The antipsychotic drugs belong to the class of phenothiazines that possess multiple effects on eucaryotic and procaryotic cells. These effects include membrane permeabilization (6, 9), alteration of cyclic nucleotide metabolism (7), intercalation into DNA (5), and antimicrobial activity (4; L. Galeazzi, thesis, corso di laurea, Universita di Camerino, Camerino, Italy, 1984). Interestingly, phenothiazines, and particularly chlorpromazine, have also been used as reagents for developing tests for the demonstration of the peroxidaselike activity of hemoglobin (1, 3). Peroxidase tests are also utilized in microbiology for the differentiation and characterization of bacterial strains. Generally, the bacterial peroxidase tests are used to perform semiquantitative whole cell enzymatic determinations. However, currently used semiquantitative assays for microbial peroxidases present some drawbacks, particularly the need for preliminary permeabilization of bacterial cells (8). For example, often the peroxidase test with o-dianisidine does not show any color formation with whole cells that have not been previously permeabilized. On the other hand, some procedures of permeabilization may interfere with enzyme detection (8). Taking into account that chlorpromazine has been well established to cause alterations in the permeability of bacterial cell walls and membranes (6) and moreover to constitute an optimal reagent for detecting peroxidase activity (1, 3), we decided to develop a microbiological application of the chlorpromazine-peroxidase reaction. In this paper we describe an assay which demonstrates that chlorpromazine may contemporaneously act both as a cell permeabilizer and as a reagent for the detection and quantitative estimation of bacterial peroxidase activities. The microbial strains tested were from the American Type Culture Collection (ATCC), Rockville, Md., and from specimens submitted to our clinical laboratory (Table 1). Bacterial suspensions for whole cell peroxidase determinations were prepared from colonies harvested from Mueller-Hinton agar (BBL Microbiology Systems, Cockeysville, Md.). Although cells could be added directly to the reaction mixture with an inoculating loop, cell suspensions in water were used because they provide standardized inocula which may be turbidimetrically controlled. Inocula which gave an absorbance of about 1.5 to 2 at 540 nm in the final reaction mixture were used to avoid false-negative reactions due to weak color formation at lower inocula.

We present experimental evidence that adrenalin autoxidation causes bacterial growth inhibition and killing. The experimental model utilized detects ‘oxygen toxicity’ in prokaryotes using standard microbiological assays for antibacterial activity, allowing direct observation of the toxicity exerted on bacterial cells and the scavenging of toxic intermediates by the defence enzymes catalase and superoxide dismutase.

Amiloride is one of the major molecular probes in basic and applied investigations on the physiology of cation transport in animal cells. In these cells the drug also exerts growth inhibitory activity. Recently, we discovered that amiloride causes growth inhibition also on bacterial cells. In this paper we report that medium pH influences amiloride activity on Streptococcus faecalis. The lowering of external pH causes a drop in the susceptibility of this bacterium to amiloride up to an almost complete resistance. This finding, constitutes a novel aspect of the in vitro experimental pharmacology of this diuretic potentially useful also in clinical pharmacology and in animal cell investigations.

The beta-adrenergic compound isoproterenol was used as oxidizable reagent in a whole-cell assay for the detection of bacterial peroxidase activities. Isoproterenol has been shown to constitute a useful reagent for detecting peroxidase activities in enzymatic tests, utilizing standard purified enzymes, and in the microbiological application proposed. The procedure developed is simple and rapid to perform. In contrast to currently used whole-cell tests for bacterial peroxidases, the assay described here does not need preliminary permeabilization; moreover, the compound utilized does not have related toxicological problems. Therefore, the isoproterenol assay may represent a low-cost safe additional peroxidase test in clinical bacteriology.

Chlorpromazine was used to perform a test for the detection of microbial peroxidase activities. The compound acts as both a cell permeabilizer and a reagent in the procedure developed which allows the detection of peroxidase and peroxidase like reactions both semiquantitatively in whole cell determinations and quantitatively in cell-free supernatants.