Controlled evaluation of hypertonic sucrose medium at a 1:5 ratio of blood to broth for detection of bacteremia and fungemia in supplemented peptone broth

Controlled comparison of a new Becton Dickinson agar slant blood culture system with Roche Septi-Chek for the detection of bacteremia and fungemia

Two commercially available agar slide blood culture systems, Septi-Chek (Roche Diagnostics, Div. Hoffmann-La Roche Inc., Nutley, N.J.) and VACUTAINER agar slant (Becton Dickinson [BD] Vacutainer Systems, Rutherford, N.J.), were compared in 5,628 paired blood cultures from adult patients. The systems were inoculated with equal volumes (5 ml) of blood. There was no statistically significant difference between the two systems in the overall recovery of clinically important microorganisms; however, significantly more Escherichia coli (P less than 0.05) organisms were detected in the Septi-Chek system. Concurrently, significantly more contaminants (P less than 0.001) also were present in Septi-Chek bottles. When microorganisms grew in both systems, there was no significant difference in the time to recovery of important organisms, except that anaerobes were detected more quickly in the BD system. This study suggests that the BD VACUTAINER agar slant is an acceptable alternative to the Septi-Chek system for routine blood cultures.

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.

Controlled evaluation of the agar-slide and radiometric blood culture systems for the detection of bacteremia and fungemia

A commercially available agar-slide blood culture bottle (Septi-Chek; Roche Diagnostics, Div. Hoffman-La Roche, Inc., Nutley, N.J.) was compared with the radiometric blood culture system (BACTEC; Johnston Laboratories, Inc., Towson, Md.) in 8,544 paired blood cultures from adult patients. The systems were inoculated with equal volumes (10 ml) of blood. Overall, there was no statistically significant difference between the two systems in the recovery of clinically important microorganisms, but significantly more members of the family Enterobacteriaceae other than Escherichia coli were detected by the agar-slide system (P less than 0.005). The agar-slide system detected more fungi, and the BACTEC detected more anaerobic bacteria; however, small numbers of recovered organisms precluded statistical significance. When microorganisms grew in both systems, their presence was detected one or more days earlier in the BACTEC (P less than 0.001). More contaminants grew in the agar-slide system (P less than 0.001). Both systems performed well, and either system should provide high yield and prompt detection of positive blood cultures in patients with bacteremia and fungemia if used in an optimal way as recommended by the respective manufacturers.

Laboratory experience with radiometric detection of bacteremia with three culture media

In two long-term studies, the BACTEC radiometric system for detection of bacteremia was evaluated with three culture media each: (i) BACTEC media 6A (for aerobes) and 7B (for anaerobes) plus a thioglycolate medium and (ii) BACTEC media 6A, 7B, and 8A (hypertonic). In study 1, clinically significant isolates were identified in 1,873 (13.9%) of 13,432 blood cultures with all three media. The thioglycolate medium revealed 143 (1.1%) organisms not recovered from the 6A and 7B media. In study 2, isolates were identified in 1,135 (12.9%) of 8,759 cultures with all three media; 104 (1.2%) organisms were isolated only from the hypertonic medium. The increased yield of positive cultures in the three-medium system is likely due to the larger volume of blood cultured.