Lietuvoje išskirtų Escherichia coli ir Salmonella enterica padermių atsparumas chinolonams

Lithuanian isolates of Escherichia coli and Salmonella enterica from animals and humans were examined for resistance to quinolones, fluoroquinolones and for resistance-associated mutations. 9% of S. enterica from animals and 4% of isolates from clinical samples of humans were resistant to nalidixic acid and susceptible to fluoroquinolones. DNA analysis of nalidixic acid-resistant S. enterica strains from animals revealed a single mutation at codon 83 (Ser→Phe) in gyrA gene, whereas resistant clinical strains contained a single gyrA mutation at codon 87 (Asp→Tyr). 10% of human isolates of E. coli were resistant to nalidixic acid and ciprofloxacin. 22% of E. coli isolates from calves were resistant to nalidixic acid. 40% and 20% of E. coli isolates from pigs were resistant to nalidixic acid and to fluoroquinolones, respectively. E. coli isolates of animal and human origin analyzed for nalidixic acid resistance-associated mutations carried single mutations at codon 83 (Ser→Leu) or at codon 87 (Asp→Tyr) in gyrA gene. Fluoroquinolone-resistant E. coli isolates from calves and humans carried multiple mutations within gyrA (83Ser→Leu, 87Asp→Gly or Asn) and parC (80Ser→Ile or Arg, 84Glu→Val or Lys) genes

Tigecycline – how powerful is it in the fight against antibiotic-resistant bacteria?

Tigecycline is a semisynthetic analogue of earlier tetracyclines and represents the first member of a novel class of antimicrobials – glycylcyclines – recently approved for clinical use. It is active against a broad range of gram-negative and gram-positive bacterial species including clinically important multidrug-resistant nosocomial and community-acquired bacterial pathogens. The exact molecular basis of tigecycline action is not clear at present, although similarly to the tetracyclines, it has been shown to inhibit the translation elongation step by binding to the ribosome 30S subunit and preventing aminoacylated tRNAs to accommodate in the ribosomal A site. Importantly, tigecycline overcomes the action of ribosomal protection proteins and is not a substrate for tetracycline efflux pumps of most bacteria – well-known and prevalent cellular mechanisms of microbial tetracycline resistance. The present review summarizes current knowledge on the molecular mechanism of the tigecycline action, antibacterial activity against various bacteria, clinical application, development of resistance to glycylcyclines

Tigeciklinas. Kokio veiksmingumo ginklas kovoje su antibiotikams atspariomis bakterijomis?

Tigecycline is a semisynthetic analogue of earlier tetracyclines and represents the first member of a novel class of antimicrobials – glycylcyclines – recently approved for clinical use. It is active against a broad range of gram-negative and gram-positive bacterial species including clinically important multidrug-resistant nosocomial and community-acquired bacterial pathogens. The exact molecular basis of tigecycline action is not clear at present, although similarly to the tetracyclines, it has been shown to inhibit the translation elongation step by binding to the ribosome 30S subunit and preventing aminoacylated tRNAs to accommodate in the ribosomal A site. Importantly, tigecycline overcomes the action of ribosomal protection proteins and is not a substrate for tetracycline efflux pumps of most bacteria – well-known and prevalent cellular mechanisms of microbial tetracycline resistance. The present review summarizes current knowledge on the molecular mechanism of the tigecycline action, antibacterial activity against various bacteria, clinical application, development of resistance to glycylcyclines

Molecular Characterization of the Acid-Inducible asr Gene of Escherichia coli and Its Role in Acid Stress Response

