The swimming velocities of two monotrichous flagellated bacteria were measured by a computer-assisted video tracking method. Tracing the moving path of the individual bacterium revealed that the bacterial cell did not swim continuously in a straight direction, but frequently changed swimming direction and velocity. The average swimming velocities calculated from the 3-sec path were 75.4±9.4μm/sec in four strains of Vibrio cholerae and 51.3±8.4μm/sec in five strains of Pseudomonas aeruginosa. These results suggest that V. cholerae swim faster than P. aeruginosa at 30C in nutrient broth. This method is useful for a detailed analysis of bacterial movement and moving patterns in different environmental conditions.

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Using pulsed field gel electrophoresis (PFGE) and Southern hybridization techniques, a physical map of Moraxella catarrhalis strain ATCC25238 was constructed to provide basic genetic knowledge of this bacterium that has attracted attention in recent years as a human pathogen. Restriction endonuclease NotI cut the genome into 10 fragments and SmaI into 9, and the molecular size of the genome was estimated to be 1, 940 kilobases. Location of the 12 genes participating in the biosynthesis of purine, pyrimidine and nine kinds of amino acids were determined on the circular physical map of the strain.

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The initial adhesion of microbes to tissue and solid surfaces can be mediated by hydrophobic interaction. Expression of microbial cell surface hydrophobicity (CSH) is influenced by growth conditions, and often best expressed after growth under nutrient-poor conditions, or “starvation.” In the present study, the CSH of 133 strains of Enterobacteriaceae, Staphylococcus aureus, coagulase-negative staphylococci, Enterococcus faecalis, group A streptococcus, Pseudomonas aeruginosa, Clostridium perfringens, Bacteroides fragilis, Peptococcus magnus, and of 8 Candida albicans strains was measured by the salt aggregation test after growth on hematin agar in a 5% CO₂ atmosphere, or under anaerobiosis. Cells of all but 8 strains expressed pronounced or moderate CSH, i.e., they aggregated in 0.01-2M ammonium sulfate. When the agar surface was covered by human serum (diluted 1:5) to mimic growth conditions in a wound, 94 strains expressed higher CSH, and 44 strains the same CSH as after growth without serum. The CSH of 12 strains of different species was measured after growth on blood, hematin and PDM agar, with or without serum, and in an aerobic or a 5% CO₂ atmosphere. The highest CSH was expressed after growth in 5% CO₂ with serum, and the lowest growth after on blood agar in aerobic atmosphere. Identical results were obtained with native and heat-inactivated (56C, 20min) serum. The reduced surface tension obtained in 5% CO₂, as well as yet unidentified serum factors, promotes expression of CSH.

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Under iron-restricted conditions, Vibrio parahaemolyticus produces a siderophore, vibrioferrin, accompanying expression of two major outer membrane proteins of 78 and 83kDa. Autoradiographic analysis of nondenaturing polyacrylamide gel electrophoregrams of outer membrane preparations previously incubated with [⁵⁵Fe]ferric vibrioferrin revealed a single radiolabeled band, in which the 78-kDa protein was detected predominantly by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The antiserum against the purified 78-kDa protein partially inhibited Fe-VF binding to isolated OMPs. The 78-kDa protein was cleaved by the treatment of whole cells with proteinase K, indicating that a portion of this protein is exposed on the surface of the outer membrane. The treated cells lost most of their iron uptake activity mediated by vibrioferrin. These results suggest that the ferric vibrioferrin-binding protein of 78kDa may function as the receptor for ferric vibrioferrin involved in the initial step of vibrioferrin-mediated iron uptake. Immunoblot analysis using the antiserum against the 78-kDa protein demonstrated that the molecular mass and antigenic properties of the protein were highly conserved among V. parahaemolyticus strains examined. The antiserum also recognized an iron-repressible outer membrane protein of 78kDa from iron-restricted V. alginolyticus strains, some of which appeared to produce vibrioferrin.

