Specific and rapid detection by fluorescent in situ hybridization of bacteria in clinical samples obtained from cystic fibrosis patients

We report on the rapid and specific detection of bacteria commonly isolated from clinical specimens from cystic fibrosis (CF) patients by fluorescent in situ hybridization (FISH). On the basis of comparative sequence analysis, we designed oligonucleotide probes complementary to species-specific 16S rRNA regions of these microorganisms and demonstrated the specificities of the probes by hybridization of different remotely related as well as closely related reference strains. Furthermore, in a pilot project we investigated 75 sputum samples and 10 throat swab specimens from CF patients by FISH and detected Pseudomonas aeruginosa, Burkholderia cepacia, Stenotrophomonas maltophilia, Haemophilus influenzae, and Staphylococcus aureus within these specimens. The specificity of FISH was 100% in comparison to the results of conventional microbial culture. In contrast, the sensitivity of standard laboratory cultivation was moderately higher, since the limit for microscopic detection of bacteria within sputum samples by FISH was approximately 4 x 10(5) CFU/ml of sputum (resulting in a 90% sensitivity for FISH). Moreover, we demonstrated that FISH will be useful for the rapid detection of bacteria that cause acute pulmonary exacerbations in CF patients, as demonstrated in patients with H. influenzae, S. aureus, and P. aeruginosa exacerbations. Therefore, FISH is a valuable additional method for the rapid and specific detection of bacteria in clinical samples from CF patients, in particular, patients with pulmonary exacerbations.

Chronic prosthetic hip infection caused by a small-colony variant of Escherichia coli

From two different specimens of a chronic prosthetic hip infection taken at an interval of 2 months a slow-growing gram-negative bacterium was isolated in pure culture. The strain grew with the typical features of a small-colony variant (SCV). 16S rRNA sequencing identified the bacterium as Escherichia coli. Biochemical characterization demonstrated multiple phenotypic alterations of a mutant carrying a defect in the heme biosynthetic pathway (Hem-): (i) catalase and nitrate reductase reactions were both negative, (ii) a negative benzidine reaction demonstrated the lack of heme-containing cytochromes, and (iii) growth stimulation under anaerobic conditions as well as gentamicin resistance indicated defective aerobic respiration. PCR and Southern hybridization demonstrated that the mutation of the SCV of E. coli was localized in the hemB gene and was most likely due to a deletion of the hemB gene. On blood agar plates revertants were recognized growing as normal-sized colonies between the dominant small colonies of the strain. Feeding experiments indicated that the revertants but not the small colonies were permeable for hemin. A strong antibody response against the infecting SCV of E. coli was found. To our knowledge, this is the first report of a Hem- E. coli strain as the etiological agent of a chronic bacterial infection.

Epstein-Barr viral gene expression in B-lymphocytes

The strategy of the Epstein-Barr virus to persist lifelong in the host depends on establishing a reservoir, which cannot be detected by the immune system but allows reactivation of the virus for shedding and transmission to a new host. Epithelial cells and B-cells play a major role in this viral strategy of EBV, since differentiating epithelial tissues were shown to be permissive for lytic replication in vivo, whereas the B-lymphocytes become predominantly latently infected. However, which cells are the reservoir and which the sites of lytic replication are not quite clear. With the technique of reverse transcription, PCR and immunohistochemistry, we demonstrated that the B-cells of the peripheral blood are a major site of virus production during the primary infection during infectious mononucleosis. These permissive B-cells were also detected after convalescence, however, the absence of any lytic transcripts suggested an efficient immunological control very early in the viral lytic cycle. Serological data on reactivation of EBV correlated with the detection of lytic cycle transcripts in the blood and thus demonstrated that the site of virus production during infectious mononucleosis must be different from that of the persistent state. In those cases, where the infection takes a chronic active course, control of lytic replication is insufficient, either on the level of immune surveillance or of viral gene regulation. We have demonstrated a virus strain with a lytic phenotype in an individual suffering chronic active infection. The impaired capability of this virus to immortalise B-cells correlated with an enhanced expression of the lytic switch gene BZLF-1 and down-regulation of latent regulatory genes in the early phase of infection.

Yersinia enterocolitica impairs activation of transcription factor NF-kappaB: involvement in the induction of programmed cell death and in the suppression of the macrophage tumor necrosis factor alpha production

