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In vitro synergy of penicillin, ceftriaxone and levofloxacin against serotype 19A Streptococcus pneumoniae
G Model ANTAGE-4651; No. of Pages 4
ARTICLE IN PRESS International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
International Journal of Antimicrobial Agents journal homepage: http://www.elsevier.com/locate/ijantimicag
Letter to the Editor In vitro synergy of penicillin, ceftriaxone and levofloxacin against serotype 19A Streptococcus pneumoniae Sir, Combination therapy with a -lactam (cefotaxime, ceftriaxone or ampicillin/sulbactam) plus a fluoroquinolone is recommended for adult patients who require antibiotic treatment for communityacquired pneumonia in the intensive care unit [1,2]. This recommendation ensures coverage of Streptococcus pneumoniae, Legionella spp. and other Gram-negative bacteria. Several studies have found that combination therapy for patients with bacteraemia due to S. pneumoniae is associated with lower mortality compared with monotherapy [1]. However, it is unclear why this is the case. In this study, two blood isolates (Isolates A and B) of serotype 19A S. pneumoniae that had been recovered from patients treated at National Taiwan University Hospital (Taipei, Taiwan) were selected. Minimum inhibitory concentrations (MICs) of penicillin, ceftriaxone and levofloxacin against these two isolates were determined by the broth microdilution method. MICs against Isolate A (penicillin-susceptible) were 0.12 mg/L for penicillin, 0.06 mg/L for ceftriaxone and 1 mg/L for levofloxacin, and against Isolate B (penicillin-non-susceptible) were 4 mg/L for penicillin, 1 mg/L for ceftriaxone and 1 mg/L for levofloxacin. Time–kill studies of the activity of these antimicrobial agents against the two S. pneumoniae isolates were performed as previously described [3,4]. Each agent was tested individually and in combination with one of the other agents, namely penicillin + ceftriaxone, penicillin + levofloxacin, and ceftriaxone + levofloxacin. Synergy was defined as a >2 log10 decrease in CFU/mL compared with the most active agent alone. Additive and indifferent effects were defined as a reduction of between 1–2-log10 CFU/mL and of ±1 log10 CFU/mL, respectively, compared with the most active single antibiotic [3]. Killing curves of the different combinations are shown in Figs. 1 and 2.
For the penicillin-susceptible S. pneumoniae isolate (Isolate A), penicillin + ceftriaxone at 1× MIC showed an indifferent effect at 8 h and an additive effect at 24 h (Fig. 1A). Combination of penicillin + levofloxacin at 1× MIC of each agent resulted in an additive effect at 8 h and synergism at 24 h (Fig. 1B). Both penicillin-based combinations (either with ceftriaxone or levofloxacin) eradicated bacterial growth at 24 h after inoculation. Ceftriaxone + levofloxacin at 1× MIC of each agent had an additive effect at 8 h and a synergistic effect at 24 h (Fig. 1C). For the penicillin-non-susceptible S. pneumoniae isolate (Isolate B), penicillin-based combinations, either with ceftriaxone or levofloxacin at 1× MIC of the tested agents, showed synergism at 24 h after inoculation (no colonies were visible after 24 h of incubation) (Fig. 2A and B). Ceftriaxone plus levofloxacin at 1× MIC of the tested agents resulted in an additive effect at 8 h and synergism at 24 h (Fig. 2C). The in vitro and in vivo synergism of third-generation cephalosporins and fluoroquinolones against penicillin-nonsusceptible S. pneumoniae has been reported previously [5]. The different targets of third-generation cephalosporins and fluoroquinolones may contribute to the synergism of this combination. However, we found that penicillin and third-generation cephalosporins act synergistically even though both drugs target similar penicillin-binding proteins [3]. The reason for this is unclear. To the best of our knowledge, this is the first study to investigate the synergistic activity of penicillin-based combinations. We found that ceftriaxone + levofloxacin, penicillin + ceftriaxone, and penicillin + levofloxacin are suitable for treating severe infections caused by pneumococci even when the isolates are not susceptible to penicillin. Further studies are needed to investigate the clinical efficacy of penicillin-based combinations in treating pneumococcal infections. Funding: None. Competing interests: None declared. Ethical approval: Not required.
