Evaluation of susceptibility testing methods for polymyxin

Behera, Bijayini; Mathur, Purva; Das, Anupam; Kapil, Arti; Gupta, Babita; Bhoi, Sanjeev Kumar; Farooque, Kamran; Sharma, Vijay; Misra, Manesh C

doi:10.1016/j.ijid.2009.09.001

Cited by 64 publications

(72 citation statements)

References 12 publications

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“…For colistin resistant, E-test was further used after the initial screening using disk diffusion. Although low sensitivity of E-test on detecting colistin resistant strains has been reported recently, 58 our results in this study was considered reliable as no zone of inhibition was observed for three colistin strains in two repeated experiments. However, the strains will be further subjected to the other MIC detection methods, such as broth macrodilution (TDS) and broth microdilution with polysorbate 80 (BMD-T) for further comparison and evaluation.…”

supporting

confidence: 58%

Intestinal carriage of multidrug-resistant gram-negative bacteria in preterm-infants during hospitalization in neonatal intensive care unit (NICU)

Yap

Kamar

Chong

et al. 2016

Pathogens and Global Health

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The prevalence and antibiotic susceptibility of intestinal carriage of Gram-negative bacteria among preterm infants admitted to the neonatal intensive care unit (NICU) in a tertiary teaching hospital in Malaysia were determined. A total of 34 stool specimens were obtained from preterm infants upon admission and once weekly up to two weeks during hospitalization. The presumptive colonies of Escherichia coli and Klebsiella pneumoniae were selected for identification, antibiotic susceptibility testing, and subtyping by using pulsed-field gel electrophoresis (PFGE). Out of 76 Gram-negative isolates, highest resistance was detected for amoxicillin/clavulanate (30.8%, n = 16), ceftriaxone (42.3%, n = 22), ceftazidime (28.8%, n = 15), cefoxitin (28.8%, n = 15), aztreonam (36.5%, n = 19), and polymyxin B (23.1%, n = 12). Three colistin resistant K. pneumoniae have also been detected based on Etest analysis. Thirty-nine isolates of K. pneumoniae and 20 isolates of E. coli were resistant to more than three antimicrobial classes and were categorized as multidrug resistant (MDR). PFGE analysis revealed a higher diversity in pulsotypes for K. pneumoniae (18 pulsotypes) in comparison to E. coli (four pulsotypes). In addition, a total of fifteen pulsotypes was observed from 39 MDR K. pneumoniae. The risk factors for antibiotic resistance were assessed using random forest analysis. Gender was found to be the most important predictor for colistin resistant while length, OFC, and delivery mode were showing greater predictive power in the polymyxin B resistance. This study revealed worrying prevalence rates of intestinal carriage of multidrug-resistant K. pneumoniae and E. coli of hospitalized preterm infants in Malaysia, particularly high resistance to polymyxins.

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supporting

confidence: 58%

Intestinal carriage of multidrug-resistant gram-negative bacteria in preterm-infants during hospitalization in neonatal intensive care unit (NICU)

Yap

Kamar

Chong

et al. 2016

Pathogens and Global Health

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“…Numerous studies have demonstrated a strong correlation between agar dilution and BMD (70,75,76), with the exception of results obtained with P. aeruginosa and S. maltophilia isolates from cystic fibrosis patients (77,78). One advantage of the agar dilution method is the ability to test multiple strains on the same plate and the possibility to semiautomate the method.…”

Section: Dilution Methodsmentioning

confidence: 99%

“…The MIC value is defined by the intersection of the lower part of the ellipse-shaped growth inhibition area with the test strip. When the intersection occurs around the MIC endpoint, the highest MIC intersection is recorded (75). When small colonies grow within the zone of inhibition, the strain must be considered heteroresistant to colistin, and the highest MIC intersection is recorded (75,81).…”

Section: Nonautomatic Systems (I) Dd Test (Kirby-bauer Procedure)mentioning

confidence: 99%

“…Several studies, notably including few resistant isolates, found an excellent correlation between the Etest and reference techniques (75,76,80,82). However, studies including larger numbers of resistant isolates reported high rates of false susceptibility (up to 32%) for Gram-negative rods compared to those with dilution methods (69,70,78,83).…”

Section: Nonautomatic Systems (I) Dd Test (Kirby-bauer Procedure)mentioning

confidence: 99%

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Polymyxins: Antibacterial Activity, Susceptibility Testing, and Resistance Mechanisms Encoded by Plasmids or Chromosomes

2017

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SUMMARY Polymyxins are well-established antibiotics that have recently regained significant interest as a consequence of the increasing incidence of infections due to multidrug-resistant Gram-negative bacteria. Colistin and polymyxin B are being seriously reconsidered as last-resort antibiotics in many areas where multidrug resistance is observed in clinical medicine. In parallel, the heavy use of polymyxins in veterinary medicine is currently being reconsidered due to increased reports of polymyxin-resistant bacteria. Susceptibility testing is challenging with polymyxins, and currently available techniques are presented here. Genotypic and phenotypic methods that provide relevant information for diagnostic laboratories are presented. This review also presents recent works in relation to recently identified mechanisms of polymyxin resistance, including chromosomally encoded resistance traits as well as the recently identified plasmid-encoded polymyxin resistance determinant MCR-1. Epidemiological features summarizing the current knowledge in that field are presented.

