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Evaluation of Fluoroquinolone Resistance in Clinical Avian Pathogenic Escherichia coli Isolates from Flanders (Belgium). Antibiotics (Basel) 2020; 9:antibiotics9110800. [PMID: 33198103 PMCID: PMC7696922 DOI: 10.3390/antibiotics9110800] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 11/06/2020] [Accepted: 11/11/2020] [Indexed: 11/16/2022] Open
Abstract
Fluoroquinolones are frequently used antimicrobials for the treatment of avian pathogenic Escherichia coli (APEC) infections. However, rapid development and selection of resistance to this class of antimicrobial drugs is a significant problem. The aim of this study was to investigate the occurrence and mechanisms of antimicrobial resistance against enrofloxacin (ENRO) in APEC strains in Flanders, Belgium. One hundred and twenty-five APEC strains from broilers with clinical colibacillosis were collected in Flanders from November 2017 to June 2018. The minimum inhibitory concentration (MIC) of all strains and the mutant prevention concentration (MPC) of a sample of sensitive isolates were determined using a commercial gradient strip test and via the agar dilution method, respectively. Non-wild type (NWT) isolates were further characterized using polymerase chain reaction (PCR), gel electrophoresis and gene sequencing. Forty percent of the APEC strains were NWT according to the epidemiological cut-off (ECOFF) measure (MIC > 0.125 μg/mL). With respect to clinical breakpoints, 21% were clinically intermediate (0.5 ≤ MIC ≤ 1 μg/mL) and 10% were clinically resistant (MIC ≥ 2). The MPC values of the tested strains ranged from 0.064 to 1 μg/mL, resulting in MPC/MIC ratios varying from 4 to 32. The majority (92%) of the NWT strains carried one or two mutations in gyrA. Less than a quarter (22%) manifested amino acid substitutions in the topoisomerase IV parC subunit. Only three of the NWT strains carried a mutation in parE. Plasmid mediated quinolone resistance (PMQR) associated genes were detected in 18% of the NWT strains. In contrast to the relatively large number of NWT strains, only a small percentage of APEC isolates was considered clinically resistant. The most common MPC value for sensitive strains was 0.125 μg/mL. Some isolates showed higher values, producing wide mutant selection windows (MSW). Chromosomal mutations in DNA gyrase and topoisomerase IV were confirmed as the main source of decreased antimicrobial fluoroquinolone susceptibility, de-emphasizing the role of PMQR mechanisms.
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Solarte AL, Astorga RJ, de Aguiar FC, Tarradas C, Luque I, Gómez-Gascón L, Huerta B. Reduced Susceptibility of Salmonella Typhimurium Strains to Oregano Essential Oil and Enrofloxacin: An In Vitro Assay. Foodborne Pathog Dis 2019; 17:29-34. [PMID: 31710243 DOI: 10.1089/fpd.2019.2635] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Several European animal nutrition companies have incorporated essential oils (EOs) into animal feed as a result of the prohibition of antibiotics to promote animal growth. Previous studies of EOs have highlighted the absence of bacterial resistance for these substances, although most of the published works focus on studying their tolerance to subinhibitory doses. For this study, oregano essential oil (OEO) was chosen for its proven inhibitory and bactericidal activity. This study is an in vitro assay of the possible induction of Salmonella enterica serovar Typhimurium strains with reduced susceptibility to OEO by mutation, seeking to calculate the mutant prevention concentration (MPC) since this is an important measurement for the control Salmonella's resistance to fluoroquinolones such as enrofloxacin (ENR), the treatment of choice for this infection. To establish the MPC, we used a bacterial inoculum ≥109 colony-forming unit (CFU)/mL and examined the bases for points of resistance to ENR and mutations of target genes of the quinolone resistance determining region (QRDR). The three strains of Salmonella Typhimurium used in this study showed an MPC of four times the minimum inhibitory concentration (MIC) for ENR. In all cases, strains with reduced susceptibility to ENR were obtained, although none reached the point of resistance. The QRDR characterization region was in all cases of wild type (wt). Two of the strains tested with OEO grew at a concentration of 1 × MIC, which could be strains with reduced susceptibility, associated with mutation or not. In this case, the MPC was 2 × MIC. Once isolated and identified as Salmonella Typhimurium, the MIC against OEO of all strains obtained in the induction test indicated a possible reduction in susceptibility. However, the result obtained for both strains coincided with MIC of the original strains, rejecting a priori such a reduced susceptibility of Salmonella Typhimurium to OEO.
