Development of a consensus method for culture of Clostridium difficile from meat and its use in a survey of U.S. retail meats.

Three previously described methods for culture of Clostridium difficile from meats were evaluated by microbiologists with experience in C. difficile culture and identification. A consensus protocol using BHI broth enrichment followed by ethanol shock and plating to selective and non-selective media was selected for use, and all participating laboratories received hands-on training in the use of this method prior to study initiation. Retail meat products (N = 1755) were cultured for C. difficile over 12 months during 2010-2011 at 9 U.S. FoodNet sites. No C. difficile was recovered, although other clostridia were isolated.

A comparison of different processing methods for picked blue crab (Callinectes sapidus).

Five methods for producing picked crab meat from cooked blue crab (Callinectes sapidus) were evaluated for internal food temperatures and bacterial numbers at various process points. Whole shell-on crabs, crab cores ("backed" crabs with carapace removed), and crab meat samples were analyzed for standard plate count, total coliforms, fecal coliforms, Escherichia coli, and Staphylococcus aureus. For three of the processes, crabs were backed and washed a substantial time before picking; one of the processes used an ice slush dip to cool cooked crabs. Except for a single crab sample, bacteria were not isolated from crab and core samples. Standard plate count, E. coli, and S. aureus in crab meat samples from the different processes were statistically the same. Bacterial numbers in fresh picked crab meat samples exposed to an ambient temperature of 20 to 21.1 degrees C for 1.5 and 3.5 h and stored at 1 degrees C for 3 to 4 days and 7 to 8 days did not significantly differ (P < 0.05).

Isolation and characterization of Escherichia coli recovered from Maryland apple cider and the cider production environment.

Contaminated apple cider has been implicated in several Escherichia coli O157:H7 outbreaks. In an attempt to investigate sources and modes of entry of E. coli into apple cider, samples of fresh apple, pomace, and cider and equipment and mill floor swabs were analyzed for standard plate counts (SPC), total coliforms (TC), fecal coliforms (FC), and E. coli. E. coli was isolated from 14 (33%) of 42 samples of bottled fresh cider, from food equipment in 6 (67%) of 9 mills, and from apples, pomace, or cider in 7 (78%) of 9 mills. Seventy-five E. coli isolates were further characterized for Shiga toxin-producing E. coli (STEC)-associated virulence factors, antimicrobial susceptibility, and pulsed-field gel electrophoresis (PFGE) type. No E. coli O157:H7 or other STEC was identified. Serotyping and PFGE revealed 64 distinct profiles, suggesting that recovered E. coli arose from multiple independent sources. However, on one occasion, E. coli isolated from the source apple sample was closely related to the E. coli identified in the finished cider sample. E. coli isolates were further tested for antimicrobial susceptibility to 17 antimicrobial agents of human and veterinary importance. Fourteen (19%) of the 75 isolates were resistant to at least one of the antimicrobial agents tested, and 9 (12%) were resistant to at least two of these agents. Of the resistant isolates recovered, 64% were resistant to tetracycline and 57% were resistant to streptomycin. Overall, the level of E. coli contamination in source apple samples did not differ significantly from those in samples of pomace, cider at the press, and cider entering the bottling tank; therefore, source apples cannot be dismissed as a potential contributor of E. coli to the cider-making process.