Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

BLACT
8118
BLAC
82896
Beta-Lactamase
Clinical Information: Various bacteria produce a class of enzymes called beta-lactamases, which
may be mediated by genes on plasmids or chromosomes. Production of beta-lactamase may be
constitutive or induced by exposure to antimicrobials. Beta-lactamases hydrolyze (and thereby inactivate)
the beta-lactam rings of a variety of susceptible penicillins and cephalosporins. Beta-lactamases are
classified by their preferred antimicrobial substrate and the effect of various inhibitors (such as clavulanic
acid) on them. Some antimicrobials, such as cefazolin and cloxacillin are resistant to such hydrolysis (at
least for staphylococcal beta-lactamases). Beta-lactamase producing strains of the following are resistant
to many types of penicillin: Staphylococcus species, Hemophilus influenzae, Neisseria gonorrhoeae,
Bacteroides species, Enterococcus species, and Moraxella catarrhalis. The above organisms, when
isolated from critical specimens such as blood or spinal fluid, should always be tested for beta-lactamase
production. Addition of a beta-lactamase inhibitor to a beta-lactam (such as sulbactam plus ampicillin)
restores the activity of the antimicrobials.
Useful For: Predicting the resistance of beta-lactamase producing isolates to hydrolysis-susceptible
beta-lactam antimicrobials
Interpretation: A positive test indicates production of beta-lactamase.
Reference Values:
Negative (reported as positive or negative)
Clinical References: Livermore DM, Williams JD: Beta-lactams: mode of action and mechanisms
of bacterial resistance. In Antibiotics in Laboratory Medicine. Fourth edition. Edited by V Lorian.
Baltimore, MD, Williams & Wilkins, 1996, pp 502-578
Beta-Lactoglobulin, IgE
Clinical Information: Clinical manifestations of immediate hypersensitivity (allergic) diseases are
caused by the release of proinflammatory mediators (histamine, leukotrienes, and prostaglandins) from
immunoglobulin E (IgE)-sensitized effector cells (mast cells and basophils) when cell-bound IgE
antibodies interact with allergen. In vitro serum testing for IgE antibodies provides an indication of the
immune response to allergen(s) that may be associated with allergic disease. The allergens chosen for
testing often depend upon the age of the patient, history of allergen exposure, season of the year, and
clinical manifestations. In individuals predisposed to develop allergic disease(s), the sequence of
sensitization and clinical manifestations proceed as follows: eczema and respiratory disease (rhinitis and
bronchospasm) in infants and children less than 5 years due to food sensitivity (milk, egg, soy, and wheat
proteins) followed by respiratory disease (rhinitis and asthma) in older children and adults due to
sensitivity to inhalant allergens (dust mite, mold, and pollen inhalants).
Useful For: Testing for IgE antibodies may be useful to establish the diagnosis of an allergic disease
and to define the allergens responsible for eliciting signs and symptoms. Testing also may be useful to
identify allergens which may be responsible for allergic disease and/or anaphylactic episode, to confirm
sensitization to particular allergens prior to beginning immunotherapy, and to investigate the specificity of
allergic reactions to insect venom allergens, drugs, or chemical allergens.
Interpretation: Detection of IgE antibodies in serum (Class 1 or greater) indicates an increased
likelihood of allergic disease as opposed to other etiologies and defines the allergens that may be
responsible for eliciting signs and symptoms. The level of IgE antibodies in serum varies directly with the
concentration of IgE antibodies expressed as a class score or kU/L.
Reference Values:
Class IgE kU/L Interpretation
0 Negative
1 0.35-0.69 Equivocal
2 0.70-3.49 Positive
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