[FORMATION OF POPULATION MORBIDITY WITH SALMONELLOSIS CAUSED BY SALMONELLA ENTERITIDIS IN REGIONS WITH INCOMPLETE SUPPLY OF LOCAL POULTRY PRODUCTS]

AIM

Study plasmid characteristics of S. enteritidis strains in patients and features of epidemi- ology of the infection in regions with incomplete supply of population with local poultry produc- tion.

MATERIALS AND METHODS

Plasmid analysis of microbe strains isolated from 382 patients and 8 samples of products was carried out, and significance of plasmid types in population morbidity was evaluated. Identification of salmonella was carried out by conventional methods, plasmid 41 specter - by Kado C.I. and Liu S.T (1981) method.

RESULTS

98.4% of strains contained virulence plasmid p38, and 80.1% of strains also had small plasmids. Sakhalin strains were divided into 16 plasmid types (D=0.794), and strains from Jewish AO - 10 (D=0.834). Uniformity of strains in patients during infection outbreaks and in transmission factors was detected.

CONCLUSION

Features of salmonellosis in. the studied subjects of Russian Federation are determined by higher risk of import of products containing salmonella. Monitoring based on plasmid analysis is an effective base for epidemiologic control.

Morphogenesis of Experimental Infection Caused by Plasmid Variants of Yersinia pseudotuberculosis

The dynamics of pathomorphological changes in response to infection with plasmid variants of Yersinia pseudotuberculosis was studied in experimental animals. Variability of cell injuries in pseudotuberculosis histopathology depended on the plasmid-associated virulence of the infection agent. Infection with highly virulent two-plasmid strain pYV48:pVM82 MDa and Y. pseudotuberculosis strain with low virulence with the only plasmid pVM82 MDa led to the development of cell destruction (necrosis and apoptosis) in the target organs. Apoptosis predominated in response to infection by plasmid variant pVM82 MDa with low virulence.

[PLASMID-ASSOCIATED VIRULENCE OF YERSINIA PSEUDOTUBERCULOSIS AND INFECTIOUS PROCESS]

Literature data regarding genetically-determined pathogenicity factors of Y pseudotuberculo- sis and associated manifestations of this infection caused by various plasmid types of the causative agent are generalized. Principal attention is given to features of cell-tissue alterations mediated by virulence plasmid pYV, as well as effects of pathogenicity of an understudied pVM82 plasmid present only in Y pseudotuberculosis sttains causing clinical-epidemic manifestation of the infec- tions as Far East scarlet-like fever (FESLF). The data obtained on the ability of far-eastern strains to produceYPMa super-antigenj Ypseudotuberculosis-derivative mitogenA, probablygive evidence on its key role in FESLF pathogenesis. Variability of damage of innate immunity cells and target- organs caused by various plasmid types of Y pseudotuberculosis by virulence could determine polymorphism of clinical-morphological manifestations of this infection. In-depth understanding of dependency of immune pathogenesis mechanisms of the disease on molecular characteristics of the causative agent opens up-perspectives of enhancement of diagnostics and prognosis of the severity of the course of pseudotuberculosis and yersiniosis in human in general.

[Effect of phenol on Yersinia pseudotuberculosis bacteria cultivated in various media]

AIM

Study of bactericidal effect of phenol on Yersinia pseudotuberculosis produced in various nutrient media.

MATERIALS AND METHODS

Bacteria were produced in nutrient broth (NB) and NB with glucose (NB+Glu) or galactose (NB+Gal) at 8 degrees C. Effect of phenol on bacteria was evaluated by changes in optical density of suspension and quantity of viable cells, and by staining of cells with ethidium bromide. Lipids were analyzed by thin-layer and gas-liquid chromatography, gas-liquid- chromatography--mass-spectrometry, differential scanning calorimetry; lipopolysaccharides (LPS)--by electrophoresis in polyacrylamide gel in the presence of sodium dodecylsulfate (SDS-PAGE).

RESULTS

Survival rate of bacteria is dependent on phenol concentration, biocide treatment time and parameters of cell cultivation. Addition of glucose or galactose into the nutrient medium increases the resistance of Yersinia against phenol. Bacterial cultures are heterogeneous in the resistance against phenol independently of the production parameters. Phenol causes damage in outer bacterial membrane, as evidenced by accumulation of lysophosphatidylethanolamine in the cell, the main product of enzyme activity of membrane-bound phospholipase A, and release into the cultural medium of part of LPS. Treatment by phenol in bactericidal concentration is accompanied by changes in phospholipidic and fatty acid composition of bacterial cell envelope.

