Detection of bacterial strains producing sulbactam- or tazobactam-sensitive beta-lactamases by the use of disks containing the inhibitors alone instead of combining them with antibiotics.

The author demonstrated that disks containing beta-lactamase inhibitors sulbactam or tazobactam combined with ampicillin (SAM) and piperacillin (TZP) are not suitable for performing the double-disk synergy test (DDST) with the aim of determining the sensitivity of beta-lactamases to these inhibitors. The presence of antibiotics (especially of piperacillin) is so disturbing that the results of testing are not specific. In contrast, the use of disks containing sulbactam or tazobactam alone yields very specific results. The author suggested to the firms producing sensi-disks that they make these commercially available to laboratory workers.

Oxidative stress in brain during experimental bacterial meningitis: differential effects of alpha-phenyl-tert-butyl nitrone and N-acetylcysteine treatment.

Antioxidant treatment has previously been shown to be neuroprotective in experimental bacterial meningitis. To obtain quantitative evidence for oxidative stress in this disease, we measured the major brain antioxidants ascorbate and reduced glutathione, and the lipid peroxidation endproduct malondialdehyde in the cortex of infant rats infected with Streptococcus pneumoniae. Cortical levels of the two antioxidants were markedly decreased 22 h after infection, when animals were severely ill. Total pyridine nucleotide levels in the cortex were unaltered, suggesting that the loss of the two antioxidants was not due to cell necrosis. Bacterial meningitis was accompanied by a moderate, significant increase in cortical malondialdehyde. While treatment with either of the antioxidants alpha-phenyl-tert-butyl nitrone or N-acetylcysteine significantly inhibited this increase, only the former attenuated the loss of endogenous antioxidants. Cerebrospinal fluid bacterial titer, nitrite and nitrate levels, and myeloperoxidase activity at 18 h after infection were unaffected by antioxidant treatment, suggesting that they acted by mechanisms other than modulation of inflammation. The results demonstrate that bacterial meningitis is accompanied by oxidative stress in the brain parenchyma. Furthermore, increased cortical lipid peroxidation does not appear to be the result of parenchymal oxidative stress, because it was prevented by NAC, which had no effect on the loss of brain antioxidants.

Influenza vaccination of human immunodeficiency virus 1-infected patients receiving antiretroviral therapy.

In 13 human immunodeficiency virus 1 (HIV-1) infected patients receiving a highly active antiretroviral therapy (HAART) annual influenza vaccination was conducted. It was hoped that HAART would prevent a post-vaccination increase in HIV-1 load and potential adverse effects. Only two patients had an increased viral load on day 14 post vaccination (p.v.). At 6 months p.v., the majority of the patients had a significantly increased CD4 cell count and a significantly decreased viral load. This indicates that HAART can protect patients from adverse consequences of influenza vaccination. The production of antibodies to the influenza A and B viruses in the HIV-infected patients was substantially lower than that in healthy persons. We propose that HIV-positive patients receiving HAART should be subjected to annual influenza vaccination.

Production of sodium azide inactivating substance by resistant mutants of Salmonella typhimurium and other bacteria.

We have found that azide-resistant mutants of Salmonella typhimurium and of other bacteria studied produce a substance which inactivates the azide. The production of this substance was proved by the demonstration of a satellite growth of azide-sensitive cells around colonies of azide-resistant mutants and by testing azide inactivating properties of culture filtrates of the azide-resistant strains. The same substance was found to be present in lower concentrations in culture filtrates of wild-type sensitive strains. In both cultures of sensitive strains, it was apparently produced by the resistant mutants and not by the sensitive cells. The substance does not pass across a dialysis membrane and is heat stable. It has a high molecular weight but is not a protein.

Efficiency and suitability of the penicillin-phenol red acidometric test for detection of beta-lactamase production in staphylococci.

The penicillin-phenol red acidometric test was found to be highly efficient and suitable for the detection of beta-lactamase production in staphylococci. The author presents his modification of the procedure and discusses its advantages. He recommends that all staphylococcal strains be tested for beta-lactamase production on the day of isolation.

Comparison of the efficiency of three methods for the determination of staphylococcal beta-lactamase.

Three methods for demonstrating the production of beta-lactamase in resistant strains of Staphylococcus aureus were compared. The "satellite phenomenon" method proved to be more sensitive than the nitrocefin test and the iodometric test.

Additive effect of the combination of griseofulvin and ketoconazole against Microsporum canis in vitro.

The susceptibility of 28 strains of Microsporum canis to griseofulvin, to ketoconazole and to a combination of both antifungal drugs was determined. Griseofulvin proved to be more active than ketoconazole. The combination of both antifungal agents was found to exert an additive effect.

Immunostimulation by vitamin C.

A review of the literature shows that vitamin C undoubtedly has a positive effect on some mechanisms of the natural resistance against infections as well as on the immune response. It is generally accepted that vitamin C increases the chemotaxis of granulocytes and of macrophages. There is also ample evidence that vitamin C increases the phagocytic activity of granulocytes as well as of macrophages. As to the effect of vitamin C on the immune response, the available data allow the conclusion that vitamin C is necessary for the induction of delayed hypersensitivity, i.e. cellular immunity. Its effect on the antibody production appears, however, to be minimal or none. In our previous in vivo studies we obtained the results which were consistent with the conclusion that high doses of vitamin C increase the efficiency of immunization with a human cell culture rabies vaccine in guinea-pigs. The purpose of this study was to establish whether relatively low doses (10 mg/kg body weight) of vitamin C have a similar effect as megadoses (100 mg/kg body weight). We observed that the efficiency of immunization with the human diploid cell culture rabies vaccine (Mérieux/Lyon) was better in the group of guinea-pigs treated with the vaccine plus vitamin C (10 mg/kg body weight) than in the group treated with the vaccine alone. The difference in the number of survivors in both groups of animals was statistically not significant, but considering the factor of repetition (a similar result in repeated experiments) we nevertheless conclude that vitamin C acts in the doses used as an immunopotentiator.

Vitamin C acts as a cocarcinogen to methylcholanthrene in guinea-pigs.

Large doses of vitamin C were found to promote the induction of sarcomas by methylcholanthrene. The tumours appeared earlier in the group of guinea-pigs treated with vitamin C after injection of methylcholanthrene than in the control group injected with methylcholanthrene. The treatment of guinea-pigs with vitamin C after induction of tumours thus did not inhibit the growth of tumours.