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Chao CM, Lai CC, Yu WL. Epidemiology of extended-spectrum β-lactamases in Enterobacterales in Taiwan for over two decades. Front Microbiol 2023; 13:1060050. [PMID: 36762100 PMCID: PMC9905819 DOI: 10.3389/fmicb.2022.1060050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Accepted: 12/22/2022] [Indexed: 01/28/2023] Open
Abstract
The emergence of antimicrobial resistance among microorganisms is a serious public health concern, and extended-spectrum β-lactamases (ESBL)-producing Enterobacterales is one of the major concerns among antibiotic-resistant bacteria. Although the prevalence of ESBL in Enterobacterales has been increasing with time, the prevalence of ESBL could differ according to the species, hospital allocation, sources of infections, nosocomial or community acquisitions, and geographic regions. Therefore, we conducted a comprehensive review of the epidemiology of ESBL-producing Enterobacterales in Taiwan. Overall, the rates of ESBL producers are higher in northern regions than in other parts of Taiwan. In addition, the genotypes of ESBL vary according to different Enterobacterales. SHV-type ESBLs (SHV-5 and SHV-12) were the major types of Enterobacter cloacae complex, but Serratia marcescens, Proteus mirabilis, Escherichia coli, and Klebsiella pneumoniae were more likely to possess CTX-M-type ESBLs (CTX-M-3 and CTX-M-14). Moreover, a clonal sequence type of O25b-ST131 has been emerging among urinary or bloodstream E. coli isolates in the community in Taiwan, and this clone was potentially associated with virulence, ESBL (CTX-M-15) production, ciprofloxacin resistance, and mortality. Finally, the evolution of the genetic traits of the ESBL-producing Enterobacterales isolates helps us confirm the interhospital and intrahospital clonal dissemination in several regions of Taiwan. In conclusion, continuous surveillance in the investigation of ESBL production among Enterobacterales is needed to establish its long-term epidemiology.
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Affiliation(s)
- Chien-Ming Chao
- Department of Intensive Care Medicine, Chi Mei Medical Center, Liouying, Taiwan,Department of Dental Laboratory Technology, Min-Hwei College of Health Care Management, Tainan, Taiwan
| | - Chih-Cheng Lai
- Division of Hospital Medicine, Department of Internal Medicine, Chi Mei Medical Center, Tainan, Taiwan
| | - Wen-Liang Yu
- Department of Intensive Care Medicine, Chi Mei Medical Center, Tainan, Taiwan,Department of Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan,*Correspondence: Wen-Liang Yu,
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Ku YH, Lee MF, Chuang YC, Yu WL. Detection of Plasmid-Mediated β-Lactamase Genes and Emergence of a Novel AmpC (CMH-1) in Enterobacter cloacae at a Medical Center in Southern Taiwan. J Clin Med 2018; 8:jcm8010008. [PMID: 30577544 PMCID: PMC6352282 DOI: 10.3390/jcm8010008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 12/17/2018] [Accepted: 12/18/2018] [Indexed: 12/03/2022] Open
Abstract
The plasmid-mediated extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases in Enterobacter spp. have increasingly been reported. In this study, we investigated the prevalence of the plasmid-mediated β-lactamases in Enterobacter cloacae from bloodstream isolates at a medical center in southern Taiwan. ESBL and ampC genes were detected by PCRs and DNA sequencing. Conjugation experiments were conducted to confirm the transferability of the genetic resistance trait. Among 41 non-repetitive blood isolates of cefuroxime-resistant E. cloacae, eight isolates exhibited ESBL phenotype confirmed by double-disk synergistic tests. Nearly all the strains were susceptible to carbapenems. The prevalence rate of the plasmid-mediated blaampC genes was 73% (30/41), including one blaDHA-1, one blaMIR-6, two novel blaCMH-1 genes and other blaACT-like genes. Coexistence of plasmid-mediated blaACT and ESBL genes (10 with blaSHV-12 and one with blaCTX-M-3) was observed. Successful transmissions of the blaACT and blaCMH-1 were demonstrated in some transconjugants. The inducible or derepressed CMH-1 had expanded activity of isolates versus ceftazidime. Enterobacterial repetitive intergenic consensus (ERIC)-PCR analysis and pulsotype showed distinct patterns suggesting non-clonal relationship. In conclusion, plasmid-mediated blaACT-likeampC genes in E. cloacae isolates have been highly prevalent in southern Taiwan and may continue genetic evolution, contributing to the complexities in antibiotic-resistant mechanisms.
