An improved selective isolation medium for the recovery of Listeria monocytogenes from smoked fish

Aims: The aim of this study was to improve the selective isolation of Listeria monocytogenes from smoked haddock fillets. Methods and Results: Listeria selective agar (LSA) - Oxford formulation was supplemented with 25 lg ml)1 of colistin sulphate and 30 lg ml)1 of nalidixic acid. Inocula from four smoked haddock fillets produced colonies (approx. 2-13 bacteria g)1), identified as L. monocytogenes, on LSA supplemented with antimicrobial compounds (MLSA). Moreover, there was only negligible evidence of bacteria which were not L. monocytogenes on MLSA. In contrast, LSA supported dense bacterial growth, which was not equated with L. monocytogenes. Significance and Impact of the Study: The modified medium permitted the recovery of L. monocytogenes from smoked haddock fillets and reduced the growth of contaminating bacteria

An extract from teak (Tectona grandis) bark inhibited Listeria monocytogenes and methicillin resistant Staphylococcus aureus

Aims: The aim of this study was to characterize the inhibitory mechanism in teak (Tectona grandis) bark and to determine its effectiveness against Listeria monocytogenes and methicillin resistant Staphylococcus aureus (MRSA). Methods and Results: Methanol extracts of teak bark were inhibitory to L. monocytogenes and MRSA by means of disc diffusion. Gas chromatography-mass spectrometry, and 1H and 13C nuclear mass resonance analyses revealed that the inhibitory compound had a molecular weight of 174, and a structure of 5-hydroxy-1,4- naphthalenedione (Juglone). Conclusions: 5-hydroxy-1,4-naphthalenedione (Juglone) inhibited L. monocytogenes and MRSA. Significance and Impact of the Study: A compound in an extract of teak bark was inhibitory to L. monocytogenes and MRSA