The antibacterial activity of Libyan honey against gram negative bacilli: potential treatment agent for infectious diseases?

Aims: Honey has is a rich source of many compounds that exhibit anti-microbial, anti-inflammatory and pro-angiogenic properties. The emergence of antibiotic resistance in a wide variety of bacterial pathogens has generated renewed interest in natural antimicrobials. The aim of the present study was to assess the antibacterial activity of Libyan honey in vitro.

Methodology: The antibacterial activities of selected Libyan origin honey including Libyan Spring, AL-Sader, Thyme and Al-Hanone (at 25%, 50%, 75% and 100 % (w/v)) were tested against Yersinia enterocolitica, Escherichia coli and Proteus mirabilis using agar well-diffusion assay. The measurement of exponential bacterial growth curves was used to determine the effects on the microbial growth pattern spectrophotometrically at 600 nm. In addition, plate count methods were used to enumerate the effects of honey on the viable bacterial count.

Results and Discussion: Honey progressively inhibited bacterial growth at higher concentrations. This effect was variable depending on the honey type. For example, Al Sader honey showed the highest inhibition zones 21.3 mm ±0.8 against P. mirabilis followed by Thyme (21 mm ±0.5) and spring (20 mm ±0.5). Al-Hanone honey only exhibited effects against E. coli (14 mm ±0.5 and 8 mm ±0.4 at 100% w/v and 75% w/v, respectively). The Al Sader, spring and Thyme honey significantly reduced the Yersinia enterocolitica bacteria growth curve (p<0.05). All tested honey significant reduced E. coli growth from 5hrs compared to the control samples (p<0.05).

Conclusion: All honey tested showed inhibition of bacterial growth. Concentrated honeys were more effective against Yersinia enterocolitica, Escherichia coli and Proteus mirabilis. The efficacy of different types of honey was dependent on the honey concentration and origin.