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Affiliation(s)
- Yee-Huang Ku
- Division of Infectious Disease, Department of Internal Medicine, Chi Mei Medical Center-Liouying, Tainan 710, Taiwan.
| | - Mei-Feng Lee
- Laboratory of Environmental Health, Research Center of Humanities and Technology, National University of Kaohsiung, Kaohsiung 811, Taiwan.
| | - Yin-Ching Chuang
- Department of Medical Research, Chi Mei Medical Center, Tainan 710, Taiwan.
| | - Wen-Liang Yu
- Department of Intensive Care Medicine, Chi Mei Medical Center, Tainan 710, Taiwan.
- Department of Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan.
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Elsherbiny NM, Ali IM, Hassanein KM, Ahmed MT. Extended-spectrum β-lactamase (ESBL)-producing Serratia marcescens causing healthcare-associated infections in Assiut University Hospitals, Egypt. J Glob Antimicrob Resist 2018; 13:96-97. [PMID: 29621627 DOI: 10.1016/j.jgar.2018.03.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 03/16/2018] [Accepted: 03/24/2018] [Indexed: 10/17/2022] Open
Affiliation(s)
- Nahla M Elsherbiny
- Department of Medical Microbiology and Immunology, Faculty of Medicine, Assiut University, P.O. 71515, Assiut, Egypt.
| | - Ibrahim M Ali
- Department of Microbiology and Immunology, Faculty of Pharmacy, Al-Azhar University, Assiut Branch, Egypt
| | - Khalid M Hassanein
- Department of Medical Microbiology and Immunology, Faculty of Medicine, Assiut University, P.O. 71515, Assiut, Egypt
| | - Mohamed T Ahmed
- Department of Microbiology and Immunology, Faculty of Pharmacy, Al-Azhar University, Assiut Branch, Egypt
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Ku YH, Chen CC, Lee MF, Chuang YC, Tang HJ, Yu WL. Comparison of synergism between colistin, fosfomycin and tigecycline against extended-spectrum β-lactamase-producing Klebsiella pneumoniae isolates or with carbapenem resistance. JOURNAL OF MICROBIOLOGY, IMMUNOLOGY, AND INFECTION = WEI MIAN YU GAN RAN ZA ZHI 2017; 50:931-939. [PMID: 28716360 DOI: 10.1016/j.jmii.2016.12.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 11/16/2016] [Accepted: 12/07/2016] [Indexed: 12/24/2022]
Abstract
PURPOSE To investigate the synergistic and bactericidal effects of antimicrobial combinations of any two of colistin, fosfomycin and tigecycline against the nine extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae (KP) clinical isolates, including 4 carbapenem-susceptible strains and five imipenem and/or meropenem-resistant strains. METHODS In vitro synergism and bactericidal activity of combination of colistin, fosfomycin and tigecycline were evaluated by time-kill studies in standard inoculum of bacterial densities of a suspension containing 5 × 105 CFU/mL by using 1/2× MIC for each alone, and both 1/2× and 1/4× MIC for any two drugs. The settings of low MIC dosing were allowed to rapidly survey the most active drug combination. RESULTS The most active combination group was colistin plus tigecycline, showing synergy in 8 isolates and bactericidal activities in 6 isolates by using concentrations of 1/2× MIC and 1/4× MIC, respectively. The least active combination was tigecycline plus fosfomycin, which showed synergy in only 4 isolates and no bactericidal activities by using concentrations of 1/2× MIC and 1/4× MIC, respectively. CONCLUSIONS The combination of tigecycline and colistin may be considered as a last-resort approach to the ESBL-producing KP infections, especially those isolates with carbapenem resistance.
