Natan Keller - Academia.edu (original) (raw)

Papers by Natan Keller

Arthritis Research & Therapy, Jan 26, 2001

We discuss the presence of anti-keratin antibodies (AKA) of the IgG class in patients with define... more We discuss the presence of anti-keratin antibodies (AKA) of the IgG class in patients with defined juvenile idiopathic arthritis (JIA). An indirect immunofluorescence test and rat oesophagus substrate was used for the detection and quantification of AKA antibodies in patients´ sera. Overall 33/60 patients with JIA had sera positive for AKA (55 %, P = 0,0001) ranging from 1:10 to 1:160 dilutions. Following idiopathic arthritis of childhood classification criteria AKA occurred in 2/7 patients with systemic disease (28,6 %), in 13/30 patients with RF negative polyarthritis (43,3 %, P = 0,008) and in 15/18 RF positive polyarthritis (83,3 %, P = 0,000002). AKA were also found in a small cohort of patients with oligoarthritis (1/3) and psoriatic arthritis (2/2). AKA positivity occurred in 3/26 healthy controls at a 1:20 dilution. The presence of AKA was correlated as well as with the severity of the disease. Our study revealed that AKA was present overall in 18/29 patients (62%) with severe JIA and in 12/26 patients (46,2 %) with non-severe disease, however this did not reach statistical significance (P = 0,18). We also observed that AKA remained positive regardless of disease activity. AKA were detectable in 55,6 % patients with active JIA and in 48,6 % patients in the complete or near remission. Acknowledgement: This research was supported by a European Commission (Acronym: EUROBANK, contract no: QOL-2000-14.1), web site http://www.ncl.ac.uk and by grant of 2nd Medical Faculty, Charles University in Prague, VZ no. 111300003. P2 The significance of antibodies to cyclic citrullinated peptide, antikeratin antibodies, antiperinuclear factor, rheumatoid factor isotypes and HLA shared epitope in prediction of erosive disease in early rheumatoid arthritis patients

Thrombosis and Haemostasis, 1994

Replacement therapy for patients with hemophilia A postoperatively or for major hemorrhage, admin... more Replacement therapy for patients with hemophilia A postoperatively or for major hemorrhage, administered as a continuous infusion, is efficient and reduces the requirement for factor VIII (F VIII). The convenience of the method is increased by using a minipump and not diluting the concentrate further after reconstitution. A monoclonally purified F VIII concentrate (Monoclate-P), was evaluated for its stability after reconstitution in different infusion systems, for its microbiological safety as well as clinical safety and efficacy in continuous infusion. The F VIII activity was unaffected by 2 of the 3 infusion systems at room temperature during 15 days, whereas in the third (CADD-1) it decreased below 80% of initial value after 3-7 days. Addition of heparin (1 U/ml) or low molecular weight heparin (1 anti-Xa U/ml), which are used to prevent thrombophlebitis at the site of infusion, did not affect the stability. Nine out of 9 samples taken from the infusion systems after 3 days and again after 7 days were sterile. After inoculation with Staphylococcus aureus or Escherichia coli the bacterial growth in samples of the reconstituted concentrate was not different from that in lidocaine in saline or heparin in saline. F VIII was given in continuous infusion with a minipump (Infu-Med) to 12 patients undergoing major surgery and 8 patients with major hemorrhage for a total of 157 days. A progressive decrease of the clearance was seen during the first 5 days of infusion from 3.0 to 1.7 ml/kg/h. Hemostasis was effectively achieved, and no infectious complications were registered.(ABSTRACT TRUNCATED AT 250 WORDS)

Thrombosis and Haemostasis, 1996

SummaryRecombinant factor Vila (rFVIIa; NovoSeven®) is a recent addition to the hemostatic altern... more SummaryRecombinant factor Vila (rFVIIa; NovoSeven®) is a recent addition to the hemostatic alternatives for the treatment of hemophiliacs with inhibitors. A drawback in the use of rFVIIa has been its half-life of only about 2 h, which necessitates very frequent and punctual injections. We evaluated the stability of reconstituted, but not further diluted, rFVIIa in 3 infusion systems (WalkMedTM 350 and CADD®-Plus minipumps and Meddex 2001 syringe pump). The factor VII (F VII) activity was maintained for at least 3 days at room temperature with only a minor and clinically insignificant increase in oxidized forms of rFVIIa and minimal leaching of the plastic softeners di-butylphthalate and di-octylphthalate after 24–48 h. Addition of heparin, 5–10 U/ml, to reconstituted rFVIIa caused a loss of about 50% of the activity within 4 h of storage in the infusion system, whereas low molecular weight heparin had no such effect. Repeated samples showed that the infusion systems maintained steri...

