Antibiotics for Streptococcus (Strep) Infection
What is streptococcus?
Streptococci are gram-positive bacteria, arranged in pairs or chains, facultative anaerobic, high nutrient requirements, and partially CO2-loving. Growth depends on a special medium, such as a blood-containing medium, that breaks down glucose by isolactic fermentation. There are many kinds of non-contact enzymes, most of which are normal bacteria in the human body, and a few can cause disease or condition disease. They are common pathogens in humans and animals and can cause a variety of infections, including streptococcal pharyngitis, scarlet fever, skin infections, and serious invasive diseases such as necrotizing fasciitis. Streptococcal infections can be spread through direct contact or droplets, especially in crowded environments where the risk of infection is higher.
Common classification of streptococcus
Mitis streptococcus, also known as α-hemolytic streptococcus, is a normal living bacteria in the human respiratory tract and intestine. Its pathogenicity is relatively low, but it can cause infection under certain conditions.
Group A Streptococcus (GAS), also known as Streptococcus pyogenes, is a Gram-positive β-hemolytic streptococcus. GAS is mainly distributed in the throat and is the most virulent bacteria in streptococcus, accounting for about 90% of streptococcal infections. The most common is GAS pharyngitis, commonly known as strep throat. In the United States, 5% to 15% of adults and 15% to 35% of children with pharyngitis have GAS infections. Globally, GAS infections and their sequelae (mainly acute kidney failure and rheumatic heart disease) are estimated to cause 500,000 deaths per year.
Group B Streptococcus is a bacterium that often settles and reproduces in the vagina and rectum of pregnant women and can be passed to newborns through the birth canal, causing serious infections such as sepsis, pneumonia and meningitis in newborns.
Streptococcus destroys host cells through a range of toxins and enzymes, triggering local tissue inflammation and a systemic immune response. For example, GAS produces a red rash toxin that is the main cause of scarlet fever, while necrotizing fasciitis is caused by streptococcus destroying muscle tissue by releasing cytolytic cytokines. Streptococcus also produces anti-phagocytic factors (such as the M protein) that help it evade clearance by the host immune system.
Antibiotic for Strep infection at BOC Sciences
Antibiotic production services at BOC Sciences
Antibiotics for strep throat
Strep throat is the most common pharyngitis caused by bacteria, accounting for about 20% to 30% of pharyngitis cases. The incidence of GAS pharyngitis is highest in school age, mainly at the age of 5 to 15, especially at the age of 7 to 8, and is uncommon before the age of 3. GAS is spread by contact with respiratory secretions of infected people, and the incubation period is usually 2-5 days. The disease is most common in winter and spring. In a small number of patients (0.3% to 3.0%) who are not treated with antibiotics, GAS pharyngitis may cause acute rheumatic fever. Early and appropriate antibiotic treatment is essential to relieve symptoms, prevent transmission, and avoid complications.
Antibiotics target S. pyogenes by inhibiting bacterial cell wall synthesis or protein synthesis, leading to bacterial cell death or inhibition of growth. The choice of antibiotic depends on its efficacy against Streptococcus species, patient-specific factors (such as allergies), and resistance patterns.
Penicillin
Penicillin remains the first-line treatment for strep throat due to its high efficacy, low cost, and the absence of reported resistance in S. pyogenes. As a beta-lactam antibiotic, penicillin inhibits the bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to bacterial lysis.
Amoxicillin
Amoxicillin, a broader-spectrum beta-lactam antibiotic, is often preferred in pediatric patients due to its better taste and bioavailability. It also acts by inhibiting bacterial cell wall synthesis and has a similar efficacy profile to penicillin. Amoxicillin is usually administered in a single daily dose, making it a more convenient option, especially for younger children.
Macrolides
For patients allergic to penicillin, macrolide antibiotics such as erythromycin or azithromycin are commonly prescribed. These antibiotics inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit of the bacteria, preventing the translation process. However, resistance to macrolides in S. pyogenes has been reported in some regions, raising concerns about their long-term effectiveness.
Cephalosporins
Cephalosporins, such as cephalexin, are often used as second-line agents for penicillin-allergic patients who cannot tolerate macrolides. They also inhibit bacterial cell wall synthesis and offer a broader spectrum of activity. Cephalosporins have been found to be more effective than penicillin in some studies due to better pharmacokinetic properties, but they are generally reserved for cases of treatment failure or in patients with recurrent infections.
Clindamycin
Clindamycin is a lincosamide antibiotic that is particularly effective against recurrent or chronic strep throat infections. It inhibits protein synthesis by binding to the 50S ribosomal subunit, similar to macrolides. Clindamycin is especially useful for patients with macrolide-resistant S. pyogenes infections or when abscess formation is suspected.
Antibiotic resistance in Group A Streptococcus
Resistance to beta-lactam antibiotic
Although GAS is usually sensitive to β-lactam antibiotics (such as penicillin), recent studies have found that the resistance of GAS to β-lactam drugs in vivo is related to the reduced sensitivity of the strain to drugs, the inoculation effect of bacteria, the formation of biofilm, the action of co-existing bacteria, the retention of bacteria, and the ability of bacteria to internalize into the cell.
Resistance to macrolides
The resistance of GAS to macrolides is mainly determined by two gene families, namely mefA and erm genes. The effector pump encoded by the mefA gene enables bacteria to push drugs out of the cell, while the ribosome methylase encoded by the erm gene creates resistance by modifying the ribosome so that drugs cannot bind properly.
Resistance to lincoamide
Mediated by the lsaE-lnuB gene island, it expresses resistance to lincoamides while remaining sensitive to macrolides.
Resistance to tetracycline
It is produced by ribosome protective genes (such as tetM or tetO) and efflux pump genes (such as tetK).
Group A Streptococcus infection prevention
Globally, GAS infections and their complications are an important public health challenge, especially in economically disadvantaged regions. Therefore, public health policies should focus on preventing the spread of GAS.
General prevention: At the individual level, maintain good personal hygiene, hand hygiene and respiratory hygiene to effectively reduce the transmission of various GAS infections; Improve living conditions to avoid overcrowding. At the level of health care facilities, focus on environmental cleanliness and hygiene to reduce the chance of transmission of infection. At the national level, health education and publicity should be strengthened to raise public awareness of GAS pharyngitis prevention. In addition, early and accurate diagnosis and treatment are effective preventive measures for GAS infection.
Vaccine development: Research on GAS vaccines is ongoing, but there are currently no commercially available GAS vaccines.
Streptococcus b antibiotics
Group B Streptococcus (GBS), also known as agalactis streptococcus, is a kind of opportunistic bacteria, mainly parasitic in the human genitourinary tract and lower digestive tract. Neonatal infection with GBS can cause neonatal meningitis, pneumonia, sepsis and so on.
Penicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis. It binds to penicillin-binding proteins (PBPs), leading to cell lysis and death. In order to prevent severe allergic reactions caused by penicillin, macrolides such as erythromycin, lincomycin such as clindamycin, quinolones and aminoglycosides are often used as second-line drugs. With the increase of antimicrobial resistance rate, their therapeutic effect also has certain limitations, and then the last line of defense vancomycin is used, but there have been reports of vancomycin resistant GBS isolates.
