Biology subjects

Kingdon, A. D. H.

Publications and source records attributed to Kingdon, A. D. H..

3 recordsLinked to original sources

bioRxiv2026

Antimicrobial activity of polymyxin A, and characterisation of the cognate biosynthetic gene cluster within the genome of the producing Paenibacillus polymyxa.

We report the isolation and identification of a Paenibacillus polymyxa strain from the citizen science project; Swab and Send. Through whole genome sequencing we are able to describe the biosynthetic gene cluster of polymyxin A produced by P. polymyxa 1G (NCBI accession no. JBVPZV000000000), compare the pmxA, pmxB and pmxE genes to five other polymyxin genes encoding known polymyxin variants, and provide mass spectrometry data that supports the production of polymyxin A1 (1157 m/z) and A2 (1143 m/z). Polymyxins are ranked in the highest priority critically important antimicrobials classification by the WHO and are of particular importance for treating gram-negative multidrug resistant pathogens. Due to the discovery of polymyxins occurring in the 1940s, there is little genetic research around polymyxins, and the literature focusses primarily on clinically used polymyxin E (colistin) and polymyxin B. Previous literature suggests that polymyxin A1 has similar/lower toxicity to clinically used polymyxins E and B. To test if polymyxin A was able to overcome current resistance mechanisms to clinically used polymyxins, the cell free supernatant from P. polymyxa 1G was tested against a panel of clinical isolates with various resistance genes. We found that resistance genes mcr-1 and mcr-4 confer resistance to polymyxin A produced by our isolate meaning that, while polymyxin A has good antimicrobial activity, clinical resistance mechanisms already confer resistance to this variant of polymyxin.

microbiology↗

bioRxiv2026

Novel Class B2 and C β-lactamases harboured by Pseudomonas spp. wastewater isolates

IntroductionAntimicrobial resistance has existed in the environment long before its rapid emergence and detection in clinically relevant pathogens. Studying the resistance of environmental bacterial strains may allow novel resistance mechanisms to be identified before they appear in pathogenic strains. Gap StatementSearching for antimicrobial resistance genes in environmental bacteria represents an understudied research area compared to resistance within clinically relevant pathogens. AimTo evaluate resistance genes present within environmental non-aeruginosa Pseudomonas spp. isolates. MethodologyWe screened a set of bacterial isolates from untreated wastewater from Liverpool, UK, for the presence of extended spectrum {beta}-lactamases and carbapenemases. A sub-set of three resistant Pseudomonas spp. isolates were selected for whole-genome sequencing. We performed minimum inhibitory concentration assays against several {beta}-lactams, and ectopic expression of four novel resistance genes within Escherichia coli. ResultsHere, we report the discovery of novel class C {beta}-lactamase genes blaPFL7, blaPFL8 and blaPFL9, as well as a novel subclass B2 metallo-{beta}-lactamase blaPFM5 present within these strains. The class C genes encoded proteins with between 61-71% amino acid identity to the closest known match, blaPFL-1. These novel {beta}-lactamases degraded the cephalosporin nitrocefin and confer piperacillin and ceftazidime resistance to susceptible Escherichia coli when ectopically expressed. The {beta}-lactamase inhibitor tazobactam was effective at inhibiting these enzymes. The sub-class B2 metallo-{beta}-lactamase had 88% amino acid identity to its closet match blaPFM-1 and conferred carbapenem resistance to susceptible E. coli. The {beta}-lactamase inhibitors relebactam, vaborbactam, xeruborbactam and captopril had no impact on the carbapenem resistance phenotype. Analogues of all these novel genes (>95% nucleotide sequence identity) were identified within publicly available whole-genome sequencing data, suggesting they are found sporadically. ConclusionOur analysis adds to the growing number of {beta}-lactamase genes found from environmental Pseudomonas spp. and suggests that continued surveillance of this environmental reservoir for novel, clinically relevant, {beta}-lactamase genes is warranted.

microbiology↗

bioRxiv2022

Repurposing Vanoxerine as a new antimycobacterial drug and its impact on the mycobacterial membrane

Mycobacterium tuberculosis is a deadly pathogen, currently the leading cause of death worldwide from a single infectious agent through tuberculosis infections. If the End TB 2030 strategy is to be achieved, additional drugs need to be identified and made available to supplement the current treatment regimen. In addition, drug resistance is a growing issue, leading to significantly lower treatment success rates, necessitating further drug development. Vanoxerine (GBR12909), a dopamine re-uptake inhibitor, was recently identified as having anti-mycobacterial activity. Repurposing vanoxerine or its analogues to treat tuberculosis infections may allow a faster route to clinical use than novel drug discovery. However, its effects on Mycobacteria were not well characterised. Herein, we report vanoxerine as a disruptor of the membrane potential, inhibiting mycobacterial efflux and survival, with an undetectable level of resistance. This study suggests a mechanism of action for vanoxerine, which will allow for its continued development and optimisation for pre-clinical testing.

microbiology↗