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Affiliation(s)
- Yee-Huang Ku
- Division of Infectious Disease, Department of Internal Medicine, Chi Mei Medical Center, Liouying, Tainan City, Taiwan
| | - Chi-Chung Chen
- Department of Medical Research, Chi Mei Medical Center, Tainan City, Taiwan
| | - Mei-Feng Lee
- Department of Medical Research, Chi Mei Medical Center, Tainan City, Taiwan
| | - Yin-Ching Chuang
- Division of Infectious Disease, Department of Internal Medicine, Chi Mei Medical Center, Liouying, Tainan City, Taiwan; Department of Medical Research, Chi Mei Medical Center, Tainan City, Taiwan
| | - Hung-Jen Tang
- Division of Infectious Disease, Department of Internal Medicine, Chi Mei Hospital, Tainan City, Taiwan; Department of Health and Nutrition, Chia Nan University of Pharmacy and Science, Tainan City, Taiwan
| | - Wen-Liang Yu
- Department of Intensive Care Medicine, Chi Mei Medical Center, Tainan City, Taiwan; Department of Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei City, Taiwan.
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Yu WL, Lee MF, Tang HJ, Chang MC, Chuang YC. Low prevalence of rmpA and high tendency of rmpA mutation correspond to low virulence of extended spectrum β-lactamase-producing Klebsiella pneumoniae isolates. Virulence 2016; 6:162-72. [PMID: 25830726 DOI: 10.1080/21505594.2015.1016703] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Invasive syndrome caused by Klebsiella pneumoniae (KP), including liver abscess, is mainly caused by community-acquired strains with characteristics of positive hypermucoviscosity (HV) phenotype and regulator of mucoid phenotype A (rmpA) and transcriptional activator (rmpA2) genes. Extended- spectrum β-lactamase-producing KP (ESBL-KP) is commonly nosocomial and rarely HV-positive. We aimed to explore the reasons of the rarer prevalence of HV phenotype, rmpA and rmpA2 as well as the virulence phenotype among the ESBL-KP isolates from clinical specimens than those non-ESBL isolates. The β-lactamase genes, rmpA, rmpA2 and genes for K capsule serotype of 440 KP isolates were analyzed. The virulence of the isolates was characterized by the mouse lethality experiments. The prevalence rates of HV phenotype (∼ 50% vs. < 10%) as well as rmpA and rmpA2 genes (∼ 50-60% vs. < 20-30%) were significantly higher in non-ESBL group than in the ESBL group (p < 0.0001). Expression of HV phenotype in the rmpA-positive KP isolates was significantly rarer in the ESBL group than in non-ESBL group (33.3% vs. 91.9%, p < 0.0001). The frameshift mutations of rmpA and/or rmpA2 corresponded to negative HV phenotype of KP isolates that harbored the rmpA and/or rmpA2, resulting in variable mouse lethality (LD50, ∼ 10(3) - >5 × 10(7) CFU). The mutation rates might significantly differ among KP isolates from various sources. Virulence was dependent on rmpA-related HV phenotype. In conclusion, ESBL-KP isolates were less hypermucoviscous and less virulent than non-ESBL KP isolates, mostly due to concurrently lower carriage and higher mutation rates of the rmpA and rmpA2 genes.
