Comparative activity of ciprofloxacin against anaerobic bacteria.

The in vitro activity of ciprofloxacin was assessed against 362 strains of anaerobic bacteria and compared with that of cefoxitin, clindamycin, metronidazole, and mezlocillin. Only 31% of the strains tested were susceptible to ciprofloxacin. The other agents were active against most of the strains tested.     

Comparative antimicrobial activity of levofloxacin and ciprofloxacin against Streptococcus pneumoniae

OBJECTIVES: Levofloxacin has good coverage against both Gram-positive and Gram-negative pathogens. Recent reports demonstrate enhanced activity associated with a higher 750 mg dosage of levofloxacin. The objective of this study was to comparatively evaluate the activity of common regimens of levofloxacin (500 mg) and ciprofloxacin (500 mg), and a higher 750 mg levofloxacin regimen against penicillin susceptible and non-susceptible strains of S. pneumoniae. MATERIALS AND METHODS: An in vitro pharmacodynamic modelling apparatus (PDMA) characterized specific bacterial kill profiles for simulated regimens of levofloxacin and ciprofloxacin against four strains of S. pneumoniae. Total log reduction, time for 3-log reduction and AUC/MIC were determined. RESULTS: Ciprofloxacin was less effective than the levofloxacin regimens against all four study isolates. Ciprofloxacin produced 3-log reduction in only one isolate compared with all four isolates with the levofloxacin regimens. Bacterial regrowth did not occur over 12 h with levofloxacin; however, three of four isolates demonstrated bacterial regrowth with ciprofloxacin. None of the isolates were cleared from the PDMA by ciprofloxacin. The 500 mg levofloxacin regimen cleared two of four isolates and the 750 mg dose of levofloxacin cleared all study isolates. Respective AUC/MIC values for levofloxacin (500 and 750 mg) and ciprofloxacin were 44-89, 63-126 and < or =13, which correlated well with bacterial kill data. CONCLUSIONS: Both levofloxacin regimens were more effective than ciprofloxacin against the study isolates tested. The 750 mg levofloxacin regimen generated more favourable bacterial killing compared with the 500 mg levofloxacin regimen. In addition to using the 750 mg levofloxacin dose for nosocomial infections, this dose may also prove useful for the management of resistant pneumococcal infections.     

Isolation and purification of enterocin E-760 with broad antimicrobial activity against gram-positive and gram-negative bacteria

Strain NRRL B-30745, isolated from chicken ceca and identified as Enterococcus durans, Enterococcus faecium, or Enterococcus hirae, was initially identified as antagonistic to Campylobacter jejuni. The isolate produced a 5,362-Da bacteriocin (enterocin) that inhibits the growth of Salmonella enterica serovar Enteritidis, S. enterica serovar Choleraesuis, S. enterica serovar Typhimurium, S. enterica serovar Gallinarum, Escherichia coli O157:H7, Yersinia enterocolitica, Citrobacter freundii, Klebsiella pneumoniae, Shigella dysenteriae, Pseudomonas aeruginosa, Proteus mirabilis, Morganella morganii, Staphylococcus aureus, Staphylococcus epidermidis, Listeria monocytogenes, Campylobacter jejuni, and 20 other Campylobacter species isolates. The enterocin, E-760, was isolated and purified by cation-exchange and hydrophobic-interaction chromatographies. The proteinaceous nature of purified enterocin E-760 was demonstrated upon treatment with various proteolytic enzymes. Specifically, the antimicrobial peptide was found to be sensitive to beta-chymotrypsin, proteinase K, and papain, while it was resistant to lysozyme and lipase. The enterocin demonstrated thermostability by retaining activity after 5 min at 100 degrees C and was stable at pH values between 5.0 and 8.7. However, activity was lost below pH 3.0 and above pH 9.5. Administration of enterocin E-760-treated feed significantly (P < 0.05) reduced the colonization of young broiler chicks experimentally challenged and colonized with two strains of C. jejuni by more than 8 log(10) CFU. Enterocin E-760 also significantly (P < 0.05) reduced the colonization of naturally acquired Campylobacter species in market age broiler chickens when administered in treated feed 4 days prior to analysis.     

