The Open Microbiology Journal




ISSN: 1874-2858 ― Volume 13, 2019
RESEARCH ARTICLE

Detection of Plasmid-Mediated qnr Genes Among the Clinical Quinolone-Resistant Escherichia coli Strains Isolated in Tehran, Iran



Reza Ranjbar1, *, Sajjad S. Tolon1, Mehrdad Sami2, Reza Golmohammadi1
1 Molecular Biology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
2 Department of Clinical Sciences, School of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad, Iran

Abstract

Background:

Escherichia coli is one of the most important bacterial agents to cause urinary tract infections. Inappropriate and unnecessary administration of antibiotics has led to an increase in the appearance of multidrug-resistant E. coli isolates, limiting treatment options. The increase in a number of resistant strains of bacteria is a major concern of health authorities worldwide.

Objective:

The purpose of this study was to determine the presence of the qnr genes among E. coli isolated from UTIs of patients in Baqiyatallah hospital in Tehran province, Iran.

Method:

Clinical urine samples of patients with suspected urinary tract infection were collected by standard methods in sterile disposable containers. After analysis of urine, microscopic observations and culture analysis, the bacterial genome was extracted by boiling method. PCR for detection of qnr genes including qnrA, qnrB and qnrS was done by specific primers, then PCR products were run using gel electrophoresis and visualized by gel documentation system.

Results:

In the present study among the 95 isolates, 60 strains were resistant to nalidixic acid. PCR showed that 92 strains were positive for qnrS. The qnrA and qnrB genes were not found among the clinical isolates.

Conclusion:

Our finding indicates a high level of resistance against nalidixic acid among E. coli isolates recovered from the patients with UTI. Also, the high frequency of qnrS imposes the importance of survey of molecular and genetic analysis of mechanisms of quinolone resistance in E. coli strains.

Keywords: Antibiotic resistance, E. coli, qnr, PCR, Clinical strains, UTIs.


Article Information


Identifiers and Pagination:

Year: 2018
Volume: 12
First Page: 248
Last Page: 253
Publisher Id: TOMICROJ-12-248
DOI: 10.2174/1874285801812010248

Article History:

Received Date: 29/3/2018
Revision Received Date: 3/7/2018
Acceptance Date: 10/7/2018
Electronic publication date: 31/07/2018
Collection year: 2018

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© 2018 Ranjbar et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: (https://creativecommons.org/licenses/by/4.0/legalcode). This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


* Address correspondence to this author at the Molecular Biology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran; Tel: 00989123048157; E-mail: ranjbarre@gmail.com




