Persistent multiple pulmonary nodules in a nonimmunocompromised woman after varicella-related myelitis treated with acyclovir

Persistent multiple pulmonary nodules were observed on the chest X ray of a nonimmunocompromised woman 6 months after she was treated with acyclovir for a varicella-related myelitis without respiratory symptoms. Early antiviral therapy given for varicella infections might decrease the intensity of clinical symptoms without actually preventing the occurrence of varicella-zoster virus-related lesions such as the persistent pulmonary nodules reported here.     

Trichosporon beigelii, an emerging pathogen resistant to amphotericin B.

Trichosporon beigelii caused fatal disseminated infections that were resistant to amphotericin B in two granulocytopenic patients. In vitro susceptibility studies demonstrated that both index strains of T. beigelii were inhibited but not killed by amphotericin B at achievable concentrations in serum. The minimum lethal concentration for both isolates was greater than or equal to 18 micrograms/ml. Five of seven other isolates were found to have a similar pattern of amphotericin B resistance. The fact that the minimum lethal concentration of T. beigelii was many times greater than its MIC was consistent with a resistance pattern of tolerance. We concluded that T. beigelii may be resistant in vitro to amphotericin B and that this in vitro resistance was correlated with refractory, disseminated trichosporonosis in granulocytopenic patients. T. beigelii should be included in the expanding list of amphotericin B-resistant fungi.     

Characterisation of a subtype of colorectal cancer combining features of the suppressor and mild mutator pathways

BACKGROUND: 10% of sporadic colorectal cancers are characterised by a low level of microsatellite instability (MSI-L). These are not thought to differ substantially from microsatelite-stable (MSS) cancers, but MSI-L and MSS cancers are distinguished clinicopathologically and in their spectrum of genetic alterations from cancers showing high level microsatellite instability (MSI-H). AIMS: To study the distribution of molecular alterations in a series of colorectal cancers stratified by DNA microsatellite instability. METHODS: A subset of an unselected series of colorectal cancers was grouped by the finding of DNA MSI at 0 loci (MSS) (n = 51), 1-2 loci (MSI-L) (n = 38) and 3-6 loci (MSI-H) (n = 25). The frequency of K-ras mutation, loss of heterozygosity (LOH) at 5q, 17p and 18q, and patterns of p53 and beta catenin immunohistochemistry was determined in the three groups. RESULTS: MSI-H cancers had a low frequency of K-ras mutation (7%), LOH on chromosomes 5q (0%), 17p (0%) and 18q (12.5%), and a normal pattern of immunostaining for p53 and beta catenin. MSI-L cancers differed from MSS cancers in terms of a higher frequency of K-ras mutation (54% v 27%) (p = 0.01) and lower frequency of 5q LOH (23% v 48%) (p = 0.047). Whereas aberrant beta catenin expression and 5q LOH were concordant (both present or both absent) in 57% of MSS cancers, concordance was observed in only 20% of MSI-L cancers (p = 0.01). CONCLUSIONS: MSI-L colorectal cancers are distinct from both MSI-H and MSS cancers. This subset combines features of the suppressor and mutator pathways, may be more dependent on K-ras than on the APC gene in the early stages of neoplastic evolution, and a proportion may be related histogenetically to the serrated (hyperplastic) polyp.     

Coxsackievirus B3-Induced Myocarditis : Perforin Exacerbates Disease, But Plays No Detectable Role in Virus Clearance

Viral myocarditis is remarkably common, being detected in approximately 1% of unselected asymptomatic individuals. Many cases are attributable to enteroviral infection, and in particular to coxsackievirus B3. The underlying pathogenesis is controversial, but most studies admit the important immunopathological role of infiltrating CD8⁺ (cytotoxic) T lymphocytes (CTLs). We have previously shown that CTLs play conflicting roles in coxsackievirus B (CVB) myocarditis; they assist in controlling virus replication, but also are instrumental in causing the extensive inflammatory disease, which often results in severe myocardial scarring. A role for perforin, the major CTL cytolytic protein, in CVB myocarditis has been suggested, but never proven. In the present study we use perforin knockout (PKO) mice to show that perforin plays a major role in CVB infection; in broad terms, perforin is important in immunopathology, but not in CVB clearance. For example, PKO mice are better able to withstand a normally lethal dose of CVB (100% survival of PKO mice compared with 90% death in +/+ littermates). In addition, PKO mice given a nonlethal dose of CVB develop only a mild myocarditis, whereas their perforin⁺ littermates have extensive myocardial lesions. The myocarditis in PKO mice resolves more quickly, and these mice show minimal histological sequelae; in contrast, late in disease the perforin⁺ mice develop severe myocardial fibrosis. PKO mice, despite lacking this major CTL effector function, can control the infection and eradicate the virus; growth kinetics and peak CVB titers are indistinguishable in PKO and perforin⁺ mice. Therefore, the immunopathological and antiviral effects of CTLs can be uncoupled by ablation of perforin; this offers a promising target for therapy of myocarditis. Furthermore, we evaluate the possible roles of apoptosis, and of chemokine expression, in CVB infection. In perforin⁺ mice, apoptotic cells are detected within the inflammatory infiltrate, whereas in their PKO counterparts, apoptotic myocyte nuclei are seen. Chemokine expression in both PKO and perforin⁺ mice precedes and parallels the course of myocarditis. Several chemokines are detectable earlier in PKO mice than in perforin⁺ mice, but PKO mice show reduced peak levels, and chemokine expression decays sooner. In particular, MIP-1α expression is barely detectable at any time point in PKO mice, but it is readily identified in perforin⁺ animals, peaking just before the time of maximal myocarditis; this is particularly interesting, given that MIP-1α knockout mice are resistant to CVB myocarditis, but remain able to control viral infection. Thus, the chemokine pathway offers a second route of intervention to diminish myocarditis and its sequelae, while permitting the host to eradicate the virus.     

