JAC Advance Access originally published online on January 14, 2003
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Journal of Antimicrobial Chemotherapy (2003) 51, 443-446
© 2003 The British Society for Antimicrobial Chemotherapy
Bactericidal activity of daptomycin against Streptococcus pneumoniae compared with eight other antimicrobials
1 Department of Pathology, Hershey Medical Center, PO Box 850, Hershey, PA 17033; 2 Case Western Reserve University, Cleveland, OH 44106, USA
Received 13 September 2002; returned 7 November 2002; revised 7 November 2002; accepted 19 November 2002
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Abstract |
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A spectrum of pneumococci with varying susceptibilities to ß-lactams, macrolides and quinolones was tested for susceptibility to nine antibiotics, including the novel lipopeptide daptomycin. Daptomycin was active against all strains (MIC range
0.5 mg/L; MIC50 0.125 mg/L; MIC90 0.25 mg/L). All pneumococci were susceptible to vancomycin, teicoplanin, linezolid and quinupristin/dalfopristin, with MICs < 4.0 mg/L. Time–kill assays with eight strains demonstrated that daptomycin (2 x MIC) was bactericidal in seven of eight strains tested at 24 h, with >90% killing at 1 h. Keywords: pneumococci, daptomycin, MIC, time–kill
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Introduction |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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The prevalence of Streptococcus pneumoniae resistant to penicillin G and other antibiotics has increased worldwide at an alarming rate.1,2 Antibiotic resistance is a significant concern in the USA. For example, a recent survey has shown that 50.4% of 1476 clinically significant pneumococcal isolates were not susceptible to penicillin.2 Furthermore, macrolide resistance was detected in 33% of the isolates, including 5% of penicillin-susceptible, 37% of penicillin-intermediate and 66% of penicillin-resistant strains.2 Quinolone-resistant pneumococcal strains have also been reported with increasing frequency, particularly in Hong Kong and Canada.3
Because of this worldwide increase in antibiotic resistance, there is a significant need for additional antimicrobial agents to treat infections caused by penicillin-intermediate and penicillin-resistant pneumococci.1,2 Although therapeutic modalities such as ß-lactams, macrolides and quinolones are currently available, in view of the increasing resistance described above, an agent with a unique mechanism of action compared with these three antibiotic classes is desirable.
Daptomycin is a novel lipopeptide that exhibits rapid in vitro concentration-dependent bactericidal activity against most clinically significant Gram-positive bacteria.4–6 Daptomycin is active against antibiotic-susceptible and -resistant strains, including methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci and antibiotic-resistant pneumococci. The mode of action of daptomycin is unique; it is believed to kill Gram-positive bacteria by disrupting multiple aspects of bacterial plasma membrane function without penetrating into the cytoplasm.4,6
This study was designed to test the activity of daptomycin compared with that of amoxicillin, erythromycin, levofloxacin, linezolid, quinupristin/dalfopristin, penicillin G, teicoplanin and vancomycin against pneumococci using microdilution and time–kill methodologies.
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Materials and methods |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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For MIC analysis, 346 strains of S. pneumoniae were tested. Of the 346 strains, 159 were penicillin susceptible (MICs < 0.06 mg/L), 86 were penicillin intermediate (MICs 0.125–1.0 mg/L) and 101 were penicillin resistant (MICs > 2.0 mg/L). Additionally, 207 strains were also erythromycin resistant (MICs > 1.0 mg/L) and 30 were levofloxacin resistant (MICs > 4.0 mg/L). Daptomycin was provided by Cubist Pharmaceuticals, Inc. (Lexington, MA, USA) and the other antimicrobials were obtained from their respective companies, or in the case of penicillin G, from Sigma, Inc. (St Louis, MO, USA). Determination of MIC was carried out using microdilution techniques recommended by the NCCLS.7 Mueller–Hinton broth was adjusted to contain 50 mg of calcium per litre for testing daptomycin.4 Previous studies4 have documented that the in vitro activity of daptomycin is enhanced by increased calcium concentrations, and that MICs thus obtained correlated well with favourable clinical outcome.6 This calcium effect is not observed with other agent classes.7 The initial calcium concentration in Mueller–Hinton broth was measured by Inductively Coupled Plasma Atomic Spectrometry (ICP), using model 61E ICP (Thermo Jarrell Ash Corporation, Franklin, MA, USA). Frozen microtitre trays containing appropriate concentrations of antibiotics were prepared by TREK Diagnostic Systems, Inc. (Westlake, OH, USA) and frozen at –70°C until use. Standard quality control strains,7 including S. pneumoniae ATCC 49619, were included in each experiment.
