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Effect of dexamethasone on the efficacy of daptomycin in the therapy of experimental pneumococcal meningitis M. Vivas a,∗ , E. Force a , F. Tubau b , C. El Haj a , J. Ariza a , C. Cabellos a a Laboratory of Experimental Infection, Infectious Diseases Department, IDIBELL-Hospital Universitari de Bellvitge, Feixa Llarga s/n, 08907 L’Hospitalet de Llobregat, Barcelona, Spain b Microbiology Department, IDIBELL-Hospital Universitari de Bellvitge and CIBERES ISCIII, Feixa Llarga s/n, 08907 L’Hospitalet de Llobregat, Barcelona, Spain
a r t i c l e
i n f o
Article history: Received 10 October 2014 Accepted 28 January 2015 Keywords: Steroids Lipopeptide CNS infection Streptococcus pneumoniae
a b s t r a c t This study aimed to determine the effect of dexamethasone in combination with low-dose or highdose daptomycin for the treatment of penicillin- and cephalosporin-resistant pneumococcal meningitis. Efficacy (CFU/mL) and cerebrospinal fluid (CSF) levels of daptomycin at 15 mg/kg and 25 mg/kg were studied in a rabbit model of pneumococcal meningitis, comparing them with the same doses in combination with dexamethasone at 0.125 mg/kg every 12 h over a 26-h period against two different Streptococcus pneumoniae strains, HUB 2349 and ATCC 51916 with daptomycin minimum inhibitory concentrations (MICs) of 0.09 mg/L and 0.19 mg/L, respectively. Daptomycin levels in CSF were lower when dexamethasone was given concurrently. Against strain HUB 2349, therapeutic failure occurred with daptomycin 15 mg/kg + dexamethasone; daptomycin 25 mg/kg + dexamethasone was better at reducing bacterial counts than the lower dose throughout treatment. Against the highly cephalosporin-resistant ATCC 51916 strain, daptomycin 15 mg/kg + dexamethasone achieved a lower bacterial decrease than daptomycin 15 mg/kg alone, and therapeutic failure at 24 h occurred in the daptomycin 15 mg/kg + dexamethasone group. Addition of dexamethasone to a 25 mg/kg daptomycin dose did not affect the efficacy of daptomycin: it remained bactericidal throughout treatment. In conclusion, against the studied strains, low-dose (15 mg/kg/day) daptomycin is affected by concomitant use of dexamethasone: CSF levels are reduced and its bacterial efficacy is affected. At a higher daptomycin dose (25 mg/kg/day), however, the use of dexamethasone does not alter efficacy; the combination appears to be a good choice for the treatment of pneumococcal meningitis. © 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
1. Introduction Despite the efficacy of antibiotic therapy, the mortality rate of bacterial meningitis is still significant, ranging between 10% and 30% [1], and >30% of survivors develop long-term sequelae including hearing loss and neurological deficits [2]. The rapid bactericidal action of daptomycin makes it an attractive alternative for the treatment of multidrug-resistant pneumococcal meningitis. In addition, its non-bacteriolytic activity may represent an advantage even in cases of full -lactam susceptibility. Adjunctive treatment with corticosteroids has been recommended to decrease the inflammation and mortality in bacterial meningitis. Several clinical studies have demonstrated that
∗ Corresponding author. Tel.: +34 932 607 625/934 035 805; fax: +34 932 607 637. E-mail address: [email protected] (M. Vivas).
dexamethasone is beneficial in the treatment of the condition, reducing mortality and improving the prognosis [1], but concomitant use of dexamethasone in combination with antibiotic therapy is still controversial [3]. Diverse clinical trials have demonstrated that adjunctive therapy with dexamethasone reduced severe hearing loss in children and reduced the risk of death and non-favourable sequelae in adults with bacterial meningitis [4,5]. However, it is well known that concomitant use of dexamethasone affects antibiotic penetration into the cerebrospinal fluid (CSF) across the blood–brain barrier and may be associated with failure of antibiotic therapy [6]. Two clinical studies showed that dexamethasone could affect the efficacy of vancomycin for the treatment of pneumococcal meningitis depending on the antibiotic concentrations in the CSF [7,8]. The interaction between dexamethasone and different antibiotics has been widely studied in experimental meningitis models. Syrogiannopoulos et al. assessed the effect of dexamethasone in
http://dx.doi.org/10.1016/j.ijantimicag.2015.01.014 0924-8579/© 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
Please cite this article in press as: Vivas M, et al. Effect of dexamethasone on the efficacy of daptomycin in the therapy of experimental pneumococcal meningitis. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.01.014
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combination with ceftriaxone. CSF antibiotic levels were lower when dexamethasone was added and they found no differences in inflammation parameters [9]. Another experimental study by our group demonstrated that the use of dexamethasone resulted in therapeutic failure and a substantial decrease in ceftriaxone levels in the CSF, even at high ceftriaxone doses, in a cephalosporin-resistant strain of Streptococcus pneumoniae [10]. Addition of dexamethasone had a beneficial effect on the inflammatory response in an experimental study using rifampicin, rifampicin plus vancomycin, and ceftriaxone plus rifampicin and did not significantly interfere with antibiotic levels in the CSF [11,12]. Demonstrating that the efficacy of antibiotic therapy is not affected by concomitant use of dexamethasone is a matter of necessity, since the use of dexamethasone may represent a useful adjunctive therapy in cases of pneumococcal meningitis. In an experimental animal model, we recently reported [13] that daptomycin may represent a good alternative for the treatment of penicillin- and cephalosporin-resistant strains of S. pneumoniae owing to its ability to sterilise CSF samples from the very beginning of treatment. The aim of this study was to test the effect of dexamethasone as standard adjunctive therapy given in combination with low-dose or high-dose daptomycin on the treatment of penicillin- and cephalosporin-resistant strains of S. pneumoniae in an experimental meningitis model.
