[Blood cultures. Comparative study with 7 known and 2 new nutrient media for the detection of aerobic and anaerobic microorganisms (author's transl)]

Abstract

The growth promoting properties of seven commercially manufactured and two recently developed culture media are compared according to a standardized method. The study is carried out alternately without and with the addition of 10% fresh human blood to the culture media. The carefully selected test strains include 20 species of bacteria and 2 species of yeasts which represent obligatory aerobic, facultative anaerobic and obligatory anaerobic microorganisms with quite different nutritional and atmospherical requirements. The 9 tested media are good enough for the purpose of culturing nonfastidious bacteria. However, most of the commercially prepared media failed to detect small inocula of very fastidious microbial agents, especially when no blood is added. Collectively, thiol broth is the most noneffective medium. The last but one is thioglycollate medium. Three culture media based on brain heart infusion formula prove to be effective. Those are the commercial brain heart dextrose and the two media recently developed by the authors, namely brain heart dipeptone (BHD) and brain heart dipeptone cysteine (BHDC). BHD is the most suitable medium for the detection of obligatory aerobic and facultative anaerobic fastidious microorganisms. BHDC detects anaerobic fastidious bacteria quite effectively. The other media, namely Columbia, trypticase soy, trypticase soy sucrose, and Rosenow are of limited value with regard to the detection of small inocula of fastidious microorganisms. The causes of the unsatisfactory results with different commercial media are discussed in detail. The authors point out to the possible use of hypertonic media in special cases. Properties that should be fulfilled by blood culture media are proposed.