Study of the methylation process and DNA methylase specificity in Shigella]

The nature and content of minor bases in DNA of 3 Shigella strains are investigated. DNAs from Shigella stutzeri 2, Sh. sonnei 1188 and Sh. sonnei 311 are found to contain 0.43, 0.56 and 0.45 mol.% of N6-methyladenine respectively. 5-methylcytosine (0.16 mol.%) is discovered in Sh. sonnei 311. Substrate specificity of adenine methylase from Sh. sonnei 1188 with respect to phage DNAs of different host modification is investigated. Recognition sites for guanine methylase of DDVI phage and for adenine methylase of Sh. sonnei 1188 turned to be different. DNA of DDII phage grown in Sh. stutzeri 2 cells does not accept methyl groups under the treatment with Sh. sonnei 1188 extracts, but it is methylated by Escherichia coli extract. Adenine methylases of Sh. sonnei 1188 and Sh. stutzeri 2 are suggested to be either the same enzyme, or enzymes, which recognition sites are partially overlapped.     

Nature of the epidemic process in Sonne and Flexner dysenteries and the causes of its induction

A comparative study of the epidemic process in Sh. sonnei and Sh. flexneri dysentery in different regions of the USSR revealed that the morbidity level of Sh. sonnei dysentery changed simultaneously in the regions under study at intervals of 2-3 years. Sh. flexneri dysentery showed morbidity rises occurring at intervals 6-8 years, and their occurrence did not coincide with the periods of elevated morbidity in Sh. sonnei dysentery. The data obtained in the cohort analysis and in the study of recurrent morbidity suggest that Sh. flexneri dysentery produces more pronounced postinfection immunity than Sh. sonnei dysentery, and the immunological factor probably affects the dynamics of the epidemic of these Shigella infections.     

Differential characteristics of the I and II phases and R-form of Sh. sonnei]

Characteristics of various phases of Sh. sonnei were determined on the standard strains of Sh. sonnei of phases I and II and R-form used for the industrial production of agglutinating monoreceptor sera. Bacteria of phase I displayed a distinct morphological, cultural and serological differences. For the differentiation of Sh. sonnei of the II phase and R-form, representing the greatest difficulty in this respect, it is recommended to use phages RFfm and 6-SR, and also indirect immunofluorescence method with the application of agglutinating monophasic serum against the II phase of Sh. sonnei. In addition, a study was made of over 20 various Sh. sonnei strains at different dissociative process phases. Verification data completely confirmed the specificity of phages RFfm and 6-SR for Sh. sonnei in the II phase. The efficacy of the immunofluorescence method was confirmed on 6 strains.     

Recurrent Sonne dysentery morbidity caused by Shigella of varying enzymatic types]

The proportion of repeated cases of dysentery caused by Sh. sonnei does not exceed 3.59% of the total number of bacteriologically confirmed cases of this infection. The frequency of reinfection depended on the enzymatic type of the causative agent. The rarest cases of reinfection were those occurring after the primary infection with Sh. sonnei, biochemical type 2, whereas the most frequent after the primary infection with Sh. sonnei, type 3. Reinfection with heterologous Sh. sonnei was registered mostly 6-12 months after the primary infection, and with homologous Sh. sonnei after a 1 year and later.     

Tendencies in the epidemic process of dysentery in Ryazan

In shigellosis caused by Sh. sonnei and Sh. flexneri the epidemic process was found to have considerable difference in the tendencies and pace of its development. Shigellosis which dominated in the etiological structure at the period following 1966 was dysentery caused by Sh. sonnei; it showed the tendency towards a decrease in morbidity rate. Dysentery caused by Sh. flexneri was second in respect to the frequency of its occurrence after 1966 and showed the tendency towards increase. The simultaneous circulation of Sh. sonnei and Sh. flexneri, the differences in the epidemiology of these types of shigellosis make it imperative that they be studied separately, taking into ccount their etiological selectivity to the main routes of transmitting the infection.     

