Biology subjects

Wiles, S.

Publications and source records attributed to Wiles, S..

7 recordsLinked to original sources

bioRxiv2025

Using a "one-strain-many-compounds" (OSMAC) approach to screen a collection of diverse fungi from Aotearoa New Zealand for antibacterial activity against Escherichia coli

There is an urgent need to identify new chemical compounds with novel modes of action to help manage the antimicrobial resistance crisis. Fungi are prolific producers of secondary metabolites, including those with antimicrobial properties, and contain biosynthetic gene clusters that awaken only under certain growth conditions. In recent years, a wealth of novel fungal biosynthetic pathways and compounds have been identified, suggesting fungi remain a viable source for developing new antimicrobials. The International Collection of Microorganisms from Plants (ICMP) contains thousands of fungi and bacteria primarily sourced from Aotearoa New Zealand. Here, we report the results of our efforts to screen 32 fungal ICMP isolates for activity against Escherichia coli, a leading cause of deaths attributable to antimicrobial resistance. We used a one strain-many compounds (OSMAC) approach, growing the ICMP isolates on seven different media with different pH and various carbon and nitrogen sources. We also tested the isolates for activity at various ages. Our results indicate that several of the tested fungi possess anti-E. coli activity and are suitable for further study, including the aero-aquatic Ascomycete Hyaloscypha sp. ICMP 16864. Our results also provide further strong evidence for the impact of media on both fungal growth and bioactivity.

microbiology↗

bioRxiv2025

Real-world testing of the durability claims of a commercially available spray-on surface biocide

Self-disinfecting biocidal surfaces have been proposed as a solution to prevent infections caused by the transmission of microorganisms from frequently touched surfaces in hospitals and other settings. For example, surface anchoring quaternary ammonium salt (SAQAS)-based biocides are purported to maintain their antimicrobial potency for up to 30 days and are available as spray-on formulations. We tested the 30-day potency claim of a commercially available spray-on SAQAS-based biocide ("SAQAS-A") under "real-world" conditions in a microbiology laboratory where regular cleaning is routine. To do this, we determined the background microbial burden on high-traffic floor areas, routinely used bench areas, frequently touched handles, and glass surfaces for 30 days before and after applying SAQAS-A. Experiments were repeated three times, and data was analysed using two Generalised Linear Mixed Models. We observed that for >80% of bench samples, the number of viable bacteria recovered was below the highest acceptable level of 2.5 CFU/cm2, with minimal reduction in CFU recovery observed after SAQAS-A treatment. In contrast, the number of floor and glass samples in which the microbial burden exceeded 2.5 CFU/cm2 was greater after biocide application (12.7 and 73%, respectively) than before (4.8 and 37%, respectively). Analysis of all data using two statistical models confirmed that the application of SAQAS-A had no antimicrobial effect. In conclusion, our results indicate that SAQAS-A was ineffective in preventing surface contamination over 30 days in a real-world scenario where routine cleaning occurs. ImportanceWe tested the claim that a commercially available spray-on biocide could protect surfaces from microbial contamination for 30 days. In the presence of routine disinfection, we found that spray-on applications of the surface anchoring quaternary ammonium salt-based biocide did not protect frequently touched surfaces in a working microbiology research lab for up to 30 days. Our data show that users of this type of product should be aware of the limitations of manufacturers claims of "continued protection", and manufacturers should consider formulations that more reliably attach to surfaces. Similarly, regulatory and consumer protection agencies should provide clear guidance for companies wishing to make durability and longevity claims for biocidal surface applications.

microbiology↗

bioRxiv2022

Beyond consensus sequence: a quantitative scheme for inferring transmission using deep sequencing in a bacterial transmission model

Genomic surveillance provides a data source complementary to contact tracing to resolve putative transmission chains. However, the role of within-host diversity in transmission is understudied due to a lack of experimental and clinical datasets that capture within-host diversity in both donors and recipients. Here, we assess the utility of deep-sequenced genomic surveillance within a mouse transmission model where the gastrointestinal pathogen Citrobacter rodentium was controllably spread during co-housing of infected and naive animals. We observed that within-host variants were maintained over multiple transmission steps until fixation or elimination. We present a model for inferring the likelihood that a given pair of samples are linked by transmission, by comparing the allelic frequency at variant genomic loci. Our data affirm that within-host single nucleotide variants (iSNVs) can repeatedly pass from donor to recipient along the transmission chain, and the mere sharing of iSNVs between different transmission pairs offers limited confidence in identifying a transmission pair. Beyond the presence and absence of within-host variants, we show that differences arising in the relative abundance of iSNVs can infer transmission pairs with high precision. An important component of our approach is that the inference is based solely on sequence data, without incorporating epidemiological or demographic data for context. Our model, which substantially reduces the number of comparisons a contact tracer needs to consider, may enhance the accuracy of contact tracing and other epidemiological processes, including early detection of emerging transmission clusters.

genomics↗

bioRxiv2022

The efficacy of commercial decontamination agents differs between standardised test settings and real-world usage for a variety of bacterial species

