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How does this bacterium cause alarming diseases in humans and animals?
In the bacterial kingdom, there are a group of bacteria called Streptococci that are of particular interest, one of which is Streptococcus dysgalactiae. This is a Gram-positive, beta-hemolytic, spherical bacterium belonging to the family Streptococcus. It has the ability to infect humans and animals, but is most often found as a commensal in the digestive tract, sexual reproductive tract, or occasionally as part of the skin flora. Diseases caused by this bacterium, such as superficial infections and tonsillitis, have a wide range of clinical manifestations and may even progress to life-threatening necrotizing fasciitis and bacteremia. In recent years, the incidence of invasive disease has been increasing, raising questions about its true pathogenicity.
Human infections with Streptococcus dysgalactiae are increasing, and in some areas, rates of invasive infection exceed those of Streptococcus pyogenes.
Epidemiology
In the past, the scientific community generally believed that Streptococcus dysgalactiae was harmless to humans. However, recent studies show that infections caused by this bacterium are increasing, especially among older adults. The age distribution shows that invasive cases are more common in the elderly, while healthy carriers are mainly concentrated in younger people. Patients facing chronic diseases, such as cancer and diabetes, are at higher risk for infection, and these characteristics have been viewed as possible reasons for the increased incidence of invasive disease. In addition, the proportion of male patients appears to be higher, presumably related to the burden of comorbidities.
Role in human disease
Streptococcus dysgalactiae subspecies equisimilis is commonly found in the human digestive and reproductive tracts and is occasionally detected in the skin, usually in association with chronic skin diseases or disruption of the epithelial barrier. Non-invasive diseases caused by this bacterium mainly include tonsillitis and superficial infections. The possible role of this bacterium in cellulitis/lymphadenitis has long been known, and recent studies suggest that its role in cellulitis may be underestimated. In addition, this bacterium is also classified as an important causative agent of bone and joint infections, and the incidence of such cases is increasing.
Streptococcus dysgalactiae subspecies equisimilis is currently associated with acute rheumatic fever and poststreptococcal tubulonephritis, which was previously associated only with Streptococcus pyogenes.
Role in animal diseases
Streptococcus dysgalactiae not only affects humans but also infects a variety of animal hosts, and both subspecies play an important role in veterinary medicine. This bacterium is commonly found as a colonizer of healthy animals, especially in the digestive tract and reproductive areas. In veterinary medicine, this bacterium is an important pathogen of dairy cow mastitis, and the clinical and subclinical mastitis caused by it is second only to Staphylococcus aureus in some areas. This pathogenic bacterium is particularly associated with summer mastitis and is thought to be caused by flying insects. In addition, this bacterium has been associated with infectious arthritis in a variety of animals and plays an important role in neonatal mortality in puppies.
Treatment and antibiotic susceptibility
Based on current research, penicillin remains the drug of choice for the treatment of streptococcal infections, and reduced susceptibility to penicillin has never been reported in Streptococcus dysgalactiae. Treatment duration ranges from 5 days to 3 months, depending on the diagnosis, and second-line drugs such as macrolides and clindamycin, although increasing resistance has been observed in some areas, do not affect Penicillin use. In contrast, aminoglycosides, which have never been active against streptococci, show synergistic effects when combined with β-lactam antibiotics. Streptococcus dysgalactiae has consistent sensitivity to glyceroglycans and oxyurea, which allows for greater treatment options.
Future challenges and discussions
Even though the pathogenesis of Streptococcus dysgalactiae remains to be explored in depth, several causative factors have been identified. M protein is widely regarded as its most important pathogenic factor, which can promote attachment and internalization to host cells. These properties may explain why this bacterium causes recurrent bacteremia after infection.
New generation detection technologies, such as endonuclease and single nucleotide polymorphism analysis, are critical to understanding the potential variability in this bacterial development.
In the context of the widespread use of antibiotics and the evolution of bacteria, how to effectively control the disease caused by this bacteria will become a major challenge for the medical community. In the future, whether a more effective solution can be found to face this well-known and What about the mysterious bacteria?
