Characterization of agr Groups of Staphylococcus pseudintermedius Isolates from Dogs in Texas

Abstract

Staphylococcus pseudintermedius is an important canine pathogen implicated in an increasing number of human infections. Along with rising levels of methicillin and multidrug resistance, staphylococcal biofilms are a complicating factor for treatment and contribute to device, implant, and surgical infections. Staphylococcal virulence, including biofilm formation, is regulated in part by the quorum sensing accessory gene regulator system (agr). The signal molecule for agr, known as the autoinducing peptide molecule, contains polymorphisms that result in the formation of distinct groups. In S. pseudintermedius, 4 groups (i.e., groups I, II, III, and IV) have been identified but not comprehensively examined for associations with infection type, virulence factor carriage, or phylogenetic relationships—all of which have been found to be significant in S. aureus. In this study, 160 clinical canine isolates from Texas, including isolates from healthy dogs (n = 40) and 3 different infection groups (pyoderma, urinary tract, and surgical, n = 40 each), were sequenced. The agr group, biofilm-producing capabilities, toxin gene carriage, antimicrobial resistance, and sequence type (ST) were identified for all isolates. While no significant associations were discovered among the clinical infection types and agr groups, agr II isolates were significantly less common than any other group in diseased dogs. Furthermore, agr II isolates were less likely than other agr groups to be multidrug resistant and to carry toxin genes expA and sec-canine. Fifty-two (33%) of the 160 isolates were methicillin resistant, and the main sequence types (ST64, ST68, ST71, ST84, ST150, and ST155) of methicillin-resistant strains of S. pseudintermedius (MRSP) were identified for the geographic region. IMPORTANCE Staphylococcus pseudintermedius is an important disease-causing bacterium in dogs and is recognized as a growing threat to human health. Due to increasing multidrug resistance, discovery of alternative methods for treatment of these infections is vital. Interference with one target for alternative treatment, the quorum sensing system agr, has demonstrated clinical improvement of infections in S. aureus animal models. In this study, we sequenced and characterized 160 clinical S. pseudintermedius isolates and their agr systems in order to increase understanding of the epidemiology of the agr group and clarify its associations with types of infection and antimicrobial resistance. We found that isolates with agr type II were significantly less common than other agr types in diseased dogs. This provides valuable information to veterinary clinical microbiologists and clinicians, especially as less research has been performed on infection associations of agr and its therapeutic potential in S. pseudintermedius than in S. aureus.

Investigation on Antibiotic-Resistance, Biofilm Formation and Virulence Factors in Multi Drug Resistant and Non Multi Drug Resistant Staphylococcus pseudintermedius

“…The prevalence of agr groups in our clinical isolates is very different to that described by Little et al [7], with agrI being the unique group found in our collection, while any of the strains were assigned to one of the other three (agr II, III and IV). Following the suggestions of the author, in this contest, it is not possible to correlate the ability to produce biofilm with the corresponding agr group.…”

“…Following the suggestions of the author, in this contest, it is not possible to correlate the ability to produce biofilm with the corresponding agr group. Little et al (2019) stated that strains harboring agrI were more prone to produce biofilm and to be MDR [7]. Our findings indicate a major ability for MDR bacteria to be strong biofilm producers.…”

“…To confirm data from MtP assay, the detection of two pivotal genes of ica locus (icaA and icaD) was performed by conventional qualitative PCR (see Table 1) using primer according to literature [14]. Taking into account that the ability to produce biofilm could be associated with a specific antibiotic-resistance profile [7,36], the agr locus was analyzed with two duplex PCRs for the determination of agr type (I-IV), as previously reported [27]. For the two duplex PCRs, the already described AccuPrime TM Taq DNA Polymerase system (Thermo Fisher Scientific, Monza (MB), Lombardy, Italy) was used.…”

“…It is an opportunistic pathogen also known as one of the leading cause of skin, ear, and post-surgical infections in domestic animals, especially in dogs [4][5][6]. Even if infections in humans are less common than those reported in pets, the description of S. pseudintermedius as a human pathogen is being increasingly reported [7][8][9], however little is known about its pathogenesis and distribution, and in human medicine is still misdiagnosed as S. aureus [10]. A progressive expansion in resistance to commonly prescribed antimicrobial agents has been observed in the past years, in particular with the emergence and the global spread of multi drug resistant (MDR) bacteria with particular regards for the Methicillin Resistant S. pseudintermedius (MRSP) clones that dramatically complicate the treatment of these infections [7,11].…”

“…To form a biofilm, bacteria require at least two features: a) Adherence to a surface, and b) the possibility to accumulate it in order to form a multi-layered complex structure. The ability to form a biofilm resides in the formation of an extracellular matrix known as polysaccharide intercellular adhesion molecule (PIA), that is encoded by the ica operon, including four distinct genes (A, B, C, and D) [7,12,14]. The biofilm forming ability of S. pseudintermedius has been reported by different authors but nowadays is still not fully understood; in a recent study Stefanetti et al [11,15], up to 96% of canine SP strains was able to produce biofilm.…”