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Affiliation(s)
- Ana Lucía Solarte
- Animal Health Department, Veterinary Faculty, Rabanales Campus, University of Cordoba, Cordoba, Spain.,"International Excellence Agrifood Campus, CeiA3," University of Cordoba, Cordoba, Spain.,Office of the Vicerrector of Research, Universidad CESMAG, Pasto, Colombia
| | - Rafael Jesús Astorga
- Animal Health Department, Veterinary Faculty, Rabanales Campus, University of Cordoba, Cordoba, Spain.,"International Excellence Agrifood Campus, CeiA3," University of Cordoba, Cordoba, Spain
| | - Fabiana C de Aguiar
- Animal Health Department, Veterinary Faculty, Rabanales Campus, University of Cordoba, Cordoba, Spain.,"International Excellence Agrifood Campus, CeiA3," University of Cordoba, Cordoba, Spain
| | - Carmen Tarradas
- Animal Health Department, Veterinary Faculty, Rabanales Campus, University of Cordoba, Cordoba, Spain.,"International Excellence Agrifood Campus, CeiA3," University of Cordoba, Cordoba, Spain
| | - Inmaculada Luque
- Animal Health Department, Veterinary Faculty, Rabanales Campus, University of Cordoba, Cordoba, Spain.,"International Excellence Agrifood Campus, CeiA3," University of Cordoba, Cordoba, Spain
| | - Lidia Gómez-Gascón
- Animal Health Department, Veterinary Faculty, Rabanales Campus, University of Cordoba, Cordoba, Spain.,"International Excellence Agrifood Campus, CeiA3," University of Cordoba, Cordoba, Spain
| | - Belen Huerta
- Animal Health Department, Veterinary Faculty, Rabanales Campus, University of Cordoba, Cordoba, Spain.,"International Excellence Agrifood Campus, CeiA3," University of Cordoba, Cordoba, Spain
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Card RM, Stubberfield E, Rogers J, Nunez-Garcia J, Ellis RJ, AbuOun M, Strugnell B, Teale C, Williamson S, Anjum MF. Identification of a New Antimicrobial Resistance Gene Provides Fresh Insights Into Pleuromutilin Resistance in Brachyspira hyodysenteriae, Aetiological Agent of Swine Dysentery. Front Microbiol 2018; 9:1183. [PMID: 29971045 PMCID: PMC6018095 DOI: 10.3389/fmicb.2018.01183] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 05/15/2018] [Indexed: 11/30/2022] Open
Abstract
Brachyspira hyodysenteriae is the aetiological agent of swine dysentery, a globally distributed disease that causes profound economic loss, impedes the free trade and movement of animals, and has significant impact on pig health. Infection is generally treated with antibiotics of which pleuromutilins, such as tiamulin, are widely used for this purpose, but reports of resistance worldwide threaten continued effective control. In Brachyspira hyodysenteriae pleuromutilin resistance has been associated with mutations in chromosomal genes encoding ribosome-associated functions, however the dynamics of resistance acquisition are poorly understood, compromising stewardship efforts to preserve pleuromutilin effectiveness. In this study we undertook whole genome sequencing (WGS) and phenotypic susceptibility testing of 34 UK field isolates and 3 control strains to investigate pleuromutilin resistance in Brachyspira hyodysenteriae. Genome-wide association studies identified a new pleuromutilin resistance gene, tva(A) (tiamulin valnemulin antibiotic resistance), encoding a predicted ABC-F transporter. In vitro culture of isolates in the presence of inhibitory or sub-inhibitory concentrations of tiamulin showed that tva(A) confers reduced pleuromutilin susceptibility that does not lead to clinical resistance but facilitates the development of higher-level resistance via mutations in genes encoding ribosome-associated functions. Genome sequencing of antibiotic-exposed isolates identified both new and previously described mutations in chromosomal genes associated with reduced pleuromutilin susceptibility, including the 23S rRNA gene and rplC, which encodes the L3 ribosomal protein. Interesting three antibiotic-exposed isolates harboured mutations in fusA, encoding Elongation Factor G, a gene not previously associated with pleuromutilin resistance. A longitudinal molecular epidemiological examination of two episodes of swine dysentery at the same farm indicated that tva(A) contributed to development of tiamulin resistance in vivo in a manner consistent with that seen experimentally in vitro. The in vitro studies further showed that tva(A) broadened the mutant selection window and raised the mutant prevention concentration above reported in vivo antibiotic concentrations obtained when administered at certain doses. We show how the identification and characterisation of tva(A), a new marker for pleuromutilin resistance, provides evidence to inform treatment regimes and reduce the development of resistance to this class of highly important antimicrobial agents.
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Affiliation(s)
- Roderick M Card
- Department of Bacteriology, Animal and Plant Health Agency (APHA), Addlestone, United Kingdom
| | - Emma Stubberfield
- APHA Veterinary Investigation Centre Bury St. Edmunds, Bury St Edmunds, United Kingdom
| | - Jon Rogers
- APHA Veterinary Investigation Centre Bury St. Edmunds, Bury St Edmunds, United Kingdom
| | - Javier Nunez-Garcia
- Central Sequencing Unit, Animal and Plant Health Agency (APHA), Addlestone, United Kingdom
| | - Richard J Ellis
- Central Sequencing Unit, Animal and Plant Health Agency (APHA), Addlestone, United Kingdom
| | - Manal AbuOun
- Department of Bacteriology, Animal and Plant Health Agency (APHA), Addlestone, United Kingdom
| | - Ben Strugnell
- Farm Post Mortems Ltd., Bishop Auckland, United Kingdom
| | - Christopher Teale
- APHA Veterinary Investigation Centre Shrewsbury, Shrewsbury, United Kingdom
| | - Susanna Williamson
- APHA Veterinary Investigation Centre Bury St. Edmunds, Bury St Edmunds, United Kingdom
| | - Muna F Anjum
- Department of Bacteriology, Animal and Plant Health Agency (APHA), Addlestone, United Kingdom
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Randall L, Ridley A, Lemma F, Hale C, Davies R. In vitro investigations into the use of antimicrobials in combination to maintain efficacy of fluoroquinolones in poultry. Res Vet Sci 2016; 108:47-53. [PMID: 27663369 DOI: 10.1016/j.rvsc.2016.07.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 07/07/2016] [Accepted: 07/28/2016] [Indexed: 01/08/2023]
Abstract
The aim of this study was to determine if apramycin, colistin or lincomycin-spectinomycin, in combination with enrofloxacin, was able prevent the emergence of mutants with reduced susceptibility to fluoroquinolone antibiotics in vitro. MICs were determined for enrofloxacin alone and in combination for panels of Campylobacter (n=37), Escherichia coli (n=52) and Salmonella (n=52) isolates. MIC results suggested that apramycin, colistin and lincomycin-spectinomycin worked in an additive/indifferent way when each was combined with enrofloxacin. Apramycin was considered the most promising antibiotic for combination-therapy in conjunction with enrofloxacin, and further evaluations (MBCs, MPCs and time-kill-curves) were performed for this combination for selected isolates. Results suggest combination-therapy of enrofloxacin with apramycin increases the efficacy, as well as decreasing the emergence and survival of bacteria with mutational resistance to fluoroquinolone antibiotics. Such combination-therapy, minimising the development of mutational resistance, may have relevance for Campylobacter, E. coli and Salmonella infections in poultry.
