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  1. Laboratory Methods (Food)

About the Bacteriological Analytical Manual (BAM)

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Microbiological Detection Methods

Methods development has always been driven by the demand for tests that are faster, cheaper, easier, and more accurate. Pressure for improved procedures is particularly apparent in microbial food safety, because traditional tests may involve many steps — resuscitation of stressed microbial cells, enrichment of the few cells that may be present in a sample, selection that leads to the isolation of pure cultures, followed by identification, which could require a combination of morphological, biochemical, immunological and genetic techniques and, possibly, tests for virulence or toxicity using animal inoculation. Often, such test protocols take longer than the shelf life of the food being analyzed. Ways proposed to accelerate the procedure included, initially, improved media and compacted culturing. Then, automation began to replace manual execution. Also, indirect identification, i.e., by biochemical (e.g., fatty acid profiles, nucleic acid sequences) or biophysical shortcuts (FT-IR) that reveal organisms' pertinent biomarkers or genetic fingerprints, began to make the isolation of viable microbes not as necessary. These newer tests — known as "rapid methods" if they took hours rather than days and as "real-time" testing if they took minutes — have not yet, however, made traditional testing obsolete.

There are good reasons why analysts should continue to have the traditional skills to resuscitate, enrich, isolate, and identify microorganisms. Often, some culturing is necessary before there is enough material for the application of a rapid method or real-time test. Then, too, foods may contain substances that interfere with biochemical/molecular test shortcuts. Furthermore, having a viable microbial isolate may still provide quantitative and infectivity information not otherwise available, or be mandatory because of regulatory requirements and legal issues, or be useful later for retrospective investigations such as the characterization of new biomarkers. And, since no two types of test have the same sensitivity, the old ones serve as convenient standards for false positive and false negative rates. Kit versions of rapid methods are interpreted differently depending on whether the results are positive or negative: negative results are considered definitive but positive results require confirmation by another test.

The Bacteriological Analytical Manual

FDA's Bacteriological Analytical Manual (The BAM) is a collection of procedures preferred by analysts in U.S. Food and Drug Administration laboratories for the detection in food and cosmetic products of pathogens (bacterial, viral, parasitic, plus yeast and mold) and of microbial toxins. The manual's contents reflect the history of methods development described above. Except for some rapid methods listed in Appendix 1 (now obsolete and withdrawn from the BAM), all these methods have been used and peer reviewed by FDA scientists as well as by scientists outside FDA. However, not all of these methods have been fully validated by collaborative studies. In some instances, collaborative studies are not possible because uniform test samples can not be prepared (as with encysted parasites). In other instances, FDA needs to use a method before the time it takes to achieve full validation.

At first (1965, Edition 1), the BAM was intended to be only a vehicle for information and standardization within FDA. However, the manual's reputation as useful spread beyond the agency. Requests for copies proliferated and it was decided to make the BAM generally available. It has gone through 8 major editions, with, on occasion, revisions in between. Since 1976 (Edition 4), BAM has been published and distributed by AOAC International. In 1998, Edition 8, Revision A was issued not just as hard copy, but also in an electronic format (a CD-ROM version) by AOAC. In 2000 the BAM was made available on the FDA/CFSAN web site and was designated the BAM online. At that time continuous updating became possible, and numbered editions of the BAM were discontinued. In 2009 the BAM content was moved to the current FDA web site. Each section bears the dates on which it was last reviewed and revised, and includes contact information for users.

