Lactobacillus sp. strain GG, which was isolated from the feces of a normal person, produced a substance with potent inhibitory activity against a wide range of bacterial species. It inhibited anaerobic bacteria (Clostridium spp., Bacteroides spp., Bifidobacterium spp.), members of the family Enterobacteriaceae, Pseudomonas spp. Staphylococcus spp., and Streptococcus spp., as demonstrated by a microbiological assay; however, it did not inhibit other lactobacilli. The inhibitory activity occurred between pH 3 and 5 and was heat stable. Bactericidal activity against Escherichia coli was demonstrated at a dilution of 1:128. The inhibitory substance was distinct from lactic and acetic acids. It had a low molecular weight (less than 1,000) and was soluble in acetone-water (10:1). Because of these characteristics, the inhibitory material could not be considered a bacteriocin; it most closely resembled a microcin, which has been associated previously with members of the family Enterobacteriaceae.

Abstract— Various nitrogen containing compounds have previously been shown to quench singlet oxygen (10z). When measuring the dimol 1O2 light emission arising from the H2O2/OCI‐ reaction, we found that certain cyclic diamines increase the emission of light, while other amines were inhibitory. This increase of light emission was seen with both 1, 4diazabicyclo[2.2.2]octane and N, N'‐dimethylpi‐perazine but not with acyclic analogues. Sodium azide inhibited both the normal and enhanced light emission. The enhanced light emission shows spectral properties characteristic of lO2 dimol emission.

Toxigenic strains of Escherichia coli isolated from humans were studied for adherence to human buccal mucosal epithelial cells. The E. coli strains were labeled with 3H-amino acids or fluorescein isothiocyanate. Toxigenic E. coli strains varied in their ability to adhere in the presence of mannose. Of 32 toxigenic strains examined, 52% bound to the buccal cells, whereas none of 8 control strains did so (Mann-Whitney U test, P = 0.007). The control strains were nontoxigenic E. coli isolates from humans, enterotoxigenic E. coli isolates from animals, and E. coli K-12 containing the K88 or K99 plasmid; these strains exhibited only background-level adherence in this assay. Among the toxigenic E. coli strains that bound to human buccal mucosal cells, there was no correlation with mannoseresistant hemagglutination (MR-HA) of guinea pig and human erythrocytes.Screening 32 strains, we found the following phenotypes: (i) MR-HA', buccal adherent; (ii) MR-HA', buccal nonadherent; (iii) MR-HA-, buccal adherent. Presumably the third group represents strains with another type(s) of surface attachment components not involved in the MR-HA reaction. Our findings indicate that a number of bacterial surface structures can function in MR-HA and buccal adherence.A recognized virulence factor in enterotoxigenic strains of Escherichia coli is the ability to colonize the upper intestinal tract of humans and animals. As demonstrated by fluorescent antibody, the organisms are-located on the surface of the epithelium, but they do not penetrate the mucosal surface, nor do they cause any perceptible inflammatory response.

A heat-labile cytotoxin was isolated from virulent strains of axenically cultivated Entamoeba histolytica. Strains of E. histolytica representing a spectrum of virulence as determined in animal and in vitro models of disease were examined for cytotoxic activity. Extracts of virulent strain HM1 possessed marked cytotoxic activity, those of moderately virulent strain 200 showed intermediate activity, and those of avirulent strains 303 and Rahman showed no activity. The cytotoxin was partially purified from the cell-free supernatant of sonicated E. histolytica HM1 trophozoites by ammonium sulfate precipitation and gel filtration. Cytotoxic activity was stable in a narrow pH range (6-7.2) and in 1 M NaCl, urea, and guanidine. Specific immune rabbit and human antiserum as well as the protease inhibitors aprotinin, pepstatin, and leupeptin inhibited cytotoxicity. The partially purified cytotoxin did not have any detectable degradative enzymatic activities. Thus, virulent strains of E. histolytica possess an immunogenic cytotoxic protein which may be important in the pathophysiology of amoebiasis.

Pili from enterotoxigenic Escherichia coli pathogenic for humans have been isolated by adsorption to the surface of erythrocytes followed by thermal elution. The pili are composed of two protein subunits with molecular weights of 13,100 and 12,500 as determined by sodium dodecyl sulfate-gel electrophoresis. These pili also bind to human buccal cells under temperature conditions (37 degrees C) which prevent the binding of these pili to the erythrocytes. Analogous temperature effects on binding have previously been observed with whole bacterial cells. This binding can be inhibited by antiserum prepared against the isolated pili.