Group A Beta Hemolytic Streptococcus

, the hemolytic beta certainly plays a prestigious role in terms of pathogenicity and virulence. Before proceeding with the precise discussion of this bacterium, let's take a step back, briefly recalling how streptococci are classified.

The classification of streptococcal bacteria is based on two important criteria:

1. Haemolytic capacity → alpha / beta / gamma hemolytic streptococci
2. Antigenic structure as a function of the cell wall polysaccharide C antigen: Lancefield classification → identification of streptococci distinct from the letters of the alphabet, from A to V (except for the letters J and I)

Due to its extraordinary importance in the field of medicine, an entire article is dedicated to the beta hemolytic streptococcus: in this discussion, the attention will be focused exclusively on a serum group of streptococcus, the beta hemolytic group A.
Group B beta hemolytic streptococcus will be analyzed in the next discussion.

of the upper airways, in particular along the adenoid, tonsillar and nasopharyngeal tissue. The S. pyogenes it assumes a certain pathogenicity when the normal defense mechanisms of the host are compromised, therefore the bacterium creates damage.
Mediator of a series of inflammatory manifestations, lo S. pyogenes it can trigger acute reactions such as necrotizing fasciitis, acute rheumatic fever, acute glomerulus nephritis, primary throat infections and scarlet fever. The pathogen, when it spreads in the different parts of the organism, can induce severe septicemia.
1-3 weeks after the first acute episode, the patient infected with group A beta hemolytic streptococcus is very likely to complain of so-called "non-suppurative" lesions.

To understand...

Non-suppurative sores: lesions only indirectly related to the acute inflammatory reaction sustained by the pathogen. From the histological point of view, these lesions lack all those signs attributable to a lively phlogistic response; the local alterations can be surrounded by haemorrhage, exudation, hyperemia and tissue nercrosis.

infected; simply through sneezing, coughing or talking, the pathogen can be transmitted from a sick person to a healthy person.
It is estimated that S. pyogenes is the second cause of streptococcal infection after pneumococcus.

Damage mediated by group A beta hemolytic streptococcus Possible complications Streptococcal angina + exanthema (scarlet fever) Peritonsillar abscess, ulcerative endocarditis, mastoiditis, meningitis, otitis media, pneumonia Bacteremia Localization of beta-hemolytic streptococcus in the heart → acute ulcerative endocarditis Nodular edema (non-suppurative lesion) - Puerperal fever Postpartum infections of the endometrium (currently gone) Acute rheumatic fever * (non-suppurative damage) Rheumatic heart disease Streptococcal glomerulonephritis (non-suppurative lesion) - Inflammation and necrosis of the subcutaneous tissues Necrotizing fasciitis and toxic shock ** Skin infections: erysipelas, impetigo, other pyoderma Bacteremia and metastic suppurative complications

* Rheumatic fever is a disease that affects the joints, kidneys and heart valves, a consequence of a "streptococcal infection NOT carefully treated. Paradoxically, this disease is not caused directly by the bacterium, rather by the antibodies developed by the immune system to fight the infection. cross reactivity between the components of the M protein of the bacterium and the self-antigens located in the sarcolemmatic membrane (membrane of striated muscle tissue fibers) → tissue damage is induced by a series of autoimmune mechanisms.

** Some complications are direct expression of the production of toxins called "erythrogenic", produced exclusively by group A Streptococci. These toxins, encoded by particular bacteriophages or plasmids, act as superantigens and create damage. The toxins synthesized from S. pyogenes for example, they can trigger toxic shock.

, while the culture analysis involves sowing on blood agar.

Streptococcus is searched for in samples taken from pharyngeal exudate or from the skin; to be isolated, the pathogen is seeded in blood agar plates. During the analysis, it is also possible to evaluate the sensitivity of the pathogen to bacitracin: S. pyogenes it is in fact more sensitive to this substance than other streptococci.

For a better detection of streptococcal infection, it is possible to search for antistreptolysin antibodies: in fact, all pyogenic streptococci synthesize this toxin.

, especially penicillins. If the patient is allergic, a therapy with erythromycin and cephalosporin is recommended, to be continued for at least 10 days, in order to avoid the late onset of non-suppurative lesions. Sulfonamides can also be used in therapy for the treatment of infections S. pyogenes. On the other hand, tetracyclines are not indicated, as streptococci can also develop resistance against these antibiotics.
When beta hemolytic streptococcus infects the skin, drainage and thorough wound hygiene are required.
Currently, there are no vaccines that ensure immunity from infections caused by beta haemolytic streptococci. The formulation of such a vaccine is hampered by the high number of serotypes identified, by the possible immunological cross-reactions with human tissues and by the difficulties of isolation of streptococcus. beta hemolytic.

Other articles on "Group A Beta Hemolytic Streptococcus - S. pyogenes"

1. Streptococcus - Streptococci
2. Group B Beta Hemolytic Streptococcus