Molecular Mimicry, Microbes, and Autoimmunity

The immunogenicity of self-like microbial molecules is strikingly illustrated in several cases of... more The immunogenicity of self-like microbial molecules is strikingly illustrated in several cases of murine and human systemic lupus erythematosus (SLE). Several indirect arguments support the idea that microbial agents influence the course of antiphospholipid syndrome (APS). An association between APS and pathogens was documented, such as hepatitis C virus, Salmonella lipopolysaccharide, and Mycoplasma penetrans, a rare bacterium that has so far only been found in human immunodeficiency virus (HlV)-infected persons and that was isolated from the blood and throat of a non-HIV-infected patient with primary APS. The molecular basis of antigen mimicry by anti-idiotypic antibodies was studied extensively. On the basis of Jerne's theory, after immunization with an autoantibody that carries a specific idiotype (Abl), naive mice develop an antiautoantibody (anti-Id; which is also known as Ab2) and then generate anti-anti-Id (Ab3) a few weeks later. Immunization of naive mice with anticardiolipin β2GPI-dependent MAbs and polyclonal antibodies or their corresponding scFv, such as Abl, resulted in the production in the inoculated mice of autoantibody directed to cardiolipin and to the cardiolipin β2GPI-dependent antibody Ab3. Studies on experimental lupus and experimental APS prove the existence of molecular mimicry between pathogens and the autoantigens involved in experimental lupus and APS. Recognition of multiple antigens and epitopes is evident in insulin-dependent diabetes mellitus, SLE, APS, rheumatoid arthritis, PBC, and probably most autoimmune diseases, with spreading of the named epitope leading to autoantibody spread.

Journal of Clinical Microbiology, Sep 1, 2008

Carbapenem resistance among Enterobacteriaceae is an emerging problem worldwide. Klebsiella pneum... more Carbapenem resistance among Enterobacteriaceae is an emerging problem worldwide. Klebsiella pneumoniae carbapenemase (bla KPC) enzymes are among the most common ␤-lactamases described. In this study, we report the development and validation of a real-time PCR (q-PCR) assay for the detection of bla KPC genes using TaqMan chemistry. The q-PCR amplification of bla KPC DNA was linear over 7 log dilutions (r 2 ‫؍‬ 0.999; slope, 3.54), and the amplification efficiency was 91.6%. The q-PCR detection limit was 1 CFU, and there was no cross-reaction with DNA extracted from several multidrug-resistant bacteria. Perianal/rectal swabs (n ‫؍‬ 187) collected in duplicate from 128 patients admitted to Sheba Medical Center surgical intensive care units were evaluated for the presence of carbapenem-resistant bacteria by culturing on MacConkey agar-pluscarbapenem disks and for bla KPC genes by q-PCR. Carbapenem-resistant organisms, all K. pneumoniae, were isolated from 47 (25.1%) of the 187 samples collected, while bla KPC genes were detected in 54 (28.9%) of the patient samples extracted by the NucliSENS easyMAG system. Of these, seven samples were positive for bla KPC genes by q-PCR but negative for carbapenem resistance by culture, while all samples in which no carbapenemresistant bacteria were detected by culture also tested negative by q-PCR. Thus, the sensitivity and specificity of the q-PCR assay after extraction by the NucliSENS easyMAG system were 100% and 95%, respectively. Similar values were obtained after DNA extraction by the Roche MagNA Pure LC instrument: 97.9% sensitivity and 96.4% specificity. Overall, the bla KPC q-PCR assay appears to be highly sensitive and specific. The utilization of q-PCR will shorten the time to bla KPC detection from 24 h to 4 h and will help in rapidly isolating colonized or infected patients and assigning them to cohorts.

