Common Bacterial Skin Infections

We all have bacteria which live normally on the surface of our skin and they are called the normal commensal flora. These commensal bacteria in ordinary circumstances do not cause us any problems and in some cases help to maintain the proper functioning of the skin.

Bacteria found in this normal flora include:

  • Staphylococcus               
  • Micrococcus                    
  • Corynebacterium         
  • Brevibacterium              
  • Propionibacterium       
  • Acinetobacter                

 The presence, quantity and combinations of these normal bacteria on the body vary with the specific area. Slightly different groupings of organisms exist in different areas.

Some persons may carry bacteria which are not classified as normal commensals and which are known to be significant in causing skin infections , as a part of their own normal flora. This phenomenon is known as bacterial carriage.

Thirty-five percent of persons may carry Staphylococcus aureus in their nostrils. This bacterium is a major cause of common bacterial skin infections. Other significant sites of Staphylococcal carriage include the hand and the perineum.  A significant number of persons may carry Streptococcus pyogenes in the nostrils, which also causes skin infections.

 A change in the skin, such as a break in the skin surface ( which allows the bacteria to enter the skin), or excessive heat and moisture (which may allow the bacteria to exist in unusually large numbers), may promote the development of infections. Persons who have skin conditions such as Atopic eczema are at significant risk of developing bacterial skin infections especially Staphylococcal infections.

Bacterial skin infections may have different patterns on the skin:

PATTERNS OF PRESENTATION SEEN IN BOTH STAPHYLOCOCCAL AND STREPTOCOCCAL SKIN INFECTIONS

DIRECT SKIN INFECTIONS

IMPETIGO: A contagious superficial bacterial skin infection. Two patterns are seen:

  • Bullous, which appear as small thin walled pus filled vescicles.
  • Non-Bullous, which may appear as moist eroded areas, or more dry scaly areas.

TREATMENT OF IMPETIGO
In mild cases, you doctor may recommend the use of local antiseptics to wash the area, such as povidone iodine or Chlorhexidine. The affected area is treated with topical antibiotics such as Mupirocin. Treatment of the environment to remove bacterial contamination is important. Contacts (ie. persons in close contact with the patient will also be asked to use the antiseptics). Treatment of the nostrils with topical antibiotics is done to interrupt nasal carriage. Good hygiene practices and hand washing are crucial in containing the infection and in preventing the spread. Where a patient presents with frequent infections, the doctor may check for a predisposing condition such as diabetes or anaemia. Family members may be checked for bacterial nasal carriage. Testing with a sterile swab is often done to properly identify the bacteria and to ensure that the antibiotics used are effective against the bacteria.

When the impetigo is widespread or severe the doctor will use oral antibiotics in addition to the other measures mentioned above. Healing of impetigo usually occurs without scarring. In pigmented persons there may be changes in the colour of the skin. These colour changes usually resolve after some time.

ECTHYMA: A bacterial infection of the skin characterized by the formation of adherent crusts, beneath which ulceration occurs. The buttocks legs and thighs are the areas most commonly affected. In our Caribbean setting one of the common causes for the development of ecthyma  (particularly in children ) is the allergic response to the bites of insects. This response is called papular urticaria.

TREATMENT OF ECTHYMA
Treatment of ecthyma involves the use of antiseptics and topical antibiotics as is done for impetigo. Oral antibiotics are used, which are known to be able to cover both Staphylococcus and Streptococcus.

Ecthyma lesions tend to heal with scarring. The colour and the texture of the skin in some cases may never return to its original state.

FOLLICULITIS: A bacterial infection which is confined to the very superficial area of the hair follicle. It is confined to or extends just below the ostium. Folliculitis lesions heal without scarring.

There are cases in which folliculitis may not be caused by bacteria. Your doctor will enquire about exposure to oils or chemical irritants or certain types of skin trauma, as these may cause your skin to have the appearance of a bacterial folliculitis.

TREATMENT OF FOLLICULITIS
Mild cases of folliculitis need only cleansing with topical antiseptics. Severe cases need topical and or systemic antibiotics. Hand washing is the most important behavioural modification. Good personal hygiene is equally important.

FURUNCLE/BOIL:  An acute usually necrotic infection of a hair follicle with Staphylococcus aureus

A furuncle/boil usually starts as a red firm painful nodule which then becomes soft and boggy. A furuncle often eventually bursts and discharges pus. Furuncles may have associated symptoms such as fever.

TREATMENT OF FURUNCLES/BOILS
Treatment requires the use of oral antibiotics.  The course of antibiotics which has been prescribed should be completed, as there is a growing trend for bacteria to develop resistance to antibiotics. The doctor may perform a minor procedure to open the lesion. This procedure will allow the pus to drain from the lesion. Measures for the reduction of bacterial spread and contamination mentioned before should be observed.

CARBUNCLE : A deep infection of a group of contiguous follicles and underlying connective tissue extending to the subcutaneous fat.

A carbuncle involves more extensive spread of the infection to the deepest layers of the skin. This extensive area of infection may be accompanied by symptoms which include fever and a general feeling of being unwell. These lesions may take some time to heal, and cause scarring.

TREATMENT OF CARBUNCLES
As is the case with boils, oral antibiotics are used in the treatment of carbuncles and the entire course must be taken. The doctor may perform the same procedure as mentioned above to allow the pus to drain. All measures for the prevention of spread must be taken.

In all cases of infections good hygienic practices are essential to the prevention of spread and of recurrence.

Your doctor will in most instances ask that your close contacts also engage in some of the meaures that you are performing.

These may include:

  • Bathing with antiseptic solutions
  • Treating their nostrils with topical antibiotics
  • Having swabs done to assess whether they are also carrying, (without a visible infection) the same  bacteria which are causing your visible infection

 Good personal and environmental hygiene are critical in preventing bacterial skin infections

Hand washing is a simple and effective way to reduce bacterial skin infections.

 REFERENCES

ROOK’S TEXTBOOK OF DERMATOLOGY  eighth edition

Marie Grandison-Didier
Dermatologist