http://dx.doi.org/10.1016/j.ijantimicag.2015.07.018 0924-8579/© 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
Please cite this article in press as: Tsai H-Y, et al. In vitro synergy of penicillin, ceftriaxone and levofloxacin against serotype 19A Streptococcus pneumoniae. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.07.018
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ARTICLE IN PRESS Letter to the Editor / International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
Fig. 1. Time–kill curves of different combinations of antimicrobial agents against penicillin-susceptible Streptococcus pneumoniae (Isolate A) with penicillin, ceftriaxone and levofloxacin minimum inhibitory concentrations (MICs) of 0.12, 0.06 and 1 mg/L, respectively: (A) penicillin + ceftriaxone; (B) penicillin + levofloxacin; and (C) ceftriaxone + levofloxacin. QC, quality control (bacterial growth in the absence of any antimicrobial agents).
Please cite this article in press as: Tsai H-Y, et al. In vitro synergy of penicillin, ceftriaxone and levofloxacin against serotype 19A Streptococcus pneumoniae. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.07.018
G Model ANTAGE-4651; No. of Pages 4
ARTICLE IN PRESS Letter to the Editor / International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
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Fig. 2. Time–kill curves of different combinations of antimicrobial agents against penicillin-resistant Streptococcus pneumoniae (Isolate B) with penicillin, ceftriaxone and levofloxacin minimum inhibitory concentrations (MICs) of 4, 1 and 1 mg/L, respectively: (A) penicillin + ceftriaxone; (B) penicillin + levofloxacin; and (C) ceftriaxone + levofloxacin. QC, quality control (bacterial growth in the absence of any antimicrobial agents).
Please cite this article in press as: Tsai H-Y, et al. In vitro synergy of penicillin, ceftriaxone and levofloxacin against serotype 19A Streptococcus pneumoniae. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.07.018
G Model ANTAGE-4651; No. of Pages 4
ARTICLE IN PRESS Letter to the Editor / International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
4
References
Po-Ren Hsueh a,b,∗∗ Department of Internal Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan b Department of Laboratory Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan a
[1] Mandell LA, Wunderink RG, Anzueto A, Bartlett JG, Campbell GD, Dean NC, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis 2007;44(Suppl. 2):S27–72. [2] Infectious Diseases Society of Taiwan, Taiwan Society of Pulmonary and Critical Medicine, Medical Foundation in Memory of Dr. Deh-Lin Cheng, Foundation of Professor Wei-Chuan Hsieh for Infectious Diseases Research and Education, CY Lee’s Research Foundation for Pediatric Infectious Diseases and Vaccines. Guidelines on antimicrobial therapy of pneumonia in adults in Taiwan, revised 2006. J Microbiol Immunol Infect 2007;40:279–83. [3] Liao CH, Huang YT, Tsai HY, Hsueh PR. In vitro synergy of ampicillin with gentamicin, ceftriaxone and ciprofloxacin against Enterococcus faecalis. Int J Antimicrob Agents 2014;44:85–6. [4] Cheng A, Sheng WH, Liou JM, Wang HP, Wu MS, Lin JT, et al. Comparative in vitro antimicrobial susceptibility and synergistic activity of antimicrobial combinations against Helicobacter pylori isolates in Taiwan. J Microbiol Immunol Infect 2015;48:72–9. [5] Flatz L, Cottagnoud M, Kühn F, Entenza J, Stucki A, Cottagnoud P. Ceftriaxone acts synergistically with levofloxacin in experimental meningitis and reduces levofloxacin-induced resistance in penicillin-resistant pneumococci. J Antimicrob Chemother 2004;53:305–10.
Hsih-Yeh Tsai Chun-Hsing Liao ∗ Chia-Ying Liu Yu-Tsung Huang Department of Internal Medicine, Far Eastern Memorial Hospital, New Taipei City, Taiwan
∗ Corresponding
author. Tel.: +886 2 2312 3456x65355; fax: +886 2 2322 4263.
∗∗ Corresponding author at: Department of Laboratory Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan. Tel.: +886 2 2312 3456x65355; fax: +886 2 2322 4263. E-mail addresses: [email protected] (C.-H. Liao), [email protected] (P.-R. Hsueh).
