Fungal Kinases With a Sweet Tooth: Pleiotropic Roles of Their Phosphorylated Inositol Sugar Products in the Pathogenicity of Cryptococcus neoformans Present Novel Drug Targeting Opportunities.

Invasive fungal pathogens cause more than 300 million serious human infections and 1.6 million deaths per year. A clearer understanding of the mechanisms by which these fungi cause disease is needed to identify novel targets for urgently needed therapies. Kinases are key components of the signaling and metabolic circuitry of eukaryotic cells, which include fungi, and kinase inhibition is currently being exploited for the treatment of human diseases. Inhibiting evolutionarily divergent kinases in fungal pathogens is a promising avenue for antifungal drug development. One such group of kinases is the phospholipase C1-dependent inositol polyphosphate kinases (IPKs), which act sequentially to transfer a phosphoryl group to a pre-phosphorylated inositol sugar (IP). This review focuses on the roles of fungal IPKs and their IP products in fungal pathogenicity, as determined predominantly from studies performed in the model fungal pathogen Cryptococcus neoformans, and compares them to what is known in non-pathogenic model fungi and mammalian cells to highlight potential drug targeting opportunities.

Opportunities and challenges to improving antibiotic prescribing practices through a One Health approach: results of a comparative survey of doctors, dentists and veterinarians in Australia.

OBJECTIVES: To explore and compare the knowledge, attitudes and experiences of doctors, dentists and veterinarians (as prescribers) in relation to antibiotic use and antibiotic resistance (AbR), and to consider the implications of these for policy-making that support a One Health approach. DESIGN: A cross-sectional survey conducted online. SETTING: Doctors, dentists and veterinarians practising in primary, secondary or tertiary care in Australia. PARTICIPANTS: 547 doctors, 380 dentists and 403 veterinarians completed the survey. MAIN OUTCOME MEASURES: Prescribers' knowledge, attitudes and perceptions of AbR, the extent to which a range of factors are perceived as barriers to appropriate prescribing practices, and perceived helpfulness of potential strategies to improve antibiotic prescribing in practice. RESULTS: There was substantial agreement across prescriber groups that action on AbR is required by multiple sectors and stakeholders. However, prescribers externalised responsibility to some extent by seeing the roles of others as more important than their own in relation to AbR. There were common and context-specific barriers to optimal prescribing across the prescriber groups. Prescriber groups generally perceived restrictive policies as unhelpful to supporting appropriate prescribing in their practice. CONCLUSIONS: The results have implications for implementing a One Health approach that involves doctors, dentists and veterinarians as key players to tackling the crisis of AbR. The findings are that (1) prescribers understand and are likely receptive to a One Health policy approach to AbR, (2) policy development should be sensitive to barriers that are specific to individual prescriber groups and (3) the development and introduction of interventions that might be perceived as reducing prescriber autonomy will need to be carefully designed and implemented.

Biochemical and functional characterisation of secreted phospholipase activities from Cryptococcus neoformans in their naturally occurring state.

A recent study demonstrated that phospholipase B (PLB), lysophospholipase (LPL) and lysophopholipase transacylase (LPTA) are secreted by Cryptococcus neoformans var. neoformans and showed that the amount of enzyme production correlated with virulence in mice. The present study characterised the extracellular enzyme activities further by radiometric assays and 31P nuclear magnetic resonance spectroscopy (NMR). All three enzymes were most active between 25 and 40 degrees C. Bovine lung surfactant and its major lipid components, disaturated phosphatidylcholine and phosphatidylglycerol, were the optimal substrates for PLB. Lysophosphatidylcholine was the favoured substrate for LPL and LPTA. PLB and LPL/LPTA were differentially affected by Triton X-100, and palmitoyl carnitine was a potent inhibitor of the three phospholipases. LPL and PLB activities were inhibited by dithiothreitol; N-ethylmaleimide inhibited LPL and LPTA activities. None of the enzymes was inhibited by N-bromosuccinimide or p-bromophenacyl bromide. Cellular disruption experiments indicated that >85% of the phospholipase activities were cell-associated, with LPL and LPTA being more easily released than PLB. At pH 5.5 and 7.0, the heat-inactivated secreted enzyme preparations decreased the viability of human neutrophils. This effect was attenuated by active supernates. The relative activities of the PLB, LPL and LPTA in the environment of neutrophils are likely to determine the fate of these cells in vivo. Both phospholipases and heat-stable substances secreted by C. neoformans at 37 degrees C could contribute to membrane degradation and virulence.