A molecular trigger for intercontinental epidemics of group A Streptococcus
The Journal of Clinical Investigation
|August 11, 2015
Summary
A specific genetic change in Group A Streptococcus M1 strains drives increased toxin production and severity, leading to pandemics. Similar events also fuel M89 strain epidemics, impacting millions globally.
Area of Science:
- Infectious Diseases
- Microbiology
- Genetics
Background:
- Identifying molecular drivers of infectious disease outbreaks is crucial.
- Group A Streptococcus (GAS) causes significant human illness, with specific strains leading to pandemics.
Purpose of the Study:
- To identify the molecular basis for the emergence and enhanced virulence of pandemic M1 Group A Streptococcus strains.
- To investigate a similar mechanism in ongoing M89 Group A Streptococcus epidemics.
Main Methods:
- Genomic analysis of 3,615 M1 GAS strains and 1,125 additional strains.
- Construction and testing of isoallelic mutant strains.
- Virulence studies in animal models (pharyngitis, necrotizing fasciitis).
Main Results:
- A recombination event replacing a toxin gene region is linked to the M1 pandemic.
- Specific polymorphisms in this region enhance toxin production, resist immune killing, and increase virulence.
- A similar recombination event drives M89 GAS epidemics.
Conclusions:
- Allelic variation in toxin genes is a key driver of GAS pandemic and epidemic strains.
- These molecular changes enhance bacterial fitness, immune evasion, and tissue destruction.
- Understanding these mechanisms is vital for addressing widespread streptococcal infections.
Related Concept Videos
01:18Bacterial Gastroenteritis
48
Bacterial gastroenteritis, characterized by diarrhea, abdominal cramps, and vomiting, is often caused by ingestion of contaminated food or water and is frequently associated with pathogenic Escherichia coli strains. These microbes exploit two principal mechanisms to inflict disease.Shiga toxin–producing E. coli, also referred to as STEC—notably O157:H7—release Shiga toxins that target ribosomes, blocking protein synthesis. The B subunit of the toxin binds the host glycolipid...
48
01:30Bacterial Phylum Spirochaetes
1.2K
Spirochetes, unique bacteria in the phylum Spirochaetes, are gram-negative, motile, tightly coiled, slender, and flexible. They inhabit aquatic sediments and animals, with some causing diseases like syphilis. Spirochetes are classified into eight genera based on habitat, pathogenicity, phylogeny, and characteristics.Their distinctive motility arises from endoflagella, located within the cell’s periplasm. These endoflagella anchor at the cell poles and extend along the cell length, encased...
1.2K
01:25Clinical Significance of Antibiotic Resistance
41
Methicillin-resistant Staphylococcus aureus (MRSA) presents a critical public health threat, arising from its capacity to resist β-lactam antibiotics due to acquisition of the mecA gene within the staphylococcal cassette chromosome mec (SCCmec). This gene encodes penicillin-binding protein 2a (PBP2a), which impairs binding efficacy of methicillin and other β-lactams. MRSA has evolved into distinct clonal lineages impacting humans and animals alike, reinforcing its significance within...
41
01:29Staphylococcal Skin Infections
76
Staphylococcus aureus is a Gram-positive coccus that resides harmlessly on the skin and mucous membranes of healthy individuals. When the skin barrier is breached, it can shift from a commensal to an opportunistic pathogen. This transition is facilitated by surface adhesins, such as clumping factor B and S. aureus surface protein G (SasG), which bind to structural proteins, including loricrin and cytokeratin, in the damaged epidermis. Protein A, another key factor, binds the Fc region of...
76
01:28Regulation of Bacterial Virulence
41
Pathogenic bacteria employ a range of regulatory mechanisms to modulate the expression of virulence genes in response to environmental and host-derived signals. These mechanisms ensure that virulence factors are expressed only under favorable conditions, thereby optimizing infection and survival strategies.Mechanisms of Virulence RegulationKey regulatory strategies include:Two-Component Systems: These consist of a membrane-bound sensor kinase and a cytoplasmic response regulator. Environmental...
41
01:10Intracellular Movement of Viruses and Bacteria
3.8K
Intracellular bacteria and viruses often comprise a group of highly infectious pathogens that can cause several diseases. Bacterial pathogens include those belonging to the genus Rickettsia responsible for conditions such as rocky mountain spotted fever and the Mediterranean spotted fever; Chlamydia, a genus responsible for a sexually transmitted disease; Coxiella burnetii, an agent responsible for Q fever. Viral pathogens include vaccinia—a poxvirus, and herpes simplex virus—a...
3.8K