Introduction: Trigona thoracica propolis is known to have antimicrobial properties, however its
antileptospiral properties and its synergistic effects with commonly prescribed antibiotics are scarcely
documented. This study aimed to evaluate the antileptospiral properties of Trigona thoracica against
pathogenic Leptospira species (spp.) and to study its synergistic effects with commonly prescribed
antibiotics. Materials and Methods: The tested Leptospira serovars were Australis, Bataviae, Canicola and
Javanica. Aqueous extract propolis (AEP) and ethanolic extracts propolis (EEP) were used. Broth dilution
methods were used to determine the Minimum Inhibitory Concentration (MIC), Minimum Bactericidal
Concentration (MBC) and the synergistic effects between the propolis and the tested antibiotics. The
synergistic effects was evaluated by using the fractional inhibitory concentration (FIC) index. Morphological
changes of the treated Leptospira were observed under a Scanning Electron Microscope (SEM). Results: The
AEP and EEP were found to have antileptospiral properties against the tested Leptospira spp. The synergy
result showed that only combination of AEP and penicillin G against serovar Australis has demonstrated
synergistic effect with the FIC index of 0.38. Morphological study using SEM showed significant structural
changes of the treated Leptospira spp. Conclusions: The result suggests that Trigona thoracica propolis could
potentially be used as either a complimentary or an alternative therapeutic agent against pathogenic
Leptospira spp.