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The neurotoxin associated with type A infant botulism in Japan shows different antigenic properties from those produced by authentic strains. The monoclonal antibodies recognizing the light chain reacted to both neurotoxins, whereas half the antibodies recognizing the heavy chain reacted specifically to the respective neurotoxin. Each neurotoxin showed its own manner of binding to brain synaptosomes. These results indicate that the distinguishable characteristics are ascribable to the heavy chain but not to the light chain. In both neurotoxins, an epitope recognized by the monoclonal antibody that reacts to the light chain and neutralizes the toxin was found to be very close to the amino-terminal half (H-1 fragment) of the heavy chain. This may support the hypothesis that the H-1 fragment functions in the transport of the light chain in the target cell.

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We investigated the murine antibody response to recombinant p17 (rp17) of human immunodeficiency virus type 1 (HIV-1) and the human antibody response directed to p17 in HIV-1 infection. Three large peptides covering residues 12-29, 53-87 and 87-115 of p17 were synthesized. The cysteine residues 57 and 87 of peptide 53-87 were reoxidized to form a disulfide bridge. Eighteen out of 19 murine monoclonal anti-rp17 antibodies had relatively high affinities (K_A=1.9×10⁵-1.4×10⁸M^-1) with one of the 3 p17 peptides in the liquid phase. Each monoclonal antibody reacted only with one particular peptide and had no reactivity with the other 2 p17 peptides. All the monoclonal antibodies reacted with rp17 in the liquid phase with a reasonable degree of affinity (K_A=2.0×10⁵-1.8×10⁷M^-1). Four HIV-1 carrier sera, which were positive in ELISA using rp17 as the antigen, reacted positively in an ELISA using 3 p17 peptides which were used to titrate murine monoclonal antibodies. Murine monoclonal antibodies having specificity for the 3 p17 peptides stained live HIV-1-infected cells by means of indirect membrane immunofluorescence, irrespective of their specificity. This suggests that the various portions of p17 (at least 3 regions of p17) were exposed on the surface of live infected cells, probably as short polypeptide chains.

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The virulence of thymidine kinase-negative herpes simplex virus type 1 (HSV-1; VRTK^- strain) and type 2 (HSV-2; UWTK^- strain) was studied in comparison with that of their parental strains (VR-3 and UW-268, respectively) in an encephalitis model of adult (4-week-old) and newborn (3-day-old) mice. Viral thymidine kinase (TK) activity was essential for the maximum expression of virulence of HSV-1, because the 50% lethal dose (LU₅₀) of VRTK^- was 60 times higher than that of VR-3 in the brains of newborn mice expressing high levels of cellular TK activity. However, the UWTK^- strain showed the same virulence as the parental strain in newborn mice, despite the lack virulence in adults, suggesting that replication of the UWTK^- strain was completely supported by cellular TK activity. This difference in the role of viral and cellular TKs for virus growth between HSV-1 and HSV-2 was confirmed with the one-step growth of virus strains in L-M and L-M(TK^-) cells.

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Herpes simplex virus (HSV) class-specific antibody responses after primary genital herpes infection were evaluated with an enzyme-linked immunosorbent assay (ELISA) in 16 patients treated with acyclovir (ACV), given orally, and 17 patients treated with adenine arabinoside (Ara-A), given topically. ACV significantly suppressed the levels of IgM, IgA, and IgG. In the ACV-treated patients, IgM and IgG were not detected in 4 of the 16 and in 1 of the 16 patients, respectively. We must take into account this suppressive effect of ACV on antibody responses, especially on the IgM response, when serodiagnosis of HSV infection is made.

