Localized adherence and attaching-effacing properties of nonenteropathogenic serotypes of Escherichia coli.

Traditional enteropathogenic Escherichia coli serotypes demonstrate a plasmid-mediated localized adherence in cultured HeLa or HEp-2 cells and induce an attaching-effacing intestinal lesion, both of which are considered pathognomonic and causes of diarrhea. This study describes three E. coli strains from infantile diarrhea which share these properties but belong to serotypes (O2:H2, O2:H25 and O15:H2) not considered enteropathogenic.     

Pathogenesis of Providencia alcalifaciens-induced diarrhea.

Providencia alcalifaciens is a member of the family Enterobacteriaceae. There are reports that P. alcalifaciens can cause diarrhea, but the mechanism(s) by which it causes diarrhea is known. We studied P. alcalifaciens isolated from a child and two adults with diarrhea for enteropathogenicity. The three isolates did not exhibit any characteristic adherence to cultured HEp-2 cell monolayers, and they did not produce enterotoxins, cytotoxins, or keratoconjunctivitis in the Sereny test. Two isolates invaded cultured HEp-2 cell monolayers, producing localized bacterial clusters and actin condensation. The pattern of actin condensation was different from that produced by enteropathogenic Escherichia coli but similar to that produced by Shigella flexneri. Invasion and actin condensation were poor for the third isolate. Histology of adult rabbit small intestinal loops inoculated with all three isolates revealed bacterial attachment to, penetration of, and microulcer formation on the surface epithelium and hyperemia, edema, and polymorphonuclear cell infiltration of lamina propria. All the isolates produced diarrhea in rabbits with removable intestinal ties, and some of these rabbits developed hindlimb paralysis. Intestinal histology of the rabbits with removable intestinal ties which developed diarrhea showed changes similar to that in adult rabbits on which ileal loop assays had been performed. Transmission electron microscopy of intestinal tissues also confirmed tissue penetration by the isolates. Nerve tissue histology of two rabbits that developed hindlimb paralysis showed focal mononuclear cell infiltration around peripheral nerve sheaths. It is concluded that some strains of P. alcalifaciens are enteropathogenic and that they cause diarrhea by invading the intestinal mucosal epithelium. However, the relevance to human disease of the hindlimb paralysis observed in this animal model is not clear.     

Genotypic analysis of Mycobacterium tuberculosis in Bangladesh and prevalence of the Beijing strain

Genotypic analysis was performed on 48 Mycobacterium tuberculosis complex strains collected from a hospital in Dhaka city. Deletion analysis showed that the isolates were all M. tuberculosis; 13 of them were found to be of the "ancestral" type, while 35 were of the "modern" type, indicating that both endemic (ancestral type) and epidemic (modern type) strains cause tuberculosis in Bangladesh. Genotyping based on the spoligotype and variable-number tandem repeats (VNTR) of mycobacterial interspersed repetitive units (MIRU) was also done. A total of 34 strains (71%) were grouped by spoligotyping into nine different clusters; the largest comprised 15 isolates of the Beijing genotype, whereas the remaining eight clusters consisted of two to five isolates. MIRU-VNTR typing detected 32 different patterns among 44 tested strains, and the 15 Beijing strains were further discriminated by MIRU-VNTR typing (7 distinct patterns for the 15 isolates). These results indicate that MIRU-VNTR typing, along with spoligotyping and deletion analysis, can be used effectively for molecular epidemiological studies to determine ongoing transmission clusters; to our knowledge, this is the first report about the type of strains prevailing in Bangladesh.     

Changes in the peripheral blood T-Cell receptor V beta repertoire in vivo and in vitro during shigellosis.