Comparative antimicrobial activity of gatifloxacin tested against Campylobacter jejuni including fluoroquinolone-resistant clinical isolates

Campylobacter jejuni is an important pathogen that causes gastroenteritis, as well as other disease states such as meningitis and septic arthritis. In this study, the Etest (AB BIODISK, Solna, Sweden) results were compared to a reference agar dilution method using gatifloxacin, a new 8-methoxyfluoroquinolone. A total of 53 strains of C. jejuni initially isolated from patients in California and Mexico were tested. Results demonstrated a high correlation (r = 0.88) between the two utilized in vitro dilution methods. In addition, gatifloxacin activity was compared to that of ciprofloxacin, metronidazole, amoxicillin, erythromycin, chloramphenicol, gentamicin, tetracycline, and trimethoprim/sulfamethoxazole using the Etest. Gatifloxacin (MIC₉₀, 4μg/ml) was approximately eight- to 16-fold more potent than ciprofloxacin (Mic₉₀, > 32 μg/ml), a commonly used fluoroquinolone for Campylobacter infections. Eight strains highly resistant to ciprofloxacin (MIC₉₀, > 32 μg/ml) were tested for cross resistance against the newer fluoroquinolones (gatifloxacin, levofloxacin, trovafloxacin) and the rank order of potency was: gatifloxacin (MIC₅₀, 16 μg/ml) > trovafloxacin = levofloxacin (MIC₅₀, > 32 μg/mL). However, only 25% ciprofloxacin-resistant strains were inhibited by ≤ 1 μg/mL of gatifloxacin or trovafloxacin. These results for gatifloxacin against C. jejuni strains must be further assessed in the context of in vivo trials before the clinical role of this new fluoroquinolone can be determined. The Etest appears to be a simple and precise susceptibility test method for testing C. jejuni isolates against fluoroquinolones and other alternative therapeutic agents.     

In vitro activity of CI-934 and other antimicrobial agents against gram-positive and gram-negative bacteria

The activity of CI-934, a new carboxy-quinolone antibiotic, against gram-positive cocci and bacilli and gram-negative bacilli was compared with that of reference antibiotics. CI-934 demonstrated excellent activity against gram-positive organisms, including Corynebacterium sp. In addition, although the activity of CI-934 against gram-negative bacilli was less than that reported for similar agents, it was comparable to that of aminoglycosidic aminocyclitol antibiotics.     

In vitro activity of levofloxacin against gram-positive bacteria

The in vitro activity of levofloxacin was investigated against 256 clinical strains of four gram-positive genera (Staphylococcus, Streptococcus, Enterococcus, and Listeria). Ofloxacin and ciprofloxacin were used as comparators. Uniform susceptibility to levofloxacin was recorded among methicillin-susceptible staphylococci, streptococci other than Streptococcus agalactiae, regardless of their being susceptible, intermediate, or resistant to penicillin (S. pneumoniae) or erythromycin (S. pyogenes and S. pneumoniae), in enterococci other than Enterococcus faecalis and E. faecium, and in Listeria monocytogenes isolates. Moreover, 1 of 22 S. agalactiae isolates and 1 of 19 E. faecium isolates was resistant, and 2 of 19 were intermediate. Resistances to levofloxacin with MIC90s in the resistance range were only observed in methicillin-resistant staphylococci and E. faecalis isolates. In any case, the MICs of ofloxacin and ciprofloxacin were usually 2-4 times higher than those of levofloxacin. In time-kill assays using three test strains (a methicillin-susceptible Staphylococcus aureus isolate, a penicillin-susceptible Streptococcus pneumoniae isolate, and an E. faecalis isolate), the bactericidal activity of levofloxacin was greater than that of ciprofloxacin. Copyright Copyright 1999 S. Karger AG, Basel.     

In vitro activities of daptomycin and other antimicrobial agents against vancomycin-resistant gram-positive bacteria.