2. Materials and methods 2.1. Bacterial strains Two different strains of S. pneumoniae isolated from patients with meningitis were used: strain HUB 2349 is penicillinand cephalosporin-resistant; and the ATCC 51916 strain (Tennessee 23F-4 clone) is intermediately penicillin-resistant and highly cephalosporin-resistant. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations, respectively, were as follows: for strain HUB 2349, penicillin, 4 mg/L and 4 mg/L; ceftriaxone/cefotaxime, 2 mg/L and 4 mg/L; vancomycin, 0.25 mg/L and 0.25 mg/L; and daptomycin, 0.09 mg/L and 0.18 mg/L; and for the ATCC 51916 strain, penicillin, 0.12 mg/L and 0.25 mg/L; ceftriaxone/cefotaxime, 32 mg/L and 32 mg/L; vancomycin, 0.25 mg/L and 0.25 mg/L; and daptomycin, 0.19 mg/L and 0.38 mg/L.
Animals were placed in a stereotactic frame and a baseline CSF sample was taken (0 h). A dose of dexamethasone (Fortecortin® ; Merck, Barcelona, Spain) of 0.25 mg/24 h divided every 12 h (q12h) was given intravenously. Then, 10 min later antibiotic therapy was administered. CSF samples were taken after 2, 6, 24 and 26 h of therapy. Hydration was ensured throughout the experiment. Mortality was assessed at 26 h. Surviving animals were euthanised using a lethal dose of thiopental sodium at the end of each experiment.
2.2.2. Therapeutic groups Intravenous antibiotic therapy was then administered for 26 h using one of the following therapy schedules: daptomycin at 15 mg/kg (n = 8 rabbits for each strain) given once daily; daptomycin 15 mg/kg given once daily plus dexamethasone (n = 9 rabbits for each strain) at 0.125 mg/kg q12h; daptomycin at 25 mg/kg (n = 9 rabbits for each strain) given once daily; and daptomycin 25 mg/kg given once daily plus dexamethasone (n = 10 rabbits for each strain) at 0.125 mg/kg q12h. Untreated control rabbits received saline. Part of the results have already been described in our previous study [13].
2.3. Sample processing CSF samples were used to determine CSF white blood cell (WBC) counts, bacterial counts and antibiotic levels at peak and trough time points. For leukocyte counts, 10 L of each sample was diluted 1:1 with Turk solution and read with a Neubauer chamber. Animals presenting ≥300 cells/mm3 were included in the study groups. Serial ten-fold dilutions were made to determine bacterial counts at each time point. To avoid interference due to carryover of antimicrobial agent, an entire agar plate was used for each sample. The lowest bacterial concentration detectable was 10 CFU/mL. For the purpose of analysis, a value of 0.99 log CFU/mL was assigned to the first sterile culture, and a value of 0 log CFU/mL to subsequent ones. Changes in bacterial counts (log CFU/mL) were calculated as the difference between bacterial concentrations at the start of therapy and at 2, 6, 24 and 26 h. Therapeutic failure was defined as an increase in bacterial concentration of ≥1 log CFU/mL compared with a previous count. A therapy was considered bactericidal when a reduction of 3 log CFU/mL was achieved. Samples were centrifuged at 5000 × g for 10 min and the supernatants were stored at −70 ◦ C.
2.2. In vivo studies
2.4. Antibiotic assays
2.2.1. Meningitis model The rabbit model of meningitis originally described by Dacey and Sande [14] was used with slight modifications. Young female New Zealand White rabbits were anaesthetised intramuscularly with 35 mg/kg ketamine (Ketolar® ; Parke-Davis, Prat de Llobregat, Spain) and 5 mg/kg xylazine (Rompun® ; Bayer AG, Leverkusen, Germany). Meningitis was induced with an intracisternal injection of 250 L of a saline suspension containing 106 CFU/mL of inoculum. In rabbits infected with the HUB 2349 strain, therapy was started 18 h post-inoculation. In animals infected with the ATCC 51916 strain, therapy was initiated 40 h post-inoculation owing to the slow progression of meningitis [15]. Rabbits were anaesthetised using urethane (Sigma Chemical Co., St Louis, MO) at 1.75 g/kg subcutaneously and thiopental sodium (Tiopental® ; B. Braun Medical S.A., Rubí, Spain) at 5 mg/kg intravenously. A blood sample was collected to assess secondary bacteraemia.
Daptomycin concentrations were measured using the agar disk diffusion method [16] using Micrococcus luteus ATCC 9341 [linearity of assay (r2 ) = 0.99; lower detection limit, 2 g/mL] as the assay organism.
2.5. Statistical analysis All bacterial counts are presented as log numbers of CFU per millilitre (mean ± standard deviation). Differences in bacterial counts between treated and untreated animals were evaluated for statistical significance using analysis of variance (ANOVA). An unpaired Student’s t-test with Bonferroni correction was used to determine statistical significance. WBC counts were compared using the non-parametric Mann–Whitney and Wilcoxon tests. For all tests, differences were considered to be statistically significant when P-values were 1 log CFU/mL from the previous counts.
