Microbiological monitoring of causative agents of sapronoses in the water of the Bogatinskoe water reservoir

The results of the microbiological monitoring of potential causative agents of sapronoses in the water of the Bogatinskoye reservoir revealed that in the summer period of 1998 the mass accumulation of virulent Aeromonas sobria (up to 25% of the total number of heterotrophic bacteria) took place. The autumn period was characterized by a decrease in the number of A. sobria and the detection of bacteria of the genus Vibrio (up to 22%) with V. mimicus and V. metschnikovii identified among them in the water ecosystems of the southern regions of the Maritime Territory.     

Microbiological control of drug resistance of causative agents in suppurative-septic infections in newborn infants

Resistance of the main causative agents of purulent septic infections such as pneumonia, meningitis, sepsis, etc. to 11 chemotherapeutic drugs was studied. The pathogens were isolated from autopsies of 203 newborns who died within 1981 to 1987. Among 2978 isolates belonging to Enterobacteriaceae (2466 strains) and Pseudomonadaceae (512 strains) which constituted 88% of all the isolates, strains with multiple resistance predominated: 90% of the strains resistant to 4 or more antibiotics, 77% of the strains resistant to 6 or more antibiotics and 48% of the strains resistant to 8 or more antibiotics. The highest number of the isolates were resistant to 8 and 9 chemotherapeutics (19 and 20%, respectively). 84% of all the isolates belonged to 4 genera: Klebsiella (34%), Escherichia (21%), Serratia (14%) and Pseudomonas (15%). They were characterized by the highest resistance spectra. In all the cases massive colonization of the intestine by the strains with multiple resistance which caused purulent septic infections was observed. The most frequent variants of the drug resistance combination were determined. In the total frequency of the isolate with multiple resistance no significant differences were detected in 1981 and thereafter. In 1986-1987 the frequency of S. marcescens strains increased 3-5 times with simultaneous broadening of their drug resistance spectra. Strains of S. marcescens and K. pneumoniae with multiple drug resistance endemic for definite hospitals were detected.     

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.     

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.     

The reciprocal effect of the causative agents in a mixed infection in burn injury

In vitro experiments on the joint cultivation of Pseudomonas aeruginosa, Escherichia coli, staphylococci and in vivo experiments carried out on mice with the experimental mixed infection of a burn injury revealed the pronounced antagonistic action of P. aeruginosa with respect to staphylococci and E. coli. Under the same conditions, in the joint cultivation of P. aeruginosa and fungi of the genus Candida and in the mixed infection of a burn wound caused by the same microorganisms the mutual stimulation of multiplication and a considerable aggravation of the clinical course of a burn wound were observed. The mutual influence of associates in the mixed infection of a burn injury is manifested by an increase in the number of an antibiotic-resistance microorganisms in their populations and, so far as the macroorganism is concerned, in the aggravation of the course of the infectious process and the formation of the pronounced state of immunodeficiency.     

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.     

Microbiological monitoring for the causative agents of nosocomial infections (exemplified by resuscitation and intensive therapy units)]

More than 900 isolates from at least 1500 patients were tested within 1996-1998. Gram-negative organisms were the main pathogens isolated from patients with different forms of nosocomial complications such as late pneumonia, associated with artificial ventilation of the lungs, and various secondary wound or urinary tract infections. The prevalence of Pseudomonas aeruginosa was stated. Antibioticograms showed that the most active drugs were imipenem (more than 90 per cent of the susceptible isolates) and ticarcillin/clavulanate (48-58 per cent of the susceptible isolates). The activity of ticarcillin/clavulanate (Timentin) was practically the same as that of imipenem against 21 strains of P.aeruginosa isolated from the blood and cerebrospinal fluid of 21 patients with sepsis and 3 patients with secondary purulent meningitis.     

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.     

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.     

Analysis of the etiological structure and dynamics of antibiotic resistance in the causative agents of suppurative inflammatory diseases in the patients at a large general hospital

The structure of the causative agents isolated from patients with pyoinflammatory infections in 1980-1983 was analysed. It was shown that the surgical and urological infections were mainly caused by gram-negative bacteria. The other pyoinflammatory infections were mainly due to gram-positive cocci. A relatively high frequency of the strains of gram-negative bacteria, especially among Pseudomonas spp. and Enterobacter spp., resistant to aminoglycoside antibiotics, such as gentamicin, sisomycin and tobramycin with preserved sensitivity to amikacin and netilmicin in the majority of the strains was shown. Among the beta-lactam antibiotics cephotaxim and cephalotin were most active against gram-negative bacteria and staphylococci, respectively. The majority of the antibiotic resistant strains of gram-negative bacteria had analogous structures and levels of resistance to 7-12 antibiotics which might indicate the occurrence of 1-2 resistance plasmids among the clinical strains.     

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.     

Pathology of camel tuberculosis and molecular characterization of its causative agents in pastoral regions of Ethiopia

A cross sectional study was conducted on 906 apparently healthy camels slaughtered at Akaki and Metehara abattoirs to investigate the pathology of camel tuberculosis (TB) and characterize its causative agents using postmortem examination, mycobacteriological culturing, and multiplex polymerase chain reaction (PCR), region of difference-4 (RD4)-based PCR and spoligotyping. The prevalence of camel TB was 10.04% (91/906) on the basis of pathology and it was significantly higher in females (χ² = 4.789; P = 0.029). The tropism of TB lesions was significantly different among the lymph nodes (χ² = 22.697; P = 0.002) and lung lobes (χ² = 17.901; P = 0.006). Mycobacterial growth was observed in 34% (31/91) of camels with grossly suspicious TB lesions. Upon further molecular characterization using multiplex PCR, 68% (21/31) of the colonies showed a positive signal for the genus Mycobacterium, of which two were confirmed Mycobacterium bovis (M. bovis) by RD4 deletion typing. Further characterization of the two M. bovis at strains level revealed that one of the strains was SB0133 while the other strain was new and had not been reported to the M. bovis database prior to this study. Hence, it has now been reported to the database, and designated as SB1953. In conclusion, the results of the present study have shown that the majority of camel TB lesions are caused by mycobacteria other than Mycobacterium tuberculosis complex. And hence further identification and characterization of these species would be useful towards the efforts made to control TB in camels.     

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.