Antimicrobial bioassay-guided fractionation of the endophytic fungi Neofusicoccum australe led to the isolation of a new unsymmetrical naphthoquinone dimer, neofusnaphthoquinone B (1), along with four known natural products (2–5). Structure elucidation was conducted by nuclear magnetic resonance (NMR) spectroscopic methods, and the antimicrobial activity of all the natural products was investigated, revealing 1 to be moderately active towards methicillin-resistant Staphylococcus aureus (MRSA) with a minimum inhibitory concentration (MIC) of 16 µg/mL.

Individuals naturally carry bacteria and other microbes as part of their natural flora, with some being opportunistic pathogens. Approximately 30% of the population is known to carry Staphylococcus aureus in their nasal cavity, an organism that causes infections ranging from soft tissue abscesses to toxic shock syndrome. This problem is compounded by the presence of antibiotic-resistant strains such as Methicillin-Resistant Staphylococcus aureus (MRSA). Commensal bacteria present on cadavers pose a risk to those who handle the body. As a Medical School Anatomy laboratory that performs hands-on cadaveric dissection, we wanted to know whether the embalming process is sufficient to kill all commensal bacteria that pose a risk to staff and students. Even if these strains do not cause disease in these individuals, secondary transmission could occur to friends and family, who may be at higher risk of acquiring an infection. Embalming is assumed to eliminate all microbial contamination on the body. However, there are limited studies to confirm this. This study characterises the incidence of antibiotic sensitive and resistant bacteria in cadavers donated for medical teaching and research. We have screened for Methicillin-Resistant Organisms (MRO) and Extended-Spectrum Beta-Lactamase (ESBL) producing bacteria. In this study group of cadavers, approximately 46% (16/35) carry an MRO, while 51% (18/35) carry an ESBL positive organism prior to embalming. By determining the organisms’ presence pre- and post-embalming, we can evaluate the embalming procedure’s effectiveness. Our results show embalming eliminates detectable microbes in about 51% (18/35) of the cadavers. MRO dropped by 75% (16 to 4 positive cadavers), while ESBL organisms went down by almost 95% (from 18 to 1 positive cadaver). There was a further decrease in the number of positive cadavers after storage at 4 °C to 6% (2/32). Thus, although the embalming process does not immediately sterilise all the cadavers, prolonged storage at 4 °C can further reduce the number of viable bacteria.

Honey has been widely purported as a natural remedy due to its antimicrobial and anti-inflammatory effects. In recent years, several studies have suggested that the considerably high methylglyoxal (MGO) concentration in Mānuka honey (MH) makes it particularly effective to manage bacterial overload, such as that observed in blepharitis. However, the poor solubility, high viscosity, and osmolarity of aqueous honey solutions, especially at the high MGO concentrations studied in the literature, render the formulation of an acceptable dosage form for topical application to the eyelids challenging. Here, the antibacterial properties of raw MH and alpha-cyclodextrin (α-CD)-complexed MH were evaluated at relatively low MGO concentrations, and a liquid crystalline-forming microemulsion containing α-CD-complexed MH was formulated. After determining pH and osmolarity, ocular tolerability was assessed using human primary corneal epithelial cells and chorioallantoic membranes, while the antibacterial efficacy was further evaluated in vitro. The α-CD–MH complex had significantly greater antibacterial activity against Staphylococcus aureus than either constituent alone, which was evident even when formulated as a microemulsion. Moreover, the final formulation had a physiologically acceptable pH and osmolarity for eyelid application and was well-tolerated when diluted 1:10 with artificial tear fluid, as expected to be the case after accidental exposure to the ocular surface in the clinical setting. Thus, a safe and efficient MH dosage form was developed for topical application to the eyelids, which can potentially be used to support optimal eyelid health in the management of blepharitis.

Mycobacterium tuberculosis is a deadly human pathogen that latently infects a third of the worlds population, resulting in approximately 1.5 million deaths per year. Due to the difficulties and expense of carrying out animal drug trials using M. tuberculosis and rodents, infections of the zebrafish Danio rerio with M. marinum have been used as a surrogate. However the methods so far described require specialised equipment and a high level of operator expertise. We investigated a natural infection model where zebrafish embryos are infected through incubation in media containing M. marinum. Using bioluminescently labelled M. marinum, we have characterised the nature of infection and established a model for interventional drug therapy. We have used a selection of traditional and experimental compounds to validate this model for anti-mycobacterial drug discovery. We observed that only three of the six treatments tested (Delamonid, SN30527 and rifampicin) retarded the growth of M. marinum in vitro. In contrast, five of the six treatments (Pretomanid, Delamanid, SN30488, SN30527 and rifampicin) retarded the growth of M. tuberculosis in vitro. Importantly, these same five treatments significantly reduced the bioluminescent signal from naturally infected zebrafish embryos. Overall this study has demonstrated that zebrafish embryos naturally infected with bioluminescent M. marinum M can be used for the rapid screening of anti-mycobacterial compounds with readily available equipment and limited expertise. The result is an assay that can be carried out by a wide variety of laboratories for minimal cost and without high levels of zebrafish expertise.

Planktonic cultures of Mycobacterium tuberculosis, the bacterium responsible for the lung disease tuberculosis (TB), are highly susceptible to killing by ascorbic acid (vitamin C). As planktonically grown M. tuberculosis are unlikely to be representative of the bacterium during infection, we set out to determine if ascorbic acid was also antibacterial against M. tuberculosis growing as a biofilm. We use biofilm growth as a model for the multiple phenotypic states M. tuberculosis can exist in during an infection. In our experiments we employed bioluminescent M. tuberculosis H37Rv (BSGTB1) in which light production is a non-destructive surrogate measure of bacterial viability. Light levels were monitored before and after treatment with 1mM to 256mM ascorbic acid. After 3 weeks of treatment, biofilms were disrupted, washed and inoculated into fresh media to look for sterilisation. Our findings show that ascorbic acid concentrations of 32mM or greater reduced bioluminescence produced by M. tuberculosis BSGTB1 growing in biofilms to background levels and resulted in the death of all cells within the biofilm. This indicates that M. tuberculosis biofilms are susceptible to inhibition and killing by ascorbic acid (vitamin C) and suggests that novel antibiotics with a mode of action similar to ascorbic acid could represent a useful avenue of investigation for TB treatment.

Planktonic cultures of Mycobacterium tuberculosis, the bacterium responsible for the lung disease tuberculosis (TB), are highly susceptible to killing by ascorbic acid (vitamin C). As planktonically grown M. tuberculosis are unlikely to be representative of the bacterium during infection, we set out to determine if ascorbic acid was also antibacterial against M. tuberculosis growing as a biofilm. We use biofilm growth as a model for the multiple phenotypic states M. tuberculosis can exist in during an infection. In our experiments we employed bioluminescent M. tuberculosis H37Rv (BSGTB1) in which light production is a non-destructive surrogate measure of bacterial viability. Light levels were monitored before and after treatment with 1mM to 256mM ascorbic acid. After 3 weeks of treatment, biofilms were disrupted, washed and inoculated into fresh media to look for sterilisation. Our findings show that ascorbic acid concentrations of 32mM or greater reduced bioluminescence produced by M. tuberculosis BSGTB1 growing in biofilms to background levels and resulted in the death of all cells within the biofilm. This indicates that M. tuberculosis biofilms are susceptible to inhibition and killing by ascorbic acid (vitamin C) and suggests that novel antibiotics with a mode of action similar to ascorbic acid could represent a useful avenue of investigation for TB treatment.