ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, Aug. 2006, p. 2875 2879 Vol. 50, No. 8 0066-4804/06/$08.00 0 doi:10.1128/aac.00286-06 Copyright 2006, American Society for Microbiology. All Rights Reserved. In Vitro Activities of Dalbavancin and 12 Other Agents against 329 Aerobic and Anaerobic Gram-Positive Isolates Recovered from Diabetic Foot Infections Ellie J. C. Goldstein, 1,2 * Diane M. Citron, 1 Yumi A. Warren, 1 Kerin L. Tyrrell, 1 C. Vreni Merriam, 1 and Helen T. Fernandez 1 R. M. Alden Research Laboratory, Santa Monica, California 90404, 1 and David Geffen School of Medicine at UCLA, Los Angeles, California 90073 2 Received 6 March 2006/Returned for modification 5 April 2006/Accepted 3 May 2006 Tests of dalbavancin s in vitro activity against 209 aerobic and 120 anaerobic isolates from pretreatment diabetic foot infections showed an MIC 90 of <0.125 g/ml against methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), and 120 anaerobes (Clostridium perfringens, other clostridia, Peptoniphilus asaccharolyticus, Finegoldia magna, and Anaerococcus prevotii), compared to respective MIC 90 s for MSSA and MRSA of 0.5 and 1 g/ml for vancomycin, 4 and 4 g/ml for linezolid, 0.5 and 0.5 g/ml for daptomycin, and 0.25 and >8 g/ml for clindamycin. Diabetes will affect 14.5 million Americans by 2010 (8), and diabetic foot infections (DFIs) account for 20% of all hospitalizations of diabetic patients (1). DFIs are often multibacterial with aerobic and anaerobic bacteria. Recently, community-acquired methicillin-resistant Staphylococcus aureus (MRSA) (2, 3, 14) has accounted for 50% of all S. aureus skin and skin structure infection (SSTI) isolates (2, 3, 14). Previously, we noted (6) that MRSA was isolated from 20% of DFIs. As a reference lab for a DFI study, we received 473 pretreatment specimens, of which 91.3% grew aerobic bacteria, including 48% that grew S. aureus as one of the isolates (one-quarter of which were MRSA), and 41.6% grew anaerobes, with anaerobic gram-positive cocci the most common isolates. Dalbavancin (BI397) is new glycopeptide (4, 10) with good activity against gram-positive organisms, including MRSA, but none against gram-negative organisms (13, 19). Dalbavancin has a long elimination half-life ( 8.5 days) and has been effective in treating gram-positive SSTIs (9, 18) with a two-dose regimen. For DFIs, an antimicrobial agent with a long half-life, especially one administered once weekly, seems to be advantageous. Specimens were obtained from patients with clinical infection who had not received antimicrobials within 48 h and after wound debridement. To avoid bias, 329 consecutively isolated gram-positive aerobic and anaerobic organisms were selected for this study. Isolates were identified by standard criteria (12, 15) and stored in skim milk at 70 C. Frozen anaerobic cultures were subcultured twice onto brucella agar supplemented with hemin, vitamin K 1, and 5% sheep blood (Anaerobe Systems, Morgan Hill, CA) to ensure purity and good growth. Aerobic strains were subcultured to