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Affiliation(s)
- Luke Randall
- Animal and Plant Health Agency (Weybridge), Woodham Lane, New Haw, Addlestone, Surrey, KT15 3NB, UK.
| | - Anne Ridley
- Animal and Plant Health Agency (Weybridge), Woodham Lane, New Haw, Addlestone, Surrey, KT15 3NB, UK
| | - Fabrizio Lemma
- Animal and Plant Health Agency (Weybridge), Woodham Lane, New Haw, Addlestone, Surrey, KT15 3NB, UK
| | - Carol Hale
- Animal and Plant Health Agency (Weybridge), Woodham Lane, New Haw, Addlestone, Surrey, KT15 3NB, UK
| | - Rob Davies
- Animal and Plant Health Agency (Weybridge), Woodham Lane, New Haw, Addlestone, Surrey, KT15 3NB, UK
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Thompson CN, Thieu NTV, Vinh PV, Duc AN, Wolbers M, Vinh H, Campbell JI, Ngoc DTT, Hoang NVM, Thanh TH, The HC, Nguyen TNT, Lan NPH, Parry CM, Chau NVV, Thwaites G, Thanh DP, Baker S. Clinical implications of reduced susceptibility to fluoroquinolones in paediatric Shigella sonnei and Shigella flexneri infections. J Antimicrob Chemother 2015; 71:807-15. [PMID: 26679253 PMCID: PMC4743702 DOI: 10.1093/jac/dkv400] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 10/26/2015] [Indexed: 11/25/2022] Open
Abstract
Objectives We aimed to quantify the impact of fluoroquinolone resistance on the clinical outcome of paediatric shigellosis patients treated with fluoroquinolones in southern Vietnam. Such information is important to inform therapeutic management for infections caused by this increasingly drug-resistant pathogen, responsible for high morbidity and mortality in young children globally. Methods Clinical information and bacterial isolates were derived from a randomized controlled trial comparing gatifloxacin with ciprofloxacin for the treatment of paediatric shigellosis. Time–kill experiments were performed to evaluate the impact of MIC on the in vitro growth of Shigella and Cox regression modelling was used to compare clinical outcome between treatments and Shigella species. Results Shigella flexneri patients treated with gatifloxacin had significantly worse outcomes than those treated with ciprofloxacin. However, the MICs of fluoroquinolones were not significantly associated with poorer outcome. The presence of S83L and A87T mutations in the gyrA gene significantly increased MICs of fluoroquinolones. Finally, elevated MICs and the presence of the qnrS gene allowed Shigella to replicate efficiently in vitro in high concentrations of ciprofloxacin. Conclusions We found that below the CLSI breakpoint, there was no association between MIC and clinical outcome in paediatric shigellosis infections. However, S. flexneri patients had worse clinical outcomes when treated with gatifloxacin in this study regardless of MIC. Additionally, Shigella harbouring the qnrS gene are able to replicate efficiently in high concentrations of ciprofloxacin and we hypothesize that such strains possess a competitive advantage against fluoroquinolone-susceptible strains due to enhanced shedding and transmission.
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Affiliation(s)
- Corinne N Thompson
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam Centre for Tropical Medicine, Oxford University, Oxford, UK The London School of Hygiene and Tropical Medicine, London, UK
| | - Nga Tran Vu Thieu
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Phat Voong Vinh
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Anh Nguyen Duc
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Marcel Wolbers
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam Centre for Tropical Medicine, Oxford University, Oxford, UK
| | - Ha Vinh
- The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - James I Campbell
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam Centre for Tropical Medicine, Oxford University, Oxford, UK
| | - Dung Tran Thi Ngoc
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Nguyen Van Minh Hoang
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Tuyen Ha Thanh
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Hao Chung The
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - To Nguyen Thi Nguyen
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Nguyen Phu Huong Lan
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Christopher M Parry
- The London School of Hygiene and Tropical Medicine, London, UK School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan
| | | | - Guy Thwaites
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam Centre for Tropical Medicine, Oxford University, Oxford, UK
| | - Duy Pham Thanh
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Stephen Baker
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam Centre for Tropical Medicine, Oxford University, Oxford, UK The London School of Hygiene and Tropical Medicine, London, UK
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Determination of the minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) of selected antimicrobials in bovine and swine Pasteurella multocida, Escherichia coli, and Staphylococcus aureus isolates. ACTA VET BRNO 2015. [DOI: 10.2754/avb201584020083] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We compared the values of the minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) values of three antimicrobial agents for 72 bovine isolates ofPasteurella multocida, 80 swine isolates ofP. multocida, 80 bovine isolates ofEscherichia coli, 80 swine isolates ofE. coli, and 80 isolates ofStaphylococcus aureusfrom bovine mastitis. The ratio of MIC90/MPC90which limited mutant selection window (MSW) was ≤ 0.12/4 mg/l for enrofloxacin, 0.5/≥ 64 mg/l for florfenicol and 4/≥ 128 mg/l for tulathromycin in bovineP. multocidaisolates, ≤ 0.12/2 mg/l for enrofloxacin, 0.5/≥ 64 mg/l for florfenicol and 4/≥ 128 mg/l for tulathromycin in swineP. multocidaisolates, 1/16 mg/l for enrofloxacin, 8/≥ 64 mg/l for florfenicol and 8/≥ 128 mg/l for tulathromycin in bovineE. coliisolates, 0.5/16 mg/l for enrofloxacin, ≥ 64/≥ 64 mg/l for florfenicol and 8/≥ 128 mg/l for tulathromycin in swineE. coliisolates, and 0.25/16 mg/l for enrofloxacin, 4/≥ 64 mg/l for florfenicol and 4/≥ 128 mg/l for tulathromycin inS. aureusisolates. These findings indicate that the dosage of antimicrobial agents to achieve serum concentration equal to or higher than MPC could reduce selection of resistant bacterial subpopulation.
