Production of and sensitivity to colicins among serologically classified strains of Escherichia coli

A significant proportion of 242 serologically classified strains of Escherichia coli of human origin produced colicins (33%) or were inhibited by one or more of six standard colicins (57%). The most common colicins identified were E1, I, and B; colicins B and V had greatest range of activity. Generally, neither the production of, nor sensitivity to, individual colicins was restricted to strains of a single serogroup. The coexistence of strains of one serogroup that were sensitive to the action of a colicin produced by strains of another serogroup was encountered among 2 of 21 fecal specimens containing strains of multiple serogroups. The production of colicins was not a major determinant in the acquistion of, or subsequent changes in, strains of E. coli in the feces of 10 newborn infants.     

Effect of bile on the lipid composition and surface properties of bifidobacteria

AIM: The changes produced on the bacterial surface of Bifidobacteria cells when they are grown in bile were compared with those provoked by bile added to bacteria grown in the absence of bile. METHODS AND RESULTS: The adhesive properties, the zeta potential and the lipid composition of Bifidobacterial strains, isolated from human faeces and grown in MRS medium, were determined. Bacteria grown in MRS with bile showed a loss of adherence and autoaggregation in correlation with a decrease in the surface hydrophobicity in comparison to those grown in MRS without bile, concomitant with the absence of two glycolipids, the increase of sugar content and minor changes in fatty acid composition. The surface changes caused by bile shock on bacteria grown in bile-free medium were much less pronounced and, in addition, no effect on the lipid composition was apparent. CONCLUSIONS: The comparison of the results indicates that bile action on surface properties is related to metabolic changes. SIGNIFICANCE AND IMPACT OF THE STUDY: Long-term exposure of bacteria to bile may cause metabolic changes affecting their adhesive properties irreversibly. This may be taken as a criterion to define the probiotic properties of different strains.     

Isolation and characterization of Lactobacillus salivarius MTC 1026 as a potential probiotic

Researchers are becoming more interested in studying probiotics at present due to their benefit to human and animal health. In this study, newly isolated strains from human feces were evaluated for probiotic properties. A total of sixty isolated strains were collected from feces and six out of sixty isolated strains could inhibit the growth of Salmonella typhi and Salmonella typhimurium. The strain which gave the best inhibitory effect was selected for further characterization as a probiotic strain. The identification of this strain was analyzed on the basis of morphological and biochemical characteristics and 16S rDNA gene sequence. This strain was Gram-positive, rod shaped, and catalase and oxidase-negative, and produced acids from D-glucose, D-fructose, lactose, mannitol, sorbitol, inulin and starch. It could not hydrolyze esculin or red blood cells. Based on its 16S rDNA gene sequence, it was Lactobacillus salivarius, and so was called L. salivarius MTC 1026 in this study, and was closely related with L. salivarius DSPV 344T isolated from the calf gut. It was able to survive in gastric and small intestinal juices at pH 2.0 and 1.0% bile salt for several hours and also could grow at 45°C. Moreover, this strain showed inhibitory activity against a variety of food-borne pathogens. It was highly sensitive to piperacillin, chloramphenicl, ampicillin, erythromycin and ceftazidime. After plasmid curing, this strain was susceptible to gentamicin, amikacin, norfloxacin and ciprofloxacin. L. salivarius MTC 1026 could significantly inhibit the adhesion process of E. coli ATCC 25922 and S. typhimurium ATCC 13311 on Caco-2 monolayers in a competition assay and also reduced invasion of both pathogens (4-log cfu/ml) in an exclusion and displacement assay. Therefore, it was clearly demonstrated in this study that L. salivarius MTC 1026 has shown promising properties as a candidate for a potential probiotic for applications in humans and animals.     

Enterotoxic properties of salmonellae and their neurotoxins

Most of live S. typhimurium cultures are capable of intraintestinal proliferation and possess enterotoxic activity. The capacity of S. typhimurium strains for producing enterotoxins is not connected with their origin. The parenteral immunization of rabbits with corpuscular vaccines prepared from S. typhimurium induced changes in the sensitivity of different sections of the small intestine of the animals to the enterotoxic action of live homologous cultures. Neurotoxin isolated from S. typhi was found to possess enterotoxic activity.     

