STREPTOCOCCAL SKIN INFECTIONS :
■INTRODUCTION
●Streptococci are gram (+) bacteria.
●They are highly pathogenic because they have a variety of mechanisms to escape immune defenses of our body . They secrete toxins , enzymes, and virulence factors.
●one of their toxins is HEMOLYSIN , which lyse RBC and almost any type of cell too;
and depending on the hemolysin they produce; streptococci are of 3 types :
1) Alpha-hemolytic
2)Beta-hemolytic
3)Gamma-hemolytic ( it is actually non-hemolytic )
Amon them, beta-hemolytic is often associated with human diseases.
Depending upon the antigenic carbohydrates present on their cell wall ; they have been categorized in to different serological groups from A to T.
The group A streptococci known as GAS are the most important of beta-hemolytic streptococci and are further divided in to 80 immunological types based on the antigenic properties of M proteins present on the cell wall.
■Following properties of GAS makes them pathogenic :
●the M protein prevents activation of complement system and help the microbe to evade phagocytosis.
It also helps the bacteria to adhere to mucous membrane and colonize it.
●Another factor making them virulence is their capsule made up of hyaluronic acid. Actually, hyaluronic acid is poorly immunogenic and few antibodies are made against it.this helps the microbe in better adaptation to the host.
● Besides, GAS also produce substances which helps them in rapid spread of infections through tissue and by liquifying pus.
e.g. STREPTOKINASES-enzymes that dissolves blood clots.
HYALURONIDASE-it dissolves the hyaluronic acid in the connective tissue and helps to
cement together.
DEOXYRIBONUCLEASE- enzymes that degrade DNA.
STREPTOLYSINS- they lyse RBC and are toxic to neutrophiles.
The GROUP A STREPTOCOCCI are synonymous with the species of STREPTOCOCCUS. PYOGENS. some infections caused by S.PYOGENS are as below :
■ERYSIPELAS- it is an infection of the dermal layers of skin. Symptoms are pupules and fever.pupules first occur on the face and then lead to sore throat. It can lead to local tissue destruction and even enter blood stream causing sepsis. It can be treated by beta-lactam antibiotics.
■IMPETIGO- common in childrens and toddlers, symptoms include pustules that become crusted and rupture. This disease is spread by contact and bacteria penetrate the skin thtough cuts and abrasions already present.
■STREPTOCOCCAL TOXIC SHOCK SYNDROME - in case of this TSS bacteremia is more likely to occur than rash. M proteins shade from surfaces of these bacteria forms complex with fibrinogen and binds to neutrophiles. This causes activation of neutrophiles, precipitating the release of damaging enzymes and consequent shock and organ damage.
PSEUDOMONADAL INFECTIONS OF SKIN-:
■pseudomonads are aerobic ,gram (-) bacteria which are capable of growing on unusual organic matter like soap films, and cap liner adhesives.
●the most prominent species is PSEUDOMONAS AERUGINOSA; which is an oppurtunistic pathogen; and causes following types of infections :
1) PSEUDOMONAS DERMATITIS - it is a self-limiting rash of 2 weeks duration and is associated with swimming pools and pool like saunas and hot tubs.
When many people use these facilities; the alkalinity rises and the chlorines become less effective; at the same time, nutritive value of pool to support the growth of microbes increases and P.AERUGINOSA starts flourishing.
Hot water causes hair follicles to open wider and bacteria easily enters inside causing infection.
2)OTITIS EXTERNA ( swimmer 's ear)- it is common among professional swimmers in which the external ear that leads to the eardrum gets infected.
3) IN BURN PATIENTS -P.AERUGINOSA is a serious oppurtunistic pathogen in burn patients and cause blue-green pus on infection; the blue-green colour is due to bacterial pigment PROCYANIN.
■TREATMENTS:
●pseudomonads are resistant to many antibiotics and disinfectants.
But, in recent years, many antibiotics and chemotherapy has been developed. The quinolones and antipseudomonal beta-lactam antibiotics are the drugs of choice.
● silver sulfaduazine is used to treat burn infections by P.AERUGINOSA.
