1 Antimicrobial Research Laboratory, Department of Bacterial and Inflammatory Diseases, National Public Health Institute, Kiinamyllynkatu 13, 20521 Turku, Finland; 2 Department of Medicine, Turku University Hospital, Kiinamyllynkatu 4-8, 20520 Turku, Finland; 3 Enteric Bacteria Laboratory, Department of Bacterial and Inflammatory Diseases, National Public Health Institute, Mannerheimintie 166, 00300 Helsinki, Finland
Received 10 August 2005; returned 9 September 2005; revised 14 September 2005; accepted 19 September 2005
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Methods: We analysed the in vitro activities of 11 fluoroquinolones against 226 C. jejuni strains collected from Finnish patients between 1995 and 2000.
Results: Of all 226 C. jejuni strains, 134 (59.3%) were resistant to ciprofloxacin (MIC 4 mg/L), 1 (0.4%) was intermediately resistant (MIC = 2 mg/L) and 91 (40.3%) were ciprofloxacin-susceptible (MIC
1 mg/L). The MIC50 and MIC90 values of ciprofloxacin for the 91 ciprofloxacin-susceptible strains were 0.25 and 0.5 mg/L, respectively. The corresponding MIC50 and MIC90 values of levofloxacin were 0.25 and 0.5 mg/L, and those of moxifloxacin were 0.125 and 0.25 mg/L, these being lower than those of norfloxacin and ofloxacin. The two newer fluoroquinolones, sitafloxacin and clinafloxacin, exhibited the lowest MIC50 and MIC90 values: 0.016 and 0.064 mg/L of sitafloxacin and 0.032 and 0.125 mg/L of clinafloxacin, respectively. Sitafloxacin and clinafloxacin exhibited the lowest MIC50 and MIC90 values also for the 134 ciprofloxacin-resistant C. jejuni strains: 0.25 and 1 mg/L of sitafloxacin and 1 and 4 mg/L of clinafloxacin, respectively.
Conclusions: Of the newer fluoroquinolones presently under development, sitafloxacin is in vitro highly effective towards C. jejuni, with low MIC values also for the ciprofloxacin-resistant strains. Sitafloxacin might be a candidate for clinical trials on campylobacteriosis.
Keywords: Campylobacter spp. , drug resistance , quinolones
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The purpose of the present study was to determine the in vitro activities of various older and newer fluoroquinolones against the C. jejuni species. Of the 11 fluoroquinolones tested, ciprofloxacin, ofloxacin, norfloxacin, levofloxacin and moxifloxacin are presently on market in Finland, and in wide use all over the world. Among the newer preparations, sitafloxacin and clinafloxacin have an extended antimicrobial spectrum with a good activity against Gram-positive, Gram-negative and anaerobic pathogens, including some highly resistant strains.3 Special interest was focused here on the efficacy of sitafloxacin and clinafloxacin against ciprofloxacin-resistant C. jejuni strains.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
We included in this study a total of 226 C. jejuni strains, which were collected during the years 19952000 in the laboratory of a large private hospital in Helsinki, Finland. The strains were isolated from stool samples of patients with gastroenteritis. All of these patients had a history of travelling abroad within 2 weeks preceding their symptoms, indicating that the C. jejuni strains were of foreign origin. The countries where these strains were acquired have been described previously.1 The strains were cultured and identified by standard microbiological methods.
The mutation analysis results of the quinolone resistance determining region (QRDR) of the gyrA gene for 133 strains of the present study have been described in our previous paper.4
Susceptibility testing
The MICs for the C. jejuni strains were determined by the standard agar plate dilution method.5,6 The antimicrobials evaluated were ciprofloxacin (Bayer, Wuppertal, Germany), clinafloxacin (Pfizer, Ann Arbor, MI, USA), enrofloxacin (Bayer, Elberfeld, Germany), gatifloxacin (Grunenthal BMBH, Aachen, Germany), gemifloxacin (GlaxoSmithKline, Worthing, UK), levofloxacin (Hoechst Marion Roussel, Romainville, France), lomefloxacin (Sigma, St Louis, MO, USA), moxifloxacin (Bayer, Wuppertal, Germany), norfloxacin (Sigma, Steinheim, Germany), ofloxacin (Sigma, Steinheim, Germany) and sitafloxacin (Daiichi Pharmaceutical, Tokyo, Japan). The reagent powder for each of these agents was provided by its manufacturer. The MIC breakpoints used for resistance were those recommended by the NCCLS for non-Enterobacteriaceae6 to those fluoroquinolones for which such recommendations are available: ciprofloxacin (MIC 1 and
4 mg/L); ofloxacin (MIC
2 and
8 mg/L); norfloxacin (MIC
4 and
16 mg/L); levofloxacin (MIC
2 and
8 mg/L); lomefloxacin (MIC
2 and
8 mg/L); and gatifloxacin (MIC
2 and
8 mg/L).
