Efficacy of trovafloxacin in treatment of experimental staphylococcal or streptococcal endocarditis.

The efficacy of trovafloxacin against Staphylococcus aureus and viridans group streptococci was investigated in vitro and in an experimental model of endocarditis. The MICs at which trovafloxacin and ciprofloxacin inhibited 90% of clinical isolates of such bacteria (MIC90s) were (i) 0.03 and 2 mg/liter, respectively, for 30 ciprofloxacin-susceptible S. aureus isolates, (ii) 32 and 128 mg/liter, respectively, for 20 ciprofloxacin-resistant S. aureus isolates, and (iii) 0.25 and 8 mg/liter, respectively, for 28 viridans group streptococci. Rats with aortic vegetations were infected with either of two ciprofloxacin-susceptible but methicillin-resistant S. aureus strains (strains COL and P8), one penicillin-susceptible Streptococcus sanguis strain, or one penicillin-resistant Streptococcus mitis strain. Rats were treated for 3 or 5 days with doses that resulted in kinetics that simulated those achieved in humans with trovafloxacin (200 mg orally once a day), ciprofloxacin (750 mg orally twice a day), vancomycin (1 g intravenously twice a day), or ceftriaxone (2 g intravenously once a day). Against the staphylococci, the activities of both trovafloxacin and ciprofloxacin were equivalent to that of vancomycin, and treatment of endocarditis with these drugs was successful (P < 0.05). However, ciprofloxacin selected for resistant derivatives in vitro and in vivo, whereas trovafloxacin was 10 to 100 times less prone than ciprofloxacin to select for resistance in vitro and did not select for resistance in vivo. Against the two streptococcal isolates, trovafloxacin significantly (P < 0.05) decreased bacterial counts in the vegetations but was less effective than the control drug, ceftriaxone. Thus, a simulated oral dose of trovafloxacin (200 mg per day) was effective against ciprofloxacin-susceptible staphylococci and was less likely than ciprofloxacin to select for resistance. The simulated oral dose of trovafloxacin also had some activity against streptococcal endocarditis, but optimal treatment of infections caused by such organisms might require higher doses of the drug.

Y-688, a new quinolone active against quinolone-resistant Staphylococcus aureus: lack of in vivo efficacy in experimental endocarditis.

Y-688 is a new fluoroquinolone with increased activity against ciprofloxacin-resistant staphylococci. The MICs of Y-688 and other quinolones were determined for 58 isolates of ciprofloxacin-resistant and methicillin-resistant Staphylococcus aureus (MRSA). The MICs at which 50% and 90% of bacteria were inhibited were >/=128 and >/=128 mg/liter, respectively, for ciprofloxacin, 16 and 32 mg/liter, respectively, for sparfloxacin, and 0.25 and 1 mg/liter, respectively, for Y-688. This new quinolone was further tested in rats with experimental endocarditis due to either of two isolates of ciprofloxacin-resistant MRSA (namely, P8/128 and CR1). Infected animals were treated for 3 days with ciprofloxacin, vancomycin, or Y-688. Antibiotics were administered through a computerized pump to simulate human-like pharmacokinetics in the serum of rats. The anticipated peak and trough levels of Y-688 were 4 and 1 mg/liter at 0.5 and 12 h, respectively. Treatment with ciprofloxacin was ineffective. Vancomycin significantly decreased vegetation bacterial counts for both organisms (P less, similar 0.05). In contrast, Y-688 only marginally decreased vegetation bacterial counts (P greater, similar 0.05). Moreover, several vegetation that failed Y-688 treatment grew staphylococci for which the MICs of the test antibiotic were increased two to eight times. Y-688 also selected for resistance in vitro, and isolates for which the MICs were increased eight times emerged at a frequency of ca. 10(-8). Thus, in spite of its low MIC for ciprofloxacin-resistant MRSA, Y-688 failed in vivo and its use carried the risk of resistance selection. The fact that ciprofloxacin-resistant staphylococci became rapidly resistant to this potent new drug suggests that the treatment of ciprofloxacin-resistant MRSA with new quinolones might be more problematic than expected.

Parenteral sparfloxacin compared with ceftriaxone in treatment of experimental endocarditis due to penicillin-susceptible and -resistant streptococci.