1. INTRODUCTION

Escherichia coli (E. coli) is a commonplace bacteria that has been isolated from different sources [1Ranjbar R, Masoudimanesh M, Dehkordi FS, Jonaidi-Jafari N, Rahimi E. Shiga (Vero)-toxin producing Escherichia coli isolated from the hospital foods; virulence factors, o-serogroups and antimicrobial resistance properties. Antimicrob Resist Infect Control 2017; 6: 4.[http://dx.doi.org/10.1186/s13756-016-0163-y] [PMID: 28074125] , 2Ranjbar R, Hosseini S, Zahraei-salehi T, Kheiri R, Khamesipour F. Investigation on prevalence of Escherichia coli strains carrying virulence genes ipaH, estA, eaeA and bfpA isolated from different water sources. Asian Pac J Trop Dis 2016; 6(4): 278-83.[http://dx.doi.org/10.1016/S2222-1808(15)61031-3] ]. E. coli is an important gram-negative bacteria with the potential to cause serious disease such as Urinary Tract Infections (UTIs) [3Jacobsen SM, Stickler DJ, Mobley HL, Shirtliff ME. Complicated catheter-associated urinary tract infections due to Escherichia coli and Proteus mirabilis. Clin Microbiol Rev 2008; 21(1): 26-59.[http://dx.doi.org/10.1128/CMR.00019-07] [PMID: 18202436] ]. UTIs, which are recognized as the most commonly reported nosocomial infections, account for up to 35% of infections associated with the health-care system, and E. coli bacteria is the most important cause of UTIs [4Wilson ML, Gaido L. Laboratory diagnosis of urinary tract infections in adult patients 2004.[http://dx.doi.org/10.1086/383029] ]. More than thirty patterns for pyelonephritis and cystitis [5Anvarinejad M, Farshad Sh, Ranjbar R, Giammanco GM, Alborzi A, Japoni A. Genotypic analysis of E. coli strains isolated from patients with cystitis and pyelonephritis. Iran Red Crescent Med J 2012; 14(7): 408-16.[PMID: 22997556] ] and variety of virulence genes among uropathogenic E. coli strains [6Jahandeh N, Ranjbar R, Behzadi P, Behzadi E. Uropathogenic Escherichia coli virulence genes: Invaluable approaches for designing DNA microarray probes. Cent European J Urol 2015; 68(4): 452-8.[PMID: 26855801] ] were obtained. Due to the widespread resistance to other antibiotics, fluoroquinolones that are synthetic and broad-spectrum antibacterial agents often used for the treatment of UTIs in many countries [7Kariuki S, Revathi G, Corkill J, et al. Escherichia coli from community-acquired urinary tract infections resistant to fluoroquinolones and extended-spectrum beta-lactams. J Infect Dev Ctries 2007; 1(3): 257-62.[PMID: 19734602] -9Ambrozic Avgustin J, Keber R, Zerjavic K, Orazem T, Grabnar M. Emergence of the quinolone resistance-mediating gene aac(6′)-Ib-cr in extended-spectrum-beta-lactamase-producing Klebsiella isolates collected in Slovenia between 2000 and 2005. Antimicrob Agents Chemother 2007; 51(11): 4171-3.[http://dx.doi.org/10.1128/AAC.01480-06] [PMID: 17846136] ].