0.72 ± 0.82*,**,†
0.62 ± 0.25*,**,†
5.15 ± 0.82
0.08 ± 0.38**,†
3.2.2. ATCC 51916 strain Secondary bacteraemia at 0 h was 100%. Mortality at 26 h was 50% in the control group, 11.1% for daptomycin 15 mg/kg, 25% for daptomycin 15 mg/kg + dexamethasone, 0% for daptomycin 25 mg/kg and 14.3% for daptomycin 25 mg/kg + dexamethasone. There were no significance between therapeutic groups. The CSF of infected rabbits showed inflammation in terms of high WBC counts throughout the experiment. CSF WBC counts at 0 h and 24 h did not differ significantly between the therapy groups. The two doses of daptomycin with and without dexamethasone were significantly better than the control group throughout the treatment. Daptomycin 15 mg/kg + dexamethasone presented a bacterial decrease at each point of the experiment, being significantly lower than daptomycin 15 mg/kg alone and daptomycin 25 mg/kg + dexamethasone at 24 h and 26 h. Therapeutic failures at 24 h occurred in 57% of the daptomycin 15 mg/kg + dexamethasone group versus 25% of the daptomycin 15 mg/kg group. Addition of dexamethasone to the 25 mg/kg daptomycin dose did not affect the efficacy of daptomycin, which was bactericidal throughout the treatment. No therapeutic failure occurred with daptomycin 25 mg/kg either alone or with dexamethasone. 4. Discussion
†
**
*
a
Data are expressed as the mean ± standard deviation. P ≤ 0.05 vs. daptomycin 15 mg/kg + dexamethasone. P ≤ 0.05 vs. daptomycin 25 mg/kg + dexamethasone. P ≤ 0.05 vs. daptomycin 15 mg/kg and daptomycin 25 mg/kg.
0.06 ± 0.34*,**,† 0.12 ± 0.43*,**,† 4.93 ± 0.38
−4.74 ± 0.87* −3.60 ± 0.65 −3.54 ± 0.52 −4.49 ± 0.95* −3.54 ± 0.52 −4.67 ± 0.82* −3.54 ± 0.52 −4.15 ± 1.26 4.44 ± 0.52 5.47 ± 0.90
−3.54 ± 0.52 −4.70 ± 0.71
5.64 ± 0.87 4.65 ± 0.71
−4.50 ± 0.98* −2.84 ± 0.78
−4.96 ± 0.86* −3.75 ± 0.71
−4.04 ± 1.14* −1.90 ± 1.89 −3.71 ± 1.39* −1.68 ± 2.08 −4.08 ± 1.06 −3.00 ± 0.87
26 h 24 h 6h
−2.3 ± 1.36 −1.92 ± 1.68
2h
−4.07 ± 0.49 −3.04 ± 1.49** −3.95 ± 0.48* −2.16 ± 2.20** −3.93 ± 0.46 −3.96 ± 0.57
5.11 ± 0.85 4.79 ± 0.75 26 h 24 h 6h
−3.32 ± 1.17 −3.27 ± 1.17
2h
4.82 ± 0.45 5.16 ± 0.67
DAP 15 mg/kg DAP 15 mg/kg + DEX 0.25 mg/kg DAP 25 mg/kg DAP 25 mg/kg + DEX 0.25 mg/kg Control (saline)
CFU/mL Initial titre at 0 h (log10 CFU/mL) Initial titre at 0 h (log10 CFU/mL)
CFU/mL
ATCC 51916 strain HUB 2349 strain Therapy group (dose in mg/kg/day)
Table 1 Initial bacterial counts in the cerebrospinal fluid of rabbits with pneumococcal meningitis caused by two strains of Streptococcus pneumoniae and changes in bacterial counts (CFU/mL) following administration of high- and low-dose daptomycin (DAP) alone and in combination with dexamethasone (DEX).a
−4.74 ± 0.87* −3.60 ± 0.65
M. Vivas et al. / International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
4
To treat bacterial meningitis, it would be necessary to establish an antibiotic therapy whose efficacy and penetration are not affected by combination with dexamethasone. The results of this study show that concomitant use of dexamethasone reduces the penetration of daptomycin into CSF compared with the use of daptomycin alone. Daptomycin 15 mg/kg reduced bacterial counts more rapidly than the combination with dexamethasone and was significantly more effective at 24 h in both strains and at 26 h in the highly cephalosporin-resistant strain (P ≤ 0.05 at 24 h and 26 h) (Table 1). The decrease in CSF daptomycin levels when dexamethasone is given has consequences in the low-dose (15 mg/kg) group, causing >50% of therapeutic failures at 24 h for both strains studied. Despite this, the efficacy is not compromised with high doses of daptomycin (25 mg/kg). Daptomycin 25 mg/kg achieved bactericidal concentrations from the very beginning of treatment, and addition of dexamethasone did not lead to any therapeutic failure. The fact that CSF levels of daptomycin at a dose of 25 mg/kg with dexamethasone were significantly lower than with daptomycin alone is irrelevant since they are still more than 100× the MIC and the efficacy is not affected. These results confirm those obtained with another experimental murine model [17] of pneumococcal meningitis, which found that concomitant use of dexamethasone in combination with daptomycin did not affect the antibiotic’s therapeutic efficacy.
Please cite this article in press as: Vivas M, et al. Effect of dexamethasone on the efficacy of daptomycin in the therapy of experimental pneumococcal meningitis. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.01.014
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A similar experimental study with rabbits by Egermann et al. [18] using low-dose daptomycin with and without dexamethasone concluded that addition of dexamethasone affected the efficacy of daptomycin, causing a delay in the sterilisation of CSF samples. However, by the end of treatment the activity was the same in the two therapy groups. Although dexamethasone affects daptomycin penetration, we strongly favour its concomitant use in the treatment of bacterial meningitis in order to achieve a good prognosis. Establishing its safety when used in combination with antibiotics is extremely important. The efficacy of daptomycin at high doses with dexamethasone is a promising finding that may also be relevant to the treatment of other infections such as neurosurgical infections caused by other micro-organisms. However, further investigations may be required in other micro-organisms that cause meningitis, since different ranges of MIC may present different results and there is no guarantee that the combination of daptomycin plus dexamethasone will be effective in other settings. As far as we know, there is no clinical experience with daptomycin and dexamethasone. In conclusion, against the studied strains, CSF levels of daptomycin are lowered by the concomitant use of dexamethasone. At a high dose of daptomycin (25 mg/kg/day), however, the efficacy of daptomycin is not altered by the use of dexamethasone and this combination appears to be a good choice for the treatment of pneumococcal meningitis. Acknowledgments CC and MV are members of the Spanish Network for the Research in Infectious Diseases (REIPI RD12/0015), Instituto de Salud Carlos III (Madrid, Spain). Funding: Financial support was provided by a research grant from the Instituto de Salud Carlos III FIS 09/518 and by a grant from Novartis. Competing interests: None declared. Ethical approval: The experimental protocol was in accordance with Spanish legislation on animal experimentation and was approved by the Ethics Committee for Animal Experiments at the University of Barcelona (Barcelona, Spain) [reference no. CEEA 173/13]. References [1] Brouwer MC, McIntyre P, Prasad K, van de Beek D. Corticosteroids for acute bacterial meningitis. Cochrane Database Syst Rev 2013;6:CD004405.
