Type IV pili (T4P) contain hundreds of major subunits, but minor subunits are also required for assembly and function. Here we show that Pseudomonas aeruginosa minor pilins prime pilus assembly and traffic the pilus-associated adhesin and anti-retraction protein, PilY1, to the cell surface. PilV, PilW and PilX require PilY1 for inclusion in surface pili and vice versa, suggestive of complex formation. PilE requires PilVWXY1 for inclusion, suggesting that it binds a novel interface created by two or more components. FimU is incorporated independently of the others and is proposed to couple the putative minor pilin-PilY1 complex to the major subunit. The production of small amounts of T4P by a mutant lacking the minor pilin operon was traced to expression of minor pseudopilins from the P. aeruginosa type II secretion (T2S) system, showing that under retraction-deficient conditions, T2S minor subunits can prime T4P assembly. Deletion of all minor subunits abrogated pilus assembly. In a strain lacking the minor pseudopilins, PilVWXY1 and either FimU or PilE comprised the minimal set of components required for pilus assembly. Supporting functional conservation of T2S and T4P minor components, our 1.4 Å crystal structure of FimU revealed striking architectural similarity to its T2S ortholog GspH, despite minimal sequence identity. We propose that PilVWXY1 form a priming complex for assembly, and that PilE and FimU together stably couple the complex to the major subunit. Trafficking of the anti-retraction factor PilY1 to the cell surface allows for production of pili of sufficient length to support adherence and motility.

Respiratory viral infections are associated with a wide range of acute syndromes and infectious disease processes in children and adults worldwide. Many viruses are implicated in these infections, and these viruses are spread largely via respiratory means between humans but also occasionally from animals to humans.

Many severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serology tests have proven to be less accurate than expected and do not assess antibody function as neutralizing, correlating with protection from reinfection. A new assay technology measuring the interaction of the purified SARS-CoV-2 spike protein receptor binding domain (RBD) with the extracellular domain of the human angiotensin-converting enzyme 2 (hACE2) receptor detects these important antibodies.

Coronavirus disease (COVID) serological tests are essential to determine the overall seroprevalence of a population and to facilitate exposure estimates within that population. We performed a head-to-head assessment of enzyme immunoassays (EIAs) and point-of-care lateral flow assays (POCTs) to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. Demographics, symptoms, comorbidities, treatment, and mortality of patients whose sera were used were also reviewed. Six EIAs (Abbott, Affinity, Bio-Rad, DiaSorin, Euroimmun, and Roche) and six POCTs (BTNX, Biolidics, Deep Blue, Genrui, Getein BioTech, and Innovita) were evaluated for the detection of SARS-CoV-2 antibodies in known COVID-19-infected individuals.

VITEK 2 (bioMérieux Inc., Durham, NC) is a widely used commercial antimicrobial susceptibility test system. We compared MIC results obtained by VITEK 2 AST-GN69 and AST-XN06 cards to those obtained by CLSI broth microdilution (BMD) for 255 isolates of Enterobacteriaceae, including 25 isolates of carbapenem-resistant Enterobacteriaceae. In total, 25 antimicrobial agents were examined. For 10 agents, MIC data were evaluated using two sets of breakpoints: 1) VITEK 2 breakpoints, which utilized the 2009 FDA breakpoints at the time of the study and are equivalent to the 2009 CLSI M100-S19 breakpoints, and 2) the 2014 CLSI M100-S24 breakpoints. There was an overall 98.7% essential agreement (EA). Categorical agreement was 95.5% (CA) by the VITEK 2 breakpoints and 95.7% by the CLSI breakpoints. There was 1 very major error (VME) (0.05%) observed by VITEK 2 breakpoints (cefazolin) and 8 VMEs (0.5%) by CLSI breakpoints (2 each for aztreonam, cefepime and ceftriaxone and 1 for cefazolin and ceftazidime). Fifteen major errors (MEs) (0.4%) were noted by VITEK 2 breakpoints, and 8 (0.5%) by CLSI breakpoints. Overall, the VITEK 2 performance was comparable to BMD for testing a limited number of Enterobacteriaceae commonly isolated by clinical laboratories. Ongoing studies are warranted to assess performance in isolates with emerging resistance.