In this study, we investigated the activity of transcription factor NF-kappaB in macrophages infected with Yersinia enterocolitica. Although triggering initially a weak NF-kappaB signal, Y. enterocolitica inhibited NF-kappaB activation in murine J774A.1 and peritoneal macrophages within 60 to 90 min. Simultaneously, Y. enterocolitica prevented prolonged degradation of the inhibitory proteins IkappaB-alpha and IkappaB-beta observed by treatment with lipopolysaccharide (LPS) or nonvirulent, plasmid-cured yersiniae. Analysis of different Y. enterocolitica mutants revealed a striking correlation between the abilities of these strains to inhibit NF-kappaB and to suppress the tumor necrosis factor alpha (TNF-alpha) production as well as to trigger macrophage apoptosis. When NF-kappaB activation was prevented by the proteasome inhibitor MG-132, nonvirulent yersiniae as well as LPS became able to trigger J774A.1 cell apoptosis and inhibition of the TNF-alpha secretion. Y. enterocolitica also impaired the activity of NF-kappaB in epithelial HeLa cells. Although neither Y. enterocolitica nor TNF-alpha could induce HeLa cell apoptosis alone, TNF-alpha provoked apoptosis when activation of NF-kappaB was inhibited by Yersinia infection or by the proteasome inhibitor MG-132. Together, these data demonstrate that Y. enterocolitica suppresses cellular activation of NF-kappaB, which inhibits TNF-alpha release and triggers apoptosis in macrophages. Our results also suggest that Yersinia infection confers susceptibility to programmed cell death to other cell types, provided that the appropriate death signal is delivered.

Determination of the number of Epstein-Barr virus genomes in whole blood and red cell concentrates

The risk of Epstein-Barr virus (EBV) infection after blood transfusion has been controversially discussed. Little is known about EBV transmission via buffy-coat-depleted red cell concentrates (RCC). In this study, we determined the number of EBV genomes in RCC of EBV-seropositive donors in comparison to whole blood. RCC were prepared from whole blood donations by using the 'top and bottom system'. Leucocyte content was significantly reduced in RCC in comparison to whole blood (0.47 x 10(9) vs. 2.3 x 10(9) per unit; P < 0.001). As B cells are expected to harbour EBV genomes, we analysed the number of B lymphocytes in both types of blood products. There was a significant reduction of B cell content from a median value of 90 x 10(6) in whole blood to 0.2 x 10(6) in RCCs (P < 0.001). The number of EBV genomes was estimated at a median value of seven from 10(6) B cells in the peripheral blood of healthy, EBV-seropositive blood donors by means of a polymerase chain reaction (PCR) assay. By calculation, one unit of RCC may contain an average of one to two EBV genomes, in contrast to a whole blood unit, which is likely to harbour an average of 600 to 700 EBV genomes. It is concluded that the use of leucocyte depletion systems significantly reduces the number of EBV genomes in erythrocyte concentrates. Thus, leucocyte reduced blood products appear to minimize the risk of EBV infection.

Characteristics of viral protein expression by Epstein-Barr virus-infected B cells in peripheral blood of patients with infectious mononucleosis

The frequency of Epstein-Barr virus (EBV) antigen-positive B cells in the peripheral blood of patients with infectious mononucleosis compared with that for latently EBV-infected individuals was examined by immunocytochemistry. B cells positive for Epstein-Barr nuclear antigen (EBNA) 1, EBNA2, and latent membrane protein were frequently found in all peripheral B lymphocyte preparations from 25 patients suffering for 3 to 28 days from infectious mononucleosis by using monoclonal antibodies and the alkaline phosphatase anti-alkaline technique. There was a significant decrease in the number of positive B cells during the course of disease. EBNA1-positive B cells were detected in 0.01 to 2.5% of total B cells (median, 0.8%), EBNA2-positive B cells were detected in 0.01 to 4.5% of total B cells (median, 0.9%), and latent membrane protein-positive B cells were detected in 0.01 to 1.8% of total B cells (median, 0.5%), depending on the duration of clinical signs. In contrast, we did not find any EBNA1- or EBNA2-positive B cells in 2 x 10(6) peripheral blood B lymphocytes of 10 latently EBV-infected individuals, whereas aliquots of the same cell preparations were EBV DNA positive by a PCR assay. Therefore, it appears to be possible to detect infectious mononucleosis by immunocytochemical determination of latent EBV products, which might be of relevance for the diagnosis of EBV reactivations in immunosuppressed patients.

Sex difference in the serostatus of adults to the Epstein-Barr virus

A total of 1047 adults, aged between 18 and 90 years, including blood donors and surgical patients of the Medical University of Lübeck in Germany, were screened for IgG antibodies to the Epstein-Barr Virus, either by standard indirect immunofluorescence or by a novel enzyme-linked immunosorbent assay (Enzygnost Anti-EBV/IgG, Behring, Marburg, Germany). There was a significant sex difference in the serostatus to the Epstein-Barr virus in adults. Male adults were more likely than females (p < 1%) to be EBV-seronegative. The same trend was seen in both a group of 713 blood donors and 334 surgical patients and when different test methods were used. However, this sex difference was not shown in the sera of 86 pediatric patients of the Medical University of Lübeck tested by indirect immunofluorescence for IgG antibodies to the Epstein-Barr virus. Furthermore, titers of IgG antibodies to Epstein-Barr virus specific antigens of female adults, obtained by the enzyme-linked immunosorbent assay (Enzygnost Anti-EBV/IgG), had significantly higher median values than male adults (p < 5%).