A comprehensive evaluation of the biological properties of the causative agents of typhoid fever isolated from patients and carriers

The biological properties of 106 S. typhi cultures were studied; of these, 59 cultures were isolated from 45 chronic carriers and 47 cultures, from 23 typhoid fever patients. According to the degree of their virulence (CPD50 in the continuous cell-line culture Hep-2), the strains isolated from the patients were more virulent than those isolated from the chronic carriers. The mean value of lg CPD50 was 5.76 +/- 0.04 for the patients and 6.86 +/- 0.03 for the chronic carriers. The strains isolated from the patients showed greater variability in the degree of their virulence. The study of the plasmid spectrum showed that 9.4 +/- 5.6% of the strains contained plasmids. From the patients plasmid-containing strains were isolated more frequently than from the carriers (14.9 +/- 2.5% and 5.1 +/- 2.9%). Multiresistance to antibiotics in combination with the presence of plasmids was detected in 6 strains isolated from the typhoid patients with morbidity having the character of outbreaks.     

DNA uptake in competent Streptococcus pneumoniae requires ATP and is regulated by cytoplasmic pH

We analyzed the ability of 120 encapsulated strains of B. fragilis to agglutinate guinea pig and human red blood cells. Sixteen strains showed a strong hemagglutination (HA) ability, 21 strains a moderate HA ability, 7 strains a weak HA ability and 74 strains did not agglutinate the tested red blood cells. Six strains tested from each HA group were able to adhere to cheek epithelial cells and to a cultured human intestinal cell line. Hemagglutinating strains were the most adhesive. By electron microscopy, pilus-like structures were found in three of the encapsulated adhesive strains. Treatment of the bacterial cells with pronase E reduced both HA ability and adherence of piliated encapsulated, and of piliated non-encapsulated strains. Glucosidase treatment of cells reduced HA activity and adherence of piliated encapsulated and of non-piliated encapsulated strains. Finally, it was found that hemagglutinating strains are more frequently isolated from clinical specimens (55%) than from feces of healthy donors (20%).     

Hemagglutinating and adhesive capacities of Klebsiella and Enterobacter strains

The authors analyze the data of studies on the hemagglutinating and adhesive capacity of 290 cultures, including 118 K. pneumoniae strains and 64 E. cloacae strains isolated from sick children, as well as 59 K. pneumoniae strains and 49 E. cloacae strains isolated from healthy children. The hemagglutinating properties of the strains were determined in the hemagglutination test with fresh, formalin- and tannin-treated red blood cells, the adhesive properties were studied by light microscopy. Among K. pneumoniae and E. cloacae strains isolated in acute intestinal infections, mannose-sensitive hemagglutination and pronounced adhesive activity were prevalent in most cases. Poorly adhesive and nonadhesive strains were characteristic of K. pneumoniae and E. cloacae cultures isolated from healthy children. The strains isolated from sick and healthy children differed only by the prevalence of adhesive cultures.     

沙门菌CWDMs乳酸脱氢酶同功酶的观察

采用聚丙烯酰胺凝胶电泳法检测伤寒杆菌和甲型副伤寒杆菌的ＣＷＤＭｓ及其宁代细菌型和伤寒杆菌粗糙型的乳酸脱氢酶（ＬＤＨ）同功酶,以了解沙门菌ＣＷＤＭｓ生物氧化的特点和机制,探讨ＣＷＤＭｓ变异的性质。结果表明,伤寒杆菌和甲型副伤寒杆菌的细菌型及伤寒杆粗糙型在聚丙烯酰胺凝胶电泳后显示出相同的４种具有不同泳动速率的ＬＤＨ同功酶,但ＣＷＤＭｓ仅显示２种ＬＤＨ。ＣＷＤＭｓ的２种ＬＤＨ同功酶与其亲代细菌型及伤寒杆     

R plasmid distribution in S. typhi isolated on the territory of the left coast of the Ukraine in 1970-1982

