Characterization of a region of the IncHI2 plasmid R478 which protects Escherichia coli from toxic effects specified by components of the tellurite, phage, and colicin resistance cluster

The IncHI2 plasmid R478 specifies resistance to potassium tellurite (Te(r)), to some bacteriophages (Phi), and to pore-forming colicins (PacB). The genes encoding the three phenotypes are linked, and an 8.4-kb fragment of R478 DNA encoding them cannot be subcloned unless cocloned with a second section of the plasmid. Subclone pKFW4A contains a 5.9-kb BamHI-EcoRI fragment which caused some toxicity when present in Escherichia coli cells. Bacterial cells containing freshly transformed pKFW4A, examined by light microscopy and electron microscopy, had a filamentous morphology consistent with a block in septation. Insertion of transposon Tn1000 into terZ, -A, -B, and -C genes of pKFW4A resulted in the loss of the filamentation phenotype. Deletion of several regions of the clone confirmed that these latter components are involved in the filamentation phenotype. The region specifying protection from toxicity caused by the larger 8.4-kb fragment (encompassing this cluster and the entire 5.9-kb section of pKFW4A) was sequenced and analyzed by T7 polymerase expression and Tn1000 mutagenesis. Three open reading frames, terW, terY, and terX, were identified in a 2.6-kb region. Two polypeptides with approximate molecular masses of 18 and 28 kDa were expressed in CSRDE3 cells and were consistent with TerW (17.1 kDa; 155 amino acids [aa]) and TerY (26.9 kDa; 248 aa), whereas a protein of 213 aa deduced from terX was not observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The terX gene product shows strong identity with the previously identified TerE, TerD, and TerZ polypeptides, and there is a conserved motif of 13 residues, GDN(R/L)TG(E/A)GDGDDE, within this group of polypeptides. Complementation analysis indicated that terW, located approximately 6.0 kb upstream of terZ, brings about protection of cells from toxic effects of components of the Te(r), Phi, and PacB cluster.

Diagnostic difficulties caused by a nonclamped Schizophyllum commune isolate in a case of fungus ball of the lung

The presence of clamp connections on hyphae and the development of fruiting bodies in culture are primary characters which allow identification of the basidiomycete Schizophyllum commune in cases of human infection. The diagnostic problems presented by a nonclamped, nonfruiting isolate from a dense mass in the right upper lobe of the lung in a female with a past history of pulmonary tuberculosis and diabetes are described. Several features of the isolated fungus, including rapid growth rate and white, dense, cottony colonies, tolerance to the fungicide benomyl at a concentration of 10 micrograms/ml, and susceptibility to cycloheximide at 400 micrograms/ml, suggested that it might be a basidiomycete. Transmission electron microscopy showed the presence of a dolipore septum with perforate pore cap characteristic of fungi in the class Holobasidiomycetes. However, species identification remained elusive until compatibility tests with known single-basidiospore isolates confirmed the identification of the sterile lung isolate as S. commune. Sequence analysis of the 5' internal transcribed spacer region of ribosomal DNA further supported conspecificity.

Invasion of HeLa 229 cells by virulent Bordetella pertussis

Phase-dependent invasive behavior of Bordetella pertussis was demonstrated by recovery of viable organisms from gentamicin-treated HeLa cell monolayers and by transmission electron microscopy. Several mutants of B. pertussis with Tn5 or Tn5 lac inserted into various vir-regulated genes were evaluated for differences in their invasive abilities. Mutants lacking filamentous hemagglutinin, pertussis toxin, and two as yet uncharacterized vir-regulated products had levels of invasion significantly lower than that of the parent strain BP338. In contrast, invasion by mutants lacking adenylate cyclase toxin was significantly increased compared with that of wild-type B. pertussis. This increase in invasion was eliminated when concentrations of intracellular cyclic 3'-5' AMP were stimulated by treating HeLa cells with cholera toxin or forskolin. Entry of B. pertussis occurred through a microfilament-dependent phagocytic process, as evidenced by the marked reduction in uptake following treatment of HeLa cells with cytochalasin D. Invasion was inhibited with polyclonal anti-B. pertussis and anti-filamentous hemagglutinin antisera. In addition, a monoclonal antibody against lipooligosaccharide A reduced uptake by 65.5%. The preservation of HeLa cell integrity and the limited replication of intracellular bacteria suggest that invasion may represent a means by which B. pertussis evades an active host immune response.

Bordetella parapertussis invasion of HeLa 229 cells and human respiratory epithelial cells in primary culture

Bordetella parapertussis, a respiratory tract pathogen commonly regarded as noninvasive, was found to invade HeLa 229 cell monolayers. Following treatment of the monolayers with gentamicin, numbers of viable B. parapertussis recovered were comparable to those of invasive Salmonella and Shigella isolates. Invasion occurs through a cytochalasin-sensitive process which appears to be distinct from receptor-mediated endocytosis. Hyperimmune antisera raised against filaments hemagglutinin, a major adhesion of B. pertussis, did not inhibit invasion by B. parapertussis, suggesting that alternate adhesin(s) are required for invasion. In addition, B. parapertussis was found to invade human respiratory epithelial cells in primary culture, as demonstrated in ultrathin sections viewed by transmission electron microscopy. Although viable intracellular B. parapertussis persist within HeLa cells, they do not multiply there and the monolayers remain intact, suggesting a possible mechanism of carriage for these organisms.