Impact of injectable cephalosporins on the gastrointestinal microflora: observations in healthy volunteers and hospitalized patients.

A disturbed microbiological ecosystem of the gut flora is frequently seen as a consequence of antibiotic therapy. Because this impact on the physiological balance is known to be causative for severe nosocomial infections and is mainly seen with antibiotics that are massively excreted via the bile (e.g. broadspectrum penicillins, ceftriaxone and cefoperazone), we investigated cefotaxime (CTX), cefotiam (CTM), cefmenoxime (CMX), ceftazidime (CAZ), ceftizoxime (CZX) and cefazolin + netilmicin (CEZ + NTL) in healthy volunteers. The respective daily i.v. doses, days of medication and numbers of volunteers were: CTX 3 g, 1 d, n = 8; CTM 6 g, 3 d, n = 15; CMX 4 g, 3 d, n = 15; CAZ 4 g, 1 d, n = 8; CZX 4 g, 1 d, n = 8; CEZ + NTL 2 X 3 g + 1 X 3 mg/kg/day, 4 d, n = 15. CTX was also investigated in 11 selected hospitalized patients. One or two stool specimens were taken before, during and several days after medication. The microorganisms were also tested for ampicillin and CEZ resistance on selective media. Ampicillin and CEZ resistance was much higher in hospitalized patients than in volunteers (mainly Proteus and Serratia sp.): 90% vs. 42% and 63.6% vs. 43%, respectively. CTX did not affect the anaerobes (Bacteroides sp. and lactobacilli) that are antagonistic to clostridia and Candida. No selection of strains resistant to ampicillin or CEZ occurred. In hospitalized patients, the level of resistance to these drugs was lower after treatment than before.(ABSTRACT TRUNCATED AT 250 WORDS)