Biological properties of opportunistic microorganisms isolated from patients with acute intestinal diseases

The comparative study of the incidence of the pathogenicity markers (DNAase, RNAase, phosphatase and hemolytic activity) in shigellae and salmonellae, acknowledged as the causative agents of intestinal infections, and in opportunistic bacteria isolated from the feces of patients with acute intestinal diseases and healthy persons has been made. The study has revealed that DNAase and RNAase activity occurs most frequently in Shigella flexneri, in salmonellae and in opportunistic enterobacteria isolated from the intestinal contents of patients with acute intestinal diseases. In this respect they essentially differ from the same species of opportunistic enterobacteria isolated from healthy persons.     

Pathogenicity factors of opportunistic enterobacteria and its role in development of diarrhea

The data of pathogenicity factors of opportunistic enterobacteria, including Klebsiella, Enterobacter, Citrobacter, Proteus, Providencia and Hafnia species are submitted. The genetic control and a role of pathogenicity factors of opportunistic enterobacteria in development of diarrhea syndrome are presented. Data about adhesins, hemolysins, cytotoxic necrotizing factors and bacterial modulins are described. The characteristic of cytotonic and cytotoxic enterotoxins, including LT, ST, Shiga-like and cytolethal toxins, and mechanisms of diarrheagenic action are analysed. The role of bacterial lipopolysaccharide (endotoxin) and induction of locally synthesized proinflammatory cytokins in pathogenisis of diarrhea are discussed.     

Diagnostic effectiveness of nutrient media for the bacteriological detection of enterobacteria

The effectiveness of new nutrient media intended for the differential isolation of pathogenic and opportunistic enterobacteria (SS agar), as well as for the preliminary identification of enterobacteria, was determined on a wide range the strains of the family Enterobacteriaceae. The comparative evaluation of SS agar and Ploskirev's bactoagar was carried out. The newly developed medium was shown to have advantage in its differentiating and inhibiting properties. The clinical trials of the media, carried out in this study, revealed high detection rate and exceedingly exact differentiation of lactose-negative lactose-positive enterobacteria, as well as 100% coincidence of the results obtained on the nutrient medium for the preliminary identification of enterobacteria and on laboratory-made control media.     

Drug resistance of opportunistic enterobacteria isolated from various sources]

Resistance of 159 strains of opportunistic enterobacteria to 9 antibacterial drugs was studied. The strains were isolated from man and cattle. It was shown that the overwhelming majority of the isolates (93 per cent) were polyresistant irrespective of the genus. There was a high frequency of the strains resistant to the widely used antibiotics such as chloramphenicol (73 per cent), ampicillin (73.6 per cent) and rifampicin (95.6 per cent) and sulfanilamides (99.3 per cent). Gentamicin and nalidixic acid proved to be the most active against the cultures: 11.9 and 10 per cent of the resistant strains, respectively. The strains of enterobacteria isolated from different sources had a sensitivity to the antibiotics. Multiple antibiotic resistance to at least 5 drugs, variability of the spectra and high resistance were more characteristic of the isolates from the animals. The necessity of a rational use of antibacterial drugs in veterinary is indicated.     

Biological properties of opportunistic enterobacteria isolated from healthy persons and from patients with intestinal dysbacteriosis

The comparative study of the signs of pathogenicity in 724 enterobacterial strains and in some species of nonfermenting microorganisms isolated from the feces of 115 somatic patients with intestinal dysbacteriosis and 80 healthy persons (565 strains) has revealed that microorganisms belonging to the same species may essentially differ in their occurrence, in the activity of the enzymes (DNAase, RNAase, phosphatase) which they release into the culture medium, as well as in their capacity to give the positive reaction with Congo red. At the same time, the cultures isolated in cases of intestinal dysbacteriosis have been found to be biologically more active.     

