Comparative In Vitro Activity of Quinolones Against Stenotrophomonas maltophilia

 The susceptibility of 109 Stenotrophomonas maltophilia isolates, all characterized by pulsed-field gel electrophoresis, to nine quinolones was studied. Grepafloxacin, trovafloxacin, and moxifloxacin displayed similar intrinsic activities (MIC90, 0.5 μg/ml), which were lower than those of ofloxacin and ciprofloxacin (MIC90, 4 μg/ml), norfloxacin (MIC90, 64 μg/ml), and nalidixic acid (MIC90, 32 μg/ml). Nalidixic acid was generally one- to twofold dilutions more active than norfloxacin. According to the criteria of the National Committee for Clinical Laboratory Standards (NCCLS), the percentage of isolates susceptible to ciprofloxacin (breakpoint ≤1 μg/ml) was 76.1%. Using the NCCLS breakpoint for comparative purposes, the percentage of isolates susceptible to grepafloxacin, moxifloxacin, and trovafloxacin was 95.4, 96.4, and 96.4%, respectively. These results indicate that new quinolones may potentially be used for the management of Stenotrophomonas maltophilia infections.     

In Vitro Activity of Gemifloxacin (SB-265805) Compared to Eleven Other Antimicrobial Agents Against Streptococcal Isolates, Excluding Streptococcus pneumoniae

 The purpose of the study presented here was to determine the in vitro activity of gemifloxacin compared with that of 11 other antimicrobial agents (5 of them quinolones) against 400 isolates of β-haemolytic and viridans group streptococci. The minimum inhibitory concentration values for gemifloxacin against 90% of the streptococci tested were as follows: Lancefield groups A, C and G, 0.06 μg/ml; Lancefield group B, Streptococcus mitis, Streptococcus mutans and Streptococcus bovis, 0.125 μg/ml; and Streptococcus milleri, 0.03 μg/ml. Resistance to penicillin, ampicillin and erythromycin was found mainly in the Streptococcus mitis isolates; tetracycline showed variable results, and no vancomycin resistance was encountered. Higher rates of ciprofloxacin resistance were identified in the Streptococcus bovis, mitis and mutans isolates. In conclusion, gemifloxacin was the most active quinolone tested followed by trovafloxacin, sparfloxacin, grepafloxacin, ciprofloxacin and levofloxacin, especially against isolates resistant to β-lactam agents, macrolides and tetracycline.     

In Vitro Susceptibility of Environmental Cryptococcus neoformans Variety neoformans Isolates from Turkey to Six Antifungal Agents, Including SCH56592 and Voriconazole

 The in vitro antifungal susceptibility of 27 environmental (pigeon droppings) isolates of Cryptococcus neoformans var. neoformans, isolated from throughout Turkey, to six antifungal agents (amphotericin B, flucytosine, fluconazole, voriconazole, itraconazole, and SCH56592) was studied. Voriconazole, itraconazole, and SCH56592 all showed comparable activity and were more active than the remaining three antifungal agents tested. Overall, SCH56592 was the most active agent (MIC90, 0.015 μg/ml, at both 48 and 72 h), followed by itraconazole (MIC90, 0.03 μg/ml, at both 48 and 72 h) and voriconazole (MIC90, 0.25 μg/ml, at both 48 and 72 h), respectively. Antifungal susceptibility data for environmental isolates may reflect patterns for the clinical isolates recovered from patients from the same geographic area.     

New Colorimetric Microdilution Method for In Vitro Susceptibility Testing of Borrelia burgdorferi Against Antimicrobial Substances

 A newly developed colorimetric microdilution method was used to analyze the activity of 12 antimicrobial agents against nine Borrelia burgdorferi isolates, including all three genospecies pathogenic for humans. In addition, in vitro antimicrobial resistance patterns of Borrelia valaisiana and Borrelia bissettii tick isolates were investigated. The applied test system is based upon color changes that occur in the presence of phenol red and result from the accumulation of nonvolatile acid produced by actively metabolizing spirochetes. After 72 h of incubation, minimal inhibitory concentrations (MICs) were determined from the decrease of absorbance by software-assisted calculation of growth curves. MIC values were lowest for azlocillin (MIC, ≤0.125 μg/ml), ceftriaxone (MIC range, ≤0.015–0.06 μg/ml), and azithromycin (MIC range, ≤0.015–0.06 μg/ml). Whereas tobramycin (MIC range, 8–64 μg/ml) exhibited little activity, spectinomycin (MIC range, 0.25–2 μg/ml) showed in vitro antimicrobial activity against Borrelia burgdorferi. The MICs of penicillin G for Borrelia afzelii isolates were ten times higher than those for Borrelia burgdorferi, Borrelia valaisiana, and Borrelia bissettii isolates (P<0.05) and 100 times higher than those for isolates belonging to the genospecies Borrelia garinii (P<0.05). Further significant differences with respect to the MIC values of the other antimicrobial agents tested were not noted. The colorimetric microdilution method offered the advantages of reliability, reproducibility, and convenience and could handle large numbers of isolates and antibiotics.     

