Lower Extremity Cellulitis: Look Between the Toes

ABSTRACT & COMMENTARY

Synopsis: Ipsilateral athlete’s foot was present in 83% of episodes of lower extremity cellulitis, and b-hemolytic streptococci and S. aureus were commonly isolated from the interdigital web space.

Source: Semel JD, Goldin H. Clin Infect Dis 1996;23:1162-64.

Semel and goldin in chicago evaluated the bacterial flora of the interdigital web space of the ipsilateral foot in patients with lower extremity cellulitis. Patients with a history of trauma, peripheral vascular disease, or chronic open ulcers were excluded, leaving 24 episodes in 22 patients. Athlete’s foot, defined as the presence of interdigital cracking, scaling, fissuring, or maceration, was present during 20 (83%) of the episodes. Thirteen (59%) of the patients with athlete’s foot reported at least one prior episode of cellulitis; only three patients had previously undergone coronary artery bypass grafting. Interdigital cultures, obtained by swab, yielded Gram-positive organisms (coagulase-negative staphylococci and Corynebacterium species were not considered relevant) in all 20 of the episodes associated with the presence of athlete’s foot. These included b-hemolytic streptococci in 17, including Streptococcus pyogenes in four, S. agalactiae in three, group C streptococci in one, and group G in nine. Staphylococcus aureus was isolated during nine (45%) episodes. While Gram-negative bacilli were isolated in seven (35%) episodes, they were always recovered together with either a b-hemolytic streptococcus or S. aureus. Cultures obtained from 30 control patients with athlete’s foot without cellulitis failed to yield b-hemolytic streptococci in any, although the frequency of isolation of S. aureus and Gram-negative bacilli was similar to that in the patient group.

COMMENT BY STAN DERESINSKI, MD, FACP

In 1984, Baddour and Bisno described an association between recurrent lower extremity cellulitis in patients who had undergone autologous saphenous vein coronary artery bypass grafting and the presence of athlete’s foot, all in the ipsilateral extremity.1 Further recurrences appeared to be prevented by treatment of the foot infection.

Athlete’s foot is not invariably associated with the presence of dermatophytes. In fact, while hyphae may be found readily in most mild cases with scaling only, they are often absent when maceration is present, a time when large numbers of bacteria are present. It appears that athlete’s foot involves both dermatophytes and bacteria with one or the other predominating depending upon the stage of disease.

This study is consistent with the notion that lower extremity cellulitis, in the absence of other obvious predisposing factors, is the result of invasion of bacteria through areas of damaged skin heavily colonized or infected with bacteria, predominantly b-hemolytic streptococci but with some S. aureus.

The precise etiologic diagnosis of cellulitis is often problematic in the absence of positive blood cultures. Aspiration of the leading edge of cellulitic lesions is most often unrewarding. This study suggests that culture of the interdigital web space of the ipsilateral foot in individuals with athlete’s foot and cellulitis may provide some assistance, but the data presented here do not allow us to make this link unequivocally. Performance of an ASO titer may be of value—it was elevated in 10 of 16 episodes in this study in which b-hemolytic streptococci were recovered from the web space.

This study reinforces the need to carefully examine the feet of patients with lower extremity cellulitis, particularly those with recurrent infection, and to treat any athlete’s foot that is present. More importantly, it indicates the need for routine examination of patients’ feet, especially those with lower extremity venous or lymphatic compromise, by primary care physicians, in order to prevent the recurrence of lower extremity cellulitis. (Dr. Deresinski is Clinical Professor of Medicine, Stanford University.)

Reference

1. Baddour LM, Bisno AL. JAMA 1984;251:1049-1052.