Emergence and spread of two distinct clonal groups of multidrug-resistant Escherichia coli in a veterinary teaching hospital in Australia.

Multidrug-resistant Escherichia coli (MDREC) expressing AmpC beta-lactamases have emerged as a cause of opportunistic infections in dogs. Following a cluster of extraintestinal infections caused by two distinct clonal groups (CGs) of bla(CMY)-producing MDREC, a 12-month infection control study was undertaken at a veterinary teaching hospital in Brisbane, Australia. Swabs from the rectum of hospitalized dogs (n=780), hospital staff (n=16) and the hospital environment (n=220) were plated onto selective agar to obtain multidrug-resistant (MDR) coliforms. These were then tested by multiplex PCR for E. coli uspA, bla(CMY) and the class 1 integron-associated dfrA17-aadA5 gene cassette for rapid identification of MDREC CG 1 (positive for all three genes) and CG 2 (positive for uspA and bla(CMY) only). A total of 16.5 % of the dog rectal swabs and 4.1% of the hospital environmental swabs yielded MDREC, and on the basis of multiplex PCR, PFGE and plasmid profiling, these were confirmed to belong to either CG 1 or CG 2. Both CG 1 and CG 2 isolates were obtained from clinical cases of extraintestinal infection and rectal swabs from hospitalized dogs over the same period of time, whereas only CG 1 isolates were obtained from the hospital environment. Both CGs were prevalent during the first 6 months, but only CG 2 was isolated during the second 6 months of the study. Two isolates obtained from rectal swabs of staff working in the hospital belonged to CG 2, with one of the isolates possessing the same REDP as nine isolates from dogs, including six isolates associated with cases of extraintestinal infection. CG 1 isolates belonged to E. coli serotypes O162 : H-, OR : H- or Ont : H-, whereas CG 2 isolates belonged to O153 : HR, OR : HR or OR : H34. These results confirm that in this particular outbreak, canine MDREC were highly clonal and CG 2 MDREC may colonize both humans and dogs.

Tailoring surface properties to build colloidal diagnostic devices: controlling interparticle associations.

The ability to control the surface properties and subsequent colloidal stability of dispersed particles has widespread applicability in many fields. Sub-micrometer fluorescent silica particles (reporters) can be used to actively encode the combinatorial synthesis of peptide libraries through interparticle association. To achieve these associations, the surface chemistry of the small fluorescent silica reporters is tailored to encourage robust adhesion to large silica microparticles onto which the peptides are synthesized. The interparticle association must withstand a harsh solvent environment, multiple synthetic and washing procedures, and biological screening buffers. The encoded support beads were exposed to different solvents used for peptide synthesis, and different solutions used for biological screening including phosphate buffered saline (PBS), 2-[N-morpholino]ethane sulfonic acid (MES) and a mixture of MES and N-(3-dimethyl-aminopropyl)-N'-ethylcarbodiimide (EDC). The number of reporters remaining adhered to the support bead was quantified after each step. The nature of the associations were explored and tested to optimize the efficiency of these phenomena. Results presented illustrate the influence of the surface functionality and polyelectrolyte modification of the reporters. These parameters were investigated through zeta potential and X-ray photoelectron spectroscopy.