24 July 2015
Please cite this article in press as: Tsai H-Y, et al. In vitro synergy of penicillin, ceftriaxone and levofloxacin against serotype 19A Streptococcus pneumoniae. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.07.018
ARTICLE IN PRESS International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
International Journal of Antimicrobial Agents journal homepage: http://www.elsevier.com/locate/ijantimicag
Letter to the Editor In vitro synergy of penicillin, ceftriaxone and levofloxacin against serotype 19A Streptococcus pneumoniae Sir, Combination therapy with a -lactam (cefotaxime, ceftriaxone or ampicillin/sulbactam) plus a fluoroquinolone is recommended for adult patients who require antibiotic treatment for communityacquired pneumonia in the intensive care unit [1,2]. This recommendation ensures coverage of Streptococcus pneumoniae, Legionella spp. and other Gram-negative bacteria. Several studies have found that combination therapy for patients with bacteraemia due to S. pneumoniae is associated with lower mortality compared with monotherapy [1]. However, it is unclear why this is the case. In this study, two blood isolates (Isolates A and B) of serotype 19A S. pneumoniae that had been recovered from patients treated at National Taiwan University Hospital (Taipei, Taiwan) were selected. Minimum inhibitory concentrations (MICs) of penicillin, ceftriaxone and levofloxacin against these two isolates were determined by the broth microdilution method. MICs against Isolate A (penicillin-susceptible) were 0.12 mg/L for penicillin, 0.06 mg/L for ceftriaxone and 1 mg/L for levofloxacin, and against Isolate B (penicillin-non-susceptible) were 4 mg/L for penicillin, 1 mg/L for ceftriaxone and 1 mg/L for levofloxacin. Time–kill studies of the activity of these antimicrobial agents against the two S. pneumoniae isolates were performed as previously described [3,4]. Each agent was tested individually and in combination with one of the other agents, namely penicillin + ceftriaxone, penicillin + levofloxacin, and ceftriaxone + levofloxacin. Synergy was defined as a >2 log10 decrease in CFU/mL compared with the most active agent alone. Additive and indifferent effects were defined as a reduction of between 1–2-log10 CFU/mL and of ±1 log10 CFU/mL, respectively, compared with the most active single antibiotic [3]. Killing curves of the different combinations are shown in Figs. 1 and 2.
For the penicillin-susceptible S. pneumoniae isolate (Isolate A), penicillin + ceftriaxone at 1× MIC showed an indifferent effect at 8 h and an additive effect at 24 h (Fig. 1A). Combination of penicillin + levofloxacin at 1× MIC of each agent resulted in an additive effect at 8 h and synergism at 24 h (Fig. 1B). Both penicillin-based combinations (either with ceftriaxone or levofloxacin) eradicated bacterial growth at 24 h after inoculation. Ceftriaxone + levofloxacin at 1× MIC of each agent had an additive effect at 8 h and a synergistic effect at 24 h (Fig. 1C). For the penicillin-non-susceptible S. pneumoniae isolate (Isolate B), penicillin-based combinations, either with ceftriaxone or levofloxacin at 1× MIC of the tested agents, showed synergism at 24 h after inoculation (no colonies were visible after 24 h of incubation) (Fig. 2A and B). Ceftriaxone plus levofloxacin at 1× MIC of the tested agents resulted in an additive effect at 8 h and synergism at 24 h (Fig. 2C). The in vitro and in vivo synergism of third-generation cephalosporins and fluoroquinolones against penicillin-nonsusceptible S. pneumoniae has been reported previously [5]. The different targets of third-generation cephalosporins and fluoroquinolones may contribute to the synergism of this combination. However, we found that penicillin and third-generation cephalosporins act synergistically even though both drugs target similar penicillin-binding proteins [3]. The reason for this is unclear. To the best of our knowledge, this is the first study to investigate the synergistic activity of penicillin-based combinations. We found that ceftriaxone + levofloxacin, penicillin + ceftriaxone, and penicillin + levofloxacin are suitable for treating severe infections caused by pneumococci even when the isolates are not susceptible to penicillin. Further studies are needed to investigate the clinical efficacy of penicillin-based combinations in treating pneumococcal infections. Funding: None. Competing interests: None declared. Ethical approval: Not required.
