Evaluation of heteroresistance to polymyxin B among carbapenem-susceptible and -resistant Pseudomonas aeruginosa
| Autor: | Aline Borges Teixeira, Vanessa Bley Ribeiro, Bárbara Netto, Djuli Milene Hermes, Alexandre P. Zavascki, Caroline Pormann Pitt, Andreza Francisco Martins, Larissa Lutz, Afonso Luis Barth |
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| Rok vydání: | 2013 |
| Předmět: |
Microbiology (medical)
Carbapenem Imipenem Cystic Fibrosis Genotype medicine.drug_class Polymyxin Population Bacteremia Microbial Sensitivity Tests Aztreonam Biology medicine.disease_cause Microbiology Meropenem beta-Lactamases chemistry.chemical_compound Drug Resistance Bacterial medicine Ascitic Fluid Humans Pseudomonas Infections education Demography Polymyxin B education.field_of_study Pseudomonas aeruginosa Sputum General Medicine Anti-Bacterial Agents Phenotype Carbapenems chemistry Brazil medicine.drug |
| Zdroj: | Journal of Medical Microbiology. 62:1184-1189 |
| ISSN: | 1473-5644 0022-2615 |
| DOI: | 10.1099/jmm.0.059220-0 |
| Popis: | One hundred and twenty-fourPseudomonas aeruginosaisolates were selected for antimicrobial susceptibility testing with anti-pseudomonal agents, MIC determination for polymyxin B and metallo-beta-lactamase detection (genesblaSPM,blaVIM-1,blaNDM-1andblaIMP). According to the imipenem and/or meropenem susceptibility profile, a set of randomly selected isolates (12 isolates carbapenem-susceptible and 12 isolates carbapenem-resistant) were evaluated for heteroresistance to polymyxin B. Heteroresistance testing was performed by plating the isolates onto increasing concentrations of polymyxin B (from 0 to 8.0 mg l–1). The population analysis profile (PAP) was defined as the ratio of the number of colony-forming units on the plate with the highest concentration of polymyxin B at which bacterial growth occurred against the number of colony-forming units on the plate without antibiotic. Isolates presenting subpopulations that exhibited growth at polymyxin B concentrations ≥2 mg l–1were considered heteroresistant. Isolates containing subpopulations that grew at polymyxin B concentrations at least twice as high as the original MIC but –1were considered heterogeneous. Antimicrobial susceptibility testing results indicated a variable degree of susceptibility: high levels of resistance to gentamicin (30.6 %) and imipenem (29.0 %); low levels of resistance to aztreonam (1.6 %) and ciprofloxacin (4.8 %). All isolates were susceptible to polymyxin B: MIC50and MIC90were 1 mg l–1and 2 mg l–1, respectively. Thirty-seven isolates (30 %) were carbapenem-resistant. Four isolates resistant to carbapenems were positive forblaIMP. There were no heteroresistant subpopulations in the carbapenem-susceptible group, but three isolates presented heterogeneous subpopulations. The PAP frequency ranged from 2.1×10−4to 6.9×10−8. In the carbapenem-resistant group, one isolate was heteroresistant. Six isolates in this group presented heterogeneous subpopulations. In the resistant population, the PAP frequency ranged from 2.1×10−7to 2.6×10−4. In this study, polymyxin B heteroresistance inP. aeruginosawas uncommon and occurred in only one carbapenem-resistant isolate, despite the fact that several isolates presented heterogeneous subpopulations with increased polymyxin B MICs. |
| Databáze: | OpenAIRE |
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