A general method for rapid determination of antibiotic susceptibility and species in bacterial infections.

To ensure correct antibiotic treatment and reduce the unnecessary use of antibiotics, there is an urgent need for new rapid methods for species identification and determination of antibiotic susceptibility in infectious pathogenic bacteria. We have developed a general method for the rapid identification of the bacterial species causing an infection and the determination of their antibiotic susceptibility profiles. An initial short cultivation step in the absence and presence of different antibiotics was combined with sensitive species-specific padlock probe detection of the bacterial target DNA to allow a determination of growth (i.

Selection of a multidrug resistance plasmid by sublethal levels of antibiotics and heavy metals.

How sublethal levels of antibiotics and heavy metals select for clinically important multidrug resistance plasmids is largely unknown. Carriage of plasmids generally confers substantial fitness costs, implying that for the plasmid-carrying bacteria to be maintained in the population, the plasmid cost needs to be balanced by a selective pressure conferred by, for example, antibiotics or heavy metals. We studied the effects of low levels of antibiotics and heavy metals on the selective maintenance of a 220-kbp extended-spectrum β-lactamase (ESBL) plasmid identified in a hospital outbreak of Klebsiella pneumoniae and Escherichia coli.

Selection of resistant bacteria at very low antibiotic concentrations.

The widespread use of antibiotics is selecting for a variety of resistance mechanisms that seriously challenge our ability to treat bacterial infections. Resistant bacteria can be selected at the high concentrations of antibiotics used therapeutically, but what role the much lower antibiotic concentrations present in many environments plays in selection remains largely unclear. Here we show using highly sensitive competition experiments that selection of resistant bacteria occurs at extremely low antibiotic concentrations.

Activation of cryptic aminoglycoside resistance in Salmonella enterica.

Aminoglycoside resistance in bacteria can be acquired by several mechanisms, including drug modification, target alteration, reduced uptake and increased efflux. Here we demonstrate that increased resistance to the aminoglycosides streptomycin and spectinomycin in Salmonella enterica can be conferred by increased expression of an aminoglycoside adenyl transferase encoded by the cryptic, chromosomally located aadA gene. During growth in rich medium the wild-type strain was susceptible but mutations that impaired electron transport and conferred a small colony variant (SCV) phenotype or growth in glucose/glycerol minimal media resulted in activation of the aadA gene and aminoglycoside resistance.