C. jejuni RH 3583 (a local control strain, originally isolated in Edinburgh, UK as C. jejuni 143483) was used as a control in susceptibility testing and also as a growth control strain. In addition, Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 35218 and Pseudomonas aeruginosa ATCC 27853 were used as controls in susceptibility testing.
Data analysis
The susceptibility data were analysed using the WHONET5 computer program (available at http://www.who.int/drugresistance/whonetsoftware/en/).
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
For the 134 ciprofloxacin-resistant C. jejuni strains, the MIC50 and MIC90 values were 16 and 32 mg/L of levofloxacin and 4 and 16 mg/L of moxifloxacin (Table 1). Sitafloxacin and clinafloxacin exhibited the lowest MIC50 and MIC90 values for these ciprofloxacin-resistant C. jejuni strains: 0.25 and 1 mg/L of sitafloxacin and 1 and 4 mg/L of clinafloxacin, respectively.
The scattergrams correlating the MICs of ciprofloxacin to those of norfloxacin, ofloxacin, levofloxacin, moxifloxacin, clinafloxacin and sitafloxacin for the 226 C. jejuni strains are presented in Figure 1. For the ciprofloxacin-resistant strains, the MIC values of norfloxacin were similar to or higher than those of ciprofloxacin, and the MIC values of ofloxacin were similar to or one dilution step lower than those of ciprofloxacin. For levofloxacin and moxifloxacin, the MIC values for ciprofloxacin-resistant strains were one to three dilution steps lower than those of ciprofloxacin. The MIC values of clinafloxacin were four dilutions steps lower than those of ciprofloxacin, and the MIC values of sitafloxacin were five to seven dilution steps lower than those of ciprofloxacin.
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Earlier data on the efficacy of sitafloxacin and clinafloxacin towards C. jejuni strains are limited. In fact, the in vitro activity of sitafloxacin has been assessed in only one previous study showing that sitafloxacin had increased activity compared with ciprofloxacin against 39 clinical Campylobacter spp. isolates.7 Also, clinafloxacin was somewhat more active than ciprofloxacin against the 18 C. jejuni isolates studied.8 Yet at the present time, clinafloxacin has no clinical relevance, since its development has been suspended. In contrast, the development of sitafloxacin continues, and the drug is undergoing Phase 1 studies in the USA and Phase 3 studies in Japan. The encouraging results of the present study suggest that the clinical efficacy of sitafloxacin should be evaluated also in campylobacteriosis.
A number of previous studies have focused on in vitro efficacy of sitafloxacin on microbes other than campylobacters. Sitafloxacin has exhibited a better activity than the other available fluoroquinolones towards e.g. several enterobacterial species, including ciprofloxacin-resistant strains.3 In one study, sitafloxacin exhibited improved activity against quinolone-resistant Klebsiella pneumoniae and Enterobacter cloacae isolates with alterations in GyrA and ParC proteins.9 In another study, the activity of sitafloxacin against quinolone-resistant clinical isolates of Neisseria gonorrhoeae bearing mutant DNA gyrases was significantly greater than that of the other fluoroquinolones tested.10 These findings have led the authors of these papers to postulate that sitafloxacin might be a potentially useful agent for the treatment of infections caused by bacterial strains resistant to other fluoroquinolones. In our previous study, the QRDR of the gyrA gene was sequenced from 115 of the 134 ciprofloxacin-resistant C. jejuni strains included in the present study, with a finding that all resistant strains had a point mutation at the codon 86, substituting isoleucine for threonine.4 These data indicate that ciprofloxacin resistance is based on mutations in gyrase genes in the majority, if not all, of the C. jejuni strains analysed here. Thus, it is possible that sitafloxacin does not have an adequate clinical activity against these ciprofloxacin-resistant strains with mutations in their gyrA. Yet, considering the low MIC values of sitafloxacin, it is possible that clinical efficacy does exist. This question cannot be answered on the basis of in vitro studies. Clinical trials to treat enteritis caused by ciprofloxacin-resistant C. jejuni with sitafloxacin may be valuable.
