Effect of normal microflora of female reproductive tract in colonization resistance

The role of female reproductive tract microflora in the maintenance of biotope colonization resistance was described. The role of lactobacilli possessing antagonistic properties in the reproductive tract defense was assessed. Classification of bacterial mechanisms of colonization resistance including block of the adhesion, antagonistic action of normal microflora associated with the production of antibacterial substances and suppression of allochthonous bacteria persistence characteristics was presented. Colonization resistance was considered as a physiological phenomenon of microecological homeostasis being a result of symbiotic relations of a host organism and autochthonous microflora.     

Microbial ecology of the vagina

In this review recent information on relationships between the vaginal environment and microflora, including new taxonomic groups of microorganisms, is updated. The role of normal microflora in formation of vaginal colonization resistance and possible participation of some representatives of normal microflora, mainly nonsporulating anaerobic organisms, in the development of perinatal, neonatal and gynecological infectious complications are considered.     

The microbial colonization of the skin of newborn infants rooming in with the mother in maternity homes]

The formation of skin biocenosis in children under the conditions of a maternity hospital with the joint care of mother and child was studied with the use of commercial bacteriological imprints manufactured in the USSR. The colonization of newborn infants in maternity hospitals with opportunistic, saprophytic and normal microflora was established. In newborn infants aged up to 5 years low skin resistance to colonization and, as a consequence, frequent colonization of the skin with opportunistic and saprophytic microflora was observed.     

Biological characterization of ecovars of gram-negative bacteria circulating in the burn ward

In 44 isolated cultures of Gram-negative bacteria, besides commonly known pathogenicity factors, their adhesive activity towards the cells of the buccal epithelium and their interrelations with the representatives of normal microflora which determine natural resistance to colonization have been studied. The artificial adhesion of target cells is accompanied by the inhibition on the natural colonization of epithelial cells by Streptococcus salivarius; it is, therefore, evident that adhesiveness is one of the factors which determine the behavior of microorganisms in cenoses. The circulation of adhesive strains of Gram-negative bacteria has been noted in the burn ward.     

Effect of new antimicrobial agents on the ecological balance of human microflora

The human normal microflora is relatively stable at each ecological habitat under normal circumstances and acts as a barrier against colonization by potentially pathogenic microorganisms and against overgrowth of already present opportunistic microorganisms. Administration of antimicrobial agents causes disturbances in the ecological balance between the host and the normal microflora. The risk of emergence and spread of resistant strains between patients and dissemination of resistant determinants between microorganisms is reduced if colonization resistance is not disturbed by antimicrobial agents. In this article, the potential ecological effects of administration of new antimicrobial agents on the intestinal and oropharyngeal microflora are summarized. The review is based on clinical studies published during the past 10 years.     

Rapid diagnosis of dysbacteriosis by detecting beta-aspartylglycine in the feces in an experiment

In experiments on Fischer rats (F-344), both with common microflora and germ-free, the influence of the systemic destination of different antibiotics (tetracycline + ampicillin, gentamicin + kefzol, gentamicin, fradizine) on the intestinal microflora, the content of beta-ospartylglycine in feces and the colonization resistance of the intestinal tract to Staphylococcus aureus B-243 and Pseudomonas aeruginosa No. 93 has been studied. The early appearance of beta-aspartyl-glycine in the supernatant of fecal samples has been shown to be the first sign of dysbacteriosis and to indicate the decrease of the colonization resistance of the intestine to opportunistic bacteria.     

Microbial colonization and succession on the faucial mucosa in newborn infants rooming in with their mothers in a maternity hospital]

The formation of microflora on the laryngeal mucosa in newborn infants during the first 5 days of their life was studied in one of the maternity hospitals of Moscow. In this work modern methods of the isolation and identification of aerobic and anaerobic microorganisms were used, and the results thus obtained were computer-processed. In the maternity hospital of the "mother-child" type the microbial colonization of the laryngeal mucosa by normal and opportunistic microorganisms was noted in newborn infants. A wave-like course of the formation of laryngeal microflora, indicative of microbial succession occurring in the child, was revealed. The attempt to establish the cases of microbial interference between the species colonizing the laryngeal mucosa revealed that it was very rarely observed in 5-day-old newborns. This feature was seemingly the cause of low resistance of the larynx to colonization in newborn infants, which determined frequent colonization of their laryngeal mucosa with Staphylococcus aureus and Klebsiella.     

The use of a rat-derived microflora for providing colonization resistance in SPF rats

To obtain a suitable species-specific microflora for a new rat SPF-unit, germ-free WAG/Rij rats were associated with a flora derived originally from selectively decontaminated Cpb: WU (Wistar) rats. Caecal and ileal contents of these rats had been cultured anaerobically (37 degrees C) for 7 days and harvested. This cultured flora was given to germ-free Cpb: SE (Swiss) mice, which were kept in an isolator system and acted as a source of the flora to associate germ-free Wag/Rij rats. In these associated rats, several parameters indicative of the 'quality' of the intestinal microflora were investigated and compared to those in rats with a mouse derived anaerobic microflora. Parameters included relative caecal weight, colonization resistance and the concentration of faecal bile acids. The cultured rat-derived microflora normalized the observed intestinal parameters better than the mouse derived microflora, and provided better colonization resistance. We conclude that culturing of intestinal contents of selectively decontaminated animals can be a useful way to obtain a species-specific donor-microflora which can be used to start new SPF units.     