Comparative Activity of Eighteen Antimicrobial Agents against Anaerobic Bacteria Isolated in South Africa

 The in vitro activity of 18 antimicrobial agents was determined against 378 anaerobic bacteria isolated in Bloemfontein, South Africa, during 1996/97. Against the gram-positive isolates, MICs of penicillin and cefoxitin were >0.5 μg/ml and >16 μg/ml, respectively, for five and three strains of non-perfringens Clostridium spp. Seventeen Peptostreptococcus anaerobius strains were resistant to penicillin (MIC≥2 μg/ml). All gram-positive anaerobes tested except one Peptostreptococcus sp. and one Clostridium sp. were susceptible to dalfopristin-quinupristin (MICs≤1 μg/ml). The carbapenems exhibited excellent activity against the gram-positive isolates and were effective against most gram-negative anaerobes, with the exception of the fusobacteria. Only seven strains exhibited decreased susceptibility to trovafloxacin (MICs>2 μg/ml). In mixed anaerobic/aerobic infections, carbapenems and the fourth-generation quinolone trovafloxacin were the agents most suitable for us as broad-spectrum monotherapy.     

Antibacterial Activity of Moxifloxacin (Bay 12-8039) against Aerobic Clinical Isolates, and Provisional Criteria for Disk Susceptibility Tests

 Moxifloxacin (Bay 12–8039), ciprofloxacin, and levofloxacin were compared in vitro against 1074 clinical isolates gathered from different medical centers throughout North America during the winter months of 1997. Moxifloxacin E tests and broth microdilution tests gave comparable results. Moxifloxacin was particularly potent against respiratory pathogens such as Haemophilus influenzae and Streptococcus pneumoniae. Ciprofloxacin was the most potent study drug against the family of Enterobacteriaceae and Pseudomonas spp. For tests of 5 μg moxifloxacin disks, zone size criteria of ≤17 mm for resistant (MIC ≥8 μg/ml) and ≥21 mm for susceptible (MIC ≤2 μg/ml) are provisionally proposed for use while clinical trials are under way.     

Urinary Excretion and Bactericidal Activity of Intravenous Ciprofloxacin Compared with Oral Ciprofloxacin

 Twelve healthy volunteers participated in a randomized crossover study to compare urinary concentrations, serum parameters, and urinary bactericidal activity of ciprofloxacin after single intravenous (i.v.) doses of 200 mg and 400 mg and an oral (p.o.) dose of 500 mg. The median serum concentrations at 1 h after administration were 1 μg/ml, 4.3 μg/ml, and 2.2 μg/ml, respectively. Between the first collection period (0–2 h) and the last collection period (38–48 h), the median urinary concentrations decreased from 394 μg/ml, 675 μg/ml, and 585 μg/ml, respectively, to 0.3 μg/ml, 0.6 μg/ml, and 1 μg/ml, respectively. The urinary concentrations after the 400 mg i.v. and the 500 mg p.o. doses were not statistically different but were significantly higher than those after the 200 mg i.v. dose. The urinary bactericidal titers (UBTs), defined as the highest urinary dilution bactericidal for the organism tested, were determined against Escherichia coli (ATCC 25922) and eight uropathogens up to 48 h after administration of ciprofloxacin. The UBTs after the 400 mg i.v. and the 500 mg p.o. doses were similar and were significantly higher (P<0.05) than those following the 200 mg i.v. dose. After 400 mg i.v. and 500 mg p.o., median UBTs of ≥1 : 4 were present up to 48 h for all strains for which the MIC was ≤0.5 μg/ml, except for one nalidixic-acid resistant Escherichia coli strain for which the MIC was 0.25 μg/ml. Species for which the MIC is ≥1 μg/ml showed median UBTs of ≥1 : 4 for 8–16 h. Median UBTs of ≥1 : 4 were present up to 8 and 12 h for both Pseudomonas strains tested. A once-daily dosage of 400 mg i.v. or 500 mg p.o. might be sufficient for treatment of urinary tract infections caused by highly susceptible pathogens. A twice-daily dosing scheme seems to be preferable for complicated infections caused by pathogens with intermediate susceptibilty (MIC≥1 μg/ml) or for empiric therapy.     

