Reviews of infectious diseases最新文献

Decision analysis was used in the evaluation of nine strategies for the prevention of neonatal infection with herpes simplex virus (HSV). These strategies involve physical examination at labor, weekly screening of pregnant women for shedding of HSV, use of serologic methods specific for HSV type 2, and performance of a rapid diagnostic test at labor. Rates of cesarean delivery and of neonatal infection with HSV were estimated for each strategy, and the estimates were compared with those for a strategy of no intervention. The effects of variations in the sensitivities and specificities of the diagnostic and serologic tests used were analyzed. Given the currently available data and technology, physical examination at labor is the optimal strategy if the primary goal is to minimize the ratio of excess cesarean sections to cases of neonatal HSV infection averted.

The occurrence of life-threatening infections, including cytomegalovirus (CMV) infection, in recipients of allogeneic bone marrow transplants is related to the severe and prolonged immunodeficiency that is present after transplantation. Studies performed in our laboratory of the recovery of CMV-specific T cell responses after bone marrow transplantation have demonstrated that CMV disease occurs exclusively in those patients with no reconstitution of CD8+ CMV-specific T cell responses. Methods of isolating class I major histocompatibility complex-restricted CD8+ CMV-specific T cell clones from healthy CMV-seropositive individuals with protective immunity have been developed. The majority of cytotoxic T cell clones isolated from several individuals recognize structural proteins of the virion that are presented by infected cells without requiring the expression of the viral gene. These results suggest this immunodominant response may be essential for maintaining the virus in a latent state in healthy CMV-seropositive individuals. Clinical trials have been initiated at our institution to investigate the potential for selective reconstitution of CMV-specific immunity in bone marrow transplant recipients by the adoptive transfer of CMV-specific T cell clones generated from the respective bone marrow donor.

Live attenuated Towne strain cytomegalovirus vaccine was evaluated in healthy volunteers and renal transplant recipients. Immunization induced humoral and cell-mediated immune responses in both groups, although responses were of a higher magnitude in healthy volunteers. Immunization of candidates for renal transplantation with Towne vaccine significantly reduced the incidence of moderately severe and severe cytomegalovirus disease in high-risk recipients after transplantation. Reactivation of vaccine-strain virus was not detected. While the use of live attenuated Towne strain vaccine for prevention of primary cytomegalovirus infections in solid-organ transplant recipients and pregnant women deserves further consideration, efforts are also under way to develop a subunit cytomegalovirus vaccine.

In vitro susceptibility testing is only one step in the evaluation of the potential efficacy of antimicrobial agents against the Bacteroides fragilis group. An assessment of in vivo efficacy, with a consideration of the factors that can best be studied in an infected host, is also an integral part of this process. Abscess models in rodents have been used to correlate in vitro activity with in vivo efficacy against this group of microorganisms. For metronidazole, clindamycin, moxalactam, and cefoxitin, the correlation was strong; for chloramphenicol and carbenicillin, it was not. In vivo studies of mixed infection with the B. fragilis group and Escherichia coli showed that cefoxitin and imipenem were effective; in contrast, cefotetan was not effective against resistant strains. Only strains susceptible to ceftizoxime in the agar dilution test were also affected by this drug in vivo. The so-called inoculum effect noted with ceftizoxime may explain this finding. In vivo elimination of encapsulated organisms of the B. fragilis group was found to be more difficult than elimination of unencapsulated isolates. The beta-lactamase produced by Bacteroides species can protect the enzyme-producing organism as well as its partners in mixed infections from the effects of beta-lactam antibiotics. These data illustrate the complexity and difficulties encountered when in vitro activity is correlated with in vivo efficacy.

The ecology of Cryptococcus neoformans and the epidemiology of cryptococcosis are reviewed. Two varieties of C. neoformans have been recognized. C. neoformans variety neoformans has been found in nature worldwide, primarily in association with bird droppings, although nonavian sources have also been found. Most cases of human cryptococcosis are caused by this variety. C. neoformans var. gattii has recently been isolated in nature in association with Eucalyptus trees. Infections caused by this variety occur mainly in tropical and subtropical regions. Because exposure to C. neoformans is probably common and clinically apparent cases of cryptococcosis in healthy hosts are rare, it is presumed that most people can mount adequate host defenses upon exposure to the organism. At least 5%-10% of patients with AIDS become infected with Cryptococcus; the epidemiology of this infection is different in many respects from that seen in patients without AIDS.