Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

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    Zoonotic transmission of asymptomatic carriage Staphylococcus aureus on dairy farms in Canterbury, New Zealand.
    (Microbiology Society, 2024-12-04) Straub C; Taylor W; French NP; Murdoch DR; Priest P; Anderson T; Scott P
    Zoonotic pathogen transmission is of growing concern globally, with agricultural intensification facilitating interactions between humans, livestock and wild animals. Staphylococcus aureus is a major human pathogen, but it also causes mastitis in dairy cattle, leading to an economic burden on the dairy industry. Here, we investigated transmission within and between cattle and humans, including potential zoonotic transmission of S. aureus isolated from cattle and humans from three dairy farms and an associated primary school in New Zealand. Nasal swabs (N=170) were taken from healthy humans. Inguinal and combined nasal/inguinal swabs were taken from healthy cattle (N=1163). Whole-genome sequencing was performed for 96 S. aureus isolates (44 human and 52 cattle). Multilocus sequence typing and assessments of antimicrobial resistance and virulence were carried out. Potential within- and across-species transmission events were determined based on single nucleotide polymorphisms (SNPs). Thirteen potential transmission clusters were detected, with 12 clusters restricted to within-species and one potential zoonotic transmission cluster (ST5). Potential transmission among cattle was mostly limited to single age groups, likely because different age groups are managed separately on farms. While the prevalence of antimicrobial resistance (AMR) was low among both bovine and human isolates, the discovery of an extended-spectrum beta-lactamase gene (bla TEM-116) in a bovine isolate was concerning. This study provides evidence around frequency and patterns of potential transmission of S. aureus on dairy farms and highlights the AMR and virulence profile of asymptomatic carriage S. aureus isolates.
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    Editorial: Mobile DNA element-driven evolution of bacterial pathogens
    (Frontiers Media S A, 2025-03-19) Cloeckaert A; Zygmunt MS; Vale FF; Altermann E; Li T
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    An accumulated mutation gained in mosquito cells enhances Zika virus virulence and fitness in mice.
    (American Society for Microbiology, 2024-10-16) Fan X-X; Li R-T; Zhu Y-B; Chen Q; Li X-F; Cao T-S; Zhao H; Cheng G; Qin C-F; Heise MT
    Zika virus (ZIKV) remains a significant public health threat worldwide. A number of adaptive mutations have accumulated within the genome of ZIKV during global transmission, some of which have been linked to specific phenotypes. ZIKV maintains an alternating cycle of replication between mosquitoes and vertebrate hosts, but the role of mosquito-specific adaptive mutations in ZIKV has not been well investigated. In this study, we demonstrated that serial passaging of ZIKV in mosquito Aag2 cells led to the emergence of critical amino acid substitutions, including A94V in the prM protein and V153D and H401Y in the E protein. Further characterization via reverse genetics revealed that the H401Y substitution in the E protein did not augment viral replication in mosquitoes but significantly enhanced neurovirulence and lethality compared with those of the wild-type (WT) virus in mice. More importantly, the H401Y mutant maintained its virulence phenotype in mice after propagation in mosquitoes in mosquito-mouse cycle model. In particular, recombinant ZIKV harboring the H401Y substitution showed enhanced competitive fitness over WT ZIKV in various mammalian cells and mouse brains, but not in mosquito cells. Notably, the H401Y substitution in the ZIKV E protein has been detected in recent isolates derived from both mosquitoes and humans in Asia and the Americas. In summary, our findings not only identify a novel virulence determinant of ZIKV but also highlight the complexity of the relationship between the evolution of vector-borne viruses and their clinical outcome in nature.
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    Genomic and clinical characteristics of campylobacteriosis in Australia.