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Affiliation(s)
- Wen-Liang Yu
- a Department of Intensive Care Medicine ; Chi Mei Medical Center ; Tainan City , Taiwan
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Batah R, Loucif L, Olaitan AO, Boutefnouchet N, Allag H, Rolain JM. Outbreak of Serratia marcescens Coproducing ArmA and CTX-M-15 Mediated High Levels of Resistance to Aminoglycoside and Extended-Spectrum Beta-Lactamases, Algeria. Microb Drug Resist 2015; 21:470-6. [DOI: 10.1089/mdr.2014.0240] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Affiliation(s)
- Rima Batah
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM 63, CNRS 7278, IRD 198, INSERM 1905, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Université de la Méditerranée, Marseille, France
- Laboratoire de Biochimie et de Microbiologie Appliquée, Département de Biochimie, Université Badji Mokhtar Annaba, Annaba, Algerie
| | - Lotfi Loucif
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM 63, CNRS 7278, IRD 198, INSERM 1905, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Université de la Méditerranée, Marseille, France
- Laboratoire de Biotechnologie des Molecules Bioactives et de la Physiopathologie Cellulaire, Université El Hadj Lakhdar, Batna, Algerie
| | - Abiola Olumuyiwa Olaitan
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM 63, CNRS 7278, IRD 198, INSERM 1905, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Université de la Méditerranée, Marseille, France
| | - Nafissa Boutefnouchet
- Laboratoire de Biochimie et de Microbiologie Appliquée, Département de Biochimie, Université Badji Mokhtar Annaba, Annaba, Algerie
| | - Hamoudi Allag
- Laboratoire de Bactériologie, Clinique Rénale Daksi Constantine, Constantine, Algerie
| | - Jean-Marc Rolain
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM 63, CNRS 7278, IRD 198, INSERM 1905, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Université de la Méditerranée, Marseille, France
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Liou BH, Duh RW, Lin YT, Lauderdale TLY, Fung CP. A multicenter surveillance of antimicrobial resistance in Serratia marcescens in Taiwan. JOURNAL OF MICROBIOLOGY, IMMUNOLOGY, AND INFECTION = WEI MIAN YU GAN RAN ZA ZHI 2013; 47:387-93. [PMID: 23751769 PMCID: PMC7105062 DOI: 10.1016/j.jmii.2013.04.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 03/08/2013] [Accepted: 04/15/2013] [Indexed: 11/22/2022]
Abstract
Background Serratia marcescens is an important nosocomial pathogen and the characteristic property of resistance conferred by extended-spectrum beta-lactamase or a novel AmpC cephalosporinase was not unusual in Taiwan. This study investigated the trends in antimicrobial resistance in S. marcescens from a nationwide surveillance in Taiwan. Materials and methods S. marcescens isolates were collected biennially between 2002 and 2010 from medical centers and regional hospitals throughout Taiwan, as part of the Taiwan Surveillance of Antimicrobial Resistance program. Minimal inhibitory concentrations were determined by the Clinical and Laboratory Standards Institute reference broth microdilution method. Results A total of 403 nonduplicate S. marcescens isolates were collected, mostly from respiratory samples (157, 39.0%), followed by the urinary tract samples (90, 22.3%). Overall, 99.3% isolates were susceptible to imipenem, 93.8% to ceftazidime, 89.2% to minocycline, 87.8% to amikacin, 86.8% to cefepime, 82.9% to aztreonam, 73.2% to ceftriaxone, 72.7% to levofloxacin, 63.8% to ciprofloxacin, 60.8% to trimethoprim/sulfamethoxazole (TMP/SMX), and 59.6% to gentamicin. A significantly increased susceptibility rate after 2004 was observed for the following antibiotics: amikacin (73.8% vs. 97.1%), gentamicin (40.0% vs. 72.4%), ciprofloxacin (53.8% vs. 70.4%), ceftriaxone (53.8% vs. 86.0%), cefepime (74.4% vs. 95.1%), aztreonam (72.5% vs. 89.7%), and TMP/SMX (41.3% vs. 73.7%). Conclusion In this 8-year study, the susceptibility of S. marcescens to ceftazidime and imipenem remained consistently high in Taiwan. S. marcescens isolates demonstrated relatively higher resistance to ciprofloxacin and levofloxacin, and therefore continued surveillance of antimicrobial resistance, especially for fluoroquinolone, is warranted.