Decontamination of surfaces and items plays an important role in reducing the spread of infectious microorganisms in many settings including hospitals and research institutes. Regardless of the location, appropriate decontamination procedures are required for maintaining biosafety and biosecurity. For example, effective decontamination of microbial cultures is essential to ensure proper biocontainment and safety within microbiological laboratories. To this end, many commercial decontamination agents are available which have been tested to a prescribed standard to substantiate their efficacy. However, these standardised tests are unlikely to accurately reflect all conditions encountered in medical and biomedical research. Despite this, laboratory workers and other users of decontamination agents may assume that all decontamination agents will work in all situations. We tested commonly used commercial decontamination agents against a range of bacterial species to determine their efficacy under real-world laboratory conditions. As each decontamination agent has a different recommended dilution for use, to compare their efficacy we calculated their effective ratio which reflects the difference between the manufacturer-recommended dilution and the dilution needed to achieve decontamination under real-world laboratory conditions. Effective ratios above 1 indicate that the agent was active at a dilution more dilute than recommended whereas effective ratios lower than 1 indicate that the agent required a higher concentration than recommended. Our results show that the quaternary ammonium agents TriGene Advance and Chemgene HLD4L were the most active out of the agents tested, with biocidal activity measured at up to 64 times the recommended dilution. In contrast, hypochlorite (bleach) and Prevail (stabilised hydrogen peroxide) had the lowest effective ratios amongst the tested agents. In conclusion, our data suggest that not all decontamination agents will work at the recommended dilutions under real-world laboratory conditions. We recommend that the protocols for the use of decontamination agents are verified under the specific conditions required to ensure they are fit for purpose.

microbiology↗

bioRxiv2017

Natural Colonization of Laboratory Mice with Staphylococcus aureus Primes a Systemic Immune Response

BackgroundWhether mice are an appropriate model for S. aureus infection and vaccination studies is a matter of debate, because they are not considered as natural hosts of S. aureus. Sparked by an outbreak of S. aureus infections in laboratory mice, we investigated whether laboratory mice are commonly colonized with S. aureus and whether this might impact on infection experiments.\n\nMethodsWe characterized 99 S. aureus isolates from laboratory mice (spa typing, virulence gene PCR), and quantified murine antibodies using FlexMap technology.\n\nResultsSpecific-pathogen-free mice from various vendors were frequently colonized with S. aureus (0-21%). S. aureus was readily transmitted from murine parents to offspring, which became persistently colonized. Most murine isolates belonged to the lineage CC88 (54%). Murine strains showed features of host adaptation, such as absence of hlb-converting phages and superantigen genes, as well as enhanced coagulation of murine plasma. Importantly, S. aureus colonization induced a systemic IgG response specific for numerous S. aureus proteins, including several vaccine candidates.\n\nConclusionLaboratory mice are natural hosts of S. aureus and, therefore, provide better infection models than previously assumed. Pre-exposure to S. aureus is a possible confounder in S. aureus infection and vaccination studies.

immunology↗

bioRxiv2016

A novel restraint device for injection of Galleria mellonella larvae that minimises the risk of accidental operator needle stick injury

Larvae of the insect Galleria mellonella are increasingly being used for studying pathogenic microbes and their virulence mechanisms, and as a rapid model for screening novel antimicrobial agents. The larvae (waxworms) are most frequently infected by injection of pathogenic organisms into the haemocoel through the insects prolegs. The mostly widely used method for restraining the waxworms for injection is by grasping them between the operators fingers, which puts the operator at risk of needle stick injury, an important consideration when working with highly pathogenic and/or drug-resistant microorganisms. While use of a stab proof glove can reduce this risk of injury, it does so at the loss of manual dexterity and speed, resulting in a more labour-intensive and cumbersome assay. We describe a simple cost effective device (the so-called Galleria Grabber) for restraining waxworms for injection that keeps the operators fingers clear of the needle thus reducing the risk of injury.

microbiology↗

bioRxiv2016

Effect of common and experimental anti-tuberculosis treatments on Mycobacterium tuberculosis growing as biofilms

Much is known regarding the antibiotic susceptibility of planktonic cultures of Mycobacterium tuberculosis, the bacterium responsible for the lung disease tuberculosis (TB). As planktonically-grown M. tuberculosis are unlikely to be entirely representative of the bacterium during infection, we set out to determine how effective a range of anti-mycobacterial treatments were against M. tuberculosis growing as a biofilm, a bacterial phenotype known to be more resistant to antibiotic treatment. Light levels from bioluminescently-labelled M. tuberculosis H37Rv (strain BSG001) were used as a surrogate for bacterial viability, and were monitored before and after 1 week of treatment. After treatment, biofilms were disrupted, washed and inoculated into fresh broth and plated onto solid media to rescue any surviving bacteria. We found that in this phenotypic state M. tuberculosis was resistant to the majority of the compounds tested. Minimum inhibitory concentrations (MICs) increased by 20-fold to greater than 1000-fold, underlying the potential of this phenotype to cause significant problems during treatment.

microbiology↗