In Vivo pH of Induced Soft-Tissue Abscesses in Diabetic and Nondiabetic Mice

Infections in the diabetic host have been shown to persist longer than those in the nondiabetic host. To investigate whether intra-abscess milieu might be a contributing factor to this persistence, the in vivo intra-abscess pH was measured in induced soft-tissue abscesses in diabetic and nondiabetic mice. Two models (female genetically obese insulin-resistant and male streptozocin-induced diabetic mice) were used with appropriate controls. The bacteria injected to produce the soft-tissue abscesses were Bacteroides fragilis and Enterococcus (B + E), Staphylococcus epidermidis and Enterococcus (S + E), and S. aureus (SA). Intra-abscess pH measured on day 3 was consistently and significantly lower in all diabetic mice compared with their controls. In the diabetic mice, the pH of an abscess induced with B + E, S + E, and SA was 6.28 (n = 17), 6.79 (n = 10), and 6.52 (n = 10), respectively; the pH in the controls was 7.21 (n = 20), 7.30 (n = 10), and 7.17 (n = 10), respectively. Differences in all groups between diabetic and nondiabetic mice were significant. The blood glucose values of the diabetic mice averaged 722 mg/dl, and in the nondiabetic mice were 210 mg/dl. No animals were ketotic. There were no significant differences in total colony counts between any groups. In conclusion, there is a significantly lower pH in the abscess of the diabetic host compared with the nondiabetic host that is not related to the numbers or types of causative bacteria.