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Analysis of triclosan-selected Salmonella enterica mutants of eight serovars revealed increased aminoglycoside susceptibility and reduced growth rates. PLoS One 2013; 8:e78310. [PMID: 24205194 PMCID: PMC3799642 DOI: 10.1371/journal.pone.0078310] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 09/19/2013] [Indexed: 11/19/2022] Open
Abstract
The biocide triclosan (TRC) is used in a wide range of household, personal care, veterinary, industrial and medical products to control microbial growth. This extended use raises concerns about a possible association between the application of triclosan and the development of antibiotic resistance. In the present study we determined triclosan mutant prevention concentrations (MPC) for Salmonella enterica isolates of eight serovars and investigated selected mutants for their mechanisms mediating decreased susceptibility to triclosan. MPCTRC values were 8 - 64-fold higher than MIC values and ranged between 1 - 16 µg/ml. The frequencies at which mutants were selected varied between 1.3 x 10-10 - 9.9 x 10-11. Even if MIC values of mutants decreased by 3-7 dilution steps in the presence of the efflux pump inhibitor Phe-Arg-β-naphtylamide, only minor changes were observed in the expression of genes encoding efflux components or regulators, indicating that neither the major multidrug efflux pump AcrAB-TolC nor AcrEF are up-regulated in triclosan-selected mutants. Nucleotide sequence comparisons confirmed the absence of alterations in the regulatory regions acrRA, soxRS, marORAB, acrSE and ramRA of selected mutants. Single bp and deduced Gly93→Val amino acid exchanges were present in fabI, the target gene of triclosan, starting from a concentration of 1 µg/ml TRC used for MPC determinations. The fabI genes were up to 12.4-fold up-regulated. Complementation experiments confirmed the contribution of Gly93→Val exchanges and fabI overexpression to decreased triclosan susceptibility. MIC values of mutants compared to parent strains were even equal or resulted in a more susceptible phenotype (1-2 dilution steps) for the aminoglycoside antibiotics kanamycin and gentamicin as well as for the biocide chlorhexidine. Growth rates of selected mutants were significantly lower and hence, might partly explain the rare occurrence of Salmonella field isolates exhibiting decreased susceptibility to triclosan.
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Sun Y, Dai M, Hao H, Wang Y, Huang L, Almofti YA, Liu Z, Yuan Z. The role of RamA on the development of ciprofloxacin resistance in Salmonella enterica serovar Typhimurium. PLoS One 2011; 6:e23471. [PMID: 21858134 PMCID: PMC3155569 DOI: 10.1371/journal.pone.0023471] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2011] [Accepted: 07/18/2011] [Indexed: 01/13/2023] Open
Abstract
Active efflux pump is a primary fluoroquinolone resistant mechanism of clinical isolates of Salmonella enterica serovar Typhimurium. RamA is an essential element in producing multidrug resistant (MDR) S.enterica serovar Typhimurium. The aim of the present study was to elucidate the roles of RamA on the development of ciprofloxacin, the first choice for the treatment of salmonellosis, resistance in S. enterica serovar Typhimurium. Spontaneous mutants were selected via several passages of S. enterica serovar Typhimurium CVCC541 susceptible strain (ST) on M-H agar with increasing concentrations of ciprofloxacin (CIP). Accumulation of ciprofloxacin was tested by the modified fluorometric method. The expression levels of MDR efflux pumps were determined by real time RT-PCR. In ST and its spontaneous mutants, the ramA gene was inactivated by insertion of the kan gene and compensated on a recombinant plasmid pGEXΦ(gst-ramA). The mutant prevention concentration (MPC) and mutant frequencies of ciprofloxacin against ST and a spontaneous mutant in the presence, absence and overexpression of RamA were tested. Four spontaneous mutants (SI1-SI4) were obtained. The SI1 (CIP MICs, 0.1 mg/L) without any target site mutation in its quinolone resistant determining regions (QRDRs) and SI3 (CIP MICs, 16 mg/L) harboring the Ser83→Phe mutation in its QRDR of GyrA strains exhibited reduced susceptibility and resistance to multidrugs, respectively. In SI1, RamA was the main factor that controlled the susceptibility to ciprofloxacin by activating MdtK as well as increasing the expression level of acrAB. In SI3, RamA played predominant role in ciprofloxacin resistance via increasing the expression level of acrAB. Likewise, the deficiency of RamA decreased the MPCs and mutant frequencies of ST and SI2 to ciprofloxacin. In conclusion, the expression of RamA promoted the development of ciprofloxacin resistant mutants of S. enterica serovar Typhimurium. The inhibition of RamA could decrease the appearance of the ciprofloxacin resistant mutants.
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Affiliation(s)
- Yawei Sun
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residues (HZAU), Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China
| | - Menghong Dai
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residues (HZAU), Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China
| | - Haihong Hao
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residues (HZAU), Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China
| | - Yulian Wang
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residues (HZAU), Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China
| | - Lingli Huang
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residues (HZAU), Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China
| | - Yassir A. Almofti
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residues (HZAU), Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China
| | - Zhenli Liu
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residues (HZAU), Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China
| | - Zonghui Yuan
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residues (HZAU), Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China
- * E-mail:
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Mutant prevention concentration-based pharmacokinetic/pharmacodynamic indices as dosing targets for suppressing the enrichment of levofloxacin-resistant subpopulations of Staphylococcus aureus. Antimicrob Agents Chemother 2011; 55:2409-12. [PMID: 21343454 DOI: 10.1128/aac.00975-10] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
MIC- and mutant prevention concentration (MPC)-based pharmacokinetic/pharmacodynamic (PK/PD) indices were compared for suitability as attainment targets for restricting amplification of levofloxacin-resistant mutant subpopulations. When three Staphylococcus aureus strains were examined with a hollow-fiber PK/PD model, area under the concentration-time curve over 24 h (AUC24)/MPC values of >25 and maximum concentration of drug in serum (Cmax)/MPC values of >2.2 predicted resistance outcome among different isolates with an interisolate kappa coefficient of 1. MIC-based mutant-restrictive PK/PD values varied >8-fold and exhibited only a moderate interisolate agreement (kappa coefficient of 0.5). Thus, MPC-based PK/PD indices are more suitable than MIC-based indices for predicting mutant-restricting fluoroquinolone doses when multiple bacterial isolates are considered.