The emergence of various isolates of the drug-resistant E. coli occurs due to the inappropriate and unnecessary administration of these antibiotics and leads to limiting the treatment options. In a recent study, Ranjbar et al. showed highly (96%) antibiotic resistance on clindamycin and frequency of different ESBLs genes among E. coli strains in the surface water sources [10Ranjbar R, Sami M. Genetic investigation of Beta-Lactam associated antibiotic resistance among Escherichia Coli strains isolated from water sources. Open Microbiol J 2017; 11(1): 203-10.[http://dx.doi.org/10.2174/1874285801711010203] [PMID: 29151997] ]. Some studies indicated that urine specimens from isolates of different strains of E. coli have high resistance to one or more than one antibiotics [11Ranjbar R, Haghi-Ashtiani MT, Jonaidi Jafari N, Abedini M. The prevalence and antimi-crobial susceptibility of bacterial uropathogens isolated from pediatric patients. Iran J Public Health 2009; 38(2): 134-8.-13Tajbakhsh E, Khamesipour F, Ranjbar R, Ugwu IC. Prevalence of class 1 and 2 integrons in multi-drug resistant Escherichia coli isolated from aquaculture water in Chaharmahal Va Bakhtiari province, Iran. Ann Clin Microbiol Antimicrob 2015; 14: 37.[http://dx.doi.org/10.1186/s12941-015-0096-y] [PMID: 26227260] ]. Plasmid profile distinguished more strains than the antimicrobial susceptibility pattern [14Farshad S, Ranjbar R, Japoni A, Hosseini M, Anvarinejad M, Mohammadzadegan R. Microbial susceptibility, virulence factors, and plasmid profiles of uropathogenic Escherichia coli strains isolated from children in Jahrom, Iran. Arch Iran Med 2012; 15(5): 312-6.[PMID: 22519382] ]. The increase in a number of resistant strains of bacteria is a major concern of health authorities worldwide. Resistance to quinolone is mediated by different routes including mutations in DNA gyrase and topoisomerase subunits [15Komp Lindgren P, Karlsson A, Hughes D. Mutation rate and evolution of fluoroquinolone resistance in Escherichia coli isolates from patients with urinary tract infections. Antimicrob Agents Chemother 2003; 47(10): 3222-32.[http://dx.doi.org/10.1128/AAC.47.10.3222-3232.2003] [PMID: 14506034] ], decreased outer membrane permeability through porin changes and overexpression of naturally occurring efflux [16Fernández L, Hancock RE. Adaptive and mutational resistance: Role of porins and efflux pumps in drug resistance. Clin Microbiol Rev 2012; 25(4): 661-81.[http://dx.doi.org/10.1128/CMR.00043-12] [PMID: 23034325] ]. Moreover, mobile genetic elements, such as plasmids, play a role in quinolone resistance. The plasmid-mediated quinolone resistance is mediated by the genes (qnr) encoding proteins [17Strahilevitz J, Jacoby GA, Hooper DC, Robicsek A. Plasmid-mediated quinolone resistance: A multifaceted threat. Clin Microbiol Rev 2009; 22(4): 664-89.[http://dx.doi.org/10.1128/CMR.00016-09] [PMID: 19822894] ]. The major groups of qnr consist of qnrA, qnrB and qnrS [18Kim HB, Park CH, Kim CJ, Kim EC, Jacoby GA, Hooper DC. Prevalence of plasmid-mediated quinolone resistance determinants over a 9-year period. Antimicrob Agents Chemother 2009; 53(2): 639-45.[http://dx.doi.org/10.1128/AAC.01051-08] [PMID: 19064896] , 19Minarini LA, Poirel L, Cattoir V, Darini AL, Nordmann P. Plasmid-mediated quinolone resistance determinants among enterobacterial isolates from outpatients in Brazil. J Antimicrob Chemother 2008; 62(3): 474-8.[http://dx.doi.org/10.1093/jac/dkn237] [PMID: 18552340] ]. Plasmid-mediated resistance is growing clinical concern due to the transfer of resistance genes through the transfer of the horizontal gene to other species, conferring resistance against these antibiotics [20Davies J, Davies D. Origins and evolution of antibiotic resistance 2010.[http://dx.doi.org/10.1128/MMBR.00016-10] ]. In addition, the presence of Extended-spectrum Beta-lactamases (ESBLs), AmpC, and qnr genes in a plasmid is well documented, indicating the complexity of the determinant factors involved in plasmid resistance among enterobacterial isolates in medical environments [21Rawat D, Nair D. Extended-spectrum b-lactamases in Gram negative bacteria. J Glob Infect Dis 2010; 2(3): 263-74.[http://dx.doi.org/10.4103/0974-777X.68531] [PMID: 20927289] ]. Obviously, the broad emergence of the growing trend associated with the prevalence of plasmid resistance in enterobacterial isolates is undeniable, however, only a limited number of studies of Iran about the prevalence of qnr gene among clinical isolates E. coli has been reported. The purpose of this study was to determine the presence of qnr genes among E. coli isolated from UTIs of patients in Baqiyatallah hospital in Tehran province, Iran.

2. MATERIALS AND METHODS

Over a period of one year, 600 patients that suspected urinary tract infections were examined for E. coli strains. Individual isolates were analyzed by standard biochemical and serological tests as described previously [22Ranjbar R, Memariani M. Multilocus variable-number tandem-repeat analysis for genotyping of Shigella sonnei strains isolated from pediatric patients. Gastroenterol Hepatol Bed Bench 2015; 8(3): 225-32.[PMID: 26328045] ]. The slide agglutination test (Mast Diagnostics, Bootle, UK) was used for confirmation of the serogrouping of the isolates. Isolates were stored in trypticase soy broth (Merck KGaA, Darmstadt, Germany) containing 25% glycerol for future tests.

Antimicrobial susceptibility to nalidixic acid and ciprofloxacin was determined by using the disk diffusion method according to the Clinical Laboratory Standards Institute guidelines [2323 Clinical and Laboratory Standards Institute Performance standards for antimicrobial disk susceptibility tests; approved standard 2010; Document M2-A9 9th ed Wayne, PA: CLSI 2010.]. Antibiotic discs were placed within a distance of 12 mm from each other and incubated at 37ºC for 18 hrs. E. coli ATCC 25922 was used as quality-control strains to ensure the accuracy of the results obtained by susceptibility testing.

