Evaluation of heteroresistance to polymyxin B among carbapenem-susceptible and -resistant Pseudomonas aeruginosa

2013 ◽  
Vol 62 (8) ◽  
pp. 1184-1189 ◽  
Author(s):  
Djuli M. Hermes ◽  
Caroline Pormann Pitt ◽  
Larissa Lutz ◽  
Aline B. Teixeira ◽  
Vanessa B. Ribeiro ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antimicrobial Susceptibility ◽  
Susceptibility Testing ◽  
Population Analysis ◽  
Polymyxin B ◽  
Antimicrobial Susceptibility Testing ◽  
Resistant Isolate ◽  
Variable Degree ◽  
Carbapenem Resistant ◽  
Colony Forming Units

One hundred and twenty-four Pseudomonas aeruginosa isolates were selected for antimicrobial susceptibility testing with anti-pseudomonal agents, MIC determination for polymyxin B and metallo-beta-lactamase detection (genes bla SPM, bla VIM-1, bla NDM-1 and bla IMP). 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–1 were considered heteroresistant. Isolates containing subpopulations that grew at polymyxin B concentrations at least twice as high as the original MIC but <2 mg l–1 were 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: MIC50 and MIC90 were 1 mg l–1 and 2 mg l–1, respectively. Thirty-seven isolates (30 %) were carbapenem-resistant. Four isolates resistant to carbapenems were positive for bla IMP. There were no heteroresistant subpopulations in the carbapenem-susceptible group, but three isolates presented heterogeneous subpopulations. The PAP frequency ranged from 2.1×10−4 to 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 2.1×10−7 to 2.6×10−4. In this study, polymyxin B heteroresistance in P. aeruginosa was uncommon and occurred in only one carbapenem-resistant isolate, despite the fact that several isolates presented heterogeneous subpopulations with increased polymyxin B MICs.

scholarly journals Multicenter Evaluation of Colistin Broth Disk Elution and Colistin Agar Test: a Report from the Clinical and Laboratory Standards Institute

2019 ◽  
Vol 57 (11) ◽  
Author(s):  
Romney M. Humphries ◽  
Daniel A. Green ◽  
Audrey N. Schuetz ◽  
Yehudit Bergman ◽  
Shawna Lewis ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antimicrobial Susceptibility ◽  
Susceptibility Testing ◽  
Polymyxin B ◽  
Antimicrobial Susceptibility Testing ◽  
Broth Microdilution ◽  
Content Type ◽  
Clinical Laboratories

ABSTRACT Susceptibility testing of the polymyxins (colistin and polymyxin B) is challenging for clinical laboratories. The Clinical and Laboratory Standards Institute (CLSI) Antimicrobial Susceptibility Testing Subcommittee evaluated two methods to enable accurate testing of these agents. These methods were a colistin broth disk elution (CBDE) and a colistin agar test (CAT), the latter of which was evaluated using two inoculum volumes, 1 μl (CAT-1) and 10 μl (CAT-10). The methods were evaluated using a collection of 270 isolates of Enterobacterales, 122 Pseudomonas aeruginosa isolates, and 106 Acinetobacter spp. isolates. Overall, 94.4% of CBDE results were in essential agreement and 97.9% in categorical agreement (CA) with reference broth microdilution MICs. Nine very major errors (VME; 3.2%) and 3 major errors (ME; 0.9%) were observed. With the CBDE, 98.6% CA was observed for Enterobacterales (2.5% VME, 0% ME), 99.3% CA was observed for P. aeruginosa (0% VME, 0.7% ME), and 93.1% CA was observed for Acinetobacter spp. (5.6% VME, 3.3% ME). Overall, CA was 94.9% with 6.8% VME using CAT-1 and improved to 98.3% with 3.9% VME using CAT-10. No ME were observed using either CAT-1 or CAT-10. Using the CAT-1/CAT-10, the CA observed was 99.4%/99.7% for Enterobacterales (1%/0.5% VME), 98.7%/100% for P. aeruginosa (8.3%/0% VME), and 88.5%/92.3% for Acinetobacter spp. (21.4%/14.3% VME). Based on these data, the CLSI antimicrobial susceptibility testing (AST) subcommittee endorsed the CBDE and CAT-10 methods for colistin testing of Enterobacterales and P. aeruginosa.

