Validity, reliability and minimum detectable change of the maximum step length test in people with stroke.

Stroke is a significant cause of deficits in balance, mobility and disability. Although tests of stepping speed are associated with balance performance after stroke, relationships between clinical tests of stepping distance and balance performance have not been investigated in people with stroke. A validated test of stepping distance and balance in older adults (the maximum step length [MSL] test), and two clinical measures associated with balance in people with stroke (the five-times-sit-to-stand test [FTSST] and gait speed) were evaluated in nineteen independent community-dwelling people with chronic stroke. There were strong relationships between MSL and performance on the clinical balance measures (Pearson's r 0.69 to -0.88), suggesting that MSL is a valid measure of balance after stroke. Test-retest reliability coefficients were excellent for the MSL tests (ICC both limbs; 0.98). Standard error of measurement expressed as a percentage of mean MSL was computed as 5.6% (hemiparetic leg) and 5.4% (unaffected leg), indicative of low levels of measurement error and excellent absolute reliability of the MSL test in people with stroke. Minimum detectable change expressed as a percentage of mean MSL was low (14.9% to 15.4%), suggesting that MSL may be sensitive to detecting change in physical performance in people with stroke. Advantages of the MSL test are that it is easy to administer, requiring minimal training, equipment, time or space. These advantages, together with the validity of the MSL test, its excellent test-retest and absolute reliability, and its low minimum change percent value suggest that MSL may be a useful measure of balance capabilities in people with stroke.

Regulation of virulence gene expression resulting from Streptococcus pneumoniae and nontypeable Haemophilus influenzae interactions in chronic disease.

Chronic rhinosinusitis (CRS) is a common inflammatory disease of the sinonasal cavity mediated, in part, by polymicrobial communities of bacteria. Recent molecular studies have confirmed the importance of Streptococcus pneumoniae and nontypeable Haemophilus influenzae (NTHi) in CRS. Here, we hypothesize that interaction between S. pneumoniae and NTHi mixed-species communities cause a change in bacterial virulence gene expression. We examined CRS as a model human disease to validate these polymicrobial interactions. Clinical strains of S. pneumoniae and NTHi were grown in mono- and co-culture in a standard biofilm assay. Reverse transcriptase real-time PCR (RTqPCR) was used to measure gene expression of key virulence factors. To validate these results, we investigated the presence of the bacterial RNA transcripts in excised human tissue from patients with CRS. Consequences of physical or chemical interactions between microbes were also investigated. Transcription of NTHi type IV pili was only expressed in co-culture in vitro, and expression could be detected ex vivo in diseased tissue. S. pneumoniae pyruvate oxidase was up-regulated in co-culture, while pneumolysin and pneumococcal adherence factor A were down-regulated. These results were confirmed in excised human CRS tissue. Gene expression was differentially regulated by physical contact and secreted factors. Overall, these data suggest that interactions between H. influenzae and S. pneumoniae involve physical and chemical mechanisms that influence virulence gene expression of mixed-species biofilm communities present in chronically diseased human tissue. These results extend previous studies of population-level virulence and provide novel insight into the importance of S. pneumoniae and NTHi in CRS.