METHODS: In total, 7541 organisms causing documented infections were consecutively collected in 66 centres in 33 countries, excluding the USA. Susceptibility testing was performed by broth microdilution. Isolates displaying linezolid MIC results of ≥4 mg/L were molecularly characterized.
RESULTS: Linezolid inhibited all Staphylococcus aureus at ≤2 mg/L, with MIC50 results of 1 mg/L, regardless of methicillin resistance. A similar linezolid MIC50 result (i.e. 0.5 mg/L) was observed against CoNS, with the vast majority of isolates (99.4%) also inhibited at ≤2 mg/L. Six CoNS that exhibited elevated linezolid MIC values were found to contain alterations in the 23S rRNA and/or L3 ribosomal protein. Linezolid exhibited consistent modal MIC and MIC50 results (1 mg/L) against enterococci, regardless of species or vancomycin resistance. Three Enterococcus faecalis from Galway and Dublin (Ireland) and Kelantan (Malaysia) showed MIC results of 4 to 8 mg/L and carried optrA. All Streptococcus pneumoniae, viridans-group streptococci and β-haemolytic streptococci were inhibited by linezolid at ≤2, ≤2 and ≤1 mg/L, respectively, with equivalent MIC90 results (1 mg/L for all groups).
CONCLUSIONS: These results document the continued long-term and stable in vitro potency of linezolid and reveal a limited number of isolates with decreased susceptibility to linezolid (i.e. MIC ≥4 mg/L). The latter isolates primarily showed mutations in the 23S rRNA gene and/or L3 protein, but cfr was not detected. Moreover, this study shows that isolates carrying the newly described ABC transporter optrA are not restricted to China.
METHODS: MEDLINE, EMBASE, PubMed, Web of Science, and ProQuest were searched. Studies were included if participants were more than 60 years, were set within the community or within long-term care and diagnosis was based on a postural drop in systolic blood pressure (BP) ≥20 mmHg or diastolic BP ≥10 mmHg. Data were extracted independently by two reviewers. Random and quality effects models were used for pooled analysis.
RESULTS: Of 23,090 identified records, 20 studies were included for community-dwelling older people (n = 24,967) and six were included for older people in long-term settings (n = 2,694). There was substantial variation in methods used to identify OH with differing supine rest duration, frequency and timing of standing BP, measurement device, use of standing and tilt-tables and interpretation of the diagnostic drop in BP. The pooled prevalence of OH in community-dwelling older people was 22.2% (95% CI = 17, 28) and 23.9% (95% CI = 18.2, 30.1) in long-term settings. There was significant heterogeneity in both pooled results (I2 > 90%).
CONCLUSIONS: OH is very common, affecting one in five community-dwelling older people and almost one in four older people in long-term care. There is great variability in methods used to identify OH.