Updates and Revisions since publication of the BAM

Edition 8 Revision A, 1998

Introduction Revision Date(s)
[mmm yy]
Introduction Mar 00, Jun 12
1. Food Sampling Apr 03
2. Microscopic Examination Nov 00
4. Enumeration of Escherichia coli and the Coliform Bacteria Sep 02, Feb 13, Jul 17
4A. Diarrheagenic Escherichia coli Sep 02, Sep 09, Dec 12, Jul 13, Jul 14, Aug 16, Oct 18
5. Salmonella Apr 03, Sep 05, Dec 05, Jun 06, Dec 07, Feb 11, Nov 11, Aug 12, Feb 14, May 14, Dec 15, Aug 16, Feb 20
6. Shigella Oct 00, Feb 13
7. Campylobacter Mar 01
8. Yersinia Aug 07, Oct 17
9. Vibrio May 04
10. Listeria monocytogenes Jan 03, Feb 13, Jan 16, Mar 17
12. Staphylococcus aureus Mar 16
13A. Staphylococcal Enterotoxins: Micro-slide Double Diffusion and ELISA-based Methods Mar 11
13B. Staphylococcal Enterotoxins Detection Methods Jun 17
14. Bacillus cereus Jan 01, Feb 12, Jul 19
19A. Detection of Cyclospora cayetanensis (Archived) Jun 17
19B. Molecular Detection of Cyclospora cayetanensis Jun 17, Oct 17
19. Yeasts, Molds and Mycotoxins Apr 00
21A. Canned Foods Nov 00
23. Microbiological Methods for Cosmetics Aug 01, May 16, Jan 17, Jul 17
24. Identification of Foodborne Bacterial Pathogens by Gene Probes (withdrawn, Oct 10) Oct 10
26B. Multi-laboratory Validation of Hepatitis A Virus Concentration and Detection Protocols - Level 3 Validation and Appendices (new chapter, Jan 2014) Jan 14
28. Detection of Enterotoxigenic Vibrio cholerae in Foods by the Polymerase Chain Reaction Mar 12
29. Cronobacter (new chapter, Mar 2012) Mar 12
1. Rapid Methods (withdrawn, Oct 10) Jan 01, Oct 10
2. Most Probable Number Feb 06, Oct 10
3. Guidelines for the Validation of Analytical Methods for the Detection of Microbial Pathogens in Foods Sep 11, Dec 19
4. Food and Feed Items that are of current Interest to the FDA for Microbiological Methods Validation Apr 12
M28a Campylobacter enrichment broth (Bolton formula) Dec 00
M29a. Abeyta-Hunt-Bark Agar Dec 00
M30d. Semisolid Medium, modified, for Biochemical Identification Mar 01
M52. Enrichment Broth, pH 7.3 ± 0.1 Sep 00
M61. Hektoen Enteric (HE) Agar Aug 10
M79. Letheen Broth (Modified) Aug 01
M103. Motility Test Medium (Semisolid) Sep 00
M152a. Trypticase Soy Agar-Magnesium sulfate-NaCl May 04
M154b. Trypticase (Tryptic) Soy Broth with 1% NaCl and 24% glycerol May 04
M156. Trypticase Soy Broth Modified Jan 02
M179. Xylose Lysine Desoxycholate (XLD) Agar Jan 02, Aug 10
M188a. Universal Preenrichment Broth (without ferric ammonium citrate) Dec 07
M189. Cellobiose-Colistin (CC) Agar May 04
M190. Vibrio vulnificus Agar May 04
M191. Vibrio parahaemolyticus sucrose Agar (VPSA) May 04
M192. Buffered Peptone Water (BPW) Sep 05
M192a. Modified Buffered Peptone water with pyruvate (mBPWp) and Acriflavin-Cefsulodin-Vancomycin (ACV) Supplement Sep 09
M193. Dey-Engley Broth Dec 05
M194. Tellurite Cefixime - Sorbitol MacConkey Agar (TC-SMAC) Sep 09, Aug 10
M195: SHIBAM Components and Instructions (New, Oct 12) Oct 12
M196 mEndo MF Medium (BD #274930) (New, Feb 13) Feb 13
M197 LES Endo Agar (BD #273620) (New, Feb 13) Feb 13
M198 mTEC Agar (BD #233410) (New, Feb 13) Feb 13
R11. Butterfield's Phosphate-Buffered Dilution Water Feb 13
R90. Peptone-Tween-salt diluent May 04
R91. Sodium desoxycholate-0.5% in sterile dH2O (String test) May 04
R92. (SDS) Sodium dodecyl sulfate-10% in sterile dH2O May 04
R93. (SSC/SDS)Sodium dodecyl sulfate May 04
R97. Peptone Diluent, 0.5%  (New, Feb 13) Feb 13

Microbiological Methods Information on Selected Websites

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