Antimicrobial resistance in human oral and intestinal anaerobic microfloras

Abstract

In the present study we determined the resistance patterns of anaerobic bacteria from human saliva and stool specimens and investigated whether there were significant differences in resistance between outpatients and hospitalized patients, regardless of whether they had received antimicrobial agents. No bacterial strains resistant to ampicillin, piperacillin, cefoxitin, cefuroxime, imipenem, clindamycin, doxycycline, chloramphenicol, or metronidazole were isolated from the saliva samples. However, resistance to ampicillin, cefoxitin, and cefuroxime was found in strains from 70%o of the fecal samples (mainly Bacteroides thetaiotaomicron, Clostridium innocuum, and Bacteroides ovatus). Resistance to both ampicillin and cefuroxime was frequently found in 19%o of the isolated strains (mainly B. thetaiotaomicron, B. ovatus, and Bacteroides vulgatus). No strains that were resistant to imipenem, chloramphenicol, or metronidazole were found. Hospitalization and/or intake of antimicrobial agents was associated with an increase in the relative number of resistant anaerobic intestinal bacteria. The percentage of resistant anaerobic strains encountered, compared with the total number of anaerobic bacteria in the normal fecal microflora, was between 5.2 and 14.8%, with the lower value associated with the outpatient group. Two-thirds of the resistant strains from this group had a relative frequency of less than 1% of the total anaerobic flora, while one-third of the strains were present at a level of greater than 1%; for the hospitalized patients, two-thirds of the strains were present at a level of greater than 1%, and one-third of the strains were present at a level of less than 1% (P < 0.001). Patients who had received antimicrobial agents for 6 days or more (n = 20) had an average of 1.6 resistant anaerobic strains each, while patients treated for 3 to 5 days (n = 30) had a mean number of 0.87 resistant strains each (P < 0.05).

Orally Administered Targeted Recombinant Beta-Lactamase Prevents Ampicillin-Induced Selective Pressure on the Gut Microbiota: a Novel Approach to Reducing Antimicrobial Resistance

“…The data are consistent with those from previous studies that demonstrate that ampicillin treatment may have a marked effect on the intestinal microbiota (15,20,23,25) and that the population of antimicrobial-resistant pathogens may expand within days after the onset of antibiotic therapy (9). Thirtythree percent of the dogs used in this study carried ampicillinresistant E. coli at low but detectable levels at the baseline.…”

“…Previous studies have demonstrated that the normal intestinal microbiota contains various degrees of antibiotic resistance genes (1,8,17,22) and that healthy individuals may harbor intestinal bacteria that can produce TEM ␤-lactamases (19,21,23). It has further been shown that the resistance patterns of enteric bacteria change in response to increased levels of exposure to antibiotics (9) and that selective pressure from ampicillin treatment can result in increased levels of ampicillin-resistant bacteria (7).…”

“…Antimicrobials that are excreted into the intestinal tract may cause profound disruption of the indigenous microbiota (18,20,23,25), resulting in a number of adverse effects such as antibioticassociated diarrhea and Clostridium difficile colitis (20). In addition, the selective pressure exerted by antimicrobials in the intestinal tract contributes to the acquisition and overgrowth of antimicrobial-resistant pathogens, including vancomycin-resistant enterococci (VRE), Candida species, and multiresistant gram-negative bacilli (28).…”

Activities of Garenoxacin (BMS-284756) and Other Agents against Anaerobic Clinical Isolates

“…Piperacillin-tazobactam, imipenem, and the quinolones showed good activity against most species, as has been noted in other studies (6,12,15,21,25). Reduced activity to all of these agents was only found among isolates of B. vulgatus and B. thetaiotaomicron species.…”

“…A number of Prevotella species associated with periodontal disease have been found to be beta-lactamase positive (10). In a study of fecal anaerobic strains, resistance to ampicillin, cefoxitin, or cefuroxime was found in 70% of strains, with 19% showing multiple resistance to both ampicillin and cefuroxime (25). Resistance to clindamycin is also increasing (6), and as many as 20 to 40% of Bacteroides fragilis strains are clindamycin resistant (2,14).…”