[Selective action of broad-spectrum antibiotics on intestinal flora in sepsis in rats].

OBJECTIVE: To investigate the selective effect of broad-spectrum antibiotics on the intestinal flora in sepsis in rats. METHODS: Fifty-six SD rats were randomly divided into normal control group, scald group [before ceftriaxone sodium (rocephin) treatment group], scald group with 3 days of rocephin treatment, scald group with 9 days of rocephin treatment, and sepsis group (before rocephin treatment group), sepsis group with 3 days of rocephin treatment, and sepsis group with 9 days of rocephin treatment. All the animals were incurred with 30% III degree burns on their back followed by endotoxin challenge with a dose of 20 mg/kg 24 hours after the burn injury. The animals were treated with intraperitoneal injection of ceftriaxone 24 hours (60 mg/kg, quaque 12 hours) after the second hit with endotoxin. At the end of the treatment, the bacteria in stomach, intestine and colon were cultured. The number and kind of the bacteria were also determined. RESULTS: Antibiotics significantly increased the number of cocci (P<0.05 or P<0.01). The ratio between cocci and bacilli was markedly inverted. In selective culture of gut bacilli, E.Coli was almost the only bacteria in the contents of stomach, intestine and colon in normal control group, but after burns and endotoxin challenge, Klebsiella pneumoniae, Proteus mirabilis appeared. After the rats received antibiotics treatment, E. coli decreased in number or disappeared, and was replaced mainly by Pseudomonas aeruginosa, Klebsiella pneumoniae, Acinetobacter baumannii, Enterobacter cloacae and Proteus and other bacilli. CONCLUSION: Broad-spectrum antibiotics can induce imbalance of bacteria flora in the gut, resulting in a reversion of the ratio between cocci and bacilli, and also reduction in intestinal colonization resistance. Then, opportunistic pathogens become dominant flora in gut, which may cause antibiotic-related gut-origin diseases.