ANTIMICROBIAL AGENTS
AND
CHEMOTHERAPY, Mar. 1991,
p.
Vol. 35, No. 3
548-552
0066-4804/91/030548-05$02.00/0 Copyright X3 1991, American Society for Microbiology
Effects of Roxithromycin on Fecal Bacteria in Human Volunteers and Resistance to Colonization in Gnotobiotic Mice SOPHIE PECQUET,1 ELISABETH CHACHATY,1 CYRILLE TANCREDE,' AND ANTOINE ANDREMONTl.2* Laboratoire d'Ecologie Microbienne, Institut Gustave-Roussy, Villejuif,1 and Laboratoire de Microbiologie, Faculte de Pharmacie, Chatenay-Malabry,7 France Received 20 June 1990/Accepted 8 December 1990
The ecological impact of roxithromycin given orally at 300 mg/day on the intestinal floras in six human volunteers was studied. The resulting fecal concentrations of active roxithromycin were in the range of 100 to 200 ,ug/g of feces. Consecutive modifications in the composition of the fecal floras were limited to a decrease in counts of total members of the family Enterobacteriaceae. The rest of the intestinal floras, including the predominant anaerobic floras, changed little. No overgrowth of Pseudomonas aeruginosa, staphylococci, fungi, or highly erythromycin-resistant strains of the family Enterobacteriaceae was observed. The strains of Enterobacteriaceae and of anaerobes isolated during treatment were not markedly more resistant to roxithromycin than those isolated before treatment started. Changes in intestinal resistance to colonization by exogenous microorganisms in gnotobiotic mice inoculated with human fecal flora were studied and were also found to be minimal. The impact of oral roxithromycin on the intestinal microbiota appears to be weaker than that previously observed with oral erythromycin, perhaps because the concentrations of roxithromycin in the feces were lower than those previously found for erythromycin.
MATERIALS AND METHODS Human volunteers. Six healthy, fully informed adult volunteers, ages 25 to 42 years, were included in the study. None had taken antibiotics for at least 1 month before the study. Oral roxithromycin was administered twice daily for 5 days in doses of 150 mg. Blood samples were drawn 2 h after the morning dose on the first and last days of treatment. Freshly passed fecal samples were obtained once before treatment, daily during treatment, and 1 week thereafter. Gnotobiotic mice. Adult germ-free C3H mice (Centre de Selection des Animaux de Laboratoire, Orleans, France) were kept in plastic Trexler-type isolators. They were fed a locally prepared diet (4) sterilized by gamma irradiation and either supplemented with 10 g of roxithromycin per kg of diet or left without roxithromycin. Autoclaved drinking water at pH 3 was given ad libitum. Some of the mice used were in the germ-free state. The remainder were each given a complex human fecal flora by intragastric and intrarectal inoculation of a dilution of the original flora, as previously described (4). The human donor was chosen from among the volunteers. Germ-free and human-flora-associated (HFA) mice were each divided into two groups. One germ-free and one HFA group were left untreated, and one group of each type was treated with roxithromycin; for the treated HFA group, 2 weeks was allowed to elapse between the introduction of the fecal flora and the beginning of roxithromycin administration. Both treated and untreated mice were challenged with various strains 2 weeks after roxithromycin administration was started with the treated groups. The challenge was performed, as previously described, by intragastric inoculation of 1 ml of a culture containing 108 CFU of one of the challenge strains per ml (4). Challenge strains. Escherichia coli H10407, Shigella flexneri 115DKR, Vibrio cholerae 569B, Salmonella typhimurium IGR9, and Campylobacter jejuni IGR6 were isolated from diarrheal patients. Pseudomonas aeruginosa IGR54, Staphylococcus aureus IGR53, and Candida albicans IGR41 were from our laboratory collection. The MICs of erythro-
Macrolide antibiotics have been used for many years because they are highly effective agents against gram-positive pathogenic bacteria. Recently, however, it was shown that oral treatment with erythromycin base, the reference drug of the macrolide class of antibiotics, was followed by a sharp decrease in the concentrations of intestinal aerobic gram-negative bacteria (6). This paradoxical effect of erythromycin was due to its accumulation in the colon, resulting in concentrations higher than those required to inhibit members of the family Enterobacteriaceae in vitro (6). Otherwise, erythromycin did little to alter either the composition of the fecal flora or the resistance to colonization by exogenous microorganisms (4). During treatment with erythromycin, a noticeable shift toward resistance in surviving bacteria was observed (4), but colonization with highly erythromycin-resistant (HER) strains of Enterobacteriaceae, i.e., strains for which the MIC was greater than 512 Vig/ml, was rare (5). Therefore, oral treatment with erythromycin is potentially useful for selective intestinal tract decontamination, a technique which has been proposed both for prophylaxis of infection in patients who have hematological malignancies or who are undergoing mechanical ventilation (10) and for the prevention of traveler's diarrhea (6, 15). Roxithromycin is a newly introduced macrolide antibiotic which differs from erythromycin in its chemical composition (14) and which exhibits greater intestinal absorption and bioavailability than erythromycin (11). Its recommended daily dosage is lower than that of erythromycin (5 versus 30 to 50 mg/kg of body weight per day). It was not known whether this lower dosage implied that roxithromycin had a weaker impact than erythromycin on the intestinal flora and on colonization resistance, and the present study was designed to elucidate this question.
