Validity of mechanism of gene transfer in the process called conjugation in bacteria.

We have attempted a new evaluation of the process of conjugation in bacteria, because of some basic dissimilarities observed between this and that of eukaryotes, or plants and animals. Reference donor and recipient strains, widely used to prove conjugation in bacteria, were chosen; addition of DNase during the conjugation process, led to an unexpected but highly reproducible increase in the transconjugant colony counts (TCC; ca. > or = 1 log), when compared with that of the controls without DNase. Transconjugants were also obtained when the same live donors were substituted with the UV-killed ones although the TCC was very low initially. Contrarily, donors treated with DNA-intercalating agents, e.g. acridine orange or ethidium bromide, resulted in a complete failure to produce transconjugants. There was a quantitative relationship between the DNase used on donors and levels of DNA sugars/nucleotides/DNA, which possibly resulted from interaction between the DNase and DNA being present/produced on the donor surface. This may be indicative of what may actually happen in the donor-recipient mixtures in the conjugation test proper, where the recipient DNase may activate a donor DNA production cycle. The evidences presented did not suggest that the donor DNA in the conjugation process is actually vestibuled through any intercellular conjugation passages, and is susceptible to the action of DNase or the intercalating dyes.

In vitro & in vivo experimental susceptibility of Mycobacterium marinum to augmentin.

The effect of augmentin alone and in combination with various beta-lactam antibiotics was studied against a pathogenic Mycobacterium, M. marinum. The in vitro studies did not reveal any additional advantage over that found with augmentin alone and this antibiotic seemed considerably inhibitory to M. marinum at < 1 microgram/ml concentration. In vivo, the effects of augmentin on experimentally produced lesions in the mouse foot pads (MFPs) showed a significant regression of the lesions, which was compatible with an early disappearance of M. marinum from the MFP, in contrast with those of the untreated, control animals.

Effect of exogenous 5-hydroxytryptamine on pathogenicity of Entamoeba histolytica in experimental animals.

In an effort to find out the mechanism(s) operative in enhancing the pathogenicity of E. histolytica in hosts under heat stress reported earlier, effect of 5-hydroxytryptamine (5-HT) on the virulence of the parasite was examined in just weaned Charles Foster strain of albino rats. Pathogenicity of 10 strains of E. histolytica, from various forms of intestinal amoebiasis, grown in modified Boeck and Drbohlav's medium was assessed by caecal scoring. Administration of 5-HT in infected animals significantly enhanced the pathogenicity of all the seven strains tested. Treatment of the host with the 5-HT precursor L-tryptophan also increased the caecal scores examined with three strains of E. histolytica. Prior blocking of tissue 5-HT receptors by administration of methysergide almost completely abolished the pathogenicity enhancing effect of 5-HT treatment. This suggested that 5-HT itself and not any of its metabolites was responsible for the observed increase in pathogenicity of E. histolytica on 5-HT treatment of the host.

Drug interaction of promethazine & other non-conventional antimicrobial chemotherapeutic agents.

The antihistamine compound promethazine (Pz) showed significant antibacterial action when tested against 124 strains of aerobic and 13 strains of anaerobic bacteria belonging to both Gram positive and Gram negative genera. The range of MIC (micrograms/ml) of Pz varied between 50 and 200 micrograms/ml among most of the test organisms. Six Pz-sensitive strains were found to be simultaneously sensitive to similar non-conventional antimicrobics, e.g., methdilazine, bromodiphenhydramine, diphenhydramine, methyl-DOPA, promazine and the antibiotic augmentin. A high degree of synergism was observed in vitro when Pz was used in combination with methdilazine and bromodiphenhydramine.