Comparison of tryptic soy broth with tryptic soy broth supplemented with sucrose in the septi-chek blood culture system

Evaluation of Escherichia coli O157:H7 growth media for use in test-and-hold procedures for ground beef processing

Since the mid-1990s, the beef industry has used a process called test and hold, wherein beef trim and ground beef are tested to keep products contaminated with Escherichia coli O157:H7 out of commerce. Current O157:H7 detection methods rely on a threshold level of bacterial growth for detection, which is dependent on the growth medium used. Twelve media were examined for growth and doubling time: buffered peptone water (BPW), SOC (which contains tryptone, yeast extract, KCl, MgCl2, and glucose), buffered peptone water plus SOC (BPW-SOC), Bacto-NZYM, RapidChek E. coli O157:H7 medium, BioControl EHEC8 culture medium, Neogen Reveal for E. coli O157:H7--Eight Hour medium (Neogen Reveal 8), BAX System medium for E. coli O157:H7 (BAX) BAX System medium for E. coli O157:H7 MP (BAX-MP), modified E. coli broth, nutrient medium, and tryptic soy broth (TSB). All media were tested at 37 or 42 degrees C under static or shaking conditions. The eight media with the highest total CFU per milliliter and most rapid doubling times were BPW-SOC, NZYM, RapidChek, EHEC8, Neogen Reveal 8, BAX, BAX-MP, and TSB. The ability of these eight media to enrich E. coli O157:H7 in ground beef was further evaluated through time-course experiments using immunomagnetic separation. Of these media, TSB was the easiest to prepare, had a wide application base, and was the least expensive. In the test-and-hold process, the normal ratio of medium to product is 1:10. In this study, a 1:3 ratio worked as well as a 1:10 ratio. Processors using test-and-hold procedures could use 1 liter of TSB to enrich for E. coli O157:H7 in a 375-g sample instead of the usual 3.375 liters, thus saving reagents, time, and labor while maintaining accuracy.

Comparative evaluation of radiometric tryptic soy broth versus radiometric tryptic soy broth with 10% sucrose for detection of bacteremia and fungemia in pediatric patients

We compared BACTEC radiometric blood culture media with (8B) and without (6B) 10% sucrose for the detection of bacteremia and fungemia in pediatric patients at four university teaching hospitals that used identical methods for obtaining and processing specimens. Overall, the yields of microorganisms from 5,714 blood culture sets were no different in the two media, although a trend was noted favoring 6B for the detection of pneumococci. Speed of detection of positive results was faster in the 6B than in the 8B medium (P less than 0.05), largely due to the faster detection of Staphylococcus aureus in the 6B medium. We conclude that, overall, with pediatric patients the hypertonic 8B radiometric medium has no advantage and that it possibly has a modest disadvantage, compared with isotonic 6B radiometric medium.

Blood-culture techniques. A survey in Australasian laboratories

The blood-culture methods of participants in the Microbiology Quality Assurance Programme were surveyed in late 1983; 183 participants from Australasia and S.E. Asia completed a questionnaire, the results of which are discussed. The choice of skin disinfectants varied widely. Conventional broth media were used by 85 participants; one or more diphasic bottles by 56; Roche Septi-Chek was used by 25; and BACTEC by 17. Only 80% of respondents reported the use of sodium polyanethol sulfonate. Contamination rates ranged from 0 to greater than 10%. Cultures were kept for as little as five days or as long as three weeks and were examined by inspection and/or Gram stain and/or subculture at widely varying intervals. While a great diversity of methods was used, in most cases these were adequate. The workload involved in some of the more laborious routines was considerable. It would be desirable to evaluate the cost-effectiveness of many blood culture practices.