The in vivo activity of olamufloxacin (HSR-903) in systemic and urinary tract infections in mice

Satoshi Yoshizumia,*, Yoshie Takahashib, Mitsuo Muratab, Haruki Domona, Nobuhiko Furuyaa, Yoshikazu Ishiia, Tetsuya Matsumotoa, Akira Ohnoa, Kazuhiro Tatedaa, Shuichi Miyazakia and Keizo Yamaguchia

a Department of Microbiology, Toho University School of Medicine, Tokyo; b Research Department, Research & Development Division, Hokuriku Seiyaku Co., Ltd, Fukui, Japan


    Abstract
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
The in vivo activity of olamufloxacin (HSR-903), a new fluoroquinolone, was evaluated and compared with ciprofloxacin, sparfloxacin and levofloxacin. Olamufloxacin was active against systemic infection in mice inoculated with both Gram-positive and -negative bacteria. Olamufloxacin had equal efficacy for experimental urinary tract infections in mice caused by Pseudomonas aeruginosa.


    Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Recently, a number of new fluoroquinolones have been developed because of their broad antimicrobial spectrum and great bactericidal activity against both Gram-positive and -negative bacteria. However, many quinolone-resistant bacteria have emerged over the past few years, the frequency of which has been increasing.1 The development of new quinolones that have activity against these resistant organisms is desirable.

Olamufloxacin (HSR-903), (S)-(–)-5-amino-7-(7-amino-5-azaspiro[2.4]hept-5-yl)-1-cyclopropyl-6-fluoro-1,4-dihydro-8-methyl-4-oxoquinoline-3-carboxylic acid methanesulphonate, is a new quinolone, synthesized by Hokuriku Seiyaku Co. Ltd (Fukui, Japan). Olamufloxacin has good in vitro activity, especially against Gram-positive bacteria.2,3 In order to study the in vitro activity of this compound we compared it with ciprofloxacin, sparfloxacin and levofloxacin.


    Materials and methods
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Antimicrobial agents and bacterial strains

The following antimicrobial agents were used in this study: olamufloxacin (Hokuriku Seiyaku Co. Ltd); ciprofloxacin (Bayer Yakuhin Ltd, Osaka, Japan); sparfloxacin (Dainippon Pharmaceutical Co. Ltd, Osaka, Japan); levofloxacin (Daiichi Pharmaceutical Co. Ltd, Tokyo, Japan).

The bacterial strains used in the study were collected from Toho University Omori hospital (Tokyo, Japan) and maintained at the Department of Microbiology, Toho University School of Medicine.

MICs were determined by the broth microdilution method recommended by the Japan Society for Chemotherapy.4

Experimental infection in mice

The experimental protocol was approved by the Ethics Review Committee for Animal Experimentation of Toho University School of Medicine.

Four-week-old male slc:ICR mice (weight, c. 20 g; SLC Japan Inc., Shizuoka, Japan) were challenged ip with a single 0.5 mL injection of bacterial suspension in 5% gastric mucin (Difco Laboratories, Detroit, MI, USA) containing 1.1 x 106 cfu/mouse (108 times the LD50) of Staphylococcus aureus (Smith), 2.0 x 107 cfu/mouse (52 times the LD50) of methicillin-resistant S. aureus (MRSA) (TUH21), 9.0 x 101 cfu/mouse (8.5 times the LD50) of Escherichia coli (C11), 5.3 x 101 cfu/mouse (53 times the LD50) of Klebsiella pneumoniae (3K25) and 1.2 x 104 cfu /mouse (72 times the LD50) of Pseudomonas aeruginosa (E7). Antibiotics were administered orally in a volume of 0.2 mL of 5% Gum arabic (Wako Pure Chemical Industries, Osaka, Japan), 1 h after injection. Serial two-fold doses of drugs were employed, using eight mice at each dose. Results were calculated as 50% effective dose (ED50), including 95% confidence limits, by the probit method5 from the survival rates on day 7 after challenge.

The therapeutic effect of olamufloxacin and other drugs in experimental urinary tract infection (UTI) were determined in a mouse model using the method of Omori et al.6 Four-week-old female slc:ICR mice (weight 15–19 g) were used for UTI caused by P. aeruginosa (KU1). Dietary intake was restricted to water for 20 h before infection. Under anaesthesia induced by im injection with a mixture of 5 mg ketamine (Sankyo, Tokyo, Japan) and 1 mg xylazine (Bayer Yakuhin Ltd) per kilogram of body weight, a polyethylene 23G catheter (Maruko, Tokyo, Japan) was introduced transurethrally to inject 0.05 mL of bacterial suspension into the bladder. The external meatus was clamped for 1 h after inoculation of bacteria. Drugs were administered orally at doses of 50, 12.5 and 3.13 mg/kg starting 20 h after infection bd for 3 days. Mice were killed 18 h after the last administration of antibiotic. The kidneys were removed and homogenized in 0.9% saline, and 0.1 mL aliquots of serial 10-fold dilutions of homogenate were plated on heart infusion agar (Eiken, Tokyo, Japan) to determine the number of viable organisms. The number of viable bacteria in the kidneys of the mice that died before the end of the experiment was estimated at 1 x 108 cfu/ kidneys, if viable bacteria were recovered from blood confirming that the infection was the cause of death. Results were expressed as the mean ± S.D. log of cfu/kidneys. Statistical analysis was performed using the Bonferroni– Dunn multiple comparison method.


    Results
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 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Efficacy against systemic infection in mice

The protective effects of olamufloxacin, ciprofloxacin, sparfloxacin and levofloxacin against systemic infection in mice are described in Table IGo. Olamufloxacin showed equal or greater efficacy against systemic infection caused by S. aureus, MRSA and E. coli compared with ciprofloxacin, sparfloxacin and levofloxacin. The activity of olamufloxacin for K. pneumoniae was comparable to those of ciprofloxacin and sparfloxacin. Olamufloxacin demonstrated efficacy for P. aeruginosa comparable to other quinolones.


