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In vitro activity of trovafloxacin against ciprofloxacin-susceptible and -resistant clinical bacterial isolates and assessment of the trovafloxacin disk test
In Vitro Activity of Trovafloxacin against Ciprofloxacin-Susceptible and -Resistant Clinical Bacterial Isolates and Assessment of the Trovafloxacin Disk Test Peter C. Fuchs, Arthur L. Barry, and Steven D. Brown
A total of 4241 consecutive clinical bacterial isolates from 10 North American medical centers were tested for susceptibility to trovafloxacin. Trovafloxacin was significantly more active than ciprofloxacin against Gram-positive bacteria, Acinetobacter spp., and Stenotrophomonas maltophilia, and resistance to trovafloxacin occurred in these groups only among isolates with high-level resistance (MIC $16 mg/mL) to ciprofloxacin. With other species, the two drugs had comparable
activity. Concerns about staphylococci and Pseudomonas aeruginosa with trovafloxacin MICs of 2.0 mg/mL (the upper end of the susceptible category) are discussed. Results of trovafloxacin disk diffusion test on more than 3200 nonfastidious isolates supported the FDA-approved zone size interpretive criteria when the MIC breakpoint of #2.0 mg/mL is used to define the trovafloxacin-susceptible category. © 1999 Elsevier Science Inc.
INTRODUCTION
assess the disk diffusion interpretive criteria for this drug.
Trovafloxacin (CP99,219) is a new fluoroquinolone antimicrobial that has recently been approved for use in the United States for the treatment of a wide variety of bacterial infections (Medical Letter 1998). It has been reported to have superior antimicrobial activity compared with earlier fluoroquinolones against Gram-positive bacteria (Barry et al. 1996; Bonilla et al. 1996; Klugman et al. 1997; Urbaskova et al. 1996), some species of nonfermentative Gramnegative bacteria (Fass et al. 1996) and anaerobes (Aldridge et al. 1997). Herein we report a multicenter study designed to: 1) determine the susceptibility of consecutive clinical isolates to trovafloxacin, and 2) From The Clinical Microbiology Institute, Wilsonville, OR 97070. Address reprint requests to Dr. Peter C. Fuchs, The Clinical Microbiology Institute, 9725 SW Commerce Circle, Suite A-1, Wilsonville, OR 97070. Received 8 July, 1998; revised and accepted 29 September 1998.
DIAGN MICROBIOL INFECT DIS 1999;33:33–38 © 1999 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010
MATERIALS AND METHODS Participants Ten North American medical centers participated in this survey and are listed in the Acknowledgments.
Microorganisms Consecutive fresh clinical isolates from different patients were collected by each participating facility during the first quarter of 1997, and are listed in Table 1. Non-fastidious Gram-negative bacterial isolates were tested at the collecting laboratory; all other isolates were sent to the Clinical Microbiology Institute for testing. Bacterial identifications were performed at each participating laboratory by the standard methods currently in use at each laboratory.
0732-8893/99/$–see front matter PII S0732-8893(98)00134-5
Fuchs et al.
34 TABLE 1 Susceptibility of Clinical Isolates to Trovafloxacin MIC (mg/mL) Microorganism (No.) Acinetobacter baumanii (70) Acinetobacter sppb (36) Burkholdera cepacia (13) Citrobacter freundii (20) Enterobacter aerogenes (133) Enterobacter agglomerans (12) Enterobacter cloacae (152) Enterobacter spp.c (21) Escherichia coli (375) Klebsiella oxytoca (114) Klebsiella pneumoniae (243) Morganella morgani (77) Pasteurella multocida (16) Proteus mirabilis (111) Proteus vulgaris (23) Providencia rettgeri (13) Providencia stuartii (30) Pseudomonas aeruginosa (307) Pseudomonas fluorescens group (24) Pseudomonas spp., NOS (13) Salmonella spp., not typhi (128) Serratia marcescens (147) Serratia spp.d (11) Shigella spp. (61) Stenotrophomonas maltophilia (99) Other gram-negative bacillie (13) Enterococcus faecalis (167)
Range
50%
90%
% Susceptiblea
#0.008–.16 #0.008–.16 0.06–.16 #0.008–0.5 #0.008–.16 #0.008–0.25 #0.008–.16 #0.008–4.0 #0.008–.16 #0.008–2.0 #0.008–.16 0.015–16 #0.008–#0.008 0.015–4.0 0.03–1.0 0.12–0.5 #0.008–.16 0.03–.16 0.03–.16 #0.008–.16 #0.008–0.5 0.03–.16 0.015–0.25 #0.008–0.03 #0.03–16 #0.008–0.12 0.03–16
0.03 0.03 1.0 0.03 0.03 0.015 0.03 0.03 0.015 0.03 0.06 0.12 #0.008 0.25 0.12 0.25 2.0 0.5 0.25 0.06 0.03 0.25 0.03 0.015 0.25 0.015 0.12
8.0 16 16 0.25 0.25 0.03 0.5 2.0 0.03 0.06 1.0 1.0 #0.008 0.25 0.25 0.5 16 4.0 8.0 8.0 0.03 4.0 0.25 0.015 2.0 0.03 8.0
82.9 75.0 69.2 100 90.2 100 97.4 85.7 98.1 100 95.9 93.5 100 98.2 100 100 60.0 86.7 78.3 76.9 100 88.4 100 100 91.7 100 79.0
Antimicrobial Agents Trovafloxacin was provided as standardized powder by Pfizer Central Research, New York, NY. Ampicillin, ciprofloxacin, and penicillin G were procured from their respective U.S. manufacturers or other commercial sources. Commercially prepared disks for disk diffusion tests included trovafloxacin (10 mg) and ciprofloxacin (5 mg).
ing from 0.008 to 16 mg/mL. Breakpoint concentrations of penicillin G (streptococci) and ampicillin (Haemophilus spp.) were also tested. For disk diffusion tests, Mueller-Hinton agar was used and was supplemented with 5% defibrinated sheep blood when testing streptococci. HTM agar was used for testing Haemophilus spp. Disk diffusion tests were not performed for gonococci or anaerobes.
