Question

Streptococcus pyogenes

• Disease(s) information
• Number of cases and deaths per year information
• Transmission information
• Taxonomy information
• Signs and symptoms information
• Identification information
• Prevention and treatment information
• Sources information

Answer 1

Streptococcus pyogenes is an aerobic, gram-positive extracellular bacterium. It is made up of non-motile, non-sporing cocci that are less then 2 µm in length and that form chains and large colonies greater then 0.5 mm in size. It has a β-hemolytic growth pattern on blood agar and there are over 60 different strains of the bacterium.

This bacterium is responsible for a wide array of infections. It can cause streptococcal sore throat which is characterized by fever, enlarged tonsils, tonsillar exudate, sensitive cervical lymph nodes and malaise. If untreated, strep throat can last 7-10 days. Scarlet fever (pink-red rash and fever) as well as impetigo (infection of the superficial layers of skin) and pneumonia are also caused by this bacterium. Septicaemia, otitis media, mastitis, sepsis, cellulitis, erysipelas, myositis, osteomyelitis, septic arthritis, meningitis, endocarditis, pericarditis, and neonatal infections are all less common infections due to S. pyogenes. Streptococcal toxic shock syndrome, acute rheumatic fever (joint inflammation, carditis and CNS complications), post-streptococcal glomerulonephritis (inflammation, hematuriia, fever, edema, hypertension, urinary sediment abnormalties and severe kidney pain) and necrotizing fasciitis (rapid and progressive infection of subcutaneous tissue, massive systematic inflammation, hemorrhagic bullae, crepitus and tissue destruction) are some of the more serious complications involving S. pyogenes infections.

There are at least 517,000 deaths globally each year due to severe S. pyogenes infections and rheumatic fever disease alone causes 233,000 deaths. 1,800 invasive S. pyogenes disease-related deaths are reported in the USA yearly, necrotizing fasciitis kills about 30% of patients and streptococcal toxic shock syndrome has a mortality rate of 30-70%.

Streptococcal bacteria are highly contagious. They can spread through airborne droplets when someone with the infection coughs or sneezes, or through shared food or drinks. You can also pick up the bacteria from a doorknob or other surface and transfer them to your nose, mouth or eyes. It is rarely transmitted by indirect contact through objects.

Domain: Bacteria
Phylum: Firmicutes
Class: Bacilli
Order: Lactobacillales
Family: Streptococcaceae
Genus: Streptococcus
Species: Streptococcus pyogenes

Signs and symptoms can include:

• Throat pain that usually comes on quickly
• Painful swallowing
• Red and swollen tonsils, sometimes with white patches or streaks of pus
• Tiny red spots on the area at the back of the roof of the mouth (soft or hard palate)
• Swollen, tender lymph nodes in your neck
• Fever
• Headache
• Rash
• Nausea or vomiting, especially in younger children
• Body aches

Streptococci are non-motile, microaerophilic, Grampositive spherical bacteria (cocci). They often occur as chains or pairs and are facultative or strict anaerobes. Streptococci give a negative catalase test, while staphylococci are catalase-positive.

To identify S. pyogenes in clinical samples, blood agar plates are screened for the presence of β-hemolytic colonies. The typical appearance of S. pyogenes colonies after 24 hours of incubation at 35-37°C is dome-shaped with a smooth or moist surface and clear margins.

To prevent strep infection:

1. Clean your hands. Proper hand cleaning is the best way to prevent all kinds of infections. ...
2. Cover your mouth. Teach your children to cover their mouths when they cough or sneeze.
3. Don't share personal items. Don't share drinking glasses or eating utensils.

Penicillin or amoxicillin is the antibiotic of choice to treat group A strep pharyngitis. There has never been a report of a clinical isolate of group A strep that is resistant to penicillin. However, resistance to azithromycin and clarithromycin is common in some communities.

S. pyogenes (group A β-hemolytic streptococcus) can be found in the oropharynx of more than 20% of children and a smaller percentage of adults. Carriage rates increase greatly during epidemics and in crowded conditions.