Previous studies have reported that infection of monocytes by viruses such as cytomegalovirus and human immunodeficiency virus weakens host natural immunity. In the present study, we demonstrated the capability of Epstein-Barr virus (EBV) to infect and replicate in freshly isolated human monocytes. Using electron microscopy analysis, we observed the presence of EBV virions in the cytoplasm and nuclei of approximately 20% of monocytes. This was confirmed by Southern blot analysis of EBV genomic DNA sequences in isolated nuclei from monocytes. Infection of monocytes by EBV leads to the activation of the replicative cycle. This was supported by the detection of immediate-early lytic mRNA BZLF-1 transcripts, and by the presence of two early lytic transcripts (BALF-2, which appears to function in DNA replication, and BHRF-1, also associated with the replicative cycle). The late lytic BcLF-1 transcripts, which code for the major nucleocapsid protein, were also detected, as well as EBNA-1 transcripts. However, attempts to detect EBNA-2 transcripts have yielded negative results. Viral replication was also confirmed by the release of newly synthesized infectious viral particles in supernatants of EBV-infected monocytes. EBV-infected monocytes were found to have significantly reduced phagocytic activity, as evaluated by the quantification of ingested carboxylated fluoresceinated latex beads. Taken together, our results suggest that EBV infection of monocytes and alteration of their biological functions might represent a new mechanism to disrupt the immune response and promote viral propagation during the early stages of infection. Epstein-Barr virus (EBV), a member of theHerpesviridae family, has long demonstrated its capabilities to adapt and evade host defense mechanisms. While it was mainly believed that EBV infects only B cells and epithelial cells of the oropharynx, there is growing evidence that EBV targeted cells are broader than initially believed. In fact, recent studies have demonstrated that EBV can infect thymocytes, as revealed by the detection of BZLF-1 and EBV nuclear antigen (EBNA)-1

A study recently conducted across Canada showed that 64 of 2,503 clinical isolates of Haemophilus influenzae were resistant to beta-lactams without production of a beta-lactamase (L. D. Tremblay, J. L'Ecuyer, P. Provencher, M. G. Bergeron, and Canadian Study Group, Can. Med. Assoc. J. 143:895-900, 1990). The beta-lactamase-negative strains formed three distinct groups, with ampicillin MICs of 0.5 to 1, 2 to 4, and greater than or equal to 8 micrograms/ml for groups I, II, and III, respectively. We have investigated the mechanisms of resistance for eight strains originating from different infections and geographic areas. These strains were representative of groups I to III. Five strains were nontypeable, two were type B, and one was non-B. Chromosomal DNA extracted from each strain was used to transform the laboratory strain Rd. Transformants were selected on beta-lactam-containing plates and showed the same level of resistance to ampicillin as the donor strains. Differences in outer membrane proteins, porins, and lipopolysaccharide profiles on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) did not change with resistance. Functional analyses of purified porins in artificial lipid bilayer experiments did not explain resistance. Peptidoglycan synthesis was measured by incorporation of [14C]alanine into trichloroacetic acid-insoluble cell wall material in the presence of chloramphenicol. The growth rate and the rate of peptidoglycan synthesis observed for the transformants of the isogenic set did not correlate with resistance. Whole-cell labeling with 125I-penicillin revealed modifications in penicillin-binding proteins (PBPs) among the transformants. In particular, PBPs 3A and 3B (65 and 63 kDa, respectively) showed a decrease in affinity for beta-lactams in all transformants (groups I, II, and III) and correlated with an increased MIC except in the transformant of group III, which showed higher levels of resistance. Partial purification and proteolytic digestion of 125I-penicillin-labeled PBP 3B led to two types of CnBr peptide profiles on SDS-PAGE, the profiles of the transformed strains from groups I and II being different from those of the control group and group III. Finally, electron microscopy revealed a distinct cell filamentation for the group III transformants. These data clearly indicate that changes in PBPs are a common mechanism that results in a significant level of non-beta-lactamase-mediated beta-lactam resistance in H. influenzae despite serotype, origin of isolation, or geographic distribution.