Clinical Infectious Diseases, Mar 1, 2004

Journal of Clinical Microbiology, Jul 1, 2011

Rapid detection of drug-resistant bacteria in clinical samples plays an instrumental role in pati... more Rapid detection of drug-resistant bacteria in clinical samples plays an instrumental role in patients' infection management and in implementing effective infection control policies. In the study described in this report, we validated a multiplex TaqMan real-time quantitative PCR (qPCR) assay for the detection of bla KPC genes and the human RNase P gene in Bactec blood culture bottles. The MagNA Pure LC (version 2.0) instrument was utilized to extract nucleic acids from the inoculated broth, while bovine serum albumin (BSA) was utilized as the PCR inhibitor reliever. The multiplex assay, which was specific for the detection of bla KPC genes, had a limit of detection of 19 CFU per reaction mixture with human blood-spiked Bactec bottles. Of the 323 Bactec blood culture sets evaluated, the same 55 (17%) blood cultures positive for carbapenem-resistant bacteria by culture were also positive by the validated qPCR assay. Thus, the sensitivity, specificity, positive predictive value, and negative predictive value of the qPCR assay compared to the results of culture were all 100%. bla KPC genes were also detected from the same Bactec bottle broth after manual extraction with a QIAamp DNA minikit; however, there was an average 3-threshold-cycle delay in the qPCR readings. With the limited therapeutic options available, the accurate and rapid detection of bla KPC-possessing bacteria by the described bla KPC /RNase P assay will be a crucial first step in ensuring optimal clinical outcomes and infection control.

ObjectivesTo compare the burden of environmental shedding of toxigenic C. difficile among asympto... more ObjectivesTo compare the burden of environmental shedding of toxigenic C. difficile among asymptomatic carriers, C. difficile infected (CDI) patients and non-carriers, in an inpatient non-epidemic setting.MethodsC. difficile carriage was determined by positive toxin-B PCR from rectal swabs of asymptomatc patients. Active CDI was defined as a positive 2-step EIA/PCR test in patients with >3 unformed stools/24 hours. C. difficile environmental contamination was assessed by obtaining specimens from 10 sites in the patients’ rooms. Toxigenic strains were identified by PCR. We created a contamination scale to define the overall level of room contamination that ranged from clean to heavy contamination.Results117 rooms were screened; 70 rooms inhabited by C. difficile carriers, 30 rooms by active CDI patients and 17 rooms by non C. difficile -carriers (Control). In the carrier rooms 29 (41%) had more than residual contamination, from which 17 (24%) were heavily contaminated. In the CDI ...

Journal of medical microbiology, 2000

This study was undertaken to determine whether the ability of group A streptococci to persist in ... more This study was undertaken to determine whether the ability of group A streptococci to persist in the throat following antibiotic therapy corresponded with their capacity to adhere to and be internalised by epithelial cells. The study employed a HEp-2 cell model to examine the adherence and internalisation capacities of 42 strains (13 from asymptomatic patients with bacteriological eradication failure and 29 from patients with bacterial eradication). The adherence and internalisation efficiencies of strains from symptomless carriers were significantly higher. The average adherence efficiency of the carriers' strains was 53 (SEM 6)% versus 35 (SEM 5)% in control strains. The average internalisation efficiency of the carriers' strains was 13.4 (SEM 4)% compared with 4.4 (SE 1.6)% in the control group. The results are in agreement with the hypothesis that, in a significant number of cases, streptococcal internalisation might contribute to eradication failure and persistent throa...

FEMS Immunology and Medical Microbiology, 1997

The assessment of deuteroporphyrin-hemin complex as an agent for the treatment of burn wounds inf... more The assessment of deuteroporphyrin-hemin complex as an agent for the treatment of burn wounds infected with a multipledrug resistant strain of Staphylococcus aureus was performed. The effect of the porphyrin on the survival of the infectious bacteria was first assayed in culture, and later tested as well in a burned infected animal model. The addition of deuteroporphyrin and hemin, separately or together (as a complex) to a growing culture of S. aureus was monitored during 8 hours. It was found that deuteroporphyrin alone was strongly bactericidal only after photosensitization. On the other hand, hemin alone was moderately bactericidal but light independent. A combination of both deuterophyrin and hemin was extremely potent even in the dark and did not require illumination to eradicate the bacteria. The in vivo experiments by application of the above porphyrins in combination to infected burn wounds in guinea pigs was an effective way to reduce dramatically the contaminating S. aureus. Reduction of more than 99% of the viable bacteria was noted after the porphyrin mixture was dropped on the eschar or injected into the eschar, an effect that lasted for up to 24 hours. The deuteroporphyrinhemin complex may be suggested as a new bactericidal treatment of S. aureus infected burns since it was found to be a potent and promising anti-Staphylococcal agent.

