triaxone, cefuroxime and vancomycin (Sigma Chemical. Co., St Louis, MO, USA), amoxycillin/clavulanic acid (in a ratio of 5:1) (Beecham Research Laboratories, ...
Journal of Antimicrobial Chemotherapy (1997) 39, Suppl. B, 57–62
JAC
The in-vitro activity of trovafloxacin, a new fluoroquinolone, against Gram-positive bacteria A. M. Sefton, J. P. Maskell, A. M. Rafay, A. Whiley and J. D. Williams Department of Medical Microbiology, St Bartholomew’s and the Royal London School of Medicine and Dentistry, London E1 2AD, UK The in-vitro activity of trovafloxacin, a new quinolone, was compared with that of ciprofloxacin, erythromycin, various -lactam antibiotics and, where appropriate, clindamycin and vancomycin against a range of Gram-positive bacteria including staphylococci (n = 201), Streptococcus pneumoniae (n = 83), -haemolytic streptococci (n = 46), viridans group streptococci (n = 100), Streptococcus milleri (n = 18) and enterococci (n = 161) by an agar dilution technique. In addition, time–kill studies were performed to estimate the bactericidal activity of trovafloxacin against S. milleri and viridans group streptococci. Trovafloxacin was the most active agent tested against staphylococci. It also showed good activity, at least four-fold and usually eight- to 16-fold that of ciprofloxacin, against all the streptococci. Trovafloxacin showed good activity against vancomycin-sensitive Enterococcus faecalis and Enterococcus faecium, but was less active against the 11 isolates of vancomycin-resistant enterococci. Trovafloxacin showed comparable or superior bactericidal activity to amoxycillin against the S. milleri and viridans group streptococci tested.
milleri (n 18), Enterococcus faecalis (n 100), vancomycin-sensitive Enterococcus faecium (n 50) and vancomycin-resistant enterococci (n 11). The Oxford S. aureus (NCTC 6571) was used as a control organism.
Introduction The fluoroquinolones generally show good activity against a wide range of Gram-negative bacteria, but only modest activity against Gram-positive organisms. Trovafloxacin is a new investigational fluoroquinolone reported to show enhanced activity against Gram-positive bacteria.1–4 We compared the in-vitro activity of trovafloxacin with that of ciprofloxacin, erythromycin, -lactam antibiotics and, where appropriate, clindamycin and vancomycin against a range of Gram-positive bacteria including streptococci, staphylococci, pneumococci and enterococci. Sensitivity testing was performed using a standard agar dilution technique. In addition we looked at the comparative bactericidal activity of trovafloxacin against viridans group streptococci using time–kill studies.
Antimicrobial agents Antimicrobial agents used were trovafloxacin (Pfizer Central Research, Sandwich, UK), ciprofloxacin, erythromycin, amoxycillin, penicillin, oxacillin, cephalothin, ceftriaxone, cefuroxime and vancomycin (Sigma Chemical Co., St Louis, MO, USA), amoxycillin/clavulanic acid (in a ratio of 5:1) (Beecham Research Laboratories, Welwyn Garden City, UK) and clindamycin (Upjohn, Crawley, UK).
MICs
Materials and methods
A standard agar dilution technique was performed with a multipoint inoculator (Denley Instruments, Billingshurst, UK). A final inoculum of 104 cfu per spot was used for streptococci and enterococci, and 106 cfu for staphylococci. Iso-sensitest Agar (Unipath Ltd, Basingstoke, UK) was used for susceptibility studies throughout and was supplemented with 5% lysed horse blood (Unipath) for testing streptococci and enterococci.
All bacteria studied were recent clinical isolates which had been stored at 70°C. Bacteria studied included methicillin-sensitive Staphylococcus aureus (n 92), methicillin-resistant S. aureus (n 9), coagulase-negative staphylococci (n 100), Streptococcus pneumoniae (n 83), -haemolytic streptococci, groups A, C and G (n 46), viridans group streptococci (n 100), Streptococcus 57 © 1997 The British Society for Antimicrobial Chemotherapy
A. M. Sefton et al. All plates were, in general, incubated aerobically for 18 h at 35°C before MICs were read. However, plates for determining the susceptibility of staphylococci to oxacillin were incubated aerobically for 36 h at 30°C.
and ten-fold dilutions of each of these were prepared in peptone water. Viable counts were determined by the method of Miles et al.,5 with the plates incubated for 48 h in air at 35°C before being read.
