Background: It is well documented that antibiotic therapy exerts selective pressure on bacteria. Conversion of bacteria from susceptible to resistant to antibiotics has been observed often during antimicrobial therapy. It has been postulated that human intestinal reservoirs facilitate communication of transposons that can transfer resistance determinants among various bacterial species.
Methods: This study examined the susceptibilities of organisms isolated from infected abdomens to a number of antibiotic agents during a 12-year time interval. Analysis included 1102 isolates recovered from 255 specimens, representing the following genera: Bacteroides, Clostridium, Gemella, Fusobacterium, Peptostreptococcus, Porphyromonas, Prevotella, Enterococcus, Staphylococcus, Streptococcus, Pseudomonas, and Enterobacteriaceae. Strains were tested against beta-lactam agents, beta-lactams in combination with beta-lactamase inhibitors, first, second, and third generation cephalosporins, aminoglycosides, clindamycin, metronidazole, chloramphenicol, and imipenem.
Results: The results indicated that during a time period of more than a decade essentially no change occurred in the antibiotic susceptible fraction of all species tested.
Conclusions: Abdominal sepsis is caused by leakage of endogenous intestinal flora. This study suggests that the intestinal flora is not permanently affected by short-term antibiotic therapy and that older antibiotics are appropriate first-line therapeutic agents for community-acquired infections caused by normal intestinal flora.