Natural immunomodulation of host defense against Klebsiella aerogenes: evidence from Licorice extract

Document Type : Research Paper

Authors

Department of Microbiology, College of Veterinary Medicine, University of Baghdad, Iraq.

10.22103/jab.2026.27079.1880

Abstract

Objective
The emergence of Klebsiella aerogenes as a possible pathogen has been linked with both gastrointestinal and systemic infections in animals and human beings. Antimicrobial resistance among strains of Klebsiella species has increased. Thus, there is a need for seeking alternative sources of immunomodulating substances. Hence, the objective of this study was to evaluate the immunomodulatory and prophylactic effects of Glycyrrhiza glabra (licorice extract) on mouse models of Klebsiella aerogenes infection.
Materials and methods
Samples were obtained from diarrhea cases of 50 cats for culturing and identification of K. aerogenes. These bacteria were then used in experimentally infecting 48 mice of the Swiss albino strain. A total of six groups of eight mice each were included. Three groups were given oral licorice extract at various doses of 50, 150, and 250 mg/mL. Two control groups comprising of negative controls (oral administration of PBS) and positive control. An additional group was only provided with extract but not infected. Licorice extract was administered twice weekly for 21 days followed by injection with Klebsiella aerogenes bacteria at 1.5 × 10⁸ CFU/mL.
Results
Infected untreated mice had significant increases in inflammatory and hematological indices compared to negative control mice (P ≤ 0.05). A significant rise in white blood cells' count occurred in infected mice, whose mean value amounted to 12.8 ± 1.4 ×10³/µL. While those in control group were lower at 6.2 ± 0.9 ×10³/µL. Moreover, IL-6 levels in infected mice significantly increased to 85.6 ± 5.3 pg/mL versus 28.4 ± 3.1 pg/mL in controls. Infected untreated mice experienced severe inflammatory and degenerative histopathological lesions. On the other hand, infected but licorice-treated mice exhibited reduced inflammation, IL-6 levels, improvements in hematological indices, and lesser degree of tissue damage. The lowest dose (50 mg/mL) was shown to produce maximum protective effect, implying that there is no clear relationship between the concentration of licorice and its biological impact on experimental mice.
Conclusion
Glycyrrhiza glabra extract produced certain anti-inflammatory and protective effects against infection caused by Klebsiella aerogenes in mice. Licorice extracts decreased inflammation and improved pathological alterations observed in infected animals. Glycyrrhiza glabra may be regarded as an interesting candidate for development as a natural immunomodulator; nonetheless, more research needs to be done.

Keywords

References

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Agricultural Biotechnology Journal
Volume 18, Issue 3
June 2026
Pages 411-430

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