Keith B. Armitage

Accessory function and properties of monocytes from healthy elderly humans for T lymphocyte responses to mitogen and antigen.

The waning of cell-mediated immunity during aging has been attributed primarily to defects in T lymphocyte properties and functions. We assessed the potential contribution of accessory dysfunction of monocytes from the elderly on responses of T cells to phytohemagglutinin (PHA) and to tetanus toxoid after in vivo boosting. Accessory function of monocytes from the elderly subjects for T lymphocyte responses to tetanus toxoid was comparable to the young. Expression of the cytokines interleukin-1, interleukin-6 and tumor necrosis factor, the cell adhesion molecules ICAM-1 and LFA-3 and the class II major histocompatibility molecule HLA-DR by monocytes from the elderly and young subjects was similar. T lymphocytes from the elderly responded poorly to PHA. Monocytes from the elderly had a decreased accessory function for PHA-stimulated T cells from young, third donors. Thus, although many accessory properties of monocytes from the elderly are normal, the monocyte and T lymphocyte defects in the elderly for mitogen may represent interactive factors in cell-mediated immunity during aging.

Does limiting fluoroquinolone use in the treatment of community-acquired infections prevent resistance among gram-negative rods?

We evaluated whether hospitals with routine fluoroquinolone (FQ) use for community-acquired infections have higher levels of gram-negative rod (GNR) resistance to FQs than hospitals that restrict their use. We obtained antibiogram data from six community hospitals (CHs) and tertiary care hospitals (THs), and calculated resistance rates among Klebsiella pneumoniae, Serratia marcescens, Escherichia coli, and Pseudomonas aeruginosa over time. We used pharmacy purchasing data to quantitate FQ use and compared resistance rates to use. Percentages of antibiotic costs related to FQs were lower at the THs (7.5%–12.5%) than at the CHs (21%–26%). There was a significant declining trend in the sensitivity of Pseudomonas to FQs at all THs and at CH 1 and CH 3 (p = .003–.039), despite less FQ use at the THs. E. coli isolates remained highly sensitive, and there were no significant trends for S. marcescens or K. pneumoniae. Without more judicious use of FQs in the outpatient setting, restrictions at individual hospitals may not slow resistance to FQs.