Kill curve studies
Results
The bactericidal activity of trovafloxacin, compared with that of amoxycillin, erythromycin and clindamycin against two strains of S. milleri and six viridans group streptococci, was estimated by comparing the reduction in viable count after defined periods of exposure of bacteria to antibiotic. The viridans group streptococci comprised two isolates of Streptococcus sanguis, two isolates of Streptococcus mitis and two isolates of Streptococcus oralis. Strains were grown in Iso-Sensitest Broth (Unipath), supplemented with 2% horse serum (SR 35, Unipath), for 18 h at 35°C, and an inoculum of this was then added to 100 mL fresh Isosensitest broth supplemented with 2% horse serum alone (control) or with 2% horse serum and either amoxycillin, erythromycin, clindamycin or trovafloxacin to give a final antibiotic concentration of 4 MIC. The final bacterial concentration was 105–106 cfu/mL. The cultures were incubated at 35°C on an orbital shaker. Aliquots (1 mL) were removed at 0, 1, 4, 6 and 24 h,
MICs Table I shows the comparative in-vitro activity of the agents tested against staphylococci. Trovafloxacin was the most active agent tested against methicillin-sensitive S. aureus: it was four-fold more active than oxacillin and 16fold more active than ciprofloxacin against these organisms. All strains of methicillin-sensitive S. aureus tested were inhibited by trovafloxacin 0.12 mg/L. Trovafloxacin also showed good activity against the nine strains of methicillin-resistant S. aureus (MIC50 0.06 mg/L; MIC 90 2 mg/L) compared with ciprofloxacin (MIC50 1 mg/L; MIC90 16 mg/L). In addition, trovafloxacin was the most active agent tested against coagulase-negative staphylococci; it had an MIC50 of 0.06 mg/L and an MIC90 of 0.25 mg/L for these isolates. Table II shows the comparative in-vitro activity of trovafloxacin against streptococci. Trovafloxacin was
Table I. Comparative in-vitro activity (mg/L) of trovafloxacin against staphylococci Organism (n)
Antimicrobial agent
MIC range
MIC50
MIC90
S. aureus, methicillin-sensitive (92)
trovafloxacin ciprofloxacin erythromycin oxacillin amoxycillin–clavulanic acid cefuroxime ceftriaxone vancomycin trovafloxacin ciprofloxacin erythromycin oxacillin amoxycillin–clavulanic acid cefuroxime ceftriaxone vancomycin trovafloxacin ciprofloxacin erythromycin oxacillin amoxycillin–clavulanic acid cefuroxime ceftriaxone vancomycin
0.03–0.12 0.12–8 0.25– 64 0.12–2 0.12–8 0.25–4 1–16 1–4 0.03–2 0.5–16 0.5– 64 4– 64 8–32 8– 64 16– 64 1–2 0.007–16 0.12– 64 0.12–0.5 0.06– 64 0.03–64 0.25– 64 1– 64 1–4
0.06 1 0.5 0.25 1 2 4 2 0.06 1 64 64 16 64 64 2 0.06 0.5 0.05 0.5 1 1 8 2
0.12 2 0.5 1 4 2 4 2 2 16 64 64 32 64 64 2 0.25 2 64 32 4 16 32 4
S. aureus, methicillin-resistant (9)
Coagulase-negative staphylococci (100)
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Trovafloxacin against Gram-positive bacteria Table II. Comparative in-vitro activity (mg/L) of trovafloxacin against streptococci Organism (n)
Antimicrobial agent
S. pneumoniae (83)
trovafloxacin ciprofloxacin erythromycin penicillin G amoxycillin cephalothin cefuroxime ceftriaxone tetracycline trovafloxacin ciprofloxacin erythromycin penicillin G amoxycillin cephalothin cefuroxime ceftriaxone tetracycline trovafloxacin ciprofloxacin erythromycin clindamycin penicillin G amoxycillin cephalothin cefuroxime ceftriaxone vancomycin trovafloxacin ciprofloxacin erythromycin clindamycin penicillin G amoxycillin cephalothin cefuroxime ceftriaxone tetracycline
