Induction of Multidrug Resistance Mechanism inEscherichia coliBiofilms by Interplay between Tetracycline and Ampicillin Resistance Genes

Abstract

Biofilms gain resistance to various antimicrobial agents, and the presence of antibiotic resistance genes is thought to contribute to a biofilm-mediated antibiotic resistance. Here we showed the interplay between the tetracycline resistance efflux pump TetA(C) and the ampicillin resistance gene (bla TEM-1 ) in biofilms of Escherichia coli harboring pBR322 in the presence of the mixture of ampicillin and tetracycline. E. coli in the biofilms could obtain the high-level resistance to ampicillin, tetracycline, penicillin, erythromycin, and chloramphenicol during biofilm development and maturation as a result of the interplay between the marker genes on the plasmids, the increase of plasmid copy number, and consequently the induction of the efflux systems on the bacterial chromosome, especially the EmrY/K and EvgA/S pumps. In addition, we characterized the overexpression of the TetA(C) pump that contributed to osmotic stress response and was involved in the induction of capsular colanic acid production, promoting formation of mature biofilms. However, this investigated phenomenon was highly dependent on the addition of the subinhibitory concentrations of antibiotic mixture, and the biofilm resistance behavior was limited to aminoglycoside antibiotics. Thus, marker genes on plasmids played an important role in both resistance of biofilm cells to antibiotics and in formation of mature biofilms, as they could trigger specific chromosomal resistance mechanisms to confer a high-level resistance during biofilm formation.

Nitrate-Dependent Ferrous Iron Oxidation by Anaerobic Ammonium Oxidation (Anammox) Bacteria

“…Scanning electron microscopy (SEM) was performed as previously described (39). Rusty precipitates were washed two times with PBS and fixed with 2.5% glutaraldehyde in PBS overnight at 4°C.…”

The Challenge of Efflux-Mediated Antibiotic Resistance in Gram-Negative Bacteria

“…In E. coli, these pumps include EmrB (occurring with the cognate adaptor EmrA) and EmrY (with EmrK), which indeed appear to be involved in the efflux of uncouplers and other substrates (Table 1) (15,31,139,140). Importantly, the crystallographic structure of EmrD was determined (141).…”

“…The survival of these active subpopulations after exposure to membrane-targeting agents (colistin and chlorhexidine) is also linked to not only MexAB-OprM but also MexCD-OprJ and MuxABC-OpmB pumps (477). In E. coli, the plasmid-borne TetA pump and TEM-1 ␤-lactamase interplay in the presence of subinhibitory levels of antibiotics to induce biofilm resistance to multiple antibiotics, and this is partly due to the induction of the chromosomal pump EmrKY and its regulator EvgAS (140). However, several early studies were unable to establish an additional contribution of AcrAB or MexABOprM to biofilm resistance to ciprofloxacin (16).…”

Exposure of conjugative plasmid carrying Escherichia coli biofilms to male-specific bacteriophages

“…However, to observe the effect of bacteriophage infection during the biofilm maturation stage, the bacteriophage(s) was added to 24-h-old-biofilms (the cell density was approximately 10 8 colony forming units per cm 3 ) at 0, 10 7 , 10 8 , 10 9 and 10 10 PFU ml À1 , corresponding to MOI of 0, 0.1, 1, 10 and 100, respectively. The plates were then incubated for another 24 h before recording the optical density at 600 nm and processing the crystal violet-based biofilm formation assay as previously described (May et al, 2009). Results showed that the bacteriophage infection dramatically inhibited the early biofilm formation by E. coli carrying a natural F-plasmid (Figure 1a), but they failed to attack the 24-h-old mature biofilms ( Figure 1b).…”