Interrelations between Klebsiella ozaenae and other members of a microbial association in a pathological ozenous focus

The study of relationships between individual representatives of the microeubiosis at a pathological ozenous focus has shown that Gram-positive microorganisms and opportunistic enterobacteria are not antagonistic to K. ozaenae which, in their turn, do not affect the growth of opportunistic enterobacteria and Pseudomonas aeruginosa. The overwhelming majority of P. aeruginosa strains (92.9%) grown on a solid culture medium are characterized by a varying antagonistic activity with respect to K. ozaenae; this activity does not manifest if these organisms have been grown together in a liquid medium. P. aeruginosa culture fluid diluted 1:10 and 1:20 has not inhibited the multiplication of K. ozaenae. The data indicate the possibility of a prolonged coexistence of K. ozaenae with Proteus and P. aeruginosa, which is confirmed by many cases of simultaneous isolation of associations of these microbes from ozena patients. Thus the possibility appears of a combined pathogenic action of these bacteria on human body.     

Enterotoxigenic capacity of strains of Klebsiella and Enterobacter genera isolated in acute intestinal diseases in children

234 strains, including 104 K. pneumoniae strains, 28 K. oxytoxica strains, 64 E. cloacae strains and 40 E. aerogenes strains, have been isolated from the intestine of 266 children with diarrhea, aged up to 1 year, and studied for enterotoxigenicity. By the coagglutination test, made with G. Kronvall's staphylococcal reagent prepared with the use of antiserum to Escherichia coli LT-enterotoxin, and the biological assay on suckling mice enterotoxigenic activity has been revealed in 119 strains, including 48 K. pneumoniae strains (12.6%), 33 E. cloacae strains (27.4%) and 23 E. aerogenes strains (19.7%). The strains producing only LT-enterotoxins, only ST-enterotoxins, and both LT- and ST-enterotoxins have been found. The determination of the enterotoxigenic activity of the clinical isolates of opportunistic enterobacteria makes it possible to improve the etiological interpretation of acute intestinal infections.     

New <Emphasis Type="Italic">Bacillus subtilis</Emphasis> Strains as Promising Probiotics

The properties of new B. subtilis strains GM2 and GM5, isolated from potato rhizosphere and possessing high antimicrobial activity, were studied. The potential of the strains for their use as probiotics was characterized. The strains were resistant to bile and to a wide range of the ambient pH. B. subtilis strains GM2 and GM5 possessed proteolytic and phytate-hydrolyzing activity and proved to be safe for model animals. The strains were characterized by antagonistic properties against phytopathogenic micromycetes, as well as against pathogenic and opportunistic enterobacteria. B. subtilis GM2 and GM5 were concluded to be promising strains for use as probiotics.     

The Yersinia high-pathogenicity island: an iron-uptake island.

Highly pathogenic Yersinia carry a pathogenicity island termed high-pathogenicity island (HPI). The Yersinia HPI comprises genes involved in the synthesis of the siderophore yersiniabactin and can thus be regarded as an iron-uptake island. A unique characteristic of the HPI is its wide distribution among different enterobacteria such as Escherichia coli, Klebsiella, Citrobacter and Salmonella. Other types of iron-uptake systems are also carried by different pathogenicity islands in enterobacteria.     

The characteristics of the biological properties of Shigella dysenteriae 1 circulating in the USSR and India: its biochemical activity and agglutinability

The properties of 71 S. dysenteriae 1 strains isolated from patients in the USSR and India in 1986-1988 were studied. The cultures possessed typical biochemical and serological properties. As revealed in this investigation, high fastidiousness of this infective agent to the quality of synthetic nutrient could become the cause of false negative reactions in different substrates used for the identification of enterobacteria, thus leading to diagnostic mistakes. The variability of the biochemical activity of different strains with respect to arginine, glycerol, maltose and trehalose (as well as the stability of these signs) was regarded as the theoretical substantiation of the possibility, in principle, to work out the scheme for the subdivision of S. dysenteriae 1 into independent biochemical variants.     

The microbiological characteristics of intestinal dysbacteriosis in children and adults in the city of Moscow

The bacteriological analysis of 302 children has revealed that dysbacteriosis with the increased content of hemolytic Escherichia in the intestine develops more frequently in the presence of the deficiency of bifido- and lactobacteria. The development of other kinds of dysbacteriosis with the increased content of different opportunistic enterobacteria, staphylococci, enterococci and fungi, as well as dysbacteriosis with the decreased content of Escherichia, does not practically depend on the deficiency of bifido- and lactobacteria. In patients with the increased content of Escherichia an increase in the content of opportunistic enterobacteria, staphylococci and fungi is observed more frequently than in patients with the low content of Escherichia.     