■INTRODUCTION
●Streptococci are gram (+) bacteria.
●They are highly pathogenic because they have a variety of mechanisms to escape immune defenses of our body . They secrete toxins , enzymes, and virulence factors.
●one of their toxins is HEMOLYSIN , which lyse RBC and almost any type of cell too;
and depending on the hemolysin they produce; streptococci are of 3 types :
1) Alpha-hemolytic
2)Beta-hemolytic
3)Gamma-hemolytic ( it is actually non-hemolytic )
Amon them, beta-hemolytic is often associated with human diseases.
Depending upon the antigenic carbohydrates present on their cell wall ; they have been categorized in to different serological groups from A to T.
The group A streptococci known as GAS are the most important of beta-hemolytic streptococci and are further divided in to 80 immunological types based on the antigenic properties of M proteins present on the cell wall.
■Following properties of GAS makes them pathogenic :
●the M protein prevents activation of complement system and help the microbe to evade phagocytosis.
It also helps the bacteria to adhere to mucous membrane and colonize it.
●Another factor making them virulence is their capsule made up of hyaluronic acid. Actually, hyaluronic acid is poorly immunogenic and few antibodies are made against it.this helps the microbe in better adaptation to the host.
● Besides, GAS also produce substances which helps them in rapid spread of infections through tissue and by liquifying pus.
e.g. STREPTOKINASES-enzymes that dissolves blood clots.
HYALURONIDASE-it dissolves the hyaluronic acid in the connective tissue and helps to
cement together.
DEOXYRIBONUCLEASE- enzymes that degrade DNA.
STREPTOLYSINS- they lyse RBC and are toxic to neutrophiles.
The GROUP A STREPTOCOCCI are synonymous with the species of STREPTOCOCCUS. PYOGENS. some infections caused by S.PYOGENS are as below :
■ERYSIPELAS- it is an infection of the dermal layers of skin. Symptoms are pupules and fever.pupules first occur on the face and then lead to sore throat. It can lead to local tissue destruction and even enter blood stream causing sepsis. It can be treated by beta-lactam antibiotics.
■IMPETIGO- common in childrens and toddlers, symptoms include pustules that become crusted and rupture. This disease is spread by contact and bacteria penetrate the skin thtough cuts and abrasions already present.
■STREPTOCOCCAL TOXIC SHOCK SYNDROME - in case of this TSS bacteremia is more likely to occur than rash. M proteins shade from surfaces of these bacteria forms complex with fibrinogen and binds to neutrophiles. This causes activation of neutrophiles, precipitating the release of damaging enzymes and consequent shock and organ damage.
PSEUDOMONADAL INFECTIONS OF SKIN-:
■pseudomonads are aerobic ,gram (-) bacteria which are capable of growing on unusual organic matter like soap films, and cap liner adhesives.
●the most prominent species is PSEUDOMONAS AERUGINOSA; which is an oppurtunistic pathogen; and causes following types of infections :
1) PSEUDOMONAS DERMATITIS - it is a self-limiting rash of 2 weeks duration and is associated with swimming pools and pool like saunas and hot tubs.
When many people use these facilities; the alkalinity rises and the chlorines become less effective; at the same time, nutritive value of pool to support the growth of microbes increases and P.AERUGINOSA starts flourishing.
Hot water causes hair follicles to open wider and bacteria easily enters inside causing infection.
2)OTITIS EXTERNA ( swimmer 's ear)- it is common among professional swimmers in which the external ear that leads to the eardrum gets infected.
3) IN BURN PATIENTS -P.AERUGINOSA is a serious oppurtunistic pathogen in burn patients and cause blue-green pus on infection; the blue-green colour is due to bacterial pigment PROCYANIN.
■TREATMENTS:
●pseudomonads are resistant to many antibiotics and disinfectants.
But, in recent years, many antibiotics and chemotherapy has been developed. The quinolones and antipseudomonal beta-lactam antibiotics are the drugs of choice.
● silver sulfaduazine is used to treat burn infections by P.AERUGINOSA.
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