Quality Control Test Procedures All test procedures followed the methods published by the National Committee for Clinical Laboratory Standards (NCCLS 1997a, 1997b, 1997c). Broth microdilution tests were performed with all organisms except Neisseria gonorrhoeae, for which the agar dilution method was used with GC agar containing Isovitalex supplements. For testing streptococci the cation-adjusted Mueller-Hinton broth was supplemented with 2 to 3% lysed horse blood, and for testing Haemophilus spp. Haemophilus Test Medium (HTM) supplements were added to the medium. A broth version of Wilkins-Chalgren medium was used for testing anaerobes. Trovafloxacin and ciprofloxacin were tested as serial twofold concentrations rang-
At least one quality control strain appropriate for the clinical strains being studied was tested on each test day. The quality control strains included: Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213 (MIC only), S. aureus ATCC 25923 (disk test only), Streptococcus pneumoniae ATCC 49619, Haemophilus influenzae ATCC 49247, N. gonorrhoeae ATCC 49226, Bacteroides fragilis ATCC 25285, B. thetaiotaomicron ATCC 29741, and Eubacterium lentum ATCC 43055.
RESULTS AND DISCUSSION A total of 4241 clinical bacterial isolates were tested and the summary of their susceptibility to trova-
Trovafloxacin Activity and Disk Test Assessment
35
TABLE 1 Continued MIC (mg/mL) Microorganism (No.)
Range
50%
90%
% Susceptiblea
Enterococcus faecium (35) Enterococcus spp.f (11) Staphylococcus aureus—MRSA (86) Staphylococcus aureus—MSSA (206) Coagulase-neg staphylococci—MR (200) Coagulase-neg staphylococci—MS (104) Stomatococcus spp. (26) Streptococcus pyogenes (114) Streptococcus agalactiae (68) Streptococcus pneumoniaeg (205) Viridans streptococci (49) Other streptococcih (37) Other gram-positive bacteriai (27) Haemophilus influenzae (180) Haemophilus spp.j (63) Moraxella catarrhalis (153) Neisseria gonorrhoeae (57) Neisseria meningitidis (24) Bacteroides fragilis (38) Bacteroides thetaiotaomicron (13) Bacteroides spp.k (22) Clostridium perfringens (21) Clostridium spp.l (15) Peptostreptococcus spp.m (19) Prevotella spp.n (30) Other anaerobeso (9)
0.125–16 0.06–.16 #0.008–8.0 #0.008–1.0 #0.008–.16 #0.008–.16 #0.008–4.0 0.06–0.5 0.06–8.0 0.03–0.12 #0.008–4.0 #0.008–0.5 #0.008–8.0 #0.008–0.12 #0.008–0.25 #0.008–0.015 #0.002–0.015 #0.008–#0.008 0.12–8.0 0.25–4.0 0.12–4.0 0.12–0.5 0.03–4.0 0.12–8.0 0.5–16 0.12–1.0
8.0 0.12 1.0 0.015 0.25 0.03 0.25 0.06 0.12 0.06 0.06 0.06 0.12 #0.008 0.015 #0.008 0.004 #0.008 0.5 0.5 0.25 0.25 0.12 0.5 1.0 0.25
16 2.0 2.0 0.03 8.0 0.12 4.0 0.12 0.25 0.06 0.12 0.25 8.0 #0.008 0.03 0.015 0.008 #0.008 4.0 1.0 4.0 0.25 1.0 8.0 4.0
34.3 90.9 93.0 100 77.5 96.2 88.5 100 98.5 100 98.0 100 76 100 100 100 100 100 73.7 92.3 86.4 100 93.3 89.5 86.7 100
Susceptible to #2.0 mg/mL (FDA-approved breakpoint) Includes: 7 A. lwoffii, 17 A. anitratus, and 12 Acinetobacter spp., NOS. c Includes: 5 E. amnigenus, 1 E. gergoviae, 1 E. sakazaki, and 14 Enterobacter spp., NOS. d Includes: 7 S. liquefaciens, and 4 Serratia spp., NOS. e Includes: 6 Aeromonas spp., NOS, 1 Alcaligenes spp., NOS, 1 Flavobacterium sp., 1 Hafnia alvei, 2 Kluyvera spp., NOS, 1 Proteus penneri, and 1 Yersinia enterocolitica. f Includes: 2 E. avium, 3 E. casseliflavus, 1 E. cecorum, 4 E. durans, and 1 E. raffinosus. g Includes: 77 strains not susceptible to penicillin. h Includes: 7 S. bovis, 1 S. intermedius, 5 S. mitis, 2 S. milleri, 1 S. mutans, 4 S. sanguis, 4 group C, 1 group F, 6 group G, and 6 Streptococcus spp., NOS. i Includes: 1 Aerococcus viridans, 1 Bacillus sp., NOS, 1 Brevibacterium casei, 5 Corynebacterium jeikeium, 8 Corynebacterium spp., NOS, 2 Gemella spp., 1 Lactobacillus casei, 3 Leuconostoc spp., NOS, 2 Listeria monocytogenes, 1 Micrococcus sp., and 2 Pediococcus pentosaceus. j Includes: 2 H. aphrophilus, 2 H. haemolyticus, 2 H. parahaemolyticus, 20 H. parainfluenzae, and 37 Haemophilus spp., NOS. k Includes: 2 B. cacae, 3 B. distasonis, 3 B. fragilis group, 1 B. ovatus, 5 Bacteroides spp., NOS, 4 B. uniformis, and 4 B. vulgatus. l Includes: 1 C. bifermentans, 1 C. butyricum, 1 C. difficile, 3 C. septicum, 1 C. sporogenes, 1 C. tertium, and 7 Clostridium spp., NOS. m Includes: 3 P. anaerobius, 5 P. asaccharolyticus, and 11 Peptostreptococcus spp., NOS. n Includes: 7 P. bivia, 3 P. buccae, 1 P. intermedia, 1 P. loescheii, 7 P. melaninogenica, and 11 Prevotella spp., NOS. o Includes: 1 Eubacterium lentum, 2 Fusobacterium necrophorum, 1 Fusobacterium nucleatum, 1 Fusobacterium sp., NOS, 3 Proprionibacterium acnes, and 1 Veillonella sp., NOS. a