Use of intraspecific differentiation of Sh. sonnei for the purpose of studying patterns in the epidemic process of dysentery]

The use of complex typing of Sh. sonnei by the colicinogenic and enzymatic properties in epidemiological analysis of dysentery caused by Sh. sonnei, apart from establishment of epidemiological connections in the foci, offered a possibility of introducing significant corrections in the determination of the sizes and duration of existence of the epidemic foci, as well as in detection of the sources and factors of transmission of the infection established in epidemiological examination. Typing of Sh. sonnei also aided in ascertaining that, apart from general regularities in the individual territories, the epidemic process in individual groups of the population and in different seasons of the year could also course autonomously.     

Characteristics and trends in the development of an epidemic process of Sonne and Flexner dysentery among preschool children

The results of studies indicate that the morbidity rates of dysentery among children attending preschool institutions and children brought up at home converged in recent years. This phenomenon was most pronounced among children of the kindergarten age group. At the same time dysentery caused by Sh. sonnei and Sh. flexnery produced a higher morbidity rate among children attending nursery in comparison with that among children of the same age group brought up at home. Group infections in preschool institutions were caused by Sh. sonnei in 89.1% of cases and by Sh. flexneri in 10.9% of cases. Outbreaks due to the transfer of infection through everyday contacts were observed only in dysentery caused by Sh. sonnei, constituting 71.4% of the total number of dysentery outbreaks.     

Production of auxotrophic mutants of Shigella sonnei]

Use of selection method with R. Ffm phage offered a possibility of obtaining R-forms of Sh. sonnei from the population of bacteria of phase II with a low frequency of natural dissociation. Mono- and polyauxotrophic mutant of I, II and R-phases by hir, ilv, pro, and mtl markers were obtained by treatment of Sh. sonnei strains with nitrosoguanidine and ethyl-methanesulfonate. The frequency of mutation in two Sh. sonnei strains studied in this work (UBC and No. 941) by the same genetic regions proved to differ. The change of Sh. sonnei phase I into phase II was observed only in selection by proline marker which could be connected with the existence in this region of a gene controlling the dissociation process.     

Manifestations of the cyclic nature of the epidemic process in dysentery

Different forms of dysentery, especially those caused by Sh. sonnei and Sh. flexneri, have been found to differ considerably in their cyclic recurrence. The development cycles of the epidemic processes of dysentery have an objective character, occur in the presence of any tendencies in the morbidity rate, and depend on the natural factors. Thus, the cycles of increase and decrease in morbidity are 3, 6, 9, 12 years for dysentery caused by Sh. sonnei and 6, 7, 8 years for dysentery caused by Sh. flexneri.     

枯草芽孢杆菌活菌体外拮抗6种肠道致病菌的研究

对枯草芽孢杆菌BS 3株在体外对 6种常见肠道致病菌 (肠产毒性大肠杆菌、肠侵袭性大肠杆菌、肠致病性大肠杆菌、鼠伤寒沙门菌、福氏志贺菌和宋内志贺菌 )的拮抗作用进行了研究。结果表明 ,枯草芽孢杆菌BS 3株对宋内志贺菌、肠致病性大肠杆菌及肠产毒性大肠杆菌拮抗作用较为明显。     

Determination of the O antigen of Shigella sonnei by a competitive immunoenzyme method

A technique for immunoenzymatic diagnosis of dysentery by Shigella sonnei O-antigen was developed. For induction of antibodies to O-antigen rabbits were immunized by intravenous administration of a commercial antidysentery vaccine. Specific antibodies to O-antigen belonging to class G immunoglobulins and not binding to O-antigens of Sh. flexneri and Salmonella typhimurium were obtained. beta-Lactamase of Bacillus licheniformis 749/c was used as a marker enzyme in the immunoenzymatic assay. To increase the sensitivity, beta-lactamase molecules were preliminarily linked with glutaric aldehyde into oligomers. Conjugates of Sh. sonnei O-antigen with the oligomers of B. licheniformis 749/c beta-lactamase were prepared with the periodate method by oxidizing O-antigen. The conjugate was used in competing solid phase immunoenzymatic assay for determination of Sh. sonnei O-antigen in blood serum of patients with dysentery. The sensitivity of the assay is 0.5-1 ng per 1 ml of O-antigen.     

