Effect of Streptococcus faecalis BIO-4R on intestinal flora of weanling piglets and calves

The effect of oral administration of Streptococcus faecalis BIO-4R, an antibiotic-resistant lactic acid bacterium, on the intestinal flora of weanling piglets and cows reared on antibiotic-containing diet was investigated. Fourteen days after administration of the bacteria, the intestinal flora of the piglets was examined. Animals of the administered group had stabilized lactic flora such as bifidobacteria, streptococci, and lactobacilli, whereas most animals of control group had reduced lactic flora. On the other hand, abundant yeasts were detected from the cecum, colon, and feces of the control animals, but the levels were significantly lower in the animals given strain BIO-4R. The density of Salmonella in the intestine appeared to be reduced after the administration of strain BIO-4R. The number of BIO-4R cells was shown to be 10 times lower in the duodenum and jejunum than in the ileum, suggesting that strain BIO-4R might have grown transiently in the ileum. The similar trend toward stabilization of the lactic flora was also observed in cows after administration of BIO-4R. In addition, an antagonistic effect of the strain against yeasts and Salmonella was suggested. These findings indicate that the oral administration of strain BIO-4R is one of the useful methods whereby the potentially deleterious effect of antibiotics on the intestinal flora of farm animals may be minimized.     

Evidence that the multi-drug-resistance of Streptococcus faecalis BIO-4R is not carried by a plasmid.

The multi-drug-resistant strain Streptococcus faecalis BIO-4R was studied to see if it carried a plasmid responsible for antibiotic resistance. From results indicating that the antibiotic resistance of S. faecalis BIO-4R was not transferred to recipient bacteria, that the organism did not produce enzymes which inactivated antibiotics, and that the presence of covalently closed circular DNA was not demonstrated by dye-cesium chloride buoyant density gradient centrifugation, it was concluded that the organism did not carry such a plasmid. Studies on polyphenylalanine synthesis by cell-free extracts of the oganism showed that its ribosomes were resistant to chloramphenicol, tetracycline, streptomycin and kanamycin. These results, although rather indirectly, support the above notion that the multi-drug-resistance of S. faecalis BIO-4R is not mediated by a plasmid.     

Studies on the Establishment of Multi-Drug-Resistant Strain BIO-4R of Streptococcus faecalis in the Intestinal Tract of Germ-Free Mice

Germ-free ICR mice were mono- or dicontaminated with a multi-drug-resistant strain BIO-4R of Streptococcus faecalis (BIO-4R) and Escherichia coli 026 : K60 (E. coli) and administered aminobenzyl penicillin (ABPC). BIO-4R was established in the intestinal tract at a level of 10⁸ viable cells per gram of stool on the fourth day following oral inoculation and the BIO-4R population was stably maintained thereafter. The drug resistance of BIO-4R remained unchanged in the intestinal tract of gnotobiotes throughout the experiment. Highly resistant cells of E. coli were isolated from the feces of some dicontaminated mice after ABPC administration. However, it seems that the high resistance of these E. coli is not due to the transfer of resistance of BIO-4R to E. coli. All animals given a large amount of BIO-4R (10⁸ cells) per os survived throughout the study period of two weeks without symptoms.     

Effects of different starch sources on Bacillus spp. in intestinal tract and expression of intestinal development related genes of weanling piglets

The study was conducted to evaluate the effects of different starch sources on Bacillus spp. in intestinal tract and expression of intestinal development related genes of weanling piglets. Twenty-eight PIC male piglets were divided into four homogeneous groups according to initial body weight (similar birth and parity, weaned at 21 ± 1.5 days). Diets for the four treatments consisted of corn starch, wheat starch, tapioca starch and pea starch with the determined ratio for amylose to amylopectin of 0.21, 0.24, 0.12 and 0.52 respectively. Real-time quantitative polymerase chain reaction was applied to: (1) detect genomic DNA of Bacillus and to quantify the number of Bacillus in the intestinal tract chyme of piglets with the primers and probe which designed based on the 16S rRNA sequences of maximum species of Bacillus on GenBank; (2) measure the mRNA level of glucagon-like peptide 2 (GLP-2), insulin-like growth factors 1 (IGF-1) and epidermal growth factor (EGF) in duodenum, jejunum and ileum. Results showed that the number of Baciilus and the percentage based on all bacteria in the whole intestinal content of piglets fed pea starch was highest in all groups (P < 0.05). There was no significant differance on copy numbers for all bacteria and Bacillus in the whole intestinal tract of piglets between the corn starch group and wheat starch group (P > 0.05). In addition, the expression level of GLP-2, IGF-1 mRNA in jejunum and ileum of pea starch treatment (the high amylose/amylopectin ratio) were increased while the tapioca starch decreased their mRNA level significantly compared to other three treatments (P < 0.05). There was no significant difference for the mRNA level of EGF in each group. The present study revealed that high amylose/amylopectin ratio of starches significantly enhanced the numbers of Bacillus in all segments of intestine and the mRNA level of intestinal development related genes.     

