsible for both animal infections in wild animals, pets, and livestock and human infections often clinically similar to the ones caused by group A streptococcus (Streptococcus pyogenes). The risk of zoonotic infection is the most significant in people having regular contact with animals, such as veterinarians, cattlemen, and farmers. SDSE is also prevalent on skin of healthy dogs, cats, and horses, which pose a risk also to people having contact with companion animals. The main aim of this study was to evaluate if there are features differentiating animal and human SDSE isolates, especially in virulence factors involved in the first stages of pathogenesis (adhesion and colonization). Equal groups of human and animal SDSE clinical strains were obtained from superficial infections (skin, wounds, abscesses). The presence of five virulence genes (prtF1, prtF2, lmb, cbp, emm type) was evaluated, as well as ability to form bacterial biofilm and produce BLIS (bacteriocin-like inhibitory substances) which are active against human skin microbiota. The study showed that the presence of genes coding for fibronectin-binding protein and M protein, as well as BLIS activity inhibiting the growth of Corynebacterium spp. strains might constitute the virulence factors which are necessary to colonize human organism, whereas they are not crucial in animal infections. Those virulence factors might be horizontally transferred from human streptococci to animal SDSE strains, enabling their ability to colonize human organism.
Streptococcus dysgalactiae subsp; equisimilis; Animal-to-human transfer; Virulence factors; Adhesion; Colonization resistance; Biofilm formation
Introduction
Streptococcus dysgalactiae subsp. equisimilis (SDSE) is a
pyogenic pathogen possessing Lancefield C or G antigens.
Until recently, it has been considered as an exclusive
animal pathogen. Nowadays, it is responsible for both animal
infections in wild animals, pets, and livestock [
1–4
] and
human infections often clinically similar to the ones caused
by group A streptococcus (Streptococcus pyogenes) [
5–7
].
According to the outline of evolutionary changes involved
in crossing an animal-to-human interspecies barrier,
presented by Wolfe et al. in Nature [8], SDSE is probably
located on the second stage of this process—it is being
isolated from humans, what has already been reported [
9, 10
];
however, there is no evidence for human-to-human
transfer. Due to the similarity of SDSE and S. pyogenes
virulence factors identified so far, as well as clinical pictures
of human infections caused by these pathogens, horizontal
gene transfer (HGT) between these species has been
suggested [11], especially via bacteriophage transduction
process [
12
]. HGT might also occur between SDSE strains, as
an element of adaptation to the new ecological niche, i.e.,
human organism [
13
].
Bacterial pathogenesis consists of complex set of
mechanisms, comprising adhesion, colonization, and spreading in
the human organism, inactivation of human immunological
system elements as well as production of toxins [
14
]. The
first process, which involves various virulence factors
of animal and human SDSE strains, is adhesion which
comprises biofilm formation, the presence of M protein,
fibronectin, laminin, and collagen binding proteins as well
as the production of BLIS (bacteriocin-like inhibitory
substances) enabling colonization of human skin microbiota
[
15, 16
].
In order to determine factors that might be specific
markers enabling animal SDSE strains to break
interspecies barrier and colonize human organism, the prevalence
of virulence factors involved in adhesion and colonization
processes both in groups of human and animal clinical
SDSE strains has been evaluated and compared.
Materials and Methods
Bacterial Strains
Six human SDSE isolates from superficial infections
(from dermatitis, wounds, bedsores, skin abscesses)
were obtained from Synevo Medical Laboratory in Łódź,
Poland. Six animal SDSE isolates from clinical cases in
pets (dogs—from wounds, skin abscesses) were obtained
from VETCOMPLEX Veterinary Diagnostic Centre in
Łódź, Poland.
Identification
MALDI-TOF technique (matrix-assisted laser desorption
ionization-time of flight) [
17
] which compares cell proteins
specters with database (bioMérieux VITEK® MS) was used
to identify the analyzed clinical strains. All bacterial strains
were also identified by means of RISA ( (...truncated)