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Shaheen BW, Boothe DM, Oyarzabal OA, Wang C, Johnson CM. Evaluation of the contribution ofgyrAmutation and efflux pumps to fluoroquinolone and multidrug resistance in pathogenicEscherichia coliisolates from dogs and cats. Am J Vet Res 2011; 72:25-32. [DOI: 10.2460/ajvr.72.1.25] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Ferrari R, Magnani M, Souza RB, Tognim MCB, Oliveira TCRM. Mutant prevention concentration (MPC) of ciprofloxacin against Salmonella enterica of epidemic and poultry origin. Curr Microbiol 2010; 62:628-32. [PMID: 20872005 DOI: 10.1007/s00284-010-9754-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Accepted: 09/03/2010] [Indexed: 11/25/2022]
Abstract
Salmonella isolates resistant or with reduced susceptibility to quinolones increased in recent years. The mutant prevention concentration (MPC) is a new alternative that can prevent the selection and multiplication of resistant Salmonella spp. strains. The MPC of ciprofloxacin (CipMPC) was evaluated for 312 Salmonella enterica strains of epidemic and poultry origin susceptible and resistant to nalidixic acid (NAL). The CipMPC for NAL-susceptible strains were in the range from 0.002 to 4 μg/ml and for NAL-resistant strains, it ranged from 0.004 to 16 μg/ml. The average MPC/MIC ratio for NAL-resistant strains was higher than NAL susceptible. S. Enteritidis showed the highest CipMPC and the highest MPC/MIC ratio also for NAL-resistant strains and with mutations in gyrA. Serovar Corvallis, a NAL-resistant strain without mutations, and of poultry origin showed the highest CipMPC value. The lowest value was observed for epidemic NAL-susceptible strains serovars Typhimurium and London. The average MPC/MIC ratio for strains with mutations in Aspartate 87 was higher than that mutated in Serine 83. The results show the importance of MPC in determining the correct dosage of Cip for treatment of Salmonella spp.
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Affiliation(s)
- Rafaela Ferrari
- Ciência e Tecnologia de Alimentos, Universidade Estadual de Londrina, Londrina, Brazil
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12
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Mutant prevention concentrations of fluoroquinolones against Campylobacter jejuni isolated from chicken. Vet Microbiol 2010; 144:409-14. [DOI: 10.1016/j.vetmic.2010.02.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 01/30/2010] [Accepted: 02/10/2010] [Indexed: 11/20/2022]
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13
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Blondeau JM. New concepts in antimicrobial susceptibility testing: the mutant prevention concentration and mutant selection window approach. Vet Dermatol 2010; 20:383-96. [PMID: 20178475 DOI: 10.1111/j.1365-3164.2009.00856.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Current measurements of antimicrobial susceptibility or resistance utilize a standardized bacterial inoculum (10(5) cfu/mL) exposed to varying drug concentrations in a test tube. Following incubation under ideal conditions, the lowest drug concentration inhibiting growth is the minimum inhibitory concentration (MIC). When the MIC exceeds the amount of drug that can be safely achieved in the body, we call these microorganisms resistant; established breakpoints for various 'bug-drug' combinations are used to categorize microorganisms as susceptible, intermediate or resistant. MIC testing has been used for decades to guide antimicrobial therapy and remains an important measurement for infectious diseases. More recently, the mutant prevention concentration (MPC) has been described as a novel measurement of in vitro susceptibility or resistance and is based on the testing of larger bacterial inocula, i.e. > or =10(9) cfu/mL - such as those associated with some infections in humans and animals. MPC defines the lowest drug concentration required to block the growth of the least susceptible cell present in high density bacterial populations. MPC testing applies to microorganisms considered susceptible to the drug by MIC testing. The mutant selection window (MSW) defines the 'danger zone' for therapeutic drug concentrations. Minimizing the length of time the drug concentration remains in the MSW may reduce the likelihood for resistance selection during therapy. The MSW is bordered by the MIC and MPC values and the drug concentration range between the measured MIC and MPC values defines the MSW. MPC values, when considered with drug pharmacology, may allow prediction on the probability of resistance selection when bacteria are exposed to antimicrobial agents during therapy for infectious diseases. In today's environment, resistance prevention should be a goal of antimicrobial therapy.
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Affiliation(s)
- Joseph M Blondeau
- Department of Clinical Microbiology, Royal University Hospital, Canada S7N 0W8.
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14
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Abstract
Large-scale, systems biology approaches now allow us to systematically map synergistic and antagonistic interactions between drugs. Consequently, drug antagonism is emerging as a powerful tool to study biological function and relatedness between cellular components as well as to uncover mechanisms of drug action. Furthermore, theoretical models and new experiments suggest that antagonistic interactions between antibiotics can counteract the evolution of drug resistance.
