Inhibitory effect of streptococci on the growth of M. catarrhalis strains and the diversity of putative bacteriocin-like gene loci in the genomes of S. pneumoniae and its relatives.

S. pneumoniae is a facultative human pathogen causing a wide range of infections including the life-threatening pneumoniae or meningitis. It colonizes nasopharynx as well as its closest phylogenetic relatives S. pseudopneumoniae and S. mitis. Both the latter, despite the considerable morphological and phenotypic similarity with the pneumococcus, are considerably less pathogenic for humans and cause infections mainly in the immunocompromized hosts. In this work, we compared the inhibitory effect of S. pneumoniae and its relatives on the growth of Moraxella catarrhalis strains using the culture-based antagonistic test. We observed that the inhibitory effect of S. mitis strains is kept when a hydrogen peroxide produced by cells is inactivated by catalase, and even when the live cells are killed in chloroform vapors, in contrast to the pneumococcus whose inhibiting ability disappeared when the cells die. It was suggested that this effect may be due to the production of bacterial antimicrobial peptides by S. mitis, so we examined the genomes of our strains for the presence of bacteriocin-like peptides encoding genes. We observed that a set of bacteriocin-like genes in the genome of S. mitis is greatly poorer in comparison with S. pneumoniae one; moreover, in one S. mitis strain we found no bacteriocin-like genes. It could mean that there are probably some additional opportunities of S. mitis to inhibit the growth of competing neighbors which are still have to be discovered.

[Discovery of Genetic Markers of Resistance to ß-Lactams in Gramnegative Microorganisms by PCR Diagnosis].

Fifteen specimens of the hemoculture and 89 specimens of the broncho-alveolar lavage were used in the study. Monocultures of gramnegative bacteria resistant to cefotaxime, cefepime, imipenem and meropenem were isolated from the specimens. The PCR method with detection of the results in the real time regimen (PCR test-system Litekh) provided detection of the beta-lactamase genes: bla(CTX-M-like) (72/104, 69.2%), bla(NDM) (6/104, 5.8%), bla(VIM) (49/104, 47.1%) and bla(OXA48-like) (59/104, 56.7%). There was identified correlation between the phenotype of resistance of Acinetobacter spp., Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli to cefotaxime and carbopenems and detection of the bla(CTX-M-like) and bla(NDM) genes. At the same time, up to 70% of the K. pneumoniae isolates from the biological specimes positive with respect to the presence of the carbapenase bla(VIM) and bla(OXA48-like) genes demonstrated their phenotypic susceptibility to carbopenems. The results of the study confirmed the prognostic value of the genetic diagnosis for improvement of the routine bacteriological investigations.

[Genetic determinants of antibiotic resistance in oropharyngeal streptococci in patients with chronic obstructive pulmonary disease and in those with asthma]. / Geneticheskie determinanty ustoichivosti orofaringeal'nykh streptokokkov k antibakterial'nym sredstvam u patsientov s khronicheskoi obstruktivnoi bolezn'yu legkikh i bol'nykh bronkhial'noi astmoi.

AIM: To identify oropharyngeal Streptococcus species and to analyze the genetic determinants of antibiotic resistance in patients with asthma and in those with chronic obstructive pulmonary disease (COPD). MATERIAL AND METHODS: An experimental diagnostic Streptopol+ (Lytech Co. LTD) panel based on a multiplex real-time PCR was applied to investigate the representation of antimicrobial resistance genes (mef and ermB) and the species composition of streptococci isolated from oropharyngeal swab samples from 89 patients with stable COPD and from 51 patients with asthma. RESULTS: In the stable disease period, the oropharyngeal swabs were found to contain Streptococcus pneumoniae in 7.8% of the patients with asthma and in 6.74% of those with COPD; the common feature of these groups was a tendency towards a severe disease course and recurrent exacerbations requiring antibiotics. S. pyogenus was detected in 42.9% of the oropharyngeal swabs from COPD and asthma patients without exacerbations. The oropharyngeal swabs showed the mef gene in 100% of the patients with asthma and in 100% of those with COPD; the ermB gene was encountered in 91% of the patients with COPD and in 82.4% of those with asthma. The COPD patients displayed a direct correlation between the representation of the ermB gene and sputum production and smoking index. The mef and ermB genes were directly correlated with the frequency of exacerbations in patients with COPD. CONCLUSION: The identified streptococci are a reservoir of antimicrobial resistance genetic determinants - the mef and ermB genes encoding the mechanisms of streptococcal macrolide resistance. The representation of the above genes directly correlates with the frequency of exacerbations and the number of antimicrobial drug uses.

[Susceptibility of gramnegative carbapenemase-producing bacteria to various group antibiotics].

The study involved 25 isolates of gramnegative carbapenemase-producing bacteria. 17 isolates of Klebsiella pneumonia produced carbapenemase NDM-1 and were highly resistant to cephalosporins (MIC>128 mcg/ml), carbapenems (MIC>16 mcg/ml), aminoglycosides and fluoroquinoiones, while among them 4 isolates preserved susceptibility to azthreonam and all of them were susceptible to tigecycline and polymyxin. 2 isolates of Acinetobacter genomospecies 13 produced NDM-1 and were resistant to all the beta-lactams and amikacin, while preserved susceptibility to gentamicin, co-trimoxazole, tigecycline and polymyxin, the susceptibility to ciprofloxacin being lowered. Carbapenemase VIM-4 was produced by 2 isolates of Enterobacter cloacae, which were highly resistant to cephalosporins and azthreonam, significant synergism being observed between cefepim and clavulanate. The resistance of the isolates to carbapenems was low (MIC 0.5-4.0 mcg/ml), they also being resistant to aminoglycosides and ciprofioxacin and susceptible to tigecycline and polymyxin. Carbapenemases KPC-2 were detected in 2 isolates of K.pneumoniae and in 1 isolate of E.cloacae. The above isolates were resistant to all the beta-lactams, ciprofloxacin, aminoglycosides and co-trimoxazole. I isolate of E.cloacae showed resistance to tigecychine and I isolate of K.pneumoniae was resistant to polymyxin. Carbapenemase OXA-48 was detected in 1 isolate of K.pneumoniae. It was resistant to all the beta-lactams, ciprofloxacin and co-trimoxazole and susceptible to aminoglycosides, tigecycline and polymyxin.

[Characteristics of complex formation between monomeric and dimeric bisbenzimidazoles and AT-containing polynucleotide].

Double-stranded DNA is a one of the most important intracellular anticancer agent targets. Disturbance of DNA functions as well as DNA structure lead to disorder of such processes as transcription and/or translation thus inducing tumor cells death. Complex formation between novel dimeric bisbenzimidazole DB(7) and poly(dA-dT) duplex in comparison with known monomeric bisbenzimidazole MB(Ac) was investigated in this study. DB(7)-poly(dA-dT) binding constant was determined by fluorescence spectroscopy using Scatchard plot and it values 1.18 x 10(8) M(-1) that is two orders of magnitude larger than MB(Ac) one (2.06 x 10(6) M(-1)). Thus, from findings mentioned above it could be concluded that the presence of two bisbenzimidazole moieties in the ligand structure significantly increases its affinity to the polynucleotide which motivates the synthesis of new potential anticancer drugs based on dimeric bisbenzimidazoles.