51
|
Phylogenetic analysis of chromosomally determined qnr and related proteins. Antimicrob Agents Chemother 2013; 57:1930-4. [PMID: 23318805 DOI: 10.1128/aac.02080-12] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
qnr genes were discovered on plasmids by their ability to reduce quinolone susceptibility, but homologs can be found in the genomes of at least 92 Gram-negative, Gram-positive, and strictly anaerobic bacterial species. The related pentapeptide repeat protein-encoding mfpA gene is present in the genome of at least 19 species of Mycobacterium and 10 other Actinobacteria species. The native function of these genes is not yet known.
Collapse
|
52
|
Mechanisms accounting for fluoroquinolone multidrug resistance Escherichia coli isolated from companion animals. Vet Microbiol 2012; 161:159-68. [DOI: 10.1016/j.vetmic.2012.07.019] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 07/08/2012] [Accepted: 07/12/2012] [Indexed: 11/22/2022]
|
53
|
Dalhoff A. Global fluoroquinolone resistance epidemiology and implictions for clinical use. Interdiscip Perspect Infect Dis 2012; 2012:976273. [PMID: 23097666 PMCID: PMC3477668 DOI: 10.1155/2012/976273] [Citation(s) in RCA: 212] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2012] [Accepted: 06/26/2012] [Indexed: 12/22/2022] Open
Abstract
This paper on the fluoroquinolone resistance epidemiology stratifies the data according to the different prescription patterns by either primary or tertiary caregivers and by indication. Global surveillance studies demonstrate that fluoroquinolone resistance rates increased in the past years in almost all bacterial species except S. pneumoniae and H. influenzae, causing community-acquired respiratory tract infections. However, 10 to 30% of these isolates harbored first-step mutations conferring low level fluoroquinolone resistance. Fluoroquinolone resistance increased in Enterobacteriaceae causing community acquired or healthcare associated urinary tract infections and intraabdominal infections, exceeding 50% in some parts of the world, particularly in Asia. One to two-thirds of Enterobacteriaceae producing extended spectrum β-lactamases were fluoroquinolone resistant too. Furthermore, fluoroquinolones select for methicillin resistance in Staphylococci. Neisseria gonorrhoeae acquired fluoroquinolone resistance rapidly; actual resistance rates are highly variable and can be as high as almost 100%, particularly in Asia, whereas resistance rates in Europe and North America range from <10% in rural areas to >30% in established sexual networks. In general, the continued increase in fluoroquinolone resistance affects patient management and necessitates changes in some guidelines, for example, treatment of urinary tract, intra-abdominal, skin and skin structure infections, and traveller's diarrhea, or even precludes the use in indications like sexually transmitted diseases and enteric fever.
Collapse
Affiliation(s)
- Axel Dalhoff
- Institute for Infection-Medicine, Christian-Albrechts Univerity of Kiel and University Medical Center Schleswig-Holstein, Brunswiker Straße 4, 24105 Kiel, Germany
| |
Collapse
|
54
|
Briales A, Rodriguez-Martinez JM, Velasco C, Machuca J, Diaz de Alba P, Blazquez J, Pascual A. Exposure to diverse antimicrobials induces the expression of qnrB1, qnrD and smaqnr genes by SOS-dependent regulation. J Antimicrob Chemother 2012; 67:2854-9. [DOI: 10.1093/jac/dks326] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
55
|
Poole K. Bacterial stress responses as determinants of antimicrobial resistance. J Antimicrob Chemother 2012; 67:2069-89. [PMID: 22618862 DOI: 10.1093/jac/dks196] [Citation(s) in RCA: 305] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Bacteria encounter a myriad of stresses in their natural environments, including, for pathogens, their hosts. These stresses elicit a variety of specific and highly regulated adaptive responses that not only protect bacteria from the offending stress, but also manifest changes in the cell that impact innate antimicrobial susceptibility. Thus exposure to nutrient starvation/limitation (nutrient stress), reactive oxygen and nitrogen species (oxidative/nitrosative stress), membrane damage (envelope stress), elevated temperature (heat stress) and ribosome disruption (ribosomal stress) all impact bacterial susceptibility to a variety of antimicrobials through their initiation of stress responses that positively impact recruitment of resistance determinants or promote physiological changes that compromise antimicrobial activity. As de facto determinants of antimicrobial, even multidrug, resistance, stress responses may be worthy of consideration as therapeutic targets.