The subcellular distribution of gentamicin in rat renal proximal tubular cells was evaluated by immunogold labeling. The distribution of the drug was monitored from 10 min to 10 days following single (40 mg/kg of body weight) and multiple (5 and 20 mg/kg/12 h) injections of gentamicin. Animals were killed on day 11, and cubes of renal cortex tissue were fixed overnight in cold phosphate-buffered glutaraldehyde (0.5%), dehydrated in ethanol, and embedded in Araldite 502 epoxy resin. Ultrathin sections were made and incubated with sheep antigentamicin and then with protein A-gold (15 nm) complex. At 10 min after a single injection, the labeling was found over the brush border membrane and over the membranes of endocytic apical vesicles of proximal tubular cells. After 1 h, a similar distribution was observed and the labeling was also seen over small lysosomes located close to the brush border membrane. At 24 h, gold particles were found over large lysosomes of proximal tubular cells. Following 10 days of treatment, lysosomes of proximal tubular cells were densely labeled with gold particles. The labeling was distributed uniformly over the lysosomes, although a lower density of labeling was observed over the myeloid bodies inside the lysosomes. Necrotic proximal tubular cells showed labeling over intact lysosomes and also in the cytoplasms of the cells, in the mitochondria, and in the nucleoli. The various control experiments demonstrated the high specificity of these results. The present immunocytochemical study better documents the subcellular disposition of gentamicim in proximal tubular cells, as previously evaluated by subcellular fractionation and autoradiography. This technique will be useful for better understanding the relationship between drug disposition and drug-induced toxicity.The nephrotoxicity of aminoglycosides has been extensively investigated, but the mechanism by which these drugs induce cellular disturbances and necrosis remains to be elucidated. These drugs, which are essentially eliminated by glomerular filtration, are partially reabsorbed by proximal tubular cells (15). They concentrate into lysosomes (7), where they induce a lysosomal phospholipidosis (9) characterized by the appearance of myeloid bodies (8).The incorporation of aminoglycosides within the lysosomes of renal cortical cells has been demonstrated by subcellular fractionation (16). The binding of aminoglycosides to brush border membranes and their subsequent accumulation into lysosomes of proximal tubular cells have been previously shown by autoradiography (3, 15). Moreover, Giurgea-Marion et al. (7), by using subcellular fractionation, have observed that gentamicin remains associated with the lysosomes of proximal tubular cells throughout a 9-day treatment.The objective of the present study was

Daptomycin is a new biosynthetic antibiotic which belongs to a new class of drugs known as lipopeptides. The objective of this study was to evaluate the effects of daptomycin and vancomycin on tobramycin-induced nephrotoxicity. Female Sprague-Dawley rats were treated during 4 and 10 days with either saline (NaCl, 0.9%) or tobramycin at doses of 4 and 40 mg/kg per day (given every 12 h [ql2h] intraperitoneally). Each treatment was combined with saline, daptomycin at a dose of 20 mg/kg per day (given ql2h subcutaneously), and vancomycin at a dose of 50 mg/kg per day (given ql2h subcutaneously). Daptomycin and vancomycin had no effect on the intracortical accumulation of tobramycin. The nephrotoxicity of aminoglycosides has been intensively studied, but there are limited data on the mechanism of vancomycin toxicity. The nephrotoxicity of vancomycin given alone has been demonstrated in animals by using sensitive parameters of nephrotoxicity (22). It has also been shown in both human (11,32) and animal (22,23,36,38) studies with different animal strains and drug doses that nephrotoxicity is increased when vancomycin and an aminoglycoside are injected concomitantly. However, this phenomenon is not reproduced in pediatric populations (27,33). Moreover, it has also been observed that vancomycin and aminoglycosides accumulate within the renal cortices of experimental animals (22,23,38

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