CONCLUSION

New data are obtained on environmental factors that contribute to the increase of resistance of bacteria against phenolic biocides.

[Oxygen deficiency increases invasive activity and resistance of Yersinia pseudotuberculosis to heat stress]

AIM

To study effects of oxygen availability and presence of glucose in growth medium on adhesive and invasive properties of Yersinia pseudotuberculosis as well as its resistance to heat stress during sharp rise of temperature from 8 degrees C to 37 degrees C.

MATERIALS AND METHODS

Yersinia pseudotuberculosis was grown on nutrient broth with or without glucose at 8 degrees C and two regimen of aeration--during intensive stirring (180 rpm) and without it. Adhesive and invasive activities were studied on the model of HeLa human cell line. Effects of temperature stress on the bacterial growth were assessed from growth curves plotted on the basis of quantity of colony-forming cells. Morphology of bacterial cells was studied by electron microscopy.

RESULTS

It was shown that cultivation of Y. pseudotuberculosis at 8 degrees C and low aeration increases its adhesive and invasive activity as well resistance to heat stress. Adding of glucose to growth medium decreases invasiveness of Y. pseudotuberculosis irrespective to aeration regimen.

CONCLUSION

Oxygen deficiency during low temperature of growth promotes increasing of pathogenic potential of Y. pseudotuberculosis. Obtained data are useful for solving practical problems associated with development of prevention measures for pseudotuberculosis as well with food processing and storage.

[Contribution of I.V. Tarasevich to the study of tsutsugamushi disease]

This article summarizes the results of study of tsutsugamushi disease in the Primorye and Tadzhikistan, in its epidemiology, diagnosis and biology of the Rickettsia tsutsugamushi. There is also information on the vectors of the disease, rickettsial infection within chiggers and transtadial transmission from larva to nymph, hosts of trombiculids and natural infection with R. tsutsugamushi.

[Epidemiologic and etiologic characteristic of enterovirus infections in Khabarovsk region]

Results of epidemiologic, virologic, and serologic studies of enterovirus infections in Khabarovsk region from 1975 to 2006 were analyzed. Patterns of epidemic process of these infections were established: periodic change of dominating type of pathogen in the population; onset of the large epidemic peaks of incidence during emergence of circulation of new for the given area serotypes of enteroviruses; possibility of realization of several routes of virus transmission. Role of water factor in the progress of the epidemic process was revealed. Etiology of the large epidemic rise of aseptic meningitis incidence in Khabarovsk region in 2006 was established--the leading pathogens were ECHO viruses serotypes E6 and E30.

[Thermotropic behavior of lipids and the morphology of Yersinia pseudotuberculosis cells with a high content of lysophosphatidylethanolamine]

The content of lysophosphatidylethanolamine (LPE) in Y. pseudotuberculosis cells was found to increase during their growth at 8 degrees C under stationary conditions (without stirring the medium) and at 37 degrees C when the medium contained glucose. The maximum level of LPE (up to 45% of the total phospholipids) was observed in cells grown at 8 degrees C under stationary conditions. Such cells showed an enhanced growth rate, a reduced yield of biomass, an altered cell morphology, and an increased cell area. The cells contained unsaturated fatty acids, phosphatidylethanolamine (PE), and total phospholipids in small amounts, whereas neutral lipids and diphosphatidylglycerol were abundant. In addition, the cells contained an amount of methylated PE and phospholipids of unknown structure. Irrespective of whether the temperature for growth was low or high, the LPE-rich cells showed a high value (32-36 degrees C) of the maximum temperature of thermal transition of lipids (Tmax). This finding is indicative of a densification of the membrane lipid matrix of the LPE-rich cells. The suggestion is made that LPE is accumulated in glucose-fermenting bacterial cells in response to stress caused by oxygen deficiency and low pH values of the growth medium. The possible relationship between LPE accumulation and the virulence of Y. pseudotuberculosis cells grown at low temperatures is discussed.

