streptococcal serology terry kotrla. introduction gram-positive beta hemolytic spherical, ovoid or...
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Streptococcal Serology
Terry Kotrla
Introduction
• Gram-positive• Beta hemolytic• Spherical, ovoid
or lancet shaped• Pairs or chains
Divided into Serotypes or groups
• Two major outer proteins M and T• Eighteen interior proteins knows as
Lancefield grouping• Streptococcus pyogenes belong to
Lancefield group A• M protein chief virulent factor
Numerous Exoantigens
• Exoantigens are produced and excreted and include:– Streptolysin O– Dnase– Hyaluronidase– Nicotinamide Adenine Dinucleotidase – Streptokinase
• Patients react to exoantigens by producing antibodies
Characteristics
• Two major sites of infection– Upper respiratory tract– Skin
• If infections left untreated can lead to post-streptococcal sequelae– Acute glomerulonephritis– Rheumatic fever
Upper Respiratory
• Sore Throat • Tonsillar exudate• Fever• Chills• 20% school
children carriers
Skin
• Impetigo– Lesions on
extremities– Commonly on face– Pustular and
crusty
Suppurative Complications
• Suppurate -To generate pus; as, a boil or abscess suppurates.
• Erysipelas• Necrotizing fasciitis• Scarlet fever
Erysipelas– Infection involves the dermis and lymphatics
and is a more superficial subcutaneous infection of the skin than cellulitis.
– characterized by intense erythema, induration and a sharply demarcated border.
Necrotizing Fasciitis
Scarlet Fever
• Strep bacteria produces a toxin that causes a rash
• Sandpapery• Peels
Non-Suppurative
• Inflammatory response elsewhere in the body.
• Damaging sequelae to strep infection– Rheumatic Fever– Post-Streptococcal glomerulonephritis
Rheumatic Fever• Delayed consequence of an untreated
upper respiratory infection with group A streptococci
• Causes serious, debilitating damage to the heart.
• Associated with large amount of M protein and a capsule
• Due to immune response against Strep antigens similar to heart antigens.
Rheumatic Fever
This is the heart of a 44 year old woman who had rheumatic fever and had been treated for congestive heart failure for about one year.
Poststreptococcal glomerulonephritis
• Follows strep infection of skin or pharynx
• Characterized by damage to glomeruli of kidneys
• Deposition of Ag-Ab complexes, activation of complement.
• Inflammatory response causes damage.
Poststreptococcal glomerulonephritis
• Most common in children 2-12• Symptoms:
– Hematuria– Proteinuria– Edema– hypertension
Poststreptococcal glomerulonephritis• The scattered capillary wall granular
deposits in acute poststreptococcal glomerulonephritis also stain for complement (immunofluorescence with antibody to C3)
Laboratory Testing
• Culture and identification• Rapid Strep Tests from throat swab• Detection of Streptococcal
antibodies• Anti-Streptolysin O (ASO) titer