A comparative evaluation of daptomycin and eight other antimicrobial agents was performed by the agar dilution technique with 56 strains of vancomycin-resistant gram-positive bacteria, including Leuconostoc, Lactobacillus, and Pediococcus spp. Erythromycin, deptomycin, clindamycin, and gentamicin exhibited the greatest activities, whereas penicillin, ampicillin, and cefotaxime showed moderate activities. The organisms were all highly resistant to vancomycin and cefoxitin.     

In vitro activity of an oral streptogramin antimicrobial, XRP2868, against gram-positive bacteria

The comparative in vitro potency of XRP2868, a new oral semisynthetic streptogramin antibiotic, was evaluated against gram-positive bacteria. XRP2868 inhibited all staphylococci at < or = 1 microg/ml and all non-pneumococcal streptococci at < or = 0.25 microg/ml and was fourfold more potent than quinupristin-dalfopristin against Staphylococcus aureus and Enterococcus faecium.     

Comparative in-vitro activity of ciprofloxacin against non-fermenters

The in-vitro activity of ciprofloxacin, a quinolone-carboxylic acid derivative, was compared with those of carbenicillin, azlocillin, cefsulodin, ceftazidime, tobramycin and amikacin against 187 non-fermenters. Only one of the 131 strains of Pseudomonas spp. was not inhibited by 1 mg/l of ciprofloxacin, while these isolates appeared highly resistant to carbenicillin, azlocillin and cefsulodin. Ciprofloxacin was also the best agent against Flavobacterium, Alcaligenes faecalis and Acinetobacter calcoaceticus with MIC90's respectively of 0.5, 4 and 8 mg/l. This new compound appeared bactericidal, and we found a small or no inoculum effect with ciprofloxacin.     

In vitro activity of LY146032 against gram-positive bacteria

The activity of LY146032 (LY) was evaluated against 269 clinical isolates: 150 Staphylococcus spp. (Staph), 45 enterococci, 51 Clostridium spp., and 23 peptostreptococci. LY was compared to penicillin, metronidazole, imipenem, clindamycin, oxacillin, ciprofloxacin, vancomycin, and ampicillin. LY and oxacillin were tested against Staph by microdilution in cation-supplemented Mueller-Hinton broth (CSMHB), and in unsupplemented Mueller-Hinton broth (MHB). For LY, the MIC 90s in CSMHB were 16-32 dilutions lower. Among the Staph, the MIC 90s for LY, vancomycin, and ciprofloxacin were 4 micrograms/ml, 4 micrograms/ml, and 2 micrograms/ml respectively. The MIC 90s for enterococci by agar dilution were as follows: LY 8 micrograms/ml; ampicillin 4 micrograms/ml; imipenem 4 micrograms/ml; vancomycin 4 micrograms/ml; and ciprofloxacin 2 micrograms/ml. Clindamycin and penicillin were the most effective drugs against peptostreptococci and Clostridia spp., but LY was the most active drug against Clostridium difficile. The bactericidal activity of LY was determined by 24-hr time-kill curves in MHB. These showed a bactericidal effect against enterococci, and a bacteriostatic effect against three of four strains of Staph. Synergy was demonstrated against enterococci and Staph when LY was tested with aztreonam, ceftriaxone, or tobramycin. LY is a promising new agent against gram-positive bacteria, including methicillin resistant strains of staphylococci and enterococci.     

In vitro activity of telavancin against resistant gram-positive bacteria

The in vitro activity of telavancin was tested against 743 predominantly antimicrobial-resistant, gram-positive isolates. Telavancin was highly active against methicillin-resistant staphylococci (MIC(90), 0.5 to 1 microg/ml), streptococci (all MICs, < or =0.12 microg/ml), and VanB-type enterococci (all MICs, < or =2 microg/ml). Time-kill studies demonstrated the potent bactericidal activity of telavancin.     

Protection of Pseudomonas aeruginosa against ciprofloxacin and beta-lactams by homologous alginate.

Pseudomonas aeruginosa-derived alginate but no other neutral and negatively charged polysaccharides protected mucoid and nonmucoid strains of that organism against ciprofloxacin, gentamicin, ticarcillin, and ceftazidime. Data indicate that alginate has an intrinsic protective effect which is independent of diffusion, charge, or biofilm phenomena.     

In vitro activity of sparfloxacin and six reference antibiotics against gram-positive bacteria.