[Influence of glucose and galactose on the morphology and biological properties of Yersinia pseudotuberculosis]

When cultivated in the presence of glucose, irrespective of temperature and the degree of aeration, Y. pseudotuberculosis cells have the ovoid form, constant size and low hydrophobic properties of their surface. Meanwhile the characteristics of the bacteria grown in the medium, carbohydrate-free or with galactose added, essentially depend on the conditions of medium aeration. Under the conditions of intensive stirring at both temperatures these bacteria acquire the coccoid form, not typical for Yersinia, they have a smaller area (approximately 2 times) and more hydrophobic surface in comparison with the cells grown in the presence of glucose. Under stationary conditions the differences between the cells, cultivated in the presence of galactose and glucose, in form and area disappear, but the differences in the hydrophobic properties of the surface are retained. As revealed in this study, the cells grown in the presence of galactose and under the conditions of intensive medium stirring, in contrast to those grown with glucose, have 1.5-fold greater invasive activity, irrespective of aeration conditions, eightfold greater resistance to ampicillin and twofold greater resistance to streptomycin and erythromycin.

Geographical heterogeneity between Far Eastern and Western countries in prevalence of the virulence plasmid, the superantigen Yersinia pseudotuberculosis-derived mitogen, and the high-pathogenicity island among Yersinia pseudotuberculosis strains

Yersinia pseudotuberculosis produces novel superantigenic toxins designated YPMa (Y. pseudotuberculosis-derived mitogen), YPMb, and YPMc and has a pathogenicity island termed HPI (high-pathogenicity island) and R-HPI (the right-hand part of the HPI with truncation in its left-hand part) on the chromosome. Analysis of the distribution of these virulence factors allowed for differentiation of species Y. pseudotuberculosis into six subgroups, thus reflecting the geographical spread of two main clones: the YPMa(+) HPI(-) Far Eastern systemic pathogenic type belonging to serotypes O1b, -2a, -2b, -2c, -3, -4a, -4b, -5a, -5b, -6, -10, and UT (untypeable) and the YPMs(-) HPI(+) European gastroenteric pathogenic type belonging to serotypes O1a and -1b. The YPMa(+) HPI(+) pathogenic type belonging to serotypes O1b, -3, -5a, -5b, and UT and the YPMb(+) HPI(-) nonpathogenic type belonging to non-melibiose-fermenting serotypes O1b, -5a, -5b, -6, -7, -9, -10, -11, and -12 were prevalent in the Far East. The YPMc(+) R-HPI(+) European low-pathogenicity type belonging to non-melibiose-fermenting serotype O3 and the YPMs(-) HPI(-) pathogenic type belonging to 15 serotypes were found to be prevalent all over the world. This new information is useful for a better understanding of the evolution and spread of Y. pseudotuberculosis.

Effects of culture method and growth phase on free lipid composition of Yersinia pseudotuberculosis

The influence of culture method (free-floating cells in liquid nutrient broth or bacteria attached to agar surface on solid agarized medium of the same formulation) and bacterial age on the composition of free lipids in Yersinia pseudotuberculosis (O:Ib serovar, strain KS 3058) grown in the cold (5 degrees C) has been investigated. The specific growth rate of the bacteria on solid medium was about threefold less than that in liquid medium. The qualitative composition of phospholipids and fatty acids only slightly depended on the bacterial culture method. At the same time, the colonially growing cultures contained somewhat more total lipids, they synthesized more phospholipids, in the linear growth phase they contained more lysophosphatides, and they had higher fatty acid unsaturation index and higher pathogenic potential than their "planktonic" counterparts grown in otherwise identical conditions. The bacterial growth phase influenced the amount of 3-hydroxytetradecanoic acid and, indirectly, that of lipopolysaccharide. The dynamics of changes in the amount of this acid with bacterial age was opposite in the surface and broth cultures.

[The effect of fluoroquinolones on the adhesive properties of different plasmidovars of Yersinia pseudotuberculosis]

The effect of fluoroquinolones such as ciprofloxacin, pefloxacin and norfloxacin on adhesion of Yersinia pseudotuberculosis was studied. It was shown that the effect of the fluoroquinolones was different: decreasing or increasing. The same effect was also observed in the closely related strains of Y. pseudotuberculosis. In the strains not dominating in the polyclonal population the adhesion decreased under the effect of the fluoroquinolones. In the strains of the dominant clones the effect on the adhesion was not single valued.