A new, investigational, parenteral form of sparfloxacin was compared with ceftriaxone in the treatment of experimental endocarditis caused by either of three penicillin-susceptible streptococci or one penicillin-resistant streptococcus. Both drugs have prolonged half-lives in serum, allowing single daily administration to humans. Sparfloxacin had relatively low MICs (0.25 to 0.5 mg/liter) for all four organisms and was also greater than or equal to eight times more effective than the other quinolones against 21 additional streptococcal isolates recovered from patients with bacteremia. Ceftriaxone MICs were 0.032 to 0.064 mg/liter for the penicillin-susceptible strains and 2 mg/liter for the resistant isolate. Both antibiotics resulted in moderate bacterial killing in vitro. Rats with catheter-induced aortic vegetations were inoculated with 10(7) CFU of the test organisms. Antibiotic treatment was started 48 h later and lasted either 3 or 5 days. The drugs were injected at doses which mimicked the kinetics in human serum produced by one intravenous injection of 400 mg of sparfloxacin (i.e., the daily dose expected to be given to human adults) and 2 g of ceftriaxone. Both antibiotics significantly decreased the bacterial densities in the vegetations. However, sparfloxacin was slower than ceftriaxone in its ability to eradicate valvular infection caused by penicillin-susceptible bacteria. While this difference was quite marked after 3 days of therapy, it tended to vanish when treatment was prolonged to 5 days. In contrast, sparfloxacin was very effective against the penicillin-resistant isolate, an organism against which ceftriaxone therapy failed in vivo. No sparfloxacin-resistant mutant was selected during therapy. Thus, in the present experimental setting, this new, investigational, parenteral form of sparfloxacin was effective against severe infections caused by both penicillin-susceptible and penicillin-resistant streptococci.

Antibiotic susceptibility of Waddlia chondrophila in Acanthamoeba castellanii amoebae.

Waddlia chondrophila is an emerging cause of miscarriage in bovines and humans. Given the strict intracellular growth of this Chlamydia-like organism, its antibiotic susceptibility was tested by amoebal coculture, cell culture, and real-time PCR. W. chondrophila was susceptible to doxycycline and azithromycin but resistant to beta-lactams and fluoroquinolones.

Chlamydia: signes d'appel, diagnostic et traitement [Chlamydia: diagnostic and treatment].

Chlamydia are obligate intracellular bacteria. Three species are considered human pathogens. Chlamydophila pneumoniae is one of the most common agents of atypical community-acquired pneumonia. Chlamydophila psittaci causes psittacosis, a severe zoonotic pneumonia transmitted by birds. Finally, Chlamydia trachomatis is the etiologic agent of trachoma and urogenital infections. The latter are commonly asymptomatic or paucisymptomatic. Thus, they may remain undiagnosed for years, leading to serious late complications such as salpingitis, ectopic pregnancy and infertility. Currently, the diagnosis of chlamydial infections is essentially based on molecular methods. Treatment should use an antibiotic with good intracellular bioavailability such as tetracycline, macrolides and new generation fluoroquinolones.

Efficacies of moxifloxacin, ciprofloxacin, and vancomycin against experimental endocarditis due to methicillin-resistant Staphylococcus aureus expressing various degrees of ciprofloxacin resistance.

