Effect of aztreonam on the colon microflora in patients undergoing colorectal surgery

Carriage of antibiotic resistant bacteria flora and its role in the guidance of clinical decision making

There is considerable literature on the threat of antibiotic resistance and its impact on morbidity. However, an under-studied consideration is how carriage of these antibiotic resistant bacteria persist in an individual. The duration that a person harbors a resistant organism is critical in guiding future antimicrobial therapy. Key unexplored questions are the rate of clearance of these organisms and what drives their persistence. This paper attempts to examine these questions and offers some initial answers as well as avenues for further study.

Effect of antibiotic treatment on growth of and toxin production by Clostridium difficile in the cecal contents of mice

In mice, subcutaneous administration of antibiotics that disrupt the anaerobic microflora (i.e., clindamycin, piperacillin-tazobactam, and ceftriaxone) facilitated in vitro growth of and toxin production by Clostridium difficile in cecal contents, whereas antibiotics that cause minimal disruption of the anaerobic microflora (i.e., levofloxacin, cefepime, and aztreonam) did not.

Prospective evaluation of effects of broad-spectrum antibiotics on gastrointestinal yeast colonization of humans

This study evaluated the effects of broad-spectrum antibiotics on the gastrointestinal (G.I.) yeast flora of humans and correlated the findings with those obtained from a mouse model of G.I. colonization by Candida albicans. We prospectively studied 46 adult cancer patients who received one of five broad-spectrum antibiotics (ceftriaxone, ceftazidime, ticarcillin-clavulanic acid, imipenem-cilastatin, and aztreonam) as therapy for infections. Quantitative examination of yeast colonization of stools was conducted at the baseline, at the end of antibiotic treatment, and 1 week after discontinuation of therapy. Antibiotics with anaerobic activity (ticarcillin-clavulanic acid) or high G.I. concentrations (ceftriaxone) caused a higher and more sustained increase in G.I. colonization by yeasts than did antibiotics with poor anaerobic activity (ceftazidime and aztreonam) or a low G.I. concentration (imipenem-cilastatin). These results were similar to those obtained with a mouse model of G.I. colonization by C. albicans that involved the same antibiotics. Hence, the mouse model may be useful for evaluation of yeast colonization of the human G.I. tract.

Modulation of the intestinal flora of mice by treatment with aztreonam and tigemonam

Oral and parenteral administration of aztreonam and oral administration of tigemonam to conventional mice caused a decrease in the number of aerobic gram-negative rods in the feces. Oral treatment with high doses of aztreonam (greater than or equal to 25 mg/kg/day) and tigemonam (100 mg/kg/day) adversely influenced colonization resistance, whereas oral treatment with lower doses of the monobactams or parenteral treatment with aztreonam did not.

Effects of broad-spectrum antimicrobial agents on yeast colonization of the gastrointestinal tracts of mice

Male Crl:CD1 (ICR) BR mice, 3 months old, were fed regular chow or chow containing Candida albicans. Subsequently, both groups were treated with either antibiotics or normal saline for 10 days. Stool cultures were obtained to determine the extent of C. albicans colonization immediately before treatment, at the end of treatment, and 1 week after the discontinuation of treatment. Animals in the antibiotic-treated groups had substantially higher Candida counts than control animals fed C. albicans, especially if they received ceftriaxone, cefoperazone, or ticarcillin-clavulanic acid. There was no evidence of Candida dissemination to internal organs.

Impact of antimicrobial agents on human intestinal microflora

The most common and significant cause of disturbances in the normal intestinal microflora is the administration of antimicrobial agents. The microflora can be influenced by antimicrobial agents because of incomplete absorption of any orally administered antimicrobial agent, secretion of an antimicrobial agent in the bile, or secretion from the intestinal mucosa. In most cases, the influence is not beneficial to the patient because suppression of the indigenous microorganisms often permits potential pathogens to overgrow and cause septic conditions, stomatitis, diarrhea, or colitis. Antimicrobial agents that influence the normal microflora also promote the emergence of antimicrobial-resistant strains. During the last fifteen years, the impact of different antimicrobial agents on the human microflora has been studied by several investigators. In this article published data on the impact of beta-lactam antibiotics, macrolides, tetracyclines, nitroimidazoles, clindamycin and quinolones on the human intestinal microflora are reviewed.

Effect of broad-spectrum parenteral antibiotics on composition of intestinal microflora of humans

We compared the effects of four beta-lactam drugs with widely differing antibacterial and pharmacological properties on the composition of the intestinal flora. Cefoxitin, piperacillin, cefoperazone, and aztreonam were given intravenously for 9 days to healthy volunteers. Cefoperazone reduced the numbers of aerobic and anaerobic bacteria to undetectable levels. At the other extreme, cefoxitin had little effect on the normal flora. Aztreonam markedly reduced the numbers of aerobes, whereas piperacillin had a variable effect on both aerobic and anaerobic bacteria. There was extensive overgrowth of enterococci in subjects given cefoxitin or aztreonam, which have little activity against this species, and of yeasts in subjects given cefoperazone or piperacillin. Cefoperazone reached concentrations of 2,727 to 8,840 micrograms/g in the feces, whereas the other agents were generally undetectable. These results show that the new beta-lactam antibiotics produce widely varying effects on the fecal microflora after parenteral administration and that these effects are consistent with the antibacterial and pharmacological properties of the drugs.

Alterations in the human oropharyngeal microflora related to therapy with aztreonam, moxalactam and ampicillin plus sulbactam

33 patients undergoing colorectal surgery were treated prophylactically with aztreonam (19 patients), moxalactam (10 patients) and ampicillin plus sulbactam (4 patients). The effect on the normal oropharyngeal microflora and new colonization of oropharynx were studied during and after the treatment. Aztreonam had minor effect on the normal flora but induced colonization with staphylococci. Moxalactam suppressed gram-negative aerobic and anaerobic bacteria and promoted colonization with Candida albicans. Ampicillin plus sulbactam had marked effect on the normal flora and suppressed aerobic as well as anaerobic bacteria. New colonization with enteric gram-negative rods or fungi was observed in all patients.