Decreased prevalence of Orientia tsutsugamushi in trombiculid mites and wild rodents in the Primorye region, Far East Russia

The isolation of Orientia tsutsugamushi was attempted from 249 rodents and approximately 14,000 trombiculid mites captured in the Primorye region, Far East Russia in 1993 and 1994, where high infection rates were recorded in both rodents and mites in the 1960s. However, no rickettsia was isolated from the samples. Low antibody titers against O. tsutsugamushi were detected in 7.1% of the rodents. These results indicate that the prevalence of O. tsutsugamushi in the Primorye region has decreased considerably in the past 30 years.

Genetic diversities of hantaviruses among rodents in Hokkaido, Japan and Far East Russia

Seroepizootiologic surveys among wild rodents were carried out in Japan and Far East Russia in 1995 and 1996. Seropositive animals were only identified in Clethrionomys rufocanus (23/134) in Hokkaido, Japan. On the other hand, seropositives were identified in C. rufocanus (1/8), Apodemus agrarius (2/66), Apodemus spp. (2/26) and Microtus fortis (3/22) in Vladivostok, Far East Russia. Total RNA was isolated from lungs of seropositive animals and the S genome segments were amplified by PCR, cloned and sequenced. The S and M genomes of hantavirus, derived from Japanese C. rufocanus (Tobetsu genotype), were most closely related with Puumala viruses (76-79% nucleotide and 95% amino acid identities for S genome, 70-78% nucleotide and 87-92% amino acid identities for M genome). The recombinant nucleocapsid protein of Tobetsu genotype was antigenically quite similar with that of Sotkamo. These suggest that the virus endemic in Japanese C. rufocanus belongs to Puumala virus. Phylogenetic analysis indicates that the genotype forms a distinct lineage within Puumala viruses. Partial S segment (1-1251 nt), derived from seropositive M. fortis in Vladivostok, was sequenced and analyzed. The S genome segment, which was designated Vladivostok genotype, was most closely related with Khabarovsk virus (79% nucleotide and 90% amino acid identities) which was isolated from M. fortis.

Putative origin of Yersinia pseudotuberculosis in western and eastern countries. A comparison of restriction endonuclease analysis of virulence plasmids

Yersinia pseudotuberculosis isolates from Russia east of Moscow, Korea and mainland China were used for restriction endonuclease analysis of virulence plasmid (REAP) and findings were compared with REAP of isolates from Japan and Western countries. An identical REAP pattern of each serogroup 1a, 1b, 3, 4a and 4b strain was observed among isolates from Russia, Korea, mainland China, and Japan but such was absent in West European strains. Therefore, the possibility that the origin of Y. pseudotuberculosis between West Europe and eastern Eurasia east of Moscow may be from a different clone should be considered.

[The epidemiological aspects of a pseudotuberculosis polyclonal infection]

The plasmid profile of 489 Y. pseudotuberculosis strains, serovar 1b, isolated from patients during 23 outbreaks and in sporadic cases of the disease were studied. As revealed in this study, in foci with the heterogeneous population of Y. pseudotuberculosis, serovar 1b, outbreaks and sporadic cases of the disease were caused by the polyclonal population of the microorganism. The study showed that three types of outbreaks could be differentiated, depending on the clonal characteristics of the microorganism causing these outbreaks and the presence of the dominating clone of the causative agent. Y. pseudotuberculosis infection caused by the combination of several clones of the microorganism was designated as polyclonal infection.

[The comparative characteristics of the Salmonella serotypes rarely encountered in the Maritime Territory]

The results of the comparative study of the phenotypical properties and the plasmid profile of 63 strains of salmonellae, belonging to 44 serotypes of groups B, C1, C2, C3, D, E1, E4, F. The study revealed that strains of different serotypes had their individual plasmid profile. Strains of the same serotype of salmonellae isolated from similar sources had an identical plasmid profile, while strains isolated from different sources differed in their plasmid profiles, though they might have a similar phenotype. Plasmid analysis was shown to be an effective method for the intraspecific typing of rarely isolated Salmonella serotypes and suitable for use as the basis of the microbiological monitoring of salmonellae.