* Corresponding author. 548
ROXITHROMYCIN AND INTESTINAL FLORA
VOL. 35, 1991
549
TABLE 1. Fecal counts of challenge strains in gnotobiotic mice and MICs of roxithromycin and erythromycin Fecal counts' for:
MIC (,ug/ml)
HFA mice' Monoassociated mice' StrainbHFmie During Before During Before Roxithromycin Erythromycin treatment treatment treatmentd treatment
E. coli H10407 S.flexneri 115DKR
S. typhimurium IGR9 P. aeruginosa IGR54 S. aureus IGR53 V. cholerae 569B C. jejuni IGR6 C. albicans IGR41
32 64 64 64 16 0.05 0.03 >1,024
128 512
128 64 64 0.05 0.03 >1,024
NDe
10.4 t 0.4 9.6 t 0.2
6.4 t 2.0 6.6 t 1.0
8.3 t 0.3
LEf
ND 8.0 t 1.4 9.2 t 1.1
AND
CHEMOTHERAPY, Mar. 1991,
p.
Vol. 35, No. 3
548-552
0066-4804/91/030548-05$02.00/0 Copyright X3 1991, American Society for Microbiology
Effects of Roxithromycin on Fecal Bacteria in Human Volunteers and Resistance to Colonization in Gnotobiotic Mice SOPHIE PECQUET,1 ELISABETH CHACHATY,1 CYRILLE TANCREDE,' AND ANTOINE ANDREMONTl.2* Laboratoire d'Ecologie Microbienne, Institut Gustave-Roussy, Villejuif,1 and Laboratoire de Microbiologie, Faculte de Pharmacie, Chatenay-Malabry,7 France Received 20 June 1990/Accepted 8 December 1990
The ecological impact of roxithromycin given orally at 300 mg/day on the intestinal floras in six human volunteers was studied. The resulting fecal concentrations of active roxithromycin were in the range of 100 to 200 ,ug/g of feces. Consecutive modifications in the composition of the fecal floras were limited to a decrease in counts of total members of the family Enterobacteriaceae. The rest of the intestinal floras, including the predominant anaerobic floras, changed little. No overgrowth of Pseudomonas aeruginosa, staphylococci, fungi, or highly erythromycin-resistant strains of the family Enterobacteriaceae was observed. The strains of Enterobacteriaceae and of anaerobes isolated during treatment were not markedly more resistant to roxithromycin than those isolated before treatment started. Changes in intestinal resistance to colonization by exogenous microorganisms in gnotobiotic mice inoculated with human fecal flora were studied and were also found to be minimal. The impact of oral roxithromycin on the intestinal microbiota appears to be weaker than that previously observed with oral erythromycin, perhaps because the concentrations of roxithromycin in the feces were lower than those previously found for erythromycin.