Inhibition of Shigella sonnei by Lactobacillus casei and Lact. acidophilus.

The protective effect of feeding milk fermented with a mixture of Lactobacillus casei and Lact. acidophilus against Shigella sonnei was studied. There was a 100% survival rate in mice fed for 8 d with fermented milk and then dosed orally with Sh. sonnei. The survival rate in control mice was approximately 60% after 21 d. Colonization of the liver and spleen with Sh. sonnei was markedly inhibited by pretreatment with fermented milk. Differences in cell counts of 2-3 log units between treated and control mice were always obtained, shigellas were not detected in these organs by the 10th day in treated mice, while high levels were maintained in the controls. Higher levels of anti-shigella antibodies were found both in sera and in small intestinal fluid of mice treated with fermented milk, suggesting that the protective immunity could be mediated by the mucosal tissue. These results suggest that milk fermented with Lact. casei and Lact. acidophilus could be used as a prophylactic against gastrointestinal infections by shigellas.     

Inhibition of Shigella sonnei by Lactobacillus casei and Lact. acidophilus

The protective effect of feeding milk fermented with a mixture of Lactobacillus casei and Lact. acidophilus against Shigella sonnei was studied. There was a 100% survival rate in mice fed for 8 d with fermented milk and then dosed orally with Sh. sonnei. The survival rate in control mice was approximately 60% after 21 d. Colonization of the liver and spleen with Sh. sonnei was markedly inhibited by pretreatment with fermented milk. Differences in cell counts of 2–3 log units between treated and control mice were always obtained, shigellas were not detected in these organs by the 10th day in treated mice, while high levels were maintained in the controls. Higher levels of anti-shigella antibodies were found both in sera and in small intestinal fluid of mice treated with fermented milk, suggesting that the protective immunity could be mediated by the mucosal tissue. These results suggest that milk fermented with Lact. casei and Lact. acidophilus could be used as a prophylactic against gastrointestinal infections by shigellas.     

痢疾杆菌不同群、型间交叉保护性试验研究

本文对痢疾杆菌不同群、型间的交叉保护作用进行了观察。试验模型为恒河猴,将其分为４组,第一、三组分别为感染过福氏１ａ和宋内菌并已康复的猴;第四组为用双价菌苗株ＦＳ（福氏２ａ和宋内）免疫的猴体,剂量依次为４×１０１０、６．５×１０１０、６×１０１０,共１６．５×１０１０活菌,第二组为空白对照。所有４组皆用福氏２ａ２５８００×１０８活菌攻击。从发病率来看,不同菌群与菌型间没有明显的交叉保护作用;从发病程度看则一组显著低于对照组,三组与对照组无显著差异,此结果表明痢疾杆菌Ｂ群内存在交叉保护作用,但较同型保护作用弱。     

1株枯草芽胞杆菌体外拮抗6种肠道致病菌的研究

目的研究枯草杆菌BS-3株对大肠埃希菌等6种肠道致病菌的拮抗作用。方法通过在体外BS-3菌株分别与大肠埃希菌等6种致病菌混合培养后,观察不同时间内各菌的菌量变化。结果BS-3菌株与6种肠道致病菌混合培养24、48、72和96h,其菌量逐渐增加;6种致病菌的菌量随着培养时间延续逐渐减少,其中产毒性大肠埃希菌、致病性大肠埃希菌和宋内志贺菌与对照组比较差异更明显。结论BS3菌株在培养生长过程中,可抑制大肠埃希菌等6种肠道致病菌的生长。     

Assessment of the diagnostic effectiveness of antigenic preparations from Sonne shigellae]

The authors studied the diagnostic possibilities of 4 diagnistic agents from Sh. sonnei. A total of 1500 from 1122 persons were investigated. Specificity and sensitivity of the diagnostic agents from Sh. sonnei were determined. Methodical priciples of the objective assessment of the diagnostic efficacy of the antigenic preparations in the controlled epidemiological trial were elaborated. A possibility of establishment of the etiological diagnosis of Sonne dysentery in the passive hemagglutination or blast agglutination tests by the results of testing with the diagnostic agents of the serum obtained from the patient once or by determining the dynamics of the antibody titre rise in coupled serum portions was not great.     