[Yersinia pseudotuberculosis sensitivity to fluoroquinolones and the efficacy of pefloxacin in experimental pseudotuberculosis]

The sensitivity of Y. pseudotuberculosis of different origin and plasmid profile to Russian preparations of the ftoroquinolones group (cyprofloxacin, pefloxacin, norfloxacin) was studied. Of the 3 preparations under study, pefloxacin was found to be most active with respect to Y. pseudotuberculosis. The absence of relationship between antibiotic resistance in 4 Y. pseudotuberculosis strains to cyprofloxacin, pefloxacin and norfloxacin and their additional conjugative R-plasmid with molecular weights of 32 and 38 mD was noted. Pefloxacin was shown to give a good sanitation and protective effect in experimental pseudotuberculosis.

[Elimination of virulence plasmids of Yersinia pseudotuberculosis as affected by fluoroquinolones]

Pefloxacin, ciprofloxacin and norfloxacin were shown to induce elimination of the virulence plasmids in the strains of Y. pseudotuberculosis. Pefloxacin had a more pronounced eliminating effect than ciprofloxacin and norfloxacin. The elimination of the virulence plasmids with the molecular weight of 40-50 MD in the strains of Y. pseudotuberculosis was more frequent at the subinhibitory concentrations of the fluoroquinolones or at 1/4 of the fluoroquinolone MIC., At 1/8 of the MIC it was rarer. The virulence plasmid elimination in the strains was observed in spite of their serovar but was more frequent in the serovar 1B strains.

[Comparative study of the antimicrobial activity of pefloxacin, ciprofloxacin, norfloxacin and azithromycin with respect to Strains of Yersinia pseudotuberculosis]

Ciprofloxacin (C), pefloxacin (P) and norfloxacin (N) had a marked effect on Yersinia pseudotuberculosis strains isolated from the infected humans and animals. The activity of C (MIC 0.0312-0.125 microgram/ml) was higher than that of P and N (MIC 0.0625-2.0 micrograms/ml). The isolates were resistant to azithromycin (MIC 3.1-100 micrograms/ml). The susceptibility of the strains did not depend on the source of their isolation. The polyresistant strains carrying the R plasmids preserved the susceptibility to the fluoroquinolones.

[Sensitivity of Yersinia pseudotuberculosis to pefloxacin]

Pefloxacin susceptibility of 27 Yersinia pseudo-tuberculosis isolates from the infected humans and animals (serovars 1a and 1b with different plasmid spectra) was studied by the method of two-fold serial dilutions in the liquid medium. The culture was incubated at a temperature of 37 degrees C for 48 hours. It was shown that all the isolates were highly susceptible to the antibiotic. The MIC was 0.0625-1.0 microgram/ml and did not depend on the source of the strain isolation.

Restriction endonuclease analysis of virulence plasmids for molecular epidemiology of Yersinia pseudotuberculosis infections

Restriction endonuclease analysis of virulence plasmid DNA was used to study the epidemiology of Yersinia pseudotuberculosis infections. The origin of Y. pseudotuberculosis could be divided into two focus areas: Eastern Asia and Europe. Wild animals were an important reservoir for the Y. pseudotuberculosis seen in infections in humans.

[Yersinia L-transformation in experimental pseudotuberculosis]

An experiment on guinea pigs infected with virulent Y. pseudotuberculosis has revealed for the first time that in the host body Yersinia cells undergo ultrastructural changes, characteristic of L-transformation. These changes are manifested by damages in the cell wall and peptidoglycan layer of bacteria, dramatic expansion of the peri-plasmatic space, appearance of spheroplast bacterial cells. Myelin-like structures are formed around dead bacteria. These changes reveal one of the possible mechanisms which may render Yersinia harmless in convalescent patients, as well as contribute to the development of relapses of Y. pseudotuberculosis infection.

[Alternative localization of the determinant of pathogenicity coded by the Yersinia pseudotuberculosis pVM82 plasmid]

The chromosomal DNA regions in Yersinia pseudotuberculosis strains occur that are homologous to 25 Md DNA segment of the plasmid pVM82 encoding the bacterial capability of immunosuppression. The character of the chromosomal DNA regions dispersion reacting with the 25 Md segment probes is different in epidemiologically hazardous and nonvirulent strains of Yersinia pseudotuberculosis. The specific DNA regions occur as well as identical ones. The suppression of antibody formation to a number of main Yersinia pseudotuberculosis antigens by epidemiologically hazardous strain is demonstrated. The suppression is analogous to the one previously described for Yersinia pseudotuberculosis strains harbouring the plasmid pVM82.

