Clinical features of COVID-19 rapid antigen test exposures reported by an Australian poisons information centre: a prospective study

INTRODUCTION

Coronavirus disease COVID-19 rapid antigen tests are a useful tool in detecting infection, and their use has increased in many countries since they became commercially available in late 2021. Some rapid antigen tests contain sodium azide, which can be toxic in small doses. This study aimed to describe the clinical characteristics of exposures to COVID-19 rapid antigen tests.

METHODS

This is a prospective study conducted by the New South Wales Poisons Information Centre. From 22 January 2022 to 31 August 2022, rapid antigen test exposures were followed up to obtain outcome information. Data collected included: brand/ingredients, exposure route, demographics, symptoms, and disposition.

RESULTS

We recorded 218 exposures in the seven-month study period. Complete follow-up information was available in 75% (n = 164). There were 53 exposures to sodium azide-containing products (35 with follow-up data) and 165 to non-sodium azide-containing products and unknown ingredient exposures (129 with follow-up data). Overall, unintentional exposures predominated (n = 182), and 151 were ingestions. The vast majority (>90%) did not develop symptoms, and all symptoms that developed were mild. Most cases (95%, n = 208) did not require referral to a healthcare facility.

CONCLUSIONS

In this prospective series, few patients developed symptoms, regardless of the sodium azide content, likely due to low concentration and low volume within the test kits. However, ongoing toxicovigilance is warranted.

Broad-host-range vector system for synthetic biology and biotechnology in cyanobacteria

Inspired by the developments of synthetic biology and the need for improved genetic tools to exploit cyanobacteria for the production of renewable bioproducts, we developed a versatile platform for the construction of broad-host-range vector systems. This platform includes the following features: (i) an efficient assembly strategy in which modules released from 3 to 4 donor plasmids or produced by polymerase chain reaction are assembled by isothermal assembly guided by short GC-rich overlap sequences. (ii) A growing library of molecular devices categorized in three major groups: (a) replication and chromosomal integration; (b) antibiotic resistance; (c) functional modules. These modules can be assembled in different combinations to construct a variety of autonomously replicating plasmids and suicide plasmids for gene knockout and knockin. (iii) A web service, the CYANO-VECTOR assembly portal, which was built to organize the various modules, facilitate the in silico construction of plasmids, and encourage the use of this system. This work also resulted in the construction of an improved broad-host-range replicon derived from RSF1010, which replicates in several phylogenetically distinct strains including a new experimental model strain Synechocystis sp. WHSyn, and the characterization of nine antibiotic cassettes, four reporter genes, four promoters, and a ribozyme-based insulator in several diverse cyanobacterial strains.

Influence of specific growth rate and nutrient-limitation upon the sensitivity of Escherichia coli towards polymyxin B

The sensitivity of Escherichia coli to the lytic action of polymyxin B was assessed for cells grown in a chemostat at a variety of specific growth rates and under conditions of carbon, nitrogen, phosphorus and magnesium limitation. Magnesium and phosphorus limited cells demonstrated a trend of increased resistance with increasing growth-rate, whereas carbon and nitrogen limited cells increased their sensitivity as the growth rate increased. Divergent patterns of sensitivity, such as these, allowed a number of models for resistance towards polymyxin to be assessed. It was not possible to attribute polymyxin sensitivity to any single envelope component; rather the patterns of sensitivity reflect, in a complex manner, presence of envelope proteins and acidic phospholipids.

Antimicrobial activity of n-alkyltrimethylammonium bromides: influence of specific growth rate and nutrient limitation

The antimicrobial activity of an homologous series of n-alkyltrimethylammonium bromides has been assessed towards Escherichia coli grown at a variety of specific growth rates and under various conditions of nutrient limitation. For each individual set of growth conditions activity was parabolically related to the n-alkyl chain length of the compounds and thus to compound lipophilicity (log P). The compound that showed optimal activity and thereby optimal lipophilicity (log Po) changed according to growth rate and nutrient limitation. Such changes are related to variations in the gross cell envelope composition of the cultures (phospholipid, lipopolysaccharide, neutral lipids, proteins). The data therefore support the hypothesis that changes in growth rate and nutrient limitation alter the overall lipophilicity of the cell envelope and thereby the optimal value of log P for compounds to traverse it. Additionally, the data suggest that for the compounds examined, the neutral acidic:neutral phospholipid ratios of the cell envelope, also influence the permeation of it.

Influence of specific growth rate and nutrient limitation upon the sensitivity of Escherichia coli towards chlorhexidine diacetate

The sensitivity of Escherichia coli to chlorhexidine has been assessed for cells grown in a chemostat at a variety of specific growth rates, under conditions of carbon, nitrogen, phosphorus and magnesium limitation. At slow rates of growth (ca 0.08/h) little difference in sensitivity was observed. As growth rate was increased, however, the sensitivity of nitrogen- and carbon-limited cells increased whilst that of magnesium- and phosphate-limited cells decreased. It was not possible to correlate the observed patterns of chlorhexidine sensitivity with any single measure of cell envelope composition (phospholipid content, lipopolysaccharide, envelope proteins, etc.). The results presented are not consistent, therefore, with any simple model for chlorhexidine binding or action and more probably reflect subtle interaction between chlorhexidine, phospholipid-lipopolysaccharide complexes and cations within the envelope.

The effect of vasovasostomy upon the structure of the vas deferens in rats

The reasons for the discrepancy between reappearance of sperm in the ejaculate following vasovasostomy and pregnancy rates remain obscure. To determine the possible adverse effects of reanastomosis upon the structure of the vas deferens, immediate microsurgical vasovasostomy was performed on 60 adult Sprague-Dawley rats. The fine structure of the mucosa, as seen by scanning electron microscopy, showed only subtle, transient changes with return to normal architecture within 3 months. Luminal dilatation, rather than stenosis, was a constant late finding. It is concluded that microsurgical reanastomosis has little, if any, permanent deleterious effect upon the structure of the vas deferens.