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Antimicrobial Agents and Chemotherapy, June 2003, p. 2030-2035, Vol. 47, No. 6
0066-4804/03/$08.00+0 DOI: 10.1128/AAC.47.6.2030-2035.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Laboratory of Bacteriology, EMI-U 9933,2 Clinical Investigation Center,1 Department of Epidemiology and Biostatistics, Bichat-Claude Bernard Hospital,3 Microbiology Laboratory, Ambroise-Paré Hospital, Paris, France4
Received 13 September 2002/ Returned for modification 9 December 2002/ Accepted 5 March 2003
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(This work was presented in part at the 41st Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago, Ill., 16 to 19 December 2001.)
Here, we compared the emergence of resistance in the commensal microflora of 2 groups of 25 fully informed healthy (by history, physical examination, routine laboratory tests, and electrocardiogram) adult (19 to 44 years) male volunteers, treated with either amoxiclav or telithromycin in a single-center, randomized, open-label, parallel-group comparative study. The volunteers had not taken antibiotics for 3 months and had a normal intestinal transit and a fecal count of enterobacteria greater than 104 CFU/g of feces at enrollment. They received either 2 tablets of 400 mg of telithromycin (Aventis Pharma, Paris, France) once daily for 7 days or 1 g of amoxicillin and 125 mg of clavulanic acid (GlaxoSmithKline, Paris, France) three times daily for 7 days. They were not hospitalized, but they returned to the center for all drug intakes and for follow-up visits (days 8, 14, 21, and 45). They were asked to continue their usual life and diet and allowed no other medication. Safety was evaluated at days 0 and 8, and adverse events were recorded by medical examination daily during treatment and then at days 14, 21, and 45. Serum samples were assayed for telithromycin (9) or amoxiclav (10) before the morning dose on days 3, 5, and 8 and 1, 2, 3, and 4 h after the morning dose on day 5 in 20 subjects per group.
Fecal, cutaneous, and oropharyngeal samples were collected on days -1, 8, 14, 21, and 45 by using sterile containers for fecal samples, a VLM E0115 apparatus (Verre-Labo Mula, Corbas, France) for cutaneous washes (2 ml), and BBL Culturette swabs (Becton-Dickinson, Cockeysville, Md.) discharged in 2 ml of broth for oropharyngeal samples. All samples were immediately transferred to the laboratory and analyzed within 3 h of arrival and blind with regard to the treatment administered. The limit of detection of the quantitative microbiological assays was 102 CFU/ml. In each ecosystem, we focused on a specific microbiological species to analyze the ecological impact of treatments. In the feces, yeasts were chosen because their counts were reported to increase after amoxiclav treatment (14, 19, 26) but not after telithromycin treatment (9), and Clostridium difficile was chosen because of its role in antibiotic-associated intestinal side effects (3). Coagulase-negative staphylococci (CNS) and nongroupable streptococci (NGS) were chosen as target organisms in the cutaneous and pharyngeal flora because they can be the source of resistance in related pathogenic species such as Staphylococcus aureus (27) and Streptococcus pneumoniae (25), respectively, within these ecosystems. Fecal samples were assayed qualitatively and quantitatively for yeasts on Chromagar medium (Biomérieux, Marcy-l'Etoile, France) and qualitatively for Pseudomonas aeruginosa and S. aureus on Cetrimide (Biomérieux) and Chapman agar (Biomérieux), respectively. C. difficile was detected on CCFA agar (Biomérieux) and by toxin assay (toxins A and B; Premier Bioscience, Inc., Cincinnati, Ohio).
Skin staphylococci were counted on Chapman agar, either free of antibiotics for total counts or containing 1 mg of erythromycin/liter, 1 mg of telithromycin/liter, or 2 mg of methicillin/liter for counts of subpopulations with decreased susceptibility (DS) to the corresponding antibiotics.
The presence of S. pneumoniae, Moraxella catarrhalis, and Haemophilus influenzae in oropharyngeal swabs was detected on blood and chocolate agar. Total oropharyngeal NGS were counted on 5% sheep blood Columbia agar containing 10 mg of colimycin/liter and 15 mg of nalidixic acid/liter (CNA agar), and those with DS to erythromycin, telithromycin, or amoxiclav were counted on the same plates but supplemented with 1, 1, or 4 mg of the corresponding antibiotic/liter, respectively. The prevalence of streptococci coresistant to erythromycin, telithromycin, and amoxicillin was determined by testing the susceptibility of clones isolated from plain CNA agar by using the disk diffusion technique, as recommended previously (6). We used this technique in that particular case because the detection of coresistance with screening plates containing several antibiotics has never been used in the literature.
