Comparison between Flow Cytometry and Traditional Culture Methods for Efficacy Assessment of Six Disinfectant Agents against Nosocomial Bacterial Species.

The present study was undertaken to compare the use of flow cytometry (FCM) and traditional culture methods for efficacy assessment of six disinfectants used in Quebec hospitals including: two quaternary ammonium-based, two activated hydrogen peroxide-based, one phenol-based, and one sodium hypochlorite-based. Four nosocomial bacterial species, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Vancomycin-resistant Enterococci faecalis, were exposed to minimum lethal concentrations (MLCs) and sublethal concentrations (1/2 MLCs) of disinfectants under study. The results showed a strong correlation between the two techniques for the presence of dead and live cell populations, as well as, evidence of injured populations with the FCM. The only exception was observed with sodium hypochlorite at higher concentrations where fluorescence was diminished and underestimating dead cell population. The results also showed that FCM can replace traditional microbiological methods to study disinfectant efficacy on bacteria. Furthermore, FCM profiles for E. coli and E. faecalis cells exposed to sublethal concentrations exhibited distinct populations of injured cells, opening a new aspect for future research and investigation to elucidate the role of injured, cultural/noncuturable/resuscitable cell populations in infection control.

Life on the outside: role of biofilms in environmental persistence of Shiga-toxin producing Escherichia coli.

Escherichia coli is a heterogeneous species that can be part of the normal flora of humans but also include strains of medical importance. Among pathogenic members, Shiga-toxin producing E. coli (STEC) are some of the more prominent pathogenic E. coli within the public sphere. STEC disease outbreaks are typically associated with contaminated beef, contaminated drinking water, and contaminated fresh produce. These water- and food-borne pathogens usually colonize cattle asymptomatically; cows will shed STEC in their feces and the subsequent fecal contamination of the environment and processing plants is a major concern for food and public safety. This is especially important because STEC can survive for prolonged periods of time outside its host in environments such as water, produce, and farm soil. Biofilms are hypothesized to be important for survival in the environment especially on produce, in rivers, and in processing plants. Several factors involved in biofilm formation such as curli, cellulose, poly-N-acetyl glucosamine, and colanic acid are involved in plant colonization and adherence to different surfaces often found in meat processing plants. In food processing plants, contamination of beef carcasses occurs at different stages of processing and this is often caused by the formation of STEC biofilms on the surface of several pieces of equipment associated with slaughtering and processing. Biofilms protect bacteria against several challenges, including biocides used in industrial processes. STEC biofilms are less sensitive than planktonic cells to several chemical sanitizers such as quaternary ammonium compounds, peroxyacetic acid, and chlorine compounds. Increased resistance to sanitizers by STEC growing in a biofilm is likely to be a source of contamination in the processing plant. This review focuses on the role of biofilm formation by STEC as a means of persistence outside their animal host and factors associated with biofilm formation.

The Incidence of Salmonella , Campylobacter , and Yersinia enterocolitica in Swine Carcasses and the Slaughterhouse Environment.

This study was done to evaluate the degree of contamination of cooler-ready hog carcasses and the slaughterhouse environment by Salmonella spp., Campylobacter spp. and Yersinia enterocolitica . Samples from diaphragms and feces were collected from 200 market hogs in a Quebec slaughterhouse. Scalding-tank water and environmental swabs were also collected in the slaughterhouse. Specimens were tested for the presence of Salmonella spp., Y. enterocolitica , and Campylobacter spp. Salmonella spp. were isolated from 45 (10%) of 448 samples. The distribution of the isolates were slaughtering floor (8.9%), feces (80.2%), cold-room floor (4.4%), and diaphragms (6.7%). Campylobacter spp. were isolated from 247 (61.7%) of 400 specimens, and C. coli , C. jejuni , and C. laridis accounted for 97%, 2%, and 1% of isolates, respectively. Ninety-nine percent of fecal samples were positive for the presence of C. coli . Y. enterocolitica was found in 42 (9.3%) of the 448 specimens. Of these, 85.7%, 11.9%, and 2.4% of the isolates came from fecal, diaphragm, and cold-room floor samples, respectively. Neither Salmonella spp. nor Y. enterocolitica were isolated from scalding-tank water.