b
floxacin is provided in Table 1. Of the 3614 nonfastidious isolates that grew aerobically, 92.5% were susceptible to trovafloxacin and 85.2% were susceptible to ciprofloxacin. The trovafloxacin susceptibility of ciprofloxacin-susceptible, ciprofloxacin-intermediate, and ciprofloxacin-resistant (low level and high level) strains are summarized in Table 2. Trovafloxacin was more active against Grampositive isolates than ciprofloxacin. Although the trovafloxacin MICs for ciprofloxacin-resistant strains were higher than those for ciprofloxacin-susceptible strains, trovafloxacin resistance was seen only
among those strains with high-level resistance to ciprofloxacin (MIC $16 mg/mL) (Table 2). Similar cross-resistance with enterococci and methicillinresistant S. aureus (MRSA) has been reported previously (Bonilla et al. 1996). With the exception of two species, nonfastidious Gram-negative bacteria were equivalently susceptible to both trovafloxacin and ciprofloxacin. The exceptions were Stenotrophomonas maltophilia and Acinetobacter spp., which showed greater susceptibility to trovafloxacin. Fass et al. (1996) also showed increased susceptibility of those species to trovafloxa-
Fuchs et al.
36 TABLE 2 Susceptibility of Ciprofloxacin-Susceptible and -Resistant Strains to Trovafloxacin Microorganisma (No. tested) Staphylococcus spp. (596)
Enterococcus spp. (213)
Streptococcus spp. (473)
Pseudomonas aeruginosa (307)
Acinetobacter spp. (106)
Stenotrophomonas maltophilia (99)
Enterobacteriaceae (1676)
Other species (127)
All organisms combined (3597)
Susceptibility to Trovafloxacinc
Ciprofloxacin Categoryb
Number (%)
S (%)
I (%)
R (%)
S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR
409 (68.6) 12 (2.0) 34 (5.7) 141 (27.7) 129 (60.5) 10 (4.7) 6 (2.8) 68 (31.9) 453 (95.8) 15 (3.2) 3 (0.6) 2 (0.4) 264 (86.0) 20 (6.5) 17 (5.5) 6 (2.0) 66 (62.3) 5 (4.7) 3 (2.8) 32 (30.2) 43 (43.4) 27 (27.3) 20 (20.2) 9 (9.1) 1588 (94.7) 24 (1.4) 19 (1.1) 45 (2.8) 107 (84.3) 6 (5.5) 9 (8.3) 5 (4.6) 3062 (85.1) 119 (3.3) 111 (3.1) 305 (8.5)
409 (100) 12 (100) 34 (100) 86 (61.0) 129 (100) 10 (100) 6 (100) 9 (13.2) 453 (100) 15 (100) 3 (100) 0 262 (99.2) 8 (40.0) 0 0 66 (100) 5 (100) 3 (100) 11 (34.4) 43 (100) 27 (100) 19 (95.0) 1 (11.1) 1581 (99.6) 16 (66.7) 1 (5.3) 3 (7.1) 104 (97.2) 3 (50.0) 4 (44.4) 1 (20.0) 3050 (99.6) 96 (80.7) 70 (63.1) 111 (36.4)
0 0 0 22 (15.6) 0 0 0 23 (33.8) 0 0 0 0 2 (0.8) 9 (45.0) 4 (23.5) 0 0 0 0 7 (21.9) 0 0 1 (5.0) 3 (33.3) 7 (0.4) 6 (25.0) 5 (26.3) 3 (7.1) 3 (2.8) 2 (33.3) 2 (22.2) 0 12 (0.4) 17 (14.3) 12 (10.8) 58 (19.0)
0 0 0 33 (23.4) 0 0 0 36 (52.9) 0 0 0 2 (100) 0 3 (15.0) 13 (76.5) 6 (100) 0 0 0 14 (43.8) 0 0 0 5 (55.6) 0 2 (8.3) 13 (68.4) 39 (85.7) 0 1 (16.7) 3 (33.3) 4 (80.0) 0 6 (5.0) 29 (26.1) 136 (44.6)
a
Excludes data with Haemophilus spp., Moraxella catarrhalis, Neisseria spp., and anaerobic bacteria that are listed in Table 1. Ciprofloxacin susceptibility categories: S, susceptible (MIC 2 #1.0 mg/mL); I, intermediate (MIC, 2.0 mg/mL); LLR, low-level resistance (MIC 24.0 2 8.0 mg/mL); HLR, high-level resistance (MIC $16 mg/mL). c Trovafloxacin breakpoint approved by FDA: S, #2.0 mg/mL; I, 4.0 mg/mL; R, $8.0 mg/mL. b
cin. For these two species, trovafloxacin resistance was found only among strains with high-level ciprofloxacin resistance (Table 2). Fastidious gram-negative bacteria were all highly susceptible to trovafloxacin and ciprofloxacin. No ciprofloxacin-resistant gonococci were encountered in this survey, but a previous report has indicated significantly higher trovafloxacin MICs for such isolates (Jones et al. 1997). Of 167 anaerobe isolates tested, 145 (89%) were susceptible to trovafloxacin at #2.0 mg/mL. For some species such as B. fragilis and Peptostreptococcus spp., the MIC 50s and MIC 90s were two- to fourfold higher than those reported by Aldridge et al. (1997).