Variability of the pathogenicity traits of populations of staphylococci in a surgical hospital

The results of the study of heterogeneity of staphylococcal populations at a surgical ward are presented. The study deals with qualitative and quantitative characteristics of three groups of pathogenicity factors: protease (the penetration factor), protein A (the function of protection from phagocytosis) and alpha-hemolysin (the toxic function). The study shows that the greatest number of S. aureus strains with a high content of protein A has been isolated from patients with postoperative and wound infections. On the basis of the data obtained in this study the groups of strains have been defined in accordance with the association of the signs of pathogenicity. These groups reflect pronounced heterogeneity of staphylococcal strains at a surgical ward.     

Fecal microflora in healthy young people

The study of the intestinal microflora in 119 young adults was carried out. A high content of anaerobic representatives of the intestinal microflora (bifido- and lactobacteria) and extremely wide fluctuations in the number of E. coli (1-5 million to 700-800 million cells per g of feces) were shown. The species composition of the facultative group was found to be variegated. Staphylococci, yeast, fungi, opportunistic enterobacteria, as well as Escherichia and cocci with changed characteristics were detected. 23.5% of the subjects showed a high content of E. coli (greater than 200 million cells per g of feces) accompanied by the increased occurrence of Klebsiella and Escherichia with changed properties. These persons can be regarded as a high risk group with a higher incidence of acute intestinal diseases with unknown etiology.     

Diagnostic value of individual tests for classification of Shigella]

A total of 1243 strains of enterobacteria were studied by four tests (mobility, lysis with dysentery polyvalent bacteriophage, relation to Christensen's citrate and salicin) for the purpose of determining shigellae genera. A combination of signs characteristic of Shigella genus was observed in 99.1% of laboratory and in 100% of freshly-isolated strains. No such combination was found in any other of the representatives of Enterobacteriaceae family. The tests under study are recommended for the work in practical laboratories to ascertain the reference to Shigella genus of cultures suspected of being Shigellae by the results of growth on combined medium (Olkenisky's, Kligler's, etc.).     

Impact of an urban effluent on antibiotic resistance of riverine Enterobacteriaceae and Aeromonas spp

In order to evaluate the impact of an urban effluent on antibiotic resistance of freshwater bacterial populations, water samples were collected from the Arga river (Spain), upstream and downstream from the wastewater discharge of the city of Pamplona. Strains of Enterobacteriaceae (representative of the human and animal commensal flora) (110 isolates) and Aeromonas (typically waterborne bacteria) (118 isolates) were selected for antibiotic susceptibility testing. Most of the Aeromonas strains (72%) and many of the Enterobacteriaceae (20%) were resistant to nalidixic acid. Singly nalidixic acid-resistant strains were frequent regardless of the sampling site for Aeromonas, whereas they were more common upstream from the discharge for enterobacteria. The most common resistances to antibiotics other than quinolones were to tetracycline (24.3%) and beta-lactams (20.5%) for Enterobacteriaceae and to tetracycline (27.5%) and co-trimoxazole (26.6%) for Aeromonas. The rates of these antibiotic resistances increased downstream from the discharge at similar degrees for the two bacterial groups; it remained at high levels for enterobacteria but decreased along the 30-km study zone for Aeromonas. Genetic analysis of representative strains demonstrated that these resistances were mostly (enterobacteria) or exclusively (Aeromonas) chromosomally mediated. Moreover, a reference strain of Aeromonas caviae (CIP 7616) could not be transformed with conjugative R plasmids of enterobacteria. Thus, the urban effluent resulted in an increase of the rates of resistance to antibiotics other than quinolones in the riverine bacterial populations, despite limited genetic exchanges between enterobacteria and Aeromonas. Quinolone resistance probably was selected by heavy antibiotic discharges of unknown origin upstream from the urban effluent.     

Etiological structure of acute intestinal infections caused by opportunistic bacteria in young children

Altogether 587 children with diagnosed acute enteric infections were examined. In 26.4% of them pathogenic enterobacteria were detected, and in 59%, opportunistic enterobacteria. In 38.2% of children these bacteria were found to be the etiological factor of the disease. A reverse relationship between the contamination of feces with pathogenic enterobacteria and the age of children was established.     