Collapse
Affiliation(s)
- Keith Poole
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada K7L 3N6.
| |
Collapse
|
56
|
|
57
|
Lupo A, Coyne S, Berendonk TU. Origin and evolution of antibiotic resistance: the common mechanisms of emergence and spread in water bodies. Front Microbiol 2012; 3:18. [PMID: 22303296 PMCID: PMC3266646 DOI: 10.3389/fmicb.2012.00018] [Citation(s) in RCA: 221] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 01/10/2012] [Indexed: 11/25/2022] Open
Abstract
The environment, and especially freshwater, constitutes a reactor where the evolution and the rise of new resistances occur. In water bodies such as waste water effluents, lakes, and rivers or streams, bacteria from different sources, e.g., urban, industrial, and agricultural waste, probably selected by intensive antibiotic usage, are collected and mixed with environmental species. This may cause two effects on the development of antibiotic resistances: first, the contamination of water by antibiotics or other pollutants lead to the rise of resistances due to selection processes, for instance, of strains over-expressing broad range defensive mechanisms, such as efflux pumps. Second, since environmental species are provided with intrinsic antibiotic resistance mechanisms, the mixture with allochthonous species is likely to cause genetic exchange. In this context, the role of phages and integrons for the spread of resistance mechanisms appears significant. Allochthonous species could acquire new resistances from environmental donors and introduce the newly acquired resistance mechanisms into the clinics. This is illustrated by clinically relevant resistance mechanisms, such as the fluoroquinolones resistance genes qnr. Freshwater appears to play an important role in the emergence and in the spread of antibiotic resistances, highlighting the necessity for strategies of water quality improvement. We assume that further knowledge is needed to better understand the role of the environment as reservoir of antibiotic resistances and to elucidate the link between environmental pollution by anthropogenic pressures and emergence of antibiotic resistances. Only an integrated vision of these two aspects can provide elements to assess the risk of spread of antibiotic resistances via water bodies and suggest, in this context, solutions for this urgent health issue.
Collapse
Affiliation(s)
- Agnese Lupo
- Institute of Hydrobiology, Department of Hydrosciences, Technical University Dresden Dresden, Germany
| | | | | |
Collapse
|
58
|
Jacoby GA, Griffin CM, Hooper DC. Citrobacter spp. as a source of qnrB Alleles. Antimicrob Agents Chemother 2011; 55:4979-84. [PMID: 21844311 PMCID: PMC3195048 DOI: 10.1128/aac.05187-11] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 08/09/2011] [Indexed: 11/20/2022] Open
Abstract
qnrB is the most common of the five qnr families and has the greatest number of allelic variants. Almost two-thirds of the qnrB alleles have been reported in Citrobacter spp., and several were shown to be located on the chromosome. In this study, PCR was used to investigate the prevalence of plasmid-mediated quinolone resistance genes in 71 clinical isolates belonging to the Citrobacter freundii complex. Thirty-seven percent contained qnrB alleles, including 7 (qnrB32 to qnrB38) that were novel and 1 pseudogene, while none contained qnrA, qnrC, qnrD, qnrS, or aac(6')-Ib-cr. When the strains were arrayed by related 16S rRNA sequence and further separated into subspecies by biochemical criteria, clustering of qnrB-positive strains was evident. In only two strains with qnrB2 and qnrB4 was quinolone resistance transferable by conjugation, and only these strains contained the ISCR1 sequence that is often associated with qnrB on plasmids. Five of 26 qnrB-positive strains contained integrase genes, but these included the strains with qnrB2 and qnrB4 as well as two strains with other transmissible plasmids. In a fully sequenced genome of Citrobacter youngae, a member of the C. freundii complex, another novel qnrB allele, qnrB39, occurs in a sequence of genes that is 90% identical to sequence surrounding integron-associated qnrB4 incorporated into plasmids. The chromosome of Citrobacter is the likely source of plasmid-mediated qnrB.
Collapse
|
59
|
Quinolone induction of qnrVS1 in Vibrio splendidus and plasmid-carried qnrS1 in Escherichia coli, a mechanism independent of the SOS system. Antimicrob Agents Chemother 2011; 55:5942-5. [PMID: 21930884 DOI: 10.1128/aac.05142-11] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Plasmid-carried qnrS1 is derived from Vibrio splendidus chromosomal qnrVS1. qnrVS1 transcripts increased 21- to 34-fold with subinhibitory concentrations of ciprofloxacin but much less with mitomycin. No LexA binding sites were upstream of qnrS1 or qnrVS1, and similar induction levels were observed in lexA-positive and lexA-negative Escherichia coli strains with native qnrS1 plasmid pMG306 but not with pUC18-cloned qnrS1 or qnrVS1. Thus, qnrS1 induction by quinolones is independent of the SOS system and requires sequence besides that of the structural gene.