Immunoelectrophoretic analysis of the antigenic structure of Sh. sonnei]

The authors studied the antigenic composition of 105 Sh. sonnei strains freshly isolated from patients suffering from acute dysentery and carriers. Immunophoregrams of pure S-and R-forms species were obtained. Up to 13 antigens differing by electrophoretic and diffusion mobility and immunological specificity were revealed among soluble Sh. sonnei antigens The position of common and specific antigens was determined on the immunophoregram. Along with the thermostable somatic O-antigen detected at the I phase of the S-forms, and two thermolabile O-antigen components at the II phase, and the R-forms, there was revealed a surface, relatively thermolabile, K-antigen of A-type capable of agglutinating live bacteria in the O-antiserum; position of the latter on the immunophoregram was also determined.     

Citrate method of extracting antigens from Shigella sonnei. I. Comparison with other methods

The comparative characteristic of extracts obtained from Sh. sonnei by the method of Raynaud and Digeon and neurotoxin obtained by sedimentation with trichloroacetic acid from chloroform autolysates by the method of Mesrobeanu et al. is presented. Both preparations were shown to be similar in their antigenic structure and immunogenicity for mice and guinea-pigs. Nevertheless the extracts obtained by the citrate method contained considerably less protein and endotoxin and had no enterotoxic activity. This allows to recommend the citrate method for extracting protective antigens from Sh. sonnei.     

Modern methods of intraspecies typing of Sonne shigellae. II. Spread of Sonne shigellae of different biochemical types]

The paper presents the results of studying peculiarities of the Sh. sonnei of different biochemical types spread established by their typing scheme suggested by the authors earlier according to rhamnose, xylose and maltose. The epidemic process in dysentery both during the years of the rise and of the decline of its incidence at various territories of the countries proved to be maintained on account of circulation of Sh. sonnei of various biochemical types. The results of studying their dissociative and virulent properties confirmed the biological separation of individual biochemical types. An interrelationship between the character of the biochemical pattern of Shigellae sonnei at the individual territories and the persisting activity of different ways of dysentery transmission was determined. The results of studying the biochemical pattern could be used as an indicator of the degree of activity of individual ways of dysentery spread at various territories.     

Acid tolerance of Shigella sonnei and Shigella flexneri

AIMS: Determination of the behaviour of Shigella sonnei and Sh. flexneri under acid conditions. METHODS AND RESULTS: The growth and survival of Shigella spp. (9 isolates) in acidified Brain Heart Infusion (BHI) (pH 5.0-3.25 with pH intervals of 0.25) was determined after 6, 24 and 30 h incubation at 37 degrees C. Subsequently, survival of shigellae was studied in apple juice and tomato juice stored at 7 degrees C and 22 degrees C for up to 14 days and in strawberries and a fresh fruit salad, kept at 4 degrees C for 4 and 48 h. CONCLUSIONS: The minimum pH for growth in acidified BHI for Sh. flexneri and Sh. sonnei was, respectively, pH 4.75 and pH 4.50. Survival in fruit juices and fresh fruits depended upon their pH, the type of strain and the incubation temperature. Shigella spp. Survived for up to 14 days in tomato juice and apple juice stored at 7 degrees C. The shortest survival time (2-8 d) was observed in apple juice at 22 degrees C. Sh. sonnei but not Sh. flexneri was recovered after 48 h from strawberries and fruit salad kept at 4 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: Acid foods, especially if kept at refrigeration temperatures, support survival of Shigella spp. and may cause Shigella food poisoning.