Preliminary investigations of some derivatives of oxamniquine.

Oxamniquine is a potent schistosomicide used clinically in the treatment of infections due to Schistosoma mansoni. Although relatively well tolerated, some central nervous system (CNS) effects characterised by convulsions have been reported in a small proportion of the population receiving this drug. Oxamniquine, the major metabolite and the secondary alcohol have been screened for convulsant activity by assessing their ability to potentiate catechol induced seizures in urethane anaesthetised mice. Significant (p < 0.05) potentiation was observed with subconvulsive doses (1.5 mg/kg) of strychnine. In contrast, oxamniquine and the secondary alcohol, each at 200 mg/kg ip, both produced significant (p < 0.05) depressions of seizures in this model whereas no effect was seen following 140 mg/kg ip of the acid derivative. These results indicate anticonvulsant rather than convulsant activity in oxamniquine and the alcohol derivative. The failure to observe any effect with the acid derivative may have been due to poorer CNS penetration.

In vitro studies of haemolysis by some staphylococci grown in chemically defined media.

Staphylococcus aureus (five strains) and Staph. epidermidis (one strain) have been evaluated for comparative growth and haemolysin titre in both brain heart infusion (BHI) and in developed, nutritionally adequate, chemically defined media (CDMs) varying only in amino acid composition. The ability to show a particular haemolytic profile was strain-dependent and the haemolytic titre (HU50/ml) was both strain- and medium-dependent. Highest titres of both alpha and beta type haemolysins were obtained in BHI. Maximum titres were in general detected in the late exponential phase in both CDMs and BHI. Titres declined during the stationary phase in CDMs. Staphylococcus epidermidis produced a delta-type haemolysis profile on BHI-based blood agars, but only rabbit blood was sensitive in agars based on a developed, chemically defined medium (CDM/A; 13 amino acids) in which all six staphylococci grew. The addition of yeast extract to CDM/A increased alpha haemolysin titre, but suppressed beta haemolysin formation; beta haemolysin was, however, detected in yeast extract/phosphate-buffered saline. Strain Wood 46 degraded haemoglobin, but only in (initially) whole blood; red blood cell-free haemoglobin-rich plates (BHI) were unaffected during growth. A novel haemolytic profile is described for Staph. aureus NCTC 8532 growing on blood agars based on CDM/A and may relate to the production of methaemoglobin during haemolysis.

The influence of pyrithione on the growth of micro-organisms.

Pyrithione was active against a range of micro-organisms, the most resistant being Gram-negative bacteria. The growth curves for Klebsiella pneumoniae and Bacillus licheniformis showed a drug-dependent lag phase. Candida albicans grew with a drug-dependent growth rate. EDTA antagonized the effects of pyrithione.

Aspects of the effect of bile salts on Candida albicans.

Cholic acid, chenodeoxycholic acid, deoxycholic acid, glycocholic acid, glycodeoxycholic acid, hyodeoxycholic acid and lithocholic acid as their sodium salts, were fungistatic to the growth of Candida albicans. Of the compounds tested, cholic acid, deoxycholic acid and chenodeoxycholic acid were the most active. In combination with other antifungal agents only cholic acid exhibited synergism with amphotericin B, whilst the imidazole antifungal agents inhibited the action of the bile salts. The bile salt minimal inhibitory concentrations were close to the critical micelle concentrations. Even though the compounds are surface active they did not cause loss of intracellular K+ and were without effect on oxygen consumption. The bile salts, particularly cholic acid, produced morphological changes that gave rise to swollen cells.

Experimentally induced Bacteroides infections in the rabbit.

Rabbits were infected with Bacteroides fragilis, B. macacae and B. gingivalis in monoinfection, mixed Bacteroides infection, and mixed infection of B. gingivalis with Streptococcus faecalis, Escherichia coli and Clostridium sporogenes. Monoinfection gave rise to localised, nodular abscesses at cell levels greater than 0.5 X 10(5) cfu ml-1, the severity of which was dose related. Mixed infections including B. gingivalis caused severe spreading lesions and affected organs distant from the injection site. Histopathological studies indicate an inflammatory response with gas vacuolation and local necrosis.

