The interrelations of the causative agents of transmissible diseases in ixodid ticks (Ixodidae) with a mixed infection

The data on interactions between pathogens of human diseases with natural focality in ixodid ticks (Ixodidae) with mixed infection are reviewed. Different variants of mixed infection revealed in nature and accompanied by predominantly extracellular, or both extra- and intracellular location of the agents in tick organism are considered. Natural mixed infection of ticks by different pathogens is a normal and commonly occurring phenomenon; moreover, there is no experimental evidence for the existence of any antagonistic relationships between spirochetes, rickettsiae, and piroplasms in such ticks. The absence of antagonism between different agents in vectors largely provides a relative autonomy of corresponding parasitic systems and creates conditions for coexistence of different parasitic systems in mixed natural foci.     

Conjugative R-plasmid resistance of the causative agents of Yersinia infection

Nature, structure, occurrence and drug resistance of 160 strains of Y. pseudotuberculosis and 60 strains of Y. enterocolitica isolated from various sources within 1986-1988 were studied. In the strains of Y. pseudotuberculosis, the cell composition with respect to the requirements in calcium ions as well as the plasmid profiles with determination of the molecular weights of the plasmids in the antibiotic sensitive and resistant pathogens and R(+)-transconjugants were investigated. Some molecular genetic properties of the Yersinia R plasmids were also investigated. Antibiotic polyresistant strains of Y. enterocolitica were the most frequent donors of the R plasmids while the strains of Y. pseudotuberculosis were less frequently the donors, in the resistance pattern of which there were more frequent streptomycin and tetracycline resistance determinants. The conjugative R plasmids of Y. pseudotuberculosis were characterized by strict control of replication, repressed frequency of transfers, and a molecular weight of about 47 MD. Their replicones as a rule contained streptomycin and tetracycline markers determining resistance to streptomycin and tetracycline at the levels of 1250 and 156 micrograms/ml, respectively.     

Sources of intrapopulation variability in causative agents of nosocomial infection

The mechanisms of heterogeneity of S. aureus and P. aeruginosa populations of pathological foci in patients with wound, traumatic, and burns infections were studied. It has been established that populations of the mentioned species in the sources of infection (patients and carriers) are pronouncedly heterogeneous and objects in the external environment serving as factors of transmission are contaminated with a whole complex of diverse variants. The conclusion can therefore be drawn that the first source of intrapopulation variability of wound populations of microbes is the presence of varying strains and variants in the infecting dose of the causative agent. The second source consists in repeated superinfection (immigration) of pathological processes by new, usually nosocomial, strains and variants of the same species with their subsequent selection during the patients' stay in the health-service establishment. Other sources of population variability, such as mutation and recombination, are of minor importance. With respect to the obtained results it is necessary to increase the volume of the representative sample of cultures in bacteriological diagnosis of open processes, to protect them reliably from superinfection, to follow up dynamically changes in the composition of causative agents and to provide for suitable correction of chemotherapy.     

Prolongation of the effect of immunostimulators as means of increasing resistance to causative agents of infection

Possible prolongation of the biological effect of some available immunostimulators such as prodigiozan, salmozan, polyribonate and thymalin by their sorption on aluminium hydrate was studied. It was shown that in comparison to the native immunostimulators the sorbed ones had a more pronounced biological action and provided a more prolonged increase in the host resistance to the causative agents of gas gangrene and typhoid fever. Using prodigiozan as an example it was demonstrated that the observed increase in the anti-infective activity of the sorbed drugs was associated with more intensive stimulation of some immunological factors involved in regulation of host nonspecific resistance. The results of the study are likely to indicate that it was experiment to further investigate the drugs to reveal their efficacy in other infection models and to optimize the schemes of their use.     

Microbiological characterization of the causative agents of hospital infection in urological patients

The analysis of the etiological structure of hospital infection in 52 urological patients has been carried out. The sensitivity of the causative agents of this infection to different antibiotics has been studied and recommendations on rational antibacterial therapy are given.     

Antibiotic sensitivity of the causative agents of suppurative surgical infection]

Sensitivity of 1492 strains of the causative agents of the surgical purulent infections, i. e. pathogenic Staphylococcus, Proteus, Ps. aeruginosa and E. coli to benzylpenicillin, streptomycin, levomycetin, tetracycline, erythromycin, oleandomycin, monomycin, kanamycin, novobiocin, ampicillin, oxacillin, ceporin, gentamicin and rifampicin was studied. Gentamicin was most active against all the bacterial species tested. The staphylococci were in addition sensitive in a high percentage of the cases to rifampicin, novobiocin, ceporin, monomycin and kanamycin. The isolates of E. coli were in addition sensitive to ceporin, monomycin and kanamycin. Sensitivity of the strains of Ps. aeruginosa and Proteus was low to all of the antibiotics except gentamycin. Most of the strains of the causative agents of the surgical purulent infections were multiresistant to 4 antibiotics. The number of the staphylococcal strains sensitive to benzylpenicillin, streptomycin and levomycetin increased in 1976 as compared to 1975 on the background of a limited use of these antibiotics in clinics.     

Adhesiveness and antibiotic resistance of the causative agents of salmonella infection in Gomel' region

The adhesive capacity, resistance to antibiotics and biological properties of Salmonella strains of different serogroups, circulating in the Gomel region, were under study. Resistance to antibiotics and changes in biological properties were accompanied by an increased adhesiveness of these strains. A high degree of adhesiveness was noted in S. hadar, a new for Belarus strains.     

