Broth Microdilution and E-Test for Determining Fluoroquinolone Activity against Streptococcus Pneumoniae

Abstract

Spanish

French

OBJECTIVE:

To compare broth microdilution and E-test minimum inhibitory concentrations (MICs) of 4 fluoroquinolones against Streptococcus pneumoniae and to determine the effect of these in vitro MIC methods on the calculation of AUC_0–24/MIC ratios.

METHODS:

Levofloxacin, gatifloxacin, moxifloxacin, and gemifloxacin MICs were determined by broth microdilution (incubated in air) and E-test (incubated in CO₂) for 100 clinical isolates of S. pneumoniae. MIC₅₀, MIC₉₀, and geometric mean MIC were calculated. Steady-state serum concentration—time profiles were simulated for once-daily, oral dosing of levofloxacin 500 mg, gatifloxacin 400 mg, moxifloxacin 400 mg, and gemifloxacin 320 mg. After correcting for protein binding, AUC_0–24 of unbound drug was calculated for each regimen, and AUC_0–24/MIC ratios were calculated using MIC data from both in vitro methods. Differences in MICs between methods were determined for each agent using the paired t-test (after logarithmic transformation of MICs) and the Wilcoxon signed-rank test. Differences in AUC_0–24/MIC ratios were also determined using the paired t-test and the Wilcoxon signed-rank test. The level of significance for all analyses was p < 0.05.

RESULTS:

Broth microdilution and E-test MICs were within ± 1 log₂ dilution for 94%, 93%, 61%, and 35% of the isolates for levofloxacin, gatifloxacin, moxifloxacin, and gemifloxacin, respectively. Broth microdilution MICs were significantly lower than E-test MICs for all 4 agents (p < 0.001). However, a categorical change in susceptibility was seen for only 1 isolate with gatifloxacin and moxifloxacin (intermediate by broth microdilution, resistant by E-test). AUC_0–24/MIC ratios were significantly higher for each regimen when MICs were determined by broth microdilution compared with E-test (p < 0.001).

CONCLUSIONS:

There is a significant difference in the activity of the newer fluoroquinolones against S. pneumoniae when MICs are determined by broth microdilution and E-test. When evaluating fluoroquinolone activity and pharmacodynamics against this organism, clinicians must be aware that MIC testing methodology may have a significant impact on the results.

Keywords

E-test fluoroquinolones microdilution

Get full access to this article

View all access options for this article.

References

Appelbaum

. Epidemiology and in vitro susceptibility of drug-resistant Streptococcus pneumoniae . Pediatr Infect Dis J 1996; 15: 932–9.

Doern

Pfaller

Kugler

Freeman

Jones

. Prevalence of antimicrobial resistance among respiratory tract isolates of Streptococcus pneumoniae in North America: 1997 results from the SENTRY Antimicrobial Surveillance Program. Clin Infect Dis 1998; 27: 764–70.

Jacobs

Bajaksouzian

Lin

Zilles

Pankuch

Appelbaum

. Susceptibility of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis to oral agents: Results of a 1998 US outpatient surveillance study (abstract 61). In: Programs and abstracts of the 39th Interscience Conference on Antimicrobial Agents and Chemotherapy, San Francisco, September 27, 1999.

Jacobs

Bajaksouzian

Zilles

Lin

Pankuch

Appelbaum

. Susceptibilities of Streptococcus pneumoniae and Haemophilus influenzae to 10 oral antimicrobial agents based on pharmacodynamic parameters: 1997 US surveillance study. Antimicrob Agents Chemother 1999; 43: 1901–8.

Bauernfeind

. Comparison of the antibacterial activities of the quinolones Bay 12–8039, gatifloxacin (AM 1155), trovafloxacin, clinafloxacin, levofloxacin, and ciprofloxacin. J Antimicrob Chemother 1997; 40: 639–51.

Blondeau

. A review of the comparative in-vitro activities of 12 antimicrobial agents, with a focus on five new “respiratory quinolones.” J Antimicrob Chemother 1999;43 (suppl B):1–11.

Pankuch

Jacobs

Appelbaum

. Activity of CP 99,219 compared to DU-6859a, ciprofloxacin, ofloxacin, levofloxacin, lomefloxacin, tosufloxacin, sparfloxacin and grepafloxacin against penicillin-susceptible and resistant pneumococci. J Antimicrob Chemother 1995; 35: 230–2.

Davies

Kelly

Pankuch

Credito

Jacobs

Appelbaum

. Antipneumococccal activities of gemifloxacin compared to those of nine other agents. Antimicrob Agents Chemother 2000; 44: 304–10.