-Haemolytic streptococci, groups A, C and G (46)
viridans group streptococci (100)
S. milleri (18)
MIC range 0.06–0.5 0.5–8 0.003–4 0.015–1 0.015–4 0.03–16 0.015–16 0.015–4 0.25– 32 0.06–0.5 0.25–2 0.03– 8 0.007–0.06 0.015–0.25 0.06–0.5 0.007–0.25 0.015–0.25 0.025– 32 0.06–2 1–16 0.007–8 0.015– 8 0.003–0.5 0.015–1 0.015–2 0.003–1 0.007–0.5 0.5–1 0.12–0.5 0.5–4 0.007–0.06 0.06–0.12 0.007–0.5 0.015–0.5 0.03–2 0.03–1 0.03–0.5 1
approximately 16-fold more active than ciprofloxacin against S. pneumoniae, and all 83 isolates tested were inhibited by trovafloxacin 0.5 mg/L. Trovafloxacin was also between eight- and 16-fold more active than ciprofloxacin against the 46 strains of group A, C and G -haemolytic streptococci tested and also against the 100 viridans group streptococci. It was between four- and eight-fold more active than ciprofloxacin against S. milleri. Table III shows the comparative in-vitro activity of
MIC50
MIC90
0.12 2 0.06 0.03 0.03 0.25 0.03 0.03 1 0.12 1 0.06 0.015 0.015 0.12 0.007 0.03 2 0.25 4 0.03 0.03 0.03 0.06 0.25 0.03 0.06 0.15 0.25 1 0.03 0.06 0.06 0.25 0.25 0.25 0.25 1
0.25 4 2 0.03 0.06 0.5 0.12 0.06 2 0.5 1 0.06 0.015 0.015 0.25 0.015 0.03 32 0.5 8 0.06 0.06 0.12 0.25 1 0.25 0.12 1 0.5 2 0.03 0.12 0.06 0.5 0.25 0.25 0.25 1
trovafloxacin against enterococci. Trovafloxacin was the most active agent against vancomycin-sensitive E. faecalis: all isolates were inhibited by 1 mg/L. Trovafloxacin was approximately four-fold more active than ciprofloxacin and amoxycillin against these strains. Trovafloxacin also showed good activity against vancomycin-sensitive E. faecium (MIC50 0.5 mg/L; MIC90 1 mg/L). However, it was less active against the 11 isolates of vancomycin-resistant enterococci tested; three isolates were inhibited by trova59
A. M. Sefton et al. Table III. Comparative in-vitro (mg/L) activity of trovafloxacin against enterococci Organism (n)
Antimicrobial agent
MIC range
MIC50
MIC90
E. faecalis (100)
trovafloxacin ciprofloxacin erythromycin amoxycillin vancomycin trovafloxacin ciprofloxacin erythromycin amoxycillin vancomycin trovafloxacin ciprofloxacin erythromycin amoxycillin vancomycin
0.06–1 0.25–2 0.12– 64 0.25–32 0.5–2 0.03–4 0.12–32 0.12–64 0.06–32 0.5–1 0.5–32 2– 64 0.007– 64 1–64 32– 64
0.12 1 2 0.5 1 0.5 2 64 8 0.5 32 64 64 16 64
0.25 1 64 1 2 1 2 64 16 0.5 32 64 64 32 64
E. faecium (50)
Enterococci, vancomycin-resistant (11)
Figure 1. Comparative in-vitro bactericidal activity of trovafloxacin at 4 MIC against an isolate of S. milleri. , control; , amoxycillin (MIC 0.25 mg/L); , clindamycin (MIC 0.06 mg/L); , erythromycin (MIC 0.06 mg/L); , trovafloxacin (MIC 0.5 mg/L).
Figure 2. Comparative in-vitro bactericidal activity of trovafloxacin at 4 MIC against an isolate of S. sanguis. , control; , amoxycillin (MIC 0.06 mg/L); , clindamycin (MIC 0.03 mg/L); , erythromycin (MIC 0.06 mg/L); , trovafloxacin (MIC 0.5 mg/L).
floxacin 1 mg/L, but MICs for the other eight were 32 mg/L. Trovafloxacin had similar or superior in-vitro bactericidal activity compared with amoxycillin against the two strains of S. milleri and all six isolates of viridans group streptococci tested. With both isolates of S. milleri trovafloxacin achieved a 3 log reduction in viable count by 4 h. Figure 1 shows the time–kill study of one of the S.
