Rapid organism identification from Bactec NR blood culture media in a diagnostic microbiology laboratory.
OBJECTIVE
To evaluate rapid organism identification on positive blood culture Bactec NR media (phial types 26, 27, 42 and 17), and to assess the usefulness of these procedures in a diagnostic microbiology laboratory.
METHODS
Two hundred and sixty, first positive, blood culture bottles from individual patients were tested by rapid identification methods selected on the basis of Gram film organism morphology. Tube coagulase and latex agglutination were applied to presumptive staphylococci; latex agglutination antigen detection methods to suspected pneumococci, Neisseria and Haemophilus sp; and latex agglutination grouping tests for cultures thought to be non-pneumococcal streptococci.
RESULTS
Media type did not influence test performance (p>> 0.05 for all comparisons). Misapplication of methods occurred on eight occasions and there were 14 false positive results, nine involving the latex reagents for group C streptococci and pneumococci. The positive predictive values for tube coagulase tests and latex reactions for H influenzae type b, and N meningitidis groups B and C were 100%. The pneumococcal and staphylococcal latex tests gave positive predictive values of 94.1% and 62.5%, respectively, and the corresponding figure for streptococcal grouping reactions was 75.9%. With the exception of staphylococcal latex testing (80%) all investigation negative predictive values were>> 90%.
CONCLUSIONS
The performance of the staphylococcal latex agglutination method was unsatisfactory and it is not appropriate for use with the media studied. In view of the cross-reactions observed with the tests used to identify group C streptococci and pneumococci, positive findings must be interpreted with caution. In all other regards the protocol evaluated produced rapid, reliable, clinically useful information and, subject to local experience, is recommended to users of Bactec NR media.
Quality control of culture media in a microbiology laboratory.
The nature of reporting of a microbiology laboratory depends upon the quality of the culture media used. Quality of media directly affects the observations and inferences drawn from the cultural characteristics of microorganisms. Checking of different parameters of media such as growth supporting characteristics, physical characteristics, gel strength and batch contamination can help to assess their quality. There are different methods to check all these parameters systematically. The meticulous performance of quality control of culture media can assure precision in reporting.
Comparison between microbiomes collected from different bacterial and fungal selective culture media used for silage microbiology
- Plate counts using selective culture media is still the most frequently used method for the enumeration of the different microbial groups that colonize silage, including lactic acid bacteria, yeasts and molds. Since different culture media have specific composition, they may allow the growth of specific populations. To date, no study has used next generation sequencing technology to compare the selective capacity of these different culture media although this approach could provide comprehensive insight into the relevance of using one culture medium over another. Sequencing of the 16S rDNA and ITS amplicon were performed to compare the selectivity of different culture media used in silage microbiology.
- Corn silage, grass-alfalfa silage and total mixed ration extracts were plated on five selective media for lactic acid bacteria, incubated under aerobic and anaerobic conditions, and on eight selective media for yeast and molds to compare their selectivity. Ensiling provided a pre-selection environment for specific microorganisms over forage and reduced the number of observed OTUs: only 12 OTUs of bacteria were observed in corn silage sampled in the center of a bunker silo, while the mean number of OTUs identified in samples taken closer to the side of the silo, influenced by higher oxygen and humidity level, increased to 79. Still, MRS and Rogosa plates had less than 12 different OTUs in the center and 24 at the side, mainly Lactobacillaceae, Acetobacteraceae, and Leuconostocaceae.
- Incubating the plates under anaerobic conditions was selective against Acetobacteraceae. MRS supplemented with acetic acid increased selectivity of lactic acid bacteria. When plated on culture media specific for yeast and molds, from 17 to 68 different OTUs were observed in corn silage. Mixed grass-alfalfa silage and total mixed ration samples usually had more observed OTUs and the diversity profile of the corresponding culture media was similar to that of the original samples. For yeasts and molds, Dichloran Rose Bengal Chloramphenicol Agar revealed a diversity profile close to the that of the corn silage.
Bacterial culture through selective and non-selective conditions: the evolution of culture media in clinical microbiology.
- Microbiology has been largely developed thanks to the discovery and optimization of culture media. The first liquid artificial culture medium was created by Louis Pasteur in 1860. Previously, bacterial growth on daily materials such as some foods had been observed. These observations highlighted the importance of the bacteria’s natural environment and their nutritional needs in the development of culture media for their isolation. A culture medium is essentially composed of basic elements (water, nutrients), to which must be added different growth factors that will be specific to each bacterium and necessary for their growth. The evolution of bacterial culture through the media used for their culture began with the development of the first solid culture medium by Koch, allowing not only the production of bacterial colonies, but also the possibility of purifying a bacterial clone.