Because the methods used in both studies are the same, the reasons for these differences are speculative. The current FDA-approved susceptible MIC breakpoint for trovafloxacin is #2.0 mg/mL. The Cmax of trovafloxacin has a linear and proportional relationship to dose. A single 200 mg oral dose of trovafloxacin has been reported to yield a mean Cmax of 2.2 mg/mL to 2.9 mg/mL (Dalvie et al. 1997; Teng et al. 1997). However, significantly higher concentrations occurred in alveolar macrophages and lung epithelial lining cells (Andrews et al. 1997), and concentrations in non-inflamed cerebrospinal fluid averaged 25% that of serum concentrations (Cutler et
Trovafloxacin Activity and Disk Test Assessment
37
FIGURE 1 Scattergram of trovafloxacin MICs and disk diffusion zone diameters with 3223 nonfastidious clinical isolates excluding streptococci. Horizontal and vertical lines represent FDA-approved MIC and zone diameter breakpoints, respectively. Correlation coefficient 5 0.85; slope 5 20.31.
al. 1997). The pharmacokinetics of alatrofloxacin, the intravenous pro-drug form of trovafloxacin, is very similar to that of the oral drug with a mean Cmax of 2.3 6 0.5 and 4.3 6 1.0 mg/mL after a 200and 300-mg dose, respectively (Vincent et al. 1997). Thus, the #2.0 mg/mL susceptible MIC breakpoint can be justified from a pharmacological viewpoint. The propensity of certain species (notably enterococci, MRSA and P. aeruginosa) to develop resistance to fluoroquinolones over time when exposed to these drugs presents a concern with respect to the trovafloxacin susceptible breakpoint of #2.0 mg/mL. For example, 14% of the trovafloxacin-susceptible MRSA strains in this study had trovafloxacin MICs of 2.0 mg/mL, of which 91% (10 of 11) had ciprofloxacin MICs .16 mg/mL. Likewise, 11% of P. aeruginosa strains susceptible to trovafloxacin required 2 mg/mL for inhibition. The in vivo response of infections by such organisms to treatment with trovafloxacin as a single agent, and the likelihood of development of trovafloxacin resistance in such cases, are currently unknown. It is, therefore, noteworthy that for both MRSA and P. aeruginosa current FDA guidelines indicate therapy with vancomycin and combination therapy, respectively. A scattergram of trovafloxacin MICs and disk diffusion test zone diameters is provided in Figure 1 for
nonfastidious organisms excluding streptococci. We applied the FDA-approved breakpoints of S 5 #2.0 mg/mL and $17 mm, I 5 4.0 mg/mL and 14 2 16 mm, and R 5 $8.0 mg/mL and #13 mm for the dilution and disk diffusion tests, respectively. This resulted in 3 (0.1%) very major discrepancies, 17 (0.5%) major discrepancies, and 147 (4.5%) minor discrepancies. For the control drug, ciprofloxacin, the corresponding discrepancy rates were 0.3%, 0.6%, and 6.1%, respectively. The data from this study support the FDA-approved trovafloxacin zone diameter interpretive criteria when using #2.0 mg/mL susceptible MIC breakpoint. This study was made possible by a grant from Pfizer, Inc., New York, NY. We are grateful to the following individuals who participated in the collection of these data: T. Cleary, U. of Miami Medical Center, Miami, FL; D. Hardy, U. of Rochester, Medical Center, Rochester, NY; J. Hindler, UCLA Medical Center, Los Angeles, CA; S. Jenkins, Carolinas Medical Center, Charlotte, NC; J. McLaughlin, U. of New Mexico Medical Center, Albuquerque, NM; M. Pfaller, U. of Iowa College of Medicine, Iowa City, IA; R. Rennie, U. Alberta Hospital, Edmonton, Alberta, Canada; D. Sahm, Barnes Jewish Hospital, St. Louis, MO; K. Waites, U. of Alabama Medical Center, Birmingham, AL; and J. Washington, The Cleveland Clinic Foundation, Cleveland, OH.
38
Fuchs et al.