A total of 373 strains of S. typhi isolated in 1970-1982 were tested with respect to their sensitivity to 9 antibiotics active against gram-negative bacteria. It was shown that about 1/3 of the isolates were resistant to 1-3 antibiotics. Among the resistant isolates the number of strains resistant to 4-5 and more antibiotics amounted to 12.5 per cent. The plasmid nature of the antibiotic resistance in the isolated strains of S. typhi was shown. Transmissive R plasmids were detected in 13 per cent of the strains studied. Within the last 5 years there was an increase in the proportion of strains with transmissive R plasmids in patients with sporadic typhoid fever or especially in groups of patients with the disease.     

Escherichia coli bacteriocins: antimicrobial efficacy and prevalence among isolates from patients with bacteraemia

Bacteriocins are antimicrobial peptides generally active against bacteria closely related to the producer. Escherichia coli produces two types of bacteriocins, colicins and microcins. The in vitro efficacy of isolated colicins E1, E6, E7, K and M, was assessed against Escherichia coli strains from patients with bacteraemia of urinary tract origin. Colicin E7 was most effective, as only 13% of the tested strains were resistant. On the other hand, 32%, 33%, 43% and 53% of the tested strains exhibited resistance to colicins E6, K, M and E1. Moreover, the inhibitory activity of individual colicins E1, E6, E7, K and M and combinations of colicins K, M, E7 and E1, E6, E7, K, M were followed in liquid broth for 24 hours. Resistance against individual colicins developed after 9 hours of treatment. On the contrary, resistance development against the combined action of 5 colicins was not observed. One hundred and five E. coli strains from patients with bacteraemia were screened by PCR for the presence of 5 colicins and 7 microcins. Sixty-six percent of the strains encoded at least one bacteriocin, 43% one or more colicins, and 54% one or more microcins. Microcins were found to co-occur with toxins, siderophores, adhesins and with the Toll/Interleukin-1 receptor domain-containing protein involved in suppression of innate immunity, and were significantly more prevalent among strains from non-immunocompromised patients. In addition, microcins were highly prevalent among non-multidrug-resistant strains compared to multidrug-resistant strains. Our results indicate that microcins contribute to virulence of E. coli instigating bacteraemia of urinary tract origin.     

Characterization of Intestinal Lactobacillus reuteri Strains as Potential Probiotics

This study was conducted to evaluate the probiotic properties of Lactobacillus reuteri isolated from human infant feces (less than 3?months). Out of thirty-two representative L. reuteri strains isolated from the infant human feces, nine isolates (i.e. LR5, LR6, LR9, LR11, LR19, LR20, LR25, LR26 and LR34) showed survival in acid, bile and simulated stomach?Cduodenum passage conditions, indicating their high tolerance to gastric juice, duodenal juice and bile environments. The nine isolates did not show strong hydrophobic properties because the percentages of adhesion to the apolar solvent, n-hexadecane, did not exceed 40%, showing that their surfaces were rather hydrophilic. Functionality of these nine probiotic isolates was supported by their antagonistic activity and their ability to deconjugate bile salts. The safety of the nine indigenous L. reuteri isolates was supported by the absence of transferable antibiotic resistance determinants, DNase activity, gelatinase activity and hemolysis. The results obtained so far suggest that the nine strains are resistant to low pH, bile salts and duodenum juice, so they could survive when passing through the upper part of the gastrointestinal tract and fulfill their potential probiotic action in the host organism. According to these results, the L. reuteri strains isolated from human infant feces possess interesting probiotic properties that make them potentially good candidates for probiotics.     