Identifying how and where pathogens acquire antibiotic resistance is crucial to developing effect... more Identifying how and where pathogens acquire antibiotic resistance is crucial to developing effective strategies to limit its spread. Many bacterial species carry and share plasmids harboring antibiotic resistant genes. Plasmids are mobile genetic elements whose horizontal transmission is difficult to assess through genomic comparison due to assembly issues when using short-read sequencing alone. In this study, we use hybrid assembly to fully assemble plasmids that are shared between different Enterobacteriaceae isolated from patients and sinks in the same hospital rooms. We isolated and sequenced pairs of carbapenem resistantEnterobacter hormaecheisubsp.xiangfangensisandKlebsiella pneumoniaefrom patients and sinks within the same hospital room. The isolate pairs share plasmids that putatively confer antibiotic resistance, including carbapenem resistance. These plasmids differ by few mutations and structural changes, while the isolates carry unique plasmids. Together, this suggests t...

Frontiers in Microbiology

Influenza A and other respiratory viruses, circulate each winter and cause respiratory illness th... more Influenza A and other respiratory viruses, circulate each winter and cause respiratory illness that can lead to severe complications in hospitalized patients. During the COVID-19 pandemic, only a few cases of respiratory viruses were detected in Israel. Our study applied RT-PCR to examine 13,674 samples collected from patients hospitalized with respiratory symptoms in 2019, 2020, and 2021 and the first half of the 2022 winter. A sharp increase in influenza A(H3N2) cases was observed in winter 2021-2022 as compared to 2020, followed by a sudden decrease in influenza cases after the detection of the SARS-CoV-2 omicron variant in Israel. Comparison of the area under the curve (AUC) of influenza infection rates during 7 consecutive winter seasons found that the minimal AUC between 2015 and 2020 was 281.1, while in 2021-2022, it was significantly lower (162.6 AUC; p = 0.0017), although the percentage of positive influenza cases was similar to those of previous years. The presented findin...

Thekinetics oftumornecrosis factor alpha (TNF-ca) production, thecorrelation between cytokine lev... more Thekinetics oftumornecrosis factor alpha (TNF-ca) production, thecorrelation between cytokine levels and mortality ratesafter lethal challenge, andtheproduction ofa native inhibitor ofTNF-aactivity was investigated inmiceimmunized withformalin-kilied Escherichia coli. Groups ofmicewereinjected for8weeks witheither untreated bacteria orbacteria treated with 0.5 MICofaztreonam andsubsequently challenged with 10050%lethal doses ofviable E.coli. Micereceiving saline only(controls) diedwithin 24h.Themortality of miceimmunized withaztreonam-treated E.coli was significantly lowerthanthatofmiceimmunized with untreated E.coli. There were no measurable levels ofTNF-ceinseraobtained fromcontrol miceduring the entire period ofimmunization. TNF-ca levels ranging from90to306U/mlwere measured 90minafter each vaccination inseraobtained frommiceimmunized withuntreated E.coli. Serafrommiceimmunized with antibiotic-treated E.coli showedlowerTNF-alevels, ranging from40to128U/ml. TNF-alevels measured 90...

Infection and Immunity, 1993

The kinetics of tumor necrosis factor alpha (TNF-alpha) production, the correlation between cytok... more The kinetics of tumor necrosis factor alpha (TNF-alpha) production, the correlation between cytokine levels and mortality rates after lethal challenge, and the production of a native inhibitor of TNF-alpha activity was investigated in mice immunized with formalin-killed Escherichia coli. Groups of mice were injected for 8 weeks with either untreated bacteria or bacteria treated with 0.5 MIC of aztreonam and subsequently challenged with 100 50% lethal doses of viable E. coli. Mice receiving saline only (controls) died within 24 h. The mortality of mice immunized with aztreonam-treated E. coli was significantly lower than that of mice immunized with untreated E. coli. There were no measurable levels of TNF-alpha in sera obtained from control mice during the entire period of immunization. TNF-alpha levels ranging from 90 to 306 U/ml were measured 90 min after each vaccination in sera obtained from mice immunized with untreated E. coli. Sera from mice immunized with antibiotic-treated E...

Scientific reports, Apr 24, 2017

Hospitalized patients are at increased risk for acquiring healthcare-associated infections (HAIs)... more Hospitalized patients are at increased risk for acquiring healthcare-associated infections (HAIs) and inadequate nutrition. The human intestinal microbiota plays vital functions in nutrient supply and protection from pathogens, yet characterization of the microbiota of hospitalized patients is lacking. We used 16S rRNA amplicon sequencing to characterize the global pattern of microbial composition of fecal samples from 196 hospitalized patients with suspected infectious diarrhea in comparison to healthy, non-hospitalized subjects (n = 881), and to traditional culture results. We show that hospitalized patients have a significant rise in α-diversity (richness within sample) from birth to <4 years of age, which continues up to the second decade of life. Additionally, we noted a profoundly significant increase in taxa from Proteobacteria phylum in comparison to healthy subjects. Finally, although more than 60% of hospitalized samples had a greater than 10% abundance of Proteobacteri...