Electrophoretic Karyotyping and Triazole Susceptibility of Candida glabrata Clinical Isolates

 A series of 35 strains of Candida glabrata isolated from 29 subjects (5 AIDS patients and 24 HIV-seronegative individuals) were typed by electrophoretic karyotyping and tested for their susceptibilities to both fluconazole and itraconazole. Almost every individual harboured his/her own specific isolate (DNA type). Neither the source of isolation nor the patient's HIV status was associated with a given DNA type. Recurrences were generally due to the persistence of the same DNA type over time. Only 9% of the isolates showed reduced susceptibility to fluconazole (MIC≥8.0 μg/ml), while 43% of the isolates showed reduced susceptibility to itraconazole (MIC≥0.25 μg/ml) (P=0.02). These data show that electrophoretic karyotyping is a useful technique for DNA typing of isolates of Candida glabrata. Care must be taken prior to inititation of antifungal therapy with either of these drugs.     

Characterization of Isoniazid-Resistant Strains of Mycobacterium tuberculosis on the Basis of Phenotypic Properties and Mutations in katG

 Forty isoniazid-resistant Mycobacterium tuberculosis isolates were characterized on the basis of phenotypic properties (i.e., catalase activity, MIC of isoniazid, and growth pattern in the presence of 7 different concentrations of isoniazid) and alterations in the katG gene (codons 315 and 463). Three different growth patterns could be distinguished: concentration-dependent inhibition of growth was observed in 29 strains, similar growth at all concentrations was seen in 7 strains, and enhanced growth at low concentrations of isoniazid was evident in 4 strains. The MIC of isoniazid was ≤4 μg/ml for 29 of 40 strains. Mutation at codon 315 of the katG was detected in 28 of 40 strains. However, only one of the seven strains for which the MIC of isoniazid was ≥16 μg/ml had mutation at this codon. Five of these seven strains for which the MIC was ≥16 μg/ml had no catalase activity. The results indicate that the MIC of isoniazid for a majority of strains is below the level achievable in serum. Therefore, isoniazid may be beneficial for the treatment of some cases of multidrug-resistant tuberculosis. Determination of catalase activity aids in the detection of isolates for which MICs are high and could, in conjunction with molecular methods, provide rapid detection of most isoniazid-resistant strains.     

Use of the Polymerase Chain Reaction for Rapid Detection of High-Level Mupirocin Resistance in Staphylococci

 The minimum inhibitory concentrations (MICs) of mupirocin were determined by the E test (AB Biodisk, Sweden) and the agar dilution method for 107 staphylococci. The organisms consisted of 34 coagulase-negative staphylococci and 73 methicillin-resistant Staphylococcus aureus. Polymerase chain reaction (PCR) primers designed to amplify a 456 bp region of the plasmid-borne isoleucyl tRNA synthetase gene (ileS–2), responsible for high-level mupirocin resistance in staphylococci, were used on DNA preparations from these isolates. Isolates with high-level mupirocin resistance due to the ileS–2 gene should be PCR positive. There was close correlation between the E test and agar dilution MIC values, with only two strains differing by more than two serial dilutions. Most (51 of 54 strains) of the high-level resistant strains (MIC>256 μg/ml) were resistant to the highest concentration of mupirocin tested (1024 μg/ml). PCR correctly classified all but four (96%) of the isolates in accordance with the results of agar dilution. All four isolates that gave discrepant results were methicillin-resistant Staphylococcus aureus. Two of these were PCR positive, yet the MIC of mupirocin for these strains was <0.06 μg/ml; on prolonged incubation they produced halos within the inhibition zone on agar diffusion testing, suggesting that the phenotypic results may have been erroneous. One of 54 isolates for which the MIC exceeded 256 μg/ml was PCR negative when tested by the original methodology, but a 456 bp product was produced when retested using a lowered annealing temperature. One isolate for which the MIC of mupirocin was 16 μg/ml by agar dilution and 8 μg/ml by the E test was positive by PCR. PCR of the ileS–2 gene is a useful, rapid method for detecting high-level mupirocin resistance in staphylococci.     

