my personal edition > bacterial infections > news


  E-Mail this DGReview to a colleague

DGReview

Linezolid Effective Against Multiple Species of Anaerobes

Linezolid (LZD) is a promising new candidate to treat anaerobic bacterial infections, found to be effective against 265 different strains of bacteria tested by French researchers.

Although there has been an increase in antibiotic resistance of anaerobes worldwide, few studies have addressed anaerobes. Josette Behra-Miellet and colleagues of the University of Lille II, France, reviewed LZD antimicrobial activity against a wide range of anaerobic bacteria isolated from human derived specimens.

Bacterial strains collected by investigators included the B. fragilis group (84), Fusobacterium spp. (21), Porphyromonas spp. (6), Prevotella spp. (44), Veillonella spp. (5), Clostridium spp. (20), Actinomyces spp. (4), Propionibacterium spp. (13), non-sporulating Gram-positive bacilli (12) and Gram-positive anaerobic cocci (56).

LZD minimal inhibition concentrations (MICs) were compared with those of 5 anti-anaerobic reference drugs, including amoxycillin (alone or combined with clavulanic acid), imipenem, clindamycin and metronidazole. For the B. fragilis group, cefoxitin, cefotetan and ticarcillin combined with clavulanic-acid were also investigated. Antibiotic dilutions were incorporated in Brucella blood agar with sterile defibrinated blood (5%) added as a growth medium.

MICs were read on plated after 48 hours of incubation in an anaerobic chamber at 35 to 36°.

Results showed that only LZD inhibited all 265 anaerobes at concentrations of 8 mg/L or less. LZD was effective against all strains of fusobacteria, prevotella and porphyromonas, independent of b-lactamase production.

Across all anaerobes, resistance rates were 1.1% for imipenem, 2.4% for amoxycillin (with/clavulanic acid), 9.8% for metronidazole, and 17% for clindamycin.

The MIC range for LZD was narrow for the B. fragilis group (0.5 to/4 mg/L for 83 strains). While imipenem and metronidazole showed lower MIC90 values than LZD MICs90, resistant strains were detected.

No resistant strains were observed for prevotella and fusobacteria to LZD, amoxycillin-clavulanic acid, imipenem, or metronidazole. LZD MIC50 was 4 mg/L and 1 mg/L for prevotella and fusobacteria, respectively.

Penicillins, imipenem and LZD were effective against Gram-positive anaerobes. Some propionibacteria were resistant to clindamycin but all strains were inhibited at beta-lactam concentrations of 0.25 mg/L or less and at LZD concentrations of 0.5 mg/L or less. Resistance to metronidazole occurred in all strains of actinomyces and Propionibacteria (intrinsic resistance), and also in some strains of peptostreptococci (acquired resistance).

Further clinical trials would be useful, the researchers conclude.
Int J Antimicrob Agents 2003 Jul;22:1:28-34. "Activity of linezolid against anaerobic bacteria"

E-Mail this DGReview to a colleague

To print, use this version