The adhesive activity of diphtheritic strains in relation to the characteristics of the infectious process they induce]

The degree of adhesiveness of 602 C. diphtheriae strains isolated from patients with different forms of diphtheria was studied on trypsinized sheep red blood cells (SRBC) used as an experimental model. The titer of bacterial suspension, i.e. its highest dilution ensuring the agglutination of 50% of SRBC, was assumed to be the index of adhesive activity. The toxigenic strains were more homogeneous with respect to the degree of their activity and proved to be moderately and highly adhesive, while among the nontoxigenic strains faintly and moderately adhesive ones prevailed. The degree of adhesiveness was not linked with the cultural biological strains variants, but depended on the form of C. diphtheriae infection. The toxigenic strains isolated from diphtheria patients were essentially more active than those isolated from carriers. Both toxigenic and nontoxigenic strains isolated in cases of prolonged carrier state (more than 4 weeks) did not differ in the degree of their adhesiveness and were essentially more active than the strains isolated from short-term carriers. The strains circulating in 10 closed groups with a high proportion of pronounced cases of carrier state (70.6% to 86.7%) were essentially more active than those circulating in 10 similar groups, but having a low proportion of pronounced cases of carrier state (6.7% to 23.8%). The conclusion was made that the degree of adhesiveness proved to be an important factor of C. diphtheriae pathogenicity, responsible for the formation of carrier state. Along with pathogenicity, this factor should be taken into consideration in the evaluation of the epidemiological importance of different sources of infection.     

The adherence of lactic acid bacteria to the columnar epithelial cells of pigs and calves

The adhesion of various lactobacilli and streptococci to columnar epithelial cells of pigs and calves were studied, by in vitro methods. The porcine strains isolated most frequently were Lactobacillus delbrueckii, Lact. acidophilus and Lact. fermentum. Thirteen of the 22 lactobacilli were adhesive. All the streptococci isolated belonged to Lancefield's D-group; none of them adhered to pig epithelial cells. The adhesive strains (9 of 22) of calves were identified as Lact. fermentum. Adherence was variable even between strains of the same species. Isolates from plant material, cultured milk and cheese did not adhere to the columnar epithelial cells in vitro. The adhesive porcine strains tolerated low pH and bile acids, which is important for their survival under conditions in the stomach and intestine.     

Characterization of the RpoS status of clinical isolates of Salmonella enterica

The stationary-phase-inducible sigma factor, sigma(S) (RpoS), is the master regulator of the general stress response in Salmonella and is required for virulence in mice. rpoS mutants can frequently be isolated from highly passaged laboratory strains of Salmonella: We examined the rpoS status of 116 human clinical isolates of Salmonella, including 41 Salmonella enterica serotype Typhi strains isolated from blood, 38 S. enterica serotype Typhimurium strains isolated from blood, and 37 Salmonella serotype Typhimurium strains isolated from feces. We examined the abilities of these strains to produce the sigma(S) protein, to express RpoS-dependent catalase activity, and to resist to oxidative stress in the stationary phase of growth. We also carried out complementation experiments with a cloned wild-type rpoS gene. Our results showed that 15 of the 41 Salmonella serotype Typhi isolates were defective in RpoS. We sequenced the rpoS allele of 12 strains. This led to identification of small insertions, deletions, and point mutations resulting in premature stop codons or affecting regions 1 and 2 of sigma(S), showing that the rpoS mutations are not clonal. Thus, mutant rpoS alleles can be found in freshly isolated clinical strains of Salmonella serotype Typhi, and they may affect virulence properties. Interestingly however, no rpoS mutants were found among the 75 Salmonella serotype Typhimurium isolates. Strains that differed in catalase activity and resistance to hydrogen peroxide were found, but the differences were not linked to the rpoS status. This suggests that Salmonella serotype Typhimurium rpoS mutants are counterselected because rpoS plays a role in the pathogenesis of Salmonella serotype Typhimurium in humans or in the transmission cycle of the disease.     

The adhesive properties of a nonenteropathogenic strain of Escherichia coli in systems in vitro on isolated rat enterocytes and in vivo

The adhesive properties and colonizing capacity of E. coli strain O83, isolated from feces of healthy humans and marked according to its resistance to rifampicin and nalidixic acid, were studied. In vivo experiments on germ-free rats revealed that these bacteria were capable of colonizing intestinal mucosa; colonization increased from the small to large intestine and E. coli cells were mainly concentrated in the intestinal lumen and in mucin. In vitro studies showed that this nonenteropathogenic E. coli strain possessed pronounced adhesive properties with respect to the colonic cells of germ-free rats; these properties were considerably less pronounced with respect to the enteric cells of the small intestine. The electron microscopic study of E. coli cells revealed the presence of fimbriae and fibrillae on their surface.     