Comparative In Vitro Activity of Gatifloxacin Against Stenotrophomonas maltophilia and Burkholderia Species Isolates Including Evaluation of Disk Diffusion and E Test Methods

 The in vitro activity of gatifloxacin, a new fluoroquinolone, was compared to that of five other fluoroquinolones against 105 Stenotrophomonas maltophilia isolates and 52 Burkholderia spp. isolates. The gatifloxacin MICs were determined using the broth microdilution method and the E test (AB Biodisk, Sweden); these methods were compared for test accuracy, and 5 μg disk zone diameters were compared for interpretive accuracy using the standardized disk diffusion method. In terms of potency, gatifloxacin was most similar to sparfloxacin and trovafloxacin against Stenotrophomonas maltophilia (MIC50, 0.5–1 mg/l) and Burkholderia spp. (MIC50, 1–2 mg/l). This activity was greater than that of ciprofloxacin, levofloxacin or ofloxacin (MIC50, ≥2 mg/l) against Stenotrophomonas maltophilia isolates but comparable to that of levofloxacin against the Burkholderia spp. (60% susceptible at ≤2 mg/l). The E test results compared well with the reference dilution test results (81–97% at ±1 log₂ dilution). The disk diffusion test using previously suggested breakpoints for other bacteria (≥18 mm or ≤2 mg/l for susceptible and ≤14 mm or ≥8 mg/l for resistant) also performed well, at >90% categorical agreement. The activity of gatifloxacin is comparable to that of other newer quinolones against isolates of Stenotrophomonas maltophilia and Burkholderia spp., and susceptibility testing using simple qualitative and quantitative methods appears to function well with these drug/organism combinations.     

Flucytosine Primary Resistance in Candida Species and Cryptococcus neoformans

 The in vitro activity of flucytosine (5FC) against 1,140 clinical isolates of Candida spp. and Cryptococcus neoformans was evaluated and compared with the activity of amphotericin B, fluconazole and itraconazole. Overall, 87.72% (1,000/1,140) of yeasts were susceptible to 5FC. This agent showed less potent in vitro activity against Candida glabrata, Candida krusei, Candida guilliermondii and Cryptococcus neoformans (MIC90s, 8–16 μg/ml) and intermediate activity or resistance to 6.5% of Candida albicans, 5.1% of Candida tropicalis and 0.8% of Candida parapsilosis strains. Amphotericin B showed potent activity against isolates with an MIC of 5FC≥8 μg/ml. A total of 112 of 140 strains that were 5FC-intermediate or -resistant showed decreased susceptibility to azoles (P<0.01).     

In vitro activity of OPC-17116 compared to other broad-spectrum fluoroquinolones

The in vitro activity of OPC-17116 was compared to that of five similar fluoroquinolones (ciprofloxacin, enoxacin, norfloxacin, ofloxacin and temafloxacin). A total of 700 isolates from recent cases of clinical bacteremia were tested. Fifty additional stock strains with well-characterized resistance mechanisms were also processed. The minimal concentrations inhibiting 90 % of strains (MIC90) ofEnterobacteriaceae species were for OPC-17116 0.015–0.5 µg/ml and for ciprofloxacin 0.015–0.25 µg/ml.Moraxella catarrhalis, Haemophilus influenzae andNeisseria gonorrhoeae were very susceptible to OPC-17116 (MIC90 0.015 µg/ml) thus being fourfold more active than ciprofloxacin. For all -hemolytic streptococci and pneumococci OPC-17116 MICs were 0.5 µg/ml. The most resistant enteric bacilli were among theCitrobacter freundii andProvidencia rettgeri strains (MIC90 0.5 µg/ml).Pseudomonas aeruginosa strains were comparably susceptible to OPC-17116 (MIC90 0.5 µg/ml). Low pH and CO₂ incubation had an adverse effect on OPC-17116 MICs, and resistance development was documented among current clinical isolates of staphylococci, pseudomonas and someEnterobacteriaceae.     

