Consideration of noninherited maternal Ags as permissible HLA mismatches in cord blood donor selection.

In cord blood (CB) transplantation, virtual 6/6 HLA matches, whereby the donor-recipient mismatch is identical to the CB noninherited maternal Ag (NIMA), have similar outcomes to inherited 6/6 matches. In the UK-British Bone Marrow Registry (BBMR), 4707 of the total 21 020 CB donors have the NIMA defined. Retrospective searches of these donors, for 1-3 NIMA matches, identified a virtual 6/6 match for 31.4% of 274 European Caucasoid (EC) and 25.4% of 67 other ethnicity (OE) patients. Patients weighing ⩽50 kg were also evaluated for a single graft with adequate cell dose. In 125 EC patients, 6/6 HLA matches were identified for 24.0% and virtual 6/6 matches were identified for a further 21.6%. The remaining EC patients had a 5/6 (30.4%) or a 4/6 (22.4%) match. In OE patients, 6/6 HLA matches were identified for 9.3% and virtual 6/6 matches were identified for a further 18.7%. The remaining OE patients had a 5/6 (30.2%) or a 4/6 (37.2%) match. Searches were also performed using the 26 735 Bone Marrow Donors Worldwide CB with defined NIMA and yielded comparable increases. Considering NIMA as permissible mismatches in donor selection therefore increased the availability of a 6/6 match in this cohort.

Tolerance to penicillin in streptococci of viridans group.

Tolerance to penicillin was investigated in 40 isolates of optochin-resistant, alpha-haemolytic streptococci. Thirteen strains exhibited tolerance to penicillin (MBC:MIC ratio greater than or equal to 32) when stationary phase inocula were used, but only seven strains retained the tolerance phenotype in experiments with logarithmic phase inocula. There was a striking association between tolerance and Eagle's optimum dosage effect, particularly among strains that displayed tolerance in both the stationary and the logarithmic growth phases. Sequential viable counts on representative strains showed that reliance on the arbitrary criterion of bactericidal activity of 99.9% reduction of the original inoculum after 24 hours' exposure may occasionally lead to difficulties in the recognition of penicillin tolerance. In general, however, the 99.9% killing criterion provided a useful discriminator between strains that were rapidly killed by penicillin and those (tolerant strains) in which the bactericidal activity was much reduced.