Characteristics of Bacteroides fragilis lacking the major outer membrane protein, OmpA.

OmpA1 is the major outer membrane protein of the Gram-negative anaerobic pathogen Bacteroides fragilis. We identified three additional conserved ompA homologues (ompA2-ompA4) and three less homologous ompA-like genes (ompAs 5, 6 and 7) in B. fragilis.

Presence of quorum-sensing systems associated with multidrug resistance and biofilm formation in Bacteroides fragilis.

Bacteroides fragilis constitutes 1-2% of the natural microbiota of the human digestive tract and is the predominant anaerobic opportunistic pathogen in gastrointestinal infections. Most bacteria use quorum sensing (QS) to monitor cell density in relation to other cells and their environment. In Gram-negative bacteria, the LuxRI system is common.

Induction of multiple antibiotic resistance in Bacteroides fragilis by benzene and benzene-derived active compounds of commonly used analgesics, antiseptics and cleaning agents.

Objectives: To determine the potential of active compounds (ACs) present in commonly used analgesics/antiseptics and cleaning agents (detergents and disinfectants) to induce multiple antibiotic resistance (MAR) in Bacteroides fragilis.

Methods: B. fragilis ATCC 25285 untreated or pretreated with sublethal concentrations of ACs (n = 25) was grown for 12 h.

Impact of anatomic site on growth, efflux-pump expression, cell structure, and stress responsiveness of Bacteroides fragilis.

This study investigated whether B. fragilis from various human sites acquired stable traits enabling it to express certain efflux pumps (EPs), adopt a particular cell structure, and tolerate certain stressors. Isolates from blood, abscess, and stool (n = 11 each) were investigated.

BmeRABC5 is a multidrug efflux system that can confer metronidazole resistance in Bacteroides fragilis.

The RND-family efflux pump gene bmeB5 was previously shown to be overexpressed in metronidazole-resistant laboratory mutants of Bacteroides fragilis. In the present study, we characterized the bmeABC5 genes and an upstream putative TetR-family regulator gene (bmeR5). bmeR5 (645 bp) was located 51 bp upstream of bmeA5 and encoded a 24.

Bile salts enhance bacterial co-aggregation, bacterial-intestinal epithelial cell adhesion, biofilm formation and antimicrobial resistance of Bacteroides fragilis.

Bacteroides fragilis is the most common anaerobic bacterium isolated from human intestinal tract infections. Before B. fragilis interacts with the intestinal epithelial cells, it is exposed to bile salts at physiological concentrations of 0.

The Bacteroides fragilis cell envelope: quarterback, linebacker, coach-or all three?

Bacteroides fragilis is an anaerobic commensal constituting only 1-2% of the micro-flora of the human gastrointestinal tract, yet it is the predominant anaerobic isolate in cases of intraabdominal sepsis and bacteremia. B. fragilis can play two roles in the host: in its role as friendly commensal, it must be able to establish itself in the host intestinal mucosa, to utilize and process polysaccharides for use by the host, and to resist the noxious effects of bile salts.

Efflux pump overexpression in multiple-antibiotic-resistant mutants of Bacteroides fragilis.

Multidrug-resistant mutants of a wild-type Bacteroides fragilis strain (strain ADB77) and a quadruple resistance nodulation division family efflux pump deletion mutant (ADB77 Delta bmeB1 Delta bmeB3 Delta bmeB12 Delta bmeB15) were selected with antimicrobials. Ampicillin, doripenem, imipenem, levofloxacin, and metronidazole selected for mutants from both strains; cefoxitin selected for mutants from strain ADB77 only; and sodium dodecyl sulfate selected mutants from ADB77Delta bmeB1 Delta bmeB3 Delta bmeB12 Delta bmeB15 only. The mutants overexpressed one or more efflux pumps.

Clinical significance of overexpression of multiple RND-family efflux pumps in Bacteroides fragilis isolates.

Objectives: The aim of the present study was to determine correlation between bmeB efflux pump overexpression and resistance to fluoroquinolones and beta-lactams in Bacteroides fragilis clinical isolates (n = 51) and the effects of broad-spectrum efflux pump inhibitors (EPIs) on the MICs of the test antibiotics.

Methods: Susceptibility to garenoxacin, levofloxacin, moxifloxacin, cefoxitin and faropenem +/- EPIs (CCCP, MC-207,110, reserpine and verapamil) was determined. Expression of bmeB efflux pumps was measured, topoisomerase genes were sequenced and beta-lactamase production was determined.

Bacteroides fragilis BmeABC efflux systems additively confer intrinsic antimicrobial resistance.

Objectives: To determine the prevalence of expression and function(s) of Bacteroides fragilis RND family efflux transport systems (bmeABC1-16).

Methods: The mRNA transcripts of bmeB efflux pump genes were detected in a wild-type strain ADB77 by RT-PCR and expression in different strains was quantified by comparative quantitative real-time RT-PCR. In order to determine independent or additive functions, BmeB 1, 3, 12 and 15 (the first efflux pumps identified) were deleted as singles, doubles, triples or quadruples by the double cross-over technique with pADB242 and antimicrobial susceptibility was assayed by the spiral gradient endpoint technique.

Evidence for multiple-antibiotic resistance in Campylobacter jejuni not mediated by CmeB or CmeF.

An efflux system, CmeABC, in Campylobacter jejuni was previously described, and a second efflux system, CmeDEF, has now been identified. The substrates of CmeDEF include ampicillin, ethidium bromide, acridine, sodium dodecyl sulfate (SDS), deoxycholate, triclosan, and cetrimide, but not ciprofloxacin or erythromycin. C.

Expression of the efflux pump genes cmeB, cmeF and the porin gene porA in multiple-antibiotic-resistant Campylobacter jejuni.

Aims: In Escherichia coli, increased expression of efflux pumps and/or decreased expression of porins can confer multiple antibiotic resistance (MAR), causing resistance to at least three unrelated classes of antibiotics, detergents and dyes. It was hypothesized that in Campylobacter jejuni, the efflux systems CmeABC, CmeDEF and the major outer membrane porin protein, MOMP (encoded by porA) could confer MAR.

Methods: The expression of cmeB, cmeF and porA in 32 MAR C.

Fluoroquinolone resistance in Campylobacter species from man and animals: detection of mutations in topoisomerase genes.

Consecutive isolates of quinolone-resistant campylobacter isolated over a 5 year period (1990-1995) from the faeces of patients with enteritis in Plymouth, UK, were examined for the epidemiology of mutations in gyrA (n = 127). In addition, clinical isolates and poultry isolates from Germany, The Netherlands and other regions of the UK collected before 1995 were examined for mutations in the quinolone resistance-determining region of gyrA by single-stranded conformational polymorphism analysis and direct sequencing of a 270 bp fragment of PCR-generated DNA. The majority of isolates (173/208) carried a mutation at codon 86 in gyrA resulting in substitution of Ile for Thr; all of these were resistant to ciprofloxacin (MIC > or = 2 mg/L).

Identification and molecular characterisation of CmeB, a Campylobacter jejuni multidrug efflux pump.

A multidrug efflux pump gene (cmeB) was identified from the published Campylobacter jejuni genome sequence. Secondary structural analysis showed that the gene encoded a protein belonging to the resistance nodulation cell division (RND) family of efflux transporters. The gene was inactivated by insertional mutagenesis.