Enterobacteria have developed numerous constitutive and inducible strategies to sense and adapt to an external acidity. These molecular responses require dozens of specific acid shock proteins (ASPs), as shown by genomic and proteomic analysis. Most of the ASPs remain poorly characterized, and their role in the acid response and survival is unknown. We recently identified an Escherichia coli gene, asr (acid shock RNA), encoding a protein of unknown function, which is strongly induced by high environmental acidity (pH < 5.0). We show here that Asr is required for growth at moderate acidity (pH 4.5) as well as for the induction of acid tolerance at moderate acidity, as shown by its ability to survive subsequent transfer to extreme acidity (pH 2.0). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western analysis of acid-shocked E. coli cells harboring a plasmid-borne asr gene demonstrated that the Asr protein is synthesized as a precursor with an apparent molecular mass of 18 kDa. Mutational studies of the asr gene also demonstrated the Asr preprotein contains 102 amino acids. This protein is subjected to an N-terminal cleavage of the signal peptide and a second processing event, yielding 15- and 8-kDa products, respectively. Only the 8-kDa polypeptide was detected in acid-shocked cells containing only the chromosomal copy of the asr gene. N-terminal sequencing and site-directed mutagenesis revealed the two processing sites in the Asr protein precursor. Deletion of amino acids encompassing the processing site required for release of the 8-kDa protein resulted in an acid-sensitive phenotype similar to that observed for the asr null mutant, suggesting that the 8-kDa product plays an important role in the adaptation to acid shock. Analysis of Asr:PhoA fusions demonstrated a periplasmic location for the Asr protein after removal of the signal peptide. Homologues of the asr gene from other Enterobacteriaceae were cloned and shown to be induced in E. coli under acid shock conditions

Otpornost na antibiotike bakterija Enterococcus spp. izdvojenih iz stoke u Litvi.

105 isolates of Enterococcus spp. were selected as representative samples from different herds of pigs (n=25), cattle (n=46) and poultry (n=34). Antimicrobial susceptibility was determined according to epidemiological cut-off values. The highest number of strains demonstrated epidemiological resistance to lincomycin (78%), tetracycline, (65%), flavomycin (59%) and erythromycin (55%). The smallest number of strains was resistant to linezolid (1%) and tigecycline (2%). Six percent of all tested strains were epidemiologically resistant to ciprofloxacin, vancomycin and daptomycin. Cattle isolates showed the most frequent resistance to fl avomycin (71%), lincomycin (54%), tetracycline (45%), streptomycin (40%) and erythromycin (40%). Enterococci isolated from pigs showed the highest resistance to tetracycline and lincomycin (92%), erythromycin (76%), kanamycin (56%) and streptomycin (52%). All strains isolated from poultry were epidemiologically resistant to lincomycin. The most frequent resistance of poultry strains was also demonstrated to tetracycline (72%), erythromycin (63%), streptomycin (50%), flavomycin (48%) and tylosin (47%). However all strains isolated from poultry were susceptible to chloramphenicol, quinupristin/dalfopristin, linezolid and bacitracin.Ukupno je 105 izolata bakterija Enterococcus spp. bilo odabrano kao predstavnici iz različitih uzgoja svinja (n = 25), goveda (n = 46) i peradi (n = 34). Osjetljivost prema antimikrobnim tvarima određivana je na osnovi epidemioloških graničnih vrijednosti. Većina izolata bila je otporna prema linkomicinu (78%), tetraciklinu (65%), flavomicinu (59%) i eritromicinu (55%). Najmanje izolata bilo je otporno prema linezolidu (1%) i tigeciklinu (2%). Šest posto svih pretraženih sojeva bilo je otporno na ciprofloksacin, vankomicin i daptomicin. Izolati iz goveda bili su najčešće otporni na flavomicin (71%), linkomicin (54%), tetraciklin (45%), streptomicin (40%) i eritromicin (40%). Enterokoki izdvojeni iz svinja bili su najotporniji prema tetraciklinu i linkomicinu (92%), eritromicinu (76%), kanamicinu (56%) i streptomicinu (52%). Svi izolati iz peradi bili su otporni prema linkomicinu. Sojevi iz peradi također su bili najčešće otporni prema tetraciklinu (72%), eritromicinu (63%), streptomicinu (50%), flavomicinu (48%) i tilozinu (47%). Međutim svi sojevi izdvojeni iz peradi bili su osjetljivi prema kloramfenikolu, kvinupristinu/dalfopristinu, linezolidu i bacitracinu