The characteristics of the colonization resistance of the intestines in conventional animals with a history of clinical death]

After modeling the terminal state caused by the acute loss of blood in rats their intestinal microflora was studied, as was their resistance to colonization. Decreased resistance to colonization was registered early after resuscitation (up to 3 days), which was confirmed by the translocation of bacteria into internal organs, decreased number of lactobacilli in the contents of the small intestine and elevated level of enterobacteria in the intestine. Disturbances in resistance to colonization was also manifested by prolonged colonization of the digestive tract of the resuscitated animals by Escherichia coli indicator strain K12pSS-120 carrying Shigella sonnei (phase I) invasiveness plasmid.     

Microbial colonization and succession in the large intestine of newborn infants during their stay with mothers at the maternity hospital]

Formation of microflora in the large intestine of 5-day old infants was studied in one of the Moscow maternity homes. The up-to-date procedures for isolation and identification of aerobic and anaerobic organisms were used in the study and the findings were processed on a computer. In the newborns of the maternity home of the "mother-infant" type there was observed colonization of the large intestine with aerobic and anaerobic organisms. A wave-like dynamics in the formation of the symbiotic microflora was revealed. It reflected the phenomenon of the microbial succession in the infants. The attempts to detect microbial interference between the species colonizing the large intestine showed that it was extremely rare in the 5-day old infants. This was likely the reason of the low intestine resistance to the colonization in the newborns which in its turn defined the frequent colonization of the intestine mucosa with S. aureus and the organisms of the Klebsiella, Enterobacter and Citrobacter group.     

Anaerobic microflora of the female reproductive tract

The microflora of the female reproductive tract is very diverse and plays an important role in both normal and pathological states. The data on the mechanisms of colonization resistance which involve the vaginal microbios (the production of H2O2, organic acids, bacteriocin-like substances, competition for adhesion sites) are presented. The data on the role of individual antagonistically active substances of anaerobic bacteria in suppressing gonococci, fungi, microorganisms, associated with bacterial vaginosis, etc. are given. The leading role of anaerobic microorganisms in the appearance of microecological disturbances, including bacterial vaginosis, is emphasized. The role of the pathogenic properties of anaerobic bacteria for the development of different pathological processes, such as premature birth, postnatal and postoperative purulent septic diseases, inflammation of pelvic organs, cancer of the neck of uterus, is discussed.     

Clostridium difficile-associated typhlitis in specific pathogen free guineapigs in the absence of antimicrobial treatment

Clostridium difficile (toxin) associated typhlitis was diagnosed in untreated barrier-maintained specific pathogen free guineapigs. It resembled the pathological lesions of antibiotic induced enterocolitis. The possible role of limited colonization resistance to C. difficile provided by mouse enteric microflora in the pathogenesis of the disease is discussed.     

Vaginal microbiocenosis in trichomoniasis

Taxonomic complex of vaginal microflora and its persistence characteristics in trichomoniasis and microecological disturbances were studied. Diminution of biotope colonization resistance was characterized by decreased autochthonous microorganisms' number and increased opportunistic microflora with expressed persistence. That could be of a great pathogenetic importance in the occurrence of reproductive tract inflammatory diseases of the bacterial etiology in addition of trichomoniasis in females.     

Microbial biocenosis of the nasal mucosa in healthy persons and in Staphylococcus carriers

The normal microflora of the nasal mucosa in man is differentiated into main, complementary and casual microflora, taking into account its isolation rate and characteristics of microbial contamination. The main microflora of adults, in contrast to children, is represented, in addition to coagulaso-negative (CN) staphylococci, by bacteria of the genus Corynebacterium. In staphylococcal carrier state a decrease in the isolation rate and the amount of bacteria belonging to the main and complementary microflora (CN staphylococci, Micrococcus, Streptococcus, Bacillus) was observed. Moreover, in carriers the weakening of the degree of association between CN staphylococci, Micrococcus, Corynebacterium, Streptococcus in symbiotic pairs was noted. In the absence of S. aureus carrier state the main and complementary microflora was characterized by the combination of the factors of antagonism and persistence, while in carrier state the complex of colonization factors was defective in the main microflora and well pronounced in coagulase-positive staphylococcal strains and enterobacteria.     