The new 8-methoxyquinolone moxifloxacin was tested against two ciprofloxacin-susceptible Staphylococcus aureus strains (strains P8 and COL) and two ciprofloxacin-resistant derivatives of strain P8 carrying a single grlA mutation (strain P8-4) and double grlA and gyrA mutations (strain P8-128). All strains were resistant to methicillin. The MICs of ciprofloxacin and moxifloxacin were 0.5 and 0.125 mg/liter, respectively, for P8; 0.25 and 0.125 mg/liter, respectively, for COL; 8 and 0.25 mg/liter, respectively, for P8-4; and >or=128 and 2 mg/liter, respectively, for P8-128. In vitro, the rate of spontaneous resistance of P8 and COL was 10(-7) on agar plates containing ciprofloxacin at two times the MIC, whereas it was <or=10(-10) on agar plates containing moxifloxacin at two times the MIC. Rats with experimental aortic endocarditis were treated with doses of drugs that simulate the kinetics in humans: moxifloxacin, 400 mg orally once a day; ciprofloxacin, 750 mg orally twice a day; or vancomycin, 1 g intravenously twice a day. Treatment was started either 12 or 24 h after infection and lasted for 3 days. Moxifloxacin treatment resulted in culture-negative vegetations in a total of 20 of 21 (95%) rats infected with P8, 10 of 11 (91%) rats infected with COL, and 19 of 24 (79%) rats infected with P8-4 (P < 0.05 compared to the results for the controls). In contrast, ciprofloxacin treatment sterilized zero of nine (0%) vegetations infected with first-level resistant mutant P8-4. Vancomycin sterilized only 8 of 15 (53%), 6 of 11 (54%), and 12 of 23 (52%) of the vegetations, respectively. No moxifloxacin-resistant derivative emerged among these organisms. However, moxifloxacin treatment of highly ciprofloxacin-resistant mutant P8-128 failed and selected for variants for which the MIC increased two times in 2 of 10 animals. Thus, while oral moxifloxacin might deserve consideration as treatment for staphylococcal infections in humans, caution related to its use against strains for which MICs are borderline is warranted.

Antibiotic susceptibility of Estrella lausannensis, a potential emerging pathogen.

Estrella lausannensis is a new Chlamydia-related bacterium, belonging to the Criblamydiaceae family. As suggested by its species name, this bacterium harbors a peculiar star shape. E. lausannensis is able to infect a wide range of amoebal, fish and mammalian cell lines. Moreover, seroprevalence of 2.9% was reported in children and in women with tubal pathology, showing that humans are commonly exposed to this recently discovered strict intracellular bacteria considered as a potential pathogen. Antibiotic susceptibility was determined using two approaches: qPCR and cellular mortality assay. Antibiotics classically used against intracellular bacteria were tested, including β-lactams, fluoroquinolones, cyclines and macrolides. We showed that E. lausannensis is resistant to β-lactams and fluoroquinolones, and sensitive to cyclines. Interestingly, E. lausannensis is slightly resistant to azithromycin with a MIC of 2 μg/ml, which is 10 fold higher compared to Waddlia chondrophila and Parachlamydia acanthamoebae MIC's. A single A2059C mutation in 23S rRNA gene could be responsible for this unexpected resistance.

Efficacy of garenoxacin in treatment of experimental endocarditis due to Staphylococcus aureus or viridans group streptococci.

The activity of garenoxacin was investigated in rats with experimental endocarditis due to staphylococci and viridans group streptococci (VGS). The staphylococci tested comprised one ciprofloxacin-susceptible and methicillin-susceptible Staphylococcus aureus (MSSA) isolate (isolate 1112), one ciprofloxacin-susceptible but methicillin-resistant S. aureus (MRSA) isolate (isolate P8), and one ciprofloxacin-resistant mutant (grlA) of P8 (isolate P8-4). The VGS tested comprised one penicillin-susceptible isolate and one penicillin-resistant isolate (Streptococcus oralis 226 and Streptococcus mitis 531, respectively). To simulate the kinetics of drugs in humans, rats were infused intravenously with garenoxacin every 24 h (peak and trough levels in serum, 6.1 and 1.0 mg/liter, respectively; area under the concentration-time curve [AUC], 63.4 mg. h/liter) or levofloxacin every 12 h (peak and trough levels in serum, 7.3 and 1.5 mg/liter, respectively; AUC, 55.6 mg. h/liter) for 3 or 5 days. Flucloxacillin, vancomycin, and ceftriaxone were used as control drugs. Garenoxacin, levofloxacin, flucloxacillin, and vancomycin sterilized >/=70% of the vegetations infected with both ciprofloxacin-susceptible staphylococcal isolates (P < 0.05 versus the results for the controls). Garenoxacin and vancomycin also sterilized 70% of the vegetations infected with ciprofloxacin-resistant MRSA isolate P8-4, whereas treatment with levofloxacin failed against this organism (cure rate, 0%; P < 0.05 versus the results obtained with the comparator drugs). Garenoxacin did not select for resistant derivatives in vivo. In contrast, levofloxacin selected for resistant variants in four of six rats infected with MRSA isolate P8-4. Garenoxacin sterilized 90% of the vegetations infected with both penicillin-susceptible and penicillin-resistant isolates of VGS. Levofloxacin sterilized only 22 and 40% of the vegetations infected with penicillin-susceptible S. oralis 226 and penicillin-resistant S. mitis 531, respectively. Ceftriaxone sterilized only 40% of those infected with penicillin-resistant S. mitis 531 (P < 0.05 versus the results obtained with garenoxacin). No quinolone-resistant VGS were detected. In all the experiments successful quinolone treatment was predicted by specific pharmacodynamic criteria (D. R. Andes and W. A. Craig, Clin. Infect. Dis. 27:47-50, 1998). The fact that the activity of garenoxacin was equal or superior to those of the standard comparators against staphylococci and VGS indicates that it is a potential alternative for the treatment of infections caused by such bacteria.