A sequential activation of T cells in peripheral blood during shigello sis has been observer (D. Islam, P.K. Bradham, A. A. Lindberg, and B. Christensson, Infect. Immun 63:2941-2949, 1995). To further investigate the cellular response during the course of Shigella infection, changes in the T-cell receptor (TCR) repertoire in the subsets in blood in patients during shigellosis was that Shigella antigens may modulate the function of T cells carrying TCRs capable of recognizing Shigella-specific epitopes or superantigens. Such a selective preference for T cells expressing certain TCR Vbeta types could lead to the expansion or deletion of these T cells. In the present study of 27 adult male Bangladeshi patients with dysentery (14 cases caused by Shigella Dysenteriae 1 and 13 cases caused by Shigella flexneri), the changes in the TCR Vbeta repertoire of peripheral blood CD4+ and CD8+ T-cell subsets have been analyzed with a panel of nine anti-Vbeta monoclonal antibodies by flow cytometry. Twenty healthy males from Bangladesh and 20 healthy males from Sweden served as controls. Compared with the Bangladeshi controls, the patients had an increased frequency of CD4+T cells expression Vbeta2, Vbeta3, and Vbeta17, with a maximum at day 7 after the onset of disease. The frequency of CD4+T cells expressing Vbeta5.1 was increased only in patients with S. flexneri infection. Peripheral blood T cells from Shigella-infected patients also responded to in vitro stimulation in a TCR Vbeta-specific manner. Stimulation with heat-killed S. dysenteriae 1 and Shiga toxin enhanced the frequency of cells expressing Vbeta2, Vbeta3, Vbeta5.1, Vbeta13.6, and Vbeta17, especially in samples obtained at day 7. The enhanced frequency of cells expressing Vbeta2, Vbeta3, Vbeta5.1, and Vbeta17 found both in in vivo and in vitro could suggest that in shigellosis antigens or superantigens are presented to the immune system and preferentially activate certain TCR Vbeta types in T-cell subsets. The kinetics of the change in the TCR Vbeta repertoire in blood during shigellosis may indicate that following local activation, the antigen activated T cells can be retrieved in the blood and restimulated in vitro. If confirmed by parallel analysis of T cells in the gut and blood by TCR sequence analysis, the possibility suggested by our findings would facilitate further analysis of the role of cell-mediated immune responses in the pathogenesis of and protection against Shigella infection.     

Antimicrobial susceptibilities and plasmid contents of Neisseria gonorrhoeae isolates from commercial sex workers in Dhaka, Bangladesh: emergence of high-level resistance to ciprofloxacin

Commercial sex workers (CSWs) serve as the most important reservoir of sexually transmitted diseases (STD), including gonorrhea. Periodic monitoring of the antimicrobial susceptibility profile of Neisseria gonorrhoeae in a high-risk population provides essential clues regarding the rapidly changing pattern of antimicrobial susceptibilities. A study concerning the prevalence of gonococcal infection among CSWs was conducted in Bangladesh. The isolates were examined with regards to their antimicrobial susceptibility to, and the MICs of, penicillin, tetracycline, ciprofloxacin, cefuroxime, ceftriaxone, and spectinomycin by disk diffusion and agar dilution methods. The total plasmid profile of the isolates was also analyzed. Of the 224 CSWs, 94 (42%) were culture positive for N. gonorrhoeae. There was a good correlation between the results of the disk diffusion and agar dilution methods. Some 66% of the isolates were resistant to penicillin, and 34% were moderately susceptible to penicillin. Among the resistant isolates, 23.4% were penicillinase-producing N. gonorrhoeae (PPNG). 60.6% of the isolates were resistant and 38.3% were moderately susceptible to tetracycline, 17.5% were tetracycline-resistant N. gonorrhoeae, 11.7% were resistant and 26.6% had reduced susceptibility to ciprofloxacin, 2.1% were resistant and 11.7% had reduced susceptibility to cefuroxime, and 1% were resistant to ceftriaxone. All PPNG isolates contained a 3.2-MDa African type of plasmid, and a 24.2-MDa conjugative plasmid was present in 34.1% of the isolates. Since quinolones such as ciprofloxacin are recommended as the first line of therapy for gonorrhea, the emergence of significant resistance to ciprofloxacin will limit the usefulness of this drug for treatment of gonorrhea in Bangladesh.     

