The West: slowing, but still strong

Federal Reserve District, 12th

Significance of Extravascular Protein Binding for Antimicrobial Pharmacodynamics in an In Vitro Capillary Model of Infection

The effect of protein binding in an extravascular space on antimicrobial pharmacodynamics was studied in an in vitro capillary model of infection. Simulated 500-mg oral doses of dicloxacillin (~ 96% bound) or cephalexin (\u3c 5% bound) were administered every 6 h for four doses. A 10-fold-higher dose of dicloxacillin was also studied to determine the effect of drug concentration on the reduction of bacterial killing in the presence of protein. Staphylococcus aureus ATCC 25923 was inoculated into peripheral chambers filled with either Mueller-Hinton broth or Mueller-Hinton broth plus 25% human serum. Serial samples for bacterial counts were collected over 24 h. The presence of serum in the chambers significantly reduced bacterial killing by dicloxacillin but not by cephalexin during the first 6 h (two-way analysis of variance, F = 6.04, P \u3c 0.05) but not at 24 h. Reduction of dicloxacillin activity in serum-containing chambers persisted with the higher dose. These data suggest that despite attaining higher total drug concentrations in protein-containing extravascular spaces with highly bound drugs, protein binding reduces bactericidal activity during the early stages of treatment in this model

Combination Therapy with Ciprofloxacin plus Azlocillin against Pseudomonas aeruginosa: Effect of Simultaneous versus Staggered Administration in an In Vitro Model of Infection

The effect of dose scheduling on the pharmacodynamics of simulated human doses of ciprofloxacin (200 mg intravenously [iv] every 12 h) and azlocillin (4 g iv every 12 h) alone or in combination against Pseudomonas aeruginosa was studied in a two-compartment in vitro kinetic model of infection. Studies with the two drugs in combination were compared using simultaneous or staggered (first doses of each drug were administered 6 h apart) dosing schedules. Bacterial regrowth and resistance were prevented by all combination dosing schedules; however, the simultaneous regimen consistently provided the greatest extent of killing for all strains, particularly in those initially resistant to ciprofloxacin. These enhanced effects of the combination were corroborated by an increase in the peak and duration of bactericidal activity in the analogous "serum” compartment of the model. These data show the potential usefulness of simultaneous dosing of an antipseudomonal µ-lactam with ciprofloxacin against P. aeruginos

The Hand of Cercopithecoides williamsi (Mammalia, Primates): Earliest Evidence for Thumb Reduction among Colobine Monkeys

Thumb reduction is among the most important features distinguishing the African and Asian colobines from each other and from other Old World monkeys. In this study we demonstrate that the partial skeleton KNM-ER 4420 from Koobi Fora, Kenya, dated to 1.9 Ma and assigned to the Plio-Pleistocene colobine species Cercopithecoides williamsi, shows marked reduction of its first metacarpal relative to the medial metacarpals. Thus, KNM-ER 4420 is the first documented occurrence of cercopithecid pollical reduction in the fossil record. In the size of its first metacarpal relative to the medial metacarpals, C. williamsi is similar to extant African colobines, but different from cercopithecines, extant Asian colobines and the Late Miocene colobines Microcolobus and Mesopithecus. This feature clearly links the genus Cercopithecoides with the extant African colobine clade and makes it the first definitive African colobine in the fossil record. The postcranial adaptations to terrestriality in Cercopithecoides are most likely secondary, while ancestral colobinans (and colobines) were arboreal. Finally, the absence of any evidence for pollical reduction in Mesopithecus implies either independent thumb reduction in African and Asian colobines or multiple colobine dispersal events out of Africa. Based on the available evidence, we consider the first scenario more likely

Fragment screening reveals salicylic hydroxamic acid as an inhibitor of <em>Trypanosoma brucei</em> GPI GlcNAc-PI de-N-acetylase

The zinc-metalloenzyme GlcNAc-PI de-N-acetylase is essential for the biosynthesis of mature GPI anchors and has been genetically validated in the bloodstream form of Trypanosoma brucei, which causes African sleeping sickness. We screened a focused library of zinc-binding fragments and identified salicylic hydroxamic acid as a GlcNAc-PI de-N-acetylase inhibitor with high ligand efficiency. This is the first small molecule inhibitor reported for the trypanosome GPI pathway. Investigating the structure activity relationship revealed that hydroxamic acid and 2-OH are essential for potency, and that substitution is tolerated at the 4- and 5-positions