milleri strains. Trovafloxacin achieved a 3 log reduction in viable count at 24 h with all six isolates of viridans group streptococci tested. Figure 2 shows the comparative bactericidal activity of trovafloxacin against one of the two isolates of S. sanguis: similar activity was shown against the other S. sanguis strain tested. Figure 3 shows the comparative bactericidal activity of trovafloxacin against one of the two strains of S. mitis tested: trovafloxacin also achieved a 60
Trovafloxacin against Gram-positive bacteria
Figure 3. Comparative in-vitro bactericidal activity of trovafloxacin at 4 MIC against an isolate of S. mitis. , control; , amoxycillin (MIC 0.12 mg/L); , clindamycin (MIC 0.03 mg/L); , erythromycin (MIC 0.015 mg/L); , trovafloxacin (MIC 0.25 mg/L).
Figure 4. Comparative in-vitro bactericidal activity of trovafloxacin at 4 MIC against an isolate of S. oralis. , control; , amoxycillin (MIC 0.06 mg/L); , clindamycin (MIC 0.03 mg/L); , erythromycin (MIC 0.015 mg/L); , trovafloxacin (MIC 0.25 mg/L).
2–3 log reduction in viable count at 4 h against the other isolate of S. mitis. The comparative activity against one of the two strains of S. oralis tested is shown in Figure 4. Against the other isolate of S. oralis tested, trovafloxacin achieved a 3 log reduction in viable count at 6 h.
compliance, may be sufficient for treating many infections.6 Clinical studies regarding the use of trovafloxacin in various different infections are in progress. It may prove useful as a broad-spectrum antibacterial agent and also for treating Gram-positive infections especially (but not exclusively) on people who are penicillin-allergic. Our study, for instance, showed that trovafloxacin was more bactericidal than amoxycillin against S. milleri and viridans group streptococci. Hence, it is possible that it may prove to be a useful alternative agent to amoxycillin and clindamycin for endocarditis prophylaxis of ‘at risk’ patients undergoing dental procedures.
Discussion This study showed trovafloxacin to have better in-vitro activity than ciprofloxacin against the staphylococci and streptococci, as found by others. Gooding & Jones,2 Eliopoulos et al.,1 Gootz et al.,4 and Neu & Chin3 all found trovafloxacin to be at least four-fold more active than ciprofloxacin against both S. aureus and coagulase-negative staphylococci. In addition, they found that trovafloxacin had greatly enhanced activity compared with ciprofloxacin against S. pneumoniae, -haemolytic streptococci and viridans group streptococci. We also found trovafloxacin to have good activity, approximately four times that of ciprofloxacin, against enterococci and Eliopoulos et al.,1 Gooding & Jones 2 and Gootz et al. 4 reported similar find ings. Neu & Chin,3 however, reported the reverse, although they examined fewer enterococcal isolates. While trovafloxacin shows better in-vitro activity than ciprofloxacin against Gram-positive cocci, it retains good activity against Gram-negative bacteria.2–4 In addition, it exhibits superior activity against anaerobes.3 A single-dose pharmacokinetic study in humans suggested that oncedaily dosing, which is likely to lead to improved patient
Acknowledgement The study was supported by a grant from International Pharmaceuticals Group, Pfizer Inc., New York, NY, USA.
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A. M. Sefton et al. 4. Gootz, T. D., Brighty, E., Anderson, M. A., Schnieder, B. J., Haskell, S. L., Sutcliffe, J. A. et al. (1994). In-vitro activity of CP99,219, a novel 7-(3-azabicyclo[3.1.0]hexyl)naphthyridone antimicrobial. Diagnostic Microbiology and Infectious Disease 19, 235–43. 5. Miles, A. A., Misra, S. S. & Irwin, J. O. (1938). The estimation of the bactericidal power of the blood. Journal of Hygiene (Cam bridge) 38, 732–49.
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6. Teng, R., Harris, S. C., Nix, D., Schentag, J., Foulds, G., Silber, B. M. et al. (1993). Pharmacokinetics of CP-99,219, a new antibiotic, following oral doses to healthy volunteers. In Program and Abstracts of the Thirty-Third Interscience Conference on Antimicro bial Agents and Chemotherapy, New Orleans, LA, 1993. Abstract 1512, p. 395. American Society for Microbiology, Washington, DC.