News & Notes: Adhesiveness of Bacteroides fragilis Strains Isolated from Feces of Healthy Donors, Abscesses, and Blood

Bacteroides fragilis strains attached to oral epithelial cells (ECs) and the cell line Intestine 407 and associated with human phagocytes with different efficiencies depending on their source. The 58%, 75%, and 40% of strains isolated from feces, abscesses, and blood respectively adhered to ECs with good efficiency (11–40 bacteria/cell). Of the strains from feces and abscesses, 17% and 20% exhibited a high adherence (>40 bacteria/cell); however, none of the blood isolates presented this property. Similar results were obtained with the cell line Intestine 407 and human phagocytes. Of the isolates from feces, abscesses, and blood, 20%, 56%, and 71% respectively also exhibited hemagglutination ability, indicating that this property is a virulence trait more frequently present among pathogenic isolates than in commensal strains.     

Sensitivity of Shiga toxin-producing Escherichia coli (STEC) strains for colicins under different experimental conditions

Twenty Escherichia coli strains producing well-characterised colicins were tested for their inhibitory activity against five Shiga toxin-producing E. coli (STEC) strains using different media under aerobic and anaerobic conditions. The five STEC strains used were of serotype O26, O111, O128, O145 and O157:H7 which are frequently isolated serotypes associated with disease in humans. The main route of infection for humans is through the eating of badly cooked or handled beef. The major reservoir for STEC strains in cattle is the rumen. To mimic the situation in the rumen of cattle, overlay assays were also performed under anaerobic conditions in the presence of 30% rumen fluid. Colicins E1, E4, E8-J, K and S4 are most active against STEC strains under anaerobic conditions in the absence or presence of rumen fluid. These colicins will be used in future experiments with the aim to eradicate the presence of STEC in cattle.     

Biochemical and serologic study of Acholeplasmae isolated from monkeys

Biochemical and serological properties of mycoplasmas isolated from the blood, feces and parenchymatous organs of monkeys have been studied to determine their species. It was established that the isolated strains belong to the family Acholeplasmatoceae. The study of their biochemical properties in different tests has revealed the presence of 5 biochemically heterogeneous groups. Their serological properties suggest that 13 out of 45 strains are identical to the reference strain of A. laidlawii A, and all other strains have been classified as new Acholeplasma species which have never been isolated from monkeys before.     

Invasiveness of Salmonella typhi strains in HeLa S3 monolayer cells

The internalization and intracellular multiplication, i.e., the invasiveness, of Salmonella typhi strains recently isolated from typhoid fever patients were confirmed in HeLa cell monolayers. When stained with Giemsa solution, intracellular bacteria were 0.6 X 1.2 micron in size and stained purple, whereas extracellular bacteria associated or not with the HeLa cell surface were 1.0 X 3.0 micron and stained deep blue. Strain GIFU 10007 was internalized into 23% of the HeLa cells within 10 min after inoculation. About 90% of the HeLa cells were infected after 24 hr incubation in kanamycin (KM)-containing medium. Intracellular multiplication of the challenge organism was verified by a large number of intracellular bacteria after 24 hr incubation in KM-containing medium by both light-microscopy of the Giemsa stained preparation and viable counts of intracellular bacteria. The viable counts of strain 10007 showed an increase of more than 40-fold within 24 hr after inoculation, whereas in the four other less or non-infective strains, recovery of viable bacteria was poor or nil. Strains which were highly invasive usually failed to show strong adhesion. The contribution of Vi antigen to the internalization of challenge organisms was not proved. Infective strains, when killed by formalin were still adhesive, but were not internalized. The same strains, when killed by boiling, were neither adhesive nor internalized. From these findings it was concluded that the internalization and multiplication of infective S. typhi strains in cultured HeLa cells should be regarded as an invasion rather than phagocytosis by host cells, and such invasiveness could be an indicator to estimate the virulence of S. typhi strains.