http://dx.doi.org/10.1016/j.ijantimicag.2015.07.018 0924-8579/© 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
Please cite this article in press as: Tsai H-Y, et al. In vitro synergy of penicillin, ceftriaxone and levofloxacin against serotype 19A Streptococcus pneumoniae. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.07.018
G Model ANTAGE-4651; No. of Pages 4 2
ARTICLE IN PRESS Letter to the Editor / International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
Fig. 1. Time–kill curves of different combinations of antimicrobial agents against penicillin-susceptible Streptococcus pneumoniae (Isolate A) with penicillin, ceftriaxone and levofloxacin minimum inhibitory concentrations (MICs) of 0.12, 0.06 and 1 mg/L, respectively: (A) penicillin + ceftriaxone; (B) penicillin + levofloxacin; and (C) ceftriaxone + levofloxacin. QC, quality control (bacterial growth in the absence of any antimicrobial agents).
Please cite this article in press as: Tsai H-Y, et al. In vitro synergy of penicillin, ceftriaxone and levofloxacin against serotype 19A Streptococcus pneumoniae. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.07.018
G Model ANTAGE-4651; No. of Pages 4
ARTICLE IN PRESS Letter to the Editor / International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
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Fig. 2. Time–kill curves of different combinations of antimicrobial agents against penicillin-resistant Streptococcus pneumoniae (Isolate B) with penicillin, ceftriaxone and levofloxacin minimum inhibitory concentrations (MICs) of 4, 1 and 1 mg/L, respectively: (A) penicillin + ceftriaxone; (B) penicillin + levofloxacin; and (C) ceftriaxone + levofloxacin. QC, quality control (bacterial growth in the absence of any antimicrobial agents).
Please cite this article in press as: Tsai H-Y, et al. In vitro synergy of penicillin, ceftriaxone and levofloxacin against serotype 19A Streptococcus pneumoniae. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.07.018
G Model ANTAGE-4651; No. of Pages 4
ARTICLE IN PRESS Letter to the Editor / International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
4
References
Po-Ren Hsueh a,b,∗∗ Department of Internal Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan b Department of Laboratory Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan a
[1] Mandell LA, Wunderink RG, Anzueto A, Bartlett JG, Campbell GD, Dean NC, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis 2007;44(Suppl. 2):S27–72. [2] Infectious Diseases Society of Taiwan, Taiwan Society of Pulmonary and Critical Medicine, Medical Foundation in Memory of Dr. Deh-Lin Cheng, Foundation of Professor Wei-Chuan Hsieh for Infectious Diseases Research and Education, CY Lee’s Research Foundation for Pediatric Infectious Diseases and Vaccines. Guidelines on antimicrobial therapy of pneumonia in adults in Taiwan, revised 2006. J Microbiol Immunol Infect 2007;40:279–83. [3] Liao CH, Huang YT, Tsai HY, Hsueh PR. In vitro synergy of ampicillin with gentamicin, ceftriaxone and ciprofloxacin against Enterococcus faecalis. Int J Antimicrob Agents 2014;44:85–6. [4] Cheng A, Sheng WH, Liou JM, Wang HP, Wu MS, Lin JT, et al. Comparative in vitro antimicrobial susceptibility and synergistic activity of antimicrobial combinations against Helicobacter pylori isolates in Taiwan. J Microbiol Immunol Infect 2015;48:72–9. [5] Flatz L, Cottagnoud M, Kühn F, Entenza J, Stucki A, Cottagnoud P. Ceftriaxone acts synergistically with levofloxacin in experimental meningitis and reduces levofloxacin-induced resistance in penicillin-resistant pneumococci. J Antimicrob Chemother 2004;53:305–10.
Hsih-Yeh Tsai Chun-Hsing Liao ∗ Chia-Ying Liu Yu-Tsung Huang Department of Internal Medicine, Far Eastern Memorial Hospital, New Taipei City, Taiwan
∗ Corresponding
author. Tel.: +886 2 2312 3456x65355; fax: +886 2 2322 4263.
∗∗ Corresponding author at: Department of Laboratory Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan. Tel.: +886 2 2312 3456x65355; fax: +886 2 2322 4263. E-mail addresses: [email protected] (C.-H. Liao), [email protected] (P.-R. Hsueh).
24 July 2015
Please cite this article in press as: Tsai H-Y, et al. In vitro synergy of penicillin, ceftriaxone and levofloxacin against serotype 19A Streptococcus pneumoniae. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.07.018