Trypticase soy blood agar. Susceptibility testing was performed according to CLSI (formerly NCCLS) standards M11-A6 (17) and M7-A6 (16). * Corresponding author. Mailing address: Alden Research Laboratory, 2021 Santa Monica Blvd., no. 740 East, Santa Monica, CA 90404. Phone: (310) 315-1511. Fax: (310) 315-3662. E-mail: ejcgmd@aol.com. The types and numbers of strains tested are shown in Table 1. Laboratory-standard reference powders were either obtained from their manufacturers or purchased from Sigma Chemicals (St. Louis, MO). The MICs for anaerobes were determined by the agar dilution method using brucella agar supplemented with hemin, vitamin K 1, and 5% laked sheep blood. Antimicrobial agents were reconstituted according to the manufacturers instructions. Serial twofold dilutions of dalbavancin were prepared at 100-fold the final concentration in dimethyl sulfoxide on the day of the test and added to the agar medium at a dilution of 1:100. The other antimicrobial agents were diluted and added according to the CLSI procedure (17). The agar plates were inoculated with a Steers replicator (Craft Machine Inc., Chester, PA) with an inoculum of 10 5 CFU/spot, incubated in an anaerobic chamber (Anaerobe Systems) at 37 C for 44 to 48 h, and then examined. Control strains (Bacteroides fragilis ATCC 25285, the newly proposed Clostridium difficile ATCC 70057, and S. aureus ATCC 29213) were tested simultaneously. Aerobic organisms were tested by the broth microdilution method using cation-adjusted Mueller-Hinton broth, with 2.5% lysed horse blood supplementation for the streptococci and corynebacteria. Dalbavancin was tested separately in dryformat trays prepared by TREK Diagnostics (Cleveland, OH) and provided by Vicuron (now Pfizer, Inc., New York, NY). The trays containing the remaining antimicrobials were prepared in house with serial twofold dilutions of test drugs using the Quick-Spense apparatus (Sandy Springs Instrument Co., Germantown, MD). Daptomycin tests were supplemented with additional Ca 2 to 50 mg/liter. The trays were stored at 70 C until used. Enterococcus faecalis ATCC 29212 and S. aureus ATCC 29213 were tested simultaneously. The in vitro activities of dalbavancin and 12 comparator agents are shown in Table 1. Dalbavancin had an MIC 90 of 0.125 g/ml against methicillin-susceptible S. aureus (MSSA) and MRSA isolates. Other MIC 90 s for MSSA and MRSA, respectively, were 0.5 and 1 g/ml for vancomycin, 4 and 4 g/ml for linezolid, 0.5 and 0.5 g/ml for daptomycin, and 2875
2876 NOTES ANTIMICROB. AGENTS CHEMOTHER. TABLE 1. In vitro activities of dalbavancin and 12 comparator antimicrobial agents against 209 aerobic and 120 anaerobic gram-positive organisms Aerobes MSSA (43) Dalbavancin 0.06 0.25 0.125 0.125 Vancomycin 0.25 1 0.5 0.5 Linezolid 2 8 4 4 Daptomycin 0.06 1 0.5 0.5 Meropenem 0.06 0.5 0.06 0.125 Imipenem 0.06 0.25 0.06 0.06 Piperacillin-tazobactam 0.125 4 0.5 2 Penicillin 0.06 8 8 8 Amoxicillin-clavulanate 0.06 2 0.5 1 Levofloxacin 0.06 8 0.125 0.25 Clindamycin 0.06 8 0.125 0.25 Cefotetan 2 16 8 8 