The sample size was calculated to demonstrate a difference of at least 2 decimal logarithms between yeast counts at day 8 (standard error, 2.3; power, 80%; type I error, 5%), by using the two-tailed Wilcoxon exact test, adjusted for the presence of yeasts at day -1. Secondary comparisons between the 2 groups were restricted to 6 variables: the area under the curve (trapezoidal rule) for the fecal yeasts between days -1 and 45 (Wilcoxon exact test stratified on the presence of yeast at day -1), the prevalence of C. difficile at day 8, and the prevalence of colonization by cutaneous staphylococci and oropharyngeal streptococci at days 8 and 45 (Fisher's exact test or Cochran-Mantel-Haenzel exact test if the tested factor [presence or absence of strains] was present at day 1). We used a global type I error of 4.5%, controlled for multiple testing by the Simes procedure (21). The incidence of treatment-related digestive adverse events was compared by using Fisher's exact test.
Effects of treatments on intestinal flora. The mean fecal density of yeasts increased during treatment between days -1 and 8 (2.50 ± 0.85 versus 3.32 ± 1.39 CFU/g of feces for amoxiclav, and 2.48 ± 0.86 versus 3.16 ± 1.16 CFU/g of feces for telithromycin) (Fig. 1), decreased progressively, and were close to the baseline at day 21 with no significant between-group differences in counts at day 8 or in areas under the curves. Pretreatment prevalences of fecal yeast colonization were of 7 of 25 (28%) and 8 of 25 (32%) in the amoxiclav and telithromycin groups, respectively, increased to 14 of 25 (56%) and 15 of 25 (60%) at day 8, and then returned to baseline (9 of 25, 36%) by day 21 in the telithromycin group but were still elevated at day 45 in the amoxiclav group (13 of 24, 54%) (Table 1). C. difficile was isolated only in 4 volunteers (one with severe intestinal symptoms) from the amoxiclav group (data not significant). No P. aeruginosa or S. aureus was isolated.
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FIG. 1. Effect of 7 days of oral treatment of human volunteers with either amoxiclav (1 g of amoxicillin and 125 mg of clavulanic acid 3 times/day) or telithromycin (800 mg 1 time/day) on fecal yeast counts (25 volunteers/treatment group). The line represents the mean counts. , individual data.
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TABLE 1. Effect of 7 days of oral treatment of human volunteers with either amoxiclav (1 g of amoxicillin and 125 mg of clavulanic acid 3 times/day) or telithromycin (800 mg 1 time/day) on the prevalence of fecal yeast colonization (25 volunteers/treatment group)
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TABLE 2. Effects of 7 days of oral treatment of human volunteers with either amoxiclav (1 g of amoxicillin and 125 mg of clavulanic acid 3 times/day) or telithromycin (800 mg 1 time/day) on the prevalence of cutaneous colonization by CNS (25 volunteers/treatment group)
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FIG. 2. Effect of 7 days of oral treatment of human volunteers with either amoxiclav (1 g of amoxicillin and 125 mg of clavulanic acid 3 times/day) or telithromycin (800 mg 1 time/day) on cutaneous counts of CNS (25 volunteers/treatment group). Lines represent mean counts. , individual data. (A) Total CNS; (B) CNS with DS to erythromycin; (C) CNS with DS to methicillin; (D) CNS with DS to telithromycin.
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TABLE 3. Influence of 7 days of oral treatment of human volunteers with either amoxiclav (1 g of amoxicillin and 125 mg of clavulanic acid 3 times/day) or telithromycin (800 mg 1 time/day) on the prevalence of oral colonization by NGS (25 volunteers/treatment group)
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FIG.3. Effect of 7 days of oral treatment of human volunteers with either amoxiclav (1 g of amoxicillin and 125 mg of clavulanic acid 3 times/day) or telithromycin (800 mg 1 time/day) on oropharyngeal counts of NGS (25 volunteers/treatment group). Lines represent mean counts. , individual data. (A) Total NGS; (B) NGS with DS to erythromycin; (C) NGS with DS to amoxicillin; (D) NGS with DS to telithromycin.