Time–kill activities were measured in duplicate, as described previously, for eight pneumococcal strains: two were penicillin susceptible and six penicillin resistant (of which three were erythromycin resistant and two levofloxacin resistant).8 Mueller–Hinton broth was supplemented as described above, and antibiotic concentrations chosen were 4 x and 2 x MIC, and the MIC for each strain. Growth controls were included in each experiment.8 The initial inoculum for each strain was within the range of 5 x 105 to 5 x 106 cfu/mL. Viability counts of antibiotic-containing cultures were carried out at 0, 1, 6, 12 and 24 h, as described previously.8 Colony counts were carried out on plates yielding 30–300 bacterial colonies. The upper limit of sensitivity of colony counts was 300 cfu/mL.8
Time–kill assays were analysed by determining the number of strains yielding a 
log10 cfu/mL of –1 (90% killing), –2 (99% killing) and –3 (99.9% killing) at 1, 6, 12 and 24 h, compared with counts at 0 h. Results are means of two assays. Bactericidal activity was defined as the lowest antibiotic concentration that reduced the original inoculum by 
3 log10 cfu/mL (99.9%) at each time period, and bacteriostatic activity was defined as a reduction of <3 log10 cfu/mL in the inoculum concentration.8 For time–kill testing with erythromycin, only strains with an erythromycin MIC of 1.0 mg/L were tested. Additionally, two strains with a levofloxacin MIC of 16 mg/L were excluded from levofloxacin time–kill assays.
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Results |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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Results of MIC testing for the nine antibiotics against the 346 pneumococcal strains are presented in Table 1. Daptomycin, linezolid, vancomycin, teicoplanin and quinupristin/dalfopristin were active against all strains tested irrespective of the strains’ susceptibility to ß-lactams, macrolides or quinolones. Teicoplanin yielded the lowest MIC50 and MIC90, followed by daptomycin, vancomycin, quinupristin/dalfopristin and linezolid, respectively. The MIC50s and MIC90s of amoxicillin, erythromycin and penicillin G were higher and increased for penicillin-susceptible, -intermediate and -resistant strains. Additionally, levofloxacin was active against the 316 quinolone-susceptible strains, with an MIC50 of 1.0 mg/L and an MIC90 of 2.0 mg/L.
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The daptomycin MICs for the eight pneumococcal strains tested in the time–kill assays were similar to those listed in Table 1 and were 0.125 mg/L (three strains), 0.25 mg/L (two strains) and 0.5 mg/L (three strains). Of these, two strains were penicillin susceptible and six were penicillin resistant. Results of the time–kill studies are summarized in Table 2. Results are means of two assays. Daptomycin at 2 x MIC was bactericidal against seven of eight strains after 24 h, and at 4 x MIC was bactericidal against all eight strains tested. Significant bacterial killing was observed early, with 90% killing in the seven strains after 1 h of incubation with daptomycin at 2 x or 4 x MIC. In comparison, only quinupristin/dalfopristin killed bacteria with similar rapidity after 1 h. Vancomycin, teicoplanin, levofloxacin and amoxicillin were bactericidal against 6–8 strains at 2 x MIC after 24 h. However, the rate of killing was slower compared with that of daptomycin. In addition, linezolid and erythromycin exhibited poor bactericidal activity compared with all the other agents tested, with bactericidal activity observed in only five of eight strains at 4 x MIC for both agents.