Involvement of K+ channels in the quercetin-induced inhibition of neuroblastoma cell growth

The effects of the flavonoid quercetin on cell proliferation and voltage-dependent K⁺ current were studied on mouse neuroblastoma×glioma hybrid cells. In the presence of 1 % fetal calf serum, quercetin inhibited both cell proliferation and K⁺ current with effective doses inducing half-maximum effects of 10 M and 70 M respectively. Valinomycin (1 nM) antagonized 80 % of the growth-inhibitory effects of 10 M quercetin. The results suggest that at least a part of the antiproliferative effect of quercetin is mediated by a K⁺ channel blockade. They further confirm a role for K⁺ channels in mitogenesis and cell proliferation.     

Molecular diagnosis of infective endocarditis by PCR amplification and direct sequencing of DNA from valve tissue

We used broad-range eubacterial PCR amplification followed by direct sequencing to identify microbial pathogens in heart valve material from 29 patients with histologically confirmed infective endocarditis and 23 patients free of infective endocarditis. Microorganisms cultured by conventional techniques matched those identified by PCR in 21 cases. PCR alone identified the causative agent in three cases (Streptococcus bovis, Staphylococcus cohnii, and Coxiella burnetii), allowing better patient management. PCR corrected the initial bacteriological diagnosis in three cases (Streptococcus bovis, Streptococcus mutans, and Bartonella henselae). Among the 29 cases of histologically confirmed infective endocarditis, PCR findings were positive in 27 cases and were consistent with the bacterial morphology seen at Gram staining (26 cases) or with the results obtained by immunohistologic analysis with an anti-C. burnetii monoclonal antibody (one case). In two other cases of histologically confirmed infective endocarditis, PCR remained negative in a blood culture-negative case for which no bacteria were seen at histological analysis and in one case with visualization of cocci and blood cultures positive for Enterococcus faecalis. Ten clinical diagnoses of possible infective endocarditis were ruled out by histopathological analysis of the valves and subsequently by PCR. PCR was negative in 13 of the 14 patients in whom infective endocarditis was rejected on clinical grounds; the other patient was found to have Coxiella burnetii infective endocarditis on the basis of PCR and histopathological analysis and was subsequently included in the group of 29 definite cases. In total, PCR contributed to the diagnosis and management of infective endocarditis in 6 of 29 (20%) cases.     

Contribution of the twin arginine translocation system to the virulence of enterohemorrhagic Escherichia coli O157:H7

Shiga toxin-producing Escherichia coli O157:H7 is a major food-borne infectious pathogen. In order to analyze the contribution of the twin arginine translocation (TAT) system to the virulence of E. coli O157:H7, we deleted the tatABC genes of the O157:H7 EDL933 reference strain. The mutant displayed attenuated toxicity on Vero cells and completely lost motility on soft agar plates. Further analyses revealed that the ΔtatABC mutation impaired the secretion of the Shiga toxin 1 (Stx1) and abolished the synthesis of H7 flagellin, which are two major known virulence factors of enterohemorrhagic E. coli O157:H7. Expression of the EDL933 stxAB₁ genes in E. coli K-12 conferred verotoxicity on this nonpathogenic strain. Remarkably, cytotoxicity assay and immunoblot analysis showed, for the first time, an accumulation of the holotoxin complex in the periplasm of the wild-type strain and that a much smaller amount of StxA₁ and reduced verotoxicity were detected in the ΔtatC mutant cells. Together, these results establish that the TAT system of E. coli O157:H7 is an important virulence determinant of this enterohemorrhagic pathogen.     

Actinomyces cardiffensis sp. nov. from human clinical sources

Eight strains of a previously undescribed catalase-negative Actinomyces-like bacterium were recovered from human clinical specimens. The morphological and biochemical characteristics of the isolates were consistent with their assignment to the genus Actinomyces, but they did not appear to correspond to any recognized species. 16S rRNA gene sequence analysis showed the organisms represent a hitherto unknown species within the genus Actinomyces related to, albeit distinct from, a group of species which includes Actinomyces turicensis and close relatives. Based on biochemical and molecular genetic evidence, it is proposed that the unknown isolates from human clinical sources be classified as a new species, Actinomyces cardiffensis sp. nov. The type strain of Actinomyces cardiffensis is CCUG 44997(T).     

Synthesis and function of the mitochondrial intron —encoded bI4 RNA maturase from Saccharomyces cerevisiae

Summary We have analyzed the expression and function of the intron-encoded bI4 maturase when frame-shift mutations in the upstream exon alter the translational process. By constructing secondary cis-acting mutations within the b14 intron, we observed (1) that the bI4 maturase is still translated in the presence of the upstream mutation, albeit in very low amounts, and (2) that the limited amounts of bI4 maturase made under these conditions is no longer able to promote the splicing process of the aI4 intron. These observations, which further strengthen the maturase model, strongly suggest that bI4 maturase acts sequentially on the bI4 intron and then on the aI4 intron.