Oxacillin 0.25 1 0.25 0.25 MRSA (60) Dalbavancin 0.06 0.5 0.125 0.125 Vancomycin 0.5 1 0.5 1 Linezolid 2 8 4 4 Daptomycin 0.25 1 0.5 0.5 Meropenem 0.06 8 4 8 Imipenem 0.06 8 1 8 Piperacillin-tazobactam 1 32 32 32 Penicillin 0.25 8 8 8 Amoxicillin-clavulanate 1 8 8 8 Levofloxacin 0.125 8 8 8 Clindamycin 0.125 8 8 8 Cefotetan 16 32 32 32 Oxacillin 4 4 4 4 Staphylococcus spp., coagulase-negative (20) a Dalbavancin 0.016 2 0.125 0.25 Vancomycin 0.5 1 1 1 Linezolid 1 4 2 4 Daptomycin 0.25 1 0.5 1 Meropenem 0.06 8 0.125 4 Imipenem 0.06 0.25 0.06 0.125 Piperacillin-tazobactam 0.125 32 0.5 16 Penicillin 0.06 8 8 8 Amoxicillin-clavulanate 0.06 8 0.125 4 Levofloxacin 0.125 8 0.25 8 Clindamycin 0.06 8 0.125 1 Cefotetan 8 32 16 32 Oxacillin 0.25 4 0.25 4 Streptococcus agalactiae (24) Dalbavancin 0.03 0.25 0.06 0.125 Linezolid 1 2 2 2 Daptomycin 0.25 0.5 0.25 0.5 Meropenem 0.06 0.06 0.06 0.06 Imipenem 0.06 0.06 0.06 0.06 Piperacillin-tazobactam 0.125 0.125 0.125 0.125 Penicillin 0.06 0.06 0.06 0.06 Amoxicillin-clavulanate 0.06 0.06 0.06 0.06 Levofloxacin 0.25 0.5 0.5 0.5 Clindamycin 0.06 8 0.06 0.06 Cefotetan 4 8 4 8 Beta-hemolytic Streptococcus spp., other (22) b Dalbavancin 0.016 0.125 0.06 0.125 Vancomycin 0.125 0.5 0.25 0.25 Linezolid 1 4 2 2 Daptomycin 0.06 0.25 0.06 0.06 Continued on following page
VOL. 50, 2006 NOTES 2877 TABLE 1 Continued Meropenem 0.06 0.06 0.06 0.06 Imipenem 0.06 0.06 0.06 0.06 Piperacillin-tazobactam 0.125 0.125 0.125 0.125 Penicillin 0.06 0.06 0.06 0.06 Amoxicillin-clavulanate 0.06 0.06 0.06 0.06 Levofloxacin 0.25 8 0.5 1 Clindamycin 0.06 8 0.125 0.25 Cefotetan 1 4 2 2 Corynebacterium amycolatum (20) Dalbavancin 0.06 1 0.125 0.25 Linezolid 0.25 0.5 0.5 0.5 Daptomycin 0.06 0.25 0.06 0.25 Meropenem 0.06 8 0.5 4 Imipenem 0.06 8 0.125 8 Piperacillin-tazobactam 0.125 32 4 32 Penicillin 0.06 8 1 8 Amoxicillin-clavulanate 0.06 8 1 8 Levofloxacin 0.06 8 4 8 Clindamycin 0.25 8 8 8 Cefotetan 2 32 32 32 Corynebacterium spp. (20) c Dalbavancin 0.03 1 0.25 1 Linezolid 0.125 1 0.5 1 Daptomycin 0.06 0.5 0.125 0.5 Meropenem 0.06 8 0.25 8 Imipenem 0.06 8 0.25 8 Piperacillin-tazobactam 0.125 32 32 32 Penicillin 0.06 8 8 8 Amoxicillin-clavulanate 0.06 8 8 8 Levofloxacin 0.125 8 8 8 Clindamycin 2 8 8 8 Cefotetan 2 32 32 32 Anaerobes Clostridium spp. (20) d Dalbavancin 0.015 8 0.03 2 Vancomycin 0.25 8 0.5 1 Daptomycin 0.25 16 1 4 Linezolid 1 8 2 8 Imipenem 0.03 4 0.06 2 Meropenem 0.03 4 0.03 2 Amoxicillin-clavulanate 0.03 1 0.03 0.5 Penicillin 0.03 4 0.125 2 Piperacillin-tazobactam 0.03 8 0.03 4 Cefotetan 0.06 32 1 2 Levofloxacin 0.25 8 0.25 8 Clindamycin 0.03 32 1 16 Metronidazole 0.03 1 0.5 1 Peptoniphilus asaccharolyticus (20) Dalbavancin 0.03 0.25 0.06 0.125 Vancomycin 0.125 0.5 0.125 0.25 Daptomycin 0.03 1 0.03 0.25 Imipenem 0.03 0.06 0.03 0.03 Meropenem 0.03 0.06 0.03 0.06 Amoxicillin-clavulanate 0.03 0.5 0.03 0.25 Penicillin 0.03 0.5 0.06 0.25 Piperacillin-tazobactam 0.03 0.5 0.03 0.125 Cefotetan 0.25 4 0.5 1 Levofloxacin 2 8 8 8 Continued on following page
