Five carbapenem-resistant Acinetobacter baumannii isolates, collected from the United Arab Emirates in 2006, were investigated to identify the mechanism(s) responsible for carbapenem resistance. ...Genotyping was performed by pulsed-field gel electrophoresis, and the location of the blaOXA-23 gene was determined by using the endonuclease I CeuI technique and mating-out assays. The four isolates in which the blaOXA-23 gene was located on the chromosome within a Tn2006 composite transposon were clonally related. The single nonclonally related isolate harboured the blaOXA-23 gene on a 70-kb transferable plasmid. This study provides the first description of the dissemination of carbapenem-resistant A. baumannii isolates carrying Tn2006 on their chromosome. It is also the first report of OXA-23-producing A. baumannii isolates in the Middle East.
Summary Klebsiella pneumoniae carbapenemases (KPCs) were originally identified in the USA in 1996. Since then, these versatile β-lactamases have spread internationally among Gram-negative bacteria, ...especially K pneumoniae , although their precise epidemiology is diverse across countries and regions. The mortality described among patients infected with organisms positive for KPC is high, perhaps as a result of the limited antibiotic options remaining (often colistin, tigecycline, or aminoglycosides). Triple drug combinations using colistin, tigecycline, and imipenem have recently been associated with improved survival among patients with bacteraemia. In this Review, we summarise the epidemiology of KPCs across continents, and discuss issues around detection, present antibiotic options and those in development, treatment outcome and mortality, and infection control. In view of the limitations of present treatments and the paucity of new drugs in the pipeline, infection control must be our primary defence for now.
Abstract Background Although Klebsiella pneumoniae is the second most common cause of Gram-negative bloodstream infections, its epidemiology has not been defined in a nonselected population. We ...sought to describe the incidence of, risk factors for, and outcomes associated with K. pneumoniae bacteremia. Methods Population-based surveillance for K. pneumoniae bacteremia was conducted in the Calgary Health Region (population 1.2 million) from 2000 to 2007. Results A total of 640 episodes of K. pneumoniae bacteremia were identified for an overall annual population incidence of 7.1 per 100,000; 174 (27%) were nosocomial, 276 (43%) were healthcare-associated community onset, and 190 (30%) were community acquired. Elderly patients and men were at highest risk for K. pneumoniae bacteremia. Dialysis, solid-organ transplantation, chronic liver disease, and cancer were the most important risk factors for acquiring K. pneumoniae bacteremia. Rates of resistance to trimethoprim/sulfamethoxazole increased significantly during 2000 to 2007. The case fatality rate was 20%, and the annual population mortality rate was 1.3 per 100,000. Increasing age, nosocomial acquisition, non-urinary and non-biliary focus of infection, and several comorbid illnesses were independently associated with an increased risk of death. Conclusion This is the first population-based study to document the major burden of illness associated with K. pneumoniae bacteremia and identifies groups at increased risk of acquiring and dying of these infections.
Five carbapenem-resistant Acinetobacter baumannii isolates, collected from the United Arab Emirates in 2006, were investigated to identify the mechanism(s) responsible for carbapenem resistance. ...Genotyping was performed by pulsed-field gel electrophoresis, and the location of the bla sub(OXA-23) gene was determined by using the endonuclease I CeuI technique and mating-out assays. The four isolates in which the bla sub(OXA-23) gene was located on the chromosome within a Tn2006 composite transposon were clonally related. The single non-clonally related isolate harboured the bla sub(OXA-23) gene on a 70-kb transferable plasmid. This study reports on the dissemination of OXA-23-producing A.baumannii isolates in the Middle East.
A unique heparinase was isolated from a recently discovered Gram-negative soil bacterium. The enzyme (heparinase III) was purified by hydroxylapatite chromatography, chromatofocusing, and gel ...permeation chromatography. The enrichment was 48x, and the specific activity of catalytically pure heparinase was 127 IU/mg of protein. Similar to the heparinase I from Flavobacterium heparinum, heparinase III also degrades heparin to mainly disaccharide fragments. It is specific for heparin and also breaks down heparan sulfate, but not hyaluronic acid and chondroitin sulfate. Heparinase III, however, differs markedly from heparinase I in several other aspects: it has a higher molecular mass (94 versus 43 kDa), pI (9.2 versus 8.5), its Km and kcat are different, and it has a higher energy of activation (15.6 versus 6.3 kcal/mol). Optimal activity was also found at higher pH (7.6 versus 6.5) and temperature (45 versus 37 degrees C). Furthermore, the amino acid composition of heparinase III is quite different from that of heparinase I.
Objectives: To characterize the β-lactam resistance mechanisms of two clinical isolates of cefotaxime-resistant Haemophilus parainfluenzae recovered from patients in South Africa. Methods: The ...relatedness of isolates and plasmids was assessed using PFGE and restriction enzyme analysis, respectively. Plasmid-mediated and chromosomally integrated blaTEM genes and ftsI genes were sequenced, and the plasmid-mediated blaTEM-15 was used to transform a range of control organisms. Results: The two isolates were found to be unique according to PFGE, but had an identical 3.7 kb plasmid encoding a TEM-15 β-lactamase. Both isolates also had substitutions in penicillin binding protein 3 (PBP3) consistent with substitutions known to exist in β-lactamase-negative ampicillin-resistant (BLNAR) strains of Haemophilus influenzae . The cefotaxime MICs for control strains of H . influenzae , H . parainfluenzae and BLNAR H . influenzae transformed with the plasmid-mediated blaTEM-15 were 1.0, 1.0 and 4.0 mg/L, respectively, compared with 16.0 and 8.0 mg/L, respectively, for the two parent H. parainfluenzae. Conclusions: The high-level cefotaxime resistance in the H . parainfluenzae isolates was due to a combination of a plasmid-mediated TEM-15 extended-spectrum β-lactamase with altered PBP3 probably contributing. Other contributing resistance mechanisms could not be excluded. PUBLICATION ABSTRACT
Melatonin is present in human semen, and may affect sperm motility. The presence of melatonin receptors on spermatozoa has not yet been reported. Detection of melatonin-binding sites may be limited ...because of the masking of such sites by sialic acid. Spermatozoa were obtained from eligible human donors, incubated with neuraminidase to remove sialic acid residues, and saturation binding assays were carried out using 2-125I-melatonin as a receptor probe. Consistent 125I-melatonin binding could only be obtained after spermatozoa were treated with neuraminidase. Scatchard analysis revealed a low-affinity binding site (ML-2) with a Kd value of 127 +/- 6 nM and a Bmax of 25 +/- 4.5 fmol/mg protein. These results present evidence of melatonin-binding sites in spermatozoa. Sialic acid possibly regulates the binding of melatonin to these sites.
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