[Analysis of the plasmid composition of Yersinia pseudotuberculosis strains and its use for typing pseudotuberculosis pathogens]

Electrophoresis in agarose gel has been used to study the plasmid spectra of 854 Yersinia pseudotuberculosis strains isolated from different sources. The plasmids found in the microbial strains are represented by the elements with molecular masses 82; 57; 45; 5.5; 4.4; 3.5; 2.7; 2.4; 2.3 Md. The variable spectra of plasmids is peculiar only for serovar I of Yersinia pseudotuberculosis. Plasmids p45 and p82 are classified as the main, while other plasmids as auxiliary ones. In accord with the classification all plasmid containing strains are divided into 8 plasmid strains. Using the proposed method for intraspecific typing of Yersinia pseudotuberculosis permits one to perfect the epidemiological analysis of pseudotuberculosis infection and make concrete the direction of prophylactic and antiepidemic measures.

[Integration with the chromosome--an alternative state of calcium-dependency plasmids in Yersinia]

Using the technique of the genes probes the naturally occuring strains Y. pseudotuberculosis and Y. enterocolitica of epidemiological importance were shown to contain pCad plasmid integrated with the chromosome. The strains having integrated plasmid express all pathogenicity determinants necessary for realization of infectious process.

[Various characteristics of Yersinia pseudotuberculosis determined by plasmid 45 Md associated with calcium dependence]

The clones of two types (T+ and T-) have been identified among the strains of Y. pseudotuberculosis. The difference in the morphology of the clones is based on the ability of T+ clones to agglutinate in the process of growth. The identified clones are different in calcium dependence, in the ability to agglutinate and in their virulence for the laboratory animals. The differences have been proved to be connected with the presence of a 45 Md plasmid in T+ cells. Replication of this plasmid is suppressed by the acridine orange dye in concentrations of 12.5 or 25.0 mkg X ml-1. The plasmid is spontaneously lost from the strains during their continuous storage. The microscopy of colonies permits the selection of clones with the parental phenotype from the populations having lost the 45 Md plasmid.

[Yersinia pseudotuberculosis plasmids and their significance in the realization of the epidemic process in pseudotuberculosis]

The results obtained in the electrophoretic study of the plasmid spectra of 190 Y. pseudotuberculosis strains, isolated from different sources, in 0.6% agarose gel are presented. 11 types of plasmids differing in their molecular weight have been detected. Plasmids with a molecular weight of 45 MD determine Ca2+ dependence, bacterial virulence for white mice and autoagglutination. The presence of differences in Y. pseudotuberculosis strains of serovars I, III and IV has been established, which is manifested by their differing plasmid spectra. The relationship between the presence of plasmids with a molecular weight of 75 and 45 DM in the strains and the character of pseudotuberculosis morbidity in the population has been demonstrated. The epidemic course of infection correlates with the presence of both these plasmids and the sporadic course of infection, with the presence of the plasmid with a molecular weight of 45 MD only.

[Natural focal infections in the north of the Far East. I. The detection of natural foci of infections in Chukot]

Results of a 3-year complex (zoo-parasitological, viral, bacteriological, and serological) studies of mammals and birds in Chukotka demonstrated the presence of natural foci of pseudo-tuberculosis, intestinal yersinosis, salmonellosis (heidelberg), and of tick-borne encephalitis. The existence of natural foci of tularemia and endemic rickettsioses is supposed on the basis of serological data.

[Tsutsugamushi fever in the Kuril Islands]

The authors present the results of a 6-year study of tsutsugamushi fever at the Kuril islands. The area of the disease proved to include Southern Kuril islands - Shikotan and Kunashir. The principal natural carriers of tsutsugamushi among the mouse-like rodents and trombiculidae larvae were revealed; highly virulent strains were found to prevail among the tsutsugamushi rickettsia strains. Tsutsugamushi fever in the population is characterized by a benign course, pyrexia, primary affects and lymphadenitis.