Zuhal Zeybek

Growth ability of Gram negative bacteria in free-living amoebae.

When bacteria and free-living amoebae (FLAs) live both in natural waters and man-made aquatic systems, they constantly interact with each other. Some bacteria can survive and grow within FLAs. Therefore, it has recently been thought that FLAs play an important role in spreading pathogenic bacteria in aquatic systems. In this study we investigated the intracellular growing ability of 7 different Gram-negative bacteria (Pseudomonas fluorescens, Pseudomonas putida, Pasteurella pneumotropica, Aeromonas salmonicida, Legionella pneumophila serogroup 1, L. pneumophila serogroup 3, L. pneumophila serogroup 6) in four different FLA isolates (A1-A4). Among these, four bacterial isolates (P. fluorescens, P.putida, P.pneumotropica, A.salmonicida) and two free-living amoebae isolates (A3, A4) were isolated from the tap water in our city (Istanbul). It was found that 4 different Gram-negative bacteria could grow in A1, 2 different Gram-negative bacteria could grow in A2, 4 different Gram-negative bacteria could grow in A3, 1 Gram-negative bacterium could grow in A4. In conclusion, we think that this ability of growth could vary according to the characteristics of both bacteria and FLA isolates. Also, other factors such as environmental temperature, bacterial concentration, and extended incubation period may play a role in these interactions. This situation can be clarified with future studies.

Amoebicidal efficacy of a novel multi-purpose disinfecting solution: First findings

Free-living amoebae of the genus Acanthamoeba can cause a sight-threatening corneal infection, Acanthamoeba keratitis, mostly in contact lens wearers. The use of ineffective contact lens disinfecting solutions is one of the most important risk factors for this infection. This study concerns a new multi-purpose contact lens disinfecting solution, OPTI-FREE® PureMoist®, tested for its efficacy against Acanthamoeba trophozoites and cysts by using the most probable number technique for amoebic enumeration. Acanthamoeba castellanii ATCC 50373 and an environmental strain of Acanthamoeba genotype T4 isolated from tap water in Istanbul were used during the experiments. OPTI-FREE® PureMoist® achieved total kill (more than a 3-log reduction) of trophozoites of both strains before the manufacturer-recommended disinfection time (6h). In contrast, this solution had limited cysticidal activity against the ATCC strain but more against the environmental strain, with log reductions of 0.75 and 2.20, respectively, after 6h of exposure.