At the present time, macrolides are the first-choice antimicrobials for the treatment of campylobacter enteritis. It is, therefore, of concern that also the macrolide resistance in campylobacters is increasing in a number of countries.2 So far, the multiresistance of C. jejuni has not led to severe consequences, since campylobacter infections are often self-limiting and require no antimicrobial treatment. However, therapy is needed in severe cases of enteritis, in invasive infections and in patients who are immunocompromised. According to the results of our previous study, these multiresistant C. jejuni strains were in vitro susceptible to co-amoxiclav and imipenem.5 Unfortunately, very few data exist on the clinical use of ß-lactams in campylobacteriosis. Efforts should be made to delineate alternative drugs for the treatment of C. jejuni infections caused by strains which are resistant to quinolones as well as to macrolides.
In conclusion, among the fluoroquinolone compounds presently on market in Finland, levofloxacin and moxifloxacin were in vitro the most effective drugs towards all the 226 C. jejuni strains studied. Of the newer fluoroquinolones presently under development, sitafloxacin was in vitro highly effective towards C. jejuni, with low MIC values also against ciprofloxacin-resistant strains. Sitafloxacin might be a candidate for clinical trials on campylobacteriosis.
![]() |
Transparency declarations |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
![]() |
Acknowledgements |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
2. Engberg J, Aarestrup FM, Taylor DE et al. Quinolone and macrolide resistance in Campylobacter jejuni and C. coli: resistance mechanisms and trends in human isolates. Emerg Infect Dis 2001; 7: 2434.[ISI][Medline]
3.
Milatovic D, Schmitz FJ, Brisse S et al. In vitro activities of sitafloxacin (DU-6859a) and six other fluoroquinolones against 8,796 clinical bacterial isolates. Antimicrob Agents Chemother 2000; 44: 11027.
4.
Hakanen A, Jalava J, Kotilainen P et al. gyrA polymorphism in Campylobacter jejuni: detection of gyrA mutations in 162 C. jejuni isolates by single-strand conformation polymorphism and DNA sequencing. Antimicrob Agents Chemother 2002; 46: 26447.
5.
Hakanen AJ, Lehtopolku M, Siitonen A et al. Multidrug resistance in Campylobacter jejuni strains collected from Finnish patients during 1995-2000. J Antimicrob Chemother 2003; 52; 10359.
6. National Committee for Clinical Laboratory Standards. Performance Standards for Antimicrobial Susceptibility Testing. Fourteenth Informational Supplement: Approved standard M2-A8 and M7-A6. NCCLS, Wayne, PA, USA, 2004.
7. Tomayko J, Korten V, Murray B. DU-6859a, a new fluoroquinolone agent. Comparative in vitro activity against enteric pathogens and multiresistant outpatient Escherichia coli. Diagn Microbiol Infect Dis 1994; 20: 457.[CrossRef][ISI][Medline]
8. Bauernfeind A. Comparison of the antibacterial activities of the quinolones Bay 12-8039, gatifloxacin (AM 1155), trovafloxacin, clinafloxacin, levofloxacin and ciprofloxacin. J Antimicrob Chemother 1997; 40: 63951.[Abstract]
9. Deguchi T, Yasuda M, Kawamura T et al. Improved antimicrobial activity of DU-6859a, a new fluoroquinolone, against quinolone-resistant Klebsiella pneumoniae and Enterobacter cloacae isolates with alterations in GyrA and ParC proteins. Antimicrob Agents Chemother 1997; 41: 25446.[Abstract]
10. Deguchi T, Yasuda M, Nakano M et al. Antimicrobial activity of a new fluoroquinolone, DU-6859a, against quinolone-resistant clinical isolates of Neisseria gonorrhoeae with genetic alterations in the GyrA subunit of DNA gyrase and the ParC subunit of topoisomerase IV. J Antimicrob Chemother 1997; 39: 2479.[Abstract]
|