MATERIALS AND METHODS Human volunteers. Six healthy, fully informed adult volunteers, ages 25 to 42 years, were included in the study. None had taken antibiotics for at least 1 month before the study. Oral roxithromycin was administered twice daily for 5 days in doses of 150 mg. Blood samples were drawn 2 h after the morning dose on the first and last days of treatment. Freshly passed fecal samples were obtained once before treatment, daily during treatment, and 1 week thereafter. Gnotobiotic mice. Adult germ-free C3H mice (Centre de Selection des Animaux de Laboratoire, Orleans, France) were kept in plastic Trexler-type isolators. They were fed a locally prepared diet (4) sterilized by gamma irradiation and either supplemented with 10 g of roxithromycin per kg of diet or left without roxithromycin. Autoclaved drinking water at pH 3 was given ad libitum. Some of the mice used were in the germ-free state. The remainder were each given a complex human fecal flora by intragastric and intrarectal inoculation of a dilution of the original flora, as previously described (4). The human donor was chosen from among the volunteers. Germ-free and human-flora-associated (HFA) mice were each divided into two groups. One germ-free and one HFA group were left untreated, and one group of each type was treated with roxithromycin; for the treated HFA group, 2 weeks was allowed to elapse between the introduction of the fecal flora and the beginning of roxithromycin administration. Both treated and untreated mice were challenged with various strains 2 weeks after roxithromycin administration was started with the treated groups. The challenge was performed, as previously described, by intragastric inoculation of 1 ml of a culture containing 108 CFU of one of the challenge strains per ml (4). Challenge strains. Escherichia coli H10407, Shigella flexneri 115DKR, Vibrio cholerae 569B, Salmonella typhimurium IGR9, and Campylobacter jejuni IGR6 were isolated from diarrheal patients. Pseudomonas aeruginosa IGR54, Staphylococcus aureus IGR53, and Candida albicans IGR41 were from our laboratory collection. The MICs of erythro-
Macrolide antibiotics have been used for many years because they are highly effective agents against gram-positive pathogenic bacteria. Recently, however, it was shown that oral treatment with erythromycin base, the reference drug of the macrolide class of antibiotics, was followed by a sharp decrease in the concentrations of intestinal aerobic gram-negative bacteria (6). This paradoxical effect of erythromycin was due to its accumulation in the colon, resulting in concentrations higher than those required to inhibit members of the family Enterobacteriaceae in vitro (6). Otherwise, erythromycin did little to alter either the composition of the fecal flora or the resistance to colonization by exogenous microorganisms (4). During treatment with erythromycin, a noticeable shift toward resistance in surviving bacteria was observed (4), but colonization with highly erythromycin-resistant (HER) strains of Enterobacteriaceae, i.e., strains for which the MIC was greater than 512 Vig/ml, was rare (5). Therefore, oral treatment with erythromycin is potentially useful for selective intestinal tract decontamination, a technique which has been proposed both for prophylaxis of infection in patients who have hematological malignancies or who are undergoing mechanical ventilation (10) and for the prevention of traveler's diarrhea (6, 15). Roxithromycin is a newly introduced macrolide antibiotic which differs from erythromycin in its chemical composition (14) and which exhibits greater intestinal absorption and bioavailability than erythromycin (11). Its recommended daily dosage is lower than that of erythromycin (5 versus 30 to 50 mg/kg of body weight per day). It was not known whether this lower dosage implied that roxithromycin had a weaker impact than erythromycin on the intestinal flora and on colonization resistance, and the present study was designed to elucidate this question.
* Corresponding author. 548
ROXITHROMYCIN AND INTESTINAL FLORA
VOL. 35, 1991
549
TABLE 1. Fecal counts of challenge strains in gnotobiotic mice and MICs of roxithromycin and erythromycin Fecal counts' for:
MIC (,ug/ml)
HFA mice' Monoassociated mice' StrainbHFmie During Before During Before Roxithromycin Erythromycin treatment treatment treatmentd treatment
E. coli H10407 S.flexneri 115DKR
S. typhimurium IGR9 P. aeruginosa IGR54 S. aureus IGR53 V. cholerae 569B C. jejuni IGR6 C. albicans IGR41
32 64 64 64 16 0.05 0.03 >1,024
128 512
128 64 64 0.05 0.03 >1,024
NDe
10.4 t 0.4 9.6 t 0.2
6.4 t 2.0 6.6 t 1.0
8.3 t 0.3
LEf
ND 8.0 t 1.4 9.2 t 1.1
