Ecological Effects of Linezolid versus Amoxicillin/Clavulanic Acid on the Normal Intestinal Microflora

Abstract

Twelve healthy subjects (6 females, 6 males; age range 18-40 y) participated in this trial. Linezolid was given as 600 mg tablets b.i.d. for 7 d and amoxicillin/clavulanic acid as 1000 mg tablets o.d. for 7 d. The washout period between the administration of the 2 antibacterial agents was 4 weeks. Faecal samples were collected prior to administration (Days -2 and -1), during administration (Days 4 and 8) and after administration (Days 14, 21 and 35) for microbiological analyses. The samples were diluted in pre-reduced media and inoculated aerobically and anaerobically on non-selective and selective media. Different colony types were identified to genus level by morphological, biochemical and molecular analyses. During the administration of linezolid, enterococci in the intestinal aerobic microflora were markedly suppressed while Klebsiella organisms increased in number. In the anaerobic microflora, the numbers of bifidobacteria, lactobacilli, clostridia and Bacteroides decreased markedly while no impact on the other anaerobic bacteria was observed. The microflora was normalized in all volunteers after 35 d. Amoxicillin/clavulanic acid administration caused increased numbers of enterococci and Escherichia coli in the aerobic intestinal microflora while numbers of bifidobacteria, lactobacilli and clostridia decreased significantly. Clostridium difficile strains were recovered from 3 of the volunteers. At the last visit, the intestinal microflora of the volunteers had returned to normal levels. The administration of linezolid mainly had an impact on the gram-positive bacteria and linezolid thus had an ecological profile different from that of amoxicillin/clavulanic acid.

The Emergence of Linezolid Resistance among Enterococci in Intestinal Microbiota of Treated Patients Is Unrelated to Individual Pharmacokinetic Characteristics

“…Similar findings were previously reported, however, for healthy volunteers and only for intestinal enterococci (10). This reduction in colonization could be due to the antibiotics coadministered with linezolid.…”

“…After 7 days, linezolid suppressed enterococci in the volunteers' intestinal microbiotas. Simultaneously, linezolid decreased the concentration of bifidobacteria, lactobacilli, clostridia, and Bacteroides (10). In mice, linezolid promoted the colonization of Klebsiella pneumoniae with extended-spectrum ␤-lactamase (11).…”

A Detrimental Role of Immunosuppressive Drug, Dexamethasone, During Clostridium difficile Infection in Association with a Gastrointestinal Microbial Shift

“…However, information about the pathogenesis of Parabacteroides in patients is still lacking. An approximate return to pretreatment conditions also occurred in this study within days after cessation of treatments, as described by others using different antibiotics [7, 15]. The proportion of Lactobacillus increased while those of Parabacteroides decreased days after cessation of the treatments (Fig.…”

Analysis of the Phase 3 ESTABLISH Trials of Tedizolid versus Linezolid in Acute Bacterial Skin and Skin Structure Infections

“…The impact of tedizolid on normal intestinal flora was previously shown to be limited and reversible, with no signs of microbiological substitution after 7 days of i.v. or oral administration in healthy subjects (32), while another study showed linezolid to result in marked alterations in gut flora composition (33). In addition, the lower dosing frequency of tedizolid (once daily versus twice daily with linezolid) may also somewhat reduce the risk of developing GI AEs overall.…”