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15
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Drug interactions modulate the potential for evolution of resistance. Proc Natl Acad Sci U S A 2008; 105:14918-23. [PMID: 18815368 DOI: 10.1073/pnas.0800944105] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Antimicrobial treatments increasingly rely on multidrug combinations, in part because of the emergence and spread of antibiotic resistance. The continued effectiveness of combination treatments depends crucially on the frequency with which multidrug resistance arises. Yet, it is unknown how this propensity for resistance depends on cross-resistance and on epistatic interactions-ranging from synergy to antagonism-between the drugs. Here, we analyzed how interactions between pairs of drugs affect the spontaneous emergence of resistance in the medically important pathogen Staphylococcus aureus. Resistance is selected for within a window of drug concentrations high enough to inhibit wild-type growth but low enough for some resistant mutants to grow. Introducing an experimental method for high-throughput colony imaging, we counted resistant colonies arising across a two-dimensional matrix of drug concentrations for each of three drug pairs. Our data show that these different drug combinations have significantly different impacts on the size of the window of drug concentrations where resistance is selected for. We framed these results in a mathematical model in which the frequencies of resistance to single drugs, cross-resistance, and epistasis combine to determine the propensity for multidrug resistance. The theory suggests that drug pairs which interact synergistically, preferred for their immediate efficacy, may in fact favor the future evolution of resistance. This framework reveals the central role of drug epistasis in the evolution of resistance and points to new strategies for combating the emergence of drug-resistant bacteria.
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16
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Kehrenberg C, de Jong A, Friederichs S, Cloeckaert A, Schwarz S. Molecular mechanisms of decreased susceptibility to fluoroquinolones in avian Salmonella serovars and their mutants selected during the determination of mutant prevention concentrations. J Antimicrob Chemother 2007; 59:886-92. [PMID: 17369276 DOI: 10.1093/jac/dkm072] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES Salmonella enterica isolates of six serovars and mutants obtained during determination of mutant prevention concentrations (MPCs) were investigated for mechanisms of decreased susceptibility to fluoroquinolones. METHODS The quinolone resistance determining regions (QRDRs) of gyrA, gyrB, parC and parE genes were sequenced. MIC values were determined in the presence/absence of the efflux pump inhibitors carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) or Phe-Arg-beta-naphthylamide (PA beta N). PCR assays for the quinolone resistance genes qnrA, qnrB, qnrS or aac(6')-Ib-cr were applied. The MPC values of ciprofloxacin (MPC(CIP)) were determined for all isolates and selected mutants were investigated for their quinolone resistance mechanisms. RESULTS In contrast to 11 nalidixic acid-susceptible isolates, 24 nalidixic acid-resistant isolates exhibited single mutations in gyrA (Asp-87 --> Tyr, Gly, Asn or Ser-83 --> Phe, Tyr) or parC (Thr-57 --> Ser). While CCCP had no influence on the MICs, PA beta N decreased the MIC(CIP) values by 1-3 dilution steps and MIC(NAL) values by up to 6 dilution steps. Of the resistance genes investigated, only qnrS was present, in a single Salmonella Infantis isolate. The MPC(CIP) values were 4-64-fold higher than the MICs and ranged between 1-16 and 0.12-1 mg/L, respectively, for isolates resistant or susceptible to nalidixic acid. Only mutants obtained from formerly nalidixic acid-susceptible isolates developed single mutations in gyrA or gyrB. CONCLUSIONS In field isolates and mutants, target site mutations and efflux seem to be important mechanisms for decreased fluoroquinolone susceptibility. Mutants derived during MPC determination from field isolates already harbouring single-step mutations in gyrA did not exhibit further mutations in any target genes.
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Affiliation(s)
- Corinna Kehrenberg
- Institut für Tierzucht, Bundesforschungsanstalt für Landwirtschaft (FAL), Höltystr. 10, 31535 Neustadt-Mariensee, Germany.
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17
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Pasquali F, Manfreda G. Mutant prevention concentration of ciprofloxacin and enrofloxacin against Escherichia coli, Salmonella Typhimurium and Pseudomonas aeruginosa. Vet Microbiol 2007; 119:304-10. [PMID: 16987619 DOI: 10.1016/j.vetmic.2006.08.018] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Revised: 07/28/2006] [Accepted: 08/09/2006] [Indexed: 11/24/2022]
Abstract
The mutant prevention concentration (MPC) is a new concept meant to face the increased prevalence of antibiotic resistance by using antibiotic concentrations able to prevent the selection of single-step resistant mutants. In the present study, the MPCs of ciprofloxacin and enrofloxacin were evaluated against fully susceptible strains of Escherichia coli, Salmonella Typhimurium and Pseudomonas aeruginosa. Additionally, representative single-step mutants arising after exposure to sub-MPC antibiotic concentrations were investigated for molecular basis of their fluoroquinolone resistance phenotypes. MPC value was recorded when more than 10(10) CFU/mL were spread on Muëller Hinton Agar supplemented with different antibiotic concentrations (from 1X to 16X MIC value). MICs of original strains as well as single-step mutants were determined in presence or absence of the Efflux Pump Inhibitor Phe-Arg-beta-naphthylamide (PAbetaN). Moreover point mutations in the QRDR of the gyrA and parC genes were investigated by sequencing. The enrofloxacin MPC values were 4-16-fold higher than ciprofloxacin values. E. coli and S. Typhimurium representative single-step mutants showed reduced susceptibilities associated with point mutations in the QRDR of the gyrA gene or efflux pump system. P. aeruginosa mutants showed resistance phenotypes associated predominantly with efflux pump system activity. According to in vitro MPC data, ciprofloxacin showed a better efficacy than enrofloxacin, in preventing the selection of E. coli, S. Typhimurium and P. aeruginosa single-step mutants. However, in relation to AUC/MPC ratio, the MPC concept can be applied in vivo to ciprofloxacin and enrofloxacin for E. coli and S. Typhimurium but not for P. aeruginosa.
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Affiliation(s)
- Frédérique Pasquali
- Department of Food Science, Alma Mater Studiorum, University of Bologna, Fanin 44, 40127 Bologna, Italy.
