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Pseudomonas aeruginosa ( Pa ) is the predominant bacterial pathogen in people with cystic fibrosis (CF) and can be transmitted by airborne droplet nuclei. Little is known about the ability of ultraviolet band C (UV-C) irradiation to inactivate Pa at doses and conditions relevant to implementation in indoor clinical settings. We assessed the effectiveness of UV-C (265 nm) at up to seven doses on the decay of nebulized Pa aerosols (clonal Pa strain) under a range of experimental conditions. Experiments were done in a 400 L rotating sampling drum. A six-stage Andersen cascade impactor was used to collect aerosols inside the drum and the particle size distribution was characterized by an optical particle counter. UV-C effectiveness was characterized relative to control tests (no UV-C) of the natural decay of Pa . We performed 112 tests in total across all experimental conditions. The addition of UV-C significantly increased the inactivation of Pa compared with natural decay alone at all but one of the UV-C doses assessed. UV-C doses from 246-1968 µW s/cm 2 had an estimated effectiveness of approximately 50-90% for airborne Pa . The effectiveness of doses ≥984 µW s/cm 2 were not significantly different from each other ( p -values: 0.365 to ~1), consistent with a flattening of effectiveness at higher doses. Modelling showed that delivering the highest dose associated with significant improvement in effectiveness (984 µW s/cm 2 ) to the upper air of three clinical rooms would lead to lower room doses from 37-49% of the 8 h occupational limit. Our results suggest that UV-C can expedite the inactivation of nebulized airborne Pa under controlled conditions, at levels that can be delivered safely in occupied settings. These findings need corroboration, but UV-C may have potential applications in locations where people with CF congregate, coupled with other indoor and administrative infection control measures.

Background: Volunteer infection studies have become a standard model for evaluating drug efficacy against Plasmodium infections. Molecular techniques such as qPCR are used in these studies due to their ability to provide robust and accurate estimates of parasitaemia at increased sensitivity compared to microscopy. The validity and reliability of assays need to be ensured when used to evaluate the efficacy of candidate drugs in clinical trials., Methods: A previously described 18S rRNA gene qPCR assay for quantifying Plasmodium falciparum in blood samples was evaluated. Assay performance characteristics including analytical sensitivity, reportable range, precision, accuracy and specificity were assessed using experimental data and data compiled from phase 1 volunteer infection studies conducted between 2013 and 2019. Guidelines for validation of laboratory-developed molecular assays were followed., Results: The reportable range was 1.50 to 6.50 log 10 parasites/mL with a limit of detection of 2.045 log 10 parasites/mL of whole blood based on a parasite diluted standard series over this range. The assay was highly reproducible with minimal intra-assay (SD = 0.456 quantification cycle (C q ) units [0.137 log 10 parasites/mL] over 21 replicates) and inter-assay (SD = 0.604 C q units [0.182 log 10 parasites/mL] over 786 qPCR runs) variability. Through an external quality assurance program, the QIMR assay was shown to generate accurate results (quantitative bias + 0.019 log 10 parasites/mL against nominal values). Specificity was 100% after assessing 164 parasite-free human blood samples., Conclusions: The 18S rRNA gene qPCR assay is specific and highly reproducible and can provide reliable and accurate parasite quantification. The assay is considered fit for use in evaluating drug efficacy in malaria clinical trials.

We aimed to describe the epidemiology, multi-drug resistance and seasonal distribution of bacteria cultured within 12 months following lower limb orthopaedic surgery in tropical and subtropical Australian hospitals between 2010 and 2017. We collected data from four tropical and two subtropical hospitals. Categorical variables were examined using the Pearson Chi-squared test or Fisher's Exact test, and continuous variables with the Student t-test or Mann-Whitney U test. A Poisson regression model was used to examine the relationship between season, weather and the incidence of Staphylococcus and nonfermentative species. We found that at tropical sites, nonfermenters ( Pseudomonas aeruginosa and Acinetobacter baumannii ) were more common (28.7% vs. 21.6%, p = 0.018), and patients were more likely to culture multi-drug-resistant (MDR) nonfermenters (11.4% vs. 1.3%, p = 0.009) and MDR Staphylococcus aureus (35.9% vs. 24.6%, p = 0.006). At tropical sites, patients were more likely to be younger (65.9 years vs. 72.0, p = < 0.001), male (57.7% vs. 47.8%, p = 0.005), having knee surgery (45.3% vs. 34.5%, p = 0.002) and undergoing primary procedures (85.0% vs. 73.0%, p = < 0.001). Species were similar between seasons in both tropical and subtropical hospitals. Overall, we found that following lower limb orthopaedic surgery in tropical compared with subtropical Australia, patients were more likely to culture nonfermenters and some MDR species.

A real-time SYBR Green I assay was developed and evaluated as a biological and enzymatic polymerase chain reaction (Bio-PCR) protocol for the detection of Xanthomonas arboricola pv. pruni. Suppression subtractive hybridization was used to generate a X. arboricola pv. pruni-specific subtracted DNA library, using X. arboricola pv. corylina as the driver strain. Primer pair 29F/R, designed from cloned sequence, showed no homology to GenBank sequences and amplified a 344-bp product in all X. arboricola pv. pruni isolates. Compared with other published X. arboricola pv. pruni primers, this primer pair was shown to be the only one capable of differentiating X. arboricola pv. pruni from all other X. arboricola pathovars. A real-time assay was developed and shown to be capable of detecting less than 10 CFU and 0.1 pg of DNA. Epiphytic bacteria isolated from plum tissue was used to further evaluate the specificity of the assay. A Bio-PCR protocol, developed for field evaluation, confirmed X. arboricola pv. pruni isolation from asymptomatic and symptomatic plum tissue over a 9-week period between host flowering and the first appearance of leaf and fruit symptoms in an orchard. Dilution plating enabled X. arboricola pv. pruni numbers to be quantified, providing supportive evidence for the usefulness of the Bio-PCR protocol in plant pathology and quarantine surveillance.