Collapse
|
60
|
Wang D, Wang H, Qi Y, Liang Y, Zhang J, Yu L. Novel variants of the qnrB gene, qnrB31 and qnrB32, in Klebsiella pneumoniae. J Med Microbiol 2011; 60:1849-1852. [PMID: 21816942 DOI: 10.1099/jmm.0.034272-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Quinolone resistance in the family Enterobacteriaceae is mostly attributed to the accumulation of mutations in the bacterial enzymes targeted by fluoroquinolones: DNA gyrase and DNA topoisomerase IV. Here we isolated the Klebsiella pneumoniae strains KP3606 and KP4707 from different specimens from 2008 to 2010 in Taizhou Municipal Hospital of China, and discovered a new subtype qnrB31, for which the GenBank accession number is HQ418999, and another new subtype qnrB32, for which the GenBank accession number is HQ704413. Susceptibility testing showed that KP3606 had a reduced susceptibility (MIC ≥0.5 µg ml(-1)) to quinolones, while KP4707 was resistant to quinolones. Of all qnrB alleles, the novel variants the qnrB32 gene and qnrB31 gene have the highest amino acid identity. The results suggested that of all the various genes involved in resistance to quinolones, the qnrB gene is the most likely to be mutated, and plasmids might play a role in the dissemination and evolution of qnrB genes.
Collapse
Affiliation(s)
- Dongguo Wang
- Department of Clinical Laboratory Medicine, Medical College of Taizhou University Affiliated Taizhou Municipal Hospital, Taizhou, ZheJiang Province, PR China
| | - Haibao Wang
- Department of Clinical Laboratory Medicine, Medical College of Taizhou University Affiliated Taizhou Municipal Hospital, Taizhou, ZheJiang Province, PR China
| | - Yongxiao Qi
- Department of Laboratory Medicine, Medical College of Taizhou University, Taizhou, ZheJiang Province, PR China
| | - Yong Liang
- Department of Laboratory Medicine, Medical College of Taizhou University, Taizhou, ZheJiang Province, PR China
| | - Jing Zhang
- Department of Clinical Laboratory Medicine, Medical College of Taizhou University Affiliated Taizhou Municipal Hospital, Taizhou, ZheJiang Province, PR China
| | - Lianhua Yu
- Department of Clinical Laboratory Medicine, Medical College of Taizhou University Affiliated Taizhou Municipal Hospital, Taizhou, ZheJiang Province, PR China
| |
Collapse
|
61
|
Vetting MW, Hegde SS, Wang M, Jacoby GA, Hooper DC, Blanchard JS. Structure of QnrB1, a plasmid-mediated fluoroquinolone resistance factor. J Biol Chem 2011; 286:25265-73. [PMID: 21597116 PMCID: PMC3137097 DOI: 10.1074/jbc.m111.226936] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 05/19/2011] [Indexed: 11/06/2022] Open
Abstract
QnrB1 is a plasmid-encoded pentapeptide repeat protein (PRP) that confers a moderate degree of resistance to fluoroquinolones. Its gene was cloned into an expression vector with an N-terminal polyhistidine tag, and the protein was purified by nickel affinity chromatography. The structure of QnrB1 was determined by a combination of trypsinolysis, surface mutagenesis, and single anomalous dispersion phasing. QnrB1 folds as a right-handed quadrilateral β-helix with a highly asymmetric dimeric structure typical of PRP-topoisomerase poison resistance factors. The threading of pentapeptides into the β-helical fold is interrupted by two noncanonical PRP sequences that produce outward projecting loops that interrupt the regularity of the PRP surface. Deletion of the larger upper loop eliminated the protective effect of QnrB1 on DNA gyrase toward inhibition by quinolones, whereas deletion of the smaller lower loop drastically reduced the protective effect. These loops are conserved among all plasmid-based Qnr variants (QnrA, QnrC, QnrD, and QnrS) and some chromosomally encoded Qnr varieties. A mechanism in which PRP-topoisomerase poison resistance factors bind to and disrupt the quinolone-DNA-gyrase interaction is proposed.