2878 NOTES ANTIMICROB. AGENTS CHEMOTHER. TABLE 1 Continued Clindamycin 0.03 32 0.25 32 Metronidazole 0.125 2 1 2 Finegoldia magna (29) Dalbavancin 0.015 0.125 0.06 0.125 Vancomycin 0.125 0.5 0.25 0.5 Daptomycin 0.125 2 0.5 1 Linezolid 0.5 2 2 2 Imipenem 0.03 0.5 0.06 0.06 Meropenem 0.03 0.125 0.06 0.06 Amoxicillin-clavulanate 0.03 0.5 0.25 0.25 Penicillin 0.03 0.5 0.125 0.25 Piperacillin-tazobactam 0.03 0.5 0.125 0.125 Cefotetan 0.125 4 1 2 Levofloxacin 0.25 8 8 8 Clindamycin 0.03 32 0.5 16 Metronidazole 0.125 2 0.5 1 Anaerococcus prevotii (20) Dalbavancin 0.015 0.25 0.03 0.125 Vancomycin 0.06 0.5 0.25 0.25 Daptomycin 0.03 1 0.125 0.125 Imipenem 0.03 0.06 0.03 0.03 Meropenem 0.03 0.06 0.03 0.03 Amoxicillin-clavulanate 0.03 0.125 0.03 0.125 Penicillin 0.03 0.5 0.04 0.125 Piperacillin-tazobactam 0.03 0.25 0.03 0.06 Cefotetan 0.03 2 0.25 0.05 Levofloxacin 0.5 8 8 8 Clindamycin 0.03 32 0.125 32 Metronidazole 0.125 1 0.5 1 Other anaerobic gram-positive cocci (31) e Dalbavancin 0.015 0.25 0.03 0.125 Vancomycin 0.06 0.5 0.25 0.5 Daptomycin 0.03 1 0.25 1 Imipenem 0.03 0.06 0.03 0.06 Meropenem 0.03 0.25 0.06 0.25 Amoxicillin-clavulanate 0.03 0.5 0.06 0.125 Penicillin 0.03 0.5 0.06 0.25 Piperacillin-tazobactam 0.03 0.5 0.03 0.25 Cefotetan 0.03 8 0.25 2 Levofloxacin 0.125 8 2 8 Clindamycin 0.03 2 0.125 0.25 Metronidazole 0.03 2 0.25 1 a Staphylococcus epidermidis (4), S. haemolyticus (3), S. capitis (1), S. caprae (1), S. cohnii (1), S. hominis (1), S. lugdunensis (3), S. schleiferi (1), S. sciuri (2), S. simulans (2), and S. warneri (1). b Streptococcus group G (19) and S. pyogenes (3). c Corynebacterium group F-1 (1), C. glucuronolyticum (1), C. jeikeium (10), C. simulans (1), C. striatum (5), C. urealyticum (1), and Corynebacterium sp. (1). d Clostridium cadaveris (4), C. clostridioforme (3), C. innocuum (1), C. perfringens (10), C. sphenoides (1), and C. subterminale (1). e Peptostreptococcus anaerobius (9), Peptoniphilus harei (4), P. vaginalis (7), Micromonas micros (7), and Anaerococcus tetradius (4). 0.25 and 8 g/ml for clindamycin. The MIC of dalbavancin for one of three strains of Staphylococcus haemolyticus was 2 g/ml. To determine if this was peculiar to the species, we tested 16 additional strains and found the range to be 0.06 to 0.125 g/ml. Against Streptococcus agalactiae, Streptococcus pyogenes, and group G beta-hemolytic streptococci, dalbavancin had an MIC 90 of 0.125 g/ml. Dalbavancin inhibited Corynebacterium amycolatum and Corynebacterium jeikeium strains at 1 g/ml and was active against 120 anaerobes (Clostridium perfringens, other clostridia, Peptoniphilus asaccharolyticus, Finegoldia magna, Anaerococcus prevotii, and other anaerobic gram-positive cocci), with MIC 90 sof 0.125 g/ml. Dalbavancin was generally at least twofold more active than vancomycin and daptomycin and fourfold more active than linezolid against MRSA, MSSA, and coagulase-negative staphylococcus isolates. Most ( 50%) of the MRSA isolates were resistant to clindamycin (MICs of 8 g/ml). In vitro studies on dalbavancin have focused on aerobic gram-positive isolates that come from a variety of clinical