REFERENCES Aldridge KE, Ashcraft D, Bowman DA (1997) Comparative in vitro activities of trovafloxacin (CP99,219) and other antimicrobials against clinically significant anaerobes. Antimicrob Agents Chemother 41:484–487. Andrews JM, Honeybourne D, Brenwald NP, Bannerjee D, Iredale M, Cunningham B, Wise R (1997) Concentrations of trovafloxacin in bronchial mucosa, epithelial lining fluid, alveolar macrophages and serum after administration of single or multiple oral doses to patients undergoing fibre-optic bronchoscopy. J Antimicrob Chemother 39:797–802. Barry AL, Fuchs PC, Brown SD (1996) In vitro activities of five fluoroquinolone compounds against strains of Streptococcus pneumoniae with resistance to other antimicrobial agents. Antimicrob Agents Chemother 40:2431–2433. Bonilla HF, Zarins LT, Bradley SF, Kauffman CA (1996) Susceptibility of ciprofloxacin-resistant staphylococci and enterococci to trovafloxacin. Diagn Microbiol Infect Dis 26:17–21. Cutler NR, Vincent J, Jhee SS, Teng R, Wardle T, Lucas G, Dogolo LC, Sramek JJ (1997) Penetration of trovafloxacin into cerebrospinal fluid in humans following intravenous infusion of alatrofloxacin. Antimicrob Agents Chemother 41:1298–1300. Dalvie DK, Khosla N, Vincent J (1997) Excretion and metabolism of trovafloxacin in humans. Drug Metab Dispos 25:423–427. Fass RJ, Barnishan J, Solomon MC, Ayers LW (1996) In vitro activities of quinolones, beta-lactams, tobramycin and trimethoprim-sulfamethoxazole against nonfermentative gram-negative bacilli. Antimicrob Agents Chemother 40:2431–2433. Jones RN, Barrett MS, Deguchi T (1997) Antimicrobial ac-
tivity of trovafloxacin against ciprofloxacin-susceptible and -resistant Neisseria gonorrhoeae. Interpretive criteria and comparison with Etest results. Diagn Microbiol Infect Dis 28:193–200. Klugman KP, Gootz TD (1997) In-vitro and in-vivo activity of trovafloxacin against Streptococcus pneumoniae. J Antimicrob Chemother 39(suppl B):51–55. Medical Letter (1998) Trovafloxacin. Medical Letter 40:30– 31. National Committee for Clinical Laboratory Standards (1997a) Performance standards for antimicrobial disk susceptibility tests. M2–A6 NCCLS, Wayne PA. National Committee for Clinical Laboratory Standards (1997b) Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically. M7–A4. NCCLS, Wayne, PA. National Committee for Clinical Laboratory Standards (1997c) Methods for antimicrobial susceptibility testing of anaerobic bacteria. M11–A3. NCCLS, Wayne, PA. Teng R, Dogolo LC, Willavize SA, Friedman HL, Vincent J (1997) Oral bioavailability of trovafloxacin with and without food in healthy volunteers. J Antimicrob Chemother 39(suppl B):87–92. Urbaskova P, Trupl J, Hupkova H, Appelbaum PC, Jacobs MR (1996) In vitro susceptibility of pneumococci to trovafloxacin, penicillin G, and other antimicrobial agents in the Czech Republic and Slovakia. Eur J Clin Microbiol Infect Dis 15:686–688. Vincent J, Venitz J, Teng R, Baris BA, Willavize SA, Polzer RJ, Friedman HL (1997) Pharmacokinetics and safety of trovafloxacin in healthy male volunteers following administration of single doses of the prodrug alatrofloxacin. J Antimicrob Chemother 39(suppl B):75–80.
A total of 4241 consecutive clinical bacterial isolates from 10 North American medical centers were tested for susceptibility to trovafloxacin. Trovafloxacin was significantly more active than ciprofloxacin against Gram-positive bacteria, Acinetobacter spp., and Stenotrophomonas maltophilia, and resistance to trovafloxacin occurred in these groups only among isolates with high-level resistance (MIC $16 mg/mL) to ciprofloxacin. With other species, the two drugs had comparable
activity. Concerns about staphylococci and Pseudomonas aeruginosa with trovafloxacin MICs of 2.0 mg/mL (the upper end of the susceptible category) are discussed. Results of trovafloxacin disk diffusion test on more than 3200 nonfastidious isolates supported the FDA-approved zone size interpretive criteria when the MIC breakpoint of #2.0 mg/mL is used to define the trovafloxacin-susceptible category. © 1999 Elsevier Science Inc.
INTRODUCTION
assess the disk diffusion interpretive criteria for this drug.
Trovafloxacin (CP99,219) is a new fluoroquinolone antimicrobial that has recently been approved for use in the United States for the treatment of a wide variety of bacterial infections (Medical Letter 1998). It has been reported to have superior antimicrobial activity compared with earlier fluoroquinolones against Gram-positive bacteria (Barry et al. 1996; Bonilla et al. 1996; Klugman et al. 1997; Urbaskova et al. 1996), some species of nonfermentative Gramnegative bacteria (Fass et al. 1996) and anaerobes (Aldridge et al. 1997). Herein we report a multicenter study designed to: 1) determine the susceptibility of consecutive clinical isolates to trovafloxacin, and 2) From The Clinical Microbiology Institute, Wilsonville, OR 97070. Address reprint requests to Dr. Peter C. Fuchs, The Clinical Microbiology Institute, 9725 SW Commerce Circle, Suite A-1, Wilsonville, OR 97070. Received 8 July, 1998; revised and accepted 29 September 1998.
DIAGN MICROBIOL INFECT DIS 1999;33:33–38 © 1999 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010
MATERIALS AND METHODS Participants Ten North American medical centers participated in this survey and are listed in the Acknowledgments.
Microorganisms Consecutive fresh clinical isolates from different patients were collected by each participating facility during the first quarter of 1997, and are listed in Table 1. Non-fastidious Gram-negative bacterial isolates were tested at the collecting laboratory; all other isolates were sent to the Clinical Microbiology Institute for testing. Bacterial identifications were performed at each participating laboratory by the standard methods currently in use at each laboratory.
0732-8893/99/$–see front matter PII S0732-8893(98)00134-5
Fuchs et al.
