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Relationships among ciprofloxacin, gatifloxacin, levofloxacin, and norfloxacin MICs for fluoroquinolone-resistant Escherichia coli clinical isolates.
Antimicrob Agents Chemother. 2009 Jan; 53(1):229-34.AA

Abstract

Fluoroquinolones are some of the most prescribed antibiotics in the United States. Previously, we and others showed that the fluoroquinolones exhibit a class effect with regard to the CLSI-established breakpoints for resistance, such that decreased susceptibility (i.e., an increased MIC) to one fluoroquinolone means a simultaneously decreased susceptibility to all. For defined strains, however, clear differences exist in the pharmacodynamic properties of each fluoroquinolone and the extent to which resistance-associated genotypes affect the MICs of each fluoroquinolone. In a pilot study of 920 clinical Escherichia coli isolates, we uncovered tremendous variation in norfloxacin MICs. The MICs for all of the fluoroquinolone-resistant isolates exceeded the resistance breakpoint, reaching 1,000 microg/ml. Approximately 25% of the isolates (n = 214), representing the full range of resistant norfloxacin MICs, were selected for the simultaneous determinations of ciprofloxacin, gatifloxacin, levofloxacin, and norfloxacin MICs. We found that (i) great MIC variation existed for all four fluoroquinolones, (ii) the ciprofloxacin and levofloxacin MICs of >90% of the fluoroquinolone-resistant isolates were higher than the resistance breakpoints, (iii) ciprofloxacin and levofloxacin MICs were distributed into two distinct groups, (iv) the MICs of two drug pairs (ciprofloxacin and norfloxacin by Kendall's Tau-b test and gatifloxacin and levofloxacin by paired t test) were similar with statistical significance but were different from each other, and (v) approximately 2% of isolates had unprecedented fluoroquinolone MIC relationships. Thus, although the fluoroquinolones can be considered equivalent with regard to clinical susceptibility or resistance, fluoroquinolone MICs differ dramatically for fluoroquinolone-resistant clinical isolates, likely because of differences in drug structure.

Authors+Show Affiliations

elz@bcm.edu.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

18838594

Citation

Becnel Boyd, Lauren, et al. "Relationships Among Ciprofloxacin, Gatifloxacin, Levofloxacin, and Norfloxacin MICs for Fluoroquinolone-resistant Escherichia Coli Clinical Isolates." Antimicrobial Agents and Chemotherapy, vol. 53, no. 1, 2009, pp. 229-34.
Becnel Boyd L, Maynard MJ, Morgan-Linnell SK, et al. Relationships among ciprofloxacin, gatifloxacin, levofloxacin, and norfloxacin MICs for fluoroquinolone-resistant Escherichia coli clinical isolates. Antimicrob Agents Chemother. 2009;53(1):229-34.
Becnel Boyd, L., Maynard, M. J., Morgan-Linnell, S. K., Horton, L. B., Sucgang, R., Hamill, R. J., Jimenez, J. R., Versalovic, J., Steffen, D., & Zechiedrich, L. (2009). Relationships among ciprofloxacin, gatifloxacin, levofloxacin, and norfloxacin MICs for fluoroquinolone-resistant Escherichia coli clinical isolates. Antimicrobial Agents and Chemotherapy, 53(1), 229-34. https://doi.org/10.1128/AAC.00722-08
Becnel Boyd L, et al. Relationships Among Ciprofloxacin, Gatifloxacin, Levofloxacin, and Norfloxacin MICs for Fluoroquinolone-resistant Escherichia Coli Clinical Isolates. Antimicrob Agents Chemother. 2009;53(1):229-34. PubMed PMID: 18838594.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Relationships among ciprofloxacin, gatifloxacin, levofloxacin, and norfloxacin MICs for fluoroquinolone-resistant Escherichia coli clinical isolates. AU - Becnel Boyd,Lauren, AU - Maynard,Merry J, AU - Morgan-Linnell,Sonia K, AU - Horton,Lori Banks, AU - Sucgang,Richard, AU - Hamill,Richard J, AU - Jimenez,Javier Rojo, AU - Versalovic,James, AU - Steffen,David, AU - Zechiedrich,Lynn, Y1 - 2008/10/06/ PY - 2008/10/8/pubmed PY - 2009/4/21/medline PY - 2008/10/8/entrez SP - 229 EP - 34 JF - Antimicrobial agents and chemotherapy JO - Antimicrob. Agents Chemother. VL - 53 IS - 1 N2 - Fluoroquinolones are some of the most prescribed antibiotics in the United States. Previously, we and others showed that the fluoroquinolones exhibit a class effect with regard to the CLSI-established breakpoints for resistance, such that decreased susceptibility (i.e., an increased MIC) to one fluoroquinolone means a simultaneously decreased susceptibility to all. For defined strains, however, clear differences exist in the pharmacodynamic properties of each fluoroquinolone and the extent to which resistance-associated genotypes affect the MICs of each fluoroquinolone. In a pilot study of 920 clinical Escherichia coli isolates, we uncovered tremendous variation in norfloxacin MICs. The MICs for all of the fluoroquinolone-resistant isolates exceeded the resistance breakpoint, reaching 1,000 microg/ml. Approximately 25% of the isolates (n = 214), representing the full range of resistant norfloxacin MICs, were selected for the simultaneous determinations of ciprofloxacin, gatifloxacin, levofloxacin, and norfloxacin MICs. We found that (i) great MIC variation existed for all four fluoroquinolones, (ii) the ciprofloxacin and levofloxacin MICs of >90% of the fluoroquinolone-resistant isolates were higher than the resistance breakpoints, (iii) ciprofloxacin and levofloxacin MICs were distributed into two distinct groups, (iv) the MICs of two drug pairs (ciprofloxacin and norfloxacin by Kendall's Tau-b test and gatifloxacin and levofloxacin by paired t test) were similar with statistical significance but were different from each other, and (v) approximately 2% of isolates had unprecedented fluoroquinolone MIC relationships. Thus, although the fluoroquinolones can be considered equivalent with regard to clinical susceptibility or resistance, fluoroquinolone MICs differ dramatically for fluoroquinolone-resistant clinical isolates, likely because of differences in drug structure. SN - 1098-6596 UR - https://www.unboundmedicine.com/medline/citation/18838594/Relationships_among_ciprofloxacin_gatifloxacin_levofloxacin_and_norfloxacin_MICs_for_fluoroquinolone_resistant_Escherichia_coli_clinical_isolates_ L2 - http://aac.asm.org/cgi/pmidlookup?view=long&pmid=18838594 DB - PRIME DP - Unbound Medicine ER -