JAC Advance Access originally published online on March 13, 2003
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Journal of Antimicrobial Chemotherapy (2003) 51, 1051-1052
© 2003 The British Society for Antimicrobial Chemotherapy
Correspondence |
Activity of ß-lactams (ampicillin, meropenem), gentamicin, azithromycin and moxifloxacin against intracellular Listeria monocytogenes in a 24 h THP-1 human macrophage model
Unité de Pharmacologie Cellulaire et Moléculaire, Université catholique de Louvain, Brussels, Belgium
Keywords: Listeria monocytogenes, pharmacodynamics, intracellular infection, ß-lactams, moxifloxacin
Sir,
Listeria monocytogenes is a facultative intracellular organism causing persistent and life-threatening infections. Recurrence and dissemination of the infection is due to the lack of eradication of intracellular forms, particularly from phagocytes.1 Currently recommended antibacterial therapy of listeriosis combines gentamicin and ampicillin (or meropenem).2 Yet, gentamicin is inactive against the intracellular forms of Listeria, and ampicillin and meropenem are only bacteriostatic in a short-term (5 h) cell culture model.3 This suggested to us that mechanisms other than intrinsic antibacterial properties could play a critical role in vivo, or that the model used did not sufficiently take into account the influence of time (a point of particular importance for ß-lactams that are time-dependent antibiotics4). We have therefore examined the activity of ampicillin, meropenem and gentamicin against extracellular and intracellular L. monocytogenes in a 24 h model. For the sake of comparison, we also examined azithromycin (ineffective against intracellular Listeria in a short-term model in spite of a rapid and very large cellular accumulation) and moxifloxacin (markedly bactericidal at 5 h towards both extracellular and intracellular bacteria).3
Time–kill studies were carried out as described previously.3 For determination of activity against extracellular bacteria, cultures were used at a density of 106 cfu/mL in tryptic soy broth. Antibiotics were then added at a fixed concentration corresponding to the highest serum concentration (Cmax) currently observed after conventional administration to patients.3 Incubation was carried out for 5 and 24 h, and cfu were determined by plate assay.
As shown in Figure 1(a), ampicillin and meropenem acted very slowly and were only slightly bactericidal (0.8 and 0.7 log cfu decrease) at 24 h. In contrast, gentamicin and moxifloxacin were highly bactericidal (gentamicin achieving complete eradication within 5 h). Azithromycin slowed down bacterial growth at 5 h but was without effect at 24 h.
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For measurement of activity against intracellular L. monocytogenes, macrophages (5 x 105/mL) were exposed for 1 h to bacteria (2.5 x 106 cfu/mL), washed extensively, and incubated for 5 and 24 h with or without antibiotics. Cells were collected, washed, lysed in distilled water and the number of viable bacteria determined by plate assay. Cell protein was determined in parallel.
As shown in Figure 1(b), ampicillin and meropenem again acted slowly but were definitely bactericidal at 24 h (2 log reduction of cfu). In sharp contrast with what was observed in broth, gentamicin caused only a modest slow down of the rate of growth of intracellular bacteria. Azithromycin was bacteriostatic both at 5 and 24 h. Moxifloxacin was bactericidal at 5 h (2 log cfu reduction) and its effect was increased at 24 h (3.2 log reduction).
The present data extend our previous studies on activities of antibiotics in Listeria-infected THP-1 macrophages,3 and bring several new pieces of information of both pharmacological and clinical significance.
First we show that gentamicin does not control the growth of intracellular L. monocytogenes for at least 24 h, even though it is highly and very quickly bactericidal against extracellular forms. This could result from the inappropriate subcellular localization of gentamicin (intracellular aminoglycosides being largely if not exclusively sequestered in lysosomes,5 whereas L. monocytogenes multiplies in the cytosol). The usefulness of gentamicin seems therefore limited to eradication of the extracellular forms of Listeria.
Secondly, the data indicate that azithromycin will be ineffective against L. monocytogenes in vivo not only against extracellular bacteria [mainly due to its unfavourable Cmax/MIC ratio (<1)], but also against intracellular forms. This probably results from the fact that azithromycin is intrinsically bacteriostatic, making its cellular accumulation largely useless in this context.
Thirdly, both ampicillin and meropenem kill intracellular bacteria more rapidly and more extensively than extracellular bacteria, even though they do not accumulate in THP-1 cells.3 Yet, ß-lactams penetrate macrophages where they are distributed into the cytosol.5 This should bring them into direct contact with their target in the case of Listeria. The present data indicate therefore some sort of enhancement of the activity of ß-lactams by the intracellular milieu compared with broth. Future studies will be needed to distinguish between a modification of the intrinsic pharmacological properties of ß-lactams and a direct co-operation between host defences and ß-lactams for bacterial killing. It nevertheless clearly appears that prolonged treatment with ampicillin or meropenem may contribute to the eradication of the intracellular forms of L. monocytogenes (as was also observed in another model6).
Finally, we confirm that moxifloxacin is, so far, the most active antibiotic towards both the extracellular and intracellular forms of L. monocytogenes. Therefore, animal trials with moxifloxacin for eradication of L. monocytogenes appear justified.
Acknowledgements
We thank the drug manufacturers for the gifts of the corresponding antibiotics. S.C. is boursier of the Belgian F.R.I.A., and F.V.B. is Chercheur qualifié and M.-P. M.-L. is Maître de recherches of the Belgian F.N.R.S. This work was supported by the Belgian F.R.S.M. (grant 3.4.612.00 F to P.M.T.).
Footnotes
* Corresponding author. Tel: +32-2-7647375; Fax: +32-2-7647373; E-mail: stephane.carryn{at}facm.ucl.ac.be 
References
1
.
Drevets, D. A. (1999). Dissemination of Listeria monocytogenes by infected phagocytes. Infection and Immunity 67, 3512–7.
2 . Temple, M. E. & Nahata, M. C. (2000). Treatment of listeriosis. Annals of Pharmacotherapy 34, 656–61.[Abstract]
3
.
Carryn, S., Van Bambeke, F., Mingeot-Leclercq, M. P. & Tulkens, P. M. (2002). Comparative intracellular (THP-1 macrophage) and extracellular activities of beta-lactams, azithromycin, gentamicin, and fluoroquinolones against Listeria monocytogenes at clinically relevant concentrations. Antimicrobial Agents and Chemotherapy 46, 2095–103.
4
.
Craig, W. A. & Ebert, S. C. (1992). Continuous infusion of beta-lactam antibiotics. Antimicrobial Agents and Chemotherapy 36, 2577–83.
5 . Tulkens, P. M. (1991). Intracellular distribution and activity of antibiotics. European Journal of Clinical Microbiology and Infectious Diseases 10, 100–6.[CrossRef][Web of Science][Medline]
6
.
Michelet, C., Avril, J. L., Cartier, F. & Berche, P. (1994). Inhibition of intracellular growth of Listeria monocytogenes by antibiotics. Antimicrobial Agents and Chemotherapy 38, 438–46.
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