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One volunteer (from the amoxiclav group) was colonized by S. pneumoniae (day -1), and 9 volunteers (5 from the amoxiclav group and 4 from the telithromycin group) were colonized by Haemophilus spp. No M. catarrhalis was isolated.
Adverse events. Twelve and 17 adverse events (all and 12, respectively, were treatment related) were reported by 8 and 13 subjects (32 and 52%) in the telithromycin and amoxiclav groups, respectively. None led to the discontinuation of treatment. Most affected the digestive system, and these were significantly less frequent in the telithromycin group than in the amoxiclav group (1 [4%] versus 8 [32%]; P = 0.02). Treatments had no significant effects on clinical or laboratory parameters, vital signs, physical examination, or electrocardiogram.
Residual drug concentrations at days 3, 5, and 8 were undetectable for amoxicillin (except for one subject at day 5) and clavulanic acid, whereas they remained stable and above the quantification limit for telithromycin at 0.033 ± 0.018 mg/liter (0.01 to 0.08), 0.039 ± 0.016 mg/liter (0.02 to 0.08), and 0.037 ± 0.016 mg/liter (0.02 to 0.07) at days 3, 5, and 8, respectively. The maximum concentrations of telithromycin, amoxicillin, and clavulanic acid in serum were 1.89 ± 1.24, 11.16 ± 4.32, and 1.99 ± 0.8 mg/liter, respectively. The times to the maximum concentrations of telithromycin, amoxicillin, and clavulanic acid in serum were 1.29 ± 0.28, 1.40 ± 0.21, and 1.04 ± 0.22 h, respectively. The results for telithromycin are from 20 subjects, and the results for amoxicillin and clavulanic acid are from 16 subjects (clavulanic acid was undetectable in 4 subjects, even at 1.5 h).
In all, we described here the emergence of bacteria with DS to the antibiotic administered in the pharynx and on the skin of humans during treatments with amoxiclav or telithromycin, together with the emergence of yeasts in the feces. This emergence was much more frequent than any other side effect and it persisted for some time after the end of treatment. Microorganisms with DS to the treatment received were selected in both groups of volunteers in all the ecosystems studied. In the feces, the increase in yeast counts was very important but did not differ between groups, although previously the emergence of yeast had been reported after treatment with amoxiclav (14, 19, 26) but not telithromycin (9). This may be due to differences in the selection of volunteers or in stool conservation methods. Intestinal adverse effects were significantly more frequent in the amoxiclav group, but colonization by C. difficile and resistance to colonization by P. aeruginosa and S. aureus were not. The remnants of the ecological impact of antibiotic treatments over the weeks that followed the discontinuation of therapy that we observed were previously reported for intestinal (16, 20) and oral bacteria (11, 22). The method used was strict. The volunteers were monitored daily, all drug intake was monitored, and concentrations of drugs in plasma were measured. Volunteers had not taken antibiotics for 3 months and had fecal counts of enterobacteria greater than 104 CFU/g at inclusion. We chose to evaluate the impact of treatments by screening strains with DS to antibiotics on selective agar supplemented with antibiotics, first, because this method is more sensitive than testing individual isolates grown on nonselective agar for susceptibility (15) and, secondly, because it yields both qualitative and quantitative results. Concentrations in agar lower than the recommended breakpoints (6) were chosen to increase the sensitivity of the screening. To avoid any confusion, we described here bacteria that grew on the corresponding antibiotic-containing agar as DS to the given antibiotic (and not as resistant). We used the term resistant only for NGS coresistant to erythromycin, telithromycin, and amoxiclav, as tested by the disk diffusion technique.
Overall, our results demonstrated that the simultaneous emergence of microorganisms with DS to antibiotics in major human ecosystems after antibiotic treatments was much more frequent than any other drug-related side effect. Differences were observed between the effects of amoxiclav and telithromycin regimens, but they were essentially related to the spectrum of the antibiotic ingested and not as marked for their magnitude for the phenotype of DS of the bacteria selected.
We thank C. Carbon and C. Safran for fruitful discussions, M. Dreyfus for English revision, and M. J. Julliard and S. Couriol for secretarial assistance.
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