Bartlett

Dowell

Mandell

File

Musher

Fine

. Practice guidelines for the management of community-acquired pneumonia in adults. Clin Infect Dis 2000; 31: 347–82.

10.

Craig

. Pharmacokinetic/pharmacodynamic parameters: Rationale for antibacterial dosing of mice and men. Clin Infect Dis 1998; 26: 1–12.

11.

Lister

Sanders

. Pharmacodynamics of levofloxacin and ciprofloxacin against Streptococcus pneumoniae . J Antimicrob Chemother 1999; 43: 79–86.

12.

Lacy

Tessier

Nicolau

Quintiliani

. Pharmacodynamic comparisons of levofloxacin, ciprofloxacin, and ampicillin against Streptococcus pneumoniae in an in vitro model of infection. Antimicrob Agents Chemother 1999; 43: 672–7.

13.

Craig

Andes

. Correlation of the magnitude of the AUC₂₄/MIC for 6 fluoroquinolones against Streptococcus pneumoniae with survival and bactericidal activity in an animal model (abstract 289). In: Programs and abstracts of the 40th Interscience Conference on Antimicrobial Agents and Chemotherapy, Toronto, September 17, 2000.

14.

National Committee for Clinical Laboratory Standards. Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically. Approved standard, M7-A5. Wayne, PA: National Committee for Clinical Laboratory Standards, 2000.

15.

Tanigawara

Nomura

Kagimoto

Okumura

Hori

. Premarketing population pharmacokinetic study of levofloxacin in normal subjects and patients with infectious diseases. Biol Pharm Bull 1995; 18: 315–20.

16.

Chien

Chow

Natarajan

Williams

Wong

Rogge

. Absence of age and gender effects on the pharmacokinetics of a single 500-milligram oral dose of levofloxacin in healthy subjects. Antimicrob Agents Chemother 1997; 41: 1562–5.

17.

Chien

Rogge

Gisclon

Curtin

Wong

Natarajan

. Pharmacokinetic profile of levofloxacin following once-daily 500-milligram oral and intravenous doses. Antimicrob Agents Chemother 1997; 41: 2256–60.

18.

Chien

Wong

Fowler

Callery-D'Amico

Williams

Nayak

. Double-blind evaluation of the safety and pharmacokinetics of multiple oral once-daily 750-milligram and 1-gram doses of levofloxacin in healthy volunteers. Antimicrob Agents Chemother 1998; 42: 885–8.

19.

Nakashima

Uematsu

Kosuge

Kusajima

Ooie

Masuda

. Single- and multiple-dose pharmacokinetics of AM-1155, a new 6-fluoro-8-methoxy quinolone, in humans. Antimicrob Agents Chemother 1995; 39: 2635–40.

20.

Grasela

Christofalo

Kollia

Duncan

Noveck

Manning

Jr. . Safety and pharmacokinetics of a single oral dose of gatifloxacin in patients with moderate to severe hepatic impairment. Pharmacotherapy 2000; 20 (pt 2):87S–94S.

21.

Grasela

Cirincione

Christofalo

Pierce

Hiles

Grasela

. Population pharmacokinetics of gatifloxacin in adults with acute bacterial exacerbation of chronic bronchitis (abstract A-28). In: Programs and abstracts of the 38th Interscience Conference on Antimicrobial Agents and Chemotherapy, San Diego, September 25, 1998.

22.

LaCreta

Kollia

Duncan

Behr

Stoltz

Grasela

. Effect of a high-fat meal on the bioavailability of gatifloxacin in healthy volunteers (abstract A-31). In: Programs and abstracts of the 38th Interscience Conference on Antimicrobial Agents and Chemotherapy, San Diego, September 25, 1998.

23.

Lober

Ziege

Rau

Schreiber

Mignot

Koeppe

. Pharmacokinetics of gatifloxacin and interaction with an antacid containing aluminum and magnesium. Antimicrob Agents Chemother 1999; 43: 1067–71.

24.

Gajjar

LaCreta

Uderman

Kollia

Duncan

Birkhofer

. A dose-escalation study of the safety, tolerability, and pharmacokinetics of intravenous gatifloxacin in healthy adult men. Pharmacotherapy 2000; 20 (pt 2):49S–58S.

25.

LaCreta

Kaul

Kollia

Duncan

Randall

Grasela

. Interchangeability of 400-mg intravenous and oral gatifloxacin in healthy adults. Pharmacotherapy 2000; 20 (pt 2):59S–66S.

