Improved oral detection is a characteristic of Omicron infection and has implications for clinical sampling and tissue tropism.

BACKGROUND: The Omicron variant of concern is characterised by more than 50 distinct mutations, most in the spike protein. The implications of these for disease transmission, tissue tropism and diagnostic testing needs study. OBJECTIVES: We evaluated the performance of RT-PCR on saliva (SA) swabs and antigen testing on mid-turbinate MT samples relative to RT-PCR on MT swabs. Patients (n = 453) presenting for outpatient testing at the Groote Schuur Hospital COVID-19 testing centre in Cape Town South Africa were recruited. Participants were recruited during the Delta (n = 304) and Omicron (n = 149) waves. RESULTS: In 30 confirmed Delta infections, positive percent agreement (PPA) of RT-PCR on saliva was only 73% compared to a composite standard of either MT or SA RT-PCR positivity, with rapid decay by day 3 after symptom onset. In contrast, in the 70 Omicron infections, SA performed as well as, or better than, MT samples up to day 5, with an overall PPA of SA swabs of 96% and MT of 93%. A change in antigen test performance was noted, with PPA of 93% in Delta, but only 68% for Omicron. CONCLUSIONS: Altered shedding kinetics appear to be present in Omicron-infected patients with more viral RNA detectable in saliva. Saliva swabs are a promising alternative to nasal samples, especially early in infection when sampling of both sites could improve detection. Lower sensitivity of antigen tests in Omicron is a concern and requires further study.

Phenotypic/Genotypic Profile of OXA-10-Like-Harboring, Carbapenem-Resistant Pseudomonas aeruginosa: Using Validated Pharmacokinetic/Pharmacodynamic In Vivo Models To Further Evaluate Enzyme Functionality and Clinical Implications.

In vitro MICs and in vivo pharmacodynamics of ceftazidime and cefepime human-simulated regimens (HSR) against modified carbapenem inactivation method (mCIM)-positive Pseudomonas aeruginosa isolates harboring different OXA-10-like subtypes were described. The murine thigh model assessed ceftazidime (2 g every 8 h [q8h] HSR) and cefepime (2 g and 1 g q8h HSR). Phenotypes were similar despite possessing OXA-10-like subtypes with differing spectra. Ceftazidime produced ≥1-log10 killing in all isolates. Cefepime activity was dose dependent and MIC driven. This approach may be useful in assessing the implications of ß-lactamase variants.