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[2] Arditi M, Mason Jr EO, Bradley JS, Tan TQ, Barson WJ, Schutze GE, et al. Threeyear multicenter surveillance of pneumococcal meningitis in children: clinical characteristics and outcome related to penicillin susceptibility and dexamethasone use. Pediatrics 1998;102:1087–97. [3] Bernardo WM, Aires FT, Sá FP. Effectiveness of the association of dexamethasone with antibiotic therapy in pediatric patients with bacterial meningitis. Rev Assoc Med Bras 2012;58:319–22. [4] McIntyre PB, Berkey CS, King SM, Schaad UB, Kilpi T, Kanra GY, et al. Dexamethasone as adjunctive therapy in bacterial meningitis. A meta-analysis of randomized clinical trials since 1988. JAMA 1997;278:925–31. [5] De Gans J, van de Beek D, European Dexamethasone in Adulthood Bacterial Meningitis Study Investigators. Dexamethasone in adults with bacterial meningitis. N Engl J Med 2002;347:1549–56. [6] Thomas R, Le Tulzo Y, Bouget J, Camus C, Michelet C, Le Corre P, et al. Trial of dexamethasone treatment for severe bacterial meningitis in adults. Adult Meningitis Steroid Group. Intensive Care Med 1999;25:475–80. ˜ [7] Viladrich PF, Gudiol F, Linares J, Pallarés R, Sabaté I, Rufí G, et al. Evaluation of vancomycin for therapy of adult pneumococcal meningitis. Antimicrob Agents Chemother 1991;35:2467–72. [8] Ricard JD, Wolff M, Lacherade JC, Mourvillier B, Hidri N, Barnaud G, et al. Levels of vancomycin in cerebrospinal fluid of adult patients receiving adjunctive corticosteroids to treat pneumococcal meningitis: a prospective multicenter observational study. Clin Infect Dis 2007;44:250–5. [9] Syrogiannopoulos GA, Olsen KD, Reisch JS, McCracken Jr GH. Dexamethasone in the treatment of experimental Haemophilus influenzae type b meningitis. J Infect Dis 1987;155:213–9 [Erratum in: J Infect Dis 1987;155:1359]. ˜ [10] Cabellos C, Martínez-Lacasa J, Tubau F, Fernández A, Viladrich PF, Linares J, et al. Evaluation of combined ceftriaxone and dexamethasone therapy in experimental cephalosporin-resistant pneumococcal meningitis. J Antimicrob Chemother 2000;45:315–20. [11] Martínez-Lacasa J, Cabellos C, Martos A, Fernández A, Tubau F, Viladrich PF, et al. Experimental study of the efficacy of vancomycin, rifampicin and dexamethasone in the therapy of pneumococcal meningitis. J Antimicrob Chemother 2002;49:507–13. [12] París MM, Hickey SM, Uscher MI, Shelton S, Olsen KD, McCracken Jr GH. Effect of dexamethasone on therapy of experimental penicillinand cephalosporin-resistant pneumococcal meningitis. Antimicrob Agents Chemother 1994;38:1320–4. [13] Vivas M, Force E, Garrigós C, Tubau F, Platteel AC, Ariza J, et al. Experimental study of the efficacy of daptomycin for the treatment of cephalosporin-resistant pneumococcal meningitis. J Antimicrob Chemother 2014;69:3020–6. [14] Dacey RG, Sande MA. Effect of probenecid on cerebrospinal fluid concentrations of penicillin and cephalosporin derivatives. Antimicrob Agents Chemother 1974;6:437–41. ˜ [15] Ribes S, Doménech A, Cabellos C, Tubau F, Linares J, Viladrich PF, et al. Experimental meningitis due to a high-level cephalosporin-resistant strain of Streptococcus pneumoniae serotype 23F. Enferm Infecc Microbiol Clin 2003;21:329–33 [in Spanish]. [16] Chapin-Robertson K, Edberg SC. Measurements of antibiotics in human body fluids: techniques and significance. In: Lorian V, editor. Antibiotics in laboratory medicine. New York, NY: Williams and Wilkins; 1991. p. 295–366. [17] Mook-Kanamori BB, Rouse MS, Kang CI, van de Beek D, Steckelberg JM, Patel R. Daptomycin in experimental murine pneumococcal meningitis. BMC Infect Dis 2009;9:50. [18] Egermann U, Stanga Z, Ramin A, Acosta F, Stucki A, Gerber P, et al. Combination of daptomycin plus ceftriaxone is more active than vancomycin plus ceftriaxone in experimental meningitis after addition of dexamethasone. Antimicrob Agents Chemother 2009;53:3030–3.
