Microbiology of secondary bacterial infection in scabies lesions

Aerobic and anaerobic bacteria were grown from specimens obtained from 30 children with secondarily infected scabies lesions. Aerobic or facultative bacteria only were present in 14 (47%) patients, anaerobic bacteria only were present in 6 (20%) patients, and a mixed anaerobic-aerobic flora was present in 10 (33%) patients. Fifty isolates were recovered (1.7 per specimen); 27 were aerobic or facultative bacteria and 23 were strict anaerobes. The predominant aerobic and facultative bacteria were Staphylococcus aureus (nine isolates), group A streptococci (five isolates), and Pseudomonas aeruginosa (three isolates). The predominant anaerobes were Peptostreptococcus sp. (nine isolates) and pigmented Prevotella and Porphyromonas spp. (four isolates). Single bacterial isolates were recovered from nine (30%) patients; five of these were S. aureus. Sixteen organisms isolated from 12 (40%) patients produced the enzyme beta-lactamase. Organisms that resided in the mucous membranes close to or in contact with the lesions predominated in those infections. Enteric gram-negative rods were recovered in leg and trunk lesions. Group A streptococci and S. aureus predominated in finger and hand lesions. Bacteroides fragilis group and Clostridium sp. were isolated from leg lesions, and pigmented Prevotella sp. and Porphyromonas and Fusobacterium spp. were recovered from finger lesions. The polymicrobial etiology of secondarily infected scabies lesions in children and the association of bacterial flora with the anatomical sites of the lesions are demonstrated.