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A subset of Category B agents comprise pathogens that are food or waterborne. These pathogens include but are not limited to: Salmonella species Shigella dysenteriae Escherichia coli 0157:H7 Vibrio chloerae Cryptosporidium parvum

A category A infectious substance is in a form that is capable of causing permanent disability or life-threatening or fatal disease in otherwise healthy humans or animals when exposure to it occurs. Exposure would occur if the substance were released from its protective packaging and a human or animal came into contact with it. Some examples of category A infectious substances include: Bacillus anthracis (cultures only) Brucella abortus (cultures only) Brucella melitensis (cultures only) Burkholderia mallei (cultures only) Clostridium botulinum (cultures only) Creutzfeldt-Jakob disease (CJD) brain tissue specimens Dengue virus (cultures only) Escherichia coli, verotoxigenic (cultures only) Ebola virus Francisella tularensis (cultures only) Hantaviruses causing hemorrhagic fever with renal syndrome Herpes B virus (cultures only) Human immunodeficiency virus (cultures only) Lassa virus Mycobacterium tuberculosis (cultures only) Poliovirus (cultures only) Rabies and other lyssaviruses (culture only) Shigella dysenteriae type I (cultures only) West Nile virus (cultures only) Yersinia pestis (cultures only)New and emerging pathogens should also be classified as category A until or unless additional information is received to move them to category B. For example, in 2009, shipments of Influenza A 2009 H1N1 subtype specimens were initially placed into category A until sufficient information allowed them to be moved to category B. This is not an exhaustive list. Sometimes, deciding on the classification of an infectious substance requires professional judgement and involves knowing the medical history or symptoms of the source patient or animal and/or knowing the local epidemiological conditions at the time the patient specimen or culture was obtained. If there is doubt as to whether or not a substance meets the criteria of category A, it must be treated as a category A substance for shipping.

According to regulatory requirements, Gram stain quality control (QC) testing must be performed with each new batch of stain and at least weekly, using both gram-positive and gram-negative organisms. However, individual laboratories may have more stringent requirements. No matter what the required frequency for QC testing, if you prepare and read Gram stains infrequently it would be helpful to stain quality control slides at the same time as a patient Gram stain smear. The image on the right represents control slides using Staphylococcus aureus as the gram-positive control and Escherichia coli as the gram-negative control. If properly stained, the Staphylococcus aureus on the positive control slide (side A in the image) will stain blue, or gram-positive. The Escherichia coli on the negative control slide (side B in the image) will stain red, or gram-negative. If these slides are not stained properly, the problem must be resolved and new slides made before patient specimens are examined and reported.

Quality control smears are stained at the same time as the patient's slides.They must be examined before you examine the patient's slides.If properly stained, the Staphylococcus aureus on the positive control slide will stain blue, or gram positive.The Escherichia coli on the negative control slide will stain red, or gram negative.If these slides are not stained properly, the problem must be resolved and new slides made before the patient specimen is examined.

The microscopic appearance of control slides must also be checked. The Gram positive control, Staphylococcus aureus, should stain blue, and the Gram negative control, Escherichia coli, should stain pink.