Please cite this article in press as: Vivas M, et al. Effect of dexamethasone on the efficacy of daptomycin in the therapy of experimental pneumococcal meningitis. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.01.014
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
Effect of dexamethasone on the efficacy of daptomycin in the therapy of experimental pneumococcal meningitis M. Vivas a,∗ , E. Force a , F. Tubau b , C. El Haj a , J. Ariza a , C. Cabellos a a Laboratory of Experimental Infection, Infectious Diseases Department, IDIBELL-Hospital Universitari de Bellvitge, Feixa Llarga s/n, 08907 L’Hospitalet de Llobregat, Barcelona, Spain b Microbiology Department, IDIBELL-Hospital Universitari de Bellvitge and CIBERES ISCIII, Feixa Llarga s/n, 08907 L’Hospitalet de Llobregat, Barcelona, Spain
a r t i c l e
i n f o
Article history: Received 10 October 2014 Accepted 28 January 2015 Keywords: Steroids Lipopeptide CNS infection Streptococcus pneumoniae
a b s t r a c t This study aimed to determine the effect of dexamethasone in combination with low-dose or highdose daptomycin for the treatment of penicillin- and cephalosporin-resistant pneumococcal meningitis. Efficacy (CFU/mL) and cerebrospinal fluid (CSF) levels of daptomycin at 15 mg/kg and 25 mg/kg were studied in a rabbit model of pneumococcal meningitis, comparing them with the same doses in combination with dexamethasone at 0.125 mg/kg every 12 h over a 26-h period against two different Streptococcus pneumoniae strains, HUB 2349 and ATCC 51916 with daptomycin minimum inhibitory concentrations (MICs) of 0.09 mg/L and 0.19 mg/L, respectively. Daptomycin levels in CSF were lower when dexamethasone was given concurrently. Against strain HUB 2349, therapeutic failure occurred with daptomycin 15 mg/kg + dexamethasone; daptomycin 25 mg/kg + dexamethasone was better at reducing bacterial counts than the lower dose throughout treatment. Against the highly cephalosporin-resistant ATCC 51916 strain, daptomycin 15 mg/kg + dexamethasone achieved a lower bacterial decrease than daptomycin 15 mg/kg alone, and therapeutic failure at 24 h occurred in the daptomycin 15 mg/kg + dexamethasone group. Addition of dexamethasone to a 25 mg/kg daptomycin dose did not affect the efficacy of daptomycin: it remained bactericidal throughout treatment. In conclusion, against the studied strains, low-dose (15 mg/kg/day) daptomycin is affected by concomitant use of dexamethasone: CSF levels are reduced and its bacterial efficacy is affected. At a higher daptomycin dose (25 mg/kg/day), however, the use of dexamethasone does not alter efficacy; the combination appears to be a good choice for the treatment of pneumococcal meningitis. © 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
1. Introduction Despite the efficacy of antibiotic therapy, the mortality rate of bacterial meningitis is still significant, ranging between 10% and 30% [1], and >30% of survivors develop long-term sequelae including hearing loss and neurological deficits [2]. The rapid bactericidal action of daptomycin makes it an attractive alternative for the treatment of multidrug-resistant pneumococcal meningitis. In addition, its non-bacteriolytic activity may represent an advantage even in cases of full -lactam susceptibility. Adjunctive treatment with corticosteroids has been recommended to decrease the inflammation and mortality in bacterial meningitis. Several clinical studies have demonstrated that
∗ Corresponding author. Tel.: +34 932 607 625/934 035 805; fax: +34 932 607 637. E-mail address: [email protected] (M. Vivas).
dexamethasone is beneficial in the treatment of the condition, reducing mortality and improving the prognosis [1], but concomitant use of dexamethasone in combination with antibiotic therapy is still controversial [3]. Diverse clinical trials have demonstrated that adjunctive therapy with dexamethasone reduced severe hearing loss in children and reduced the risk of death and non-favourable sequelae in adults with bacterial meningitis [4,5]. However, it is well known that concomitant use of dexamethasone affects antibiotic penetration into the cerebrospinal fluid (CSF) across the blood–brain barrier and may be associated with failure of antibiotic therapy [6]. Two clinical studies showed that dexamethasone could affect the efficacy of vancomycin for the treatment of pneumococcal meningitis depending on the antibiotic concentrations in the CSF [7,8]. The interaction between dexamethasone and different antibiotics has been widely studied in experimental meningitis models. Syrogiannopoulos et al. assessed the effect of dexamethasone in
http://dx.doi.org/10.1016/j.ijantimicag.2015.01.014 0924-8579/© 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
Please cite this article in press as: Vivas M, et al. Effect of dexamethasone on the efficacy of daptomycin in the therapy of experimental pneumococcal meningitis. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.01.014
G Model ANTAGE-4535; No. of Pages 5
ARTICLE IN PRESS M. Vivas et al. / International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
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combination with ceftriaxone. CSF antibiotic levels were lower when dexamethasone was added and they found no differences in inflammation parameters [9]. Another experimental study by our group demonstrated that the use of dexamethasone resulted in therapeutic failure and a substantial decrease in ceftriaxone levels in the CSF, even at high ceftriaxone doses, in a cephalosporin-resistant strain of Streptococcus pneumoniae [10]. Addition of dexamethasone had a beneficial effect on the inflammatory response in an experimental study using rifampicin, rifampicin plus vancomycin, and ceftriaxone plus rifampicin and did not significantly interfere with antibiotic levels in the CSF [11,12]. Demonstrating that the efficacy of antibiotic therapy is not affected by concomitant use of dexamethasone is a matter of necessity, since the use of dexamethasone may represent a useful adjunctive therapy in cases of pneumococcal meningitis. In an experimental animal model, we recently reported [13] that daptomycin may represent a good alternative for the treatment of penicillin- and cephalosporin-resistant strains of S. pneumoniae owing to its ability to sterilise CSF samples from the very beginning of treatment. The aim of this study was to test the effect of dexamethasone as standard adjunctive therapy given in combination with low-dose or high-dose daptomycin on the treatment of penicillin- and cephalosporin-resistant strains of S. pneumoniae in an experimental meningitis model.
