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In vivo pH of induced soft-tissue abscesses in diabetic and nondiabetic mice
A N Bessman1, J Page, L J Thomas
1Department of Medicine, University of Southern California, Rancho Los Amigos Medical Center, Downey 90242.
Abstract:
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.
Insights
Diabetic mice exhibit significantly lower intra-abscess pH compared to nondiabetic mice, contributing to persistent infections. This acidic environment within abscesses is independent of bacterial type or count.
Area of Science:
- Microbiology
- Immunology
- Diabetology
Background:
- Infections in diabetic individuals often persist longer than in non-diabetic individuals.
- The internal environment of an abscess may influence infection persistence in diabetic hosts.
Purpose of the Study:
- To investigate the intra-abscess milieu as a factor in prolonged infections in diabetic hosts.
- To measure and compare in vivo intra-abscess pH in diabetic and non-diabetic mice.
Main Methods:
- Induced soft-tissue abscesses in two diabetic mouse models (genetically obese insulin-resistant and streptozocin-induced) and their respective controls.
- Inoculation with specific bacterial combinations: Bacteroides fragilis and Enterococcus (B + E), Staphylococcus epidermidis and Enterococcus (S + E), and S. aureus (SA).
- Measurement of intra-abscess pH on day 3 post-induction.
Main Results:
- Intra-abscess pH was consistently and significantly lower in all diabetic mice compared to controls across all bacterial challenge groups.
- Specific pH values in diabetic mice were 6.28 (B + E), 6.79 (S + E), and 6.52 (SA), versus 7.21, 7.30, and 7.17 in controls, respectively.
- No significant differences in total bacterial colony counts were observed between diabetic and non-diabetic groups.
Conclusions:
- A significantly lower intra-abscess pH is characteristic of the diabetic host.
- This acidic environment within abscesses is not attributable to the number or type of causative bacteria.
- The altered intra-abscess pH may be a key factor in the persistence of infections in diabetic individuals.