Biology and pathogenicity of "Waddlia chondrophila"

Abstract This thesis investigates the pathogenicity of a Chlamydia-related bacterium: Waddlia chondrophila, which is suspected to cause abortion in bovines as well as miscarriages in humans. Macrophages represent the first line of defense of the innate immunity against invading pathogens, we thus studied the interaction between W. chondrophila and human macrophages. We observed that W. chondrophila multiplied very efficiently inside monocyte-derived macrophages. Diagnostic tools to detect obligate intracellular bacteria are lacking so we developed a Waddlia specific real-time PCR based on the 16S rRNA encoding gene. Since W. chondrophila could be involved in human miscarriage, we analyzed samples from women having miscarriage or uneventful pregnancy. Waddlia serologies results confirmed an association between the presence of W. chondrophila antibodies and miscarriage (23.2% versus 14.6% in the control group, p-value 0.044). As W. chondrophila's pathogenicity was suggested, we studied its antibiotic susceptibility. W. chondrophila revealed to be susceptible to macrolides and tetracylines but resistant to beta-lactams and fluoroquinolones. This resistance to fluoroquinolones could be explained by mutations in the quinolone resistance determining region of the gyrase (GyrA) and topoisomerase IV (ParC) encoding genes. In conclusion, this thesis allowed to precise the role of W. chondrophila in human miscarriage. However, more studies will be necessary to fully understand the pathogenesis of W. chondrophila in adverse pregnancy outcomes. Résumé Le but de cette thèse a été d'étudier la pathogénicité d'une bactérie apparentée aux Chlamydia: Waddlia chondrophila. Les macrophages représentant la première ligne de défense du système immunitaire inné contre les pathogènes, nous avons d'abord étudié l'interaction entre W. chondrophila and les macrophages humains. Nous avons pu observer que W. chondrophila résistait aux effecteurs microbicides des macrophages et se multipliait efficacement au sein de ces cellules. Au vu du manque d'outils diagnostiques pour détecter cette bactérie intracellulaire obligatoire, nous avons également développé une PCR en temps réel, spécifique pour Waddlia, basée sur le gène de l'ARN ribosomal 16S. Cette PCR a été utilisée dans les différents projets afin de détecter la présence de W. chondrophila. W. chondrophila étant suspectée de pouvoir causer des fausses couches chez la femme, nous avons analysé des échantillons provenant de femmes ayant souffert de fausse couche, ainsi que, comme contrôles, des femmes ayant eu une grossesse normale. Les sérologies ont révélé une association entre la présence d'anticorps dirigés contre Waddlia et la fausse couche (23.2% versus 14.6% chez les contrôles, p-value=0.044). La présence de la bactérie a aussi été détectée par PCR et immunohistochimie dans plusieurs échantillons. L'implication de W. chondrophila dans la fausse couche se précisant, nous avons étudié sa susceptibilité aux antibiotiques. W. chondrophila s'est révélée sensible aux macrolides et aux tetracyclines mais résistante aux beta-lactames et aux quinolones. Cette résistance aux quinolones peut être expliquée par la présence de mutations dans le QRDR (région déterminant la résistance aux quinolones) des gènes gyrA et parC. En conclusion, cette thèse a permis de préciser l'implication de W. chondrophila dans la fausse couche. Des études complémentaires seront cependant nécessaires pour confirmer et préciser le rôle exact de W. chondrophila dans les problèmes obstétricaux.

In vitro susceptibility of Actinobaculum schaalii to 12 antimicrobial agents and molecular analysis of fluoroquinolone resistance.