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18
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Randall LP, Cooles SW, Coldham NC, Stapleton KS, Piddock LJV, Woodward MJ. Modification of enrofloxacin treatment regimens for poultry experimentally infected with Salmonella enterica serovar Typhimurium DT104 to minimize selection of resistance. Antimicrob Agents Chemother 2006; 50:4030-7. [PMID: 17030564 PMCID: PMC1694010 DOI: 10.1128/aac.00525-06] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2006] [Revised: 07/02/2006] [Accepted: 09/19/2006] [Indexed: 11/20/2022] Open
Abstract
We hypothesized that higher doses of fluoroquinolones for a shorter duration could maintain efficacy (as measured by reduction in bacterial count) while reducing selection in chickens of bacteria with reduced susceptibility. Chicks were infected with Salmonella enterica serovar Typhimurium DT104 and treated 1 week later with enrofloxacin at the recommended dose for 5 days (water dose adjusted to give 10 mg/kg of body weight of birds or equivalence, i.e., water at 50 ppm) or at 2.5 or 5 times the recommended dose for 2 days or 1 day, respectively. The dose was delivered continuously (ppm) or pulsed in the water (mg/kg) or by gavage (mg/kg). In vitro in sera, increasing concentrations of 0.5 to 8 microg/ml enrofloxacin correlated with increased activity. In vivo, the efficacy of the 1-day treatment was significantly less than that of the 2- and 5-day treatments. The 2-day treatments showed efficacy similar to that of the 5-day treatment in all but one repeat treatment group and significantly (P < 0.01) reduced the Salmonella counts. Dosing at 2.5x the recommended dose and pulsed dosing both increased the peak antibiotic concentrations in cecal contents, liver, lung, and sera as determined by high-pressure liquid chromatography. There was limited evidence that shorter treatment regimens (in particular the 1-day regimen) selected for fewer strains with reduced susceptibility. In conclusion, the 2-day treatment would overall require a shorter withholding time than the 5-day treatment and, in view of the increased peak antibiotic concentrations, may give rise to improved efficacy, in particular for treating respiratory and systemic infections. However, it would be necessary to validate the 2-day regimen in a field situation and in particular against respiratory and systemic infections to validate or refute this hypothesis.
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Affiliation(s)
- Luke P Randall
- Department of Food and Environmental Safety, Veterinary Laboratories Agency, New Haw, Surrey, KT15 3NB, United Kingdom.
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Chavanet P, Croisier D. La fenêtre de mutation pour le couple « pneumocoque–fluoroquinolone ». Apport des modèles expérimentaux. Med Mal Infect 2006; 36:614-24. [PMID: 17095175 DOI: 10.1016/j.medmal.2006.07.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Accepted: 07/21/2006] [Indexed: 10/23/2022]
Abstract
Low-level resistance to fluoroquinolones (in vitro susceptible but with topoisomerase mutation, parC) is currently rare among pneumococci in France. However, this resistance is more frequently observed in previously exposed patients and therapeutic failure has been reported. These issues were investigated by using a humanized model of experimental pneumonia induced by pneumococci exhibiting this low-level resistance profile. The results are as follows: 1) when the pneumonia is due to a wild type pneumococcus, humanized ciprofloxacin treatment is not effective because of resistant mutants with parC mutation; moreover, levoflaxin treatment is less bactericidal than gatiflo- or moxifloxacin (-4 vs -6 log CFU/g); 2) when an efflux strain is used, levo-treatment is not efficient but there are no mutants, a gatiflo-treatment is combined when mutants appear and moxiflo-treatment is effective; 3) when the pneumonia is induced with susceptible parC strains, treatment with either levo, or gati, or moxifloxacin is completely ineffective because resistant mutants appear (acquisition of another gyrA mutation). Measure of the mutation prevention concentration (MPC) allows anticipating these results since the mutation window can be determined. These results stress the necessity to identify patients with such pneumococcal strains in order to avoid therapeutic failure and the emergence of fluoroquinolone resistant mutants.
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Affiliation(s)
- P Chavanet
- Laboratoire des maladies infectieuses, LQRF-EA 562, service des maladies infectieuses, hôpital du Bocage, CHU de Dijon, faculté de médecine de Dijon, BP 77908, 21000 Dijon, France.
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20
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Giraud E, Baucheron S, Cloeckaert A. Resistance to fluoroquinolones in Salmonella: emerging mechanisms and resistance prevention strategies. Microbes Infect 2006; 8:1937-44. [PMID: 16714137 DOI: 10.1016/j.micinf.2005.12.025] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Accepted: 12/28/2005] [Indexed: 11/18/2022]
Abstract
We review the current state of knowledge about the genetic and biochemical mechanisms that mediate quinolone resistance in Salmonella. They include modifications of topoisomerase targets, increased efflux activity and the recently described topoisomerase protection by the plasmid-encoded Qnr protein. We discuss what factors may determine the order of implementation of these various mechanisms in a particular strain, and what strategies could be used to combat resistance, from the inhibition of mutagenesis mechanisms to counteracting, during fluoroquinolone treatment, of resistance mechanisms already set in the infecting strain.
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Affiliation(s)
- Etienne Giraud
- UMR INRA-ENVN Chimiothérapie Aquacole et Environnement, La Chantrerie, BP 40706, 44307 Nantes Cedex 03, France.
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Drlica K, Zhao X, Blondeau JM, Hesje C. Low correlation between MIC and mutant prevention concentration. Antimicrob Agents Chemother 2006; 50:403-4. [PMID: 16377725 PMCID: PMC1346827 DOI: 10.1128/aac.50.1.403-404.2006] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Hansen GT, Zhao X, Drlica K, Blondeau JM. Mutant prevention concentration for ciprofloxacin and levofloxacin with Pseudomonas aeruginosa. Int J Antimicrob Agents 2006; 27:120-4. [PMID: 16426820 DOI: 10.1016/j.ijantimicag.2005.10.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2005] [Accepted: 10/06/2005] [Indexed: 11/20/2022]
Abstract
The mutant prevention concentration (MPC) was determined by population analysis using six fluoroquinolone-susceptible isolates of Pseudomonas aeruginosa applied to fluoroquinolone-containing agar plates. The MPCs were 3 mg/L and 9.5 mg/L for ciprofloxacin and levofloxacin, respectively. At high concentrations of either compound, single-step gyrA resistance mutants were recovered. Using a modified method for estimating the MPC, 151 clinical isolates were surveyed. Modal MPCs were 2 mg/L and 8 mg/L, respectively, for ciprofloxacin and levofloxacin. Thus, ciprofloxacin is three to four times more active than levofloxacin against resistant mutant subpopulations. For individual isolates, the MPC correlated poorly with the minimum inhibitory concentration (r(2) = 0.41 and 0.39 for ciprofloxacin and levofloxacin, respectively).
