Wounds and bacteria: contamination, colonization, and infection

Ulceration of the skin in epidermolysis bullosa (EB) invariably leads to the presence of bacteria, although the extent to which this happens and its clinical implications vary greatly. It is useful to consider bacterial load in a wound as a continuum ( Fig. 1 ). At one end there is contamination, with bacteria over the wound surface, usually as a result of inoculation from hands, fomites, or airborne contamination: in this situation bacteria do not impede healing of the wound and no treatment is necessary. When bacteria are present in greater numbers, but not impairing healing, the wound can be said to be colonized. If bacterial proliferation increases further, the wound may become “stuck,” where it is unable to heal, although not extending in size. At this stage, the term “critical colonization” is used. At the far end of the spectrum, with still greater bioburden, is infection: this is usually considered to occur once there are 10 ⁵ bacteria present per gram of tissue. Wound infection is essentially a clinical diagnosis characterized by increasing size, exudate, odor, and pain, and surrounding erythema, swelling and edema, although these signs may be less marked in chronic EB wounds. Systemic upset and fever may also accompany a wound infection. As with all wounds, EB management relies on recognition of colonization or frank infection, and tailoring treatment accordingly.

The bioburden in a wound is a continuum, and reflects a balance between numbers and virulence of bacteria, and the host defenses. Contamination and colonization can be viewed as normal states, although critical colonization (in which the wound fails to heal) and infection (increased wound size and local signs) are abnormal and require treatment to enable healing to occur.

Colonization and infection in EB

There are no good data concerning the incidence of critical colonization or wound infection in EB but, anecdotally, this is a sizeable problem, particularly for patients with more severe and generalized forms who have large numbers of chronic wounds. These wounds cause considerable morbidity, including pain, exudate and odor, and may demand many hours of dressing changes on a daily basis; they are also responsible for a significant economic burden, necessitating large quantities of often expensive, specialized dressings.

Sepsis, in the majority of cases arising from cutaneous infection, is an important cause of death of EB patients, particularly neonates and infants with junctional and recessive dystrophic EB. The use of intravenous lines and indwelling ports are also a significant source of septicemia in this group due to chronically colonized or infected surrounding or overlying skin. These patients may be particularly susceptible to infections due to anemia, poor nutrition, and relative immunosuppression as a result of their systemic disease.

The most common bacteria isolated from EB wounds include gram-positive organisms, particularly Staphylococcus aureus and Streptococci , as well as gram-negatives and anaerobes such as Pseudomonas aeruginosa and Proteus . It is common to find a mixed growth of organisms in EB wounds, particularly those that are chronic. The emergence of antibiotic-resistant strains of bacteria is a particular problem: methicillin-resistant Staphylococcus aureus and, increasingly, ciprofloxacin-resistant Pseudomonas , are frequently isolated from EB wounds. It may be impossible to eradicate these bacteria fully, and it is possibly unfeasible to aim to do so in EB patients. Rather, efforts should be made to restrict treatment to clinically significant infections, and to limit spread within health care settings and the community as much as possible.

Colonization and infection in EB

There are no good data concerning the incidence of critical colonization or wound infection in EB but, anecdotally, this is a sizeable problem, particularly for patients with more severe and generalized forms who have large numbers of chronic wounds. These wounds cause considerable morbidity, including pain, exudate and odor, and may demand many hours of dressing changes on a daily basis; they are also responsible for a significant economic burden, necessitating large quantities of often expensive, specialized dressings.

Sepsis, in the majority of cases arising from cutaneous infection, is an important cause of death of EB patients, particularly neonates and infants with junctional and recessive dystrophic EB. The use of intravenous lines and indwelling ports are also a significant source of septicemia in this group due to chronically colonized or infected surrounding or overlying skin. These patients may be particularly susceptible to infections due to anemia, poor nutrition, and relative immunosuppression as a result of their systemic disease.

The most common bacteria isolated from EB wounds include gram-positive organisms, particularly Staphylococcus aureus and Streptococci , as well as gram-negatives and anaerobes such as Pseudomonas aeruginosa and Proteus . It is common to find a mixed growth of organisms in EB wounds, particularly those that are chronic. The emergence of antibiotic-resistant strains of bacteria is a particular problem: methicillin-resistant Staphylococcus aureus and, increasingly, ciprofloxacin-resistant Pseudomonas , are frequently isolated from EB wounds. It may be impossible to eradicate these bacteria fully, and it is possibly unfeasible to aim to do so in EB patients. Rather, efforts should be made to restrict treatment to clinically significant infections, and to limit spread within health care settings and the community as much as possible.