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Discussion |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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In this study, the in vitro activity of daptomycin against pneumococci, measured by MIC determination and time–kill assays, was similar to results described previously.4–6 Comparative activities of other agents active against Gram-positive organisms such as vancomycin, linezolid and quinupristin/dalfopristin were similar to previous findings.9,10 Interestingly, compared with other antimicrobial agents predominantly active against Gram-positive organisms, daptomycin demonstrated very rapid kill kinetics, with significant killing of pneumococcal strains observed as early as 1 h after antibiotic exposure. In this study, only quinupristin/dalfopristin had comparable bactericidal activity.8
This study supports a possible role for daptomycin in treating infections caused by antibiotic-susceptible and -resistant pneumococci, irrespective of the susceptibility of the given strain to ß-lactams, macrolides or quinolones. Further studies are warranted on the bactericidal activity of daptomycin against S. pneumoniae, including relationship of kill kinetics with protein binding and pharmacokinetic/pharmacodynamic properties.
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Acknowledgements |
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This study was supported by a grant from Cubist Pharmaceuticals, Inc. (Lexington, MA, USA).
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Footnotes |
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* Corresponding author. Tel: +1-717-531-5113; Fax: +1-717-531-7953; E-mail: pappelbaum{at}psu.edu
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References |
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1 . Friedland, I. R. & McCracken, G. H., Jr (1994). Management of infections caused by antibiotic-resistant Streptococcus pneumoniae. New England Journal of Medicine 331, 377–82.
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Jacobs, M. R., Bajaksouzian, S., Zilles, A., Lin, G., Pankuch, G. A. & Appelbaum, P. C. (1999). Susceptibilities of Streptococcus pneumoniae and Haemophilus influenzae to 10 oral antimicrobial agents based on pharmacodynamic parameters: 1997 US surveillance study. Antimicrobial Agents and Chemotherapy 43, 1901–8.
3
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Chen, D. K., McGeer, A., de Azavedo, J. C. & Low, D. E. (1999). Decreased susceptibility of Streptococcus pneumoniae to fluoroquinolones in Canada. New England Journal of Medicine 341, 233–9.
4 . Fuchs, P. C., Barry, A. L. & Brown, S. D. (2000). Daptomycin susceptibility tests: interpretive criteria, quality control, and effect of calcium on in vitro tests. Diagnostic Microbiology and Infectious Disease 38, 51–8.[CrossRef][ISI][Medline]
5
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King, A. & Phillips, I. (2001). The in vitro activity of daptomycin against 514 Gram-positive aerobic clinical isolates. Journal of Antimicrobial Chemotherapy 48, 219–23.
6
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Tally, F. P. & DeBruin, M. F. (2000). Development of daptomycin for Gram-positive infections. Journal of Antimicrobial Chemotherapy 46, 523–6.
7 . National Committee for Clinical Laboratory Standards. (1997). Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically—Fifth Edition: Approved Standard M7-A5. NCCLS, Wayne, PA, USA.
8 . Pankuch, G. A., Lichtenberger, C., Jacobs, M. R. & Appelbaum, P. C. (1996). Antipneumococcal activities of RP 59500 (quinupristin/dalfopristin), penicillin G, erythromycin, and sparfloxacin determined by MIC and rapid time–kill methodologies. Antimicrobial Agents and Chemotherapy 40, 1653–6.[Abstract]
9
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Henwood, C. J., Livermore, D. M., Johnson, A. P., James, D., Warner, M., Gardiner, A. et al. (2000). Susceptibility of Gram-positive cocci from 25 UK hospitals to antimicrobial agents including linezolid. Journal of Antimicrobial Chemotherapy 46, 931–40.
10
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Livermore, D. M. (2000). Quinupristin/dalfopristin and linezolid: where, when, which and whether to use? Journal of Antimicrobial Chemotherapy 46, 347–50.
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