Determinants for the Development of Oropharyngeal Colonization or Infection by Fluconazole-Resistant Candida Strains in HIV-Infected Patients

 A point prevalence study to document oral yeast carriage was undertaken. Risk factors for the development of oropharyngeal colonization or infection by fluconazole-resistant Candida strains in HIV-infected patients were investigated with a case-control design. Cases included all patients with fluconazole-resistant strains (MIC≥64 μg/ml), and controls were those with susceptible (MIC≤8 μg/ml) or susceptible-dependent-upon-dose (MIC 16–32 μg/ml) strains. One hundred sixty-eight Candida strains were isolated from 153 (88%) patients, 28 (16%) of whom had oropharyngeal candidiasis. Overall, 19 (12%) of the patients harbored at least one resistant organism (MIC≥64 μg/ml). Among patients with resistant strains, tuberculosis (P<0.001), esophageal candidiasis (P=0.001), clinical thrush (P<0.001), and a CD4+ cell count <200/mm³ (P=0.03) were more frequent. These patients had also been treated more commonly with antituberculous drugs (adjusted odds ratio [OR] 6.13; 95% confidence interval [CI] 2.11–17.80), ciprofloxacin (OR 6.0; 95% CI 1.23–29.26), fluconazole (OR 4.59; 95% CI 1.55–13.52), and steroids (OR 4.13; 95% CI 1.11–15.39). Multivariate analysis showed that the determinants for fluconazole resistance were therapy with antituberculous drugs (OR 3.61; 95% CI 1.08–12.07;P=0.03) and one of the following: previous tuberculosis (OR 3.53; 95% CI 1.08–14.57;P=0.03) or fluconazole exposure (OR 3.41; 95% CI 1.10–10.54). Findings from this study indicate that treatment with antituberculous drugs, previous tuberculosis, and fluconazole exposure are the strongest determinants for development of oropharyngeal colonization or infection by fluconazole-resistant Candida strains in HIV-infected patients.     

In vitro activity of fluoroquinolones against clinical isolates of Nocardia identified by partial 16S rRNA sequencing

Fluoroquinolones have several properties that make them potentially attractive candidates for the treatment of Nocardia infections, but information regarding their in vitro activity is limited. Minimum inhibitory concentrations (MIC) of five fluoroquinolones and other antimicrobials were determined by the reference broth dilution and E-test methods for 33 consecutive clinical isolates of Nocardia speciated by 16S rRNA gene sequences. The isolates included: Nocardia cyriacigeorgica (n = 6), N. nova (n = 8), N. farcinica (n = 8), N. brasiliensis (n = 3), N. asteroides (n = 4), and N. veterana (n = 4). MIC₅₀/MIC₉₀ results for ciprofloxacin, gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin by broth dilution were 32/32, 2/4, 1/4, 32/32, and 2/2 μg/ml, respectively. The MICs by broth dilution and E-test were within a two-fold doubling dilution for 94%, 97%, 97%, 100%, and 100% of isolates for ciprofloxacin, gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin, respectively. For ciprofloxacin, the E-test results showed either complete categorical agreement or minor error compared to the reference broth dilution method for 97% (32/33) of the isolates. For other fluoroquinolones, using Streptococcus pneumoniae breakpoints, 94% (124/132) of MIC results by E-test showed either complete agreement or minor error compared to the reference broth dilution method. Fluoroquinolones show variable in vitro activity against clinical isolates of Nocardia spp., and MICs determined by the E-test show reasonable agreement with those determined by the reference broth dilution method.     

Antimicrobial susceptibility patterns of Arcobacter butzleri and Arcobacter cryaerophilus strains isolated from humans and broilers

The MICs of five antimicrobial agents were determined by the agar dilution method for 98 Arcobacter butzleri and 28 Arcobacter cryaerophilus strains from humans, and poultry. With gentamicin, a MIC of 16 microg/ml was recorded for one A. butzleri strain isolated from poultry, whereas for the other strains MICs ranged from 0.25 to 4 microg/ml. With ciprofloxacin, a bimodal distribution of susceptibility levels was seen for human A. butzleri isolates (0.015-0.03 versus 0.12-0.25), whereas MICs for 65 of the 68 A. butzleri poultry strains ranged from 0.12 to 0.5 microg/ml and three strains from three different broilers were resistant with a MIC of 16 microg/ml. One A. cryaerophilus strain from poultry was resistant to erythromycin at a MIC of 128 microg/ml, whereas MICs for the other Arcobacter strains ranged from 2 to 32 microg/ml. No difference in susceptibility or resistance among the human and poultry strains tested was observed with doxycycline and nalidixic acid. The presence of acquired resistance to erythromycin and ciprofloxacin among poultry isolates is a matter of concern, because the two antimicrobials are generally prescribed as first-line drugs for the treatment of infections with Campylobacteraceae in humans.     