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“…Manual BMD, however, is laborious and not performed in many routine clinical microbiology laboratories, which often rely on diffusion or automated systems for susceptibility testing. Moreover, and somewhat paradoxically in view of the drugs' poor diffusion in agar, diffusion methods (both disk and gradient strips) have been found to have unacceptably high levels of false susceptibility (or very major errors [VMEs]) in multiple studies (12,(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28) (Table 1). Both the CLSI and EUCAST have now advised against diffusion methods for the polymyxins, removing disk diffusion interpretive criteria for them from their guidance documents (9,15,22).…”

mentioning

confidence: 99%

Susceptibility Testing for the Polymyxins: Two Steps Back, Three Steps Forward?

Vasoo

2017

J Clin Microbiol

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Optimizing and standardizing susceptibility testing for the polymyxins have become pressing issues, given the rise in multidrug-resistant Gram-negative bacilli. Recently, both the CLSI and EUCAST have recommended broth microdilution (BMD) (without polysorbate) as the reference method for polymyxin susceptibility testing. In this issue, K. L. Chew et al. (J Clin Microbiol 55:2609 -2616, https://doi .org/10.1128/JCM.00268-17) compare the performances of three commercial BMD panels and the Etest to the reference, BMD, for polymyxin B and colistin, using 76 Enterobacteriaceae isolates (21 of which were mcr-1 positive). Although none of the commercial BMD panels strictly met FDA performance standards in this evaluation, possibly because of the small number isolates tested, the Sensititre panel achieved Ͼ90% categorical agreement for both polymyxin compounds. These results also reaffirm CLSI and EUCAST guidance that gradient diffusion testing, which had unacceptable error rates, should be abandoned. In a simulated analysis with lowered breakpoints (susceptible, Յ1 mg/liter; intermediate, 2 mg/liter; resistant, Ն4 mg/liter), error rates and agreement were improved across the various methods and the rate of detection of mcr-1-positive isolates improved. These observations, taken together with recent pharmacokinetic data on optimizing target attainment for the polymyxins, suggest that more-stringent (lower) breakpoints may be reasonable, although such an approach may be limited by the inherent reliability of current testing methodologies and a lack of robust clinical correlative data, which are sorely needed. S usceptibility testing for the polymyxins has been beleaguered over the years. The polymyxins were first isolated from Paenibacillus polymyxa in 1947 by two independent American groups (1, 2), and there has been a therapeutic renaissance in the use of both polymyxin B and colistin (polymyxin E) over the last decade, given the rise of multidrug-resistant (MDR) Gram-negative bacilli, such as MDR Acinetobacter and Pseudomonas and carbapenemase-producing Enterobacteriaceae.Despite susceptibility testing being available for a long time, clarity has been lacking for appropriate methods of testing and optimal dosing for the polymyxins. Polymyxins are cationic polypeptides comprised of a heptapeptide ring, an exocyclic chain, and a fatty acid tail with positively charged residues which interact with and disrupt the Gram-negative lipopolysaccharide membrane; polymyxin B and colistin differ by only one amino acid in the heptapeptide ring (3, 4). Several reasons have accounted for difficulties with susceptibility testing for the polymyxins, including their cationic nature, their poor diffusion in agar due to their large molecular size, concerns over drug powder composition, and their heteroresistance. Further, the complex pharmacokinetics (PK) and pharmacodynamics (PD) of these compounds and the paucity of data correlating MIC data, drug concentration, and clinical outcomes have made setting clinical breakpoints chal...

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Evaluation of susceptibility testing methods for polymyxin

Abstract: The E-test and agar dilution methods showed good concordance with BMD. The disk diffusion method can be useful for initial screening in diagnostic laboratories.

Cited by 64 publications

References 12 publications

Intestinal carriage of multidrug-resistant gram-negative bacteria in preterm-infants during hospitalization in neonatal intensive care unit (NICU)

Intestinal carriage of multidrug-resistant gram-negative bacteria in preterm-infants during hospitalization in neonatal intensive care unit (NICU)

Polymyxins: Antibacterial Activity, Susceptibility Testing, and Resistance Mechanisms Encoded by Plasmids or Chromosomes

Susceptibility Testing for the Polymyxins: Two Steps Back, Three Steps Forward?

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