Bacterial skin infections


I- Introduction :

  • The majority of bacterial skin infections due to Gram cocci + : strep A, Staphylococcus aureus. These infections are self-inoculable not immunizing.
  • They are favored by local factors (wounds, Pre-existing skin diseases, skin maceration…).
  • Staphylococcus infections often testify d & rsquo; a chronic staff porting and / or the & rsquo; family environment.
  • The diagnosis of these common skin infection is mainly clinical.
  • Complications are rare but potentially serious, justifying the usual recourse to general antibiotic therapy.
  • Preventing recurrence is based on :

–     Treatment of d & rsquo doors entry (intertrigo dermatophyte in & rsquo; erysipelas ..) ;

–     Detection and decontamination of houses in case of boils.

II- mechanisms from control from l’infection from the skin :




Integrity of the stratum corneum renewal of the stratum corneum




Skin acidity

lipid inhibitor (free fatty acids, sphingolipides) antibiotic peptides secreted by keratinocytes




humoral immunity cellular immunity


Competition between the Microorganisms


substances secreted by microorganisms :

- Enzymes bacteriolytic

- Lipolysis of surface lipids of free fatty acids - Antibiotic, antifungal and bacteriocin

"Occupation" field


III- factors encouraging l’infection cutaneous :

  • factors local :

- Overcrowding and poor hygiene

- maceration

- Alteration of the skin

- Local Corticosteroid

  • factors general :

- Congenital immunodeficiency or acquired

- unbalanced Diabetes

- Systemic corticosteroids

- immunosuppressive

  • Finally, l & rsquo; weakening of the defenses from l & rsquo; host.

IV- impetigo :

A- Etiology :

  • L & rsquo; Impetigo is a superficial skin infection (in the horny layer of the & rsquo; epidermis) streptococcal beta-hemolytic group A and / or Staphylococcus aureus.
  • Autoinoculable not immunizing,
  • Achieved especially the & rsquo; child.
  • Contagious with small family epidemics or school communities àéviction.
  • At the & rsquo; adult impetigo almost always reflects preexisting skin lesions.

B- Diagnostic :

  • Form usual from l & rsquo; child :
  • The elementary lesion is a superficial bubble, sub-stratum. Very fragile àrarement view
  • Evolving rapidly towards an erosion covered with yellowish scabs ("Mélicériques" c & rsquo; is to say, honey-colored) centrifugal extension.
  • Beginning often périorificiel, àdiffusent on the face and limbs superiors.
  • No general signs (in particular no fever).
  • impetigo bullous :

C & rsquo; is the characteristic shape of newborn, especially staph.

  • THE : The bubbles sometimes large
  • Complication : Syndrome & rsquo; staphylococcal epidermolysis (or staphylococcal scalded skin for SSSS syndrome) : Erythema diffuse and superficial epidermal peeling starts around & rsquo; sometimes a small focus of infection (nasal,  umbilical or perineal)  and s & rsquo; expanding rapidly in a feverish table may be complicated by dehydration. The sign is positive Nikolski. This is due to cleavage induced by staphylococcal exfoliative toxin (exfoliatine)
  • Diagnostic differenciel : toxic epidermal necrolysis
  • Ecthyma :

C & rsquo; is a burrowing form & rsquo; impetigo usually located in the lower limbs.

  • impetiginisation :

It s & rsquo; is the & rsquo; emergence of dermatosis (most SVT itchy) pustules or crusts mélicériques.

C- positive diagnosis :

The East clinique.

  • Bactériologie: is not useful in clinical practice. The germs involved are either streptococci, or Staphylococcus aureus, or the combination of two.
  • histology, rarely necessary, -> pustule souscornée.

D- Evolution :

  • It is rapidly favorable.
  • Very rarely impetigo may be the door & rsquo; d & rsquo entry; severe generalized infection streptococcus or staphylococcus.
  • The exceptional risk-streptococcal glomerulonephritis post justified the search & rsquo; proteinuria 3 weeks after & rsquo; infectious episode.

E- Treatment :

  • Local treatment may be sufficient in some extended forms :

– antiseptics (chlorhexidine…) ;

– topical antibiotics (fusidic acid…).

  • General antibiotic treatment is usually prescribed.
  • Indication :
  • many lesions (> 5) and / or more territories,
  • Failed local TRT,
  • aggravating factors (immune deficiency in particular). cloxacillin, amoxicillin + clavulanic acid, céphalixine, Pristinamycine, fusidic acid.
  • Additional measures :

– Eviction of school days ;

– Treatment of siblings ;

V- Boil :

A- Etiology :

  • C & rsquo; is a deep infection of the follicle pilosebaceous by staphylococcus aureus.
  • It is favored by the manual porting from staphylococcal houses.

B- Diagnostic :

  • Boil :

–     The beginning is a simple folliculitis, then

–     Rapidement appears

  • an indurated area, rouge, hot, centered by a pustule,
  • The sometimes intense pain,
  • +/- lymphadenopathy and +/- fever,

–     In A few days, bourbillon the s & rsquo; eliminated aune scar þess.

–     Seat : stt dos, shoulders, thighs or buttocks (role of friction).

–     Irritation or handling àrisque boil dissemination of & rsquo; infection.

  • Anthrax

C & rsquo; is a cluster of boils, performing an inflammatory hyperalgesic closet dotted pustules. His office is elective neck or upper back.

  • Furonculose :

C & rsquo; is the repetition of & rsquo; episodes of boils, with chronicity over periods of several months.

