Journal of Antimicrobial Chemotherapy (2001) 48, 131-135
© 2001 The British Society for Antimicrobial Chemotherapy
Brief report |
In vitro and in vivo efficacy of a novel fluoro-ketolide HMR 3562 against enterococci
Aventis Pharma, Infectious Diseases Group, Microbiology, 102, Route de Noisy, 93235 Romainville Cedex, France
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and methodsResultsDiscussionReferences |
|---|
The in vitro activity of HMR 3562, a new 2-fluoro-ketolide drug, was investigated against 95 enterococci, including 36 vancomycin-resistant strains. HMR 3562 inhibited 90% of enterococci susceptible or resistant to erythromycin A at 0.005 and 0.6 mg/L, respectively. HMR 3562 was highly active in murine peritonitis induced by five enterococci, irrespective of resistance phenotype, displaying effective doses in the range 3.4–21.8 mg/kg. The results demonstrate the potential of HMR 3562 in the treatment of infections caused by multiresistant enterococci.
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Even though enterococci, which are normal human commensals, are less virulent than certain other Gram-positive bacteria, they have been recognized as important causes of nosocomial and community-acquired diseases. Enterococcus faecalis causes 80–90% of human enterococcal infections, while Enterococcus faecium and Enterococcus durans account for a majority of the remainder.1 Such infections may be difficult to treat because of intrinsic or acquired resistance of enterococci to many antimicrobial agents,2 prompting the search for new drugs.
Ketolides are a new class of semi-synthetic 14- membered-ring macrolides, active against respiratory tract pathogens and also enterococci.3,4 Introduction of a fluorine moiety in position 2 of the macrolactone skeleton improves the overall antibacterial spectrum, as reported previously for novel 2-fluoro-ketolides,5 such as HMR 3562. Here, we focused on the in vitro and in vivo antibacterial activity of HMR 3562 against enterococci, including vancomycin-resistant strains.
|
Materials and methods |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Antibiotics
HMR 3562, erythromycin A, clarithromycin and azithromycin were prepared by Aventis (Romainville, France). Pristinamycin was provided by Aventis (Vitry, France). Teicoplanin and vancomycin were purchased from Sigma (St Louis, MO, USA).
Bacterial strains
Ninety-five strains were tested: 51 E. faecalis, 40 E. faecium, two Enterococcus gallinarum, one E. durans and one Enterococcus casseliflavus. Thirty-six isolates were vancomycin resistant. All the strains tested were clinical isolates from various European and US hospitals, except the reference strain E. faecalis ATCC 29212 used for quality control.
MIC determination
MICs were measured by a two-fold agar dilution method in Mueller–Hinton (MH) agar medium (pH 7.4; Diagnostic Pasteur, France).6 A standard inoculum of 104 cfu/spot was used throughout the study. All plates were incubated at 37°C for 24 h. The MIC was defined as the lowest concentration at which no visible growth could be detected on agar plates. According to NCCLS breakpoints, MICs for susceptible strains were 
0.5, 4 and 8 mg/L for erythromycin, vancomycin and teicoplanin, respectively.
Systemic infection model
The present studies were approved by the Internal Animal Ethics Committee. Male C3H and C57Bl/6 Charles River mice were used to study the antibacterial activity of compounds in a peritonitis model against vancomycin-susceptible and -resistant strains, respectively. Each dosing group was composed of 10 animals weighing 20–22 g. Mice were infected intraperitoneally with 0.5 mL of an overnight culture suspended in physiological buffer containing 5% pig mucin (Sigma) to a final cell density corresponding to 10–100 times the minimal lethal dose, i.e. approximately 109 cfu. Bovine haemoglobin (2%) (Sigma) was added when testing vancomycin-resistant strains. Under these conditions, untreated animals died by 48–72 h. Suspensions of compounds (0.5 mL) were administered in carboxymethyl cellulose (Sigma) by the oral route, except for vancomycin, immediately and 4 h post-infection. Vancomycin was administered subcutaneously in saline buffer. Mice were observed for 8–10 days following the inoculation, and the 50% protective dose (PD50) expressed as the unit dose that protected 50% of the animals from death was calculated by the probit method of Litchfield & Wilcoxon.7
|
Results |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
In vitro susceptibility results
Table I
indicates the in vitro activity of HMR 3562 against 95 enterococci. The MICs of erythromycin, vancomycin and teicoplanin for E. faecalis ATCC 29212 were 1.2, 2.5 and 0.08 mg/L, respectively, which are within NCCLS quality control breakpoint limits.
|
Against erythromycin A-susceptible strains, HMR 3562 was 100 times more active than erythromycin A or clarithromycin (MIC90 of 0.005 mg/L). The ketolide was the only compound active against erythromycin A-resistant strains (MIC90 of 0.6 mg/L). A similar MIC90 was observed for vancomycin-resistant isolates, irrespective of the VanA or VanB phenotype. HMR 3562 was more active against E. faecalis than against E. faecium, particularly against erythromycin A-resistant isolates, with MIC50/MIC90 of 0.04/0.3 and 0.3/0.6 mg/L, respectively.
