Comparative in vitro activities of new quinolones against coryneform bacteria

Abstract

The in vitro activities of eight quinolones against 115 coryneform bacteria (20 Corynebacteriumjeikeium, 15 Corynebacterium minutissimum, 15 Corynebacterium striatum, 25 Corynebacterium urealyticum, 10 Corynebacterium xerosis, 10 Corynebacterium group ANF-1, 10 Corynebacterium group 12, and 10 Listeria monocytogenes) were determined. The MICs of ciprofloxacin, ofloxacin, and sparfloxacin for 90%o of C. jeikeium, C. urealyticum, and C. xerosis isolates tested were >16 ,ug/ml. Those of BAY Y 3118 and clinafloxacin against these species were 0.5 and 1 to 2 ,ig/ml, respectively. The MICs for 90% of all 115 strains tested were 0.5 ,ug/ml for BAY Y 3118, 1 ,ug/ml for clinafloxacin, 2 ,ig/ml for E-5068, 4 gIg/ml for E-5065, and >16 ,ug/ml for ciprofloxacin, ofloxacin, sparfloxacin, and E-4868. An in-house microdilution method was used for susceptibility testing. We followed the guidelines described by the National Committee for Clinical Laboratory Standards (7), with the exception that we used cation-supplemented MuellerHinton broth containing 0.5% Tween 80 (MHT80). Twofold dilutions across a range of 0.015 to 16 ,ug/ml for all eight quinolones were tested. Bacteria from cultures grown on Columbia agar with 5% percent sheep blood for 20 to 24 h were suspended in MHT80 to a concentration of about 108 CFU/ml. This suspension was diluted to obtain 5 x 104 CFU per well. The final volume in each well of the microtiter plate was 100 pLI. Plates were inoculated and were incubated aerobically at 35°C for 18 h or, in the case of plates containing C. jeikeium and C. urealyticum, for 24 h, because with both species there was no visible growth in the control wells without antibiotics at 18 h. The MIC was determined to be the lowest concentration of antimicrobial agent that inhibited visible growth.MICs (range and MICs for 50% [MIC50] and 90% [MIC90] of isolates tested) and the percentage of strains that were inhibited at different concentrations of antibiotics are presented in Table 1. Considering all 115 strains, MIC90s were 0.5 I,g/ml for BAY Y 3118, 1 jig/ml for CLI, 2 ,ug/ml for E-5068, 4 ,ug/ml for E-5065, and >16 jig/ml for CIP, SPA, OFL, and E-4868.The breakpoints of the National Committee for Clinical Laboratory Standards (7) for CIP and OFL were c1 and .2 ,ug/ml, respectively, for susceptibility and .4 and .8 ,ig/ml, respectively, for resistance. Considering these values, an initial report (6) showed that all strains of C. jeikeium were susceptible to CIP, but a more recent study (9) showed that only 36% of C. jeikeium strains were susceptible to this fluoroquinolone. Similarly, initial data concerning C. urealyticum (10) showed that all strains tested were susceptible to OFL; in a later report (2), only 47% of strains were susceptible to OFL and 40% were susceptible to CIP. In our study, 40% of C. jeikeium strains were susceptible to CIP and 50% were susceptible to OFL; in the case of C. urealyticum, 44% of strains were susceptible to CIP and 48% were susceptible to OFL. It is difficult to know whether these discr...

Activities of Gemifloxacin and Five Other Antimicrobial Agents against Listeria monocytogenes and Coryneform Bacteria Isolated from Clinical Samples

“…In a previous study by our group in which we evaluated 86 strains of C. striatum isolated during the period from 1991 to 1994, MIC 50 s and MIC 90 s of 1 and 128 g/ml and 4 and 16 g/ml for gentamicin and ciprofloxacin, respectively, were obtained, values much lower than those obtained in the present study. The decreased activity of ciprofloxacin against other Corynebacterium species (C. amycolatum, C. jeikeium, C. minutissimum, C. urealyticum) may also be inferred when data obtained in the present study are compared to data from previous studies conducted by our group (10,11). For all the strains mentioned above, the MIC 50 s of ciprofloxacin have increased from 4 to Ͼ8 times, whereas the proportions of strains inhibited by ciprofloxacin at 2 g/ml have decreased from 50 to 32% (C. amycolatum), 50 to 10% (C. jeikeium), 87 to 75% (C. minutissimum), and 44 to 10% (C. urealyticum).…”

“…In previous studies we have observed that new quinolones are more active than older compounds against coryneform bacteria (10,11). The objective of the study described here was to determine the in vitro activity of the new fluoroquinolone gemifloxacin in comparison with those of other compounds against different species of coryneform bacteria isolated from clinical samples.…”

“…The concentrations of antimicrobial agents ranged from 0.008 to 16 g/ml (gemifloxacin, ciprofloxacin, vancomycin) or 0.06 to 128 g/ml (all other agents). MICs were determined by a microdilution assay, as described previously (7,(9)(10)(11). Briefly, cation-adjusted Muel-ler-Hinton broth (supplemented with 0.5% Tween 80 when C. jeikeium and C. urealyticum were tested) was used.…”

Nondiphtherial Corynebacterium species isolated from clinical specimens of patients in a university hospital, Rio de Janeiro, Brazil

“…Most recent studies show an alarming rate of antibiotic resistance among Corynebacterium species and other facultative, non-spore-forming, Gram-positive bacilli. Resistance to β-lactams, clindamycin, erythromycin, azythromycin, ciprofloxacin, and gentamicin is quite frequent, with vancomycin, doxycycline, fusidic acid, and prystinamycin being the agents that are most active in vitro (15). Antimicrobial susceptibility tests may be of utility when prescribing antibiotics in cases in which any of the present organisms are involved in clinical infections.…”

Activities of ABT-773 against Listeria monocytogenes and Coryneform Bacteria of Clinical Interest

“…Some reports suggest that other species may be susceptible to commonly used antimicrobial agents, but we lack reliable clinical evidence supporting these in vitro observations. It is necessary to evaluate the activities of new antimicrobial agents against coryneform bacteria of clinical importance (3,7,(10)(11)(12)19).…”