The yeasts Malassezia (M.) pachydermatis and Candida (C.) parapsilosis are often co-isolated in case of canine seborrhea dermatitis (SD) and also are emerging as opportunistic pathogens of immunocompromised human beings. Increased information about how their relationship results in biofilm production and an antifungal response would be useful to inform treatment and control. This study was designed to investigate biofilm production derived from co-culture of M. pachydermatis and C. parapsilosis from dog skin and to determine their in vitro antifungal susceptibility. We demonstrated that regardless of yeast strain or origin all single and dual cultures produced biofilms within 24 hours, and the greatest amount was present after 72 hours. Biofilm production from mixed cultures was greater than for single strains (P < .05). All sessile forms of the single and dual cultures were resistant to the tested antifungals itraconazole and ketoconazole, whereas planktonic forms were susceptible. The study suggests that dual cultures produce stronger biofilms that are likely to enhance persistence in skin lesions in dogs and result in greater resistance to antifungal treatment.

The aim of this study is to evaluate cellular interaction between free-living amoebae Naegleria fowleri strains and mammalian target cells in vitro. Two Thai strains of N. fowleri; Khon Kaen strain from the environment and Siriraj strain from the patient's cerebrospinal fluid and the Center of Disease Control VO 3081 strain from Atlanta (US) were studied. Human neuroblastoma (SK-N-MC) and African Green monkey Kidney (Vero) cells were used as target cells. Each cell line was inoculated with each strain of N. fowleri at a ratio of 1:1 and observed for 7 days. The uninoculated target cells and each strain of N. fowleri were used as control. The numbers of the challenged and unchallenged cells as well as the free-living amoebae were counted three times by trypan blue exclusion method. The inoculation began when the amoebae attached to the cell membrane and ingested the target cells. In this study, extensive cytopathogenesis with many floating inoculated cells and abundant number of amoebae were observed. The destruction pattern of both inoculated SK-N-MC and Vero target cells were similar. Interestingly, SK-N-MC was more susceptible to N. fowleri strains than the Vero cell. In addition, N. fowleri Siriraj strain showed the highest destruction pattern for each target cell. Our findings suggest that the SK-N-MC should be used as a base model for studying the neuropathogenesis in primary amoebic meningoencephalitis patients.

In order to understand the pathogenesis of Naegleria fowleri in primary amoebic meningoencephalitis, the human neuroblastoma (SK-N-MC) and African green monkey kidney (Vero) cells were studied in vitro. Amoeba suspension in cell-culture medium was added to the confluent monolayer of SK-N-MC and Vero cells. The cytopathic activity of N. fowleri trophozoites in co-culture system was elucidated by scanning electron microscope at 3, 6, 9, 12, and 24 h. Two strains of N. fowleri displayed well-organized vigorous pseudopods in Nelson's medium at 37 degrees C. In co-culture, the target monolayer cells were damaged by two mechanisms, phagocytosis by vigorous pseudopods and engulfment by sucker-like apparatus. N. fowleri trophozoites produced amoebostomes only in co-culture with SK-N-MC cells. In contrast, we could not find such apparatus in the co-culture with Vero cells. The complete destruction time (100%) at 1:1 amoeba/cells ratio of SK-N-MC cells (1 day) was shorter than the Vero cells (12 days). In conclusion, SK-N-MC cells were confirmed to be a target model for studying neuropathogenesis of primary amoebic meningoencephalitis.