OBJECTIVES: To assess the in vitro susceptibility of Actinobaculum schaalii to 12 antimicrobial agents as well as to dissect the genetic basis of fluoroquinolone resistance. METHODS: Forty-eight human clinical isolates of A. schaalii collected in Switzerland and France were studied. Each isolate was identified by 16S rRNA sequencing. MICs of amoxicillin, ceftriaxone, gentamicin, vancomycin, clindamycin, linezolid, ciprofloxacin, levofloxacin, moxifloxacin, co-trimoxazole, nitrofurantoin and metronidazole were determined using the Etest method. Interpretation of results was made according to EUCAST clinical breakpoints. The quinolone-resistance-determining regions (QRDRs) of gyrA and parC genes were also identified and sequence analysis was performed for all 48 strains. RESULTS: All isolates were susceptible to amoxicillin, ceftriaxone, gentamicin, clindamycin (except three), vancomycin, linezolid and nitrofurantoin, whereas 100% and 85% were resistant to ciprofloxacin/metronidazole and co-trimoxazole, respectively. Greater than or equal to 90% of isolates were susceptible to the other tested fluoroquinolones, and only one strain was highly resistant to levofloxacin (MIC ?32 mg/L) and moxifloxacin (MIC 8 mg/L). All isolates that were susceptible or low-level resistant to levofloxacin/moxifloxacin (n?=?47) showed identical GyrA and ParC amino acid QRDR sequences. In contrast, the isolate exhibiting high-level resistance to levofloxacin and moxifloxacin possessed a unique mutation in GyrA, Ala83Val (Escherichia coli numbering), whereas no mutation was present in ParC. CONCLUSIONS: When an infection caused by A. schaalii is suspected, there is a risk of clinical failure by treating with ciprofloxacin or co-trimoxazole, and ?-lactams should be preferred. In addition, acquired resistance to fluoroquinolones more active against Gram-positive bacteria is possible.

Prise en charge de la pneumonie communautaire [Management of community acquired pneumonia]

Une grande partie des patients présentant une pneumonie communautaire ont un bon pronostic et peuvent être suivis dans la pratique ambulatoire moyennant un nombre limité d'examens paracliniques. Le diagnostic repose sur une clinique suggestive en présence d'un infiltrat compatible avec une pneumonie à la radiographie de thorax. Une anamnèse de voyage et une bonne connaissance de résistances locales du pneumocoque aux antibiotiques sont déterminantes pour le choix du traitement. Pour les patients de moins de 50 ans sans comorbidités et sans signes de sévérité, il est généralement recommandé de prescrire un macrolide ou une fluoroquinolone de 3e ou de 4e génération (fluoroquinolones «respiratoires»). Pour les patients plus âgés, et pour ceux qui présentent des comorbidités ou des critères de sévérité, une évaluation à l'hôpital est indiquée. La majorité des patients hospitalisés en soins généraux peuvent être traités par l'association d'une bêta-lactame et d'un macrolide, ou par une fluoroquinolone «respiratoire» seule, après prélèvements d'expectorations et de sang pour culture.

Hospital antibiotic consumption in Switzerland: comparison of a multicultural country with Europe.

The consumption of antibiotics in the inpatient setting of Switzerland was assessed to determine possible differences between linguistic regions, and to compare these results with European results. Data on antibiotic consumption were obtained from a sentinel network representing 54% of the national acute care hospitals, and from a private drug market monitoring company. Aggregated data were converted into defined daily doses (DDD). The total consumption density in Switzerland was close to the median consumption reported in European surveys. Between 2004 and 2008, the total consumption of systemic antibiotics rose from 46.1 to 54.0 DDD per 100 occupied bed-days in the entire hospitals, and from 101.6 to 114.3 DDD per 100 occupied bed-days in the intensive care units. Regional differences were observed for total consumption and among antibiotic classes. Hospitals in the Italian-speaking region showed a significantly higher consumption density, followed by the French- and German-speaking regions. Hospitals in the Italian-speaking region also had a higher consumption of fluoroquinolones, in line with the reported differences between Italy, Germany and France. Antibiotic consumption in acute care hospitals in Switzerland is close to the European median with a relatively low consumption in intensive care units. Some of the patterns of variation in consumption levels noticed among European countries are also observed among the cultural regions of Switzerland.