Spectrum Information and Courses from MediaLab, Inc.

Illustrated is the picture of the surface of a disk diffusion test including a ceftazidime disk (left) and a combintation ceftazidime/clavulanic acid disk (right).Observe in the photograph that the zone of inhibition around the the combination ceftazidime/clavulanic acid disk (right) is at least 5 mm larger than around the clavulanic acid disk (left).This observation that the presence of clavulanic acid, a beta-lactamase inhibitor, has resulted in such a large increase in the zone of inhibition indicates that an extended spectrum beta lactamase (ESBL)is being produced.When an organism is producing an ESBL, the susceptibility to individual cephalosporins cannot be predicted, thus requiring that each drug must be tested individually.It may be important to detect ESBL-producing stains of K. pneumoniae and E. coli as treatment failure may occur if the wrong cephalosporin is selected.

Ladhani S. Joannou CL. Lochrie DP. Evans RW. Poston SM.: Clinical, microbial, and biochemical aspects of the exfoliative toxins causing staphylococcal scalded-skin syndrome. Clinical Microbiology Reviews. 12:224-242, 1999The exfoliative (epidermolytic) toxins of Staphylococcus aureus are the causative agents of the staphylococcal scalded-skin syndrome (SSSS), a blistering skin disorder that predominantly affects children. Clinical features of SSSS vary along a spectrum, ranging from a few localized blisters to generalized exfoliation covering almost the entire body.The toxins act specifically at the zona granulosa of the epidermis to produce the characteristic exfoliation, although the mechanism by which this is achieved is still poorly understood.Despite the availability of antibiotics, SSSS carries a significant mortality rate, particularly among neonates with secondary complications of epidermal loss and among adults with underlying diseases.

A lack of Vitamin K can cause a loss of functionality in Vitamin K dependant coagulation factors, specifically, factors II, VII, IX and X. Most often associated with a diet lacking in Vitamin K, it may also present in situations of broad spectrum antibiotic use, where normal flora in the gut have been eliminated. As one might expect, treatment involves a diet rich in Vitamin K containing foods, and judicious use of broad spectrum antibiotics.

Chemiluminescent assays use antibodies that are conjugated to enzymes, such as peroxidase or alkaline phosphatase. These enzymes, mixed with chemiluminescent substrates, produce light in the visible spectrum. A direct relationship exists between the amount of drug that is present in the sample and the light units that are produced and measured by the luminometer in the instrument. Assays that use chemiluminescence are more sensitive than immunoassays that rely on the generation of a colored product.