The influence of incubation time and medium composition on fatty acid production by some Bacteroides species.

Thirteen strains (eleven species) of Bacteroides have been examined for the production of short chain fatty acids (SCFAs). Two media, cooked meat glucose (CMG) and peptone yeast glucose (PYG) were examined quantitatively by gas liquid chromatography (glc) after anaerobic incubation at 37 degrees C for up to 7 days. Growth and medium pH were monitored in PYG for two species. The SCFA profile was established after 12 h and the amount of acids produced was greater in CMG than in PYG; both CMG and PYG contained SCFAs prior to inoculation. Maximum acid production and lowering of pH appear to coincide with the stationary phase of growth. Results are discussed in terms of a standardized approach to the identification of anaerobic bacteria.

Local anaesthetics as antibacterial agents: effects on cellular respiration and the leakage of cytoplasmic constituents.

The effect of four local anaesthetics, amethocaine and procaine (esters) and cinchocaine and lignocaine (amides), on the respiration and dehydrogenase activity of E. coli has been studied. Cells were suspended in either a chemically defined medium or in 0.2 M phosphate buffer (pH 6.4). Substrates included: glucose, succinate, malate and lactate. Further studies on the release of cellular constituents (pentoses and inorganic phosphate) are included and indicated that some local anaesthetics, at high concentrations, inhibit autolysis. Results are discussed in terms of the action of local anaesthetics on membrane integrity and its significance in enzyme action. A novel method for the detection of inorganic phosphate by differential pulse voltammetry and its application to studies of drug induced leakage of intracellular materials is described.

Ampicillin induced septum formation in Bacillus cereus.

Cells of Bacillus cereus grown in the presence of subinhibitory concentrations of ampicillin at either 30 degrees or 45 degrees C exhibited an increase in the numbers of centres of septum formation per unit cell length. Under identical conditions of cultivation, cells of Escherichia coli grew as aseptate filaments. In general, untreated B. cereus cells grown at 45 degrees C were longer than those grown at 30 degrees C. The strain of E. coli used was unaffected in terms of filamentation by elevated growth temperature. Results are discussed in terms of the presence and availability of penicillin binding proteins and autolysins involved in cell growth, division and separation.

Local anaesthetics as antimicrobial agents: structure-action considerations.

The antibacterial activity of four local anaesthetics (LAs), amethocaine and procaine (esters), and cinchocain and lignocaine (amides), has been studied. All four LAs inhibited cell growth but only amethocaine and cinchocain had significant effects on cell viability and on the leakage of cellular constituents. Effects on growth inhibition were reversible. Concentrations causing marked loss in viability also caused the leakage of cellular constituents. Uptake isotherms for all four LAs by E. coli are presented and an attempt made to relate derived intracellular LA levels with effects on growth inhibition. Cultures of E. coli grown in the presence of low levels of LAs effects reflecting the relative hydrophilic-lipophilic nature of the individual LAs.

Local anaesthetic induced turbidity increases: implications of interactions with intact bacterial cells and with subcellular fractions.

Four local anaesthetics (LAs), amethocaine and procaine (esters) and cinchocaine and lignocaine (amides) have been assessed in terms of their ability to induce turbidity increases in non-growing cells of Escherichia coli suspended in a carbohydrate free defined medium (CFM) or distilled water or in 0.2 M phosphate buffer. Procaine and lignocaine did not induce turbidity increases. The turbidity increase-LA concentration profiles for both amethocaine and cinchocaine are similar in all three systems. Slight variation are discussed in terms of the ionic content of the suspending media. Interactions between LAs and dispersed systems comprising: cell envelope preparations, cytoplasmic contents, lipid depleted cells and cell lipid dispersion, are also described. Transmission electron micrographs of LA treated cells are presented and the use of uranyl acetate as a 'vital' stain is illustrated. Results are discussed in terms of LA lipophilicity and the effectiveness of LAs in precipitating intracellular materials at high concentrations.