DNA was extracted using the AccuPrep® genomic DNA extraction kit (Bioneer, South Korea) according to the manufacturer’s instructions. The DNA concentration was determined by measuring absorbance of the samples at 260 nm using a spectrophotometer. The PCR and specific primers (Table 1) used for the detection of qnrA, qnrB and qnrS plasmid-mediated quinolone-resistance genes [24Lavilla S, González-López JJ, Sabaté M, et al. Prevalence of qnr genes among extended-spectrum beta-lactamase-producing enterobacterial isolates in Barcelona, Spain. J Antimicrob Chemother 2008; 61(2): 291-5.[http://dx.doi.org/10.1093/jac/dkm448] [PMID: 18029415] ]. PCR reaction was performed in a DNA thermocycler as follows: Initial denaturation at 96ºC for 5 min, 30 cycles of denaturation at 95ºC for 1 min, annealing at 55ºC for 1 min (based on the type of primer for each gene is different from that given in Table 1), elongation at 72ºC for 1 min and a final extension step of at 72ºC for 7 min, followed by a hold at 4ºC. PCR products were electrophoresed on 1.5% agarose gel containing ethidium bromide at 80 V for 1 h [25Khakabimamaghani S, Najafi A, Ranjbar R, Raam M. GelClust: A software tool for gel electrophoresis images analysis and dendrogram generation. Comput Methods Programs Biomed 2013; 111(2): 512-8.[http://dx.doi.org/10.1016/j.cmpb.2013.04.013] [PMID: 23727299] ].

Table 1
Primers used for detection of qnr genes in urinary Escherichia coli isolates.


3. RESULTS

Totally, 95 E. coli strains were isolated and enrolled in this study. Among the isolates, 60 and 49 strains were resistant to nalidixic acid and ciprofloxacin, respectively. PCR showed that 92 E. coli isolates carried qnrS. The qnrA and qnrB genes were not found among the clinical isolates of this study (Fig. 1).

Fig. (1)
PCR amplification of qnrS genes in nalidixic acid-resistant Escherichia coli isolates.