Normalization of the increased translocation of endotoxin from gram negative enterobacteria (leaky gut) is accompanied by a remission of chronic fatigue syndrome

There is now evidence that chronic fatigue syndrome (CFS) is accompanied by an increased translocation of endotoxins from gram-negative enterobacteria through the gut wall, as demonstrated by increased prevalences and median values for serum IgM and IgA against the endotoxins of gram-negative enterobacteria. This condition can also be described as increased gut permeability or leaky gut and indicates intestinal mucosal dysfunction (IMD). Here we report a case of a 13 year old girl with CFS who showed very high values for serum IgM against the LPS of some enterobacteria and signs of oxidative and nitrosative stress, activation of the inflammatory response system, and IgG3 subclass deficiency. Upon treatment with specific antioxidants and a "leaky gut diet", which both aim to treat increased gut permeability, and immunoglobins intravenously, the increased translocation of the LPS of gram negative enterobacteria normalized and this normalization was accompanied by a complete remission of the CFS symptoms.     

Characteristics of nonpathogenic Neisseria and Branhamella catarrhalis based on cytopathogenicity

The study of the action of 12 Neisseria species belonging to 112 strains, 6 B. catarrhalis strains and 202 meningococcal strains on the culture of continuous cell line F1 (human amniotic cells) has revealed that nonpathogenic Neisseria are essentially weaker than meningococci in their pathogenicity (expressed in terms of CPD50). Among nonpathogenic Neisseria highly cytopathogenic strains occur in 13.9% of cases, which gives grounds for considering them opportunistic bacteria. Sharply pronounced correlation between the adhesive and pathogenic properties of Neisseria has been observed. The cytopathogenic action of Neisseria is accompanied by the lesion of the chromosomal apparatus of mitotic infected cells.     

Inhibitory effects of various micro-organisms on the growth of Helicobacter pylori

AIMS: To examine the in vitro influence of various bacteria species on Helicobacter pylori (Hp) growth. METHODS AND RESULTS: The effects of 29 micro-organisms on 31 Hp strains were determined using two modified 'cross streak' methods. Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Morganella morganii, Serratia marcescens, Bacteroides fragilis, Fusobacterium nucleatum and Clostridium difficile showed the strongest inhibition. The inhibitory effects varied, depending on the bacteria spp. and Hp strains, and were method dependent. The cagA status of Hp strains did not correlate with the extent of inhibition. CONCLUSIONS: Helicobacter pylori is inhibited by a significant number of commensal bacteria species as well as opportunistic human pathogens. The success and progress of Hp infection may be influenced by the bacterial flora present, while the difficulty in cultivating Hp from the oral mucosa and faeces may be the result of antagonistic bacterial interaction. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides valuable data on the sensitivity of Hp to a variety of intestinal and oral commensals as well as opportunistic human pathogens. Hp's varying pathogenicity and the specific localization of infection may be the result of these sensitivities. These results can also serve as a basis for further studies to identify the inhibitory substances and make them available for therapeutic use.     

Interrelation of the enterotoxigenic properties and the antigenic structure of Escherichia

The enzymatic signs and serological characteristics of Escherichia enterotoxigenic strains isolated from patients with acute intestinal diseases and from healthy persons were studied. The cultures were subdivided into 24 enzymatic variants and classified with 48 serogroups and 61 serovars. The enterotoxigenic properties of the strains were compared with their serological characteristics and enzymatic signs. The strains, isolated from different persons and classified with the same serovar, belonged to the same variant with respect to the type of enterotoxin they produced (only thermostable enterotoxin, only thermolabile enterotoxin, or both), were similar in the degree of their toxigenicity and belonged, as a rule, to the same enzymatic variant. The data on the presence of manifest interrelation between the enteropathogenicity of Escherichia and their structure, as well as on the stability of the enterotoxigenic properties of these organisms, indicate that in acute intestinal diseases the determination of Escherichia enterotoxigenic strains can be carried out by common bacteriological techniques with the use of specific agglutinating sera.