Comparative activity of the new fluoroquinolone bay y3118 against 177 penicillin susceptible and resistant pneumococci

The activity of a new fluoroquinolone, Bay y3118, was evaluated in comparison to three quinolones (ciprofloxacin, ofloxacin, lomefloxacin) and four broad-spectrum oral cephalosporins (cefpodoxime, cefuroxime, cefaclor, cefixime) against 49 penicillin-susceptible pneumococci, 77 pneumococci with intermediate resistance and 51 penicillin-resistant pneumococci. Quinolone activity was not affected by the penicillin susceptibility status of the organisms. Bay y3118 was very active against all strains, with an MIC90 of 0.015 µg/ml. Other quinolones were less active, with MIC90s of 4 µg/ml (ciprofloxacin and ofloxacin) and 8 µg/ml (lomefloxacin). Cephalosporin MICs rose parallel to those of penicillin. Cefuroxime and cefpodoxime were the most active cephalosporins, with MIC90s for strains showing susceptibility, intermediate resistance and resistance of 0.125–0.25, 2–4 and 4 µg/ml, respectively. Cefaclor and cefixime were less active, with corresponding MIC90s of 1–2, 8–16 and > 16 µg/ml, respectively.     

Correlation of the in vitro antifungal drug susceptibility with the in vivo activity of fluconazole in a murine model of cerebral infection caused by Cryptococcus gattii

Forty Cryptococcus gattii strains were submitted to antifungal susceptibility testing with fluconazole, itraconazole, amphotericin B and terbinafine. The minimum inhibitory concentration (MIC) ranges were 0.5–64.0 for fluconazole, <0.015–0.25 for itraconazole, 0.015–0.5 for amphotericin B and 0.062–2.0 for terbinafine. A bioassay for the quantitation of fluconazole in murine brain tissue was developed. Swiss mice received daily injections of the antifungal, and their brains were withdrawn at different times over the 14-day study period. The drug concentrations varied from 12.98 to 44.60 μg/mL. This assay was used to evaluate the therapy with fluconazole in a model of infection caused by C. gattii. Swiss mice were infected intracranially and treated with fluconazole for 7, 10 or 14 days. The treatment reduced the fungal burden, but an increase in fungal growth was observed on day 14. The MIC for fluconazole against sequential isolates was 16 μg/mL, except for the isolates obtained from animals treated for 14 days (MIC = 64 μg/mL). The quantitation of cytokines revealed a predominance of IFN-γ and IL-12 in the non-treated group and elevation of IL-4 and IL-10 in the treated group. Our data revealed the possibility of acquired resistance during the antifungal drug therapy.     

Interpretive criteria and quality control for antimicrobial susceptibility tests of levofloxacin

To confirm preliminary interpretive breakpoints for prototype 5 µg levofloxacin disks, 490 strains were tested in vitro using commercially manufactured disks. For in vitro susceptibility testing, 5 µg levofloxacin disks can be used with interpretive criteria of 12 mm for resistant (MIC 8.0 µg/ml) and 16 mm for susceptible (MIC 2.0 µg/ml). Proposed quality control limits for tests of levofloxacin are as follows:Escherichia coli ATCC 25922, zones 29–37 mm or MIC 0.008–0.03 µg/ml;Pseudomonas aeruginosa ATCC 27853, zones 19–26 mm or MIC 0.5–2.0 µg/ml;Staphylococcus aureus ATCC 25923, zones 24–31 mm;Staphylococcus aureus ATCC 29213, MIC 0.06–0.25 µg/ml andEnterococcus faecalis ATCC 29212, MIC 0.25–2.0 µg/ml.     

In vitro susceptibility of pneumococci to trovafloxacin,penicillin G,and other antimicrobial agents in the Czech Republic and Slovakia

The in vitro activity of the new naphthyridone trovafloxacin (CP 99,219) was compared with those of penicillin G and six other agents (cefpodoxime, erythromycin, azithromycin, clindamycin, ciprofloxacin, and sparfloxacin) against 316 penicillin-susceptible and -resistant pneumococci isolated in the former Czechoslovakia. Trovafloxacin was very active against strains ofStreptococcus pneumoniae (MIC50 and MIC90 0.25 g/ml). Ciprofloxacin was less active (MIC50 1.0 g/ml, MIC90 2.0 (g/ml), and MICs of sparfloxacin were between those of trovafloxacin and ciprofloxacin (MIC50 and MIC90 both 0.5 g/ml). MICs of cefpodoxime, erythromycin, azithromycin, and clindamycin were higher for strains intermediately resistant or resistant to penicillin than for penicillin-susceptible strains.