PD50 determinations
Table II gives the PD50s of HMR 3562, clarithromycin, pristinamycin and vancomycin obtained in five different lethal infections induced by one E. faecalis and four E. faecium isolates in a murine peritonitis model. The activity of HMR 3562 did not depend on the resistance phenotype of the strains tested and was the highest, with PD50 ranging from 3.4 to 21.8 mg/kg. As expected, vancomycin was completely inactive against vancomycin-resistant isolates.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
The emergence of virulent isolates of enterococci with high levels of intrinsic penicillin resistance has limited the use of ß-lactams as first line therapy. Although new quinolones may be more active, they still remain contraindicated in pregnant women or young children. In contrast, macrolides are usually considered as safe antibacterial agents. Structural changes in ketolides render them drastically different from macrolides, particularly in their activity against multiresistant Gram-positive cocci, with telithromycin (HMR 3647) being active against enterococci.4 In the search for new compounds, the 2-fluoro analogue of telithromycin, HMR 3562, has been synthesized.
As shown previously,8,9 HMR 3562 displayed potent activity against E. faecalis and E. faecium, irrespective of their erythromycin A susceptibility status. The MIC90 of HMR 3562 for erythromycin A-resistant enterococci was 0.6 mg/L, while all of the macrolides tested remained inactive. As vancomycin resistance is commonly associated with macrolide resistance in enterococci, it is worth noting that HMR 3562 remained active against vancomycinresistant strains. However, as with telithromycin and macrolides,4 HMR 3562 demonstrated bacteriostatic activity against both erythromycin A-susceptible and erythromicin A-resistant strains (data not shown).
There is little published information about therapy of enterococci in murine models, particularly with ketolides.3,10 In experimental peritonitis, we confirmed the in vitro activity of HMR 3562, with consistent efficacy against all of the five strains tested, irrespective of their macrolide resistance phenotype. The PD50 range was 3.4–21.8 mg/kg, while MICs ranged from 0.01 to 0.15 mg/L. On the other hand, despite its favourable MICs, pristinamycin did not show any therapeutic efficacy at the doses tested, probably due to disadvantageous kinetics.
In conclusion, HMR 3562 shows promise as an antimicrobial agent for use against multi-resistant enterococci.
|
Acknowledgments |
|---|
This work was presented in part at the Thirty-ninth Interscience Conference on Antimicrobial Agents and Chemotherapy, San Francisco, CA, USA, September 26–29, 1999.8
|
Notes |
|---|
* Corresponding author. Tel: +33-1-49-91-47-78; Fax: +33-1-49-91-50-61; E-mail: Alain.Bonnefoy{at}aventis.com
|
References |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
1 . Moellering, R. C. (1992). Emergence of Enterococcus as a significant pathogen. Clinical Infectious Diseases 14, 1173–8.[Web of Science][Medline]
2
.
Moellering, R. C. (1991). The Garrod Lecture. The enterococcus: a classic example of the impact of antimicrobial resistance on therapeutic options. Journal of Antimicrobial Chemotherapy 28, 1–12.
3 . Agouridas, C., Bonnefoy, A. & Chantot, J. F. (1997). Antibacterial activity of RU 64004 (HMR 3004), a novel ketolide derivative active against respiratory pathogens. Antimicrobial Agents and Chemotherapy 41, 2149–58.[Abstract]
4
.
Malathum, K., Coque, T. M., Singh, K. V. & Murray, B.E. (1999). In vitro activities of two ketolides, HMR 3647 and HMR 3004 against gram-positive bacteria. Antimicrobial Agents and Chemotherapy 43, 930–6.
5 . Bonnefoy, A., Denis, A., Bretin, F., Fromentin, C. & Agouridas, C. (1999). In vitro antibacterial activity of novel 2-fluoro-ketolides. In Program and Abstracts of the Thirty-ninth Interscience Conference on Antimicrobial Agents and Chemotherapy, San Francisco, CA, 1999. Abstract 2153, p. 351. American Society for Microbiology, Washington, DC.
6 . Barry, A. (1991). Procedures and theoretical considerations for testing antimicrobial agents in agar media. In Antibiotics in Laboratory Medicine, 3rd edn, (Lorian, V., Ed.), pp. 1–16. Williams & Wilkins, Baltimore, MD.
7
.
Litchfield, J. T. & Wilcoxon, F. (1949). A simplified method of evaluating dose-effect experiments. Journal of Pharmacology and Experimental Therapy 96, 99–113.
8 . Bonnefoy, A., Denis, A., Bretin, F., Fromentin, C. & Agouridas, C. (1999). In vitro antibacterial activity of two ketolides, HMR 3562 and HMR 3787, against respiratory pathogens. In Program and Abstracts of the Thirty-ninth Interscience Conference on Antimicrobial Agents and Chemotherapy, San Francisco, CA, 1999. Abstract 2155, p. 351. American Society for Microbiology, Washington, DC.
9 . Felmingham, D., Robbins, M. J., Mathias, I. & Bryskier, A. (1999). In vitro activity of two ketolides, HMR 3562 and HMR 3787 against clinical bacterial isolates. In Program and Abstracts of the Thirty-ninth Interscience Conference on Antimicrobial Agents and Chemotherapy, San Francisco, CA, 1999. Abstract 2154, p. 351. American Society for Microbiology, Washington, DC.
10
.
Singh, K. V., Zscheck, K. K. & Murray, B. E. (2000). Efficacy of telithromycin (HMR 3647) against enterococci in a mouse peritonitis model. Antimicrobial Agents and Chemotherapy 44, 3434–7.
Received 7 December 2000; returned 26 February 2001; revised 19 March 2001; accepted 17 April 2001
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||