The in vitro activity of sparfloxacin, a new fluoroquinolone, was assessed against 234 gram-positive bacterial isolates by agar dilution (10(4) CFU/spot). Sparfloxacin activity was compared with that of ciprofloxacin and five other antibiotics. Sparfloxacin was the most active drug tested against methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci (MIC90, 0.125-0.25 mg/l). Sparfloxacin was also the most active drug tested against Enterococcus faecalis (MIC90, 1 mg/l) and showed equal activity against gentamicin-susceptible and gentamicin-resistant (MIC greater than 2,000 mg/l) enterococci. Sparfloxacin was the most active quinolone tested against Streptococcus pneumoniae and S. pyogenes (MIC90, 1 mg/l). Most Corynebacterium jeikeium showed exquisite susceptibility to sparfloxacin (MIC, 0.06-0.25 mg/l). For MRSA, time-kill curves showed sparfloxacin to be rapidly bactericidal at the MIC of the organism. Sparfloxacin showed greater and more sustained bactericidal activity than ciprofloxacin and vancomycin at 1x and 2x the MIC. Reduction in the activity of sparfloxacin occurred with decreased agar pH (from 7.0 to 6.0) and increased bacterial inoculum. Sparfloxacin showed superior activity compared to reference drugs against most gram-positive bacteria.     

Comparative in-vitro activity of LY146032 and eight other antibiotics against gram-positive bacteria isolated from children

LY146032, a cyclic peptide antibiotic active against many Gram-positive bacteria, was compared to methicillin, vancomycin, clindamycin, cefuroxime and gentamicin against methicillin-resistant and methicillin-susceptible strains of Staphylococcus aureus and Staph. epidermidis. LY146032 was uniformly active against clinical isolates of staphylococci, inhibiting 90% of strains of Staph. aureus and Staph. epidermidis at a concentration of 0.5 mg/l. Vancomycin was slightly less active than LY146032 against Staph. aureus and Staph. epidermidis, inhibiting 90% of strains at concentrations of 1.0 and 2.0 mg/l, respectively. All other antibiotics tested were less active than LY146032 or vancomycin against staphylococci. LY146032 was compared to penicillin, ampicillin, vancomycin and chloramphenicol against strains of Streptococcus pneumoniae, group B streptococcus, group D streptococcus (enterococcus) and Listeria monocytogenes and was found to inhibit 90% of the strains at concentrations of 0.25, 1.0, 32.0 and 16.0 mg/l respectively. The combination of LY146032 and chloramphenicol was antagonistic in vitro for one strain each of Staph. aureus and group D streptococcus and showed indifference against other strains of Staph. aureus(2), Staph. epidermidis(2), group D streptococcus(1) and L. monocytogenes(2). LY146032 in combination with gentamicin showed indifference against the same bacteria. On the basis of its in-vitro activity, LY146032 appears to be a promising agent for the treatment of serious community- and hospital-acquired staphylococcal infections.     

In vitro activity of teichomycin against isolates of gram-positive bacteria

The in vitro activity of teichomycin has been evaluated against 189 clinical isolates of Staphylococcus aureus, Staphylococcus epidermidis and group D streptococci. Teichomycin was as active as vancomycin, a chemically related antibiotic, on staphylococci and inhibited the in vitro growth of methicillin-resistant strains at the same concentration necessary to inhibit the sensitive ones. Against group D streptococci teichomycin was about three times more active than vancomycin (MIC50 = 0.125 mg/l, MIC90 = 0.4 mg/l). MBC:MIC ratios of both drugs against staphylococci were comparable, but teichomycin had higher bactericidal activity against group D streptococci, as shown also by killing curves. The activity of teichomycin was not significantly affected by variation of pH, even if the maximum activity was achieved at neutral pH, or by different methods of MIC evaluation. The antibiotic seemed more active when tested with a low inoculum (10(3)-10(5)/ml): a two- to threefold increase in MIC was observed at an inoculum of 10(7)/ml. A reduction of the in vitro activity could be shown when Penassay broth was used as culture medium.     