26.

Stass

Dalhoff

Kubitza

Schuhly

. Pharmacokinetics, safety, and tolerability of ascending single doses of moxifloxacin, a new 8-methoxy quinolone, administered to healthy subjects. Antimicrob Agents Chemother 1998; 42: 2060–5.

27.

Wise

Andrews

Marshall

Hartman

. Pharmacokinetics and inflammatory-fluid penetration of moxifloxacin following oral or intravenous administration. Antimicrob Agents Chemother 1999; 43: 1508–10.

28.

Stass

Kubitza

. Pharmacokinetics and elimination of moxifloxacin after oral and intravenous administration in man. J Antimicrob Chemother 1999; 43 (suppl B):83–90.

29.

Wise

. A review of the clinical pharmacology of moxifloxacin, a new 8-methoxyquinolone, and its potential relation to therapeutic efficacy. Clin Drug Invest 1999; 17: 365–87.

30.

Allen

Vousden

Lewis

. Effect of omeprazole on the pharmacokinetics of oral gemifloxacin in healthy volunteers. Chemotherapy 1999; 45: 496–503.

31.

Allen

Vousden

Porter

Lewis

. Effect of Maalox on the bioavailability of oral gemifloxacin in healthy volunteers. Chemotherapy 1999; 45: 504–11.

32.

Allen

Bygate

Oliver

Johnson

Ward

Cheon

. Pharmacokinetics and tolerability of gemifloxacin (SB-265805) after administration of single oral doses to healthy volunteers. Antimicrob Agents Chemother 2000; 44: 1604–8.

33.

Davy

Allen

Bird

Romain

. Pharmacokinetics and tolerability of gemifloxacin in healthy Japanese and Caucasian volunteers (abstract 2264). In: Programs and abstracts of the 40th Interscience Conference on Antimicrobial Agents and Chemotherapy, Toronto, September 20, 2000.

34.

Lode

Petzold-Bradley

Lubasch

Smith

Lewis

Vousden

. Effect of calcium carbonate on the bioavailability of gemifloxacin in healthy volunteers (abstract 2266). In: Programs and abstracts of the 40th Interscience Conference on Antimicrobial Agents and Chemotherapy, Toronto, September 20, 2000.

35.

National Committee for Clinical Laboratory Standards. Performance standards for antimicrobial susceptibility testing. M100-S10 (M7). Wayne, PA: National Committee for Clinical Laboratory Standards, 2000.

36.

Jones

Erwin

Biedenbach

Johnson

Pfaller

. Development of in vitro susceptibility testing methods for gemifloxacin (formerly LB20304a or SB-265805), an investigational fluoroquinolone. Diagn Microbiol Infect Dis 1999; 35: 227–34.

37.

White

Kays

Friedrich

Del Bene

. Impact of different statistical methodologies on the evaluation of the in-vitro MICs for Bacteroides fragilis of selected cephalosporins and cephamycins. J Antimicrob Chemother 1993; 31: 57–64.

38.

Kays

Wood

Miles

. In vitro activity and pharmacodynamics of oral β-lactam antibiotics against Streptococcus pneumoniae from southeast Missouri. Pharmacotherapy 1999; 19: 1308–14.

39.

Kays

Conklin

. Comparative in vitro activity and pharmacodynamics of five fluoroquinolones against clinical isolates of Streptococcus pneumoniae . Pharmacotherapy 2000; 20: 1310–7.

40.

Gerardo

Citron

Claros

Goldstein

EJC

. Comparison of E-test to broth microdilution for testing Streptococcus pneumoniae susceptibility to levofloxacin and three macrolides. Antimicrob Agents Chemother 1996; 40: 2413–5.

41.

Clark

Jacobs

Appelbaum

. Antipneumococcal activities of levofloxacin and clarithromycin as determined by agar dilution, microdilution, E-test, and disk diffusion methodologies. J Clin Microbiol 1998; 36: 3579–84.

42.

Jones

Johnson

Erwin

Beach

Biedenbach

Pfaller

. Comparative antimicrobial activity of gatifloxacin tested against Streptococcus spp. including quality control guidelines and etest method validation. Diagn Microbiol Infect Dis 1999; 34: 91–8.

43.

Ednie

Jacobs

Appelbaum

. Activity of gemifloxacin, a new broad-spectrum quinolone, against 200 pneumococci by four different susceptibility testing methods. J Antimicrob Chemother 2000; 45: 525–8.