scholarly journals Polymyxin Susceptibility Testing and Interpretive Breakpoints: Recommendations from the United States Committee on Antimicrobial Susceptibility Testing (USCAST)

2019 ◽  
Vol 64 (2) ◽  
Author(s):  
Jason M. Pogue ◽  
Ronald N. Jones ◽  
John S. Bradley ◽  
David R. Andes ◽  
Sujata M. Bhavnani ◽  
...  
Keyword(s):  
United States ◽  
Antimicrobial Susceptibility ◽  
Susceptibility Testing ◽  
Polymyxin B ◽  
The United States ◽  
Antimicrobial Susceptibility Testing ◽  
Content Type ◽  
Carbapenem Resistant ◽  
Testing Strategies ◽  
Tract Infections

ABSTRACT The polymyxins are important agents for carbapenem-resistant Gram-negative bacilli. The United States Committee on Antimicrobial Susceptibility Testing breakpoint recommendations for colistin and polymyxin B are that isolates of Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterobacteriaceae are considered susceptible at MIC values of ≤2 mg/liter. These recommendations are contingent upon dosing and testing strategies that are described in this commentary. Importantly, these recommendations are not applicable to lower respiratory tract infections, for which we recommend no breakpoints. Furthermore, there is no breakpoint recommendation for polymyxin B for lower urinary tract infections.

scholarly journals Specific and rapid reverse assaying protocol for detection and antimicrobial susceptibility testing of Pseudomonas aeruginosa based on dual molecular recognition

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yong He ◽  
Hang Zhao ◽  
Yuanwen Liu ◽  
He Zhou
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antimicrobial Susceptibility ◽  
Magnetic Particles ◽  
Susceptibility Testing ◽  
Fluorescein Isothiocyanate ◽  
High Specificity ◽  
Antimicrobial Susceptibility Testing ◽  
Tail Fiber ◽  
Isolation And Identification ◽  
Magainin Ii

AbstractThe worldwide emergence and spread of antimicrobial resistance is accelerated by irrational administration and use of empiric antibiotics. A key point to the crisis is a lack of rapid diagnostic protocols for antimicrobial susceptibility testing (AST), which is crucial for a timely and rational antibiotic prescription. Here, a recombinant bacteriophage tail fiber protein (TFP) was functionalized on magnetic particles to specifically capture Pseudomonas aeruginosa, while fluorescein isothiocyanate-labeled-magainin II was utilized as the indicator. For solving the magnetic particles’ blocking effects, a reverse assaying protocol based on TFP recognition was developed to investigate the feasibility of detection and AST of P. aeruginosa. P. aeruginosa can be rapidly, sensitively and specifically detected within 1.5 h with a linear range of 1.0 × 102 to 1.0 × 106 colony forming units (CFU)⋅mL−1 and a detection limit of 3.3 × 10 CFU⋅mL−1. Subsequently, AST results, which were consistent with broth dilution results, can be obtained within 3.5 h. Due to the high specificity of the TFP, AST can actually be conducted without the need for bacterial isolation and identification. Based on the proof-of-principle work, the detection and AST of other pathogens can be extended by expressing the TFPs of their bacteriophages.

scholarly journals Rapid Colorimetric Assay for Antimicrobial Susceptibility Testing of Pseudomonas aeruginosa

2004 ◽  
Vol 48 (5) ◽  
pp. 1879-1881 ◽  
Author(s):  
Michael M. Tunney ◽  
Gordon Ramage ◽  
Tyler R. Field ◽  
Thomas F. Moriarty ◽  
Douglas G. Storey
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Excellent Agreement ◽  
Antimicrobial Susceptibility ◽  
Susceptibility Testing ◽  
Colorimetric Assay ◽  
Antimicrobial Susceptibility Testing ◽  
Tetrazolium Salt ◽  
Xtt Assay ◽  
Conventional Methods

ABSTRACT A colorimetric assay based on the reduction of a tetrazolium salt {2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT)} for rapidly determining the susceptibility of Pseudomonas aeruginosa isolates to bactericidal antibiotics is described. There was excellent agreement between the tobramycin and ofloxacin MICs determined after 5 h using the XTT assay and after 18 h using conventional methods. The data suggests that an XTT-based assay could provide a useful method for rapidly determining the susceptibility of P. aeruginosa to bactericidal antibiotics.

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