Induction of acute arthritis in mice by peptidoglycan derived from gram-positive bacteria and its possible role in cytokine production.

The activities of a water-soluble peptidoglycan fragment derived from Staphylococcus epidermidis (SEPS) were examined as to their role in proliferation of spleen mononuclear cells (SMNC) from various strains of mice, the production of cytokines in vitro, and the induction of an inflammatory reaction in vivo. The proliferation of SMNC from C3H/HeN, C57BL/6, AKR, DBA/2, and ddY mice in reaction to SEPS in vitro showed a peak on day 3 and was greater than that of SMNC from BALB/c mice. The cells of SMNC from C3H/HeN mice responsive to SEPS were indicated to be mainly macrophages. A time kinetics experiment showed a coincidence in the proliferation of SMNC in reaction to SEPS and the detection of colony-stimulating factor (CSF) activity. Interleukin 2 (IL-2) activity was not detected during the incubation periods. When SEPS was administered to mice, much stronger mRNA transcripts of granulocyte-macrophage (GM)-CSF were detected in the lungs of C3H/HeN mice than in BALB/c mice. On the other hand, the amounts of IL-1 and PGE2 produced by SMNC of BALB/c mice stimulated by SEPS were greater than those produced in C3H/HeN mice. SEPS was confirmed to induce arthritis in BALB/c mice, but not in C3H/HeN mice. Our findings suggest that the production of GM-CSF is involved in the in vitro proliferation of SMNC in reaction to SEPS and that along with IL-1 and PGE2 production, contributes to the inflammation by SEPS in vivo.

Activity of sub-minimal inhibitory concentrations of aspoxicillin in prolonging the postantibiotic effect against Staphylococcus aureus.

Aspoxicillin, a newly developed acylureido-penicillin with a long half-life in mouse serum of 55 min, induced postantibiotic effects (PAEs) against Staphylococcus aureus Smith of 1.7 h in vitro and 5.2 h in vivo in a thigh infection model in neutropenic mice. The long serum half-life meant that in order to evaluate the in-vivo PAE, it was necessary to examine the contribution of the drug at a sub-minimal inhibitory concentration (sub-MIC). Growth suppression by sub-MICs of aspoxicillin was examined in vitro using either previously unexposed bacterial cells or cells which had been pre-exposed to twice the MIC of aspoxicillin for 2 h. At each sub-MIC tested, the duration of growth suppression for pre-exposed cells was longer than that for unexposed cells. In an attempt to eliminate the sub-MIC effect in vivo, penicillinase was injected into mice at the time after administration when the aspoxicillin serum concentration approached the MIC. The in-vivo PAE decreased to 2.7 h when penicillinase was injected. It was concluded that aspoxicillin induced a PAE in vivo which was additional to the effect of sub-inhibitory residual drug, but that sub-MIC levels of the drug were simultaneously involved in suppressing bacterial regrowth after the drug concentration decreased below the MIC. Similar postantibiotic sub-MIC effects may also occur with other long half-life antibiotics.

Suppression of B-cell differentiation by natural killer (asialo GM1+) cells in mice.

Mice were injected intravenously with rabbit antiserum to ganglio-n-tetraosylceramide (asialo GM1, ASGM1), a neutral glycosphingolipid present at high quantities on the surface of natural killer (NK) cells. Spleen cells prepared from the mice were then examined for NK activity against YAC-1 targets, for phagocytic cells and by flow cytometric analysis for Thy1, Lyt1, Lyt2, ASGM1 and surface Ig (SIg) phenotypes. Administration of anti-ASGM1 in mice resulted in a complete depletion of NK activity and ASGM+1 cells in the spleen, but no changes in the proportions of Thy1+ cells and their Lyt1+ and Lyt2+ subsets and phagocytic cells. Corresponding to this selective depletion of ASGM+1 cells and NK activity, the spleen cells showed an increased number of SIg+ B cells and augmented mitogenic responses to B-cell but not T-cell mitogens. These NK-depleted spleen cells also showed production of pokeweek mitogen (PWM)-driven plaque-forming cells (PFC) to much higher levels than those of control spleens. In the spleens of mice treated with varying concentrations of anti-ASGM+1, a good correlation was found between the decreased NK activity and the enhanced PFC response. To directly test the possible suppressor activity of NK cells on PWM-induced PFC response, NK (ASGM+1) cells were highly purified from the spleen by a combination of Percoll gradients and cytolysis of T cells by monoclonal antibodies followed by indirect panning. When added to NK-depleted spleen cells, they suppressed the augmented PFC response of NK-depleted spleen cells, depending on the number of cells added. These results suggest that NK (ASGM+1) cells in mice exhibit a suppressor property on B cells, which are undergoing spontaneous or mitogen-induced differentiation.

Macrolide antibiotics M-4365 produced by Micromonospora. IV. Antimycoplasmal activity of antibiotic M-4365 G2 (de-epoxy rosamicin).

In vitro activities of M-4365 G2, a new basic 16-membered macrolide antibiotic, against a total 19 strains including human, bovine, porcine, rodent, avian and saprophytic mycoplasmas were compared with those of three other macrolide antibiotics, josamycin, erythromycin and tylosin. M-4365 G2 exhibited stronger activities than the other macrolide antibiotics against 11 strains of mycoplasma tested. Especially, its higher activities against M. pneumoniae Mac and FU, U. urealyticum T-960, M. mycoides PG-1 and M. gallisepticum Kp-13, PG-31 and 9-49A were to be noticed (final minimum inhibitory concentrations: 0.0001 approximately 0.049 microgram/ml). Higher antimycoplasmal activity of M-4365 G2 than that of tylosin was also proved in experimental treatment of chickens intranasally inoculated with M. gallisepticum Kp-13 by feeding a diet containing the drug. M. gallisepticum Kp-13 was not isolated from the infected chickens fed a diet containing 0.0063% or more of M-4365 G2.