Effect of cerulenin on Streptococcus faecalis macromolecular synthesis and cell division.

The antibiotic cerulenin has been used to study macromolecular synthesis and cell division in Streptococcus faecalis. The data suggest that lipid and lipoteichoic acid synthesis as well as cell number increase are affected prior to any observable effects on overall mass increase or DNA, RNA, protein, or peptidoglycan synthesis. Treatment with cerulenin of cultures growing at various rates and analysis of the subsequent cell divisions indicate that the antibiotic may block a cell cycle event that precedes the completion of chromosome replication by about 10 min.     

Effect of intestinal flora on megaenteron of mice.

CF#1 germfree (GF) and conventional (CV) mice as well as offspring of conventionalized GF (GF-CV) mice were orally inoculated with Escherichia coli 0115a, c: K(B), a causative agent of megaenteron in mice. Although CV and GF mice showed no clinical signs and survived, all of the GF-CV mice died with diarrhea by day 14 after inoculation. Thickened wall of the large intestine, microscopically showing proliferation of crypt type cells, was seen in GF and GF-CV mice but not in CV mice. In addition, in GF-CV mice, hemorrhage and severe erosion with marked inflammatory reactions were observed. While the inoculated E. coli could not colonize in CV mice, a level of 10⁸ cells/g feces was maintained in GF mice from day 1 after inoculation to the end of examination (on day 28) and in GF-CV mice from day 5 to the time of death. Newly prepared germfree (GF-CV-GF) mice obtained hysterectomy from GF-CV mice showed a low sensitivity as comparable to that in GF mice. On the other hand, ex-germfree mice produced by oral administration of feces of GF-CV mice showed severe infection as comparable to that seen in GF-CV mice. These results suggest that the intestinal flora may play roles both on protecting from the infection of pathogenic E. coli and on enhancing the infection.     

Effect of protein synthesis on plasmid maintenance in Streptococcus faecalis.

Plasmid-to-chromosome ratios in Enterobacteriaceae, upon interruption of protein synthesis by chloramphenicol, are either conserved or increased when measured by dye buoyant density centrifugation. We have found, on the other hand, that the effect of inhibition of protein synthesis on the amount of covalently closed circular deoxyribonucleic acid visualized by this method in two strains of Streptococcus faecalis appears to differ from these established systems. A three- to sixfold decrease in covalently closed circular deoxyribonucleic acid was observed when lysates of chloramphenicol-treated cultures were submitted to dye buoyant density centrifugation. A loss of covalently closed circular deoxyribonucleic acid was also evident from electrophoretic profiles of these lysates. Several conditions which could account for the apparent loss of covalently closed circular deoxyribonucleic acid upon inhibition of protein synthesis are discussed.     

Observations on the synthesis and destruction of tyrosine by Streptococcus faecalis R

Streptococcus faecalis R when grown in a double-strength medium rendered the medium deficient in folic acid and tyrosine. The organism was found to be capable of removing approximately ten times as much folic acid from the medium during the 24-hr. incubation period as it requires for maximum growth.Although Streptococcus faecalis R achieved maximum growth in the absence of added tyrosine if pyridoxal was present in the medium, the growth response obtained in the presence of tyrosine was proportional to the amount of tyrosine added at concentrations of tyrosine greater than 10 μ./10 ml. medium.Growth of S. faecalis R in the presence but not in the absence of pyridoxal caused a tyrosine deficiency to develop in the double-strength medium.     

肠道菌群对新生儿神经发育的影响

新生儿肠道菌群的定植和建立是一个复杂的动态演变过程,且易受分娩方式、喂养方式、胎龄、抗生素暴露等多种因素的影响。肠道菌群不仅在新生儿生理发育、免疫系统成熟、抵抗病原体入侵、维护肠道屏障等方面发挥重要作用,还影响神经回路的建立、髓鞘的形成和血脑屏障的形成。早期肠道菌群失调可导致新生儿坏死性小肠结肠炎、生长发育迟缓和智力发育落后等。近年来肠道菌群通过肠-脑轴影响新生儿神经发育受到广泛关注,其主要与代谢、免疫、迷走神经和神经内分泌等途径相关。本文主要就新生儿肠道菌群特征及其影响因素和肠道菌群对神经发育的影响作一综述。     

Effect of macromolecular synthesis and lytic capacity on surface growth of Streptococcus faecalis.