VOL. 50, 2006 NOTES 2879 sources, including thousands of European and American staphylococcal isolates (11, 13, 19). MIC 90 s for S. aureus and coagulase-negative isolates, whether susceptible or resistant to methicillin, were in most cases 0.06 g/ml; somewhat lower MICs were observed for streptococci. Higher MICs were seen only with some vancomycin-resistant E. faecalis and E. faecium strains. Goldstein et al. (5) studied 238 anaerobes and 52 Corynebacterium species and noted that dalbavancin was 1 to 3 dilutions more active than vancomycin against most strains. Recent studies (7; D. M. Citron, E. J. C. Goldstein, B. A. Lipsky, A. Tice, D. E. Morgenstern, and M. A. Abramson, 45th Intersci. Conf. Antimicrob. Agents Chemother., abstr. E-1440, 2005) have suggested that the source of isolates may be an important factor that influences the activity of agents, noting different susceptibilities of anaerobic gram-positive cocci isolated from DFIs compared to those from intra-abdominal infections. Our study is unique in that it examined only strains isolated from pretreatment DFIs. We found that dalbavancin was more active against MSSA and MRSA isolates than vancomycin, linezolid, daptomycin, and clindamycin and was active against C. perfringens, other clostridia, P. asaccharolyticus, F. magna, and A. prevotii, with MIC 90 sof 0.125 g/ml. In a recent clinical comparison, dalbavancin ( 90% clinical success rate) was equivalent to linezolid in the treatment of complicated SSTIs (9) with MRSA as a baseline pathogen in 51% of patients, 23% of whom were diabetic. The bacteriology of the DFIs was not specifically elucidated. Our study showed dalbavancin to have excellent in vitro activity against the 329 gram-positive aerobic and anaerobic DFI strains tested. The in vitro data coupled with the clinical studies suggest that dalbavancin is active against a wide variety of gram-positive isolates and might provide an advantage for patient management of DFI in emergency departments, as well as both outpatient and inpatient settings. This study was sponsored in part by a grant from Vicuron Pharmaceuticals Inc. We thank Judee H. Knight and Alice E. Goldstein for various forms of assistance. REFERENCES 1. Bailey, T. S., H. M. Yu, and E. J. Rayfield. 1985. Patterns of foot examination in a diabetes clinic. Am. J. Med. 78:371 374. 2. Diederen, B. M., and J. A. Kluytmans. 2006. The emergence of infections with community-associated methicillin resistant Staphylococcus aureus. J.Infect. 52:157 168. 3. Frazee, B. W., J. Lynn, E. D. Charlebois, L. Lambert, D. Lowery, and F. Perdreau-Remington. 2005. High prevalence of methicillin-resistant Staphylococcus aureus in emergency department skin and soft tissue infections. Ann. Emerg. Med. 45:311 320. 4. Goldstein, B. P., G. Candiani, T. M. Arain, G. Romano, I. Ciciliato, M. Berti, M. Abbondi, R. Scotti, M. Mainini, and F. Ripamonti. 1995. Antimicrobial activity of MDL 63,246, a new semisynthetic glycopeptide antibiotic. Antimicrob. Agents Chemother. 39:1580 1588. 