It must find a contributory factor and a (of the) foyer(s) staphylococcique(s) :

–     Narinaire +++,

–     postauricular,

–     Interfessier,

–     Scars & rsquo; former boils.

C- Diagnostic positive :

  • He is before all clinical.
  • Search Staph in shelters in case of boils.

D- Diagnostic differential :

  • Folliculites superficial :

Papulo- pustules centered by a hair (taking the name of sycosis for the & rsquo; achieving beard).

It s & rsquo; is usually d & rsquo; Staphylococcus aureus infection but d & rsquo; other agencies may be involved (yeast especially).

  • hidrosadénite suppurative :

inflammatory skin disease follicular,   recurrent debilitating and that usually occurs after puberty with painful and inflammatory lesions deeply located in the body zones carrier apocrine glands, most often axillary regions, inguinal and anogenital.

  • Acne :

Confusion is common, although the & rsquo; acne is characterized by boils his lesional polymorphism (comedones, cysts, papulo-pustules).

E- Evolution :

The chronicity (or chronic furunculosis) is the most common complication. Sepsis and other complications visceral Staphylococcus aureus are very rare.

The malignant staphylococcal infection of the face with thrombophlebitis of the cavernous sinus is exceptional. It is feared in the presence of & rsquo; a boil central facial handled becoming hyperalgesia with marked infectious syndrome and an important central facial edema.

F- Treatment :

  • Boil isolated :

–   1thrust era non-severe, simple treatment :

+ Hygiene,

+ Do not handle the lesions,

+local antiseptic.

–   injury centrofacial, extension of the lesion and / or the occurrence of fièvreàAntibiothérapie

oral (oral penicillin M, pristinamycine, fusidic acid).

  • Furonculose :

– strict hygiene ;

– Antibiotic po ;

– Local treatment by prolonged houses antiseptics or antibiotics ; – Collection and processing of deposits for the whole family.

WE- erysipelas :

A- Definition :

acute dermo-bacterial hypodermitis most svt streptococcal β-hemolytic A

B- Epidemiology :

- Location leg in + from 80% cases

- Frequent and the first dgc to raise with a big red leg acute, febrile

- Average age of onset to 60 years.

C- Contributing factors :

– IVC et (or) lymphatic.

- Lymphedema,

- Front door intertrigo inter-toes, leg ulcer

- General (obesity).

D- Clinique :

usual "fat acute febrile red leg" unilateral Table

  • Onset is sudden
  • SG: high fever (39at 40 ˚C) + chills,
  • Built inflammatory skin :

- erythematosus,

- oedematous,

- Circumscribed, A peripheral bead is rarely observed

- Painful to palpation.

– +/- superficial bullous detachment or purpura,

  • Of ipsilateral inflammatory ADP are frequently associated.
  • A trail of ipsilateral lymphangitis is present in a quarter of cases.

E- A gateway :

- clinically detectable in 2/3 cases.

- Minimum: intertrigo inter-toes, sting, traumatic erosion

- evident (leg ulcer).

F- No exam complementary is necessary.

- Leukocytosis PNN is usual

- The inflammatory syndrome is important (CRP often > 100 mg / L).

- Blood cultures are of low profitability ;

G- The evolution :

- Favorable in 8 at 10 days within antibiotics.

- The apyrexia in 48 at 72 hours ;

- Local signs in a week.

H- The less typical tables :

1- Erysipèle atypical :

  • Of subacute, where fever and leukocytosis are moderate, or absent. Dgc mentioned before:

- The clinical features of cutaneous inflammatory closet

- Regression in streptococcal antibiotics.

2- Erysipèle in the diabetic :

  • classic shape, or
  • Dermo-hypodermite subaiguë, in Torp, foot and leg lower third :

–     skin inflammation appears deeper,

–     Built less limited,

–     moderate pain,

–     sometimes absent fever.

  • The door & rsquo; entry is often a sore plantar perforating.
  • The causative : Staphylococcus aureus, Pseudomonas aeruginosa, anaerobic.
  • systematic review : osteitis underlying / decompensation of diabetes.
  • Evolution is less favorable
  • If a poor response to antimicrobial therapy to surgery.

3- Dermohypodermites infectious of the immunosuppressed :

The clinical presentation is often misleading (few inflammatory signs) AFrom- estimated the severity and in particular the possibility of deep necrosis.

4- Other dermohypodermites acute bacterial :

  • A pasteurellosis animal àmorsure (chat, dog) ;
  • The swine erysipelas : erythematous edematous wound periphery, extremely painful after an injury pork bones, mutton, of fish or crustaceans edges.

I- Treatment :

  • And hospitalization : Penicillin G IV until at least apyrexia then orally relay (penicillin V, amoxicillin). Total duration : 10 at 20 days.
  • And retention at domicile : misoprostol by mouth hang 15 days about.
  • Pristinamycine (or clindamycine) in case of allergy to beta-lactam.
  • Preventing recurrence :

–     Treatment of a door

–     Support contributing factors

VII- Dermohypodermites necrotizing :

“fasciite necrotizing”, from gangrene gas, from dermo-hypodermite necrotizing,

  • Signs of sepsis:

–     Fever > 39° c or hypothermia

–     TIME / collapsed

  • local signs:

–     dr +++ or hypoesthesia

–     Induration diffuse

–     Cyanose / necrosis

–     crepitus

  • The germs: streptococcus, Staphylococcus aureus, Gram-negative bacilli, anaerobic.
  • surgical emergency.