Reliability of the E-Test Method for Detection of Colistin Resistance in Clinical Isolates of
            <i>Acinetobacter baumannii</i>

Arroyo, Luis Alberto Rodríguez; García-Curiel, A.; Pachón-Ibáñez, María Eugenia; Llanos, Ana C.; Ruiz, María Teresa; Pachón, Jerónimo; Aznar, Javier

doi:10.1128/jcm.43.2.903-905.2005

Cited by 103 publications

(73 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The observation of elevated pmr expression in patient 4's initial isolate led us to wonder if this isolate was in fact colistin resistant, despite demonstrating susceptibility by E-test. E-tests have been previously shown to be reliable indicators of colistin resistance in A. baumannii, demonstrating good correlation with other standard susceptibility tests (Arroyo et al 2005). Here, however, we found that despite susceptibility by E-test (MIC [minimal inhibitory concentration] = 0.125), broth-microdilution (BMD) experiments showed growth of PT4-S well into the range of colistin concentrations associated with resistance (MIC = 64 mg/mL) (Supplemental Table S4).…”

Section: Evolution Of a Baumannii Colistin Resistancementioning

confidence: 90%

Genomic insights into the fate of colistin resistance and Acinetobacter baumannii during patient treatment

et al. 2013

View full text Add to dashboard Cite

Bacterial whole-genome sequencing (WGS) of human pathogens has provided unprecedented insights into the evolution of antibiotic resistance. Most studies have focused on identification of resistance mutations, leaving one to speculate on the fate of these mutants once the antibiotic selective pressure is removed. We performed WGS on longitudinal isolates of Acinetobacter baumannii from patients undergoing colistin treatment, and upon subsequent drug withdrawal. In each of the four patients, colistin resistance evolved via mutations at the pmr locus. Upon colistin withdrawal, an ancestral susceptible strain outcompeted resistant isolates in three of the four cases. In the final case, resistance was also lost, but by a compensatory inactivating mutation in the transcriptional regulator of the pmr locus. Notably, this inactivating mutation reduced the probability of reacquiring colistin resistance when subsequently challenged in vitro. On face value, these results supported an in vivo fitness cost preventing the evolution of stable colistin resistance. However, more careful analysis of WGS data identified genomic evidence for stable colistin resistance undetected by clinical microbiological assays. Transcriptional studies validated this genomic hypothesis, showing increased pmr expression of the initial isolate. Moreover, altering the environmental growth conditions of the clinical assay recapitulated the classification as colistin resistant. Additional targeted sequencing revealed that this isolate evolved undetected in a patient undergoing colistin treatment, and was then transmitted to other hospitalized patients, further demonstrating its stability in the absence of colistin. This study provides a unique window into mutational pathways taken in response to antibiotic pressure in vivo, and demonstrates the potential for genome sequence data to predict resistance phenotypes.

show abstract

Section: Evolution Of a Baumannii Colistin Resistancementioning

confidence: 90%

Genomic insights into the fate of colistin resistance and Acinetobacter baumannii during patient treatment

et al. 2013

View full text Add to dashboard Cite

show abstract

“…MICs of the CIP, GEN, PIP/tazobactam, CAZ and IMP were determined by E-test strip (Hi-Media) test as described by the manufacturer's instructions. MICs of the CLS were determined by E-test strip (Hi-Media) as described by the manufacturer's instructions and also by colistin sulfate (Sigma) broth dilution as described previously by Arroyo et al (2005). Isolates at least resistant to three classes of antibiotics were considered as MDR-AB as previously described by Manchanda et al (2010).…”

Section: Methodsmentioning

confidence: 99%

Class 1 integrons in non-clonal multidrug-resistant Acinetobacter baumannii from Iran, description of the new bla IMP-55 allele in In1243

Azizi

Shakibaie

Badmasti

et al. 2016

Journal of Medical Microbiology

View full text Add to dashboard Cite

Infections and outbreaks caused by multidrug-resistant Acinetobacter baumannii (MDR-AB) are prevalent and have been reported worldwide over the past 20 or more years. Class 1 integron in MDR-AB plays an important role in the spread of antibiotic resistance in clinical settings. This study has been conducted to evaluate the detection of metallo-b-lactamase, characterization of class 1 integron and determination of clonal relatedness among A. baumannii hospital isolates. Sixty-five clinical isolates of MDR-AB were recovered from two Iranian hospital's intensive care units from February to August 2013. Integrase (intI1) and bla IMP genes were detected in 70.8 % (n=46/65) and 9.23 % (n=6/65) of the isolates using PCR assay, respectively. No other metallo-b-lactamase genes (bla VIM , bla SIM and bla NDM ) were detected. PCR sequencing of integron gene cassette revealed the following arrays: bla OXA10 -aacA4-bla IMP-55 -cmlA5 (as a novel array was designated In1243), aacC1 and aadA1. Analysis of bla IMP gene revealed a new allele designated as bla . Gene transfer experiment by conjugation showed the 36 kb conjugative plasmid harbouring In1243. The clonal assessment by repetitive extragenic palindromic PCR demonstrated a high-degree relatedness among the strains, but strains harbouring In1243 displayed a different repetitive extragenic palindromic PCR profile. In this study, we found that a novel class 1 integron (In1243) that encoded a new bla IMP allele resided on a transferable plasmid in non-clonal strains of MDR-AB.

show abstract

“…High error rates and low levels of reproducibility of the disk diffusion method for detecting colistin resistance are well documented (4), but Etest has shown excellent agreement with agar dilution (AD) and broth microdilution for testing colistin resistance in major Gram-negative bacteria (4)(5)(6). However, the performance of automated antimicrobial susceptibility testing systems has rarely been assessed in terms of determining colistin susceptibility in Acinetobacter species, especially for non-baumannii Acinetobacter strains (4,7).…”

mentioning

confidence: 99%

Comparison of the Vitek 2, MicroScan, and Etest Methods with the Agar Dilution Method in Assessing Colistin Susceptibility of Bloodstream Isolates of Acinetobacter Species from a Korean University Hospital

et al. 2013

View full text Add to dashboard Cite

cWe evaluated three commercial colistin susceptibility testing methods using 213 bloodstream Acinetobacter isolates identified by gene sequencing. Compared to the agar dilution reference method, excellent categorical agreements (both 99.1%) were observed using Vitek 2 and Etest, compared to 87.3% (95.7% for Acinetobacter baumannii and 80.7% for non-baumannii Acinetobacter isolates) using MicroScan.

show abstract

Reliability of the E-Test Method for Detection of Colistin Resistance in Clinical Isolates of Acinetobacter baumannii

Cited by 103 publications

References 16 publications

Genomic insights into the fate of colistin resistance and Acinetobacter baumannii during patient treatment

Genomic insights into the fate of colistin resistance and Acinetobacter baumannii during patient treatment

Class 1 integrons in non-clonal multidrug-resistant Acinetobacter baumannii from Iran, description of the new bla IMP-55 allele in In1243

Comparison of the Vitek 2, MicroScan, and Etest Methods with the Agar Dilution Method in Assessing Colistin Susceptibility of Bloodstream Isolates of Acinetobacter Species from a Korean University Hospital

Contact Info

Product

Resources

About