34 TABLE 1 Susceptibility of Clinical Isolates to Trovafloxacin MIC (mg/mL) Microorganism (No.) Acinetobacter baumanii (70) Acinetobacter sppb (36) Burkholdera cepacia (13) Citrobacter freundii (20) Enterobacter aerogenes (133) Enterobacter agglomerans (12) Enterobacter cloacae (152) Enterobacter spp.c (21) Escherichia coli (375) Klebsiella oxytoca (114) Klebsiella pneumoniae (243) Morganella morgani (77) Pasteurella multocida (16) Proteus mirabilis (111) Proteus vulgaris (23) Providencia rettgeri (13) Providencia stuartii (30) Pseudomonas aeruginosa (307) Pseudomonas fluorescens group (24) Pseudomonas spp., NOS (13) Salmonella spp., not typhi (128) Serratia marcescens (147) Serratia spp.d (11) Shigella spp. (61) Stenotrophomonas maltophilia (99) Other gram-negative bacillie (13) Enterococcus faecalis (167)
Range
50%
90%
% Susceptiblea
#0.008–.16 #0.008–.16 0.06–.16 #0.008–0.5 #0.008–.16 #0.008–0.25 #0.008–.16 #0.008–4.0 #0.008–.16 #0.008–2.0 #0.008–.16 0.015–16 #0.008–#0.008 0.015–4.0 0.03–1.0 0.12–0.5 #0.008–.16 0.03–.16 0.03–.16 #0.008–.16 #0.008–0.5 0.03–.16 0.015–0.25 #0.008–0.03 #0.03–16 #0.008–0.12 0.03–16
0.03 0.03 1.0 0.03 0.03 0.015 0.03 0.03 0.015 0.03 0.06 0.12 #0.008 0.25 0.12 0.25 2.0 0.5 0.25 0.06 0.03 0.25 0.03 0.015 0.25 0.015 0.12
8.0 16 16 0.25 0.25 0.03 0.5 2.0 0.03 0.06 1.0 1.0 #0.008 0.25 0.25 0.5 16 4.0 8.0 8.0 0.03 4.0 0.25 0.015 2.0 0.03 8.0
82.9 75.0 69.2 100 90.2 100 97.4 85.7 98.1 100 95.9 93.5 100 98.2 100 100 60.0 86.7 78.3 76.9 100 88.4 100 100 91.7 100 79.0
Antimicrobial Agents Trovafloxacin was provided as standardized powder by Pfizer Central Research, New York, NY. Ampicillin, ciprofloxacin, and penicillin G were procured from their respective U.S. manufacturers or other commercial sources. Commercially prepared disks for disk diffusion tests included trovafloxacin (10 mg) and ciprofloxacin (5 mg).
ing from 0.008 to 16 mg/mL. Breakpoint concentrations of penicillin G (streptococci) and ampicillin (Haemophilus spp.) were also tested. For disk diffusion tests, Mueller-Hinton agar was used and was supplemented with 5% defibrinated sheep blood when testing streptococci. HTM agar was used for testing Haemophilus spp. Disk diffusion tests were not performed for gonococci or anaerobes.
Quality Control Test Procedures All test procedures followed the methods published by the National Committee for Clinical Laboratory Standards (NCCLS 1997a, 1997b, 1997c). Broth microdilution tests were performed with all organisms except Neisseria gonorrhoeae, for which the agar dilution method was used with GC agar containing Isovitalex supplements. For testing streptococci the cation-adjusted Mueller-Hinton broth was supplemented with 2 to 3% lysed horse blood, and for testing Haemophilus spp. Haemophilus Test Medium (HTM) supplements were added to the medium. A broth version of Wilkins-Chalgren medium was used for testing anaerobes. Trovafloxacin and ciprofloxacin were tested as serial twofold concentrations rang-
At least one quality control strain appropriate for the clinical strains being studied was tested on each test day. The quality control strains included: Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213 (MIC only), S. aureus ATCC 25923 (disk test only), Streptococcus pneumoniae ATCC 49619, Haemophilus influenzae ATCC 49247, N. gonorrhoeae ATCC 49226, Bacteroides fragilis ATCC 25285, B. thetaiotaomicron ATCC 29741, and Eubacterium lentum ATCC 43055.
RESULTS AND DISCUSSION A total of 4241 clinical bacterial isolates were tested and the summary of their susceptibility to trova-
Trovafloxacin Activity and Disk Test Assessment
35
TABLE 1 Continued MIC (mg/mL) Microorganism (No.)
Range
50%
90%
% Susceptiblea
Enterococcus faecium (35) Enterococcus spp.f (11) Staphylococcus aureus—MRSA (86) Staphylococcus aureus—MSSA (206) Coagulase-neg staphylococci—MR (200) Coagulase-neg staphylococci—MS (104) Stomatococcus spp. (26) Streptococcus pyogenes (114) Streptococcus agalactiae (68) Streptococcus pneumoniaeg (205) Viridans streptococci (49) Other streptococcih (37) Other gram-positive bacteriai (27) Haemophilus influenzae (180) Haemophilus spp.j (63) Moraxella catarrhalis (153) Neisseria gonorrhoeae (57) Neisseria meningitidis (24) Bacteroides fragilis (38) Bacteroides thetaiotaomicron (13) Bacteroides spp.k (22) Clostridium perfringens (21) Clostridium spp.l (15) Peptostreptococcus spp.m (19) Prevotella spp.n (30) Other anaerobeso (9)
0.125–16 0.06–.16 #0.008–8.0 #0.008–1.0 #0.008–.16 #0.008–.16 #0.008–4.0 0.06–0.5 0.06–8.0 0.03–0.12 #0.008–4.0 #0.008–0.5 #0.008–8.0 #0.008–0.12 #0.008–0.25 #0.008–0.015 #0.002–0.015 #0.008–#0.008 0.12–8.0 0.25–4.0 0.12–4.0 0.12–0.5 0.03–4.0 0.12–8.0 0.5–16 0.12–1.0
8.0 0.12 1.0 0.015 0.25 0.03 0.25 0.06 0.12 0.06 0.06 0.06 0.12 #0.008 0.015 #0.008 0.004 #0.008 0.5 0.5 0.25 0.25 0.12 0.5 1.0 0.25