2. Materials and methods 2.1. Bacterial strains Two different strains of S. pneumoniae isolated from patients with meningitis were used: strain HUB 2349 is penicillinand cephalosporin-resistant; and the ATCC 51916 strain (Tennessee 23F-4 clone) is intermediately penicillin-resistant and highly cephalosporin-resistant. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations, respectively, were as follows: for strain HUB 2349, penicillin, 4 mg/L and 4 mg/L; ceftriaxone/cefotaxime, 2 mg/L and 4 mg/L; vancomycin, 0.25 mg/L and 0.25 mg/L; and daptomycin, 0.09 mg/L and 0.18 mg/L; and for the ATCC 51916 strain, penicillin, 0.12 mg/L and 0.25 mg/L; ceftriaxone/cefotaxime, 32 mg/L and 32 mg/L; vancomycin, 0.25 mg/L and 0.25 mg/L; and daptomycin, 0.19 mg/L and 0.38 mg/L.
Animals were placed in a stereotactic frame and a baseline CSF sample was taken (0 h). A dose of dexamethasone (Fortecortin® ; Merck, Barcelona, Spain) of 0.25 mg/24 h divided every 12 h (q12h) was given intravenously. Then, 10 min later antibiotic therapy was administered. CSF samples were taken after 2, 6, 24 and 26 h of therapy. Hydration was ensured throughout the experiment. Mortality was assessed at 26 h. Surviving animals were euthanised using a lethal dose of thiopental sodium at the end of each experiment.
2.2.2. Therapeutic groups Intravenous antibiotic therapy was then administered for 26 h using one of the following therapy schedules: daptomycin at 15 mg/kg (n = 8 rabbits for each strain) given once daily; daptomycin 15 mg/kg given once daily plus dexamethasone (n = 9 rabbits for each strain) at 0.125 mg/kg q12h; daptomycin at 25 mg/kg (n = 9 rabbits for each strain) given once daily; and daptomycin 25 mg/kg given once daily plus dexamethasone (n = 10 rabbits for each strain) at 0.125 mg/kg q12h. Untreated control rabbits received saline. Part of the results have already been described in our previous study [13].
2.3. Sample processing CSF samples were used to determine CSF white blood cell (WBC) counts, bacterial counts and antibiotic levels at peak and trough time points. For leukocyte counts, 10 L of each sample was diluted 1:1 with Turk solution and read with a Neubauer chamber. Animals presenting ≥300 cells/mm3 were included in the study groups. Serial ten-fold dilutions were made to determine bacterial counts at each time point. To avoid interference due to carryover of antimicrobial agent, an entire agar plate was used for each sample. The lowest bacterial concentration detectable was 10 CFU/mL. For the purpose of analysis, a value of 0.99 log CFU/mL was assigned to the first sterile culture, and a value of 0 log CFU/mL to subsequent ones. Changes in bacterial counts (log CFU/mL) were calculated as the difference between bacterial concentrations at the start of therapy and at 2, 6, 24 and 26 h. Therapeutic failure was defined as an increase in bacterial concentration of ≥1 log CFU/mL compared with a previous count. A therapy was considered bactericidal when a reduction of 3 log CFU/mL was achieved. Samples were centrifuged at 5000 × g for 10 min and the supernatants were stored at −70 ◦ C.
2.2. In vivo studies
2.4. Antibiotic assays
2.2.1. Meningitis model The rabbit model of meningitis originally described by Dacey and Sande [14] was used with slight modifications. Young female New Zealand White rabbits were anaesthetised intramuscularly with 35 mg/kg ketamine (Ketolar® ; Parke-Davis, Prat de Llobregat, Spain) and 5 mg/kg xylazine (Rompun® ; Bayer AG, Leverkusen, Germany). Meningitis was induced with an intracisternal injection of 250 L of a saline suspension containing 106 CFU/mL of inoculum. In rabbits infected with the HUB 2349 strain, therapy was started 18 h post-inoculation. In animals infected with the ATCC 51916 strain, therapy was initiated 40 h post-inoculation owing to the slow progression of meningitis [15]. Rabbits were anaesthetised using urethane (Sigma Chemical Co., St Louis, MO) at 1.75 g/kg subcutaneously and thiopental sodium (Tiopental® ; B. Braun Medical S.A., Rubí, Spain) at 5 mg/kg intravenously. A blood sample was collected to assess secondary bacteraemia.
Daptomycin concentrations were measured using the agar disk diffusion method [16] using Micrococcus luteus ATCC 9341 [linearity of assay (r2 ) = 0.99; lower detection limit, 2 g/mL] as the assay organism.
2.5. Statistical analysis All bacterial counts are presented as log numbers of CFU per millilitre (mean ± standard deviation). Differences in bacterial counts between treated and untreated animals were evaluated for statistical significance using analysis of variance (ANOVA). An unpaired Student’s t-test with Bonferroni correction was used to determine statistical significance. WBC counts were compared using the non-parametric Mann–Whitney and Wilcoxon tests. For all tests, differences were considered to be statistically significant when P-values were 1 log CFU/mL from the previous counts.