Comparative activity of cefditoren and other oral beta-lactams against nonpneumococcal streptococci

BACKGROUND: In vitro studies of cefditoren activity have focused primarily on Streptococcus pneumoniae and other bacterial species isolated from patients with respiratory infections, but relatively few reports have been published describing the activity of cefditoren against clinical isolates of nonpneumococcal streptococci. METHODS: Cefditoren activity was determined by broth microdilution (M7-A5, NCCLS, 2000) for 450 viridans group streptococci, 917 Streptococcus pyogenes and 800 other beta-hemolytic streptococci collected throughout the US during 1999-2000. RESULTS: Against viridans group streptococci, cefditoren (MIC(90), 0.5 microg/ml) was 4- to 32-fold more active than the other beta-lactams tested (penicillin ampicillin, amoxicillin-clavulanate, cefprozil and cefuroxime). The difference in activity between cefditoren and the other beta-lactams was greater for penicillin-nonsusceptible isolates (MIC(90s), 1 microg/ml versus 8-32 microg/ml) than among penicillin-susceptible isolates (MIC(90s), 0.12 versus 0.25- 1 microg/ml). Cefditoren also demonstrated potent activity against S. pyogenes (MIC(90), 0.015 microg/ml) and other beta-hemolytic streptococci (MIC(90), 0.06 microg/ml), comparable to that of the other beta-lactams. CONCLUSIONS: The activity demonstrated by cefditoren against nonpneumococcal streptococci, including beta-lactam- and macrolide-resistant isolates, suggests that this agent holds promise as therapy for infections caused by all clinically significant species of streptococci.     

In-vitro activity of ciprofloxacin and other agents against oral bacteria

The susceptibility of 102 bacterial strains isolated from oral infections to ciprofloxacin, penicillin V, tetracycline and metronidazole was assessed by an agar dilution technique. Penicillin V was the most effective of the antimicrobials, with only three isolates resistant, while widespread resistance to tetracycline was seen. Metronidazole, as expected, was extremely effective against anaerobic isolates. Ciprofloxacin exhibited intermediate activity with the majority of MICs in the range of 1-4 mg/l. However, resistance was seen, particularly among Actinomyces and Wolinella species. In was concluded that, on the basis of these results, ciprofloxacin has limited potential for the treatment of oral infection but its potential for use in prophylaxis in head and neck surgery remains to be determined.     

In vitro activity of ciprofloxacin against aerobic gram-negative bacteria

For 177 gram-negative isolates, the MICs for ciprofloxacin ranged from 0.02 microgram/ml (Escherichia coli) to 0.31 microgram/ml (Pseudomonas aeruginosa). In time-kill curves, ciprofloxacin at 8 X the MIC almost completely killed 10(6) CFU of P. aeruginosa by 24 h. Ciprofloxacin at 4 X the MIC allowed bacterial regrowth by 24 h, with development of partial resistance to ciprofloxacin.     

Interactions of ciprofloxacin with clindamycin, metronidazole, cefoxitin, cefotaxime, and mezlocillin against gram-positive and gram-negative anaerobic bacteria.

A total of 598 clinical isolates of anaerobic bacteria were tested against ciprofloxacin by the agar dilution technique with 10(5) CFU on Wilkins-Chalgren medium. Selected strains representative of the six major genera of anaerobes relatively resistant to the quinolones were tested for interactions with ciprofloxacin in combination with clindamycin, metronidazole, cefoxitin, cefotaxime, or mezlocillin by using a checkerboard agar dilution technique. Cefotaxime-ciprofloxacin and clindamycin-ciprofloxacin were the most effective combinations, with 16% of all isolates and 44% of the Bacteroides fragilis group isolates responding synergistically to the former combination and 9% of all isolates and 37% of Peptostreptococcus isolates responding synergistically to the latter. Occasional synergy was seen with all other antibiotic combinations except for metronidazole-ciprofloxacin. Likewise, synergism was seen with all groups of anaerobes except for Fusobacterium species. Antagonistic interactions were observed only with a Peptostreptococcus intermedius strain tested against clindamycin-ciprofloxacin. These data suggest that combinations of ciprofloxacin with these agents may be useful for certain resistant anaerobic infections.