The genomic fingerprinting of the causative agents of sapronoses

The genome polymorphism of the causative agents of sapronoses (Vibrio cholerae, Legionella and Leptospira) has been studied. The use of the method of genome fingerprinting [correction of dactyloscopy] has been shown to permit the differentiation of closely related strains of such causative agents. The epidemically significant strains of the causative agents of sapronoses, isolated in different geographical regions, have been found to be genotypically related, i.e., they are probably of clonal origin. Avirulent and nontoxigenic strains are genotypically heterogeneous and differ both from one another and from epidemically significant strains. Using V. cholerae as an example, the hypothesis of the appearance of potentially dangerous variants at the epidemic period in the absence of their release at the period between epidemics is considered.     

The virulence of Streptococcus pneumoniae strains--the causative agents of pneumococcal infection at different sites]

A total of 256 S. pneumoniae strains, the causative agents of infectious processes with different localization, were studied for their virulence (in experiments on mice), neuraminidase and aldolase-protease activity (APA). In pneumococcal strains isolated 18-20 hours after intraperitoneal infection their virulence for mice increased, on the average, 1,000-fold and the average level of extracellular and cellular neuraminidase and APA increased 2- to 5-fold in comparison with the initial values. Pneumococcal strains causing acute pneumococcal infections with different localization, or the aggravation of such infections, exhibited higher virulence for mice and higher levels of neuraminidase and APA, while the inflammatory process at the period of clinical remissions was mainly maintained by S. pneumoniae cultures with low virulence.     

A method for determining the sensitivity of the causative agents of suppurative infection to iodopiron

Bacterial suspensions of cultures (10(7) PFU) of pathogenic Staphylococcus, vulgar Proteus and pyocyanic bacterium are resistant to 2.9-46.87 mg per disc of iodopyron in 100% of cases. Sensitivity of 32 and 100% of cultures of pyocyanic bacteria (of 25 under study) being in the suspension (10(5) PFU) to 11.71 and 23.43-9.375 mg of idopyron, respectively, in a hole has been established. To determine sensitivity of pyocyanic bacteria to iodopyron it is suggested to use the procedure of adding of 11.71 mg of the preparation (water solution) to the holes in MPA.     

Modifying action of oxytocin on the biological properties of the causative agents of anaerobic non-clostridial infection

In a number of in vitro experiments the effect of oxytocin on the antilysozyme and anticomplemental activity of Propiobacterium propionicum, Bacteroides fragilis, Prevotella melaninogenica and Peptostreprtococcus anaerobius, isolated from patients with acute pyoinflammatory pleuropulmonary diseases, was studied. Antibiotic resistance dynamics of the infective agents under study to lincomycin, clindamycin, thienam, vancomycin was also detected. The inhibiting activity of oxytocin on the persistence properties of B. fragilis, P. melanogenica and P. anaerobius was noted. Under the influence of the preparations used changes in the sensitivity of the strains to a number of antibiotics of the lincosamide, carbapenem and glycopeptide groups were found to occur. The data thus obtained were indicative of the possible mechanisms of action of oxytocin in the treatment of acute pyoinflammatory pleuropulmonary diseases of anaerobic nonclostridial etiology.     

Etiological structure and resistance to antibacterial drugs of causative agents of cross infection in Donetsk

Tests for hemocultures were performed in 51 patients with clinical diagnoses of sepsis treated in a reanimation unit. Microbial cultures were isolated from 30 patients (58.9 per cent). Staphylococci in pure cultures and associations were the causative agents of sepsis in 26 patients (86.4 per cent). The cultures of E. coli, Y. enterocolitica and Streptococcus faecalis were isolated from 2, 1 and 1 patients, respectively. Pus specimens from 111 patients with postinjection suppuration were tested and staphylococci in pure cultures and associations were detected in 90 patients (81.8 per cent). The cultures of P. vulgaris, Streptococcus pyogenes, E. coli, Str. faecalis, Enterobacter spp. and Pseudomonas aeruginosa were isolated from 10, 5, 3, 1, 1 and 1 patients, respectively. The results showed that Staphylococci played the leading role in development of the hospital infections. Treatment of such patients should be performed with an account of antibioticograms since many strains are resistant to various antibiotics.     

Comparative sensitivity of the main causative agents of suppurative infection to antibacterial preparations and their combinations

Sensitivity of 492 microbial strains to 9 antibacterial drugs and their double combinations was studied. The MTC was determined with the method of serial dilutions in an apparatus MIC-2000 (Austria). The apparatus provides determination of the MTC simultaneously to 12 antibiotics in 8 dilutions or to 8 antibiotics in 12 dilutions.     

Changes in the composition of the causative agents of wound infection in emergency surgery in the period from 1967 through 1987

The composition of the causative agents of suppurations, isolated from suppurating wounds of patients hospitalized at different departments of the Sklifosovski? Emergency Aid Institute was studied. The proportion of representatives of different microbial families among more than 18,000 strains of the causative agents of wound infection was estimated. Fluctuations in the amount and structure of the agents were analyzed in different clinics over the period of 1967-1987. Under the conditions of emergency aid hospital Staphylococcus aureus proved to be the most frequent causative agent of suppurative inflammatory processes at different departments. At the same time no tendency towards an increase of the etiological role of any microbial family in the development of wound infections was noted. The incidence of different causative agents of suppurations was found to vary at different departments, depending on their specialization and season. The results of observations on the composition of the causative agents of wound infection may be used for the planning and evaluation of antiepidemic measures.