Effects of concentrated supernatants recovered from Lactobacillus plantarum on Escherichia coli growth and on the viability of a human promyelocytic cell line.

AIMS: The ability of concentrated supernatants from Lactobacillus plantarum to produce a disruption of plasma membrane in eukaryotic and prokaryotic cells has been examined. METHODS AND RESULTS: A strain of Lact. plantarum (tolerant to acid and bile salts and resistant to several antibiotics) was used. It inhibited the growth of pathogenic Escherichia coli and L. monocytogenes. Supernatants from Lact. plantarum were concentrated by centrifugation. Either E. coli or HL-60 cells (a human promyelocytic cell line) were treated in the presence of the concentrated supernatants. The effect of concentrated supernatants from Lact. plantarum on E. coli growth demonstrated a bacteriostatic activity and a loss of cell viability measured by sytox green staining. Concentrated supernatants were capable of disturbing plasma membrane in E. coli and of promoting a cytotoxic and lyctic action on HL-60 cells and on human erythrocytes, respectively. CONCLUSIONS: These results suggest that Lact. plantarum release an effective compound responsible for an important effect in the disruption of E. coli plasma membrane and for a cytototoxic activity on promyelocytic leukaemia cells. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first in vitro study about the antimicrobial and biological activities of concentrated supernatants from Lact. plantarum.

Modification of acquired immunity in BALB/c mice by aztreonam.

Recent studies have suggested that antibiotics may act as biological response modifiers. In this study we investigated the effect of aztreonam, a monobactam antibiotic, on different parameters of acquired immunity in BALB/c mice. Different dosages of aztreonam injected into mice induced an increase in the lymphoproliferative response to specific mitogens and in the production of interleukin-2 by splenic cells, as well as a decreased response of this immune population to sheep erythrocytes lower total blood cell counts and a lower percentage of monocytes than in untreated mice. These results show a modulatory action of aztreonam on different immune parameters, which is independent of its antimicrobial activity and that could be of interest in human therapy.

Effects of aztreonam on natural immunity in mice.

The influence of the dose and the duration of treatment with aztreonam, a monocyclic beta-lactam antibiotic, on the natural immune response of mice has been investigated. The results show the effects induced by the antibiotic on several immune parameters were affected by the duration of treatment. Thus, treatment with 28 mg/kg per day of aztreonam over 14 days increased every immune parameter tested, while treatment with 57 mg/kg per day of aztreonam for 7 days only enhanced the natural killer (NK) activity of splenocytes. Since aztreonam does not apparently impair the innate immune response, it might be a suitable therapy for the treatment of patients who are immunosuppressed.

Modification of natural immunity in mice by imipenem/cilastatin.

The imipenem/cilastatin constitutes a broad spectrum beta-lactam antibiotic formulation, especially used in pre and post-operatory treatments for transplanted or drug-immunosuppresed patients. The effect of the dose and the duration of the treatment with imipenem/cilastatin on some parameters of natural immunity in BALB/c mice were examined. The treatment by intraperitoneal route with 1 or 2 g/70 kg/day during 7 days did not alter significantly the parameters tested, whereas the greater dose used (4 g/70 kg/day) had an inhibitory effect on peritoneal cell counts and phagocytic activity, as well as it caused an increase on IL-1 production and natural killer activity. The greater stimulating effect of innate immunity was obtained with the lowest imipenem/cilastatin dose used (0.5 g/70 kg/day). Since this antibiotic apparently does not impair the studied innate immune responses at 1 or 2 g/70 kg/day, it seems to be especially suited for the therapy of systemic bacterial infections in immunocompromised patients.

A study on the microbiota from olive-mill wastewater (OMW) disposal lagoons, with emphasis on filamentous fungi and their biodegradative potential.

The microbial composition of olive mill wastewater (OMW) from four disposal ponds has been studied. Such OMW samples contained a variable (but high) number of bacteria, yeasts and molds. Among the latest, members of twelve different genera (Acremonium, Alternaria, Aspergillus, Chalara, Fusarium, Lecytophora, Paecilomyces, Penicillium, Phoma, Phycomyces, Rhinocladiella and Scopulariopsis) were found. Members of five genera (Chalara, Fusarium, Paecilomyces, Penicillium and Scopulariopsis) were widely distributed, and they were able to grow efficiently in undiluted OMW as a sole source of nutrients. Strains of Fusarium, Paecilomyces, Penicillium and Scopulariopsis showed a marked capacity for OMW detoxification, depleting its antibacterial activity almost completely.

Modification of acquired immunity in mice by imipenem/cilastatin.

The immunomodulating properties of antimicrobial drugs may have important implications for clinical practice, particularly for those patients whose immune system has been compromised. In this study, we assessed the influence of different treatments with a beta-lactam antibiotic (imipenem/cilastatin) on several acquired immune responses of BALB/c mice; splenocyte responses to specific mitogens and to sheep red blood cells, IL-2 production and proportions of the different lympho-monocytic populations. Impenem/cilastatin was shown to modify some lymphocyte-associated immune functions and it would be useful to investigate whether immunomodulatory effects also occur in humans.