Exposure of exponential-phase cultures of Streptococcus faecalis to any of three inhibitors of protein synthesis was accompanied by an increase in the average distance that the cross wall extended into the cytoplasm. This resulted in: (i) an increase in the average surface area of the cross wall (Sa) and (ii) septation occurring in the envelope growth sites that were much smaller than the controls. However, although at the concentrations used, all three antibiotics inhibited protein synthesis and autolytic capacity to the same extent and with the same kinetics, cells treated with these agents showed large differences in the rate at which Sa values increased above those of the untreated cells. The largest increases in Sa were observed in cells that synthesized the least amount of cytoplasmic macromolecules (deoxyribonucleic acid, plus ribonucleic acid, plus protein). The observations were interpreted in terms of a model in which a decreased lytic capacity reduces the rate of splitting of the nascent cross wall into two layers of peripheral wall, preferentially using wall precursors to close open cross walls. However, the extent to which centripetal growth occurs would be inversely related to the rate at which cytoplasmic macromolecules are synthesized. In contrast, inhibition of deoxyribonucleic acid synthesis was accompanied by decreased extension of the leading edge of the cross wall into the cytoplasm, thus antagonizing septation. These findings are discussed in relation to the normal cell division cycle of S. faecalis.     

Recombination-deficient mutant of Streptococcus faecalis.

An ultraviolet radiation-sensitive derivative of Streptococcus faecalis strain JH2-2 was isolated and found to be deficient in recombination, using a plasmid-plasmid recombination system. The strain was sensitive to chemical agents which interact with deoxyribonucleic acid and also underwent deoxyribonucleic acid degradation after ultraviolet irradiation. Thus, the mutant has properties similar to those of recA strains of Escherichia coli.     

Genetic, molecular, and functional analysis of Streptococcus faecalis R plasmid pJH1.

Streptococcus faecalis JH1 contains two conjugative plasmids, pJH1, an R plasmid that codes for resistance to kanamycin, streptomycin, erythromycin, and tetracycline, and pJH2, a hemolysin-bacteriocin plasmid. Strain JH1 was used as an antibiotic resistance donor in conjugation experiments with two plasmid-free S. faecalis recipient strains, JH2-2 and OG1-RF1. Plasmid pJH1 was purified from one transconjugant, DL77, and subjected to restriction endonuclease analyses. Five restriction enzymes, EcoRI, XbaI, BamHI, SalI, and XhoI, yielding 10, 9, 3, 2, and 2 fragments, respectively, were used to determine the size (80.7 kilobases) of pJH1 and to construct a restriction endonuclease map of the plasmid. Twenty-eight percent of the antibiotic-resistant transconjugants examined expressed only part of the resistance pattern (Kmr Smr Emr Tcr) associated with pJH1, that is, they were resistant to kanamycin, streptomycin, and erythromycin; to erythromycin and tetracycline; or to erythromycin or to tetracycline only. Most of these strains also produced hemolysin and bacteriocin, and several contained a hybrid plasmid consisting of pJH2 and specific segments of pJH1 DNA. Several of these hybrid plasmids, as well as a deletion derivative of pJH1 that coded for resistance to tetracycline but not to kanamycin, streptomycin, or erythromycin, were purified and used to confirm the arrangement of restriction endonuclease fragments on the pJH1 map and to locate the resistance determinants on this map.     

Effect of lipoteichoic acid and lipids on lysis of intact cells of Streptococcus faecalis.

Autolysis of intact cells of Streptococcus faecalis was inhibited to a greater extent by phospholipids than by lipoteichoic acid, suggesting a possible difference in the accessibility of native autolysin to these substances.     

Effect of sulphasalazine on the human intestinal flora

Sulphasalazine is commonly used to treat patients with ulcerative colitis but the mode of action is still unexplained. To investigate a possible antibacterial effect of sulphasalazine, the faecal flora composition was studied in patients with ulcerative colitis and in mice harbouring a human intestinal flora. Patients on sulphasalazine were found to have an intestinal flora that was completely resistant to sulphapyri-dine. Oral administration of sulphasalazine did not influence the composition of the human flora in mice.