Oncotarget, Jan 23, 2015

The seasonal influenza vaccine is currently the most effective preventive modality against influe... more The seasonal influenza vaccine is currently the most effective preventive modality against influenza infection. Nasopharyngeal samples of vaccinated and non-vaccinated patients presenting with Influenza-like-illness (ILI) were collected from over 20 outpatient clinics located in different geographic parts of Israel and were tested for the presence of influenza viruses (influenza A and influenza B). Here we show, that in the 2014-2015 season, the vaccine that included the A/Texas/50/2012 H3N2 virus was ineffective. Significant numbers of individuals vaccinated with the 2014-2015 vaccine, of all ages, were infected with influenza A (H3N2), manifesting similar symptoms as the non-vaccinated group. We further demonstrate that the Israeli circulating influenza A(H3N2) virus was different than that included in the 2014-2015 northern hemisphere vaccine, and that antibodies elicited by this vaccine were significantly less efficient in neutralizing influenza A(H3N2) infection.

Clinical Infectious Diseases, 2014

Background. Listeria monocytogenes is a foodborne pathogen that causes life-threatening infection... more Background. Listeria monocytogenes is a foodborne pathogen that causes life-threatening infections in elderly, immunocompromised, and pregnant women. In pregnancy it may cause fetal loss or a preterm delivery, and the neonate is prone to neonatal sepsis and death. Methods. We created a cohort of all L. monocytogenes cases during 10 years (1998-2007) in Israel, by a comprehensive review of cases in hospitals throughout the country and cases reported to the Ministry of Health. Results. One hundred sixty-six pregnancy-related listeriosis cases were identified, resulting in a yearly incidence of 5-25 cases per 100 000 births. Presentation associated with fetal demise was more common in the second trimester (55.3%), and preterm labor (52.3%) and abnormal fetal heart rate monitoring (22.2%) were more common in the third trimester (P = .001). Fetal viability was low in the second trimester (29.2%) and much higher (95.3%) in the third trimester. Each additional week of pregnancy increased the survival chance by 33% (odds ratio, 1.331 [95% confidence interval, 1.189-1.489]). A single case of maternal mortality was identified. Listeria monocytogenes serotype 4b was more common in pregnancy-related than in non-pregnancy-related cases (79.5% vs 61.3%, P = .011). Pulsed-field gel electrophoresis analysis suggested that 1 pulsotype is responsible for 35.7% of the pregnancy cases between 2001 and 2007. This clone is closely related to the Italian gastroenteritis-associated HPB2262 and the invasive US Scott A L. monocytogenes strains. Conclusions. Our survey emphasizes the high rate of pregnancy-related listeriosis in Israel and shows that specific clones might account for this.

Postgraduate Medical Journal, 2000

Summary Aspergillus is an opportunistic nosocomial fungus generally associated with a high mortal... more Summary Aspergillus is an opportunistic nosocomial fungus generally associated with a high mortality rate.A nigerhas been rarely associated with infection, and most cases have occurred in patients who have recently undergone heart surgery or in immunocompromised patients. We present a case of an immunocompetent patient with A niger endocarditis which illustrates the difficulties in diagnosis and the possible insidious course of fungal endocarditis.

New England Journal of Medicine, 2006

Medical Mycology, 2006

We report a case of endogenous endophthalmitis due to a sporodochial-forming species of Phialemon... more We report a case of endogenous endophthalmitis due to a sporodochial-forming species of Phialemonium curvatum. The infection led to the enucleation of the affected eye, but there was no evidence of systemic dissemination. The isolated P. curvatum produced aggregates of phialides, many occurring on coils or in verticils, which eventually develop into sporodochia. The initial and postenucleation isolates revealed they were identical to strains of P. curvatum from Israel causing disseminated disease in patients practicing intracavernous autoinjections for the treatment of erectile dysfunction. The reported case had unusual clinical and microbiological features. Despite the route of acquisition and the lack of systemic antifungal therapy, the infection did not spread beyond the eye. The morphology of the phialides aggregates was also unique, and the distinction between Volutella and Acremonium is discussed. This case expands the spectrum of infections due to Phialemonium species, and reveals a novel way of developing fungal endophthalmitis.