Comparison of E test and Disk Diffusion Test for Antibiotic Resistance Testing of Enterotoxigenic and Non- Enterotoxigenic Bacteroides fragilis Isolated From Stools

Abstract

Background: Enterotoxigenic Bacteroides fragilis (ETBF) are one of the most important anaerobic bacteria whichcause diarrhea in human beings. A bft gene is coded for enterotoxin production called fragilysin. Most of them have acquired resistance to antianaerobicbacteria agent like other facultative anaerobic bacteria. E test and different dilution methods are usually performed for antimicrobial susceptibility determination of B. fragilis.Objectives: The aims of this study are to recognize ETBF by PCR method and also to evaluate efficiency thedisk diffusion method (DDM) in comparison with the E tests for antimicrobial susceptibility of B. fragilis isolates.Materials and Methods: bft gene was detected among 157 B. fragilis isolated from patients and healthy individuals by PCR. Antimicrobial susceptibility of all isolates was determined by DDM and E tests methods.Results: Nineteen (12.1%) B. fragilis containing bft gene from diarrheic (n = 14) and nondiarrheic (n = 5) feces were detected among 157 B. fragilis isolates. The highest resistance for ciprofloxacin, cefotaxim, cefoxitin with DDM and E test were 100%, 60%, and 65% respectively, while the lowest resistance in two methods was obtained for imipenem, piperacillin / tazobactam, and metronidazol. 100% agreement for some of antibiotics such as imipenem (P ≤ 0.05), and no correlation for others were observed among the antimicrobial susceptibility results obtained by the two methods (P ≥ 0.05).Conclusions: The presence of bft gene in B. fragilis isolates wouldnot certainly result in diarrheaamong patients. There is not enough accordance between DDM and Swedish E tests for antimicrobial susceptibility of B. fragilis for some antibiotics, although in other cases a good agreement was observed

Antimicrobial resistance, prevalence of resistance genes, and molecular characterization in intestinal Bacteroides fragilis group isolates

“…The previous studies regarding the incidence and characterization of ETBF or NETBF, and their drug susceptibility patterns have provided the distribution statistics and involvement in diseases (5,(8)(9)(10). In Iran, rare studies have been done to detect B. fragilis strains in hospitalized patients (11)(12)(13)(14). In the current study, we evaluated the antimicrobial resistance, prevalence of resistance genes, and molecular characterization of intestinal BFG isolates in hospitalized patients among three hospitals, Firouzabadi, Firouzgar, and Rasoul Akram, Tehran, Iran.…”

Role of Enterotoxigenic Bacteroides fragilis in Children Less Than 5 Years of Age With Diarrhea in Tabriz, Iran

“…Bacteroides fragilis usually constitutes 1% to 2% of the normal human gastrointestinal microbial flora ( 23 ). This important opportunistic obligate anaerobic pathogen commonly causes human extra-intestinal polymicrobial infections ( 17 ).…”

“…This important opportunistic obligate anaerobic pathogen commonly causes human extra-intestinal polymicrobial infections ( 17 ). Recently, the association of B. fragilis as etiological pathogen of gastrointestinal disease has been highlighted by some researchers ( 23 ). This opportunistic pathogen causes diarrheal disease via production of zinc metalloprotease enterotoxin ( 11 ).…”

“…Although some studies show that regardless of being diarrheal disease, one may be an ETBF carrier ( 23 ), Sack et al reported 4% ETBF as an important etiologic agent in acute diarrhea in children older than 1 year in a controlled study ( 9 ).…”

“…Due to the decrease in sensitivity to antibiotics among anaerobic bacteria, selection of antibiotic drugs for treatment of infections caused by these bacteria has been difficult ( 23 ). Metronidazole has been the drug of choice for the treatment of infection caused by anaerobic bacteria worldwide for nearly 40 years but the recent emergence of metronidazole resistance is a matter of great concern ( 17 ).…”