4. DISCUSSION

This study showed a high level of resistance against nalidixic acid among E. coli isolates recovered from the patients with UTI. Among the 95 isolates, 60 strains were resistant to nalidixic acid. Firoozeh et al. [26Firoozeh F, Zibaei M, Soleimani-Asl Y. Detection of plasmidmediated qnr genes among the quinolone-resistant Escherichia coli isolates in Iran. J Infect Dev Ctries 2014; 14(7): 818-22.] showed that 82.5% and 45% of urinary E. coli isolates were resistant to nalidixic acid and ciprofloxacin, respectively. The resistance of E. coli isolates from nosocomial infections was 76% and 52%, to nalidixic acid and ciprofloxacin, respectively in Khorvash et al. study [27Khorvash F, Mostafavizadeh K, Mobasherizadeh S, Behjati M. Susceptibility pattern of E. coli-associated urinary tract infection (UTI): A comparison of spinal cord injury-related and nosocomial UTI. Med Sci Monit 2009; 15(11): CR579-82.[PMID: 19865057] ]. In China, the prevalence of ciprofloxacin resistance among E. coli isolated from urine was 59.4% [28Shao HF, Wang WP, Zhang XW, Li ZD. Distribution and resistance trends of pathogens from urinary tract infections and impact on management. Zhonghua Nan Ke Xue 2003; 9(9): 690-692, 696.[PMID: 14727361] ]. Due to high rates of antibiotic resistance in this study and other studies, a full review of hospital management and further evaluation of monitoring systems are required. This study showed a high prevalence rate of plasmid-mediated quinolone resistance (qnrS). We did not find the qnrA and qnrB genes in our clinical isolates. The frequency of qnrS genes in our study was higher and the frequency of qnrA and qnrB genes in this study that was lower than those found in the two studies previously conducted in Iran. In another study, a low frequency (only a single E. coli isolate among 144 ciprofloxacin-resistant isolates) for qnr gene isolation was also described [29Pereira AS, Andrade SS, Monteiro J, Sader HS, Pignatari AC, Gales AC. Evaluation of the susceptibility profiles, genetic similarity and presence of qnr gene in Escherichia coli resistant to ciprofloxacin isolated in Brazilian hospitals. Braz J Infect Dis 2007; 11(1): 40-3.[http://dx.doi.org/10.1590/S1413-86702007000100011] [PMID: 17625725] ]. In Singapore [30Deepak RN, Koh TH, Chan KS. Plasmid-mediated quinolone resistance determinants in urinary isolates of Escherichia coli and Klebsiella pneumoniae in a large Singapore hospital. 2009] and Denmark [31Cavaco LM, Hansen DS, Friis-Møller A, Aarestrup FM, Hasman H, Frimodt-Møller N. First detection of plasmid-mediated quinolone resistance (qnrA and qnrS) in Escherichia coli strains isolated from humans in Scandinavia. J Antimicrob Chemother 2007; 59(4): 804-5.[http://dx.doi.org/10.1093/jac/dkl554] [PMID: 17284539] ], the nalidixic acid-resistant E. coli isolates as qnr positive was 1.8% and 1.6%, respectively. In Canada, only about 1% of E. coli and Klebsiella spp. isolates were resistant to ciprofloxacin and/or tobramycin as qnr positive [32Pitout JD, Hanson ND, Church DL, Laupland KB. Population-based laboratory surveillance for Escherichia coli producing extended-spectrum beta-lactamases: Importance of community isolates with blaCTX-M genes. Clin Infect Dis 2004; 15(38(12)): 1736-41.]. Currently, resistance against quinolones and qnr genes has increased in many parts of the world including Iran among Shigella [33Ranjbar R, Behnood V, Memariani H, Najafi A, Moghbeli M, Mammina C. Molecular characterisation of quinolone-resistant Shigella strains isolated in Tehran, Iran. J Glob Antimicrob Resist 2016; 5: 26-30.[http://dx.doi.org/10.1016/j.jgar.2016.01.010] [PMID: 27436462] ], Salmonella [34Malehmir S, Ranjbar R, Harzandi N. The molecular study of antibiotic resistance to quinolones in Salmonella enterica strains isolated in Tehran, Iran. Open Microbiol J 2017; 11: 189-94.[http://dx.doi.org/10.2174/1874285801711010189] [PMID: 29151995] ] and E. coli [35Ranjbar R, Farahani O. The prevalence of plasmid-mediated quinolone resistance genes in Escherichia coli isolated from hospital wastewater sources in Tehran, Iran. Iran J Public Health 2017; 46(9): 1285-91.[PMID: 29026795] , 36Abdi S, Ranjbar R, Vala MH, Jonaidi N, Bejestany OB, Bejestany FB. Frequency of bla TEM, bla SHV, bla CTX-M, and qnrA among Escherichia coli isolated from urinary tract infection. Arch Clin Infect Dis 2014; 9(1): e18690.[http://dx.doi.org/10.5812/archcid.18690] ] isolates. Uropathogenic E. coli is the most common cause of urinary tract infections, and quinolones resistant strains cause growing concern in developing countries [37Anvarinejad M, Farshad S, Alborzi A, Ranjbar R, Giammanco GM, Japoni A. Integron and genotype patterns of quinolones-resistant uropathogenic Escherichia coli. Afr J Microbiol Res 2011; 5(22): 3765-70.]. Also in a recent study, the low frequency of qnr genes observed among the clinical isolates of E. coli in Iran [40Rezazadeh M, Baghchesaraei H, Peymani A. Plasmid-Mediated Quinolone-Resistance (qnr) Genes in Clinical Isolates of Escherichia coli Collected from Several Hospitals of Qazvin and Zanjan Provinces, Iran. Osong Public Health Res Perspect 2016; 7(5): 307-12.[http://dx.doi.org/10.1016/j.phrp.2016.08.003] [PMID: 27812489] -42Yaghoubi S, Ranjbar R, Soltan Dallal MM, Shirazi MH, Sharifi-Yazdi MK. The frequency of mutations in quinolone resistance-determining regions and plasmid-mediated quinolone resistance in shigella isolates recovered from pediatric patients in Tehran, Iran: An Overlooked Problem. Microb Drug Resist 2017.[http://dx.doi.org/10.1089/mdr.2017.0155] [PMID: 29148915] ]. In this study, qnrS-positive isolates showed high-level resistance, however other mechanisms such as secondary changes in DNA gyrase or topoisomerase IV, and porin or efflux systems, which was not evaluated in our study that could be involved in resistance patterns.

