Staphylococcus aureus produces four types of ,-lactamase (A, B, C, and D). To (13,14,16,20,21,24,25,27

BKV load exceeding 59 copies per cell identified all cases of BKVAN. The diagnostic sensitivity, specificity, positive predictive value, and negative predictive value of quantitative PCR were 100%, 92.1%, 73.6%, and 100%, respectively. Lower levels of BKV DNA were identified in biopsies performed before viral nephropathy development. Future research will determine if earlier recognition of at-risk patients allows application of antiviral strategies to improve graft outcome.

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Boronic acids are active-site inhibitors of serine P-lactamases, and a phenylboronic acid-agarose affinity column has been used to purify j-lactamase from crude cell extracts of several bacterial species. We applied phenylboronic acid-agarose chromatography to the purffication of Staphylococcus aureus P-lactamase. Two factors interfered with the success of the previously described single-step chromatographic protocol. First, staphylococcal ,l-lactamase exhibited non-active-site-mediated adsorption to the agarose used as a support for the meta-aminophenylborate ligand, preventing the recovery of j-lactamase from the column. Second, the staphylococcal (-lactamases exhibited low affinity for meta-aminophenylborate with inhibition constants (K's) ranging from 8.0 x 10-3 to 20.0 x 10-3 M. These problems were resolved by modifying the buffers utilized during chromatography and increasing the dimensions of the affinity column, and a two-stage procedure consisting of cation-exchange chromatography followed by affinity chromatography was used to purify each of the four variants of staphylococcal ,I-lactamase. The mean specffic activities of the purified type A, B, C, and D 3-lactamases were 44.6, 12.2, 10.6, and 30.8 ,3-lactamase in pure form from a variety of bacterial species, including Bacillus cereus, Pseudomonas aeruginosa, Enterobacter cloacae, Klebsiella aerogenes, and Pseudomonas maltophilia (4). The present study investigates the applicability of the chromatographic method described by Cartwright and Waley to the purification of the four recognized variants of staphylococcal 1-lactamase. A modified protocol useful in the preparation of purified P-lactamase from S. aureus is described. MATERIALS AND METHODSOrganisms. S. aureus strains that produce each of the four variants of staphylococcal ,-lactamase were evaluated and included PC1(pl524) and RN11(pI258) (type A P-lactamase), 22260 and ST79M41 (type B P-lactamase), V137 (type C 1-lactamase), and FAR8 and FAR10 (type D P-lactamase).The sources and pedigrees of these strains have been described previously (12-14, 16, 23, 24, 26, 31

Toxoplasmosis encompasses a variety of clinical conditions. Serious sequelae are seen in congenital toxoplasmosis and in infections of the immunocompromised host. In the former, prevention of maternal acquisition of toxoplasmosis during pregnancy is paramount. Infection in the compromised host often presents with neurologic abnormalities. Unfortunately, the HIV syndrome itself or other opportunistic infections can present in a similar manner. Often, empiric treatment for toxoplasmosis is begun based on clinical findings and an enhancing lesion noted on the head CT. Pyrimethamine and sulfadiazine remain the drugs of choice for toxoplasmosis and are able to penetrate blood-brain barriers. Currently, trials using other agents are in progress.