Incidence of colicinogenic strains among human Escherichia coli.

During the years 1993-1999, altogether 1,043 Escherichia coli strains from colons of different persons were screened for colicinogeny using a most susceptible procedure and indicator system. In control persons (with healthy colons), 41.37% producers of colicins were found. In patients suffering from salmonelloses, the proportion of colicinogenic Escherichia coli was the same. In patients with non-specific inflammatory colon diseases, the proportion of colicinogenic Escherichia coli strains appeared slightly though weakly, significantly or unsignificantly increased: to 47.50% in morbus Crohn and to 56.10% in colitis ulcerosa. These results suggest some sort of engagement of colicinogeny in the pathogenesis thereof. In malignant tumours of the colon, the incidence of colicinogenic Escherichia coli was not altered (40.58%). This does not indicate any colicin participation in the pathology of malignant tumours. In colitis ulcerosa, the incidence of colicinogenic Escherichia coli strains inhibiting Shigella sonei 17 (the indicator for colicin Js which generally inhibits interoinvasive strains of both species) increased from 21.94% (control samples) to 41.46%. Uropathogenic Escherichia coli strains shared the same incidence of colicinogeny as controls (42.08%), if they were not haemolytic; haemolytic ones were colicinogenic with only 22.37%. This difference was highly significant. The patterns of some colicin activities in the set of five indicator strains used suggested that several wild strains produced new, so far unknown types of colicins and/or combinations thereof.

Inhibition of bacterial pathogens by lactobacilli.

Lactobacilli produce many antimicrobial substances including organic acids, hydrogen peroxide and bacteriocins. Antagonistic activity of lactobacilli is an important factor in the protection of the vagina of fertile women against infection by certain pathogens. In the present study, we investigated 17 strains of lactobacilli, including 11 strains of vaginal origin. The aim was to investigate in more detail the antibacterial activity of lactobacilli and to attempt to assess substances responsible for inhibition. The investigated lactobacilli inhibited some strains of Escherichia coli, Serratia marcescens, Shigella boydii, Listeria monocytogenes, Listeria ivanovii, Listeria innocua and Staphylococcus aureus. We have provided evidence that inhibition is due mainly to organic acids and to a lesser extent, to bacteriocins.

[Antibacterial activity of lactobacilli]. / Antibakteriální aktivita laktobacilu.

The antagonistic action of lactobacilli is an important factor in the protection of the vagina of fertile women from infection by other microorganisms. In the present study the authors investigated 17 strains of lactobacilli, incl. 11 of vaginal origin. The objective was to investigate in more detail the antibacterial activity of lactobacilli and to attempt to assess substances responsible for inhibition. The investigated lactobacilli inhibited some strains of Escherichia coli, Serratia marcescens, Shigella boydii, Staphylococcus aureus, Listeria monocytogenes, Listeria innocua and Listeria ivanovii with different intensity. The authors provided evidence that inhibition is due mainly to organic acids and to a lesser extent to bacteriocins. The authors assessed also the effect of enterobacteria on lactobacilli but did not observe any inhibition of lactobacilli.

[Isolation of mycoplasmas from female genitalia]. / Izolace mykoplazmat z genitálu zen.

The author tested ways of collection, transport and storage of material for mycoplasmatological examination. The use of tampons on a stick during transport in urea substrate medium proved useful. The site of maximum occurrence of mycoplasmas was the posterior vaginal vault. On examination of the vaginal secretion of 804 women Mycoplasma hominis was isolated in 29.6% and Ureaplasma urealyticum in 65.2% of the cases. Concurrent isolation of Mycoplasma hominis and Ureaplasma urealyticum was recorded in 22.1% of the women. The results of the examination do not suggest the participation of mycoplasmas in the development of aminocolpitis. In pregnant women there is a greater probability of colonization of the vagina by U. urealyticum.

The cytotoxic and cytocidal effect of colicin E3 on mammalian tissue cells.

The plasma membrane of mammalian cells can mediate the cytotoxic and cytocidal effects of colicin E3. As little as 10(2) lethal units of purified colicin E3 per cell exert a pronounced cytocidal effect on human epithelial HeLa cells and as little as 10(4) lethal units per cell also on line L mouse fibroblasts in tissue culture. Cells in complete monolayers are rapidly killed, become spherical and shrink, they are detached from the support and finally autolyzed. The percentage of killed cells in both lines is directly proportional to the multiplicity of colicin used. The LD50 for HeLa cells is about 30 times lower than for L cells. At the multiplicity of 10(5) I.u., usually 100% HeLa and 90% L cells are killed in 2--3 days. Purified colicins E2 and D have no demonstrable cytological effect on HeLa cells, although DNA synthesis in L cells appears to be partly inhibited by colicin E2. The profound effect of colicin E3 on mammalian cells could be interpreted in a similar way as in bacteria, viz. as a specific cleavage of rRNA.

Protease activity in cells of Bacillus megaterium during derepression.

A proteolytic activity hydrolyzing denatured proteins of Bacillus megaterium labelled with 35S or 14C amino acids was detected in cells of the asporogenic strain of Bacillus megaterium. The substrate is hydrolyzed by the enzyme or enzymes at optimum pH around 7, their activity being almost completely inhibited by EDTA and o-phenanthroline. PMSF, the inhibitor of serine proteases, is slightly inhibitory. Gel filtration on a Sephadex column separated the protease activity to two or three fractions. The protease activity in cells with the repressed synthesis of protease corresponds to 5-20 mug of substrate degraded per hour by 1 mg of protein at 37 degrees C. It increases five to ten-fold during the derepression. When the intracellular protease activity increases the extracellular enzyme begins to be excreted into the medium. The intracellular protease activity rapidly decreases after the addition of chloramphenicol or of a mixture of amino acids to the derepressed culture. Half or even more of the protease activity is released from the cells during their conversion to protoplasts by means of lysozyme. This "periplasmic" activity remains mostly in the supernatant also after mesosomes have been centrifuged down from the periplasm. A portion of the activity bound in protoplasts sediments together with membrane fraction after their lysis.