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Table I. Protective effect of olamufloxacin, ciprofloxacin, sparfloxacin and levofloxacin against systemic infection in mice
 
Efficacy for UTI in mice

The therapeutic effect of olamufloxacin for UTI is presented in Table IIGo. The recovery of P. aeruginosa from kidneys of mice without treatment was 7.50 ± 1.27 cfu/ kidneys. Treatment with olamufloxacin at doses of 50 and 12.5 mg/kg led to significant reduction in the number of viable cells in kidneys compared with those of untreated mice (P < 0.01). The number of viable cells in kidneys of olamufloxacin-treated mice was equal to that of ciprofloxacin-treated mice at a dose of 50 mg/kg; however, a dose of 3.13 mg showed little therapeutic efficacy.


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Table II. Therapeutic effects of olamufloxacin and other quinolones against UTIs caused by P. aeruginosa (KU1)
 

    Discussion
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 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Olamufloxacin has a broad spectrum2,3 of activity, and we have demonstrated activity for systemic infections and UTI in mice to complement respiratory tract data reported previously.7 The in vivo activity of olamufloxacin in this study was slightly less than the in vitro activity, which could be explained by host factors or pharmacokinetics.7,8 The maximum concentration (Cmax) in plasma of olamufloxacin after a single oral 5 mg/L dose in mice was 0.32 mg/L.8 The Cmax after 50 mg/kg of olamufloxacin in mice (1.42 mg/L) was lower than that of sparfloxacin (4.38 mg/L) and levofloxacin (4.15 mg/L). The elimination half-life in plasma of olamufloxacin (2.83 h) was comparable to that of levofloxacin (1.62 h) and shorter than that of sparfloxacin (5.18 h).7 In humans, olamufloxacin showed plasma Cmax (0.86 mg/L) comparable to available quinolones and long elimination half-life (18 h) in a phase I trial following a single dose of 200 mg daily.9 In view of the difference in pharmacokinetic parameters between mice and humans, it is expected that olamufloxacin would be more active for human infection than for experimental infection in mice.


    Acknowledgments
 
We thank Dr Hideo Kato, Dr Osamu Nagata and the researchers of the Microbiology Section of Hokuriku Seiyaku Co., Ltd for their suggestions and skilful support.


    Notes
 
* Correspondence address. Research Department, Hokuriku Seiyaku Co., Ltd, 1-1 Inokuchi 37, Katsuyama, Fukui 911-8555, Japan. Tel: +81-779-88-5121; Fax: +81-779-88-3021; E-mail: satoshi.yoshizumi{at}hokuriku-seiyaku.co.jp Back


    References
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 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
1 . Yamaguchi, K., Ohno, A., Kashitani, F., Iwata, M., Shimizu, Y., Sato, S. et al. (1999). In vitro activity of 23 antimicrobial agents against 4,993 gram-positive and gram-negative bacterial strains isolated from multicenters of Japan during 1994—in vitro susceptibility surveillance. Levofloxacin Surveillance Group. Japanese Journal of Antibiotics 52, 75–92.[Medline]

2 . Takahashi, Y., Masuda, N., Otsuki, M., Miki, M. & Nishino, T. (1997). In vitro activity of HSR-903, a new quinolone. Antimicrobial Agents and Chemotherapy 41, 1326–30.[Abstract]

3 . Watanabe, A., Tokue, Y., Takahashi, H., Kikuchi, T., Kobayashi, T., Gomi, K. et al. (1999). In vitro activity of HSR-903, a new oral quinolone, against bacteria causing respiratory infections. Antimicrobial Agents and Chemotherapy 43, 1767–8.[Abstract/Free Full Text]

4 . Japanese Society for Chemotherapy. (1990). Method for the determination of minimal inhibitory concentration (MIC) of aerobic bacteria by microdilution method. Chemotherapy (Tokyo) 38, 102–5.

5 . Miller, L. C. & Tainter, M. L. (1944). Estimation of ED50 and its error by means of logarithmic probit graph paper. Proceedings of the Society for Experimental Biology and Medicine 57, 261–4.

6 . Omori, Y., Ogawa, M., Miyazaki, S. & Goto, S. (1982). Studies on therapeutic effects of three pyridonecarboxylic acid agents against experimental urinary tract infection in mice. Chemotherapy (Tokyo) 30, 1232–6.

7 . Yoshizumi, S., Domon, H., Miyazaki, S. & Yamaguchi, K. (1998). In vivo activity of HSR-903, a new fluoroquinolone, against respiratory pathogens. Antimicrobial Agents and Chemotherapy 42, 785–8.[Abstract/Free Full Text]

8 . Murata, M., Takahara, E., Nagata, O., Kato, H., Tamai, I. & Tsuji, A. (1995). Carrier-mediated tissue distribution and pharmacokinetics of HSR-903, a new quinolone. In Program and Abstracts of the Thirty-fifth Interscience Conference on Antimicrobial Agents and Chemotherapy, San Francisco, CA, 1995. Abstract F203, p. 148. American Society for Microbiology, Washington, DC.

9 . Mizuno, A., Umemura, K. & Nakashima, M. (1996). Pharmacokinetics and safety of HSR-903 in healthy volunteers. In Program and Abstracts of the Thirty-sixth Interscience Conference on Antimicrobial Agents and Chemotherapy, New Orleans, LA, 1996. Abstract F59, p. 110. American Society for Microbiology, Washington, DC.

Received 18 December 2000; returned 12 March 2001; revised 2 April 2001; accepted 6 April 2001