Characterization of Aeromonas spp. isolated from humans with diarrhea, from healthy controls, and from surface water in Bangladesh.

Aeromonas isolates from patients with diarrhea in Bangladesh (n = 69), from healthy controls (n = 11), and from surface water (n = 40) were analyzed with respect to their hybridization groups (HGs) by the aid of fatty acid methyl ester (FAME) characterization and DNA fingerprinting by AFLP, biochemical phenotypes (Phe-nePlate [PhP] types), and the production of hemolysin and cytotoxin. The aim of the investigation was to find out whether certain strains carrying virulence factors predominated among patient isolates. According to FAME and/or AFLP analysis, most human isolates were allocated to DNA HGs 4 (Aeromonas caviae) and 1 (A. hydrophila). Most environmental strains were allocated to HG8 (A. veronii biogroup sobria) and HG4 (A. caviae), and only one was of HG1. According to PhP typing, the diversity among patient isolates was lower than that among other strains, and two dominating PhP types (types BD-1 and BD-2) were identified in 29 and 30% of the patient isolates, respectively. PhP type BD-1 was also common among the environmental isolates, whereas PhP type BD-2 was only identified in two of the other isolates. Twenty-five of 26 isolates belonging to HG1 were of the same PhP type (BD-2), whereas isolates of other common HGs were more diverse according to their PhP types. Hemolytic and cytotoxin-producing strains occurred more frequently among the environmental isolates than among patient isolates. However, the hemolytic and cytotoxic activities among human isolates was strongly correlated to the HG1/BD-2 type, which, in addition, showed high cytotoxin titers (median values, 1/512 compared to 1/128 for cytotoxin-positive isolates belonging to other types). Thus, the HG1/BD-2 type may represent a pathogenic A. hydrophila type that is able to produce diarrhea in humans.     

CD8 expression on B cells in chronic lymphocytic leukemia: a case report and review of the literature

The expression of CD8, a restricted T-cell antigen, on B cells in B chronic lymphocytic leukemia is rare, and its significance, if any, remains unknown. We report herein a patient with B chronic lymphocytic leukemia in whom CD8 was strongly expressed on all B cells, both in the bone marrow and peripheral blood. The patient required no therapy for 6 years after being diagnosed as having B chronic lymphocytic leukemia. Then, when the disease progressed, he was treated with conventional doses of fludarabine phosphate (25 mg/m(2) daily for 5 days), but unlike other patients with B chronic lymphocytic leukemia he tolerated this therapy poorly. He received a total of only 4 series of fludarabine therapy, and following each course of treatment, he developed considerable myelosuppression. After the fourth course of therapy, his bone marrow failed to show any evidence of regeneration, and he died as a result of intercurrent respiratory tract infection 1 month after his last dose of fludarabine was given.     

CD39 activity correlates with stage and inhibits platelet reactivity in chronic lymphocytic leukemia

Background  

Chronic lymphocytic leukemia (CLL) is characterized by accumulation of mature appearing lymphocytes and is rarely complicated by thrombosis. One possible explanation for the paucity of thrombotic events in these patients may be the presence of the ecto-nucleotidase CD39/NTDPase-1 on the surface of the malignant cells in CLL. CD39 is the major promoter of platelet inhibition in vivo via its metabolism of ADP to AMP. We hypothesize that if CD39 is observed on CLL cells, then patients with CLL may be relatively protected against platelet aggregation and recruitment and that CD39 may have other effects on CLL, including modulation of the disease, via its metabolism of ATP.     

The gene encoding CD23 leukocyte antigen (FCE2) is located on human chromosome 19

Using Southern blot analysis of DNAs from human×rodent cell hybrids, we have mapped the CD23 leukocyte antigen gene (FCE2) to human chromosome 19.