Plasmid-mediated sulfonamide resistance in Neisseria meningitidis.

An 8.5-megadalton plasmid coding for sulfonamide resistance was found in a clinical isolate of Neisseria meningitidis, as demonstrated by plasmid elimination and transformation experiments. The plasmid complemented a mutation which determines the production of a thermosensitive dihydropteroate synthetase in Escherichia coli, thus suggesting that the mechanism of resistance involved a plasmid-encoded dihydropteroate synthetase

MODULATORY EFFECTS OF HEN EGG-WHITE LYSOZYME ON IMMUNE RESPONSE IN MICE

The effect of her egg-white lysozyme (HEWL) on immune response was evaluated by measuring antibody-producing cells and circulating antibodies in mice inoculated with the test antigen (SRBC or BSA) and HEWL at the same time but in a separate body area. HEWL caused a premature decline in SRBC-specific plaque forming cells (PFC) and a reduction in the total amount of these cells. HEWL inhibited antibody production against BSA in the primary response, but was devoid of any effect on the secondary response elicited in the same mice by a second inoculation of the test antigen. The inhibitory effect of HEWL was dose-dependent, being maximal with 300 micrograms, required an enzymatically active protein and was not shown by other basic proteins. HEWL also abolished the enhancing effect of LPS and CFA on anti-BSA antibody production. The inhibitory activity of HEWL was further increased by hydrolyzed peptidoglycan. These results suggest that HEWL modulates the immune response in mice and performs this function through activation of non-specific suppression mechanism

Inhibition of Herpes simplex virus-induced cytopathic effect by modified hen egg white lysozyme

Hen egg-white lysozyme and three of its basic derivatives obtained by chemical modification were tested for their activity in vitro against a wild strain of herpes simplex virus type 1. Marked inhibition of the cytopathic effect was exhibited by the three chemical derivatives and the heat-inactivated lysozyme, whereas the native enzyme displayed only modest anticytopathic activity. Enzymatic activity did not appear to be necessary for the antiherpes activity of the lysozyme compounds. Instead, other properties such as their basic nature seemed to be relevant to their antiherpes effectiveness in vitro. At the concentrations used, all compounds but one had no significant effect on cell viability and growth. Some of the compounds tested caused formation of deposits on the surface of the cells. Some correlation between deposit formation and antiherpes cytopathic activity was found. The antiherpes efficacy in vitro and toxicity of the modified lysozymes were compared with those of known antiviral agents. The lysozymes were less toxic than the reference antiviral agents, and some of them were also more activ