CONCLUSION

In conclusion, our finding showed high frequencies of quinolone resistance genes among E. coli isolated from UTIs of patients in Baqiyatallah hospital in Tehran province, Iran. The circulation of strains of E. coli with a resistance plasmid gene can be considered as a risk for the spread of these types of genes among other bacteria, which requires special considerations. Also, the appropriate use of antibiotics may be useful to limit the potential spread of these resistant genes.

ETHICS APPROVAL AND CONSENT TO PARTICIPATE

Not applicable.

HUMAN AND ANIMAL RIGHTS

No animals/humans were used for studies that are the basis of this research.

CONSENT FOR PUBLICATION

Not applicable.

CONFLICT OF INTEREST

The author declares no conflict of interest, financial or otherwise.

ACKNOWLEDGMENTS

We would like to thank from the “Clinical Research Development Center of Baqiyatallah hospital” for their kind cooperation. This study was financially supported in part by “Clinical Research Development Center of Baqiyatallah hospital”

REFERENCES

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[17] Strahilevitz J, Jacoby GA, Hooper DC, Robicsek A. Plasmid-mediated quinolone resistance: A multifaceted threat. Clin Microbiol Rev 2009; 22(4): 664-89.[http://dx.doi.org/10.1128/CMR.00016-09] [PMID: 19822894]
[18] Kim HB, Park CH, Kim CJ, Kim EC, Jacoby GA, Hooper DC. Prevalence of plasmid-mediated quinolone resistance determinants over a 9-year period. Antimicrob Agents Chemother 2009; 53(2): 639-45.[http://dx.doi.org/10.1128/AAC.01051-08] [PMID: 19064896]
[19] Minarini LA, Poirel L, Cattoir V, Darini AL, Nordmann P. Plasmid-mediated quinolone resistance determinants among enterobacterial isolates from outpatients in Brazil. J Antimicrob Chemother 2008; 62(3): 474-8.[http://dx.doi.org/10.1093/jac/dkn237] [PMID: 18552340]
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[21] Rawat D, Nair D. Extended-spectrum b-lactamases in Gram negative bacteria. J Glob Infect Dis 2010; 2(3): 263-74.[http://dx.doi.org/10.4103/0974-777X.68531] [PMID: 20927289]
[22] Ranjbar R, Memariani M. Multilocus variable-number tandem-repeat analysis for genotyping of Shigella sonnei strains isolated from pediatric patients. Gastroenterol Hepatol Bed Bench 2015; 8(3): 225-32.[PMID: 26328045]
[23] 23 Clinical and Laboratory Standards Institute Performance standards for antimicrobial disk susceptibility tests; approved standard 2010; Document M2-A9 9th ed Wayne, PA: CLSI 2010.
[24] Lavilla S, González-López JJ, Sabaté M, et al. Prevalence of qnr genes among extended-spectrum beta-lactamase-producing enterobacterial isolates in Barcelona, Spain. J Antimicrob Chemother 2008; 61(2): 291-5.[http://dx.doi.org/10.1093/jac/dkm448] [PMID: 18029415]
[25] Khakabimamaghani S, Najafi A, Ranjbar R, Raam M. GelClust: A software tool for gel electrophoresis images analysis and dendrogram generation. Comput Methods Programs Biomed 2013; 111(2): 512-8.[http://dx.doi.org/10.1016/j.cmpb.2013.04.013] [PMID: 23727299]
[26] Firoozeh F, Zibaei M, Soleimani-Asl Y. Detection of plasmidmediated qnr genes among the quinolone-resistant Escherichia coli isolates in Iran. J Infect Dev Ctries 2014; 14(7): 818-22.
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Endorsements



"Open access will revolutionize 21st century knowledge work and accelerate the diffusion of ideas and evidence that support just in time learning and the evolution of thinking in a number of disciplines."


