[Implication of ermX genes in macrolide- and telithromycin-resistance in Corynebacterium jeikeium and Corynebacterium amycolatum]

The activity of seven macrolides, clindamycin and telithromycin against clinical isolates of Corynebacterium spp. was studied. Of these, 36 isolates were identified as C. jeikeium and 57 as C. amycolatum. The frequency of resistance to erythromycin and other macrolides as well as clindamycin was high, with CMI(90) >256 microg/ml. Telithromycin showed the best activity, with 52.3% of C. amycolatum and 70% of C. jeikeium erythromycin-resistant strains susceptible to this ketolide. All strains had the MLSb constitutive phenotype. The ermX gene was present in all erythromycin-resistant strains, and in C. amycolatum was 100% homologous with that of C. striatum and C. diphtheriae.

[Activity of new quinolones against clinical isolates of Corynebacterium species]

The activity of six quinolones (ciprofloxacin, levofloxacin, trovafloxacin, moxifloxacin, clinafloxacin and grepafloxacin) against 86 clinical isolates of Corynebacterium spp. obtained from different clinical sources was studied. Of these, 30 isolates were identified as C. jeikeium, 30 as C. urealyticum and 26 as C. amycolatum. C. amycolatum was the most resistant species, with 85.5% of the strains analyzed resistant to all the quinolones studied. Clinafloxacin showed the best activity against these species with a concentration range between <0.01 and 8 mg/l, and MIC50 and MIC90 64 and 32 times lower, respectively, than the MICs of ciprofloxacin. The majority of the isolates (90%) of C. jeikeium and C. urealyticum were susceptible to all the quinolones studied. Only 9.9% of the C. jeikeium strains and 13.2% of the C. urealyticum strains were resistant to ciprofloxacin, which showed the lowest activity of the antimicrobial agents evaluated. Clinafloxacin, grepafloxacin and moxifloxacin were the most active quinolones against these two multiresistant species.

[In vitro activity of new quinolones against clinical strains of Staphylococcus aureus of the wild type and with mutations characterized by gyrA, gyrB and grlA]

The aim of this study was to determine the in vitro activity of five quinolones against clinical strains of methicillin-susceptible and -resistant Staphylococcus aureus clinical isolates characterized at the molecular level with respect to the presence of mutations in genes coding for resistance to quinolones (grlA, gyrA and gyrB). The relationship between the mutations found and the activities of these quinolones was also analyzed. Trovafloxacin was the most active against methicillin-susceptible S. aureus and showed good activity against methicillin-resistant S. aureus, with a MIC90 of 2 mg/l. The grlA-gyrA double mutation was the most frequent (55% of the strains). Single mutation in grlA was detected only in 5% of strains; 39% of strains showed a wild-type genotype. The grlA-gyrA double mutants presented a high level of resistance against the fluoroquinolones tested except for trovafloxacin, with the MIC ranging between 0.5 and 4 mg/l. Wild-type strains were susceptible to all the fluoroquinolones tested and the single grlA mutants had a low level of quinolone resistance but were still below the breakpoint for resistance. Trovafloxacin and sparfloxacin were less affected by this mutation.

Appearance of resistance to meropenem during the treatment of a patient with meningitis by Acinetobacter

A case is reported of a patient who developed Acinetobacter meningitis after an external ventricular drainage system had been fitted for control of intracranial pressure. During the process, nine strains of Acinetobacter isolated from her cerebrospinal fluid were indistinguishable by analysis of total genomic DNA by pulse-field gel electrophoresis. The first eight strains were sensitive to meropenem and imipenem (MICs < 1 g/l). The MIC of the last one, which had been recovered after 32 days during two courses of treatment with meropenem, increased to > 32 g/l for meropenem, while with imipenem the increase was minimal (MIC = 1.5 g/l). The microorganism persisted in the central nervous system despite the administration of different antimicrobials, including intraventricular aminoglycosides and six changes in the external ventricular system. The patient died 68 days after admission to the intensive care unit from bilateral cerebral ischemic lesions, intraventricular hemorrhage and cerebral edema with endocraneal hypertension, the Acinetobacter ventriculitis also contributing to this state.