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Streptococcal diseases and their complications are among the global problems of international health. S. pyogenes (group A streptococci — GAS) is a pathogen that causes significant morbidity in different countries and different age groups of the population, occurring both sporadically and epidemically. Due to ineffective antibacterial therapy or its absence, 3–5% of people who have had streptococcal infection may develop complications such as acute rheumatic fever, rheumatic heart disease, acute post-streptococcal glomerulonephritis and invasive complications: necrotizing fasciitis and myositis, septicemia and toxic shock syndrome, highly lethal due to the rapid development of the process and systemic organ damage. According to recent estimates, at least 517 000 deaths occur annually in the world due to diseases caused by GAS. The diverse arsenal of pathogenic factors of this pathogen is manifested in a combination of joint or sequential reactions in the process of microbial colonization of tissue, formation of the focus of infection and overcoming the host's defense mechanisms. It is an important point in the process of studying the pathogenesis of diseases caused by these microbes. The pathogenic factors of GAS can be divided into extracellular and associated with the microbial cell, predominantly with its cell wall. The spectrum activity of pathogenicity factors can be quite wide (M proteins, pyrogenic exotoxins, superantigens) or limited (serine and cysteine proteinases, streptokinase). Information about the specificity of pathogenicity factors, their properties, relationships, regulation and specific function in pathology is the task of scientific, as well as complex researches, leading to understanding the pathogen-host interaction. An integrated approach to the investigation of GAS pathogenicity factors is needed to study the pathogenicity of streptococci, since pathogenicity factors do not manifest themselves in isolation and are not always independently regulated. In many cases, regulators control the expression of more than one of them. S. pyogenes has been studied for about 150 years, but a number of issues related to their pathogenicity remain unknown to this day. Some factors need more in-depth study: for example, endo-β-N-acetylglucosaminidase, arginine deiminase. Immunoglobulin-degrading enzymes require special attention due to their possible participation in the genesis of immunopathological processes of streptococcal etiology. This review summarizes the literature data about most of the pathogenicity factors of S. pyogenes and their role in the infectious process.

Background and Aim: Pseudomonas aeruginosa is a relevant opportunistic and difficult to treat pathogen due to its widespread environmental diffusion, intrinsic resistance to many classes of antimicrobials, high ability to acquire additional resistance mechanisms, and wide range of pathogenic factors. The present study aimed to investigate the prevalence of P. aeruginosa in canine clinical samples, the antimicrobial susceptibility against antipseudomonal antibiotics, and the presence of extracellular pathogenic factors of the isolates, as well as their ability to produce biofilm. Materials and Methods: Overall, 300 clinical specimens from dogs with pyoderma or abscesses (n=58), otitis (n=59), and suspected bladder infection (n=183) were analyzed by standard bacteriological methods. P. aeruginosa isolates were tested for their antimicrobial susceptibility by disk and gradient diffusion methods to determine the minimum inhibitory concentrations. The ability of the isolates to produce biofilm was investigated by a microtiter plate assay, while virulence genes coding for elastase (lasB), exotoxin A (toxA), alkaline protease (aprA), hemolytic phospholipase C (plcH), and exoenzyme S (ExoS) were detected by polymerase chain reaction method. Results: A total of 24 isolates of P. aeruginosa were found in clinical specimens (urine n=3, skin/soft tissue n=6, and ear canal n=15). No resistance was found to ceftazidime, gentamicin, aztreonam, and imipenem (IMI), while low levels of resistance were found to enrofloxacin (ENR) (4.2%) and piperacillin-tazobactam (8.3%). However, 41.7% and 29.2% of the isolates showed intermediate susceptibility to ENR and IMI, respectively. Disk and gradient diffusion methods showed high concordance. The majority of the isolates revealed a weak (33.3%) or intermediate (45.8%) ability to form biofilm, while the strong biofilm producers (20.8%) derived exclusively from the ear canal samples. All isolates (100%) were positive for lasB, aprA, and plcH genes, while exoS and toxA were amplified in 21 (87.5%) and 22 (91.7%) isolates, respectively. Conclusion: In the present study, P. aeruginosa isolates from canine clinical samples were characterized by low levels of antimicrobial resistance against antipseudomonal drugs. However, the high presence of isolates with intermediate susceptibility for some categories of antibiotics, including carbapenems which are not authorized for veterinary use, could represent an early warning signal. Moreover, the presence of isolates with strong ability to produce biofilm represents a challenge for the interpretation of the antimicrobial susceptibility profile. In addition, the high prevalence of the extracellular pathogenic factors was indicative of the potential virulence of the isolates.