5. Goldstein, E. J. C., D. M. Citron, C. V. Merriam, Y. Warren, K. Tyrrell, and H. T. Fernandez. 2003. In vitro activities of dalbavancin and nine comparator agents against anaerobic gram-positive species and corynebacteria. Antimicrob. Agents Chemother. 47:1968 1971. 6. Goldstein, E. J. C., D. M. Citron, and C. A. Nesbit. 1996. Diabetic foot infections. Bacteriology and activity of 10 oral antimicrobial agents against bacteria isolated from consecutive cases. Diabetes Care 19:638 641. 7. Goldstein, E. J. C., D. M. Citron, Y. A. Warren, K. L. Tyrrell, C. V. Merriam, and H. Fernandez. 2006. In vitro activity of moxifloxacin against 923 anaerobes isolated from human intra-abdominal infections. Antimicrob. Agents Chemother. 50:148 155. 8. Hogan, P., T. Dall, and P. Nikolov. 2003. Economic costs of diabetes in the US in 2002. Diabetes Care 26:917 932. 9. Jauregui, L. E., S. Babazadeh, E. Seltzer, L. Goldberg, D. Krievins, M. Frederick, D. Krause, I. Satilovs, Z. Endzinas, J. Breaux, and W. O Riordan. 2005. Randomized, double-blind comparison of once-weekly dalbavancin versus twice-daily linezolid therapy for the treatment of complicated skin and skin structure infections. Clin. Infect. Dis. 41:1407 1415. 10. Jones, R. N., D. J. Biedenbach, D. M. Johnson, and M. A. Pfaller. 2001. In vitro evaluation of BI 397, a novel glycopeptide antimicrobial agent. J. Chemother. 13:244 254. 11. Jones, R. N., M. S. Stillwell, H. S. Sader, T. R. Fritsche, and B. P. Goldstein. 2006. Spectrum and potency of dalbavancin tested against 3322 gram-positive cocci isolated in the United States Surveillance Program (2004). Diagn. Microbiol. Infect. Dis. 54:149 153. 12. Jousimies-Somer, H. R., P. Summanen, D. M. Citron, E. J. Baron, H. M. Wexler, and S. M. Finegold. 2002. Wadsworth-KTL anaerobic bacteriology manual. Star Publishing, Belmont, CA. 13. Lin, G., K. Credito, L. M. Ednie, and P. C. Appelbaum. 2005. Antistaphylococcal activity of dalbavancin, an experimental glycopeptide. Antimicrob. Agents Chemother. 49:770 772. 14. Moran, G. J., R. N. Amii, F. M. Abrahamian, and D. A. Talan. 2005. Methicillin-resistant Staphylococcus aureus in community-acquired skin infections. Emerg. Infect. Dis. 11:928 930. 15. Murray, P. R., E. J. Baron, J. H. Jorgensen, M. A. Pfaller, and R. H. Yolken (ed.). 2003. Manual of clinical microbiology, 8th ed. ASM Press, Washington, D.C. 16. NCCLS. 2003. Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically. Document M7-A6. NCCLS, Wayne, Pa. 17. NCCLS. 2004. Methods for antimicrobial susceptibility testing of anaerobic bacteria. Approved standard M11-A6. NCCLS, Wayne, Pa. 18. Seltzer, E., M. B. Dorr, B. P. Goldstein, M. Perry, J. A. Dowell, and T. Henkel. 2003. Once-weekly dalbavancin versus standard-of-care antimicrobial regimens for treatment of skin and soft-tissue infections. Clin. Infect. Dis. 37:1298 1303. 19. Streit, J. M., T. R. Fritsche, H. S. Sader, and R. N. Jones. 2004. Worldwide assessment of dalbavancin activity and spectrum against over 6,000 clinical isolates. Diagn. Microbiol. Infect. Dis. 48:137 143.