Identification of two abundant Aerococcus urinae cell wall-anchored proteins

A mouse model displays host and bacterial strain differences in Aerococcus urinae urinary tract infection

In recent years, the clinical significance of Aerococcus urinae has been increasingly recognized. A. urinae has been implicated in cases of urinary tract infection (UTI; acute cystitis and pyelonephritis) in both male and female patients, ranging from children to older adults. Aerococcus urinae can also be invasive, causing urosepsis, endocarditis, and musculoskeletal infections. Mechanisms of pathogenesis in A. urinae infections are poorly understood, largely due to the lack of an animal model system. In response to this gap, we developed a model of A. urinae urinary tract infection in mice. We compared A. urinae UTI in female C3H/HeN and C57BL/6 mice and compared four clinical isolates of A. urinae isolated from patients with UTI, urgency urinary incontinence, and overactive bladder. Our data demonstrate that host genetic background modulates A. urinae UTI. Female C57BL/6 female mice rapidly cleared the infection. Female C3H/HeN mice, which have inherent vesicoureteral reflux that flushes urine from the bladder up into the kidneys, were susceptible to prolonged bacteriuria. This result is consistent with the fact that A. urinae infections most frequently occur in patients with underlying urinary tract abnormalities or disorders that make them susceptible to bacterial infection. Unlike uropathogens such as E. coli, which cause infection and inflammation both of the bladder and kidneys in C3H/HeN mice, A. urinae displayed tropism for the kidney, persisting in kidney tissue even after clearance of bacteria from the bladder. Aerococcus urinae strains from different genetic clades displayed varying propensities to cause persistent kidney infection. Aerococcus urinae infected kidneys displayed histological inflammation, neutrophil recruitment and increased pro-inflammatory cytokines. These results set the stage for future research that interrogates host-pathogen interactions between A. urinae and the urinary tract.

Summary:Aerococcus urinae clinical isolates are genetically diverse and display differential capacity to cause UTI in a mouse model. Infection was rapidly cleared from the bladder, but persisted and caused inflammation in the kidney.

Antibody kinetics and clinical course of COVID-19 a prospective observational study

Background

Serological response and association to clinical manifestation is important for understanding the pathogenesis of COVID-19.

Materials and methods

A prospective observational study was conducted where antibody responses of IgG and IgA towards SARS-CoV-2 spike protein were studied over time in patients with COVID-19. Possible associations between antibody titers and outcome were analyzed.

Results

Forty patients with COVID-19, hospitalized at Skåne University hospital, Sweden, between April and June 2020 were included. IgG antibody responses were detected for all patients with the highest levels four weeks after COVID-19 diagnosis. Levels of IgA were generally higher at diagnosis and decreased towards baseline 4 weeks after confirmed COVID-19. Patients with severe COVID-19 had higher levels of antibodies directed against SARS-CoV-2 spike protein compared with patients with mild disease.

Conclusion

IgG and IgA antibodies towards the spike protein follow different kinetics during COVID-19 and patients with severe disease develop higher antibody levels.