Daniel Pesut
(Indiana University School of Nursing, USA)

"It is important that students and researchers from all over the world can have easy access to relevant, high-standard and timely scientific information. This is exactly what Open Access Journals provide and this is the reason why I support this endeavor."


Jacques Descotes
(Centre Antipoison-Centre de Pharmacovigilance, France)

"Publishing research articles is the key for future scientific progress. Open Access publishing is therefore of utmost importance for wider dissemination of information, and will help serving the best interest of the scientific community."


Patrice Talaga
(UCB S.A., Belgium)

"Open access journals are a novel concept in the medical literature. They offer accessible information to a wide variety of individuals, including physicians, medical students, clinical investigators, and the general public. They are an outstanding source of medical and scientific information."


Jeffrey M. Weinberg
(St. Luke's-Roosevelt Hospital Center, USA)

"Open access journals are extremely useful for graduate students, investigators and all other interested persons to read important scientific articles and subscribe scientific journals. Indeed, the research articles span a wide range of area and of high quality. This is specially a must for researchers belonging to institutions with limited library facility and funding to subscribe scientific journals."


Debomoy K. Lahiri
(Indiana University School of Medicine, USA)

"Open access journals represent a major break-through in publishing. They provide easy access to the latest research on a wide variety of issues. Relevant and timely articles are made available in a fraction of the time taken by more conventional publishers. Articles are of uniformly high quality and written by the world's leading authorities."


Robert Looney
(Naval Postgraduate School, USA)

"Open access journals have transformed the way scientific data is published and disseminated: particularly, whilst ensuring a high quality standard and transparency in the editorial process, they have increased the access to the scientific literature by those researchers that have limited library support or that are working on small budgets."


Richard Reithinger
(Westat, USA)

"Not only do open access journals greatly improve the access to high quality information for scientists in the developing world, it also provides extra exposure for our papers."


J. Ferwerda
(University of Oxford, UK)

"Open Access 'Chemistry' Journals allow the dissemination of knowledge at your finger tips without paying for the scientific content."


Sean L. Kitson
(Almac Sciences, Northern Ireland)

"In principle, all scientific journals should have open access, as should be science itself. Open access journals are very helpful for students, researchers and the general public including people from institutions which do not have library or cannot afford to subscribe scientific journals. The articles are high standard and cover a wide area."


Hubert Wolterbeek
(Delft University of Technology, The Netherlands)

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(Sapienza - University of Rome, Italy)

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Philippe Hernigou
(Paris University, France)

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Peter Chiba
(University of Vienna, Austria)

"Open access journals are probably one of the most important contributions to promote and diffuse science worldwide."


Jaime Sampaio
(University of Trás-os-Montes e Alto Douro, Portugal)

"Open access journals make up a new and rather revolutionary way to scientific publication. This option opens several quite interesting possibilities to disseminate openly and freely new knowledge and even to facilitate interpersonal communication among scientists."


Eduardo A. Castro
(INIFTA, Argentina)

"Open access journals are freely available online throughout the world, for you to read, download, copy, distribute, and use. The articles published in the open access journals are high quality and cover a wide range of fields."


Kenji Hashimoto
(Chiba University, Japan)

"Open Access journals offer an innovative and efficient way of publication for academics and professionals in a wide range of disciplines. The papers published are of high quality after rigorous peer review and they are Indexed in: major international databases. I read Open Access journals to keep abreast of the recent development in my field of study."


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(Chinese University of Hong Kong, Hong Kong)

"It is a modern trend for publishers to establish open access journals. Researchers, faculty members, and students will be greatly benefited by the new journals of Bentham Science Publishers Ltd. in this category."


Jih Ru Hwu
(National Central University, Taiwan)


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