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Affiliation(s)
- Bo-Huang Liou
- Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Ruay-Wang Duh
- Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Yi-Tsung Lin
- Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
| | - Tsai-Ling Yang Lauderdale
- National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan, Taiwan
| | - Chang-Phone Fung
- Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan
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Schröppel K, Riessen R. [Multiresistant gram-negative bacteria. A bacterial challenge of the twenty-first century]. Med Klin Intensivmed Notfmed 2013; 108:107-12. [PMID: 23479223 DOI: 10.1007/s00063-012-0160-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 02/08/2013] [Indexed: 10/27/2022]
Abstract
The incidence of human-pathogenic microorganisms with resistance or even complete insensitivity to broad-spectrum antibiotics is increasing. This poses a serious challenge to infection control in hospitals and to hygiene strategies in clinical areas with critically ill patients, particularly intensive care or transplant units. These microorganisms create problems that are seemingly impossible to solve at present. The management of gram-positive pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) has been facilitated by evidence-based recommendations resulting in a measurable decrease in the incidence of infection and, where treatment is concerned, in a selection of reliably effective drugs for clinicians. However, in the more frequent cases of multiresistant gram-negative (MRGN) pathogens, the only option is the use of poorly defined regimens with older drugs, which carry the risk of serious side effects and organ toxicities. This article presents a comparative analysis of hospital hygiene management for MRSA and MRGN pathogens, pointing out both similarities and features which are unique to MRGN pathogens.
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Affiliation(s)
- K Schröppel
- medhyg Institut für Medizinhygiene, Denzenbergstr. 20, 72072, Tübingen.
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Eumkeb G, Chukrathok S. Synergistic activity and mechanism of action of ceftazidime and apigenin combination against ceftazidime-resistant Enterobacter cloacae. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2013; 20:262-269. [PMID: 23218402 DOI: 10.1016/j.phymed.2012.10.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2012] [Revised: 09/19/2012] [Accepted: 10/27/2012] [Indexed: 06/01/2023]
Abstract
The purpose of this investigation was to examine the antibacterial and synergistic effect of naturally occurring flavonoids, apigenin, quercetin, naringenin and ceftazidime when use singly and in combination against ceftazidime-resistant Enterobacter cloacae strains by minimum inhibitory concentration (MIC), checkerboard and viable count methods. The mode of actions were also studied by electronmicoscopy, enzyme assay, outer and inner membrane permeabilisation. The results showed that these strains were positive in the ESBL-ampC genes combination by multiplex PCR. These findings were confirmed by MICs that these strains were resistant to ceftazidime, cefepime and flomoxef at >1024, 16-24, >256 μg/ml respectively, while susceptible to imipenem at 1-2 μg/ml. The synergistic activity was observed at ceftazidime plus either apigenin or naringenin combinations with FIC indixes between <0.01 and <0.27 against these strains, whereas ceftazidime plus clavulanic acid or quercetin did not exhibit synergy. The modulation of ceftazidime-resistance by apigenin or narigenin significantly enhanced the activities of ceftazidime. The 5,7-OH group of A ring and one 4'-OH group of the B ring in apigenin and naringenin are important for synergistic activity. Viable counts showed that the killing of ceftazidime-resistant E. cloacae DMST 21394 (CREC) cells by 3 μg/ml ceftazidime was potentiated by 3 μg/ml apigenin to low levels (10(3) cfu/ml) over 6h. Electronmicroscopy clearly showed that ceftazidime 3 μg/ml in combination with 3 μg/ml of apigenin also caused marked morphological damage of cell wall, cell shape and plasma membrane of this strain. Enzymes assays indicated that apigenin showed marked inhibitory activity against penicillinase type IV from E. cloacae. The results for outer membrane (OM) permeabilization in both nitrocefin (NCF) assay and crystal violet uptake showed that the combination of ceftazidime plus apigenin significantly altered OM permeabilisation of CREC compared to control or single treatment of these agents. Both o-nitrophenyl-β-D-galactoside (ONPG) uptake and release of UV-absorbing material concentrations results exhibited that ceftazidime and apigenin combination damaged CREC cytoplasmic membrane (CM) and caused subsequent leakage of intracellular constituents. From the results, it can be concluded that apigenin and naringenin have the synergistic effect with ceftazidime to reverse bacterial resistance to this cephalosporin against CREC. This activity may be involved three mechanisms of action by apigenin. The first is on the peptidoglycan synthesis inhibition. The second mechanism is inhibition the activity of certain β-lactamase enzymes. The third mode of action is alteration of OM and CM permeabilization. Apigenin and naringenin have a sufficient margin of safety for therapeutic use. For this reason, apigenin and naringenin offer for the development of a valuable adjunct to ceftazidime against CREC, which currently almost cephalosporins resistance.