0.72 ± 0.82*,**,†
0.62 ± 0.25*,**,†
5.15 ± 0.82
0.08 ± 0.38**,†
3.2.2. ATCC 51916 strain Secondary bacteraemia at 0 h was 100%. Mortality at 26 h was 50% in the control group, 11.1% for daptomycin 15 mg/kg, 25% for daptomycin 15 mg/kg + dexamethasone, 0% for daptomycin 25 mg/kg and 14.3% for daptomycin 25 mg/kg + dexamethasone. There were no significance between therapeutic groups. The CSF of infected rabbits showed inflammation in terms of high WBC counts throughout the experiment. CSF WBC counts at 0 h and 24 h did not differ significantly between the therapy groups. The two doses of daptomycin with and without dexamethasone were significantly better than the control group throughout the treatment. Daptomycin 15 mg/kg + dexamethasone presented a bacterial decrease at each point of the experiment, being significantly lower than daptomycin 15 mg/kg alone and daptomycin 25 mg/kg + dexamethasone at 24 h and 26 h. Therapeutic failures at 24 h occurred in 57% of the daptomycin 15 mg/kg + dexamethasone group versus 25% of the daptomycin 15 mg/kg group. Addition of dexamethasone to the 25 mg/kg daptomycin dose did not affect the efficacy of daptomycin, which was bactericidal throughout the treatment. No therapeutic failure occurred with daptomycin 25 mg/kg either alone or with dexamethasone. 4. Discussion
†
**
*
a
Data are expressed as the mean ± standard deviation. P ≤ 0.05 vs. daptomycin 15 mg/kg + dexamethasone. P ≤ 0.05 vs. daptomycin 25 mg/kg + dexamethasone. P ≤ 0.05 vs. daptomycin 15 mg/kg and daptomycin 25 mg/kg.
0.06 ± 0.34*,**,† 0.12 ± 0.43*,**,† 4.93 ± 0.38
−4.74 ± 0.87* −3.60 ± 0.65 −3.54 ± 0.52 −4.49 ± 0.95* −3.54 ± 0.52 −4.67 ± 0.82* −3.54 ± 0.52 −4.15 ± 1.26 4.44 ± 0.52 5.47 ± 0.90
−3.54 ± 0.52 −4.70 ± 0.71
5.64 ± 0.87 4.65 ± 0.71
−4.50 ± 0.98* −2.84 ± 0.78
−4.96 ± 0.86* −3.75 ± 0.71
−4.04 ± 1.14* −1.90 ± 1.89 −3.71 ± 1.39* −1.68 ± 2.08 −4.08 ± 1.06 −3.00 ± 0.87
26 h 24 h 6h
−2.3 ± 1.36 −1.92 ± 1.68
2h
−4.07 ± 0.49 −3.04 ± 1.49** −3.95 ± 0.48* −2.16 ± 2.20** −3.93 ± 0.46 −3.96 ± 0.57
5.11 ± 0.85 4.79 ± 0.75 26 h 24 h 6h
−3.32 ± 1.17 −3.27 ± 1.17
2h
4.82 ± 0.45 5.16 ± 0.67
DAP 15 mg/kg DAP 15 mg/kg + DEX 0.25 mg/kg DAP 25 mg/kg DAP 25 mg/kg + DEX 0.25 mg/kg Control (saline)
CFU/mL Initial titre at 0 h (log10 CFU/mL) Initial titre at 0 h (log10 CFU/mL)
CFU/mL
ATCC 51916 strain HUB 2349 strain Therapy group (dose in mg/kg/day)
Table 1 Initial bacterial counts in the cerebrospinal fluid of rabbits with pneumococcal meningitis caused by two strains of Streptococcus pneumoniae and changes in bacterial counts (CFU/mL) following administration of high- and low-dose daptomycin (DAP) alone and in combination with dexamethasone (DEX).a
−4.74 ± 0.87* −3.60 ± 0.65
M. Vivas et al. / International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
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To treat bacterial meningitis, it would be necessary to establish an antibiotic therapy whose efficacy and penetration are not affected by combination with dexamethasone. The results of this study show that concomitant use of dexamethasone reduces the penetration of daptomycin into CSF compared with the use of daptomycin alone. Daptomycin 15 mg/kg reduced bacterial counts more rapidly than the combination with dexamethasone and was significantly more effective at 24 h in both strains and at 26 h in the highly cephalosporin-resistant strain (P ≤ 0.05 at 24 h and 26 h) (Table 1). The decrease in CSF daptomycin levels when dexamethasone is given has consequences in the low-dose (15 mg/kg) group, causing >50% of therapeutic failures at 24 h for both strains studied. Despite this, the efficacy is not compromised with high doses of daptomycin (25 mg/kg). Daptomycin 25 mg/kg achieved bactericidal concentrations from the very beginning of treatment, and addition of dexamethasone did not lead to any therapeutic failure. The fact that CSF levels of daptomycin at a dose of 25 mg/kg with dexamethasone were significantly lower than with daptomycin alone is irrelevant since they are still more than 100× the MIC and the efficacy is not affected. These results confirm those obtained with another experimental murine model [17] of pneumococcal meningitis, which found that concomitant use of dexamethasone in combination with daptomycin did not affect the antibiotic’s therapeutic efficacy.
Please cite this article in press as: Vivas M, et al. Effect of dexamethasone on the efficacy of daptomycin in the therapy of experimental pneumococcal meningitis. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.01.014
G Model ANTAGE-4535; No. of Pages 5
ARTICLE IN PRESS M. Vivas et al. / International Journal of Antimicrobial Agents xxx (2015) xxx–xxx
A similar experimental study with rabbits by Egermann et al. [18] using low-dose daptomycin with and without dexamethasone concluded that addition of dexamethasone affected the efficacy of daptomycin, causing a delay in the sterilisation of CSF samples. However, by the end of treatment the activity was the same in the two therapy groups. Although dexamethasone affects daptomycin penetration, we strongly favour its concomitant use in the treatment of bacterial meningitis in order to achieve a good prognosis. Establishing its safety when used in combination with antibiotics is extremely important. The efficacy of daptomycin at high doses with dexamethasone is a promising finding that may also be relevant to the treatment of other infections such as neurosurgical infections caused by other micro-organisms. However, further investigations may be required in other micro-organisms that cause meningitis, since different ranges of MIC may present different results and there is no guarantee that the combination of daptomycin plus dexamethasone will be effective in other settings. As far as we know, there is no clinical experience with daptomycin and dexamethasone. In conclusion, against the studied strains, CSF levels of daptomycin are lowered by the concomitant use of dexamethasone. At a high dose of daptomycin (25 mg/kg/day), however, the efficacy of daptomycin is not altered by the use of dexamethasone and this combination appears to be a good choice for the treatment of pneumococcal meningitis. Acknowledgments CC and MV are members of the Spanish Network for the Research in Infectious Diseases (REIPI RD12/0015), Instituto de Salud Carlos III (Madrid, Spain). Funding: Financial support was provided by a research grant from the Instituto de Salud Carlos III FIS 09/518 and by a grant from Novartis. Competing interests: None declared. Ethical approval: The experimental protocol was in accordance with Spanish legislation on animal experimentation and was approved by the Ethics Committee for Animal Experiments at the University of Barcelona (Barcelona, Spain) [reference no. CEEA 173/13]. References [1] Brouwer MC, McIntyre P, Prasad K, van de Beek D. Corticosteroids for acute bacterial meningitis. Cochrane Database Syst Rev 2013;6:CD004405.