    (Microbiology Society, 2024-01) Cribb DM; Moffatt CRM; Wallace RL; McLure AT; Bulach D; Jennison AV; French N; Valcanis M; Glass K; Kirk MD
    Campylobacter spp. are a common cause of bacterial gastroenteritis in Australia, primarily acquired from contaminated meat. We investigated the relationship between genomic virulence characteristics and the severity of campylobacteriosis, hospitalisation, and other host factors.We recruited 571 campylobacteriosis cases from three Australian states and territories (2018-2019). We collected demographic, health status, risk factors, and self-reported disease data. We whole genome sequenced 422 C. jejuni and 84 C. coli case isolates along with 616 retail meat isolates. We classified case illness severity using a modified Vesikari scoring system, performed phylogenomic analysis, and explored risk factors for hospitalisation and illness severity.On average, cases experienced a 7.5 day diarrhoeal illness with additional symptoms including stomach cramps (87.1 %), fever (75.6 %), and nausea (72.0 %). Cases aged ≥75 years had milder symptoms, lower Vesikari scores, and higher odds of hospitalisation compared to younger cases. Chronic gastrointestinal illnesses also increased odds of hospitalisation. We observed significant diversity among isolates, with 65 C. jejuni and 21 C. coli sequence types. Antimicrobial resistance genes were detected in 20.4 % of isolates, but multidrug resistance was rare (0.04 %). Key virulence genes such as cdtABC (C. jejuni) and cadF were prevalent (>90 % presence) but did not correlate with disease severity or hospitalisation. However, certain genes (e.g. fliK, Cj1136, and Cj1138) appeared to distinguish human C. jejuni cases from food source isolates.Campylobacteriosis generally presents similarly across cases, though some are more severe. Genotypic virulence factors identified in the literature to-date do not predict disease severity but may differentiate human C. jejuni cases from food source isolates. Host factors like age and comorbidities have a greater influence on health outcomes than virulence factors.
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    Pathogenicity of Beauveria bassiana PfBb and Immune Responses of a Non-Target Host, Spodoptera frugiperda (Lepidoptera: Noctuidae)
    (MDPI AG, 8/10/2022) Gao Y-P; Luo M; Wang X-Y; He X; Lu W; Zheng X-L
    Exploring the pathogenicity of a new fungus strain to non-target host pests can provide essential information on a large scale for potential application in pest control. In this study, we tested the pathogenicity of Beauveria bassiana PfBb on the important agricultural pest Spodoptera frugiperda (Lepidoptera: Noctuidae) by determining the relative activities of protective enzymes and detoxifying enzymes in different larval instars. Our results show that the B. bassiana PfBb strain could infect all six larval instars of S. frugiperda, and its virulence to S. frugiperda larvae gradually increased with an increase in spore concentration. Seven days after inoculation, the LC50 of B. bassiana PfBb was 7.7 × 105, 5.5 × 106, 2.2 × 107, 3.1 × 108, 9.6 × 108, and 2.5 × 1011 spores/mL for first to sixth instars of S. frugiperda, respectively, and the LC50 and LC90 of B. bassiana PfBb for each S. frugiperda instar decreased with infection time, indicating a significant dose effect. Furthermore, the virulence of B. bassiana PfBb to S. frugiperda larvae gradually decreased with an increase in larval instar. The activities of protective enzymes (i.e., catalase, peroxidase, and superoxide dismutase) and detoxifying enzymes (i.e., glutathione S-transferases, carboxylesterase, and cytochrome P450) in S. frugiperda larvae of the first three instars infected with B. bassiana PfBb changed significantly with infection time, but such variations were not obvious in the fifth and sixth instars. Additionally, after being infected with B. bassiana PfBb, the activities of protective enzymes and detoxification enzymes in S. frugiperda larvae usually lasted from 12 to 48 h, which was significantly longer than the control. These results indicate that the pathogenicity of B. bassiana PfBb on the non-target host S. frugiperda was significant but depended on the instar stage. Therefore, the findings of this study suggest that B. bassiana PfBb can be used as a bio-insecticide to control young larvae of S. frugiperda in an integrated pest management program.