Collapse
Affiliation(s)
- Matthew W. Vetting
- From the Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Subray S. Hegde
- From the Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Minghua Wang
- the Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts 02114, and
| | | | - David C. Hooper
- the Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts 02114, and
| | - John S. Blanchard
- From the Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461
| |
Collapse
|
62
|
Coates ARM, Halls G, Hu Y. Novel classes of antibiotics or more of the same? Br J Pharmacol 2011; 163:184-94. [PMID: 21323894 PMCID: PMC3085877 DOI: 10.1111/j.1476-5381.2011.01250.x] [Citation(s) in RCA: 358] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Revised: 01/13/2011] [Accepted: 01/14/2011] [Indexed: 01/06/2023] Open
Abstract
The world is running out of antibiotics. Between 1940 and 1962, more than 20 new classes of antibiotics were marketed. Since then, only two new classes have reached the market. Analogue development kept pace with the emergence of resistant bacteria until 10-20 years ago. Now, not enough analogues are reaching the market to stem the tide of antibiotic resistance, particularly among gram-negative bacteria. This review examines the existing systemic antibiotic pipeline in the public domain, and reveals that 27 compounds are in clinical development, of which two are new classes, both of which are in Phase I clinical trials. In view of the high attrition rate of drugs in early clinical development, particularly new classes and the current regulatory hurdles, it does not seem likely that new classes will be marketed soon. This paper suggests that, if the world is to return to a situation in which there are enough antibiotics to cope with the inevitable ongoing emergence of bacterial resistance, we need to recreate the prolific antibiotic discovery period between 1940 and 1962, which produced 20 classes that served the world well for 60 years. If another 20 classes and their analogues, particularly targeting gram-negatives could be produced soon, they might last us for the next 60 years. How can this be achieved? Only a huge effort by governments in the form of finance, legislation and providing industry with real incentives will reverse this. Industry needs to re-enter the market on a much larger scale, and academia should rebuild its antibiotic discovery infrastructure to support this effort. The alternative is Medicine without effective antibiotics.
Collapse
Affiliation(s)
- Anthony R M Coates
- Medical Microbiology, Centre for Infection, Department of Clinical Sciences, St George's, University of London, UK.
| | | | | |
Collapse
|
63
|
Dissemination of multiple drug resistance genes by class 1 integrons in Klebsiella pneumoniae isolates from four countries: a comparative study. Antimicrob Agents Chemother 2011; 55:3140-9. [PMID: 21518841 DOI: 10.1128/aac.01529-10] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A comparative genetic analysis of 42 clinical Klebsiella pneumoniae isolates, resistant to two or more antibiotics belonging to the broad-spectrum β-lactam group, sourced from Sydney, Australia, and three South American countries is presented. The study focuses on the genetic contexts of class 1 integrons, mobilizable genetic elements best known for their role in the rapid evolution of antibiotic resistance among Gram-negative pathogens. It was found that the class 1 integrons in this cohort were located in a number of different genetic contexts with clear regional differences. In Sydney, IS26-associated Tn21-like transposons on IncL/M plasmids contribute greatly to the dispersal of integron-associated multiple-drug-resistant (MDR) loci. In contrast, in the South American countries, Tn1696-like transposons on an IncA/C plasmid(s) appeared to be disseminating a characteristic MDR region. A range of mobile genetic elements is clearly being recruited by clinically important mobile class 1 integrons, and these elements appear to be becoming more common with time. This in turn is driving the evolution of complex and laterally mobile MDR units and may further complicate antibiotic therapy.
Collapse
|
64
|
Liu IF, Sutherland JH, Cheng B, Tse-Dinh YC. Topoisomerase I function during Escherichia coli response to antibiotics and stress enhances cell killing from stabilization of its cleavage complex. J Antimicrob Chemother 2011; 66:1518-24. [PMID: 21486853 DOI: 10.1093/jac/dkr150] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES To explore the role of topoisomerase I in gene activation and increased RecA levels during the bacterial SOS response, as well as the effect of antibiotic treatment and stress challenge on cell killing initiated by trapped topoisomerase I cleavage complex. METHODS A mutant Escherichia coli strain with a ΔtopA mutation was used to investigate the role of topoisomerase I function in the SOS response to trimethoprim and mitomycin C. Induction of the recA and dinD1 promoters was measured using luciferase reporters of these promoters fused to luxCDABE. An increase in the RecA level following trimethoprim treatment was quantified directly by western blotting. The effect of stress challenge from trimethoprim and acidified nitrite treatments on cell killing by topoisomerase I cleavage complex accumulation was measured by the decrease in viability following induction of recombinant mutant topoisomerase I that forms a stabilized cleavage complex. RESULTS Topoisomerase I function was found to be required for efficient transcriptional activation of the recA and dinD1 promoters during the E. coli SOS response to trimethoprim and mitomycin C. The role of topoisomerase I in the SOS response was confirmed with quantitative western blot analysis of RecA following trimethoprim treatment. The bactericidal effect from topoisomerase I cleavage complex accumulation was shown to be enhanced by stress challenge from trimethoprim and acidified nitrite. CONCLUSIONS Bacterial topoisomerase I function is actively involved in the SOS response to antibiotics and stress challenge. Cell killing initiated by the topoisomerase I cleavage complex would be enhanced by antibiotics and the host response. These findings provide further support for bacterial topoisomerase I as a therapeutic target.