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[2] Arditi M, Mason Jr EO, Bradley JS, Tan TQ, Barson WJ, Schutze GE, et al. Threeyear multicenter surveillance of pneumococcal meningitis in children: clinical characteristics and outcome related to penicillin susceptibility and dexamethasone use. Pediatrics 1998;102:1087–97. [3] Bernardo WM, Aires FT, Sá FP. Effectiveness of the association of dexamethasone with antibiotic therapy in pediatric patients with bacterial meningitis. Rev Assoc Med Bras 2012;58:319–22. [4] McIntyre PB, Berkey CS, King SM, Schaad UB, Kilpi T, Kanra GY, et al. Dexamethasone as adjunctive therapy in bacterial meningitis. A meta-analysis of randomized clinical trials since 1988. JAMA 1997;278:925–31. [5] De Gans J, van de Beek D, European Dexamethasone in Adulthood Bacterial Meningitis Study Investigators. Dexamethasone in adults with bacterial meningitis. N Engl J Med 2002;347:1549–56. [6] Thomas R, Le Tulzo Y, Bouget J, Camus C, Michelet C, Le Corre P, et al. Trial of dexamethasone treatment for severe bacterial meningitis in adults. Adult Meningitis Steroid Group. Intensive Care Med 1999;25:475–80. ˜ [7] Viladrich PF, Gudiol F, Linares J, Pallarés R, Sabaté I, Rufí G, et al. Evaluation of vancomycin for therapy of adult pneumococcal meningitis. Antimicrob Agents Chemother 1991;35:2467–72. [8] Ricard JD, Wolff M, Lacherade JC, Mourvillier B, Hidri N, Barnaud G, et al. Levels of vancomycin in cerebrospinal fluid of adult patients receiving adjunctive corticosteroids to treat pneumococcal meningitis: a prospective multicenter observational study. Clin Infect Dis 2007;44:250–5. [9] Syrogiannopoulos GA, Olsen KD, Reisch JS, McCracken Jr GH. Dexamethasone in the treatment of experimental Haemophilus influenzae type b meningitis. J Infect Dis 1987;155:213–9 [Erratum in: J Infect Dis 1987;155:1359]. ˜ [10] Cabellos C, Martínez-Lacasa J, Tubau F, Fernández A, Viladrich PF, Linares J, et al. Evaluation of combined ceftriaxone and dexamethasone therapy in experimental cephalosporin-resistant pneumococcal meningitis. J Antimicrob Chemother 2000;45:315–20. [11] Martínez-Lacasa J, Cabellos C, Martos A, Fernández A, Tubau F, Viladrich PF, et al. Experimental study of the efficacy of vancomycin, rifampicin and dexamethasone in the therapy of pneumococcal meningitis. J Antimicrob Chemother 2002;49:507–13. [12] París MM, Hickey SM, Uscher MI, Shelton S, Olsen KD, McCracken Jr GH. Effect of dexamethasone on therapy of experimental penicillinand cephalosporin-resistant pneumococcal meningitis. Antimicrob Agents Chemother 1994;38:1320–4. [13] Vivas M, Force E, Garrigós C, Tubau F, Platteel AC, Ariza J, et al. Experimental study of the efficacy of daptomycin for the treatment of cephalosporin-resistant pneumococcal meningitis. J Antimicrob Chemother 2014;69:3020–6. [14] Dacey RG, Sande MA. Effect of probenecid on cerebrospinal fluid concentrations of penicillin and cephalosporin derivatives. Antimicrob Agents Chemother 1974;6:437–41. ˜ [15] Ribes S, Doménech A, Cabellos C, Tubau F, Linares J, Viladrich PF, et al. Experimental meningitis due to a high-level cephalosporin-resistant strain of Streptococcus pneumoniae serotype 23F. Enferm Infecc Microbiol Clin 2003;21:329–33 [in Spanish]. [16] Chapin-Robertson K, Edberg SC. Measurements of antibiotics in human body fluids: techniques and significance. In: Lorian V, editor. Antibiotics in laboratory medicine. New York, NY: Williams and Wilkins; 1991. p. 295–366. [17] Mook-Kanamori BB, Rouse MS, Kang CI, van de Beek D, Steckelberg JM, Patel R. Daptomycin in experimental murine pneumococcal meningitis. BMC Infect Dis 2009;9:50. [18] Egermann U, Stanga Z, Ramin A, Acosta F, Stucki A, Gerber P, et al. Combination of daptomycin plus ceftriaxone is more active than vancomycin plus ceftriaxone in experimental meningitis after addition of dexamethasone. Antimicrob Agents Chemother 2009;53:3030–3.
Please cite this article in press as: Vivas M, et al. Effect of dexamethasone on the efficacy of daptomycin in the therapy of experimental pneumococcal meningitis. Int J Antimicrob Agents (2015), http://dx.doi.org/10.1016/j.ijantimicag.2015.01.014
