Antibacterial activity of silver nanoparticles against Escherichia coli and methicillin-resistant Staphylococcus pseudintermedius is affected by incorporation into carriers for sustained release.

OBJECTIVE: To establish the lowest effective dose of commercially available nanoparticulate silver (AgNP) for antibacterial activity against Escherichia coli (E coli) and methicillin-resistant Staphylococcus pseudintermedius (MRSP), in vitro, and to establish the effect of incorporating AgNP into carriers for sustained release on this antibacterial activity. SAMPLES: Silver nanoparticle dispersion (0.02 mg/mL) composed of citrate-stabilized, spherical, 10 nm diameter nanoparticles in aqueous buffer. PROCEDURES: E coli and MRSP were treated with 0.01 mg/mL AgNP. The highest concentration of bacteria where growth was inhibited by AgNP was selected for treatment with 0.01 mg/mL AgNP incorporated 3 carriers for sustained release: calcium sulfate hemihydrate (CSH) beads, poloxamer 407 gel, and gelatin sponge, respectively. The antibacterial activity of AgNP and AgNP incorporated into carriers for sustained release was compared with a mixed linear effects model. RESULTS: AgNP inhibited bacterial growth at a concentration of 101 for MRSP and 103 for E coli. For MRSP, the treatment group was associated with bacterial growth (P < .001) while the concentration of bacteria and time were not (P = .292 and P = .289, respectively). For E coli, the treatment group and concentration of bacteria were associated with bacterial growth (P < .001 and = .029, respectively) while time was not (P = .095). Poloxamer 407 gel exerted standalone antibacterial activity against both species of bacteria; sponge and CSH beads did not. CLINICAL RELEVANCE: AgNP has antibacterial activity against E coli and MRSP, which can be reduced when incorporated into carriers for sustained release. Poloxamer 407 gel alone and combined with AgNP exerts antibacterial activity against E coli and MRSP.

Evaluation of RapidChek® SELECT™ for the detection of Salmonella spp. in environmental samples from a veterinary hospital.

Nosocomial salmonellosis in hospitalized animals is a recognized hazard, especially in large animal clinics. A standardized culture protocol (SCP) for detecting Salmonella spp. in environmental samples using a 48-h enrichment step results in a 5-day turnaround time for negative results. The RapidChek® SELECT™ Salmonella (RCSS) test system offers detection of organisms in 22-44 h through double enrichment followed by a lateral flow immunoassay. Negative results are reported within 48 h. To determine the most sensitive and rapid method for detecting Salmonella spp. from environmental samples collected at the large animal Purdue Veterinary Hospital (LA-PVH), a preliminary study compared the performance of RCSS and a SCP when testing artificially spiked and naturally contaminated samples. An expanded study analyzed results obtained using the RCSS method to test 872 environmental samples over a 12-month period. Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry was chosen as the confirmation method for RCSS-presumptive positive samples. A randomly selected subset of samples received additional confirmation by real-time PCR. Here, we reported the performance data of RCSS in terms of sensitivity, specificity, and positive predictive value using MALDI-TOF results as reference for comparison. We also provide guidelines for reporting results obtained using this system.