A Platform Approach to Cleavable Macrocycles for the Controlled Disassembly of Mechanically Caged Molecules.

Inspired by interlocked oligonucleotides, peptides and knotted proteins, synthetic systems where a macrocycle cages a bioactive species that is "switched on" by breaking the mechanical bond have been reported. However, to date, each example uses a bespoke chemical design. Here we present a platform approach to mechanically caged structures wherein a single macrocycle precursor is diversified at a late stage to include a range of trigger units that control ring opening in response to enzymatic, chemical, or photochemical stimuli. We also demonstrate that our approach is applicable to other classes of macrocycles suitable for rotaxane and catenane formation.

COVID-19 among University of Otago students living in North Dunedin households in the first half of 2022: was the prevalence underestimated?

AIMS: To estimate the prevalence of COVID-19 among occupants of North Dunedin student flats between Flat Orientation Week (Flo-Week, week starting 14 February 2022) and the end of Semester 1 (week starting 30 May 2022); to investigate the potential under-reporting of cases to the University of Otago and under-recording of positive rapid antigen test (RAT) results in My Covid Record; to explore the COVID-related experiences of students during the above period. METHODS: Randomly selected households in the North Dunedin area were visited at the end of Semester 1 and oral consent was sought for a short interview comprising closed- and open-ended questions. Households were eligible for inclusion if at least one resident was a University of Otago student. RESULTS: One hundred and thirty-five (96.4%) of 140 eligible households participated, and in 94.1% of these households at least one resident tested positive for COVID-19 between the start of Flo-Week and the date of the interview (a mean period of 109 days [standard deviation 3.6]). In total, 73.6% of the occupants in the participating households tested positive. Of the cases who were University of Otago students, 60.4% reported their positive status to the University. Of all cases diagnosed via a RAT, 66.9% uploaded their result to My Covid Record. Students reported various academic, financial and mental health stresses associated with the general COVID-19 situation during the study period. CONCLUSIONS: These findings suggest that the number of COVID-19 cases reported to the University of Otago between Flo-Week and the end of Semester 1 was a substantial underestimate of the true number, as was the number of cases recorded in My Covid Record. The findings also highlight the considerable impact that COVID-19 had on students during Semester 1.

Identification and characterization of Shigella boydii 20 serovar nov., a new and emerging Shigella serotype.

Analysis of 163 putative Shigella isolates from Canada and the USA showed biochemical reactions consistent with Shigella species, although none of the isolates reacted with antiserum raised against any of the well-established or provisional Shigella serotypes. All these isolates, provisionally designated serotype SH108, were positive for the ipaH gene and the invasion-associated locus. All fermented mannitol, were serologically indistinguishable from each other and showed no reaction in antisera prepared against Escherichia coli serotypes O1 to O181. PCR-RFLP analysis of the genes involved in O-antigen synthesis revealed a common pattern among these isolates that was distinct from recognized Shigella serotypes and E. coli. Between 1999 and 2003, isolates from across Canada were submitted to the National Laboratory for Enteric Pathogens for antibiotic susceptibility testing, phage typing and PFGE. These assays revealed heterogeneity among the members of this serotype. Antimicrobial susceptibility testing with seven antibiotics identified six profiles, with 90 % (45/50) of the isolates resistant to four or more antibiotics and 72 % (36/50) resistant to five or more. All isolates were typable using a panel of 16 phages, with 11 different phage types (PTs) represented. The most common PTs found were PT 3 (64 %), PT 6 (10 %) and PT 16 (6 %). Analysis of XbaI-restricted genomic DNA revealed 16 highly related patterns that were not readily distinguishable from those obtained for some other Shigella serotypes. The World Health Organization Collaborating Center for Shigella has added serotype SH108 to the Shigella scheme as S. boydii serotype 20 (serovar nov.). Strain SH108 (isolate 99-4528) is the reference strain for this serotype.

Comparison of Three Selective Enrichment Methods for the Isolation of Listeria monocytogenes from Naturally Contaminated Foods.

Three selective enrichment procedures-the U.S. Food and Drug Administration (FDA) method, the U.S. Department of Agriculture (USDA) method, and the Netherlands Government Food Inspection Service (NGFIS) method-were compared for isolating Listeria monocytogenes from contaminated foods. The foods were obtained from the refrigerators of patients with culture-proven listeriosis who were identified through multistate active surveillance in a U.S. population of 19 million. The study was designed to identify foods that may be important in transmission of L. monocytogenes in sporadic cases of human listeriosis. Of 899 foods analyzed by all three methods, 121 were positive for L. monocytogenes by at least one method. The three enrichment methods detected L. monocytogenes in 65% (FDA), 74% (USDA), and 74% (NGFIS) of the foods shown to contain L. monocytogenes . The differences among the three methods were not statistically significant. However, the recovery of L. monocytogenes by a combination of any two methods (USDA-FDA 88%, USDA-NGFIS 91%, FDA-NGFIS 87%) was significantly better than that by one method alone (p < 0.02). The differences among the combinations of methods were not statistically significant. These results suggest that at least two enrichment methods must be used in combination to recover L. monocytogenes from contaminated foods with a success rate near 90%. Correlations were observed between negative results and low (<0.3 CFU/g) level of L. monocytogenes contamination for the USDA (p << 0.001) and NGFIS (p << 0.001) methods. A similar but somewhat weaker association was observed for the FDA method (p < 0.06).