16 2.0 2.0 0.03 8.0 0.12 4.0 0.12 0.25 0.06 0.12 0.25 8.0 #0.008 0.03 0.015 0.008 #0.008 4.0 1.0 4.0 0.25 1.0 8.0 4.0
34.3 90.9 93.0 100 77.5 96.2 88.5 100 98.5 100 98.0 100 76 100 100 100 100 100 73.7 92.3 86.4 100 93.3 89.5 86.7 100
Susceptible to #2.0 mg/mL (FDA-approved breakpoint) Includes: 7 A. lwoffii, 17 A. anitratus, and 12 Acinetobacter spp., NOS. c Includes: 5 E. amnigenus, 1 E. gergoviae, 1 E. sakazaki, and 14 Enterobacter spp., NOS. d Includes: 7 S. liquefaciens, and 4 Serratia spp., NOS. e Includes: 6 Aeromonas spp., NOS, 1 Alcaligenes spp., NOS, 1 Flavobacterium sp., 1 Hafnia alvei, 2 Kluyvera spp., NOS, 1 Proteus penneri, and 1 Yersinia enterocolitica. f Includes: 2 E. avium, 3 E. casseliflavus, 1 E. cecorum, 4 E. durans, and 1 E. raffinosus. g Includes: 77 strains not susceptible to penicillin. h Includes: 7 S. bovis, 1 S. intermedius, 5 S. mitis, 2 S. milleri, 1 S. mutans, 4 S. sanguis, 4 group C, 1 group F, 6 group G, and 6 Streptococcus spp., NOS. i Includes: 1 Aerococcus viridans, 1 Bacillus sp., NOS, 1 Brevibacterium casei, 5 Corynebacterium jeikeium, 8 Corynebacterium spp., NOS, 2 Gemella spp., 1 Lactobacillus casei, 3 Leuconostoc spp., NOS, 2 Listeria monocytogenes, 1 Micrococcus sp., and 2 Pediococcus pentosaceus. j Includes: 2 H. aphrophilus, 2 H. haemolyticus, 2 H. parahaemolyticus, 20 H. parainfluenzae, and 37 Haemophilus spp., NOS. k Includes: 2 B. cacae, 3 B. distasonis, 3 B. fragilis group, 1 B. ovatus, 5 Bacteroides spp., NOS, 4 B. uniformis, and 4 B. vulgatus. l Includes: 1 C. bifermentans, 1 C. butyricum, 1 C. difficile, 3 C. septicum, 1 C. sporogenes, 1 C. tertium, and 7 Clostridium spp., NOS. m Includes: 3 P. anaerobius, 5 P. asaccharolyticus, and 11 Peptostreptococcus spp., NOS. n Includes: 7 P. bivia, 3 P. buccae, 1 P. intermedia, 1 P. loescheii, 7 P. melaninogenica, and 11 Prevotella spp., NOS. o Includes: 1 Eubacterium lentum, 2 Fusobacterium necrophorum, 1 Fusobacterium nucleatum, 1 Fusobacterium sp., NOS, 3 Proprionibacterium acnes, and 1 Veillonella sp., NOS. a
b
floxacin is provided in Table 1. Of the 3614 nonfastidious isolates that grew aerobically, 92.5% were susceptible to trovafloxacin and 85.2% were susceptible to ciprofloxacin. The trovafloxacin susceptibility of ciprofloxacin-susceptible, ciprofloxacin-intermediate, and ciprofloxacin-resistant (low level and high level) strains are summarized in Table 2. Trovafloxacin was more active against Grampositive isolates than ciprofloxacin. Although the trovafloxacin MICs for ciprofloxacin-resistant strains were higher than those for ciprofloxacin-susceptible strains, trovafloxacin resistance was seen only
among those strains with high-level resistance to ciprofloxacin (MIC $16 mg/mL) (Table 2). Similar cross-resistance with enterococci and methicillinresistant S. aureus (MRSA) has been reported previously (Bonilla et al. 1996). With the exception of two species, nonfastidious Gram-negative bacteria were equivalently susceptible to both trovafloxacin and ciprofloxacin. The exceptions were Stenotrophomonas maltophilia and Acinetobacter spp., which showed greater susceptibility to trovafloxacin. Fass et al. (1996) also showed increased susceptibility of those species to trovafloxa-
Fuchs et al.
36 TABLE 2 Susceptibility of Ciprofloxacin-Susceptible and -Resistant Strains to Trovafloxacin Microorganisma (No. tested) Staphylococcus spp. (596)
Enterococcus spp. (213)
Streptococcus spp. (473)
Pseudomonas aeruginosa (307)
Acinetobacter spp. (106)
Stenotrophomonas maltophilia (99)
Enterobacteriaceae (1676)
Other species (127)
All organisms combined (3597)
Susceptibility to Trovafloxacinc
Ciprofloxacin Categoryb
Number (%)
S (%)
I (%)
R (%)
S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR S I LLR HLR
409 (68.6) 12 (2.0) 34 (5.7) 141 (27.7) 129 (60.5) 10 (4.7) 6 (2.8) 68 (31.9) 453 (95.8) 15 (3.2) 3 (0.6) 2 (0.4) 264 (86.0) 20 (6.5) 17 (5.5) 6 (2.0) 66 (62.3) 5 (4.7) 3 (2.8) 32 (30.2) 43 (43.4) 27 (27.3) 20 (20.2) 9 (9.1) 1588 (94.7) 24 (1.4) 19 (1.1) 45 (2.8) 107 (84.3) 6 (5.5) 9 (8.3) 5 (4.6) 3062 (85.1) 119 (3.3) 111 (3.1) 305 (8.5)
409 (100) 12 (100) 34 (100) 86 (61.0) 129 (100) 10 (100) 6 (100) 9 (13.2) 453 (100) 15 (100) 3 (100) 0 262 (99.2) 8 (40.0) 0 0 66 (100) 5 (100) 3 (100) 11 (34.4) 43 (100) 27 (100) 19 (95.0) 1 (11.1) 1581 (99.6) 16 (66.7) 1 (5.3) 3 (7.1) 104 (97.2) 3 (50.0) 4 (44.4) 1 (20.0) 3050 (99.6) 96 (80.7) 70 (63.1) 111 (36.4)
0 0 0 22 (15.6) 0 0 0 23 (33.8) 0 0 0 0 2 (0.8) 9 (45.0) 4 (23.5) 0 0 0 0 7 (21.9) 0 0 1 (5.0) 3 (33.3) 7 (0.4) 6 (25.0) 5 (26.3) 3 (7.1) 3 (2.8) 2 (33.3) 2 (22.2) 0 12 (0.4) 17 (14.3) 12 (10.8) 58 (19.0)
0 0 0 33 (23.4) 0 0 0 36 (52.9) 0 0 0 2 (100) 0 3 (15.0) 13 (76.5) 6 (100) 0 0 0 14 (43.8) 0 0 0 5 (55.6) 0 2 (8.3) 13 (68.4) 39 (85.7) 0 1 (16.7) 3 (33.3) 4 (80.0) 0 6 (5.0) 29 (26.1) 136 (44.6)
a