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Affiliation(s)
- Griangsak Eumkeb
- School of Pharmacology, Institute of Science, Suranaree University of Technology, Nakhonratchasima, Thailand.
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Phenotypic detection and polymerase chain reaction screening of extended-spectrum β-lactamases produced by Pseudomonas aeruginosa isolates. JOURNAL OF MICROBIOLOGY, IMMUNOLOGY, AND INFECTION = WEI MIAN YU GAN RAN ZA ZHI 2012; 45:200-7. [DOI: 10.1016/j.jmii.2011.11.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Revised: 07/14/2011] [Accepted: 08/09/2011] [Indexed: 11/22/2022]
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Lin KH, Chuang YC, Lee SH, Yu WL. In vitro synergistic antimicrobial effect of imipenem and colistin against an isolate of multidrug-resistant Enterobacter cloacae. JOURNAL OF MICROBIOLOGY, IMMUNOLOGY, AND INFECTION = WEI MIAN YU GAN RAN ZA ZHI 2010; 43:317-22. [PMID: 20688292 DOI: 10.1016/s1684-1182(10)60049-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Revised: 07/05/2009] [Accepted: 08/13/2009] [Indexed: 10/19/2022]
Abstract
BACKGROUND/PURPOSE Enterobacter cloacae is an important nosocomial pathogen responsible for various infections. Little is known about the synergistic effects of imipenem and colistin against multidrug-resistant E. cloacae. Therefore, we investigated the in vitro effects of imipenem and colistin against a clinical isolate of multidrug-resistant E. cloacae. METHODS A strain of E. cloacae, designed Ent 831, was isolated from the sputum of a woman who developed severe pneumonia in a medical intensive care unit. Minimal inhibitory concentrations (MICs) of imipenem and colistin were determined by the agar dilution method. The synergistic effects were investigated using the time-kill method. RESULTS MICs of imipenem and colistin for E. cloacae strain Ent 831 were 0.5 microg/mL and 1.0 microg/mL, respectively. Using a standard inoculum (5 x 10(5)) CFU/mL), synergism was shown with a concentration of two times the MICs of imipenem and colistin. Furthermore, four times the MIC of imipenem completely inhibited bacterial growth for more than 48 hours, but four times the MICs of colistin resulted in re-growth after 4 hours. There was no synergism between imipenem and colistin at two times the MICs against a high concentration inoculum (6.24 x 10(6)) CFU/mL). Nevertheless, imipenem, with or without colistin, at a concentration of four times MICs could inhibit the growth of bacteria for more than 48 hours. CONCLUSION High-dose imipenem, alone or in combination with colistin, is effective against multidrug-resistant E. cloacae. Colistin alone, even at a high dose, is not effective. However, in vitro susceptibility to antimicrobial compounds does not always correlate with clinical success. Thus further testing of these antibiotic combinations in animal models is needed in order to predict their suitability for clinical use.
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Affiliation(s)
- Kuan-Hung Lin
- Division of Infection Diseases and Department of Internal Medicine, Chi-Mei Medical Center, 901 Chung Hwa Road, Tainan, Taiwan
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