Evaluation of two commercial immunoassays used to screen patients for systemic lupus erythematosus.

Diagnosing systemic lupus erythematosus (SLE) can be challenging as laboratory screening methods, although sensitive, lack specificity. The poor specificity of autoimmune testing produces more false positive results than true positive results. False positive results can cause stress to patients without autoimmune disease and require unnecessary rheumatology consultation to rule out disease. Our objective was to evaluate two screening assays to reduce the number of false positives while maintaining high sensitivity. In this study, we evaluated two immunoassays, the AtheNA Multi-Lyte II ANA System and QUANTA Lite ANA ELISA, to screen patients for SLE. All positive screening results were compared to immunoflourescent ANA testing using theHEp-2000 ANA System. A chart review was performed on all patients tested to determine clinical diagnosis of SLE. The QuantaLite ANA ELISA produced significantly more false positive results than the AtheNA Multi-Lyte II Test System when screening for SLE in our patient population.

Recovery of a catalase-negative Staphylococcus epidermidis strain in blood and urine cultures from a patient with pyelonephritis.

This report describes a 60-year-old patient with bilateral nephrolithiasis. A catalase-negative Staphylococcus epidermidis strain was recovered from both urine and blood cultures. Although rare, isolates of catalase-negative Staphylococcus spp., including Staphylococcus aureus, have been reported. Here, we describe the first report of a catalase-negative S. epidermidis strain.

Rates of carriage of methicillin-resistant and methicillin-susceptible Staphylococcus aureus in an outpatient population.

OBJECTIVES: To assess the prevalence of and the clinical features associated with asymptomatic Staphylococcus aureus colonization in a healthy outpatient population, and to compare the characteristics of colonizing methicillin-resistant S. aureus (MRSA) strains with those of strains causing infection in our community and hospital. SETTING: Outpatient military clinics. METHODS: Specimens were obtained from the nares, pharynx, and axillae of 404 outpatients, and a questionnaire was administered to obtain demographic and risk factor information. MRSA strains were typed by pulsed-field gel electrophoresis (PFGE) and evaluated for antibiotic susceptibility. Antibiograms of study MRSA strains were compared with those of MRSA strains causing clinical illness during the same time period. RESULTS: Methicillin-susceptible S. aureus (MSSA) colonization was present in 153 (38%) of the 404 asymptomatic outpatients, and MRSA colonization was present in 8 (2%). Detection of colonization was highest from the nares. No clinical risk factor was significantly associated with MRSA colonization; however, a tendency was noted for MRSA to be more common in men and in those who were older or who had been recently hospitalized. All colonizing MRSA strains had unique patterns on PFGE. In contrast to strains responsible for hospital infections, most colonizing isolates of MRSA were susceptible to oral antibiotics. CONCLUSIONS: MRSA and MSSA colonization is common in our outpatient population. Colonization is best detected by nares cultures and most carriers of MRSA are without apparent predisposing risk factors for acquisition. Colonizing isolates of MRSA are heterogeneous and, unlike nosocomial isolates, often retain susceptibility to other non-beta-lactam antibiotics.