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In the present study, mice of 3 different haplotypes (H-2d, H-2k and H-2b) were sensitized subcutaneously with heat-killed H37Ra or 38-kDa antigen of Mycobacterium tuberculosis. Lymphocytes obtained from immunized animals were challenged in vitro with 38-kDa antigen in both cases. The dominant pattern of Th1-like lymphokines (IL-2 and IFN-gamma) and preferential production of 38-kDa specific IgG2a-type antibody were observed. It was noted that 38-kDa antigen was recognized permissively by all 3 strains of mice used in the present study. It was interesting to note that C3H/HeJ mice, which express BCG-resistant alleles showed a higher level of proliferative as well as cytokine response as compared to BALB/c and C57BL/6 mice, which bear BCG-susceptible alleles. These results suggest that not only in recall responses but also during the induction as well as expression phase of the immune response mediated by 38-kDa antigen of M. tuberculosis the Th1-like immune response predominates.

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Effects of prostaglandins (PGs) of the E series on growth and differentiation of murine myeloid leukemic cell line M1 were studied. PGE₁, but not PGE₂, inhibited the growth of M1 cells. PGE₂ neither inhibited nor augmented the antiproliferative effect of PGE₁. PGE₁ augmented the differentiation of M1 cells into macrophage-like cells induced by interleukin 6. PGE₂, however, did not exhibit any effect on the differentiation. PGE₁ caused a marked increase in intracellular cAMP level in M1 cells, whereas PGE₂ had no effect. These results indicate that M1 cells are able to respond only to PGE₁. Radiolabeled PGE₁ binding experiments, however, revealed that there was no specific binding in M1 cells, suggesting that the cells express low numbers of receptors or very low affinity receptors specific for PGE₁. Stable agonists of PGI₂, iloprost, cicaprost or carbacyclin, also potently inhibited the growth of M1 cells. These findings suggest that PGE₁ as well as PGI₂ may play a role in the differentiation of monocyte-macrophage lineage cells.

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Coligenoid, composed of the B subunit of heat-labile enterotoxin from enterotoxigenic Escherichia coli, was separated into monomers in the presence of 2% propionic acid containing 6M urea (pH 3.8). Monomers equilibrated against 0.75% or 0.5% propionic acid containing 3M urea (pH 3.8) did not reassemble into coligenoid. Complexes of GM₁ ganglioside and coligenoid in these buffers were detected by SDS-polyacrylamide gel electrophoresis, but those of the GM₁ ganglioside and monomers were not. The binding ability of monomer to GM₁ ganglioside in these buffers was about 1% of that of normal coligenoid by GM₁-enzyme-linked immunosorbent assay. Moreover, monomers in these buffers reassembled into coligenoid by buffering against original TEAN buffer, and the binding ability of the resulting coligenoid to GM₁ ganglioside was identical to that of native coligenoid. These data suggest that although coligenoid formation is important for the receptor binding of the B subunit, little binding ability to GM₁ ganglioside remains in monomer of the B subunit.

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Thirty strains of Yersinia pseudotuberculosis were isolated from rabbits (17 strains), wild rats (9 strains) and house rats (4 strains) in China between 1990 and 1993. The biochemical properties of these isolates were identical with those of Y. pseudotuberculosis and no special characteristics were found in these strains. Serologically, serogroups 4b and 5b were identical to isolates found in Japan, and a new serogroup 1c and unclassified strains have also been detected. The existence of virulence-associated properties were different among strains. The pYV plasmid was detected from 6 strains of 30 isolates. This report documents the presence of Y. pseudotuberculosis in China, providing important epidemiological information.

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We developed a reverse transcription and polymerase chain reaction (RT-PCR) method for detecting astrovirus serotypes 1, 2, 3, 5, 6 and 7 (but not serotype 4). Furthermore, we developed the specific primers for detecting serotypes 1 and 2, the most predominant serotypes in the world. Sensitivity of the first PCR with serotype common primers was about 10 times higher than that of enzyme immunoassay with monoclonal antibody (EIA-MAb). Sensitivity of the second PCR with the serotype-specific primers was even higher. The RT-PCR method was useful for detecting astroviruses from clinical samples, especially serotypes 1 and 2.

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