Excludes data with Haemophilus spp., Moraxella catarrhalis, Neisseria spp., and anaerobic bacteria that are listed in Table 1. Ciprofloxacin susceptibility categories: S, susceptible (MIC 2 #1.0 mg/mL); I, intermediate (MIC, 2.0 mg/mL); LLR, low-level resistance (MIC 24.0 2 8.0 mg/mL); HLR, high-level resistance (MIC $16 mg/mL). c Trovafloxacin breakpoint approved by FDA: S, #2.0 mg/mL; I, 4.0 mg/mL; R, $8.0 mg/mL. b
cin. For these two species, trovafloxacin resistance was found only among strains with high-level ciprofloxacin resistance (Table 2). Fastidious gram-negative bacteria were all highly susceptible to trovafloxacin and ciprofloxacin. No ciprofloxacin-resistant gonococci were encountered in this survey, but a previous report has indicated significantly higher trovafloxacin MICs for such isolates (Jones et al. 1997). Of 167 anaerobe isolates tested, 145 (89%) were susceptible to trovafloxacin at #2.0 mg/mL. For some species such as B. fragilis and Peptostreptococcus spp., the MIC 50s and MIC 90s were two- to fourfold higher than those reported by Aldridge et al. (1997).
Because the methods used in both studies are the same, the reasons for these differences are speculative. The current FDA-approved susceptible MIC breakpoint for trovafloxacin is #2.0 mg/mL. The Cmax of trovafloxacin has a linear and proportional relationship to dose. A single 200 mg oral dose of trovafloxacin has been reported to yield a mean Cmax of 2.2 mg/mL to 2.9 mg/mL (Dalvie et al. 1997; Teng et al. 1997). However, significantly higher concentrations occurred in alveolar macrophages and lung epithelial lining cells (Andrews et al. 1997), and concentrations in non-inflamed cerebrospinal fluid averaged 25% that of serum concentrations (Cutler et
Trovafloxacin Activity and Disk Test Assessment
37
FIGURE 1 Scattergram of trovafloxacin MICs and disk diffusion zone diameters with 3223 nonfastidious clinical isolates excluding streptococci. Horizontal and vertical lines represent FDA-approved MIC and zone diameter breakpoints, respectively. Correlation coefficient 5 0.85; slope 5 20.31.
al. 1997). The pharmacokinetics of alatrofloxacin, the intravenous pro-drug form of trovafloxacin, is very similar to that of the oral drug with a mean Cmax of 2.3 6 0.5 and 4.3 6 1.0 mg/mL after a 200and 300-mg dose, respectively (Vincent et al. 1997). Thus, the #2.0 mg/mL susceptible MIC breakpoint can be justified from a pharmacological viewpoint. The propensity of certain species (notably enterococci, MRSA and P. aeruginosa) to develop resistance to fluoroquinolones over time when exposed to these drugs presents a concern with respect to the trovafloxacin susceptible breakpoint of #2.0 mg/mL. For example, 14% of the trovafloxacin-susceptible MRSA strains in this study had trovafloxacin MICs of 2.0 mg/mL, of which 91% (10 of 11) had ciprofloxacin MICs .16 mg/mL. Likewise, 11% of P. aeruginosa strains susceptible to trovafloxacin required 2 mg/mL for inhibition. The in vivo response of infections by such organisms to treatment with trovafloxacin as a single agent, and the likelihood of development of trovafloxacin resistance in such cases, are currently unknown. It is, therefore, noteworthy that for both MRSA and P. aeruginosa current FDA guidelines indicate therapy with vancomycin and combination therapy, respectively. A scattergram of trovafloxacin MICs and disk diffusion test zone diameters is provided in Figure 1 for
nonfastidious organisms excluding streptococci. We applied the FDA-approved breakpoints of S 5 #2.0 mg/mL and $17 mm, I 5 4.0 mg/mL and 14 2 16 mm, and R 5 $8.0 mg/mL and #13 mm for the dilution and disk diffusion tests, respectively. This resulted in 3 (0.1%) very major discrepancies, 17 (0.5%) major discrepancies, and 147 (4.5%) minor discrepancies. For the control drug, ciprofloxacin, the corresponding discrepancy rates were 0.3%, 0.6%, and 6.1%, respectively. The data from this study support the FDA-approved trovafloxacin zone diameter interpretive criteria when using #2.0 mg/mL susceptible MIC breakpoint. This study was made possible by a grant from Pfizer, Inc., New York, NY. We are grateful to the following individuals who participated in the collection of these data: T. Cleary, U. of Miami Medical Center, Miami, FL; D. Hardy, U. of Rochester, Medical Center, Rochester, NY; J. Hindler, UCLA Medical Center, Los Angeles, CA; S. Jenkins, Carolinas Medical Center, Charlotte, NC; J. McLaughlin, U. of New Mexico Medical Center, Albuquerque, NM; M. Pfaller, U. of Iowa College of Medicine, Iowa City, IA; R. Rennie, U. Alberta Hospital, Edmonton, Alberta, Canada; D. Sahm, Barnes Jewish Hospital, St. Louis, MO; K. Waites, U. of Alabama Medical Center, Birmingham, AL; and J. Washington, The Cleveland Clinic Foundation, Cleveland, OH.
38
Fuchs et al.
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