- The main gelling agent used in solid culture media is agar. However, some limits have been observed in the use of agar because of some extremely oxygen-sensitive bacteria that do not grow on agar media, and other alternatives were proposed and tested.
- Then, the discovery of antimicrobial agents and their specific targets prompted the emergence of selective media. These inhibiting agents make it possible to eliminate undesirable bacteria from the microbiota and select the bacteria desired. Thanks to a better knowledge of the bacterial environment, it will be possible to develop new culture media and new culture conditions, better adapted to certain fastidious bacteria that are difficult to isolate.
Agar, low gel strength, suitable for microbiology |
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| GC6234-100G | Glentham Life Sciences | 100 g | 64.8 EUR |
Agar, low gel strength, suitable for microbiology |
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| GC6234-1KG | Glentham Life Sciences | 1 kg | 184.8 EUR |
Agar, low gel strength, suitable for microbiology |
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| GC6234-250G | Glentham Life Sciences | 250 g | 84 EUR |
Agar, low gel strength, suitable for microbiology |
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| GC6234-500G | Glentham Life Sciences | 500 g | 118.8 EUR |
Agar, low gel strength, suitable for microbiology |
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| GC6234-1 | Glentham Life Sciences | 1 | 122.6 EUR |
Agar, low gel strength, suitable for microbiology |
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| GC6234-100 | Glentham Life Sciences | 100 | 23.8 EUR |
Agar, low gel strength, suitable for microbiology |
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| GC6234-250 | Glentham Life Sciences | 250 | 39.4 EUR |
Agar, low gel strength, suitable for microbiology |
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| GC6234-500 | Glentham Life Sciences | 500 | 68.9 EUR |
DiscoveryProbe? Microbiology & Virology-related Compounds Panel |
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| L1014-5 | ApexBio | 5 mg/well | 6267.6 EUR |
CMRL 1066, CIT CULTURE MEDIA |
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| 98-304-CV | CORNING | 500 mL/pk | 78 EUR |
Mouse ES Cell Culture Media |
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| M16101 | Neuromics | 500 mL | 1336.8 EUR |
ExoFACS? Kit for Cell Culture Media Exosomes |
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| K1236-20 | Biovision | each | 973.2 EUR |
Exosome Isolation kit (for cell culture media) |
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| P100 | 101Bio | - | Ask for price |
Exosome Isolation kit (for cell culture media) |
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| P100L | 101Bio | - | Ask for price |
Exosome Isolation kit (for cell culture media) |
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| P100S | 101Bio | - | Ask for price |
Exosome Isolation kit (for stem cell culture media) |
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| P107S | 101Bio | - | Ask for price |
Exosome Isolation kit (for stem cell culture media) |
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| P107 | 101Bio | - | Ask for price |
VEX Exosome Isolation Reagent (from cell culture media) |
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| R601 | Vazyme | 50 ml | 706.8 EUR |
Reagent for Total Exosome Isolation (Culture Media Supplement) |
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| EIR-02 | Creative Biolabs | 50 ml | 2485.2 EUR |
Exo-Flow 2.0 CD9 Analysis Kit (for Tissue Culture Media) |
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| EXOFLOW2-205A-TC | SBI | 10 rxn | 705.6 EUR |
Exo-Flow 2.0 CD63 Analysis Kit (for Tissue Culture Media) |
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| EXOFLOW2-200A-TC | SBI | 10 rxn | 705.6 EUR |
Exo-Flow 2.0 CD81 Analysis Kit (for Tissue Culture Media) |
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| EXOFLOW2-210A-TC | SBI | 10 rxn | 705.6 EUR |
Optimization of incubation duration of culture media in microbiology.
In order to perform biological analysis, clinical laboratories apply the instructions of reagent suppliers. For culture media these instructions are often incomplete and poorly adapted to the variety of clinical samples and micro-organisms. The REMIC can help to overcome these shortcomings. Required time of incubation for culture media are proposed based on the nature of the sample and the type of micro-organism suspected. Nevertheless, they are most often expressed in multiple of 24 hours and they are often considered as minimal by the laboratories.
As the samples are inoculated “continuously”, while the readings are most often done at a single definite time of the day, we propose a strategy to optimize incubation duration of cultures medium. A time of incubation in the day so-called “limit” is defined. From this, the incubations are stopped or prolonged according to the results of the culture and the direct examination. As the instructions of suppliers of culture media are not adapted, it appears necessary that these suppliers relies on the repositories of professional societies as this is the case for agars medias used for antibiotic susceptibility testing.