Collapse
Affiliation(s)
- I-Fen Liu
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA
| | | | | | | |
Collapse
|
65
|
Abstract
Antibiotics have always been considered one of the wonder discoveries of the 20th century. This is true, but the real wonder is the rise of antibiotic resistance in hospitals, communities, and the environment concomitant with their use. The extraordinary genetic capacities of microbes have benefitted from man's overuse of antibiotics to exploit every source of resistance genes and every means of horizontal gene transmission to develop multiple mechanisms of resistance for each and every antibiotic introduced into practice clinically, agriculturally, or otherwise. This review presents the salient aspects of antibiotic resistance development over the past half-century, with the oft-restated conclusion that it is time to act. To achieve complete restitution of therapeutic applications of antibiotics, there is a need for more information on the role of environmental microbiomes in the rise of antibiotic resistance. In particular, creative approaches to the discovery of novel antibiotics and their expedited and controlled introduction to therapy are obligatory.
Collapse
|
66
|
Abstract
Antibiotics have always been considered one of the wonder discoveries of the 20th century. This is true, but the real wonder is the rise of antibiotic resistance in hospitals, communities, and the environment concomitant with their use. The extraordinary genetic capacities of microbes have benefitted from man's overuse of antibiotics to exploit every source of resistance genes and every means of horizontal gene transmission to develop multiple mechanisms of resistance for each and every antibiotic introduced into practice clinically, agriculturally, or otherwise. This review presents the salient aspects of antibiotic resistance development over the past half-century, with the oft-restated conclusion that it is time to act. To achieve complete restitution of therapeutic applications of antibiotics, there is a need for more information on the role of environmental microbiomes in the rise of antibiotic resistance. In particular, creative approaches to the discovery of novel antibiotics and their expedited and controlled introduction to therapy are obligatory.
Collapse
Affiliation(s)
- Julian Davies
- Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada.
| | | |
Collapse
|
67
|
Guérin E, Cambray G, Da Re S, Mazel D, Ploy MC. [The SOS response controls antibiotic resistance by regulating the integrase of integrons]. Med Sci (Paris) 2010; 26:28-30. [PMID: 20132769 DOI: 10.1051/medsci/201026128] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
68
|
Velasco C, Rodríguez-Martínez JM, Briales A, Díaz de Alba P, Calvo J, Pascual A. Smaqnr, a new chromosome-encoded quinolone resistance determinant in Serratia marcescens. J Antimicrob Chemother 2009; 65:239-42. [PMID: 19942618 DOI: 10.1093/jac/dkp424] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES A new pentapeptide repeat (PRP) protein, named SmaQnr, from the clinically relevant species Serratia marcescens, which decreased susceptibility to quinolones when expressed in Escherichia coli, is reported herein. METHODS In silico analysis revealed the presence of a gene encoding a Qnr-like protein that shares 80% amino acid identity with QnrB1 in the S. marcescens strain Db11. Fragments carrying the coding region and the upstream non-coding sequences of eight clinical isolates were cloned and expressed in E. coli. MIC values of quinolones were determined. RT-PCR was used to study expression of these genes in their natural host. Southern hybridization was used to explore the presence of the gene in the genus Serratia. RESULTS Recombinant plasmids encoding SmaQnr reduced susceptibility to fluoroquinolones and nalidixic acid in both E. coli ATCC 25922 and DH10B. Sequences upstream of these genes contain a LexA box. Conventional RT-PCR showed transcription of the analysed Smaqnr genes in their natural hosts. Southern blot analysis suggests the presence of similar genes in several species of the genus Serratia. CONCLUSIONS SmaQnr conferred a reduced susceptibility phenotype against fluoroquinolones in E. coli. These data provide evidence of its possible role in quinolone resistance in S. marcescens. This Gram-negative species may constitute a reservoir for qnr-like quinolone resistance genes.
Collapse
Affiliation(s)
- C Velasco
- Department of Microbiology, University of Seville, Seville, Spain.
| | | | | | | | | | | |
Collapse
|