STREPTOCOCCUS PYOGENES

• Streptococcus pyogenes is a species of Gram-positive bacteria, it is gram positive cocci.

• streptococci is typically found in chains or pairs.

• It is an important cause of bacterial infections worldwide

Morphology

· Gram-positive bacteria

· Shape: spherical or oval

· Size: About 0.5 to 1.0 µm in diameter.

· Arrangement: Arrange in chain.

· Capsule: Some strains of possess capsule.

· Motility: Non-motile

· Spore: Non-sporing

Pathogenesis

• Streptococcus pyogenes produce pyogenic infection that spread locally along with lymphatic & blood stream.

Ø Source of infection – Contaminated food, lesion, infected blood or body fluid such as saliva, wound, or nasal secretions, etc.

Ø Mode of transmission – transmitted by direct or indirect content, ingestion & inhalation.

Ø Route of transmission – respiratory tract, GI tract, etc.

Ø Incubation period – about 3 to days.

A. SUPPRATIVE INFECTION:

1) RESPIRATORY INFECTION –

• Sore throat (acute tonsillitis and/or pharyngitis) is the most common streptococcal diseases.

• Tonsillitis is more common in older children and adults.

2) Skin & soft tissue infection –

• Strep. Pyogenes causes subcutaneous infection of skin lymphangitis & cellulitis.

• It include wound & burn.

• It may lead to fetal septicemia.

• Strep. Pyogenes is also known as ‘FLASH EATING BACTERIA’.

• Bacterial infection such as Erysipelas & impetigo.

3) Streptococcal toxic shock syndrome –

• TSS is a condition in which the entire organ system is collapse, leading to death.

4) Genital infection –

• Aerobic & Anerobic streptococci are normal inhabitant of female genital tract.

• Important causative agent of puerperal sepsis.

5) Other supprative infection

• Strep. Pyogenes may cause abscess in internal organ such as brain, lungs, liver & kidney.

B. NON-SUPPRATIVE INFECTION:

Lab diagnosis

Ø Specimen:

• Throat swab

• Wound swab

• Pus

• CSF

• Blood

Ø collection & transport:

• Specimen should be collected on sterile container.

• Pike’s medium is used for transport

Ø Microscopy:

• Gram staining - Gram positive bacteria seen in chain formation.

Ø Culture:

• Best grow in blood agar at 37®C for 24-48 hours in presence of 5 – 10% CO2.

Ø Colony morphology:

• Colony of strep. Pyogenes are-

Shape – round

Size- 0.5-1mm

Surface – smooth

Color – grey

Opacity – translucent

Ø Biochemical reaction:

• Camp test – negative

• Catalase – negative

• PYR test – positive

Ø Serological test:

• Anti streptolysin o (ASO) is most widely used

Ø Antigen detection test:

• ELISA

• Agglutination test

Ø Molecular method:

• Polymerase chain reaction

Ø Antibiotic susceptibility testing:

• Oral penicillin V or amoxicillin

Prevention

• Good hygiene practices such as handwashing and covering the mouth and nose when coughing or sneezing.

• Avoiding close contact with infected person.

• Proper wound care and management to prevent skin infections.