Efflux modulators from Momordica balsamina L. in multidrug resistant bacterial strains

Leonard Amaral, Cátia Ramalhete, G. Spengler , Julianna Serly, Joseph Molnár, Silva Mulhovo, Maria José U Ferreira

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Bacterial infections are becoming more challenging to treat as a result of the emergence of multidrug resistant (MDR) bacteria. The genetic and physiological basis for the MDR phenotype of clinical isolates has been associated with porin deficiencies and over-expression of efflux pumps which, when present in the same organism, decrease the permeability of the bacteria to two or more unrelated antibiotics. The problem of resistant bacteria (Gram-positive and Gram-negative) highlights the urgent need for new drugs. A solution is the development of efflux pump inhibitors that will restore the activity of the antibiotic to which the bacteria became resistant [1].
In this study we evaluated the efflux modulating effect of cucurbitane-type triterpenes isolated from the methanol extract of aerial parts of Momordica balsamina L. in some Gram-positive (Enterococcus faecalis and Staphylococcus aureus) and Gram-negative (E. coli and Salmonella enteritidis) bacterial strains. The previously developed semi-automated real-time fluorometric method was used to monitor the accumulation and extrusion of the fluorochrome ethidium bromide, in the presence and absence of tested compounds [2].
The tested compounds have shown to increase the accumulation of ethidium bromide in the Gram-positive bacteria tested, with higher accumulation than observed in positive controls, such as thioridazine. No increase in EB accumulation was observed in S. enteridis and E. coli strains tested.
These findings show that these compounds have potential to be used as efflux pump inhibitors of Gram- positive bacteria, and thus to restore the activity of antibiotics. This is especially important due to the increase of multidrug resistance in Gram-positive pathogenic bacteria like S. aureus, S. pneumoniae and Enterococcus spp.
Original languageEnglish
Pages (from-to)896
Number of pages1
JournalPlanta Medica
VolumeVol. 75
Issue numbern.º 9
Publication statusPublished - Jul 2009


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