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Affiliation(s)
- Glen T Hansen
- Department of Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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23
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Wetzstein HG. Comparative mutant prevention concentrations of pradofloxacin and other veterinary fluoroquinolones indicate differing potentials in preventing selection of resistance. Antimicrob Agents Chemother 2005; 49:4166-73. [PMID: 16189094 PMCID: PMC1251556 DOI: 10.1128/aac.49.10.4166-4173.2005] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2005] [Revised: 07/01/2005] [Accepted: 07/15/2005] [Indexed: 11/20/2022] Open
Abstract
Pradofloxacin (PRA) is an 8-cyano-fluoroquinolone (FQ) being developed to treat bacterial infections in dogs and cats. Its mutant prevention concentrations (MPC) were determined for Escherichia coli ATCC 8739 at 0.225 microg/ml, and for Staphylococcus aureus ATCC 6538 at 0.55 microg/ml. At drug concentrations equal to or above the MPC, growth (implying selective clonal expansion) of first-step FQ-resistant variants, naturally present in large bacterial populations, was inhibited. MPC(90) derived from 10 clinical isolates each of E. coli and Staphylococcus intermedius, the latter species being of greater clinical relevance than S. aureus in companion-animal medicine, amounted to 0.2 to 0.225 and 0.30 to 0.35 microg/ml, respectively. MPCs of other veterinary FQs were assessed to determine relative in vitro potencies. The MPCs of marbofloxacin, enrofloxacin, danofloxacin, sarafloxacin, orbifloxacin, and difloxacin were 1.2-, 1.4-, 2.3-, 2.4-, 5-, and 7-fold higher than the MPC of PRA for E. coli ATCC 8739, and 6-, 6-, 19-, 15-, 15-, and 31-fold higher than the MPC of PRA for S. aureus ATCC 6538, respectively. MPC curves revealed a pronounced heterogeneity in susceptibility within populations of > or =4 x 10(9) CFU employed, extending to 10-fold above the MICs. The duration of incubation and, for S. aureus, inoculum density profoundly affected the MPCs. With appropriate dosing, PRA may combine high therapeutic efficacy with a high potential for restricting the selection for FQ resistance under field conditions in the species analyzed.
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Affiliation(s)
- H-G Wetzstein
- Bayer HealthCare AG, Animal Health Division, Leverkusen, Germany.
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24
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Abstract
Quinolones are one of the largest classes of antimicrobial agents used worldwide. This review considers the quinolones that are available currently and used widely in Europe (norfoxacin, ciprofloxacin, ofloxacin, levofloxacin and moxifloxacin) within their historical perspective, while trying to position them in the context of recent and possible future advances based on an understanding of: (1) their chemical structures and how these impact on activity and toxicity; (2) resistance mechanisms (mutations in target genes, efflux pumps); (3) their pharmacodynamic properties (AUC/MIC and Cmax/MIC ratios; mutant prevention concentration and mutant selection window); and (4) epidemiological considerations (risk of emergence of resistance, clonal spread). Their main indications are examined in relation to their advantages and drawbacks. Overall, it is concluded that these important agents should be used in an educated fashion, based on a careful balance between their ease of use and efficacy vs. the risk of emerging resistance and toxicity. However, there is now substantial evidence to support use of the most potent drug at the appropriate dose whenever this is required.
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Affiliation(s)
- F Van Bambeke
- Unit of Cellular and Molecular Pharmacology, Catholic University of Louvain, Brussels.
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Murray A, Coia JE, Mather H, Brown DJ. Ciprofloxacin resistance in non-typhoidal Salmonella serotypes in Scotland, 1993–2003. J Antimicrob Chemother 2005; 56:110-4. [PMID: 15914492 DOI: 10.1093/jac/dki164] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES To determine the levels of resistance to ciprofloxacin among non-typhoidal salmonellae in Scotland. METHODS Etest strips were used to determine the ciprofloxacin MICs for nalidixic acid-resistant salmonellae isolated from humans during 1993-2003. RESULTS The percentage of nalidixic acid-resistant salmonellae isolated from human infection in Scotland has increased from 1.4% in 1993, to 8.8% in 1998 and 21.3% in 2003. Of 493 strains of nalidixic acid-resistant Salmonella tested, a single isolate of Salmonella Typhimurium RDNC was resistant to ciprofloxacin at the NCCLS breakpoint of 4 mg/L. Eleven isolates were resistant at the Scottish Salmonella Reference Laboratory breakpoint of 0.5 mg/L, while 466 isolates (94.5%) had reduced susceptibility with MICs of > or =0.125 mg/L and <0.5 mg/L. CONCLUSIONS These results show that very few non-typhoidal isolates of Salmonella in Scotland that are resistant to nalidixic acid are also resistant to ciprofloxacin at the NCCLS recommended breakpoint of 4 mg/L. The majority of isolates examined, however, do show reduced susceptibility at 0.125 mg/L. This confirms the necessity for continuing antimicrobial surveillance of resistance to this important antibiotic.
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Affiliation(s)
- A Murray
- Scottish Salmonella Reference Laboratory, Stobhill Hospital, Glasgow, UK
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