Body distribution of impetigo and association with host and pathogen factors

Background: Impetigo or skin sores are estimated to affect >162 million people worldwide. Detailed descriptions of the anatomical location of skin sores are lacking. Methods: We used prospectively collected data from a randomised control trial of treatments for impetigo in Aboriginal children in Australia. We generated heat-map distributions of skin sores on the human body from 56 predefined anatomical locations and stratified skin sore distribution by sex, age, causative pathogen and co-infection with scabies, tinea and head lice. We compared the distribution of sores between males and females, between sores with only Streptococcus pyogenes and sores with only Staphylococcus aureus; and across age groups with a Fisher's exact test. Results: There were 663 episodes of impetigo infections among 508 children enrolled in the trial. For all 663 episodes, the lower limbs were the most affected body sites followed by the distal upper limbs, face and scalp. On the anterior surface of the body, the pre-tibial region was the most affected while on the posterior surface, the dorsum of the hands and calves predominated. There was no observable difference between males and females in distribution of sores. Children up to 3 years of age were more likely to have sores on the upper posterior lower limbs and scalp than older age groups, with the distribution of sores differing across age groups (p = 3 x 10(-5)). Sores from which only Staphylococcus aureus was cultured differed in distribution to those with only Streptococcus pyogenes cultured (p = 3 x 10(-4)) and were more commonly found on the upper posterior lower limbs. Conclusions: Skin sores were predominantly found on exposed regions of the lower leg and distal upper limbs. The distribution of sores varied by age group and