The AutoMicrobic system (Vitek Systems, Inc., Hazelwood, Mo.) is a fully automated, computerized instrument. One of the most thoroughly studied aspects of the system is its ability to identify and quantify the nine most common urinary tract pathogens. The major advantages of the AutoMicrobic system are that the results of urine cultures are available in a fraction of the time required by conventional methods and that samples can be processed with fewer man-hours. Although the specificity, sensitivity, and reliability of the system have been amply described in the literature, only one study combines these aspects with a cost analysis (D.

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The authors determined the value of performing urine microscopy on biochemically negative urine specimens in a pediatric population. Four reactions of the Chemstrip-9TM (Biodynamics, Inc., Indianapolis, IN) were used as biochemical indicators, namely, protein, occult blood, leukocyte esterase, and nitrite. Out of 1,016 urine specimens thus studied, 310 were true positive. Eleven specimens reacted biochemically in the absence of significant microscopic findings (false positive), 668 specimens were negative by the Chemstrip-9 and were either negative microscopically or had less than five white blood cells (WBCs) per high power field (HPF) and were considered true negatives. Twenty-seven specimens had negative biochemical indicators, in spite of positive microscopy; of these specimens, only seven had more than ten WBCs per HPF, 17 had five to ten WBCs per HPF, and three had five to ten red blood cells per HPF. The sensitivity of the four parameters for predicting significant microscopy of urinary sediment is 91% and the specificity is 98%. The predictive value of a negative result is 96.1%, and that of a positive result is 96.5%. The authors therefore conclude that urine microscopy is unnecessary in biochemically negative urine specimens from pediatric patients who are asymptomatic for urinary tract disease.

An increased incidence in nafcillin (semisynthetic penicillins) resistant Staphylococcus aureus (SR-SA), which peaked in January 1980, was noted in Columbus Children's Hospital (CCH), Columbus, Ohio. To investigate the source of this outbreak, we reviewed the susceptibility patterns of S. aureus strains isolated at CCH for a 12-month period (July 1979 to June 1980). A total of 773 isolates from 706 patients were investigated with a total of 40 patients colonized or infected with SR-SA, approximately 25% of which were diagnosed in the ambulatory clinics. These patients did not have any apparent previous contact with the inpatient unit or inpatient personnel. Eight nosocomial infections were also uncovered. The first appeared in December 1979. Our studies suggested that some SR-SA isolates may have originated in the community and these organisms may not be exclusive to the hospital environment, as was felt to be the case previously. We also determined that the baseline incidence for our hospital of SR-SA was approximately 2% of total S. aureus isolates. Only 35% of the SR-SA demonstrated resistance to multiple antibiotics. This report indicates that community and nosocomial 5. aureus isolates should be monitored for nafcillin resistance. Vancomycin susceptibility should be tested on all isolates and reported for SR-SA in life-threatening infections.