Microbial ecology of laboratory animals as a model in evaluation of the immunomodulating and antimicrobial agents]

Rats with altered microbial ecology and decreased colonization resistance due to neutropenia induced by cyclophosphamide were used as a model for estimating the effect of bacterial polysaccharides (lactulose and exopolysaccharide from Bacillus polymyxa) and fluoroquinolones (pefloxacin). Monotherapy with pefloxacin had a favourable effect both on normalization on the intestinal microflora in the rats and their hemopoiesis (decreased neutropenia). The highest correcting effect with respect to the lowered colonization resistance was observed when pefloxacin was used in combination with exopolysaccharide.     

Microbial ecology and a retrospective assessment of the possibility of predicting an outbreak of suppurative meningitis caused by a Serratia marcescens strain in a hospital for the nursing care of premature infants]

An outbreak of purulent meningitides in a hospital ward for preterm babies, caused by Serratia marcescens strain of serovar 05/13 with multiple resistance, is described. Data on the results of the long-term observation of the ward showed that during three months preceding the outbreak the consecutive spread of the infective strain and its colonization of the intestine of children occurred. At the moment of the outbreak S. marcescens 05/13 was the dominating intestinal microflora in 37% of children in the ward and constituted 30% of the total aerobic flora in the intestine of the examined children. No S. marcescens strains were isolated from the feces and urine of the medical personnel and mothers. The importance of the observation of microflora colonizing newborn infants in the ward for the evaluation and prognostication of the epidemiological situation is discussed.     

Colonization of Beef Cattle by Shiga Toxin-Producing Escherichia coli during the First Year of Life: A Cohort Study

Each year Shiga toxin-producing Escherichia coli (STEC) are responsible for 2.8 million acute illnesses around the world and > 250,000 cases in the US. Lowering the prevalence of this pathogen in animal reservoirs has the potential to reduce STEC outbreaks in humans by controlling its entrance into the food chain. However, factors that modulate the colonization and persistence of STEC in beef cattle remain largely unidentified. This study evaluated if animal physiological factors such as age, breed, sex, and weight gain influenced the shedding of STEC in beef cattle. A cohort of beef calves (n = 260) from a multi-breed beef calf population was sampled every three months after birth to measure prevalence and concentration of STEC during the first year of life. Metagenomic analysis was also used to understand the association between the STEC colonization and the composition of gut microflora. This study identified that beef calves were more likely to shed STEC during the first 6 months and that STEC shedding decreased as the animal matured. Animal breed group, sex of the calf, and average weight gain were not significantly associated with STEC colonization. The metagenomic analysis revealed for the first time that STEC colonization was correlated with a lower diversity of gut microflora, which increases as the cattle matured. Given these findings, intervention strategies that segregate younger animals, more likely to be colonized by STEC from older animals that are ready to be harvested, could be investigated as a method to reduce zoonotic transmission of STEC from cattle to humans.     

Significance of hydrobiont persistent properties for symbiotic interactions

Significance of symbiotic relations formed by associative symbiosis type for autochthonous and allochthonous microflora of natural water bodies is shown. Generality of symbiotic interaction mechanisms of symbionts in limnetic and halophilous communities provided by secreted factors of natural resistance from the side of the host, and by factors of persistence from the side of symbionts is proven based on a set of examples. Features of operation of lysozyme-antilysozyme, histon-antihiston, hydrogen peroxide-catalase functional systems in symbiotic interactions of autotrophic and heterotrophic components of hydrobiocenosis with dominant and associative microflora are presented. Associative microflora of allochthonous origin was shown to actively use the ecologically formed system of interaction between hydrobionts that facilitates survival of these microorganisms and preservation of their persistent potential, and as a result leads to biocenosis disorders. The knowledge obtained open new possibilities and perspectives of research of sanitary and ecological aspects of vital activity of aquatic biocenoses.     

Role of neutrophils in the regulation of the reproductive tract microbiocenosis in women

The influence of neutrophils and their secretory products on the microflora of the vaginal contents in healthy women and in women having dysbiotic processes in the vagina was studied. The secretory products of neutrophils were found to produce a bactericidal effect on the representatives of the opportunistic bacteria, this effect being less pronounced with respect to lactic-acid bacteria. The established effect of neutrophils on bacteria is regarded as one of the mechanisms of microbiocenosis formation, ensuring colonization resistance.     

Symbiotic relations of humans and microorganisms

Symbiosis is considered to be the biological basis of the infectious process. Particular attention is paid to the change of paradigm in symbiology and the introduction of a new term, associative symbiosis. The main structural-functional elements of associative symbiosis are estimated, and three vectors of the infectious process are distinguished: (1) host-normal flora, (2) host-associants, and (3) associants-indigenous microflora (microsymbiocenosis). The functions of microsymbionts that determine the colonization resistance of the host and the formation of dysbioses and pathobiocenoses are discussed. The phenomenon of microbial self-nonself recognition is determined on the basis of the opposite (increase/decrease) effects on the growth and persistent (including biofilm formation) characteristics of the dominant-associant pair under the conditions of microsymbiocenosis in humans. Material is presented to characterize the role of intercellular interactions of the symbionts at the level of prokaryotes and pro-eukaryotes under the conditions of infectious pathology.