PubMed · 14002460
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B YANIS. 1963. Bacteriological tests for controlled environment.. https://pubmed.ncbi.nlm.nih.gov/14002460/
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The study presented here was performed to evaluate an accelerated protocol for the early detection of organisms producing extended-spectrum beta-lactamase (ESBL). The procedure involved testing isolates directly from positive blood-culture bottles, and a total of 40 clinical isolates (10 ESBL-producing and 10 non-ESBL-producing isolates of both Escherichia coli and Klebsiella pneumoniae) were used. The isolates were inoculated into blood cultures bottles and, upon growth signal, fluid from the bottle was cultured directly onto plates with combination discs containing cefotaxime or ceftazidime with and without clavulanate. Results were compared with those of standard methods for the detection of ESBL. High concordance between the two methods was found, and the direct test showed high sensitivity (95%) and specificity (100%). Use of this accelerated protocol may speed detection of the ESBL phenotype and thereby facilitate the early administration of appropriate antimicrobial therapy.
AIMS: To quantify the influence of the growth phase, storage temperature and nutritional quality of the plate count medium on the apparent viability of Mannheimia haemolytica during storage at different temperatures. METHODS AND RESULTS: Mannheimia haemolytica was grown in shake flasks and in aerobic continuous culture to investigate factors affecting cell viability during storage, which was determined using plate counts on different media and epifluorescence microscopy. The high specific death rates of cells harvested after cessation of exponential growth and stored at 22, 4, -18 and -75 degrees C could be related to the rapid onset of exponential death in batch cultures. Yeast extract supplementation of the culture medium increased the viability of cells at most of the above-mentioned storage temperatures. Of the total cell count in continuous culture, only 48% could be recovered on brain-heart infusion agar, whereas supplementation of the agar medium with foetal calf serum increased the plate count to 71% of the total count. CONCLUSIONS: Mannheimia haemolytica cells harvested from the exponential growth phase had the highest survival rate during storage at low temperatures. Plate count values also depended on the nutritional quality of the agar medium. SIGNIFICANCE AND IMPACT OF THE STUDY: Results presented here impact on the procedures for culture preservation and plate count enumeration of this fastidious animal pathogen.