D-lactic acid production as a monitor of the effectiveness of antimicrobial agents.
Most bacteria at an infection site obtain energy by the breakdown of glucose via microaerophilic or anaerobic pathways and in the process yield various end products. In this study, production of D-lactic acid by Staphylococcus aureus and Escherichia coli was correlated with glucose utilization by bacteria during exposure to antibiotics at subinhibitory, inhibitory, and suprainhibitory concentrations. D-Lactic acid production was further correlated with production of a tissue-destroying enzyme, hyaluronidase, by S. aureus. For E. coli, all agents tested showed dose-related bacterial killing, with the most noticeable being with ampicillin, piperacillin, and ciprofloxacin. Imipenem, ciprofloxacin, and chloramphenicol had the most dose-related effects on D-lactic acid production. With few exceptions, hyaluronidase production correlated well with D-lactic acid production in S. aureus. Subinhibitory concentrations of erythromycin and clindamycin effectively decreased accumulation of D-lactic acid and hyaluronidase. Determination of D-lactic acid production may perhaps serve as a means of independently monitoring the effects of antimicrobial agents on bacterial metabolic activity, which is an important aspect of antimicrobial action that remains relatively unexplored.
Smith
S M
SM
Microbiology Section, Veterans Administration Medical Center, East Orange, New Jersey 07019.
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006821:Hyaluronoglucosaminidase / Q000378:metabolism; D007773:Lactates / Q000096:biosynthesis*; D019344:Lactic Acid; D008826:Microbial Sensitivity Tests; D013211:Staphylococcus aureus / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism
D000900:Anti-Bacterial Agents; D007773:Lactates; D019344:Lactic Acid; D006821:Hyaluronoglucosaminidase; D005947:Glucose